Two-stage Membrane Process Research Articles

Alternate solvent for soybean oil extraction based on extractability and membrane solvent recovery.

Ethyl acetate, acetone, 2-propanol, 1-propanol, and ethanol were screened among the class 3 category solvents as an alternative to hexane based on operational and occupational safety and bio-renewability potential. All five solvents exhibited higher extractability (22.3 to 23.2%) than hexane (21.5%) with soybean flour. Additionally, there was no significant difference in the fatty acid and triacylglycerol (TAG) composition of the oils extracted using alternate solvents and hexane, indicating the oil quality was not affected. More importantly, ethyl acetate (2.1%) resulted in a marginally higher yield of TAG, while 2-propanol showed a nearly equal yield to hexane. Further, membrane desolventizing was attempted to mitigate the limitations of higher thermal energy requirements. One of the polydimethylsiloxane membranes exhibited good selectivity (TAG rejection 85.8%) and acceptable flux (59.3 L·m-2·h-1) with an ethyl acetate miscella system. Under plant-simulated recirculation conditions, a two-stage membrane process reduced the oil content in permeate to 2.5%. The study revealed that ethyl acetate could potentially replace hexane, considering its higher TAG extractability and suitability for the membrane-augmented solvent recycling process in the extraction plants.

Anaerobic digestion of winery solid waste in a two-stage membrane process: Effect of loading rate on biomethane production

The wine industry causes a high amount of solid waste with high organic content at different parts of the production line. One of the best strategies to overcome organic solid waste management problem is anaerobic digestion, as It allows renewable energy production and waste reduction together. The OLR is considered one of the most important operating parameters in continuous or semi-continuous anaerobic operations, as it affects the overall performance of anaerobic digestion systems. Therefore, appropriate OLR determination plays a crucial role in anaerobic digestion. This study investigated the effect of OLR on the performance of a TAnMBR treating (winery solid waste) WSW in terms of biogas and biomethane production. To this end, the production of biogas and biomethane from WSW via a TAnMBR at four different OLRs (0.5 0.75 1.0 1.5 gVS/Lreac d) was investigated. Biogas production rates were 677, 850, 1265, and 566 ml/gVS and biomethane production rates were 352, 450, 679, and 251 ml/gVS respectively, during 0.5 0.75 1.0 1.5 gVS/Lreac d OLR operating conditions. Results revealed that proper biogas and biomethane production can continue until the OLR is 1.5. VFA accumulation can be considered as the main inhibition reason, at 1.5 OLR VFA/Alk ratio increased up to 1.6 with 1864 mgHAc/L VFA concentration. Additionally, phenol and sulfate concentrations were below 45 and 48 mg/L during operation, respectively, therefore it is considered that no inhibition occurred due to these parameters.

Spacial regulation of precise aperture in metal–organic frameworks towards ultrahigh-selective mixed matrix membranes for low-energy-consumption C3H6/C3H8 separation

Membrane technology based on metal–organic framework (MOF) with molecular sieving properties is a promising alternative to energy-intensive conventional distillation for C3H6/C3H8 separation. However, precisely regulating the aperture of MOF materials for industrial separation processes with low energy consumption remains a significant challenge. Herein, we introduce a post-synthetic defect exchange, using ortho-trifluoromethylbenzoic acid (o-TBA) in defective UiO-66, resulting in a mixed matrix membrane (MMM) with a C3H6/C3H8 ideal selectivity of ∼ 104 and C3H6 permeability of ∼ 293 Barrer, and exhibiting a C3H6/C3H8 selectivity ∼ 36 with C3H6 permeability of ∼ 188 Barrer for a C3H6/C3H8 (50:50) mixture. Computational simulations confirm impact of o-TBA-UiO on reducing pore sizes and providing moderate propylene affinity. Static adsorption and solution-diffusion experimental results show that the o-TBA-UiO/6FDA-DAM membrane provides fast C3H6 diffusion rates but retards C3H8 diffusion, leading to ultrahigh C3H6/C3H8 selectivity. A large-area membrane of 2400 cm2 was prepared to promote practical applications, mainly because of the considerably enhanced affinity between o-TBA-UiO and 6FDA-DAM. At a feed pressure of 1 bar, the 1812-type membrane module exhibited a modest decline in single gas separation performance with a C3H6 permeability of ∼ 175 Barrer and a C3H6/C3H8 ideal selectivity of ∼ 96. Finally, a potential two-stage membrane process with low energy consumption was designed. This study provides a robust design for MOF-based MMMs with molecular sieving for energy-efficient gas separation.

High-performance hydrogen separation using cellulose-based carbon molecular sieve membranes

Cellulose-based carbon molecular sieve membranes were designed for hydrogen deblending from natural gas and hydrogen recovery from other relevant industrial sources. The crystallinity of the cellulose precursor was increased by adding propylene glycol, which originated a carbon membrane with a permeability to the hydrogen of 544 barrer and an H2/CH4 permselectivity of ca. 3500 (Robeson index = 100). A careful optimization of the carbonization conditions of the cellulose precursor boosted the carbon membrane permeability to hydrogen to 1144 barrer and the H2/CH4 permselectivity to 1080 (Robeson index = 62). The membrane with the highest permeability to hydrogen presented the highest micropore volume of 0.443 cm3·g−1 and a micropore surface area of 1326 m2·g−1.A detailed techno-economic analysis of the hydrogen recovery from the natural gas was performed. It was concluded that a single-stage carbon membrane module can recover hydrogen with a concentration of 99.8 % and a specific cost of 0.26 €·kgH2−1 for a hydrogen recovery of 68 %. A two-stage membrane process was simulated to deliver a purity >99.997 % and a recovery of 96 %, with a specific cost of 1.8 €·kgH2−1. The carbon membranes prepared in this work are highly competitive with other separation processes for the recovery and purification of hydrogen from different industrial processes essential for the decarbonization.

Two-stage membrane process (UF/NF) for treatment of water process in the steel industry at a pilot scale

Two-stage membrane process (UF/NF) for treatment of water process in the steel industry at a pilot scale

Synchronous Design of Membrane Material and Process for Pre-Combustion CO2 Capture: A Superstructure Method Integrating Membrane Type Selection

Membrane separation technology for CO2 capture in pre-combustion has the advantages of easy operation, minimal land use and no pollution and is considered a reliable alternative to traditional technology. However, previous studies only focused on the H2-selective membrane (HM) or CO2-selective membrane (CM), paying little attention to the combination of different membranes. Therefore, it is hopeful to find the optimal process by considering the potential combination of H2-selective and CO2-selective membranes. For the CO2 capture process in pre-combustion, this paper presents an optimization model based on the superstructure method to determine the best membrane process. In the superstructure model, both CO2-selective and H2-selective commercial membranes are considered. In addition, the changes in optimal membrane performance and capture cost are studied when the selectivity and permeability of membrane change synchronously based on the Robeson upper bound. The results show that when the CO2 purity is 96% and the CO2 recovery rate is 90%, the combination of different membrane types achieves better results. The optimal process is the two-stage membrane process with recycling, using the combination of CM and HM in all situations, which has obvious economic advantages compared with the Selexol process. Under the condition of 96% CO2 purity and 90% CO2 recovery, the CO2 capture cost can be reduced to 11.75$/t CO2 by optimizing the process structure, operating parameters, and performance of membranes.

Analysis and optimal design of membrane processes for flue gas CO2 capture

Membrane separation technology is a potential low-cost flue gas CO2 capture technology to cope with increasing CO2 content in the atmosphere. This paper analyzes the effects of different driving force generation strategies, membrane separation performance and water vapor on operating energy consumption and CO2 capture cost. Then membrane processes are optimized and designed under a wide range of separation requirements. The energy consumption of feed compression combined with permeate vacuum is the lowest when the stage cut is larger than 33.8%, but from the perspective of CO2 capture cost, the vacuum operation is suitable for membranes with high CO2 permeance and moderate selectivity, such as the CO2 permeance above 4000 GPU and the CO2/N2 selectivity below 100, to reduce the investment cost of membrane-related equipment. Since only improving the CO2/N2 selectivity results in an enlarged membrane area and consequently limits the reduction of CO2 capture cost, the development trend of CO2 permeance with increasing CO2/N2 selectivity is proposed to restrain the expansion of membrane area. The water vapor in flue gas can improve the mass transport driving force of CO2 and reduce the membrane area and the capture cost. For water-facilitated membranes, it is recommended to use segmented humidification to replenish the water vapor content of the residue side, especially for the membrane process with a high stage cut, such as the first stage of a two-stage membrane process. Finally, the optimal membrane process and operating pressure under different separation targets, specifically 50–95% dry basis CO2 purity and 50–90% CO2 recovery rate, are obtained by the techno-economic analyses.

Membrane-Assisted Removal of Hydrogen and Nitrogen from Synthetic Natural Gas for Energy-Efficient Liquefaction

Synthetic natural gas (SNG) production from coal is one of the well-matured options to make clean utilization of coal a reality. For the ease of transportation and supply, liquefaction of SNG is highly desirable. In the liquefaction of SNG, efficient removal of low boiling point impurities such as hydrogen (H2) and nitrogen (N2) is highly desirable to lower the power of the liquefaction process. Among several separation processes, membrane-based separation exhibits the potential for the separation of low boiling point impurities at low power consumption as compared to the existing separation processes. In this study, the membrane unit was used to simulate the membrane module by using Aspen HYSYS V10 (Version 10, AspenTech, Bedford, MA, United States). The two-stage and two-step system designs of the N2-selective membrane are utilized for SNG separation. The two-stage membrane process feasibly recovers methane (CH4) at more than 95% (by mol) recovery with a H2 composition of ≤0.05% by mol, but requires a larger membrane area than a two-stage system. While maintaining the minimum internal temperature approach value of 3 °C inside a cryogenic heat exchanger, the optimization of the SNG liquefaction process shows a large reduction in power consumption. Membrane-assisted removal of H2 and N2 for the liquefaction process exhibits the beneficial removal of H2 before liquefaction by achieving low net specific power at 0.4010 kW·h/kg·CH4.

Unobstructed Ultrathin Gas Transport Channels in Composite Membranes by Interfacial Self-Assembly.

Ultrathin unobstructed gas transport channels through the membrane selective layer are constructed in mixed matrix membranes (MMMs) by using gravity-induced interface self-assembly of poly(vinylamine) and polymer-modified MIL-101(Cr). For CO2 /N2 (15/85 by volume) mixed gas, the MMMs achieve a high CO2 permeance of 823 gas permeation units and CO2 /N2 selectivity of 242 at 0.5 MPa. Based on economic analyses, a two-stage membrane process can achieve gas separation and economic targets.

Long-term performance and economic evaluation of full-scale MF and RO process – A case study of the changi NEWater Project Phase 2 in Singapore

The Changi NEWater Project Phase 2 purifies the secondary effluent of an urban sewage treatment plant using a two-stage microfiltration membrane (MF) and reverse osmosis (RO) process to produce NEWater for industrial use and to supplement drinking water sources. The total recovery rate of the system was 73.5%. The turbidity removal rate of the MF unit was 93.4% and the silt density index (SDI) value of MF product water was stable below 3. The performance of the pretreatment unit met the design standards. After reverse osmosis treatment, the total organic carbon removal rate was 99.4% and the desalination rate was greater than 99%. The quality of the NEWater was superior to the drinking-water standards of Singapore and the World Health Organization. Because of its advanced automatic control system, the Changi NEWater Project Phase 2 required a staff of only 15 operation and management personnel. The total operational cost was between 0.08 and 0.15 $/m³, of which energy consumption, chemical consumption, maintenance costs, and labor costs accounted for 62.9%, 20.2%, 7.3% and 9.6%, respectively. The energy consumption was between 0.6 and 0.8 ​kWh/m³. The Changi NEWater Project Phase 2 represents a milestone in water cycle engineering practice because of its excellent process design, superior product water quality, high degree of automatic control, and low operational energy consumption.

Treatment of highly sour natural gas stream by hybrid membrane-amine process: Techno-economic study

This paper summarizes a techno-economic study to treat a highly sour natural gas (NG) beyond conventionally known to classical treatment processes, utilizing hybrid membrane-amine process. Stand-alone amine process utilizing Diglycolamine (DGA) as an absorption reagent, is used as a benchmark for comparison with the hybridized membrane-amine treatment process. A one-stage membrane process with performance factors that are similar to the commercially abundant material, distinguished as reference membrane (RM), is used to benchmark the membrane process. The membrane process performance have been varied in two levels: (i) using a membrane with enhanced (doubled) performance factors, distinguished as (EM), and (ii) deploying a two-stage membrane process configuration. The impact of the membrane process has proved to be substantial and extended beyond the amine process to the sulfur recovery unit (SRU). All processes showed to be economic with clear role of the membrane process in altering the contribution of the different elements of the capital investment cost (CAPEX) and the operating cost (OPEX). The two stage membrane process is more appealing to the operation of the gas plant for the low slippage of hydrocarbons. However, the need for the inter-stage compression caused the hybridized two-stage membrane-amine process with (RM) membrane to be less feasible than the stand-alone amine process. Enhancing the membrane performance factors will produce a treatment process that is more feasible than the amine stand-alone. This study showed that the feasibility of the treatment process of such highly sour NG stream is very sensitive to both energy price (sales gas) and the cost associated with the production of sour raw gas.

Design of Amine-Containing CO2-Selective Membrane Process for Carbon Capture from Flue Gas

A two-stage membrane process featuring a partial retentate recycling is designed for using amine-containing facilitated transport membranes to decarbonize flue gases from pulverized coal power plan...

Integrated Coagulation-Membrane Processes with Zero Liquid Discharge (ZLD) Configuration for the Treatment of Oil Sands Produced Water

This study explores the feasibility of implementing five hybrid coagulation-membrane processes for the treatment of the boiler blow-down (BBD) water from an oil sands steam assisted gravity drainage (SAGD) operation. The processes involved (1) direct nanofiltration (NF) of the BBD water, (2) pre-treatment of the NF retentate using ion exchanger regeneration wastewater (IERW) as a chemical coagulant followed by NF, (3) pre-treatment of BBD water using IERW followed by NF, (4) dual pre-treatment of BBD water using IERW and soda ash (sodium carbonate, Na2CO3) followed by NF, and (5) forward osmosis (FO) treatment of the BBD water using IERW as a draw solution followed by NF treatment of diluted draw solution. These scenarios were compared based on total flux decline ratio (DRt), flux recovery ratio (FRR), and total dissolved solids (TDS) removal over the final NF treatment to suggest an efficient treatment technique to avoid an undesired increase in the capital and operating expenses. It was found that process-1 provided the highest selectivity toward dissolved solids (80%) with a flux decline and recovery ration of 89.6% and 97.4%, respectively. Considering the permeation flux, process-4 exhibited the lowest flux decline (86.1%) and highest recovery ratio (97.5%) compared to other processes, proving the successful role of soda ash softening, as a chemical pretreatment method, in improving the performance of membrane filtration. Process-2 presented a mediocre performance with DRt, FRR, and TDS rejection of 93.3%, 97.3%, and 74%, respectively. Finally, process-3 and process-5 showed the lowest performance among all the scenarios with low flux recovery and low permeability, respectively. In addition, process-3 was expected to be cost-efficient since it only uses an on-site generated waste as a coagulant for the chemical pretreatment of the membrane filtration unit. The optimum scenario was proposed to be the two-stage membrane process, with direct NF of BBD followed by the post-treatment of the retentate via a hybrid chemical conditioning using IERW and soda ash softening, followed by a second NF. Overall, this integrated process offered a highly efficient mean with a zero liquid discharge (ZLD) system for the treatment of high pH wastewaters into an uncontaminated stream for the boilers.

Post-combustion CO2 capture with membrane process: Practical membrane performance and appropriate pressure

Membrane separation process is one of the most promising methods for post-combustion CO2 capture from coal-fired power plant. In this paper, a multicomponent gas separation process using spiral-wound membrane modules is explored to optimize its membrane area and energy consumption. Firstly, the parametric analysis is conducted for the single-stage membrane process to study the impact of the feed gas CO2 concentration, feed pressure and selectivity on the permeate gas flow rate, permeate gas CO2 concentration and membrane area. Secondly, a feasible procedure that maintains product purity and recovery is applied to discuss the impact of the membrane selectivity, permeance and the feed pressure on the two-stage membrane process. Based on the analysis and conclusions in the single-stage membrane process, the trade-off between membrane area and energy consumption has been analyzed in detail. By varying the selectivity and the feed pressure, the impact of these two parameters on the membrane area and energy consumption is discussed, finding that the combination of low selectivity in the first stage and high selectivity in the second stage has much smaller membrane area and slightly higher energy consumption than that of high selectivity in both stages. Moderate feed pressure, varying from 0.55 MPa to 0.65 MPa, is found to provide relatively low CO2 capture energy consumption. Techno-economic analysis is conducted to further validate the above strategy. To minimize the CO2 capture cost, high CO2 permeance and moderate selectivity is desirable for the first stage, while high selectivity and moderate CO2 permeance should be maintained for the second stage. The membrane developed for the flue gas CO2 capture do not have to simultaneously enhance the CO2/N2 selectivity and CO2 permeance. Even considering the uncertainties related to economic parameters, the optimum feed pressure that provides the minimum CO2 capture cost only varies from 0.69 MPa to 0.83 MPa.

Process Simulation and Cost Evaluation of Carbon Membranes for CO₂ Removal from High-Pressure Natural Gas.

Natural gas sweetening is required to remove the acid gas CO2 to meet gas grid specifications. Membrane technology has a great potential in this application compared to the state-of-the-art amine absorption technology. Carbon membranes are of particular interest due to their high CO2/CH4 selectivity of over 100. In order to document the advantages of carbon membranes for natural gas (NG) sweetening, HYSYS simulation and cost evaluation were conducted in this work. A two-stage carbon membrane process with recycling in the second stage was found to be technically feasible to achieve >98% CH4 with <2% CH4 loss. The specific natural gas processing cost of 1.122 × 10−2 $/m3 sweet NG was estimated at a feed pressure of 90 bar, which was significantly dependent on the capital-related cost. Future work on improving carbon membrane performance is required to increase the competitiveness of carbon membranes for natural gas sweetening.

Evaluation of polyphenolic compounds in membrane concentrated pistachio hull extract.

Pistachio hull is a substantial source of natural polyphenols, but a substantial volume is being wasted annually. Aqueous pistachio green hull extract (PGHE) was subjected to two-stage membrane process in order to separate a polyphenol rich fraction. The membrane conditions of each stage were investigated. Total phenolic content and antioxidant activity were determined by Folin-Ciocalteu and DPPH· assay; also membrane fouling was monitored. The use of the 1 kDa cellulose membrane accompanied by 4 bar pressure and 250 rpm stirring speed was observed to be successful in the separation of a fraction with the highest amount of phenolic compound and antioxidant activity, in the retentate part. UHPLC/MSn characterization of PGHE polyphenols enabled us to identify 34 compounds, including the most abundant galloylshikimic acids, gallic acid, theogallin, galloyl-O-hexoside, quercetin-O-hexoside and pyrogallol.

Integration of multi-stage membrane carbon capture processes to coal-fired power plants using highly permeable polymers

Membrane separation systems could be a feasible option as post combustion carbon capture technologies in coal-fired power plants. Recent advancement on membrane materials based on microporous super glassy polymers could improve significantly the capture process but the properties of the materials have to guide the design of the separation stage. In this study an advanced hybrid two-stage membrane process employing one of the most permeable polymer known (PIM-1) is retrofitted to a coal fired power plant and the process is analysed in terms of energy requirement and cost performance. The results are based on the use of an in-house detailed membrane module model implemented in UniSim Design®, the Honeywell process flowsheet simulator. The study indicates the need for advanced configuration in order for highly permeable membranes to be competitive with more mature technologies in terms of capture cost. The effect of ageing and impurities on the material is also investigated in order to predict the decline in process performance over time and suggest a timeproof design.

Monophenols separation from monosaccharides and acids by two-stage nanofiltration and reverse osmosis in hydrothermal liquefaction hydrolysates

Through hydrothermal liquefaction (HTL), lignocellulosic biomass is directly hydrolyzed into small organics like monosaccharides, monophenols and acids, which can be used as valuable chemicals by further purification. This study aims at investigating the feasibility of simultaneous separation of monophenols from sugar and acids in model lignocellulosic hydrolysate solution through two-stage nanofiltration (NF) and reverse osmosis (RO) process. The effects of pressure, temperature and pH on the solute retentions and permeate flux were examined with an eight-solute sugar-monophenols-acids model solution. NF-RO (DK-SE) two-stage membrane process was performed to confirm the multistage separation performance of model hydrolysates under an optimal operation condition. Results showed that membranes with higher water permeability had better performance in separation of sugar from monophenols. The decrease in temperature promoted separation of both acetic acid and monophenols from sugar, while higher pressure and lower temperature favored separation of acetic acid from phenols. The pH should be kept at low values to maintain good monophenols simultaneous separation of from sugar and acids. The maximum separation factors of acetic acid over 2,6-dimethoxyphenol and 2,6-dimethoxyphenol over glucose were 99.59 by RO membrane SE and 29.99 by NF membrane DK, respectively. Two-stage membrane process (DK NF+SE RO) was proven to be a feasible way to fractionate model HTL hydrolysates into three parts: incomplete hydrolyzed biomass fragments, monophenols riched concentrate, and acetic acid permeate.

Two-Stage Membrane System for Post-combustion CO2 Capture Application

This work evaluates the viability of a two-stage process using combined nitrogen (N2)-selective and carbon dioxide (CO2)-selective membranes for post-combustion CO2 capture. A novel type of cellulose acetate (CA) hybrid membrane is used here as a N2-selective membrane. The silica functionalized with p-tetranitrocalix[4]arene (Si–CL) was incorporated into the CA matrix, thereby resulting in a CA/Si–CL hybrid membrane. Moreover, the published permeation data of a CO2-selective fixed-site-carrier (FSC) membrane, i.e., polyvinylamine (PVAm) casted on porous polysulfone (PSf), is used here in a simulation study to serve as a second stage membrane. Although experimental work on the CA/Si–CL hybrid membrane is in progress based on the assumptions of initial appreciable results, a two-stage membrane process is proposed in which a N2-selective membrane is placed in the first stage, while a CO2-selective membrane is placed in the second stage. Subsequently, the techno-economic analysis of a two-stage membrane proce...

An experimental and modeling study of CO2-selective membranes for IGCC syngas purification

In recent years, integrated gasification combined cycle (IGCC) technology has gained significant attention for large-scale power generation with carbon capture. In an IGCC power plant, the syngas is typically directed to the gas turbine (for power generation) after CO2 and H2S removal. This work describes the transport properties of the CO2-selective polymeric facilitated transport membranes for syngas purification at different pressures (2–15bar) and 107°C. These membranes contain amines as CO2-carriers that are dispersed in a crosslinked polyvinylalcohol (PVA) matrix. Furthermore, a two-stage membrane process is proposed for CO2 removal from syngas in an IGCC plant. A process modeling and cost-sensitivity analysis of the proposed two-stage membrane process was performed. The effects of feed pressure, temperature, membrane permeance, and selectivity on the overall increase in the cost of electricity (COE) were analyzed. An increase in the COE of 14–18% was estimated for 90% CO2 removal and >99% H2 recovery using the two-stage membrane process in an IGCC power plant.