High Feed Concentration Research Articles

Performance of Different Inert Gases in Production of Fuel Grade Ethanol by Diffusion Distillation

Performance of sulfur hexafluoride, nitrogen, argon, and helium inert gases was investigated in a view to produce fuel grade ethanol by diffusion distillation. Stefan–Maxwell equations based mathematical model was used for this study. Modeling results were also compared with the own experimental data. Shifting of azeotrope to different extents was observed by using different inert gases as selective filter. As the selected inert gas becomes lighter, narrow concentration range for positive selectivity was found. Sulfur hexafluoride was found to be the most suitable inert gas for ethanol dehydration by diffusion distillation, and quantity $${{S}_{{{\text{az}}}}}({{N{}_{2}} \mathord{\left/ {\vphantom {{N{}_{2}} {{{N}_{1}}}}} \right. \kern-0em} {{{N}_{1}}}})$$ , which represents the overall performance of any inert gas, was also found to be highest for this gas out of all the inert gases studied. Sulfur hexafluoride gas also allows to work at high vaporization temperature, which facilitates the high transfer efficiency. If light gases are to be used they should be used for high feed concentrations and at low vaporization temperatures to achieve the high degree of separation.

Optimized Continuous Multicolumn Chromatography Enables Increased Productivities and Cost Savings by Employing More Columns.

The advantages of continuous chromatography with respect to increased capacity are well established. However, the impact of different loading scenarios and total number of columns on the process economics has not been addressed. Here four different continuous multicolumn chromatography (MCC) loading scenarios are evaluated for process performance and economics in the context of a Protein A mAb capture step. To do so, a computational chromatography model is validated experimentally. The model is then used to predict process performance for each of the loading methods. A wide range of feed concentrations and residence times are considered, and the responses of operating binding capacity, specific productivity, and the number of process columns are calculated. Processes that are able to add more columns proved to be up to 65% more productive, especially at feed concentrations above 5 g L-1 . An investigation of the operating costs shows that discrete column sizing and process performance metrics do not always correlate and that the most productive process is not necessarily the most cost effective. However, adding more columns for the non-load steps at higher feed concentrations allows for overall cost savings of up to 32%.

Optimization of structural parameters of an inner preheating transpiring-wall SCWO reactor

A computational fluid dynamics model of an inner preheating transpiring wall reactor for supercritical water oxidation was proposed to optimize the structural parameters. Results showed that higher feed degradation efficiencies and lower inner surface temperatures of the porous wall were obtained at higher reactor diameters. Although the increase in reactor length promoted feed degradation, the increased inner surface temperatures of the porous wall were unsuitable for water film formation. A pyknic-type reactor with a lower length/diameter (H/D) value at a constant volume was more beneficial for water film formation and feed degradation. A higher feed concentration or feed flow required a lower H/D value to ensure an ideal water film formation and feed degradation. We proposed the use of sectional heat load as a new parameter for reactor design based on the similarity between the boiler furnace and the transpiring wall reactor. The sectional heat load in a certain range was calculated to serve as guide in the design of transpiring wall reactors.

Extractive-Catalytic Oxidative Desulfurization with Graphene Oxide-Based Heteropolyacid Catalysts: Investigation of Affective Parameters and Kinetic Modeling

Different tungsten and molybdenum containing heteropolyacid (HPA) catalysts (H3PMo12O40:Mo12, H3PMo8W4O40:Mo8W4, H3PMo6W6O40:Mo6W6, H3PW12O40:W12) were immobilized on graphene oxide (GO) to obtain HPA–GO heterogeneous catalysts (Mo12–GO, Mo8W4–GO, Mo6W6–GO, and W12–GO). The synthesized catalysts were applied in removal of sulfur containing compounds [benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT)] with combined extraction–oxidation process using a batch reactor. The sulfur removal efficiency was gradually increased with increasing the ratio of molybdenum ions in the HPAs and complete sulfur removal efficiency for DBT was obtained for Mo12–GO. The roles of affecting parameters such as extracting solvent, catalyst calcination, and feed concentration were also investigated. Among different extracting solvents including acetonitrile, DMF, NMP, methanol, water, and ethylene glycol, acetonitrile represented the best ECOD performance as the extracting solvent. The performance of non-calcined catalyst for sulfur removal was slightly better than that by the calcined one. It was also found that the high sulfur removal activity of the extractive-catalytic oxidative process (ECOD) was retained even at high feed concentration. The kinetic model was evaluated considering mass transfer coupled with chemical reaction, in which the catalytic oxidation reaction was recognized as the rate-controlling step. The kinetic parameters such as rate constants and apparent activation energy were determined.

Thermodynamic optimization of a vacuum multi-effect membrane distillation system for liquid desiccant regeneration

The regenerator is one of the key components in the liquid desiccant air-conditioning system, and improvement of the regenerator performance is key to promoting the overall system energy efficiency. This study entails the investigation of a vacuum multi-effect membrane distillation system (V-MEMD) for liquid desiccant regeneration. The V-MEMD regenerator possesses the merits of high energy efficiency and zero desiccant carry-over. A thermodynamic model has been developed to study the regeneration process based on the principles of heat and mass transfer and heat and mass balances. The model is validated with experimental data, and the discrepancies are observed to be within 10% and 5% for regeneration rate and brine concentration, respectively. Employing the developed and validated model, several V-MEMD configurations have been investigated and the effects of key operating parameters are evaluated. The regenerator performance is observed to degrade at higher feed concentrations, while a higher hot water temperature promotes regeneration rate and thermal efficiency. The proposed configurations expand the operation range of the V-MEMD regenerator to greater than 40 wt% under a heat source temperature of 70 °C. Compared with existing liquid desiccant regeneration systems, the specific energy consumption is reduced by 10–50%.

Modelling and experimental investigation of the adsorption breakthrough behaviors of Pd (II) and Cu (II) by ETA microspheres

AbstractBACKGROUNDEpichlorohydrin/thiourea modified alginate (ETA) microspheres prepared by an emulsion method were used as stationary phase in a fixed‐bed column to selectively adsorb Pd (II) from bi‐metallic solutions. The transport‐dispersive model with a linear driving force kinetics equation and a pH‐dependent competitive Langmuir isotherm was employed to predict the breakthrough curves of the metal ions from the fixed bed.RESULTSGood agreement between the model predictions and the experimental results under different operating conditions confirms the validity and accuracy of the mathematical model and the derived model parameters. Metal ions elute faster from the column with steeper breakthrough curves at higher flow rates and relatively higher feed concentrations. The pH value significantly affects the competitive adsorption isotherm as well as the breakthrough curves. The fully loaded packed bed can be regenerated completely by dilute thiourea solution.CONCLUSIONThe tailor‐made ETA microspheres can be successfully packed in a fixed‐bed column to selectively adsorb Pd (II) from bimetallic solutions. The transport‐dispersive model is capable of predicting the adsorption performances over a wide range of operating conditions. © 2018 Society of Chemical Industry

Predicting Average Molecular Weights and Branching Level for Self‐Condensing Vinyl Copolymerization in a CSTR

AbstractA continuous stirred‐tank reactor (CSTR) model is developed to produce arborescent polyisobutylene via carbocationic copolymerization of isobutylene and inimer using multidimensional method of moments. The model is used to predict dynamic changes in average branching level (Bkin) and number‐average and weight‐average molecular weights (). Simulations of this self‐condensing vinyl copolymerization (SCVCP) show a tendency toward higher polydispersity and higher Bkin compared to batch reactor simulations conducted using the same recipes and residence times. At high inimer feed concentration and/or long residence time, the model predicts that a CSTR does not reach steady‐state operation due to increasing toward infinity. There is a narrow operating range in which inimer feed concentrations can be adjusted to achieve a desired steady‐state . If SCVCP is to be conducted in a CSTR, it will be important to ensure that residence times and inimer feed concentrations are selected within the stable operating window.

Fractional-submerged membrane distillation crystallizer (F-SMDC) for treatment of high salinity solution

Membrane distillation with crystallization (MDC) is an attractive process for high saline seawater reverse osmosis (SWRO) brine treatment. MDC produces additional fresh water while simultaneously recovering valuable resources. This study developed a novel approach of fractional-submerged MDC (F-SMDC) process, in which MD and crystallizer are integrated in a feed tank with a submerged membrane. F-SMDC principle is based on the presence of temperature/concentration gradient (TG/CG) in the feed reactor. The operational conditions at the top portion of the feed reactor (higher temperature and lower feed concentration) was well suited for MD operation, while the bottom portion of the reactor (lower temperature and higher concentration) was favourable for crystal growth. F-SMDC performance with direct contact MD to treat brine and produce sodium sulfate (Na2SO4) crystals using TG/CG showed positive results. The TG/CG approach in F-SMDC enabled to achieve higher water recovery for brine treatment with a volume concentration factor (VCF) of over 3.5 compared to VCF of 2.9 with a conventional S-MDC set-up. Further, the high feed concentration and low temperature at the reactor bottom in F-SMDC enabled the formation of Na2SO4 crystals with narrow crystal size distribution.

Removal of Pb(II) from water using a bio-composite adsorbent-A systematic approach of optimizing synthesis and process parameters by response surface methodology

The synthesis parameters for preparing a novel bio-composite adsorbent by integrating a copolymer of 2-hydroxyethyl methacrylate (HEMA), acrylamide (AM) and crosslinker N, N′-methylene bis acrylamide (MBA), polyethylene glycol (PEG) and Azadirachta Indica or Neem leaf (NL) and the process parameters for its subsequent use for adsorption of Pb(II) ion from water were optimized with central composite design (CCD) of response surface methodology (RSM). The structure of the bio-composite was characterized by FTIR, XRD, TGA, DMA, FESEM-EDX and PZC analysis. The optimized adsorbent prepared with a AM: HEMA molar ratio of 5:1, MBA, PEG and NL wt% of 0.75, 4 and 2.5, respectively showed 182.85 mg/g (92.5%) adsorption of Pb(II) from water containing low concentration of 50 mg/L of Pb(II) ion and 911 mg/L (57%) adsorption of the same metal ion for a high feed concentration of 400 mg/L in a solution pH of 6, adsorbent dose of 0.25 g/L and a feed temperature of 30 °C. This functional bio-composite may also be suitably used for separation of other metal ions and polar molecules from water.

Nanomaterial Endocytosis: Estimation of Particles Per Cell by Magnetic Measurement

We investigated the uptake of superparamagnetic iron oxide nanoparticles (SPIONs) by mammalian cells in monolayer culture by exposing Chinese hamster ovary cells, line CHO-K1 which is frequently used in industrial applications, to Chemicell FluidMagD nanoparticles with diameters of 105 and 150 nm and surface coatings of starch and aminated starch, respectively. The number of particles ingested per cell was determined by measuring the magnetophoretic mobility distributions of treated and untreated cell populations using a Hyperflux magnetic particle tracking velocimeter. Increases in cell volume were evaluated on the basis of cell size data from the Hyperflux velocimeter and used to calculate particles per cell. Starch-coated and positively charged SPIONs were taken up effectively at several concentrations, and these led to quantifiable magnetophoretic mobility and cell volume increases, which, if due to particles only, correspond to several hundred thousand to over one million SPIONs per cell at high SPION feed concentrations. These conclusions are consistent with independent bulk measurements of iron content. Magnetophoretic mobility measurement is a facile and more robust method for measuring SPION uptake.

Highly efficient separation of strongly hydrophilic structurally related compounds by hydrophobic ionic solutions

The selective separation of strongly hydrophilic structurally related compounds in aqueous solutions is a long‐standing challenge due to a trade‐off between separation selectivity and capacity. This work shows a new method to separate strongly hydrophilic structurally related compounds through hydrophobic ionic solution‐based liquid‐liquid extraction, with L‐ascorbic acid 2‐glucoside (AA‐2G) and L‐ascorbic acid as model compounds. Extraordinary distribution coefficient, superb molecular selectivity, large extraction capacity and good recyclability without using strong acids and salts were all achieved, with a small consumption of phosphonium bromide ionic liquid and aprotic molecular diluent. The essence of this method is the successful combination of both strong hydrogen‐bond basicity and good hydrophobicity along with significant preferential solvation phenomena of the constructed ionic solutions. Even if at a high feed concentration of 100 mg/mL, the purity of AA‐2G could be greatly elevated from 50% to 96.2% with an ultrahigh yield of almost 100% after five‐stage countercurrent extraction. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1373–1382, 2018

Combination of adsorption-diffusion model with CFD for study of desulfurization in fixed bed

A 2D porous media Computational Fluid Dynamics (CFD) model is developed for a fixed bed adsorber to remove the 4,6-dimethyldibenzothiophene (4,6-DMDBT) from diesel. The Ag-TiO2-SiO2 modified by CeOx adsorbent is used to remove the 4,6-DMDBT from diesel and proves that CeOx species could promote high dispersion of Ag species on adsorbent surface. The mass source term describing mass transfer of 4,6-DMDBT inside the adsorption bed column is considered. The effects of various parameters such as feed concentration, feed rate and column height on adsorption process have been investigated. Mesh independent test is performed to investigate the effect of the grid size on the simulation results. The component distribution contour and mass transfer rate are employed to analyse further the mass transfer phenomenon in fixed bed column. The higher mass transfer rate at the beginning can be observed and the lower mass transfer rate is obtained after a period of adsorption time at high feed concentration. Results also demonstrate that the porous media CFD model can successfully describe the adsorption of 4,6-DMDBT from diesel in fixed bed column. Finally, the results of Genetic algorithm search suggest that the optimal height of mass transfer zone can be got at low feed rate, high bed height and low feed concentration.

Continuous Total Spontaneous Resolution

We achieved chiral symmetry breaking through continuous crystallizations, which enables the continuous industrial production of chirally pure crystals. For this, a novel recycling platform that mimics a continuous cooling crystallization process with a hot concentrated feed and an outflow of cold suspension was developed and tested. A virtually enantiopure steady-state was realized by seeding a clear supersaturated achiral solution with enantiopure seed crystals at the start of the experiment. Seeding with the enantiopure form ensured that fragments of the seeded form were continuously created through secondary nucleation. Below the metastable zone limit, the product continued to consist of crystals of the same handedness as the seeded form provided that long residence times were applied in combination with sufficiently high feed concentrations. Short residence times in combination with low feed concentrations led to fouling-induced formation of both chiral forms and a decrease in the product’s enantiomer...

Energy consumption and exergy analyses of a supercritical water oxidation system with a transpiring wall reactor

A supercritical water oxidation system with a transpiring wall reactor was simulated by Aspen Plus, and simulation model was validated by comparisons with experimental reactor outlet temperatures and product properties (total organic carbon and CO). Energy and exergy analyses were conducted to reduce energy consumption and exergy loss of the system. It is indicated that the system’s energy efficiency and exergy efficiency are 97.73% and 13.28% at typical operating conditions, respectively. The exergy loss of electric heater, heat exchanger and reactor account for 39.89%, 26.64%, and 17.23% of the system’s total exergy loss, respectively. The process optimization is conducted by preheating the middle branch of transpiring water with the heat of the reaction products to reduce energy consumption, and the net electric cost is reduced from 7.43 ¥/h to 5.96 ¥/h. It can be observed that when the split coefficient for split 2 equals to 0.6, the minimum electricity input is required for the system. When the feed concentration is increased from 2wt.% to 10wt.%, net electric cost per COD significantly decreases from 14.05 ¥/kg to 1.31 ¥/kg, which indicates that higher feed concentrations are beneficial for reducing the cost of energy consumption. What is more, when feed flow rate increases from 6kg/h to 16kg/h, net electric cost per COD increases from 3.21 ¥/kg to 4.61¥/kg, which shows that higher energy consumption costs will be required at higher feed flow rates.

Effect of filtration mode and backwash water on hydraulically irreversible fouling of ultrafiltration membrane

To investigate the effect of filtration mode and backwash water on ultrafiltration (UF) membrane performance, total fouling index (TFI) and hydraulic irreversible fouling index (HIFI) for constant pressure (CP) filtration and constant flux (CF) filtration were compared. Kaolin, humic acid (HA) and sodium alginate (SA) solutions were used as feed solutions, and then the fouled membranes were backwashed with UF permeate or ultrapure water. Results showed that when the kaolin solution was filtrated, the filtration mode had a limited effect on the membrane fouling, and low TFI and HIFI were observed. When HA and SA solutions were filtrated, the TFI of UF under CP mode was comparable to or slightly higher than that under CF mode. Higher TFI was observed at a hydrophobic membrane, a high filtration strength, a high feed concentration, a low pH, a high ionic strength, and a low Ca2+ concentration. When the UF permeate was used as the backwash water, the HIFI for the UF operated under CF mode was significantly less than that under CP mode. Low irreversible fouling was obtained when the ultrapure water was used for backwashing, and the HIFI for the UF under different filtration modes was almost identical.

A Thermodynamical Approach for Evaluating Energy Consumption of the Forward Osmosis Process Using Various Draw Solutes

The forward-osmosis (FO) processes have received much attention in past years as an energy saving desalination process. A typical FO process should inclu de a draw solute recovery step which contributes to the main operation costs of the process. Therefore, investigating the energy consumption is very important for the development and employment of the forward osmosis process. In this work, NH3-CO2, Na2SO4, propylene glycol mono-butyl ether, and dipropylamine were selected as draw solutes. The FO processes of different draw solute recovery approaches were simulated by Aspen PlusTM with a customized FO unit model. The electrolyte Non-Random Two-Liquid (Electrolyte-NRTL) and Universal Quasi Chemical (UNIQUAC) models were employed to calculate the thermodynamic properties of the feed and draw solutions. The simulation results indicated that the FO performance decreased under high feed concentration, while the energy consumption was improved at high draw solution concentration. The FO process using Na2SO4 showed the lowest energy consumption, followed by NH3-CO2, and dipropylamine. The propylene glycol mono-butyl ether process exhibited the highest energy consumption due to its low solubility in water. Finally, in order to compare the equivalent work of the FO processes, the thermal energy requirements were converted to electrical work.

Ultrafiltration membrane for effective removal of chromium ions from potable water

The objective of the present work was to investigate the efficacy of indigenously developed polyacrylonitrile (PAN) based ultrafiltration (UF) membrane for chromium ions removal from potable water. The hydrolyzed PAN membranes effectively rejected chromium anions in the feed ranging from 250 ppb to 400 ppm and a rejection of ≥90% was achieved for pH ≥ 7 at low chromate concentration (≤25 ppm) in feed. The rejection mechanism of chromium ions was strongly dependent on Donnan exclusion principle, while size exclusion principle for UF did not play a major role on ions rejection. Feed pH played a vital role in changing porosity of membrane, which influenced the retention behavior of chromate ions. Cross-flow velocity, pressure did not play significant role for ions rejection at low feed concentration. However, at higher feed concentration (≥400 ppm), concentration polarization became important and it reduced the chromate rejection to 32% at low cross flow and high pressure. Donnan steric-partitioning pore and dielectric exclusion model (DSPM-DE) was applied to evaluate the chromate ions transport through PAN UF membrane as a function of flux by using optimized model parameters and the simulated data matched well with experimental results.

Surface micro-patterning as a promising platform towards novel polyamide thin-film composite membranes of superior performance

Novel and efficient micro-patterned polyamide (PA) thin-film composite (TFC) membranes are successfully fabricated. Polyethersulfone support membranes are micro-patterned using two microfabrication methods, combined processes of vapor- and non-solvent-induced phase separation micro-molding, as well as micro-imprinting lithography. PA layer is successfully adapted on the developed micro-patterned supports and the impact on the membrane performance as a result of the difference in micro-patterning resolution is explored. The patterned PA TFC membranes exhibit superior water permeability, ~2–2.4 times compared to the flat PA TFC membranes, without sacrificing the membrane selectivity. This is mainly due to the distinguishable enhancement in membrane active surface area (~40–70%) and the increasing of the surface roughness upon micro-patterning. Furthermore, the concentration polarization analysis using different membrane orientations, with patterned grooves “parallel” and “perpendicular” to the direction of feed flow, and various feed concentrations is carried out. The results explicit the merits of implementing the micro-patterned TFC membranes in producing specific surface-induced mixing effects, which are found to reduce the concentration polarization, even at a high feed concentration. Moreover, the fidelity of the micro-patterning methods used in this work is comprehensively studied and different mechanisms for membrane surface patterning are proposed.

Performance of submerged anaerobic membrane bioreactor for thermomechanical pulping wastewater treatment

A hollow fiber submerged anaerobic membrane bioreactor (SAnMBR) was operated for 160 days for thermo-mechanical pulping pressate treatment. A COD removal efficiency of 83±4% was achieved under all tested conditions, although the residual COD in permeate increased slightly with an increase in influent COD. The biogas yield slightly decreased with a higher feed concentration. The EPS production increased with an increase in organic loading rate. Membrane performance was affected by both the influent COD concentration and biogas sparging rate. The fouling layer samples were characterized using various analytical tools. The results suggest that it is feasible and attractive to treat thermomechanical pulping wastewater by a hollow fiber SAnMBR. Cake layer formation was the dominant mechanism of membrane fouling. An increase in biogas sparging rate actively mitigated the accumulation and deposition of sludge on/in membrane module, thus favored the enhancement of membrane flux and an efficient long-term operation.

Enhanced biodegradation of phenolic compounds in landfill leachate by enriched nitrifying membrane bioreactor sludge

The role of autotrophic nitrification on the biodegradation of toxic organic micro-pollutants presented in landfill leachate was assessed. A two-stage MBR system consisting of an inclined tube incorporated anoxic reactor followed by aerobic submerged membrane reactor was operated under long sludge age condition in which nitrifying bacteria could be enriched. During the reactor operation, organic removal efficiencies were more than 90% whereas phenolic compounds including bisphenol A (BPA) and 4-methyl-2,6-di-tert-butylphenol (BHT) were removed by 65 and 70% mainly through biodegradation in the aerobic reactor even at high feed concentrations of 1000μg/L for both compounds. Batch experiments revealed that enriched nitrifying sludge with nitrifying activities could biodegraded 88 and 75% of BPA and BHT, largely improved from non-nitrifying sludge and enriched nitrifying sludge with the presence of inhibitor. The first-order kinetic rates of BHT and BPA removal were 0.0108 and 0.096h−1, also enhanced by 44% from the non-nitrifying sludge.