filter by: Publication Year
(Descending) Articles
Renewable Energy (09601481) 256
This study presents the development of a mathematical model to accurately predict the dynamics of salt and water transport in a batch electrodialysis system used for either NaCl desalination or LiCl brine concentration. The primary aim of the model is to simulate the desalination of high-salinity water under specified current density conditions. The governing equations for the electrodialysis stack and associated tanks were formulated and solved using numerical methods. Model predictions were validated against experimental data, demonstrating high accuracy: the deviation between measured and predicted tank concentrations was within ±2 % for both NaCl and LiCl systems. In addition, the study investigated how initial salt concentration, current density, and flow rate influence system performance. The results show that system efficiency is significantly affected by the initial brine concentration. Increasing the salt concentration from 5 wt% to 10 wt% and 20 wt% reduced desalination efficiencies by approximately 67 % and 93 %, respectively. Moreover, salt flux improved with higher current density, with a 71 % increase in desalination observed when current density was raised from 100 A/m2 to 400 A/m2. © 2025 Elsevier Ltd
This study explores the experimental and mathematical modeling of energy recovery from hot exhaust gases using a finned tube heat exchanger filled with paraffin. The experimental setup employs air as the heating fluid, water as the cooling fluid, and paraffin with a melting point of 68°C as the phase change material. Key parameters investigated include inlet air temperature, air mass flux during heating, and water mass during cooling. The system's thermal behavior is modeled mathematically by assuming heat accumulation in the paraffin-filled finned tubes. Numerical solutions of the equations are compared with experimental data, and dimensionless parameters are used to evaluate system performance under varying conditions. The model also examines the effects of structural features, such as fin height and the number of fins per unit tube length. The results show that increasing inlet air temperature and reducing air mass flux improve the heating and cooling efficiencies and overall system performance. Enhancing fin height from 0 to 1.5 cm and the number of fins from 0 to 20 within a 10 cm tube length leads to heating efficiency gains of 10.88% and 15%, respectively. © 2025 Wiley Periodicals LLC.
Industrial and Engineering Chemistry Research (15205045) 63(36)pp. 15646-15655
The notable reduction in forest coverage and usage of nonrenewable energy resources have resulted in accumulation of carbon dioxide in the atmosphere, thus contributing to the worsening of the phenomenon commonly referred to as global warming. This research undertook an investigation into the efficacy of a distinct absorbent in eliminating CO2 from the air within a spouted bed reactor. By utilizing the Taguchi methodology, the study examined the capacity of sodium carbonate to eradicate CO2 from the atmosphere across a wide range of concentrations (600-1850 ppm), temperatures (55-90 °C), and molar ratios of Na to C in the absorbent (ranging from 1 to 3). The results indicated that this absorbent effectively eliminated 86% of the initial CO2 at a reaction temperature of 55 °C, a molar Na/C ratio of 1.4, and an initial concentration of 1280 ppm. Additionally, the examination of the solid composition postabsorption using X-ray diffraction revealed the formation of sodium bicarbonate during the absorption process. The novelty of this study resides in the introduction of a novel method for capturing CO2 from the atmosphere. Moreover, the viability of regenerating sodium carbonate by liberating CO2 from bicarbonate was also evaluated through thermogravimetric analysis. © 2024 American Chemical Society.
Process Safety and Environmental Protection (17443598) 190pp. 1440-1449
The utilization of biogas as a renewable energy source necessitates a reduction in its CO2 content. “Ex-situ biomethanation” is employed to convert CO2 in biogas to CH4 through hydrogenotrophic methanogens. In this study, a biogas stream (32–36 % CO2) originating from cow manure digestion was subjected to treatment in a trickle bed bioreactor (4 liters). The presence of microorganisms on the packing material was confirmed by using a 16 S rRNA test and SEM images. This study stands out by considering all four combinations of thermophilic and mesophilic conditions, monitoring the transition and steady-state phases in a two-reactor series setup. The mesophilic-thermophilic mode yielded the highest purity (92 %) with an 86 % CO2 conversion rate and an energy density of 13,870 kJ/m3. Additionally, the performance consistency was also assessed using a larger TBB (8 liters). Extending the residence time, the thermophilic-thermophilic mode yielded the highest CH4 concentration at 98 %. The 16 S rRNA results revealed that, influenced by the designated growth conditions encompassing culture media, pH, temperature, and reactor retention time, an enrichment of hydrogenotrophic methanogens occurred. Furthermore, promising results in terms of CH4 concentration and process efficiency were demonstrated by the trickled bed bioreactor employing liquid-in-gas dispersion. © 2024 The Institution of Chemical Engineers
Advanced Biomedical Research (22779175) 13(1)
Background: Researchers are always searching for chemicals with antioxidant properties. The cell wall polysaccharide of Sargassum angustifolium consists of alginic acid. To use this polysaccharide and investigate on its various effects, it must first be isolated from brown algae and the operational parameters of extraction need to be optimized to reach the maximum antioxidant effect. Materials and Methods: The effects of changing the parameters (temperature, time, and power of ultrasonic waves) used in the extraction of alginic acid were discussed based on changes in the antioxidant effect. After that, M/G (β‑D‑mannuronic acid to α‑L‑guluronic acid ratio) was measured using 1H NMR spectra, and the antioxidant activity of the extracted alginic acid was examined using the DPPH method. Results: The highest antioxidant effect was observed in sample No. 4 with an extraction temperature of 65°C, extraction duration of 25 min, and 640 W of ultrasonication power, whereas the lowest antioxidant effect was observed in sample No. 7 at 45°C, 20 min, and 480 W. Conclusion: Structural changes due to increasing temperature may cause less activity, whereas the optimum temperature was 65°C. There was no direct relationship between M/G and IC50, and it should be examined along with molecular weight. Increasing the intensity of the waves increased the antioxidant activity. The extraction yield can be increased by increasing A/W (Gram of algal sample per mL of solvent). It appears that the extraction under optimum conditions enhances the MM block epimer, which may lead to an increase in the antioxidant activity. © 2024 Advanced Biomedical Research.
Clean Technologies And Environmental Policy (1618954X) 26(5)pp. 1335-1362
This study reviews the efforts made regarding thermal desalination systems, focusing on the exergetic aspect. Each plant has a component, which limits the magnitude of thermal energy improvement; however, the target should be an effort to minimize the exergy destruction. It was found that all stand-alone systems required modification or integration with other desalination plants due to their low exergy efficiency. Furthermore, the exergy-destructive components in humidification–dehumidification (HDH) systems as a domestic desalination process, in poly-generation systems by the ability of freshwater production and energy generation, and in combined cooling–heating–power (e.g., MEE-CCPP) cycles as the recent desalination technologies were introduced. The exergy efficiency of a desalination plant increased by coupling to a solid oxide fuel cell or heat pump, using surplus low-pressure or makeup steam and optimization of the effect and stage numbers. Designing a poly-generation system capable of producing power, desalinated water, as well as liquefied natural gas heating/cooling could improve the system exergetically. Desalination systems were found to benefit from increasing the evaporation temperature caused by a Rankine cycle. Coupling the HDH system to a reverse osmosis unit or thermo-compressor vapor compression–reverse osmosis plant was found to improve the system performance exergetically. Graphical abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023.
Applied Thermal Engineering (13594311) 244
Humidification-dehumidification (HD) desalination systems as small-scale desalination plants suffer from lower energy efficiency and higher costs compared to large-scale desalination systems. This review focuses on the performance of hybrid HD systems which can be coupled to a heat pump (HP), ejector, photovoltaic thermal panel, air conditioner unit, and other desalination plants to overcome these issues. The decision to select the most proper economical and energy-efficient hybrid HD system necessitates reviewing the performance of HD hybrid systems. The analysis is conducted based on desalinated water productivity, gained output ratio, exergy efficiency, and desalinated water cost. Generally, all hybridization strategies improve the performance of the HD systems. Particularly, increasing the working fluid temperature, number of solar collectors, solar radiation intensity, and effectiveness of the humidifier and dehumidifier, as well as optimization of the air and water flow rates improve the performance of the hybrid HD systems. Moreover, using a multi-stage humidifier and dehumidifier, air-heated HD-HP system, variable-pressure HD operation, multi-air extraction, proper packing, and 24-hour operation are recommended. Maximum gained output ratio of 29 and minimum desalinated water cost of US $0.54/m3 are found for the single-air extraction HD-HP system and the waste-heat driven HD unit coupled to an ejector, respectively. © 2024
Algal Research (22119264) 78
Fertilizers play a crucial role in enhancing the yield of agricultural crops and their market value. Therefore, it is essential to have large-scale, low cost, eco-friendly, broad-spectrum, and clean production of fertilizers. This study aims to prepare an iron-rich biomass, which holds the potential to serve as a biofertilizer, through the cultivation of Chlorella vulgaris microalgae under iron stress conditions. To attain this objective, three different iron sources were examined by supplementing them to the microalgal growth culture medium, namely ammonium ferric citrate, FeCl3, and EDDHA-Fe, each at varying concentrations of iron. The experimental findings revealed that, under iron stress conditions, the addition of ammonium ferric citrate as the iron source to the microalgal growth culture medium resulted in a microalgal biomass with a maximum iron content of 4.88 % by weight. However, the iron content of the obtained biomass from the culture media sourced from FeCl3 and EDDHA-Fe reached a maximum of only 2.01 % and 3.55 % by weight, respectively. Ultimately, the efficacy of the iron-rich microalgal biomass was evaluated by utilizing it during corn cultivation, in conjunction with regular microalgal biomass, ammonium ferric citrate, and the iron-deficient soil (as control) samples. The dry weight of the corn stem cultured with iron-rich biomass was 13 %, 55 %, and 152 % higher, compared to those cultured with regular microalgal biomass, ammonium ferric citrate, and the iron-deficient soil, respectively. © 2024 Elsevier B.V.
Desalination (00119164) 577
The photosynthetic chemical desalination cell (PCDC) represents a cost-effective and ecologically friendly alternative for desalinization. Nevertheless, these cells exhibit a limited desalination rate, creating challenges in terms of commercialization due to the growing internal resistance and its impact on desalination. To tackle this issue, the study explores the use of series and parallel arrangement of three CPDCs to enhance the salinity removal percentage (SR%) and flow rate, while concurrently reducing internal resistance. Findings revealed that the series configuration of cells attained a superior SR% when compared to a lone CPDC. Conversely, the parallel configuration of cells led to an increased flow rate of the desalinized stream. Equivalent cells, featuring distinct currents, were fabricated for both configurations. The research also placed emphasis on evaluating the impact of variations in internal resistance and their significance in each configuration, a crucial aspect for facilitating the scaling up of the process. From an energy consumption standpoint, the parallel configuration was identified as being more efficient. The series configuration, with a flow rate of 0.9 mL/min, exhibited the highest desalination rate (DR), whereas the parallel equivalent cell, possessing the same flow rate, demonstrated the lowest DR. Synopsis: The development of CPDC technology has the potential to result in sustainable carbon dioxide capture, the production of valuable biomass, hybrid desalination, and power generation without the presence of any reject brine. © 2024 Elsevier B.V.
Journal of the Taiwan Institute of Chemical Engineers (18761070) 148
Background: Chemical photosynthetic desalination cells (CPDCs) are among the last generations of desalination cells which use microalgae in their structure. In the cathode chambers of previous desalination cells, expensive catalysts and toxic chemicals were employed for electricity generation, similar to other bio-electrochemical systems. Many parameters affect the CPDC performance, which are still unknown. Methods: In this study, the optimization of CPDC operating parameters was investigated utilizing response surface methodology (RSM). The investigated parameters were catholyte flow rate, catholyte pH, inlet salinity concentration, saltwater flow rate, anolyte pH, anolyte concentration, and anolyte flow rate. Three different anolyte types were investigated which were an acidic anolyte (10 mM HCl), neutral anolyte (12 g/L NaCl solution) and alkaline anolyte (10 mM NaOH solution). Significant Findings: Using the optimum values for these parameters, the predicted (from RSM) and experimental salinity removal percentage values were found to be 77.76% and 75.33%, respectively. The alkaline anolyte showed higher salinity removal percentage, and power generation values (71% and 36.8 W/m2), respectively. © 2023 Taiwan Institute of Chemical Engineers
Desalination (00119164) 566
In this study, a solar multi-stage humidification-compression desalination plant with heat recovery section was experimentally studied. Since honeycomb cellulose pads are more efficient than the conventional packings, in this plant, the humidifier was filled with cellulose pads. The influence of several operating parameters on the plant performance was experimentally studied. The experiments were conducted by one-at-a-time method and the plant was optimized using the response surface methodology based on a central composite design. The results showed that increasing the temperature of the inlet water to the humidifier and the compressor pressure ratio while reducing the water-to-air mass flow ratio enhanced the gained output ratio (GOR), performance ratio (PR), and recovery ratio percentage (RR%). Besides, to improve the specific energy consumption (SEC), the temperature of the inlet water to the humidifier and water-to-air mass flow ratio should be increased while the compressor pressure ratio should be decreased. The salt concentration in the feed does not have a significant influence on the system performance. The production cost was estimated at 1.3–8.53 $·m−3 in the proposed system, which, is capable to produce demineralized water. © 2023 Elsevier B.V.
Applied Thermal Engineering (13594311) 227
A humidification-dehumidification (HDH) system using a bubble column humidifier was optimized using response surface methodology (RSM). The humidifier was integrated with four types of air distributors entitled the horizontal cuts (H-cuts) and vertical cuts (V-cuts) spargers with the same total hole area, as well as the multiple orifice nozzles (M-orifice) and perforated plate with equal hole diameters. The experimental investigation consisted of a parametric study, optimization using RSM, and bubble characteristics using image analysis. The effects of a qualitative parameter (i.e., the type of air distributors) and quantitative parameters (i.e., the inlet water temperature, superficial air velocity into the humidifier as well as the water height inside the humidifier) on the absolute humidity of the air leaving the humidifier were studied. The H-cuts and M-orifice spargers were found as the best air distributors in their subclasses due to higher gas holdup, specific interfacial area, and lower Sauter mean diameter. The humidifier performance was optimized in the lowest superficial air velocity (0.195 m/s), the highest water height inside the humidifier (50 cm) and the inlet water temperature to the humidifier (90 °C). It was concluded that the H-cuts and M-orifice spargers at the optimum values of the quantitative parameters achieved the maximum absolute humidity of about 0.18 and 0.143 kg water vapor/kg dry air, respectively. © 2023 Elsevier Ltd
International Journal of Biological Macromolecules (01418130) 226pp. 660-669
In this study, the extraction and characterization of alginic acid, the most abundant compound among brown algae were investigated. The used algae were Sargassum angustifolium from the family of brown algae native to the coasts of the Persian Gulf. The effect of temperature, time, algae mass to solvent volume ratio, and ultrasonic power on the extraction yield and ratio of monomers (M/G) was investigated using the central composite design method. Moreover, the effect of the mentioned parameters on the poly dispersity index and cytotoxic effects against breast cancer cells were also investigated. The maximum obtained extraction yield was 46 %, which was higher than those reported for algae in tropical climates. This shows the effectiveness of ultrasound in facilitating the extraction process. In addition, the minimum monomer ratio was 0.45, the minimum poly dispersity index was 2.5 and the maximum cytotoxicity for using the extract on breast cancer cell line (MCF-7) was 20.3 % (with alginic acid concentration of 250 micrograms per milliliter). © 2022 Elsevier B.V.
Journal of Energy Storage (2352152X) 54
A considerable amount of industrial heat is wasted to the atmosphere. This valuable energy could be recovered through fixed bed systems by sensible or latent heat. Mathematical modeling and experimental study of a fixed bed thermal energy recovery system by sensible heat are presented in this paper. An experimental setup was constructed in which air and water were utilized as the charging and discharging process heat transfer fluids, respectively. Three different materials including silica-ceramic, alumina-ceramic, and metal with different sizes were used as the energy storage material. Mathematical modeling was performed at three different levels to analyze the system behavior. The difference among the various modeling levels was in their simplifying assumptions. The resulting equations in each level of modeling were numerically solved. Validation of the modeling results against the experimental data was performed to evaluate the capability of the developed models in prediction of the system actual behavior. Level I model with an average error of 24 % in the charging process and 11 % in discharging process showed unsuitable results, while level II and level III models showed approximately the same and acceptable results with 5 % and 9 % average errors in charging and discharging processes, respectively. Then level II model was selected for prediction of the system performance due to its less complexity compared to level III model. Finally, the influence of the packings material, packing size, and inlet air velocity and temperature on the system performance was predicted using level II model. The system yield had the highest value for all packings at the entering air highest temperature and lowest superficial velocity examined. Metal packings showed better performance and had an experimental system yield of 54 % and 67 % at the entering air highest temperature and lowest superficial velocity, respectively. It was also observed that metal packings outperformed other packings and had the highest experimental yield of 58 % at the same operating conditions. Besides, the highest experimental yield of 61 % was achieved by packings with the smallest size (13 mm) at the highest entering air temperature (140 °C). Based on the findings of this study it can be concluded that lower inlet air velocity and higher inlet air temperature enhanced the recovery efficiency. Besides, the smaller metal packings size showed higher recovery efficiency. © 2022 Elsevier Ltd
Clean Technologies And Environmental Policy (1618954X) 23(9)pp. 2683-2696
In this study, four zero liquid discharge thermal desalination processes were technoeconomically investigated to select the most efficient and economic process for the treatment of the brine rejected from desalination units. These processes were (1) evaporation/crystallization, (2) evaporation/spray drying, (3) membrane distillation/crystallization, and (4) membrane distillation/spray drying. To harmonize the economic assessment conditions in this technoeconomic study, the feed concentration and feed flow rate of all processes were considered to be 80,000 ppm and 1500 m3/day, respectively. The results showed that the specific water production costs for Processes 1–4 were 8.1, 22.1, 8.4, and 20.7 $/m3, respectively. Therefore, the produced water from Processes 1 and 3 had the lowest specific production cost. In addition, these processes had the lowest total fixed capital investment. On the other hand, although the specific production cost and the equivalent thermal gained output ratio of Processes 1 and 3 were almost the same, Process 1 can produce demineralized water. Therefore, Process 1 was considered as the most economic option due to the high economic value of demineralized water. Graphic abstract: [Figure not available: see fulltext.]. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Process Safety and Environmental Protection (17443598) 148pp. 237-248
The objective of this study was to investigate the suitability of direct use of Chlorella vulgaris for brackish water desalination as a new conceptual technique. First, the adaptation of Chlorella vulgaris in saline water was performed, and then the living microalgae cells were utilized for the desalination process using a bubble column photobioreactor. The effect of culture medium, time, salinity and initial inoculum on the microalgae growth and salinity removal was investigated and the optimum conditions were obtained by RSM−CCD method. To assure the consumption of sodium chloride (NaCl) content of water by microalgae, the BG11 culture medium was modified by substituting its chloride and sodium containing salts by nitrate, calcium and potassium containing minerals. The results indicated that the enhancement of microalgae growth and salt removal efficiency were more pronounced in the modified-BG11 (MBG11) culture medium. Using Chlorella vulgaris microalgae in the MBG11 culture medium, the decrease in brackish water electrical conductivity for different NaCl concentrations between 1000 and 5000 ppm, was between 80 % and 40 %, respectively. Atomic absorption and flame photometry analyses confirm the hypothesis of adsorption of Na+ ions on the Chlorella vulgaris cell surface. © 2020 Institution of Chemical Engineers
European Physical Journal Plus (21905444) 136(5)
In this study, computational fluid dynamics (CFD) was used to simulate a fixed-bed distributor, investigating spherical particles in body-centered cubic (BCC) and hexagonally close-packed (HCP) structures. The bed-to-particle diameter ratio (D/dp) varied in the range of 4.158–16.65, while the range for the ratio of bed height to particle diameter (h/dp) was 5–13. The simulations were carried out for Reynolds number (Rep) in the range of 4–589, including laminar and turbulent flow regimes. To conduct validation, the numerical results were compared with our experimental data as well as seven empirical equations, where perfect match was found for both laminar and turbulent flows. Then simulations were conducted to generate the required data for an artificial neural network (ANN) to predict the velocity profile at the distributor outlet in order to save the computational CPU time. The R2, MAE and RMSE values of the neural network for predicting the fluid outlet velocity were 0.972, 0.0274 and 0.0512, respectively. The function obtained from the neural network is an efficient tool for the optimum design of fixed-bed distributors. This function could be directly used in three-dimensional fixed-bed distributor models. © 2021, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Chinese Journal of Chemical Engineering (10049541) 34pp. 61-67
The hydrodynamics and mass transfer characteristics of a lab-scale jet bubbling reactor (JBR) including the gas holdup, volumetric mass transfer coefficient and specific interfacial area were assessed experimentally investigating the influence of temperature, pH and superficial gas velocity. The reactor diameter and height were 11 and 30 cm, respectively. It was equipped with a single sparger, operating at atmospheric pressure, 20 and 40 °C, and two pH values of 3 and 6. The height of the liquid was 23 cm, while the superficial gas velocity changed within 0.010–0.040 m·s−1 range. Experiments were conducted with pure oxygen as the gas phase and saturated lime solution as the liquid phase. The liquid-side volumetric mass transfer coefficient was determined under unsteady-state oxygen absorption in a saturated lime solution. The gas holdup was calculated based on the liquid height change, while the specific interfacial area was obtained by a physical method based on the bubble size distribution (BSD) in different superficial gas velocities. The results indicated that at the same temperature but different pH, the gas holdup variation was negligible, while the liquid-side volumetric mass transfer coefficient at the pH value of 6 was higher than that at the pH = 3. At a constant pH but different temperatures, the gas holdup and the liquid-side volumetric mass transfer coefficients at 40 °C were higher than that of the same at 20 °C. A reasonable and appropriate estimation of the liquid-side volumetric mass transfer coefficient (kla) in a pilot-scale JBR was provided which can be applied to the design and scale-up of JBRs. © 2020 Elsevier B.V.
Biomass Conversion and Biorefinery (21906815) 11(6)pp. 2963-2973
Tobacco product waste (TPW) was considered as a novel and sustainable feedstock for second-generation ethanol production. TPW with over ~ 44% cellulose content was efficiently pretreated using concentrated (10% W/V) sodium hydroxide (SH) solution at different temperatures (0, 25, and 80 °C) and retention times (3 and 6 h). Subsequently, the pretreated biomass was subjected to separate enzymatic hydrolysis and fermentation by the filamentous fungus Mucor hiemalis. Promising results were achieved following 3 h pretreatment of TPW at 80 °C, whereas the hydrolysis yield was substantially increased up to 91.3%. Besides, comprehensive tacking of key features of biomass (e.g., composition, crystalline structure, surface hydrophilicity and morphology, and accessible surface area) by semi-quantitative methods together with FTIR and SEM observations revealed major improvements occurred after mild SH pretreatment. Consequently, the maximum ethanol production as high as ~ 97% of theoretical ethanol yield was obtained, while it was only 44.4% from the untreated TPW. The implication of the work could possibly support TPW utilization for large-scale ethanol production in a tobacco-based biorefinery framework. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Desalination (00119164) 515
A solar multi-stage desalination plant based on humidification compression with a heat recovery section was proposed in this study. Unlike conventional multi-stage plants, in this plant, water was reheated in the energy recovery section before entering the next humidifiers. The plant consisted of three packed columns (humidifiers), a polytropic compressor and three heat exchangers for energy recovery. A mathematical model was established to evaluate the impact of several operating parameters on the plant performance. The model was numerically solved, and a good conformity was found between the experimental data and numerical results. Average absolute error values of 2.12%, 0.25% and 0.38% were found for the outlet air humidity, outlet water temperature and outlet air temperature, respectively. In addition, the gained output ratio (GOR) and performance ratio (PR) for the proposed plant were found to be higher than those of conventional plants. In addition, higher inlet water temperature and lower pressure ratio and water-to-air mass flow ratio enhanced the GOR. On the other hand, the variation of pressure ratio had no significant influence on the PR, but higher inlet water temperature and lower water-to-air mass flow ratio increased the PR. © 2021 Elsevier B.V.
Process Safety and Environmental Protection (17443598) 148pp. 1304-1314
This study compares the freshwater productivity of a three-stage vacuum humidification-dehumidification (VHDH) desalination system to a single-stage VHDH system. Experimental study on a multi-stage humidification in sub-atmospheric pressure condition confirmed its superiority over previous multi-stage humidification-dehumidification processes. The variation of the desalination rate was measured experimentally using the three-stage vacuum humidification and heating modes. The results showed that the maximum desalination rate of the unit was 1.8 kg.h−1 per 1 m2 of solar water heater area with minimum specific power consumption (SPC) of 0.1 kW h.kg−1 when the maximum solar intensity was 1106 W.m-2 in July 2020. This investigation indicated that the system had high freshwater productivity and low SPC compared to a single-stage VHDH system. The system performance was improved when the operation was further optimized using the response surface methodology (RSM). The optimal values of saline water to air mass flow rate ratio (sw/a) and humidifier pressure (PH) of 1.77 and 33 kPa led to the maximum freshwater productivity. In all operating conditions, through converting the single-stage humidification to two-stage and three-stage humidification processes, the humidity ratio was enhanced by about 51 % and 19 %, respectively. The optimal freshwater productivity could be realized only when multi-stage vacuum humidification was utilized at isothermal heating mode in all stages and the cost was $0.002 per liter. © 2021 Institution of Chemical Engineers
Science of the Total Environment (00489697) 779
In this study, a chemical photosynthesis desalination cell (CPDC) was investigated for saltwater desalination. The cell consisted of three main parts: (1) an anodic compartment where the oxidation reaction occurs, releasing electrons, (2) a cathode compartment where the required soluble oxygen is provided by microalgae photosynthesis, and (3) an electrodialysis desalination cell installed between the cathode and anode. In the anode, a novel idea was adopted to shorten the desalination duration and increase the salinity rate using a chemical oxidation reaction in combination with the biocathode. The CPDC contributed to the carbon dioxide biological sequestration (reducing air pollution), produced microalgae biomass as a source of renewable energy and generated electricity. In the investigated CPDC, microalgae were used to supply the required oxygen solution as an electron acceptor. The metal anode-microalgae biocathode battery could provide the required energy for electrodialysis. In addition, some extra electricity was generated with a maximum excess power density of 32.4 W/m3 per volume of the net anodic compartment, 16.2 W/m3 per volume of the net cathodic compartment, and 3.07 W/m2 of membrane surface area. This study confirms the benefits of microalgae as a sustainable biocathode in microbial desalination cells (MDCs) to supply electron acceptors in an environmental-friendly manner. Compared to photosynthetic microbial desalination cells (PMDCs), the CPDC decreased the desalination time by a factor of about 4. Besides, the NaCl removal was about 69% for 12 g/L NaCl concentration in the CPDC, higher than other MDCs. In addition, as a new operational factor, the internal resistance variations were determined by electrochemical impedance spectroscopy in different case studies. The results demonstrated for the first time the possibility of applying a new desalination cell (i.e. CPDC) for water desalination and power generation which only uses a source of chemical reaction and microalgae photosynthesis without the need for an external power source. © 2021 Elsevier B.V.
Journal of Environmental Chemical Engineering (22133437) 9(2)
In this study, an air-cathode-aluminum-air desalination battery as a new technology for simultaneous desalination and electrical power generation was developed through the optimization of its operating parameters. Nitrogen-sulfur co-doped carbon was synthesized and characterized as a cheap and efficient catalyst for oxygen reduction reaction in the cathode. By optimizing the aluminum anode parameters, utilizing the fabricated air-cathode and modifying the operational conditions, the salt removal and average generated energy reached 2.06 g/L (in 90 min) and 0.55 Wh/L of the processed water, respectively, consuming 0.26 g of aluminum per hour. Moreover, using cost analysis this technology was found competitive with other desalination systems for high salinity water, consuming 2.05 Wh for 1 g salt removal with initial salinity of 12 g/L. Overall, this assembly is a low cost and environmentally friendly process, and with advantages such as continuous desalination and reasonable desalination rate, seems to be a promising candidate for desalination purposes. © 2020 Elsevier Ltd.
SN Applied Sciences (25233971) 2(4)
In the present study, Glycyrrhiza glabra residues (GGR) were used for the preparation of activated carbon, with a surface area of 959.22 m2 g−1. Activated carbon was prepared through chemical activation using ZnCl2 at optimum carbonization temperature, and impregnation ratio for nitrate, and phosphate removal. The effect of contact time and adsorbent dosage on the removal efficiency was investigated, and the pseudo-second-order kinetic model correlated well with the adsorption data. The response surface methodology was applied for the determination of the effect of initial concentration, pH, and temperature and their interaction on the removal efficiency in the batch adsorption system. The Langmuir isotherm generated a satisfactory fit with the experimental data, and the maximum adsorption capacity was 142.5 mg g−1 at 308 K and 92.5 mg g−1 at 298 K for nitrate and phosphate removal, respectively. The high adsorption capacity reveals the applicability of the GGR activated carbon for nitrate and phosphate removal. Furthermore, the fixed-bed column adsorption studies were carried out, and the effect of flow rate and influent concentration on the behavior of the breakthrough curve was studied. The breakthrough time decreased by increasing the flow rate and inlet concentration. The Thomas and Yoon–Nelson models were suitable models for the design of GGR activated carbon fixed-bed column. The LUB of 0.44 cm and 4.35 cm was obtained for nitrate and phosphate with the inlet concentration of 20 mg L−1 and a flow rate of 40 mL min−1, respectively. GGR is a new adsorbent that has not been previously utilized for adsorption of phosphate and nitrate. © 2020, Springer Nature Switzerland AG.
Progress in Energy and Combustion Science (03601285) 80
The humidification-dehumidification desalination system is known as an appealing process for small and medium scales, and high-salinity water desalination. These systems consist of humidifier and dehumidifier as the main components, energy sources for heating and electrical energy generation, accessories used for the fluid transfer or efficiency improvement, and measurement/control devices. Different system designs are reported and categorized based on enhancement in productivity, energy consumption and effective parameters such as gained output ratio, specific electrical energy consumption and production cost. According to input energy types and used components, these systems react differently, and the performance parameters change. This literature reviews past/current status and future ideas about humidification-dehumidification systems to pave the way for the researchers to improve this technology. All technologies that improve the humidification-dehumidification system performance via using efficient constitutes, renewable energy, heat recovery via multi-effect and multi-stage processes, accelerating the humidification and dehumidification processes by pressure variation or using heat pump as well as exergy and cost analyses are clarified. It is concluded that despite improving humidification-dehumidification system as a promising process for decentralized small-scale freshwater production applications, it requires further development to improve the system performance based on gained output ratio and economy. © 2020 Elsevier Ltd
Journal of CO2 Utilization (22129820) 37pp. 9-19
In this study, a modified gas feeding bubble column photo-bioreactor was utilized for microalgae cultivation and CO2 capturing. By applying response surface methodology, the optimum values of temperature, pH, light intensity, aeration rate, light-dark cycle and time were determined as 25 ° C, 8, 2700 lx, 0.5 LPM and 16-8 h, respectively. Two air spargers (with different aperture size) were used to study the effect of the bubble size on the CO2 removal and microalgae growth rate. Besides, the inlet air was humidified to avoid the evaporation from the photo-bioreactor. For the smaller bubbles and 7% CO2 concentration, the maximum values for the CO2 fixation rate, productivity and concentration of microalgae were determined to be 633.73 mg L-1d-1, 337 mg L-1d-1 and 4244 mg L-1, respectively. CO2 utilization efficiency was 35% for the smaller bubbles, showing a 15% increase over that for the larger bubbles. © 2019 Elsevier Ltd. All rights reserved.
Applied Thermal Engineering (13594311) 169
In this work, a solar-assisted pilot-scale vacuum humidification-dehumidification (VHDH) desalination plant is investigated experimentally as well as thermodynamically. In this process, the humidification performs at sub-atmospheric pressure, while the dehumidification occurs at over-atmospheric pressure. The annual experimental results show that the maximum desalination rate is obtained as 1200 mL h−1 m−2 during summer days at the best value of water to air mass flow rate ratio (w/a) and minimum humidifier pressure. It is resulted that despite achieving a high desalination rate at low pressure, the exergy efficiency decreases. This result reveals that the obtained value of humidifier pressure from energy-exergy analyses differs from the experimental one that is obtained regarding the desalination rate. © 2020 Elsevier Ltd
Bulletin Of Chemical Reaction Engineering And Catalysis (19782993) 15(2)pp. 579-590
In this study, CO2 removal efficiency from flue gas was investigated in a fluidized bed reactor under semi-dry conditions. A lab-scale fluidized bed reactor, filled with inert glass beads, was used to investi-gate the effect of operating parameters on the CO2 removal efficiency using calcium hydroxide slurry as the absorbent. The Taguchi design method was used to design the experiments. The maximum inlet concentration of CO2 was 3 vol%. The most important factors were the reaction surface area, inlet gas velocity, inlet CO2 concentration, absorbent solution flow rate, inlet gas temperature and calcium hy-droxide slurry concentration. The experimental results indicated that the CO2 removal efficiency in-creased when increasing the effective surface area of the reaction. Moreover, the removal efficiency in-creased by decreasing the input gas flow rate and inlet CO2 concentration. By performing experiments under optimum conditions, the maximum obtained CO2 removal efficiency was 79%. Copyright © 2020 BCREC Group. All rights reserved.
Industrial and Engineering Chemistry Research (15205045) 59(19)pp. 8984-8994
The reactive absorption kinetics for SO2 removal from flue gas was studied by the use of a saturated solution of Ca(OH)2 in a bench-scale jet bubbling reactor (JBR). Gas- and liquid-side mass transfer coefficients were determined using suitable chemical and physical absorption methods in the JBR. The influences of main parameters, such as the gas flowrate, concentration of inlet SO2, slurry pH, slurry temperature, and sparger submergence depth, were investigated on the rate of SO2 absorption in the JBR. The results obtained from the kinetic study of SO2 absorption by Ca(OH)2 solution showed that the reaction was empirically a pseudo-first-order fast reaction concerning SO2. The mass transfer rate in this process was much lower than the chemical reaction rate; therefore, the mass transfer was the main controlling step. Moreover, a model was proposed and validated for the absorption rate of SO2 into Ca(OH)2 in the JBR. The validation results showed that the calculated values were in good agreement with experimental data. Copyright © 2020 American Chemical Society.
International Journal of Heat and Mass Transfer (00179310) 159
This paper presents the results of experimental study and mathematical modeling of thermal energy recovery from the flue gases in a packed bed using phase change materials (PCMs). Air and water were used as the heat transfer fluids (HTFs) in the heating and cooling periods, respectively. Paraffin wax was used as the PCM which was encapsulated within polyethylene spheres of 40 mm diameter. The effect of temperature and velocity of the entering air to the bed on the system performance was investigated. In addition, mathematical modeling was conducted, and its numerical results were compared with experimental data. Moreover, two dimensionless parameters (i.e. efficiency and yield) were defined to evaluate the system performance under various operating conditions. The results of this study showed that the efficiency of energy recovery in the considered system could be increased by increasing the inlet gas temperature and decreasing the inlet gas velocity. A 40% increase in inlet gas temperature at constant gas velocity increases the system efficiency by up to 44%. Besides, the mathematical modeling results showed a good agreement with the experimental data. © 2020
Applied Thermal Engineering (13594311) 170
In this study, a pilot plant of a triangular channel solar air heater with a U-turn airflow pattern was constructed and its performance was investigated using a developed model and experimental data under different operating conditions. A new equivalent radiation-convection circuit was developed as the most sophisticated part of the model. Based on the circuit, a mathematical model with minimal simplifying assumptions was developed to predict the performance of the heater. Compared with the results of an integral model of overall energy balance equations, the developed model showed a 50% reduction of error in prediction of thermal efficiency and outlet air temperature. The maximum thermal efficiency of the system could be obtained at an air mass flow rate of 0.045 kg/s (i.e. mass flux of 8.18 kg/m2.s). Considering the air pressure drop (as the most important penalty) and outlet air temperature, the highest thermohydraulic performance was obtained at a channel internal peak angle of 60°. Besides, the results indicated that to achieve a certain thermal efficiency, the presented solar air heater requires less surface area than that of a flat plate solar air heater for the same input solar radiation. © 2020 Elsevier Ltd
Applied Thermal Engineering (13594311) 180
In this study, the vacuum desalination technology coupled with a heat pump was investigated. Two vacuum humidification-dehumidification desalination systems were experimented. The proposed systems involved the over-atmospheric and atmospheric pressure dehumidification operations denoted by Processes 1 and 2, respectively. The more efficient process was determined through a parametric study based on the desalination rate and specific power consumption. The results indicated that decreasing the humidifier pressure and using a heat pump at the optimum value of saline water to air mass flow rate ratio, a maximum desalination rate of 1.12 kg·h−1 (per 1 m2 of solar water heater aperture area) was obtained. Coupling the heat pump to the efficient process had desirable effects on the desalination rate and produced water cost, with a negligible negative impact on the specific power consumption. Although the airflow rate was considered constant in simulation, its fixing was not possible in experimental work. In actual operation, a reduction in airflow rate was occurred by humidifier pressure reduction, which led to system performance reduction. © 2020
International Journal of Thermal Sciences (12900729) 145
Calcium sulfate fouling was determined experimentally in a heat exchanger during liquid–solid fluidized bed with cylindrical particles and forced convective (without particles) heat transfer. Then a model to predict the fouling resistance during the solid–liquid fluidized bed heating system was proposed. According to the proposed model and experimental data, a correlation is presented for the prediction of fouling resistances of calcium sulfate during liquid–solid fluidized bed heating at any time. Finally, the prediction of the presented correlation for performed fouling is compared with measured data. Results show that the absolute average percent relative error between experimental data and those obtained by the proposed model vary between 0.6 and 22.8. © 2019 Elsevier Masson SAS
Tahmasebi-boldaji, R. ,
Hatamipour, M.S. ,
Khanahmadi, M. ,
Sadeh, P. ,
Najafipour, I. Ultrasonics Sonochemistry (13504177) 57pp. 89-97
This paper presents the successful application of ultrasound-assisted packed-bed (UAE-PB) method for the extraction of hypericin from the Hypericum perfuratum L. The Soxhlet system was utilized for the determination of suitable solvent from ethanol, methanol or from the mixture of different proportions of ethanol-methanol. The mixture of 50:50 v/v ethanol-methanol was obtained to be the most suitable solvent since it led to the highest extraction amount of hypericin. The extraction amount of hypericin increased by 13.6% and 21.4% when the solvent changed from pure methanol to the mixture of 50:50 v/v ethanol-methanol for the extraction time of 3 and 8 h, respectively. Subsequently, the extraction was conducted through the UAE-PB, and the effects of temperature, time, and the ratio of solvent to the dried plant were studied. The response surface method (RSM) was used to investigate the effect of parameters on the extraction in the UAE-PB system. At the temperature of 60 °C, extraction time of 105 min, and the solvent to plant ratio of 15.3, the maximum extraction yield of hypericin was achieved. In the optimal conditions, the amount of extraction was 0.112 mg hypericin/g dried plant, which was in accordance with the optimized predicted value (0.111 mg hypericin/g dried plant) from Design-Expert software. © 2019
Applied Thermal Engineering (13594311) 160
Variable pressure humidification dehumidification (VPHDH), humidification compression (HC), and conventional humidification dehumidification (HDH) processes are coupled to a heat pump (HP) for enhancement of their performances and desalination rates. Process simulation of the modified processes reveals the superiority of the proposed VPHDH-HP process to HC-HP, HDH-HP and the conventional HDH processes. Due to the superiority of VPHDH processes over conventional HDH processes, coupling them to HP units as a novel idea improves the desalination rate and energy utilization. The effects of dehumidifier to humidifier pressure ratio (PD/PH), humidifier pressure, and the inlet water to air mass flow rate ratio (w/a) on desalination rate and performance ratio (PR) are studied for the VPHDH-HP process as the superior process. Increasing PD/PH within 2.0 to 3.0 range, leads to an increase in desalination rate by 215%. Increasing w/a from 1.5 to 2.0 increases the desalination rate by 15%, while the same from 2.0 to 3 leads to a 53% decrease in the desalination rate for humidifier pressure of 0.5 bara. A cost analysis yields a water cost of US $4.68/m3 in VPHDH-HP system, indicating its performance superiority against its counterparts. © 2019 Elsevier Ltd
Desalination (00119164) 437pp. 73-80
A solar desalination system using the HDH technology with sub-atmospheric pressures inside the humidifier has been experimentally investigated in this study. The influence of inlet water and air temperatures, the absolute humidity of the air, and the ratio of the mass flow rate of water to that of air in the humidifier on the rate of desalinated water production, and gained output ratio (GOR) have been studied. The developed set-up includes a humidifier, a liquid ring vacuum pump, solar air and water heaters, and a double-pipe condenser. The optimum values for the main parameters were determined by the response surface methodology (RSM). The results indicate that the reducing the humidifier pressure has benefits, and intensifies the effects of the other parameters on the production rate of the desalinated water. In this operating condition, the desalinated water production reached a rate of 1.07 L/h·m2, and the maximum GOR was 3.43. To complete a comprehensive study of the proposed plant, a cost evaluation of the developed system has been done. © 2018 Elsevier B.V.
International Journal of Thermal Sciences (12900729) 125pp. 11-22
Calcium sulfate fouling was determined experimentally in a heat exchanger during liquid-solid fluidized bed with cylindrical particles and forced convective (without particles) heat transfer. The effects of bed voidage, wall temperature and foulant concentration on fouling resistance were studied during fluidized bed heating and compared with corresponding cases in forced convective (without particles) heating. The results show that fouling resistance was considerably decreased during fluidized bed heat transfer compared with forced convective heat transfer (without particles). Maximum fouling removal as heat transfer occurred at bed voidages ranging from 0.6 to 0.8; under these conditions, fouling resistance was lowered to at least one-seventh that of similar cases in forced convective heat transfer. © 2017
Reviews in Chemical Engineering (01678299) 34(6)pp. 743-766
This article reviews the major research and development on spouted beds (SBs). Due to its unique structural and flow characteristics, the SB is a very successful system in most applications. Two-phase and sometimes three-phase interactions generate a large number of variables to be noted in each process. Up-To-date information on the fundamentals and applications of SBs has been briefly presented, based on the published works. Thousands of interesting studies on hydrodynamic characteristics, numerical simulations, and new applications of SBs are reported. In the first step, the present work presents a review of hydrodynamic characteristics (circulation of solids in SB, measurement techniques for particle tracking and empirical hydrodynamics, pressure drop, maximum spoutable height, minimum spouting velocity, and diameter of the spout). In the second step, main mathematical models and computational fluid dynamics (CFD) simulation of the SB to predict and analyze different processes are described. Some main mathematical modeling and the recent advances of two fluid methods and discrete element method approaches in CFD simulation of SBs are summarized. In the last step, some new applications of the SB are presented. As the result of this review, we can observe the importance of further development of hydrodynamics structure, working on modeling and related correlations and improve the applications of SBs. © 2018 Walter de Gruyter GmbH, Berlin/Boston 2018.
Desalination (00119164) 433pp. 48-55
The performance of humidifier was studied in a solar humidification-dehumidification desalination in which dehumidification is carried out by compression. The modified mathematical models were developed to investigate the effect of operating condition on humidifier performance. The modeling results were evaluated by experimental data and compared with those of another mathematical modeling. The results showed, in the mathematical model with insulation effect the model precision increases compared to the model without insulation effect and the absolute error is decreased up to 2.4% based on experimental data. © 2017
Energy Conversion and Management (01968904) 162pp. 321-330
Variable pressure humidification technology is proposed for seawater desalination through evaporation at pressure(s) less than atmospheric and subsequent condensation. Two sub-atmospheric humidification processes (process-I and II) utilizing solar heat are proposed and assessed theoretically. The desalinated water production rate, gained output ratio and an economical comparison between processes are made subject to similar operating conditions. It is deduced that, under similar conditions, pressure reduction from 0.9 bara to 0.1 bara leads to approximately 50% increase in the desalinated water production rate in each of the proposed processes. For humidifier pressures less than atmospheric pressure, the maximum gained output ratio for process-II is higher by 139.13% than that of process-I while the distilled water production rate is lower by 5.71%. Unlike other variable pressure desalination processes, there is no need to use compressor when the vacuum pump is present. To have a comprehensive study of the proposed systems and determine their feasibilities, a cost analysis is conducted. The result of cost analysis indicates that the total cost per liter of distilled water in two proposed process are 0.034 and 0.041 US $/L, respectively. This value is estimated to be reduced to 0.002 US $/L for an industrial scale variable pressure humidification-dehumidification plant. © 2018 Elsevier Ltd
Industrial Crops and Products (09266690) 108pp. 767-774
Glycyrrhiza glabra residue (GGR) contains 30.5% cellulose and 23.0% hemicellulose and can be considered as a promising low-cost and non-edible feedstock for production of ethanol. For the first time, GGR was subjected to inexpensive sodium hydroxide (SH) pretreatment to enhance fermentable sugars production through enzymatic hydrolysis and subsequent utilization by fungus Mucor hiemalis. The pretreatment was carried out at 5% (w/v) solid loading and different temperatures (0, 28 and 110 °C) with 2, 4, 6, 8 and 10% (w/v) SH solutions. When applying no pretreatment, the glucose and ethanol production yields through separated hydrolysis and fermentation of GGR were only 13.9% and 14.3%, respectively. However, a major improvement was achieved after alkali pretreatment of GGR and the maximum hydrolysis yield of 93.7% was observed when the substrate was pretreated with 4% SH solution at 28 °C for 24 h. Consequently, fermentation of the SH pretreated materials by M. hiemalis led to a maximum 5.9-fold increase in ethanol production yield (∼217 kg per ton of GGR), which was slightly higher than the ethanol yield through the yeast Saccharomyces cerevisiae (∼207 kg per ton of GGR). Semi-quantitative analyses of the substrate after pretreatment indicated that crystallinity reduction and expanded surface area were the main reasons for the observed improvements. In brief, the results revealed that SH pretreatment (4% w/v) at room temperature is an effective strategy to valorize GGR to ethanol through hydrolysis and fermentation by fungus M. hiemalis. © 2017 Elsevier B.V.
Canadian Journal of Chemical Engineering (00084034) 95(6)pp. 1150-1155
Simultaneous absorption of CO2 and SO2 was analyzed using the Taguchi method for NaOH solution in a powder particle spouted bed reactor. Experimental results revealed that CO2 removal efficiency increased as the inlet CO2 concentration inlet gas temperature and Na/C molar ratio increases and decreases as the inlet SO2 concentration and gas flow rate decreases. A 68.564% maximum CO2 removal efficiency was achieved under optimal conditions of 13.55 m3/h gas flow rate 1400 Μg/g of flue gas for inlet CO2 concentration 0.0 Μg/g of flue gas for inlet SO2 concentration 200 °C and 2.4 Na/C molar ratio.
Heat and Mass Transfer (09477411) 52(11)pp. 2391-2400
Most correlations presented for the heat transfer coefficient of liquid–solid fluidized bed heat exchangers are based on experiments with glass bead particles in particulate fluidization which usually under-predict the heat transfer coefficient. The present study used experimental data from previous studies for the heat transfer coefficient in liquid–solid fluidized bed heating systems using cylindrical metal particles and five heat transfer correlations based on experiments with spherical glass beads to approximate the behavior of the cylindrical metal particles under aggregative conditions. The results show that modifying the correlations significantly improved the prediction of heat transfer coefficients and the average relative error decreased in comparison with those for the original correlations. © 2016, Springer-Verlag Berlin Heidelberg.
Desalination and Water Treatment (19443994) 57(33)pp. 15285-15292
The performance of humidification-dehumidification desalination, in which dehumidification is carried out by compression, was studied experimentally. A test rig was designed and assembled based on a new idea. In this system, the carrier gas is humidified through direct contact with hot water; and after humidification, the humid air is compressed by a compressor and cooled in a heat exchanger to recover the humidity as desalinated water. The effects of water-to-air ratio, water and air inlet temperatures, operating pressure, and condenser temperature on desalination performance were examined. It was found that the increase in temperature of the feed water and/or inlet air to the humidifier increased the water production rate and gain output ratio (GOR) of the system. The water-to-air ratio showed an increasing-decreasing trend in relation to the water production rate and GOR of the system; the best water-to-air ratio was found to be 2. © 2015 Balaban Desalination Publications. All rights reserved.
Chemical Engineering Research and Design (17443563) 109pp. 180-189
In this article, the reactive absorption of SO2 by seawater is studied in a spray tower experimentally and mathematically. The liquid film formation on the tower wall is implemented in the model and measured experimentally at different operating conditions. The effect of liquid to gas flow rate, initial SO2 concentration in gas phase and initial gas temperature on SO2 removal efficiency is examined. Regarding the importance of liquid droplets hydrodynamics and its effect on the performance of the equipment, the required differential equations for predicting the trajectory and local velocity of droplets are also developed based on the nozzle and spray characteristics and solved simultaneously with other governing equations. In order to survey the effect of nozzle type on removal efficiency, two different types of nozzles are examined. Semi-empirical correlations are proposed for two different nozzles by using experimental data and droplets hydrodynamics model, to predict the amount and the variation of liquid film mass flow rate on the spray tower wall. Results indicate that neglecting the liquid film formation leads to an average of 23% error in predicting the removal efficiency when nozzle type 1 is used, while the calculated error of model by considering the film formation is reduced to 4%. By implementation of droplets hydrodynamics model and applying a modified thermodynamics model for predicting the behavior of the existing chemical reactions, the capability of the spray tower model in predicting the SO2 removal efficiency is enhanced. © 2016 The Institution of Chemical Engineers.
Desalination and Water Treatment (19443994) 54(6)pp. 1526-1541
The technologies that are used mainly in the seawater desalination industry are reviewed and evaluated in this article. The utilization principles, applications, and problems of these processes are summarized and discussed. The desalination methods are compared with each other for performance ratio (PR), gain output ratio (GOR), unit energy consumption (kWh/m3), or unit operating cost ($/m3) and afterward the preferred method is identified. © 2014, © 2014 Balaban Desalination Publications. All rights reserved.
Chemical Engineering Research and Design (17443563) 98pp. 157-167
In a co-current lab-scale spray dryer absorber fitted with a two-fluid nozzle, the removal of carbon dioxide through chemical absorption with NaOH solution as absorbent was investigated experimentally and theoretically. Experimental results showed that in selected ranges of operating parameters, increasing the inlet gas temperature and absorbent concentration has the increasing-decreasing effect on the overall removal efficiency. Also increasing L/G ratio (liquid to gas flow rate), decreasing inlet CO2 concentration and decreasing the droplet mean diameter had favorable effects on overall removal efficiency. Process modeling was done through Computational Fluid Dynamics (CFD) method and using Ansys Fluent 13.0 software. In the three dimensional model of the process the gas phase was modeled as a continuum using the Euler approach and the droplet/particle phase was modeled by the Lagrange approach. An empirical correlation for reaction rate was obtained through experimental data and added to the CFD model of the process as a surface reaction via a user defined function. Predictions of the CFD model were compared to the experimental data. The model prediction in comparison to the experimental trends is fair. © 2015 The Institution of Chemical Engineers.
Process Safety and Environmental Protection (17443598) 98pp. 342-353
In the present study, a comprehensive non-isothermal model is developed to study the performance of a spouted bed reactor (SBR), in which CO2 is removed at the presence of SO2 by using NaOH solution. For this aim, the stream-tube model is applied for hydrodynamics of solid and gas phases, and then by using the conservation laws of mass and energy, the governing equations for gas and solid phases are derived and solved numerically. The effects of variation of different operating parameters and process conditions are evaluated, and by comparing the model results with the gathered experimental data, the maximum, minimum and average error are obtained. The results indicate that the CO2 removal efficiency increases by increasing the inlet CO2 concentration and by decreasing the inlet SO2 concentration, ratio of superficial gas velocity to minimum spouting velocity and inlet gas temperature. Also, the modeling overall results indicate that by increasing the bed diameter and static bed height, CO2 absorption efficiency increases. © 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Polish Journal of Chemical Technology (18994741) 17(3)pp. 13-18
Sweet sorghum juice and traditional ethanol substrate i.e. sugarcane molasses were used for ethanol production in this work. At the end of the fermentation process, the sweet sorghum juice yielded more ethanol with higher ethanol concentration compared to sugarcane molasses in all experiments. The sweet sorghum juice had higher cell viability at high ethanol concentrations and minimum sugar concentration at the end of the fermentation process. The ethanol concentration and yield were 8.9% w/v and 0.45 g/g for sweet sorghum in 80 h and 6.5% w/v and 0.37 g/g for sugarcane molasses in 60 h, respectively. The findings on the physical properties of sweet sorghum juice revealed that it has better physical properties compared to sugarcane molasses, resulting to enhanced performance of sweet sorghum juice for ethanol production © 2015 Mohammad Sadegh Hatamipour et al.
Polish Journal of Chemical Technology (18994741) 16(4)pp. 60-65
In this study, the thin-layer drying characteristics of Figs (Ficus carica) are investigated in a pilot scale forced convective dryer. Experiments carried out under various operating conditions including air temperature (40, 50, 60, 70°C), air velocity (0.65, 2.1, 3.45, 4.85 m/s) and air humidity (0.005, 0.010, 0.015 kg/kg) and the effects of these operating conditions on the drying kinetics and the drying time determined. The obtained kinetics data are fitted into a conceptually developed model. The equilibrium moisture content of the dried figs is determined at different values of temperature and relative humidity of air. The values of effective moisture diffusivity (Deff) are obtained from the Fick's second law and a temperature-dependent relation is proposed for this parameter. © by A. Rahimi 2014.
Chemical Product and Process Modeling (21946159) 9(1)pp. 15-24
The performance of a pilot-scale spray dryer is investigated experimentally and theoretically. The governing equations for flow field, heat and mass transfer, and particle trajectory are solved by applying computational fluid dynamics (CFD). The effects of inlet air temperature and initial particle diameter on the outlet humidity and particle residence time are examined. These parameters should be considered carefully in proper designing of spray dryers especially for the heatsensitive products. The model is validated with an error of 5.5%. Copyright © 2011-2014 by Walter de Gruyter GmbH.
Heat and Mass Transfer (09477411) 50(9)pp. 1291-1300
An unsteady-state model is developed for primary and secondary stages of freeze drying process of skim milk. The results are compared with those obtained from a quasi-steady-state (QSS) formulation. The QSS formulation is not valid where the applied heat load is high. The applied heat load affects on the drying time the most compared to other parameters like chamber pressure and the radiation surface temperature. © 2014 Springer-Verlag Berlin Heidelberg.
Desalination (00119164) 341(1)pp. 120-125
In this communication, a new Humidification De-Humidification process desalination technology is identified which has some advantages (such as: high energy performance, high recovery flow rate, energy recovery and so on) in comparison with other similar methods; this technology is named "Humidification Compression". This method is simulated by a commercial process simulation software and the results are compared with two conventional methods. It is seen that, gain output ratio (GOR) for proposed method is higher than conventional methods; also capital cost per product for proposed method is lower than two others. © 2014 Elsevier B.V.
Drying Technology (15322300) 32(14)pp. 1655-1663
An image processing technique was used to predict the size distribution of the high speed, fine droplets at downstream of an air blast atomizer. The spray visualization setup consisted of UV lamps as light source, a stroboscope for slowing down the droplet motion, and a digital camera to capture the droplet images. The experiments were carried out at different liquid flow rates with various nozzle diameters. Two key unknown parameters (spray half angle and dispersion angle) of the air blast atomizer model in Fluent were obtained from these experiments. Using the obtained parameters and other structural parameters, the spray modeling was performed, and the Rosin–Rammler distribution was obtained and compared with those obtained from image processing technique through a diagnostic matrix. Regarding the kappa value, the agreement between predictions of the Fluent model and the image processing technique was moderate. © 2014, Copyright Taylor & Francis Group, LLC.
Separation Science and Technology (15205754) 49(7)pp. 988-998
Flue gas desulfurization of industrial plants using seawater is studied experimentally and theoretically in a counter-current packed-bed tower. Experiments are carried out based on a 16-run orthogonal array of the Taguchi method (five factors, four levels) and ANOVA table created to determine the most significant controlling factors on SO2 removal efficiency. Liquid flow rate (1.5-4 l/min), gas temperature (50-350°C), gas flow rate (8-20 m3/h), and SO2 concentration (500-2000 ppmv) are revealed as important factors, while the pH of seawater (8-9.5) is not significant. Experimental results show that an increase in gas temperature causes a decrease in the removal efficiency. A mathematical model is developed for the removal of SO2 by seawater for non-isothermal operating conditions. In the modeling procedure the equilibrium reactions of eight dissolved species within the liquid phase are considered to calculate the kinetic of reaction correctly. The results of this study confirm the capability of seawater for SO2 removal in packed-bed towers. Copyright © Taylor & Francis Group, LLC.
Amin, M.M. ,
Hatamipour, M.S. ,
Momenbek, F. ,
Nourmoradi, H. ,
Farhadkhani, M. ,
Mohammadi-moghadam, F. Scientific World Journal (23566140) 2014
The integration of bioventing (BV) and soil vapor extraction (SVE) appears to be an effective combination method for soil decontamination. This paper serves two main purposes: it evaluates the effects of soil water content (SWC) and air flow rate on SVE and it investigates the transition regime between BV and SVE for toluene removal from sandy soils. 96 hours after air injection, more than 97% removal efficiency was achieved in all five experiments (carried out for SVE) including 5, 10, and 15% for SWC and 250 and 500 mL/min for air flow rate on SVE. The highest removal efficiency (>99.5%) of toluene was obtained by the combination of BV and SVE (AIBV: Air Injection Bioventing) after 96 h of air injection at a constant flow rate of 250 mL/min. It was found that AIBV has the highest efficiency for toluene removal from sandy soils and can remediate the vadose zone effectively to meet the soil guideline values for protection of groundwater. © 2014 Mohammad Mehdi Amin et al.
Mohammadi-moghadam, F. ,
Amin, M.M. ,
Khiadani, M. ,
Momenbek, F. ,
Nourmoradi, H. ,
Hatamipour, M.S. Journal Of Environmental And Public Health (16879805) 2013
The aim of this paper is to investigate the removal of toluene from gaseous solution through Glycyrrhiza glabra root (GGR) as a waste material. The batch adsorption experiments were conducted at various conditions including contact time, adsorbate concentration, humidity, and temperature. The adsorption capacity was increased by raising the sorbent humidity up to 50 percent. The adsorption of toluene was also increased over contact time by 12 h when the sorbent was saturated. The pseudo-second-order kinetic model and Freundlich model fitted the adsorption data better than other kinetic and isotherm models, respectively. The Dubinin-Radushkevich (D-R) isotherm also showed that the sorption by GGR was physical in nature. The results of the thermodynamic analysis illustrated that the adsorption process is exothermic. GGR as a novel adsorbent has not previously been used for the adsorption of pollutants. © 2013 Fazel Mohammadi-Moghadam et al.
International Journal of Thermal Sciences (12900729) 74pp. 86-94
This paper is devoted to feasibility study of substitution of two hydrocarbon refrigerants instead of R134a in a domestic refrigerator. Experiments are designed on a refrigerator manufactured for 105 g R134a charge. The effect of parameters including refrigerant type, refrigerant charge and compressor type are investigated. This research is conducted using R436A (mixture of 46% iso-butane and 54% propane) and R600a (pure iso-butane) as hydrocarbon refrigerants, HFC type compressor (designed for R134a) and HC type compressor (designed for R600a). The results show that for HFC type compressor, the optimum refrigerant charges are 60 g and 55 g for R436A and R600a, respectively. Moreover, for this type of compressor, the energy consumption of R436A and R600a at the optimum charges is reduced about 14% and 7%, respectively in comparison to R134a. On the other hand, when using HC type compressor, the optimum refrigerant charges for R436A and R600a are both 50 g, and the energy consumption of R436A and R600a at the optimum charges are reduced about 14.6% and 18.7%, respectively. Furthermore, when the refrigerator is equipped with HC type compressor, working under optimum charges of R436A and R600a have a total equivalent warming impact about 16% and 21% lower than base refrigerator, respectively. Total exergy destruction of the domestic refrigerator with HFC type compressor for R134a, R600a and R436A are 0.0389, 0.0301, 0.0471, respectively and for R600a and R436A with HC type compressor are 0.0292, 0.0472, respectively. © 2013 Elsevier Ltd. All rights reserved.
International Journal of Refrigeration (01407007) 36(4)pp. 1233-1242
Exergy analysis was applied to investigate the performance of a domestic refrigerator originally manufactured to use 145 g of R134a. It was found that the highest exergy destruction occurred in the compressor followed by the condenser, capillary tube, evaporator, and superheating coil. Taguchi method was applied to design experiments to minimize exergy destruction while using R600a. Taguchi parameters were selected by the obtained results from R134a and an experiment using 60 g of R600a, which indicated similar results as R134a. Based on the outcomes, R600a charge amount, condenser fan rotational velocity and compressor coefficient of performance were selected for the design. The analysis of variance results indicated that R600a charge amount was the most effective parameter. At the optimum condition, the amount of charge required for R600a was 50 g, 66% lower than R134a one, which not only brings economic advantages, but also significantly reduces the risk of flammability of the hydrocarbon refrigerant. © 2013 Elsevier Ltd and IIR. All rights reserved.
Korean Journal of Chemical Engineering (19757220) 30(6)pp. 1201-1206
Drying kinetics of quince (Cydonia oblonga) in mashed form was investigated in a pilot scale freeze dryer. Experiments were conducted in various operating conditions, and the effects of initial moisture content, heat load power and the initiation time of heat application were investigated on drying rate and performance of the dryer. The experimental data of the moisture changes were correlated through non-linear regression and an appropriate mathematical model was obtained. The drying kinetics of the sample was determined on the basis of the pre-identified mathematical models as a function of operating parameters. The obtained values of mean relative percent deviation for the kinetics models of the primary and secondary drying stages are 7.47% and 5.94%, respectively. It is revealed that by applying a high heat load power at the beginning of the process the drying time is reduced significantly. © 2013 Korean Institute of Chemical Engineers, Seoul, Korea.
Chemical Engineering and Technology (09307516) 36(3)pp. 500-506
A semi-empirical kinetic correlation was obtained through a shrinking core model assumption for reactive absorption of CO2 with NaOH solution by applying response surface method analogy in a laboratory-scale spray-dryer absorber. The effect of approach temperature, absorbent concentration, nozzle diameter, and L/G ratio on the kinetic coefficient was studied and the optimum operating conditions to reach the maximum absorption were determined. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Journal of Chemical Technology and Biotechnology (02682575) 88(7)pp. 1289-1294
Background: A mathematical modeling approach was used to obtain a simulation model to predict the performance of an industrial rotating disc contactor (RDC) in the extraction of lubricating base oils by furfural. The field data of a lube-oil producing plant was used to validate the model. This model can be used for the parametric study of the RDC column and to investigate the effect of operational data such as solvent and feed temperatures, solvent to feed ratio, and agitation rate on the yield of extraction and on the energy saving value of the extraction. Results: The mathematical modeling of RDC shows good agreement with the plant data with an accuracy of 95% and the model was used to investigate the effect of adding a co-solvent. Conclusion: Results show that by using furfural with added 2,2,4 trimethylpentane it is possible to perform the extraction process at a lower process temperature, 363.15K, compared with 393.15K using furfural as solvent, and also at a lower 1.3 solvent/feed ratio, compared with 1.5 when furfural alone was used for as the solvent. This process modification leads to saving of 38% of the consumed energy per cubic meter of product in the extraction process. © 2012 Society of Chemical Industry.
Industrial and Engineering Chemistry Research (15205045) 52(27)pp. 9422-9432
Previously, several mathematical models have been proposed for liquid-liquid extraction processes involving a rotating-disk-contactor (RDC) column. Most of these models reveal that hydrodynamic and mass-transfer phenomena are important for predicting the performance of the column. In this paper, a mathematical model, using a new scheme, was developed to acquire a simulation tool to predict the performance of a RDC column used in lubricating-oil production. Field data obtained in a RDC column of 4.1 m diameter, 22.2 m height, and 32 disks, from a commercial lubricating-oil production company, were used to evaluate the predictions. The model is used for parametric study to investigate the effects of operational data such as the solvent and feed temperatures, solvent-to-feed ratio, and disk rotation rate on the extraction yield. © 2013 American Chemical Society.
Measurement: Journal of the International Measurement Confederation (02632241) 45(7)pp. 1807-1813
This article presents an experimental investigation of substituting R134a with R436A (a mixture of R290 and R600a with a mass ratio of 56/44) in a 238 L single evaporator domestic refrigerator without any modification in refrigeration cycle. The refrigerator's compressor was charged with different amount of R436A, and in addition to refrigerator's power consumption during operation, the temperatures in different sections of the refrigerator were measured. Results showed that in comparison to the base refrigerator working with R134a, the ON time ratio and the energy consumption per day were reduced by 13% and 5.3%, respectively. Although the original R134a charge for this refrigerator was 105 g, the optimum charge for R436A was reduced to 55 g that exhibits 48% reduction in refrigerant charge. Also replacing R134a charge with R436A raised the energy efficiency index of the refrigerator from label "E" to label "D" according to Iranian National Standard No. 4853-2. © 2012 Published by Elsevier Ltd. All rights reserved.
Drying Technology (15322300) 30(6)pp. 574-582
The wall deposition phenomenon in a pilot-scale spray dryer was investigated based on mathematical modeling and experimental trials. For this purpose, the governing equations were obtained and solved numerically by applying a mathematical modeling technique and an open-source computational fluid dynamics (CFD) software. The wall deposition, velocity distribution of the existing phases, and droplet trajectory in the drying chamber were determined. The effect of the operating parameters including the feed flow rate, inlet concentration of dissolved solid, and initial droplet diameter on the air flow pattern, droplet trajectory, and wall deposition was investigated. Through the experiments, the wall deposition of powder product in different positions of the drying chamber was measured. In modeling part of this study, we attempted to determine the effect of particle diameter on the percentage of wall deposition and the position where it occurred.The model results obtained for wall deposition were compared with collected experimental data and good agreement was observed. © 2012 Copyright Taylor and Francis Group, LLC.
Drying Technology (15322300) 30(2)pp. 128-137
In this study, green pea drying is investigated experimentally in a laboratory-scale spouted bed dryer. A mathematical model is also developed to investigate the effect of operating conditions on the performance of the system. The effect of operating parameters such as inlet air temperature, particle size, and flow rate of the drying air on the performance of the dryer are studied experimentally. In order to build the process model, it is necessary to analyze the transport in both solid and gas phases. A complete set of equations with no adjustable parameters is derived for existing zones in the spouted bed dryer in order to predict variations in the temperature and moisture content of the solid and gas phases with time for batch drying conditions. Model results are compared with corresponding experimental data. Agreement between the model results and experimental data is good. © 2012 Copyright Taylor and Francis Group, LLC.
Computers and Chemical Engineering (00981354) 38pp. 44-51
A mathematical model is developed for simulation of dynamic behavior of coke-burning process in a hydrocracker reactor with an array of 4 fixed beds. The model is used for parametric study of the coke burning process. Results show that the effective parameters are inlet oxygen concentration, the flow rate of carrier gas and temperature within the beds. The effect of referred parameters on performance of regeneration of an industrial hydrocracker reactor is investigated for a real case and the optimum values of operating conditions are predicted. The optimum value for oxygen concentration during regeneration obtained as 0.85. mol%, with a predicted regeneration time of around 76. h. © 2011 Elsevier Ltd.
Applied Thermal Engineering (13594311) 31(5)pp. 670-673
Maryam Moradi, Amir Rahimi, and Mohammad Sadegh Hatamipour from Department of Chemical Engineering, Faculty of Engineering, University of Isfahan, Iran, critically analyze an article titled 'Experimental and numerical investigation of solid particles thermal energy storage unit' by A. Benmansour, M.A. Hamdan, and A. Bengeuddach. Similar boundary and initial conditions are used for comparison of the two referred models. Both of the models have been developed with the assumption that when the temperature of PCM reaches to its melting point, the phase change period begins and the PCM temperature during this period remains constant. After this process is finished and all of the solid paraffin wax melted the temperature begins to rise. In the next section the results of the present model are presented and compared with the results of Benmansour and colleagues, model and also with corresponding experimental data. Unfortunately, the mathematical model results which were reported by Benmansour are not in agreement with this theory.
Chemical Engineering Research and Design (17443563) 89(6)pp. 616-620
In the present study, the carbonation reaction of hydrated lime in semi-dry condition is investigated experimentally in a laboratory-scale spouted bed reactor. Results show that for operating conditions where the concentration of CO2 is low, the capture efficiency is raised by increasing the inlet CO2 concentration. Additionally, because of the inconsistency between the experimental reaction rate and the calculated values based on the previous proposed equations, a new rate equation is introduced that considers the dependency of CO2 concentration too. To validate the proposed equation, its predictions were compared with another set of experimental data. © 2010 The Institution of Chemical Engineers.
Chemical Engineering and Technology (09307516) 34(3)pp. 459-464
An artificial neural network (ANN) approach was used to obtain a simulation model to predict the rotating disc contactor (RDC) performance during the extraction of aromatic hydrocarbons from lube oil cuts, to produce a lubricating base oil using furfural as solvent. The field data used for training the ANN model was obtained from a lubricating oil production company. The input parameters of the ANN model were the volumetric flow rates of feed and solvent, the temperatures of feed and solvent, and the disc rotation rate. The output parameters were the volumetric flow rate of the raffinate phase and the extraction yield. In this study, a feed-forward multi-layer perceptron neural network was successfully used to demonstrate the complex relationship between the mentioned input and output parameters. It is possible to conduct a parametric study of the complex lubricating oil extraction process in an industrial rotating disc contactor column using the artificial neural network (ANN) procedure. The accuracy of the created ANN model was checked by randomly selected data among the archived operational data set of an industrial lubricating oil producer company. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Journal of Chemical Reactor Engineering (15426580) 9
Reactive absorption of CO2 with NaOH as absorbent was evaluated experimentally in a lab scale spray dryer. Taguchi method was used for design of experiments. Results showed that the most important factors are inlet CO2 concentration, nozzle size, absorbent concentration and temperature, respectively. The optimum conditions are 150°C for temperature, 10% (w/w) for NaOH concentration, 10% for CO2 concentration, and 0.5 mm for nozzle diameter. By conducting experiments under the optimum conditions, the removal efficiency was obtained as 69.4%. Copyright © 2011 The Berkeley Electronic Press. All rights reserved.
Drying Technology (15322300) 29(14)pp. 1648-1655
In this study, a drying kinetics model for predicting the drying of green pea particles using a bench-scale spouted bed with heat carriers is investigated. The experiments were carried out under different operating conditions. The effect of inert particle diameter, inert particle type, and the mass ratio of inert particles to green peas was examined based on the performance of the dryer and the rate of drying. As expected, the rate of drying increased with increased mass ratio of inert particles to green peas and thermal diffusivity of inert particles. © 2011 Taylor & Francis Group, LLC.
Separation and Purification Technology (13835866) 80(3)pp. 509-518
In present study, a non-isothermal comprehensive mathematical model is developed for performance analysis of a spouted bed reactor in which CO 2 is removed by using a semi-dry chemical absorption process. For this aim, based on the hydrodynamic model of streamtube and equations of mass and energy balances for a reactive absorption process, the governing equations for gas and solid phases in three different regions of the bed are derived and solved numerically. The effects of variation of different operating parameters and process conditions are investigated and corresponding maximum, minimum and average values of errors are obtained by comparison of the model results with existing experimental ones. Results show that the superficial gas velocity and the approach to saturation temperature have considerable effects on CO 2 removal efficiency, while Ca/C molar ratio, inlet concentration of CO2 and static bed height of reactor do not influence performance of the reactor significantly. © 2011 Elsevier B.V. All rights reserved.
Chemical Engineering Research and Design (17443563) 89(6)pp. 777-784
A mathematical model is developed for investigation of SO2 removal in a powder particle spouted bed (PPSB) for non-isothermal operating condition. For this aim, the stream-tube model which was already validated for such systems is applied for hydrodynamics of solid and gas phases, and then by using the conservation laws of mass and energy, the governing equations for gas and solid phases are derived and solved numerically. The published experimental data in the literature are used to validate the accuracy of the proposed model. The results show that the model is capable of predicting the behaviour of this system properly. Also the optimum performance of this system is investigated by studying the effects of different parameters such as bed height, molar ratio of sorbent to acid gas (Ca/S) and inlet concentration of SO2. © 2010 The Institution of Chemical Engineers.
Chinese Journal of Chemical Engineering (10049541) 18(4)pp. 642-647
Lubricating mineral base oils are normally extracted from lube-oil cuts with furfural solvent. Aromatic content in the raffinate phase from extraction process is an essential parameter that affects the quality of the lubricating base-oils. For determination of aromatic content by the usual ASTM D3238 method, density, refractive index and molecular weight of the raffinate are required. In this work, a new generalized correlation is developed for determination the aromatic content by using only the measured viscosity of lubricating oil. With a mole fraction of aromatic compounds, the kinematic viscosity may be obtained at any temperature between 60-100 (C along with their molecular weight and refractive index. © 2010 Chemical Industry and Engineering Society of China (CIESC) and Chemical Industry Press (CIP)
Food and Bioproducts Processing (09603085) 88(2-3)pp. 133-137
In this paper a new physical pretreatment of plums, consists of piercing them by a thin needle, is proposed to increase the rate of drying. The effect of physical pretreatment on drying time was compared with chemical pretreatment that consists of dipping of plums in hot NaOH solution (1%). Drying experiments were carried out in a convective laboratory dryer at 85 °C and 0.81 m/s air velocity. It was observed that pierced plums were dried faster than chemically pretreated plums. After 480 min moisture ratio of pierced sample was 0.07 while for the chemical method it was 0.25. The moisture ratio at any time was compared with seven different mathematical models and the best model was determined according to the best agreement. Accordingly, two-term exponential model for moisture ratio is found to be superior to the other proposed models. The effective diffusivity was found to be 5.471 × 10-9 m2/s for chemically pretreated and 1.016 × 10-8 m2/s for physically pretreated plums. © 2009 The Institution of Chemical Engineers.
Energy (18736785) 35(5)pp. 2130-2133
Industrial processes are the most energy consuming processes in the world. Modification of these processes helps us with controlling the consumption of energy and minimizing energy loss. Changing raw materials is one of the ways through which we can optimize industrial processes. In this paper, a new solvent mixture (furfural + a co-solvent) was used for the extraction of lubricating base oil from lube-oil cut. It was found that the energy consumption of the new solvent mixture for obtaining a product with the same quality was much lower than the original solvent. By using this new solvent mixture, the operating temperature of the top of tower was reduced by 30 K. This leads to a high reduction in energy consumption in extraction of aromatics from lube oil. At our new extraction process by means of using new solvent mixture, the maximum energy saving was 38% per cubic meter of produced raffinate. © 2010 Elsevier Ltd. All rights reserved.
Desalination (00119164) 250(1)pp. 203-207
Economical study of humidification-dehumidification desalination (HDD) pilot plant was made in order to estimate the economic benefits of the process in comparison with a small-scale reverse osmosis (RO) system. The energy recovery of the unit was investigated to be 75%. Some theoretical modifications were made to the HDD system in order to reduce the energy costs of the unit. Exact and clear economic analysis results were obtained using COMFAR ΙΙΙ software including fixed investment costs, production costs, internal rate of return on investment, operating costs, energy costs and some other economical parameters. Based on the energy prices in Iran, the total fresh water production cost was calculated to be $ 6.4/m3 that was nearly the same as produced by an imported RO plant. Finally some points were recommended whether to choose HDD or RO plant in different cases and capacities. © 2009 Elsevier B.V. All rights reserved.
International Journal of Food Science and Technology (09505423) 45(12)pp. 2546-2552
Drying of Green Peas (Pisum sativum) was studied experimentally in a lab-scale spouted bed. Experiments were carried out at different operating conditions, and the effect of inlet air temperature and its flow rate, bed height (initial mass of wet particles) and average diameter of particles were examined on performance of dryer and rate of drying. The obtained experimental results were fitted by an exponential form equation to model the drying kinetic behaviour of green peas in a spouted bed. The fitting parameters are presented in the form of mathematical correlations as a function of operating parameters. As expected, it was found that by increasing inlet air temperature and air-flow rate, the rate of drying increases, but by increasing the bed height and diameter of particles, the rate of drying decreases. The results can help the design engineers to choose the optimum drying conditions for industrial applications. © 2010 The Authors. International Journal of Food Science and Technology © 2010 Institute of Food Science and Technology.
Drying Technology (15322300) 28(4)pp. 490-494
Leavening activity is an important quality index in the baker's yeast industry. In this work, Taguchi's experimental design was used to investigate the effect of important factors on the leavening activity of Saccharomyces cerevisiae during spray drying. Feed rate and inlet air temperature are the most important factors in spray drying of baker's yeast. The amount of starch as a processing aid also has a considerable effect on the leavening activity of the yeast. © 2010 Taylor & Francis Group.
Separation and Purification Technology (13835866) 72(3)pp. 288-293
The performance of a powder-particle spouted bed (PPSB) on the removal of CO2 is investigated. A laboratory scale PPSB is employed to investigate the effects of operating parameters such as approach to saturation temperature, static bed height, Ca/C molar ratio, inlet CO2 concentration and type of sorbent on CO2 removal efficiency. The experimental results show that the CO2 removal efficiency increases by increasing the static bed height, Ca/C molar ratio and inlet CO2 concentration, and decreases by increasing the approach to saturation temperature and superficial gas velocity. Also it is concluded that maximum CO2 removal efficiency could be up to 50% when approach to saturation temperature is 8 K, Ca/C molar ratio is 1.4 and the static bed height is 0.225 m. © 2010 Elsevier B.V. All rights reserved.
Special Topics and Reviews in Porous Media (21514798) 1(3)pp. 231-241
Using the mathematical modeling technique, the reaction rate constant for high temperature and pressure coke-burning processes was obtained by considering a simple reaction rate equation; while in accordance with the industrial operating conditions the feed rate and inlet oxygen concentration were changed continuously with time. Using the precise data of a real regeneration process and adjusting the reaction's rate constant for matching the results of the model with the experimental data, the rate of reaction was estimated. The precision of the method and the reaction rate is validated by using another set of experimental data. The obtained kinetics along with the mathematical model is able to predict the behavior of the coke-burning process with an acceptable error for applied aims. © 2010 by Begell House, Inc.
Industrial and Engineering Chemistry Research (15205045) 48(20)pp. 9325-9330
The use of 2,2,4-tri methyl pentane as a cosolvent for extraction of aromatic hydrocarbons from lube cut is studied. Optimized values of extraction temperature and amount of 2,2,4-tri methyl pentane are determined. The liquid-liquid equilibrium between {lube oil + furfural + cosolvent} is examined with the NRTL equation. The binary interaction parameters for the NRTL model are obtained by minimization of an objective function. General binary interaction parameters are computed and reported for estimating the liquid-liquid equilibrium products between 323.15 and 343.15 K. Also, a generalized model is presented for calculation of the refractive index and specific gravity of lube-oil fractions. The calculated results are in good agreement with the results of the experiments. © 2009 American Chemical Society.
Separation and Purification Technology (13835866) 66(1)pp. 167-170
Liquid-liquid extraction is the most common method for extraction of aromatics from lube oil. Aromatic content of vacuum distillate is reduced by solvent extraction, frequently with furfural. The solvent power and selectivity of furfural can be further increased by using n-hexane as co-solvent. The aromatics in lube oil were extracted at different temperatures (ranging from 323.15 to 343.15 K) and different co-solvent to feed volume ratios (ranging from 0.0 to 0.5). The extraction temperature and the amount of n-hexane in furfural were investigated systematically in order to determine their optimum values. The amounts of aromatic, paraffinic and naphthenic compounds were determined using ASTM standards by measuring refractive index (RI), viscosity, molecular weight and sulfur content. It was found that using 11% n-hexane at 333.15 K yields the optimum extraction conditions. © 2008 Elsevier B.V. All rights reserved.
Journal of Chemical and Engineering Data (00219568) 54(6)pp. 1871-1875
Experimental data for liquid-liquid equilibrium of the lube-oil cut + furfural system is determined. The effect of the solvent-to-feed ratio and the operating temperature on the distribution of aromatic, naphthenic, paraffinic, and furfural in extract and raffinate phases is investigated. We determined the aromatic, naphthenic, and paraffinic content of raffinate and extract phases by using the ASTM standard methods. © 2009 American Chemical Society.
Desalination (00119164) 237(1-3)pp. 296-304
Using air as a carrier gas is common in humidification-dehumidification desalination processes. A computer program was written using mass and energy balances for modeling the process behavior. The parameters considered in this work were inlet air and fresh water recycle temperatures, inlet air flow rate, saline water and fresh water recycle flow rates, and saline water to air flow ratio. Results of simulation showed that increasing inlet air and fresh water recycle flow rate increases fresh water production. It was also found that heating the inlet air to humidification column or cooling the inlet water to dehumidification column increases the production rate but increasing water to air flow ratio in a humidifier leads to a lower production rate. The predicted effects of the parameters on fresh water production agreed well with the existing experimental data. © 2008 Elsevier B.V. All rights reserved.
Journal of Porous Media (19340508) 12(4)pp. 369-377
The effect of heat carriers on heat transfer to a cylindrical metal bar was investigated theoretically. The usual models for wall heat transfer in fluidized beds was extended for heat transfer to an immersed cylinder in a fluidized bed by considering the physical properties of the heat carriers in the thermal diffusivity of the emulsion layer. The heat transfer coefficient predicted by film penetration theory was acceptable and the predictions of model had good agreement with experimental data. It was found that heat carriers with high thermal conductivity and low specific heat can enhance the heat transfer rate more than carriers with low thermal conductivity and high specific heat. Copyright © 2009 Begell House, Inc.
Process Safety and Environmental Protection (17443598) 86(3)pp. 208-212
Seven strains isolated from DSO (disulfide oil) contaminated soils. Among them, two strains had high potential to remove DSO from contaminated soils. These strains identified as Paenibacillus (a gram positive, nitrogen fixing spore, spore forming bacillus) and Rhodococcus (a gram positive, catalase positive, acid fast forming bacteria), by preliminary tests. The optimal conditions for DSO removal from contaminated soils were determined. The biotic depletion for Paenibacillus pre-grown in nutrient broth was 24.3% and for Rhodococcus was 19.3%. Bioremediation of DSO in soil was investigated by gas chromatography and UV-vis absorption spectroscopy techniques. The results showed that addition of water (20 μl/g soil) to soil is necessary for DSO removal by both strains and none of the strains could remove DSO in concentrations more than 30 μg/g soil. The results also showed that none of these strains could degrade DSO under anaerobic condition. © 2008 The Institution of Chemical Engineers.
Chemical Engineering and Technology (09307516) 31(1)pp. 71-82
The powder-particle spouted bed process is one of the semi-dry processes that have been developed for flue gas desulfurization. In this study, which is designed for SO2 removal by a powder-particle spouted bed, the reaction term is included in one-dimensional and streamtube models that were presented previously for spouted beds. Hydrated lime is used as the sorbent in this process. The predictions of the models are compared with some published experimental data and it is found that the developed models are valid. The results of two models are compared with each other and their various properties are evaluated. The effects of different operating conditions on SO2 removal efficiency are also investigated and preferred operating conditions are discussed. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
The GOS method was applied for solving the heat exchanger network synthesis problems. For solving these problems first, the sources of non-convexities were identified. The variables and constraints were decomposed into two sets. This led to the decomposition of original MINLP problem into two convex subproblems, which can be solved for their respective global solution. Based on the generalized Bender's decomposition method, this approach then solved a series of these subproblems to arrive at the optimal solution. Even though the proposed approach cannot mathematically guarantee the identification of the global optimum, the global optimization technique applied to a number of HENS problems determined the global solution in all cases from various starting points. The mathematical modeling of heat exchanger network synthesis and the modified global optimum search approach was implemented automatically using the modeling language GAMS. This is an abstract of a paper presented at the 18th International Congress of Chemical Process Engineering (Praque, Czech Republic 8/24-28/2008).
Energy Conversion and Management (01968904) 49(8)pp. 2317-2323
This article presents useful ancient energy technologies that have been used many years for natural cooling of buildings during summer in a hot and humid province in the South of Iran. By use of these technologies, people were able to live in comfort without any electrical air conditioning system. These technologies include use of color glazed windows, wooden windows frames, light colored walls and roofs, insulated walls, wooden roofs covered with leaves and mud. In addition, these technologies made use of terraces, use of louvers, constructing the lanes as narrow as possible and shading the buildings with the nearby buildings, all of which are now the modern experienced technologies. © 2008 Elsevier Ltd. All rights reserved.
Food and Bioproducts Processing (09603085) 85(3 C)pp. 171-177
In this work, which was designed for drying of agro-food products, six varieties of potatoes (Santana, Santea, Marfona, Diamant, Koncord, Renjer) were chosen as drying material. A pilot-scale tray dryer, with and without air circulation, and a fluidized bed dryer were used for performing drying experiments. The experiments were performed with and without blanching. The changes in structure and colour of six varieties of potatoes were studied. Temperature did not show significant effect on shrinkage, but blanching time and air circulation had significant effect on shrinkage as well as on the appearance of dried product. Less shrinkage occurred in Renjer and Diamant varieties at 80°C in comparison with other varieties. Santana (at 80°C), Santea (at 70°C) and Renjer (at 80°C) had better appearance and colour after free convection drying, whereas the appearance, colour and quality of Marfona variety was not acceptable at all. The quality and appearance of Marfona variety improved by using a tray dryer with air circulation. The quality and appearance of all varieties was very good in fluidized bed dryer. Blanching was effective in improving the colour of all dried varieties. © 2007 Institution of Chemical Engineers.
Energy and Buildings (03787788) 39(1)pp. 105-112
This work was designed to estimate the cooling load power consumption during the summer in the hot and humid areas of Iran. The actual electrical energy consumption for cooling systems of some typical buildings with various applications (3 residential home buildings, 2 industrial plant buildings, a trade center with 38 shops, 3 public sectors and a city hospital) in a hot and humid region in South of Iran was recorded during the peak load period of the year (July-August). The records were used for estimating the total power consumption of the cooling systems in this region. According to this estimation, which was confirmed by the regional electrical power distribution office, the cooling systems power consumption in this region accounted for more than 60% of the total power consumption during the peak load period of the year. A computer program was developed for simulating the effect of various parameters on cooling load of the buildings in hot and humid regions. According to the simulation results, use of double glazed windows, light colored walls and roofs, and insulated walls and roofs can reduce the cooling load of the buildings more than 40%. © 2006 Elsevier B.V. All rights reserved.
Chemical Engineering and Technology (09307516) 30(11)pp. 1584-1589
The unsteady-state simultaneous heat and mass transfer between gas and potato cubes during the drying process in a batch fluidized bed was described by a mathematical model. Mass transfer was considered to occur in three dimensions whereas heat transfer between the gas and dried material was assumed to be lumped. It was found that the model could describe the drying process with acceptable accuracy. The moisture profile inside the material at any cross-section and at any time can be predicted by the model. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Food and Bioproducts Processing (09603085) 84(3 C)pp. 220-226
Drying behaviour of maize and green peas was investigated in a bench scale fluidized bed dryer with an inert energy carrier (2.7 mm glass beads and steel balls). The effects of drying solid diameter, inert material type, amount of inert material, air velocity and temperature on the rate of drying were studied. A mathematical model is proposed for predicting the drying rate and temperature variation of spherical shape drying solids. It was found that presence of inert particles enhances the rate of drying. The rate of drying increases with decreasing drying solid diameter, increasing the inert material thermal conductivity and increasing air temperature. However, air velocity, amount of inert material and initial moisture content have no appreciable effects on the rate of drying in well fluidized systems. The independence of rate of drying on air velocity especially in well-fluidized systems indicates that external convection is not a controlling step in this process. Experimental results showed that drying rate decreases by increasing the mass ratio of drying solid to inert material. © 2006 Institution of Chemical Engineers.
Journal of Porous Media (19340508) 9(4)pp. 373-380
The effect of heat carriers on heat transfer to a cylindrical metal bar was investigated in a lab setup fluidized bed with small spherical solids (2.7 mm glass beads and steel balls). Rods of aluminum and steel, each with 10 and 20 mm diameter and 60 mm length, were heated by means of hot air. In each experiment, the temperature of the center of solid was measured at various intervals of time. The effect of various parameters such as air velocity, air temperature, mass ratio of fluidizing material to solid, type of fluidizing material, diameter of fluidizing material, and diameter of solid were investigated. The rate of heat transfer increases with decreasing immersed solid diameter, increasing the fluidizing material thermal conductivity, decreasing fluidizing medium size, and increasing air temperature, but air velocity and amount of fluidizing material must be optimized to convert the system to a well-fluidized system and maximize the rate of heat transfer. Copyright © 2006 Begell House, Inc.
Journal of Food Engineering (02608774) 59(2-3)pp. 221-227
Drying behavior of maize and green peas investigated in a pilot scale fluidized bed dryer with inert energy carriers. The variations of drying material density, size and mass diffusivity with change of moisture content were investigated. It was found that, air temperature, inert material, and air velocity had no significant effect on physical properties and therefore, shrinkage and density are only functions of moisture content, but diffusivity is a function of temperature and moisture content. Based on the experimental data obtained, some correlations were developed for variation of shrinkage, density and diffusivity of green peas and maize during drying in a fluidized bed with inert particles. The shrinkage, density and moisture diffusivity of green peas and maize could be predicted by an average accuracy of 98% by use of proposed correlations. © 2003 Elsevier Science Ltd. All rights reserved.
Drying Technology (15322300) 21(1)pp. 83-101
A pilot scale fluidized bed dryer with an inert energy carrier (steel, glass beads ranging from 2.7 to 6.5 mm) was used to investigate the drying of carrots. The effects of sample diameter, inert material type, inert material diameter, amount of inert material, air velocity, and temperature on the rate of drying were studied. A mathematical model was proposed for predicting the drying rate and temperature of drying material. It was found that presence of inert particles enhance the rate of drying. The results of this study also revealed that, although the rate of drying increases with decreasing sample diameter, increasing the inert material thermal conductivity, and increasing air temperature, but the inert material diameter and air velocity have no significant effects on the rate of drying. The independence of rate of drying on air velocity especially in well-fluidized systems indicates that external diffusion is not a controlling step in this process. Also the presence of inert materials causes the drying material to reach more rapidly to its final internal temperature.
Chemical Engineering and Technology (09307516) 26(1)pp. 43-49
A pilot scale fluidized bed dryer with inert particles as energy carrier was used to investigate the drying characteristics of carrot in this type of dryer. Glass beads, hollow steel balls and pieces of dry carrot were used as inert materials. The effects of sample diameter, inner material type, inert material diameter, amount of inert material, air velocity and temperature on the rate of drying were studied. It was found that the presence of inert particles enhances the rate of drying. The results of this study also revealed that, although the rate of drying increased with decreasing sample diameter, increasing of inert material thermal conductivity, and increasing of air temperature, but the inert material diameter and air velocity did not have any significant effect on the rate of drying. The independence of the rate of drying on air velocity in well fluidized systems, indicates that external diffusion is not the controlling step in this process. It was also found that the presence of inert materials caused the drying material to reach its final internal temperature more rapidly. The internal temperature of the drying material, also increased with increasing diameter and thermal conductivity of the inert materials.
Chemical Engineering Communications (00986445) 190(4)pp. 508-518
In this paper some experimental results showing the influence of inclination of a cylindrical heating surface immersed in an air duct on heat transfer coefficient are presented. The experiments were performed in a laboratory-scaled apparatus of square cross section with dimensions 120 × 120 mm and 1400 mm in height. Heat transfer surface was an electrical heater made of brass tube with outer diameter of 19 mm and 110 mm length. In each experiment the temperatures of the front and rear side of the heating surface, inclination angle, air velocity, inlet air temperature, and heater power were measured. It was concluded that heat transfer coefficient depends on flow conditions and angle of inclination. The maximum Nusselt number (Nu) was observed to occur about 45° inclination relative to the horizon, for the range of Reynolds numbers used in experiments. The values of heat transfer coefficients in the vertical position were very nearly the same as they were in the horizontal position. Based on the experimental results, a correlation was proposed for estimation of Nu at the desired flow velocity and inclination angle, relative to Nu at zero inclination.
Journal of Food Engineering (02608774) 55(3)pp. 247-252
Agricultural food products and specially root vegetables undergo several physical and structural modifications during the drying process. Shrinkage of root vegetables during drying is important not only from the viewpoint of material end-use but also for simulation problems. In this paper the shrinkage of root vegetables is studied in a pilot-scale, inert medium fluidized bed dryer. Cylindrical carrot samples were utilized as the test media, providing simulants for high moisture content food systems. The effects of various parameters such as air temperature, air humidity, sample diameter, sample initial moisture content, existence of inert particles and air velocity were investigated. It was found that the shrinkage of root vegetables during drying in a fluidized bed could be well correlated with moisture content of the sample during drying. Air velocity, temperature and presence of inerts did not show significant effects on shrinkage in this system. © 2002 Elsevier Science Ltd. All rights reserved.
IRANIAN JOURNAL OF SCIENCE AND TECHNOLOGY (03601307) 23(3)pp. 180-181
Madder (Rubia tinctrum) is a plant growing in areas such as south east Asia, and Europe. Over the ages its root has been used for dyeing wool and natural silk fibers, but the traditional methods of dyeing suffer from some disadvantages such as the long time required for dyeing, low brightness of fibers, etc. For this reason, the extraction of coloring matters of madder root has been performed and the parameters have been experimentally optimized. In the present article, a brief explanation of the methods, and the design procedure for the extraction unit, along with other extraction conditions have been thoroughly investigated. Equilibrium data for solid-liquid in the leaching process at different temperatures as well as different solvents have been experimentally obtained. © Shiraz University.
