Hollow Fiber Membrane Contactor Research Articles

Intensification of CO2 absorption using MDEA-based nanofluid in a hollow fibre membrane contactor

Porous hollow fibres made of polyvinylidene fluoride were employed as membrane contactor for carbon dioxide (CO2) absorption in a gas–liquid mode with methyldiethanolamine (MDEA) based nanofluid absorbent. Both theoretical and experimental works were carried out in which a mechanistic model was developed that considers the mass transfer of components in all subdomains of the contactor module. Also, the model considers convectional mass transfer in shell and tube subdomains with the chemical reaction as well as Grazing and Brownian motion of nanoparticles effects. The predicted outputs of the developed model and simulations showed that the dispersion of CNT nanoparticles to MDEA-based solvent improves CO2 capture percentage compared to the pure solvent. In addition, the efficiency of CO2 capture for MDEA-based nanofluid was increased with rising MDEA content, liquid flow rate and membrane porosity. On the other hand, the enhancement of gas velocity and the membrane tortuosity led to reduced CO2 capture efficiency in the module. Moreover, it was revealed that the CNT nanoparticles effect on CO2 removal is higher in the presence of lower MDEA concentration (5%) in the solvent. The model was validated by comparing with the experimental data, and great agreement was obtained.

Regeneration of CO2 absorbent with membrane contactor via pressure swing

A new method to regenerate high pressure CO2 absorbent is presented in this paper, where PTFE hollow fiber membrane contactor was used as a gas–liquid separator in pressure swing process. CO2 desorption happened in the membrane contactor at the same time. The two mass transfer mechanisms were analysed through calculation of viscous flux and mass transfer coefficients. Experimental results showed that CO2 loading in regenerated absorbent increased with absorbent flow rate. This was due to decrease in membrane area available for CO2 desorption, as most of the membrane area was utilized for gas-liquid separation. Co-current configuration exhibited higher CO2 desorption driving force compared to counter-current configuration, hence its CO2 loading in regenerated absorbent was lower. When integrated with membrane contactor for CO2 absorption, stable and consistent performance was observed. Unlike conventional flash drum, membrane contactor did not have requirement on flashed gas velocity, because the membrane itself functioned as a screen to prevent fine liquid droplets from escaping the system along with flashed gas. Results from this study show that vessel size reduction up to 2.5 times could be achieved when PTFE membrane contactor was used, with absorbent regeneration energy as low as 0.94 GJ/ton CO2.

Demonstrating Commercial Hollow Fibre Membrane Contactor Performance at Industrial Scale for Biogas Upgrading at a Sewage Treatment Works

Hollow fibre membrane contactor (HFMC) technology has been developed for CO2 absorption primarily using synthetic gas, which neglects the critical impact that trace contaminants might have on separation efficiency and robustness in industrial gases. This study, therefore, commissioned a demonstration-scale HFMC for CO2 separation at a full-scale anaerobic digester facility to evaluate membrane integrity over six months of operation on real biogas. The CO2 capture efficiency identified using real biogas was benchmarked at comparable conditions on synthetic gas of an equivalent partial pressure, and an equivalent performance identified. Two HFMC were subsequently compared, one with and one without a pre-treatment stage that targeted particulates, volatile organic compounds (VOCs) and humidity. Similar CO2 separation efficiency was again demonstrated, indicating limited impact within the timescale evaluated. However, gas phase pre-treatment is advised in order to ensure robustness in the long term. Over longer-term operation, a decline in CO2 separation efficiency was observed. Membrane autopsy identified shell-side deposition, where the structural morphology and confirmation of amide I and II groups, indicated biofouling. Separation efficiency was reinstated via chemical cleaning, which demonstrated that proactive maintenance could minimise process risk.

Ammonia capture from human urine to harvest liquid N-P compound fertilizer by a submerged hollow fiber membrane contactor: Performance and fertilizer analysis

In this study, we developed a submerged hollow fiber membrane contactor (HFMC) to recover ammonia from human urine to get compound N-P fertilizers. The ammonia capture performance, water vapor transmembrane performance, ion rejection performance and the liquid fertilizer components using 1–4 mol/L H3PO4 as the stripping solution was comprehensively investigated. Increasing H3PO4 concentration did not significantly affect the ammonia capture performance but the water vapor transfer and fertilizer components. The ammonia mass transfer coefficients were in a range of 1.95×10−6±4.77×10−8 to 2.28×10−6±6.71×10−8 m/s and the ammonia flux fluctuated between 17.80 and 20.80 g/m2·h. The water vapor flux increased with the increase of stripping solution concentration and the time elapsed. The N content (21.29–55.24 g/L) was in the range of the commercial products while the P2O5 content (99.41–281 g/L) was slightly higher, which can be used in the soils or plants with a high demand for phosphorus. The liquid fertilizers were all mixtures of (NH4)2HPO4 and NH4H2PO4, but the distribution ratio slightly changed with the different initial H3PO4 concentration. The economic assessment showed that harvesting liquid N-P fertilizer from human urine using HFMC can make a profit of $7.089/L.

Selective Sulfur Dioxide Absorption from Simulated Flue Gas Using Various Aqueous Alkali Solutions in a Polypropylene Hollow Fiber Membrane Contactor: Removal Efficiency and Use of Sulfur Dioxide.

Hollow fiber membrane contactors (HFMCs) provide a large specific surface area. Thus, their significantly reduced volume provides an advantage compared to the conventional gas–liquid contactor. In this study, the selective removal efficiency of flue gas, in which sulfur oxide (SO2) and carbon dioxide (CO2) coexist, was measured using a polypropylene (PP) HFMC with such advantages. To increase the selective removal efficiency of SO2, experiments were conducted using various alkaline absorbents. As a result, with 0.05 M ammonia solution, the removal efficiency of 95% or more was exhibited with continuous operation for 100 h or more. We confirmed that the absorbent saturated by the once-through mode was aqueous ammonium sulfate ((NH4)2SO4) solution and could be used as a fertilizer without additional processing.

The enhancement of ozone-liquid mass transfer performance in a PTFE hollow fiber membrane contactor using ultrasound as a catalyzer.

A comprehensive assessment of a polytetrafluoroethylene (PTFE) hollow fiber membrane contactor and ultrasound for intensifying ozone–liquid mass transfer was conducted simultaneously. The initial part of the study concentrates on the systematic analysis of the previous literature related to the reinforcement on the ozone–liquid mass transfer. In this paper, the introduction of a membrane contactor and ultrasound as a catalyzer that increased the mass transfer coefficient (KLa) may be partially attributed to the increase of the net surface area and the decrease of the mass transfer resistance, thus leading to the enhancement of the ozone mass transfer rate and acceleration of the ozone decomposition in solution. Results revealed that the maximum value of the KLa value was 0.7858 min−1 in the PTFE hollow fiber membrane contactor in the presence of the ultrasound, while only 0.5154 min−1 in a single ozone aeration at an intake flow of 300 L h−1, ozone dosage of 32.38 mg L−1 and operating temperature of 293.15 K. A 52.46% improvement of the KLa value was obtained in the presence of the ultrasound. In addition, the dosage of sodium chloride appeared to have a positive correlation with KLa, but a negative correlation with the concentration of dissolved ozone. The sulfolane destruction by ozonation, ultrasound and the combination between the ozonation and ultrasound were performed to further verify the enhancement of the ozone mass transfer performance. It has been established that the O3/US combined process was a promising method, giving the maximum degradation of sulfolane (96.5%) with the synergistic index as 2.41.

Maximising resource recovery from wastewater grown microalgae and primary sludge in an anaerobic membrane co-digestion pilot plant coupled to a composting process

A pilot-scale microalgae (Chlorella spp.) and primary sludge anaerobic co-digestion (ACoD) plant was run for one year in an anaerobic membrane bioreactor (AnMBR) at 35 °C, 70 d solids retention time and 30 d hydraulic retention time, showing high stability in terms of pH and VFA concentration. The plant achieved a high degree of microalgae and primary sludge substrate degradation, resulting in a methane yield of 370 mLCH4·gVSinf−1. Nutrient-rich effluent streams (685 mgN·L−1 and 145 mgP·L−1 in digestate and 395 mgNH4-N·L−1 and 37 mgPO4-P·L−1 in permeate) were obtained, allowing posterior nutrient recovery. Ammonium was recovered from the permeate as ammonia sulphate through a hydrophobic polypropylene hollow fibre membrane contactor, achieving 99% nitrogen recovery efficiency. However, phosphorus recovery through processes such as struvite precipitation was not applied since only 26% of the phosphate was available in the effluent. Composting process of the digestate coming from the ACoD pilot plant was assessed on laboratory-scale Dewar reactors, as was the conventional sludge compost from an industrial WWTP digestion process, obtaining similar values from both. Sanitised (free of Escherichia coli and Salmonella spp.) and stable compost (respirometric index at 37 °C below 0.5 mgO 2 g organic matter−1·h−1) was obtained from both sludges.

Hollow Fiber Membrane Contactors in CO2 Desorption: A Review

This work was funded by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO), Project CTQ2016-76231-C2-(AEI/FEDER, UE) and Project PID2019-108136RB-C31). J.M.V. thanks the Concepcion Arenal postgraduate research grant from the University of Cantabria.

Study of intrinsic oxygen mass transfer characteristic and model on polypropylene hollow fiber membrane contactor

The oxygen mass transfer characteristics of a membrane contactor with a hydrophobic polypropylene hollow fiber membrane are experimentally studied herein. The examination focuses on influences of oxygen intake pressure (0.12, 0.13, and 0.14 MPa) and water flux (from 100 L/h to 320 L/h) on oxygen mass transfer coefficient. Experimental results indicate that the inflection point of oxygen mass transfer coefficient shows up when water flux increases under specific intake gas pressures. The mass transfer coefficient goes up remarkably along with rise of oxygen intake pressure. A novel mass transfer model based on the concept of the liquid film renewal time (△tj) and the solubility equilibrium time (△t⁎) is proposed. In this model, the total mass transfer rate is influenced both by liquid film renewal rate between fluid bulk region and liquid film at the gas–liquid interface, and by oxygen diffusion rate in the twice interface renewal process. The model interprets the experimental mass transfer phenomena well.

Hollow Fiber Membrane Contactors for Post-Combustion Carbon Capture: A Review of Modeling Approaches.

Hollow fiber membrane contactors (HFMCs) can effectively separate CO from post-combustion flue gas by providing a high contact surface area between the flue gas and a liquid solvent. Accurate models of carbon capture HFMCs are necessary to understand the underlying transport processes and optimize HFMC designs. There are various methods for modeling HFMCs in 1D, 2D, or 3D. These methods include (but are not limited to): resistance-in-series, solution-diffusion, pore flow, Happel’s free surface model, and porous media modeling. This review paper discusses the state-of-the-art methods for modeling carbon capture HFMCs in 1D, 2D, and 3D. State-of-the-art 1D, 2D, and 3D carbon capture HFMC models are then compared in depth, based on their underlying assumptions. Numerical methods are also discussed, along with modeling to scale up HFMCs from the lab scale to the commercial scale.

Research Progress in Gas Separation Using Hollow Fiber Membrane Contactors.

In recent years, gas–liquid membrane contactors have attracted increasing attention. A membrane contactor is a device that realizes gas–liquid or liquid–liquid mass transfer without being dispersed in another phase. The membrane gas absorption method combines the advantages of chemical absorption and membrane separation, in addition to exhibiting high selectivity, modularity, and compactness. This paper introduces the operating principle and wetting mechanism of hollow membrane contactors, shows the latest research progress of membrane contactors in gas separation, especially for the removal of carbon dioxide from gas mixtures by membrane contactors, and summarizes the main aspects of membrane materials, absorbents, and membrane contactor structures. Furthermore, recommendations are provided for the existing deficiencies or unsolved problems (such as membrane wetting), and the status and progress of membrane contactors are discussed.

Mathematical modeling of CO2 separation using different diameter hollow fiber membranes

This research presents a 2D mass-transfer simulation model using computational fluid dynamics (CFD) for separation of CO2 from a binary gas mixture of CO2/CH4 by means of polytetrafluoroethylene (PTFE) hollow fiber membrane contactor (HFMC). Governing equations with their corresponding boundary conditions are solved using COMSOL Multiphysics and the results are validated against reported experimental data. Convection and diffusion flux vectors and concentration gradient of CO2 species in the radial and axial directions of the HFMC are investigated. This study provides an opportunity to investigate the effects of gas and liquid cross flow velocities on the overall performance of membrane contacting system. The results demonstrate that increasing the liquid phase velocity improves the CO2 absorption performance of the membrane system, while increasing the gas mixture velocity deteriorates the CO2 separation of the system. The impact of hollow fiber geometry on the removal of CO2 is investigated and the results indicate that hollow fibers with smaller inner diameter provides higher effective mass-transfer area and therefore superior CO2 removal performance. Furthermore, the modeling predictions for the CO2 removal are in good agreement with the experimental data under various ratios of gas to liquid velocity. The PTFE hollow fiber membrane contacting system showed a great potential for separation of CO2 from gas mixtures.

Numerical Investigation on the Effect of Flow Parameters in CO2 Capturing Using Aqueous MEA Absorbent in HFMC Systems

Nowadays, CO2 as the product of fossil fuel combustions, is polluting the air and the human environment, and it causes global warming. To reduce the negative effect of CO2 presence, it should be removed from the air by capturing methods. Hollow fiber membrane contactor (HFMC) system is one of the most efficient method for CO2 capturing than the other feasible capturing methods. In the present paper an HFMC absorbing system has been simulated using COMSOL Multiphysics software and the effect of flow rates of gas and liquid on the amount of CO2 removal has been studied. Aqueous solution of Mono-ethanolamine (MEA) is entered as the absorbent liquid in the tubes, and CO2 is removed from the shell side by the diffusion phenomena by participating in the chemical reaction with MEA. The results show that the higher liquid flow rate the higher %CO2 removal from the inserted gas. Against this result, the percentage of CO2 removal decreases with increasing the gas flow rate as expected. Higher gas flow rate leads the gas velocity to higher values and less possibility of absorbing by the diffusion method. The rate of the CO2 removal variation with liquid flow rate is higher than the CO2 removal variation whit the gas flow rate.

Recent developments in membrane technology for the elimination of ammonia from wastewater: A review

This review article presents an extensive study on ammonia elimination from wastewater through membrane separation technology. The mechanism, performance and morphology of different types of membranes that have been employed for ammonia removal from wastewater such as hollow fiber membrane contactor, membrane distillation contactor and flat sheet membranes including blend, and mixed matrix membranes were analyzed. The impact of various variables, for example feed solution pH, concentration of ammonia in the feed solution, operation temperature, membrane thickness, the feed velocity and striping phase velocity on ammonia removal performance of membranes, was evaluated. To summarize the experimental studies, the best performance of membranes reported in the articles was compared and the future perspective of ammonia removal by membrane technology was reported.

CFD Modeling of CO2 Absorption in Membrane Contactors Using Aqueous Solutions of Monoethanolamine–Ionic Liquids

The effects of addition of an ionic liquid to pure water as a physical absorbent and monoethanolamine (MEA) solutions as a chemical absorbent on carbon dioxide (CO2) absorption through hollow fiber membrane contactors were investigated using a 2D axisymmetric model. A numerical simulation was developed based on finite element method using computational fluid dynamics techniques. Liquid phase flowed in the tube side and gas mixture containing CO2 passed in the shell side of the membrane contactor in co-current and countercurrent modes. The simulation results are consistent with experimental data, and the root-mean-square error was calculated as 9 and 13% for pure water and 25 wt % for ionic liquid solution. The results showed that addition of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) to the base fluids increases CO2 absorption in both physical and chemical absorbents. However, the effects of an ionic liquid in physical absorption is higher than that in chemical absorption. Addition of 10 wt % [Bmim][BF4] to 3.5 wt % MEA solution could increase the absorption rate by 12% in countercurrent flow compared to a 6 wt % MEA solution without [Bmim][BF4] despite lower MEA concentration. Also, the results indicate that reaction term in a chemical absorbent is more important in low liquid flow rates. It can also be found that addition of 25 and 50 wt % of [Bmim][BF4] to pure water can enhance absorption performance up to 30 and 75%.

CO2 Desorption Performance from Imidazolium Ionic Liquids by Membrane Vacuum Regeneration Technology.

In this work, the membrane vacuum regeneration (MVR) process was considered as a promising technology for solvent regeneration in post-combustion CO2 capture and utilization (CCU) since high purity CO2 is needed for a technical valorization approach. First, a desorption test by MVR using polypropylene hollow fiber membrane contactor (PP-HFMC) was carried out in order to evaluate the behavior of physical and physico-chemical absorbents in terms of CO2 solubility and regeneration efficiency. The ionic liquid 1-ethyl-3-methylimidazolium acetate, [emim][Ac], was presented as a suitable alternative to conventional amine-based absorbents. Then, a rigorous two-dimensional mathematical model of the MVR process in a HFMC was developed based on a pseudo-steady-state to understand the influence of the solvent regeneration process in the absorption–desorption process. CO2 absorption–desorption experiments in PP-HFMC at different operating conditions for desorption, varying vacuum pressure and temperature, were used for model validation. Results showed that MVR efficiency increased from 3% at room temperature and 500 mbar to 95% at 310 K and 40 mbar vacuum. Moreover, model deviation studies were carried out using sensitivity analysis of Henry’s constant and pre-exponential factor of chemical interaction, thus as to contribute to the knowledge in further works.

Water deoxygenation using a hollow fiber membrane contactor to prevent pipe corrosion for sustainable management of district heating systems: A pilot-scale study

Dissolved oxygen (DO) is a key factor affecting pipe corrosion in district heating systems (DHS). This study demonstrated effective deoxygenation of water in a DHS using a hollow fiber membrane contactor (HFMC) via systematic investigation from lab-to pilot-scale. First, deoxygenation efficiency was evaluated in a lab-scale HFMC with varying operating parameters including an effective membrane area, flow rate and feedwater temperature. Based on the results from the lab-scale investigation, a pilot HFMC system was designed with capacity of 1 m3 per day. To achieve a permeate DO concentration below 10 μg L−1 at feedwater temperatures of 20–60 °C, the vacuum degree needed to be lower than the saturated water vapor pressure of 10–120 Torr. In addition, the primary foulant for membrane fouling was organic matter in the make-up and district heating (DH) return water. A significant change in corrosion response was observed for pipe steel in the DHS after deoxygenation. Immersion tests for 14 days indicated that weight loss values had greatly reduced by the deoxygenation process from 39.3 to 1.3 mg cm−2 and from 21.9 to 2.1 mg cm−2 for steel pipe samples immersed in the make-up water and the DH return water of the DHS, respectively. This improved corrosion resistance from deoxygenation was interpreted by electrochemical analysis. As such, this study offers a pilot-scale demonstration of the feasibility of a hollow fiber membrane-based deoxygenation process as an effective tool to prevent the corrosion of steel pipes.

Rigorous non-isothermal modeling approach for mass and energy transport during CO2 absorption into aqueous solution of amino acid ionic liquids in hollow fiber membrane contactors

In the current study, a rigorous modeling approach was used to develop a mathematical model for the non-isothermal absorption process of CO2 in hollow fiber membrane contactors (HFMC). Four amino acid-based ionic liquids (ILs) namely, tetramethylammonium glycinate [N1111][Gly], 1-ethyl-3-methylimidazolium glycinate [C2mim][Gly], 1-butyl-3-methylimidazolium glycinate [C4mim][Gly] and 1-hexyl-3-methylimidazolium glycinate [C₆mim][Gly] were used as absorbents. These ILs have never been implemented for the membrane contactor CO2 absorption operations both on the lab scale and industrial scale. Wide ranges of operating conditions were investigated for freshly unloaded absorbents and partial conversion of absorbents considering steady-state conditions for the model. Non-wetting conditions were adopted by keeping very low transmembrane pressure. The non-isothermal model predicted a significant temperature rise along the contactor length, ranging from 10 to 25 K, which further affected the absorption and reaction kinetics. Simulations confirmed the strong influence of absorbent concentration and mild influence of process temperature on the separation performance of ILs, CO2 boundary flux, and reaction kinetics between CO2 and ILs. Very fast absorption of CO2 near the interface justified the dominancy of the chemisorption for the current absorption. Finally, the comparison with experimental data evidenced the identical trends and hence validated the model.

Teflon AF2400 Hollow Fiber Membrane Contactor for Dissolved Gas-in-Oil Extraction: Mass Transfer Characteristics

Ceramic-supported Teflon AF2400 hollow fiber membrane contactors for dissolved gas-in-oil extraction has gained importance in online dissolved gas analysis (DGA) monitoring. An improved understandi...

Computational fluid dynamics modeling of ibuprofen removal using a hollow fiber membrane contactor

AbstractIn this study, modeling and simulation of removing a common pharmaceutical contaminant by a hollow fiber membrane contactor (HFMC) were carried out. For this purpose, a model was presented for separation of ibuprofen from wastewater in the membrane contactor. The suggested model was developed by coupling the mass and momentum equations. The partial differential equations (PDEs) and the corresponding boundary conditions of the model were solved using the computational fluid dynamics (CFD) techniques. The results showed that the predictions of this model were in close agreement with experimental data obtained from the literature. Moreover, the effects of different design and operating parameters on the removal of ibuprofen were studied. The simulation results revealed that the removal of ibuprofen was increased by increasing the membrane porosity and the length of fibers. The ibuprofen removal efficiency was also enhanced up to 93.2 and 90.2% by increasing the inner radius and the number of fibers from 110 to 145 μm and 3,000 to 15,000, respectively. As a result, this study illustrates the successful development of the CFD model for prediction of ibuprofen removal using HFMC according to which removal efficiency of more than 95% was achieved.