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A complementary study, which involves computational and in-house collected experimental work, has been employed to elucidate the swelling effect within polysulfone membranes by CO 2 at varying operating temperatures. The simulation models have been constructed with accordance to collected experimental data. The experimental and simulated sorption isotherms of CO 2 are in fairly good agreement with one another. Subsequently, the constructed molecular structures of unswollen and swollen polysulfone membrane at varying operating temperature has been analyzed to study the effect of CO 2 in terms of physical characteristic, glass transition temperature, relaxation and free volume to determine whether the temperature or concentration parameters are more dominant in CO 2 swelling. In addition, radial distribution function (RDF) between CO 2 and varying groups within polysulfone has been evaluated to determine association reaction that invokes the dilation. RDF at various operating temperature has been employed to be incorporated within a series of thermodynamic equations in order to quantify the interaction of CO 2 with polysulfone that constitutes to swelling. [ABSTRACT FROM AUTHOR]

Swelling in polymeric membranes due to the humid feed is a major issue in gas separation applications at offshore conditions. To ensure the integrity of the polymeric membrane, a high capital cost dehydration system is typically installed together with the membrane system. Hence, to minimize the dehydration requirement, a swelling resistant membrane was developed by film casting of polydimethylsiloxane (PDMS) over polysulfone (PSF). The PSF/PDMS composite membrane exhibited higher contact angle as compared to PSF membrane. Performances of the developed membranes were evaluated with and without water in the feed gases at the pressure of 2–10 bar. Separation performance in the PSF membrane was affected by swelling in the membrane; however, the composite membrane with the PDMS film resisted the water swelling in membrane and CO 2 /CH 4 selectivity increased from 21.6 to 27.7 at 10 bar. Under wet feed conditions, the PSF/PDMS composite membrane exhibited stability for 24 h with stable permeance and selectivity. Based on the permeation results and the stable performance of a PSF/PDMS membrane, it can be concluded that the developed composite membrane demonstrates a potential to be used in an offshore membrane system with the minimum dehydration requirement for CO 2 /CH 4 separation. [ABSTRACT FROM AUTHOR]

CO 2 capture for power plant and natural gas purification using absorption process suffers two major drawbacks: large absorption body and high regeneration energy. The high energy penalty of absorption technology can be addressed using low heat of absorption solvent. However, the challenge of using low heat of absorption solvent is to develop a practical approach to intensify absorption rate. In recent years, high frequency ultrasonic system emerges as a potential technology for mass transfer process. In this study, the potential of using high frequency ultrasonic system have been investigated using the slow kinetic solvent: (potassium carbonate) without utilizing any chemical promoter. The ultrasonic-assisted absorption system with 20 wt% potassium carbonate (without promoter) has provides 1.75 times higher volumetric mass transfer coefficient than the Piperazine (PZ) promoted potassium carbonate using stirring method. The absorption rate has been increased up to 32 times as compared to the case without ultrasonic irradiation. Besides, the required absorption time to achieve 0.9 loading (CO 2 mole/K 2 CO 3 mole) has been significantly reduced to approximate 400 s. Furthermore, an ultrasonic-assisted absorption model has been developed by including the atomization, ultrasonic streaming, and ultrasonic chemical effect in order to investigate the mechanism involved in high frequency ultrasonic-assisted absorption. Based on the model validation study, the ultrasonic chemical effect is essential to be considered in order to match the simulated and the experimental results. The results of current study prove that, high frequency ultrasonic system possesses high potential to be utilized to enhance the absorption using promoter-free potassium carbonate. [ABSTRACT FROM AUTHOR]

In this work, Polydimethyl siloxane/polysulfone (PDMS/PSF) membrane was developed by dip coating of developed PSF membrane. Developed membranes were characterized in terms of thermal analysis, glass transition temperature, and membrane morphology. Performances of the developed membranes were tested using gas permeation equipment within the pressure range of 2-10 bar. To study the water swelling in membrane, developed membranes were soaked in distilled water for 5 minutes. Gas permeation in membrane was investigated before and after swelling. Based on the results, increase in CO 2 permeance was observed due to plasticization in membrane before swelling. However, CO 2 permeance decreased after swelling in membrane. Swelling affected the separation performance of membrane by decreasing its permeance. While, CO 2 /CH 4 selectivity has increased after membrane swelled. Hence, swelling resulted in membrane contraction, which contributed to the increase of selectivity. Pure polysulfone membrane exhibited higher degree of swelling, whereas PDMS/PSF membranes demonstrated substantial high resistance toward swelling. Based on swelling degree of PDMS/PSF composite membrane, this membrane can be considered as a potential water (swelling) resistant polymeric membrane for CO 2 /CH 4 separation. [ABSTRACT FROM AUTHOR]

Polymeric membranes demonstrate the fastest emerging field in membrane gas separation since it has huge reproducibility for large scale production and low cost fabrication. To date, many research works have emerged to propose different polymeric materials for membrane synthesis and fabrication in order to enhance gas separation performance. It has been suggested that the underlying factor that distinguishes the difference in separation efficiency among varying polymer is the amount of free volume formed throughout the polymeric matrix. Therefore, in current work, through adaptation of atomistic models by a combination of molecular dynamics and Monte Carlo or commonly known as the Cavity Energetic Sizing Algorithm (CESA), the cavity size distributions of several commonly adapted polymeric membranes for gas separation have been determined. The accuracy of the simulated molecular structure has been verified by comparing the simulated and measured experimental density. It is found from the study that that the CESA algorithm is capable of capturing the free volume distribution within the polymeric matrix, with the higher free volume polymeric membrane inheriting higher average cavity size [PTMSP (10.30A) >PPO (4.86A) >Matrimid® 5218 (4.01A) >PSF (3.25A)]. In addition, the higher free volume polymers, which exhibit shift towards the larger cavity sizes, also reveal higher gas permeability for gas molecules. The sieving capability of the polymer is also demonstrated to be correlated with the kinetic diameter of the gas penetrants as compared to the cavity size. In future work, the methodology is proposed to be employed as a preliminary step to predict polymeric membrane morphology in order to evaluate the feasibility of any polymers before being applied in gas separation. [ABSTRACT FROM AUTHOR]

In this work, the rheology of a solvent which consisted of monoethanolamine (MEA) as well as water and n-methyl-2-pyrrolidone (NMP) (weight ratio 20:40:40) was studied at gauge pressure up to 5 MPa and temperature range from 303.15 to 333.15 K. The flow chart showed positive linear relationship between shear stress and shear rate for the solvent at all temperature and pressure conditions tested. This trend was consistent with the behaviour of a Newtonian fluid. The dynamic viscosity of MEA-NMP hybrid solvent at temperature from 303.15 to 333.15 K and gauge pressure from (0.1 to 5) MPa was calculated from the rheology data measured. [ABSTRACT FROM AUTHOR]

Modeling and simulation on lean carbon dioxide (CO 2 ) absorption has been widely studied for low pressure conditions. However, modeling on rich CO 2 absorption in packed column requires consideration on significant decrease of total gas flow rate along the column. In this work, the absorption of CO 2 in countercurrent structured packed column at 50% concentration level in inlet gas was modeled to predict the mass transfer of CO 2 from gas phase into liquid phase. The integrated mathematical model, which is a combination of hydraulic and mass transfer correlation from SRP II model as well as mass conservation equation, was developed to elucidate the CO 2 capture profile along the absorption column for pressure conditions of 0.1, 1, 3 and 5 MPa. Based on the validation with experimental data, the mathematical model developed in this study had satisfactorily represented the mass transfer behavior of high CO 2 concentration gas removal along the absorption column at elevated pressure conditions. [ABSTRACT FROM AUTHOR]

Isothermal vapor–liquid equilibrium (VLE) data for methane (CH 4 ) + carbon dioxide (CO 2 ) binary system at temperature range of (240.35–293.15) K and synthetic carbon dioxide rich natural gas mixtures at temperature and pressure range of (248.15–279.15) K and (2.81–9.05) MPa were measured in sapphire type equilibrium cell apparatus. Thermodynamic modeling of experimental data was carried out with GERG2008–equation of state (EOS) and volume-translated Peng–Robinson equation of state (VTPR–EOS) using van der Waals (vdw1) mixing rule. For CH 4 + CO 2 system, the temperature dependent binary interaction parameters ( kij ) were tuned to measured VLE data, whereas, between CO 2 with other hydrocarbons the value of kij = 0 was assumed. Comparison between measured and prediction shows excellent agreement with overall lower deviations were obtained. [ABSTRACT FROM AUTHOR]

A mathematical model has been developed to characterize the multi-component CO 2 capture from natural gas adapting hollow fiber membrane module for the radial crossflow, countercurrent and cocurrent flow. The solution procedure can also be incorporated in a versatile manner within the Aspen HYSYS process simulator to constitute the entire CO 2 /natural gas separation plant in order to assist in the process design and optimization. The study of the separation performance and process economics of the different flow mechanisms has been conducted along with parameter sensitivity of typical membrane selectivity and CO 2 feed composition in industrial application. Based on the study's findings, ideally the countercurrent configuration exhibits a slightly higher separative performance in comparison to the radial crossflow, while both being superior to the cocurrent. It is also found that flow with the most effective separative performance is not always the most economical. Under circumstances of excessive permeation, it can lead to extra membrane area, auxiliary equipment power and hydrocarbon lost that increase the gas processing cost. Therefore, a tradeoff must be determined among these parameters to determine the optimal flow configuration for efficient CO 2 removal under different operating conditions. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO 2 ) removal is an essential step in natural gas (NG) processing to provide high quality gas stream products and minimize operational difficulties. This study aims to investigate the absorption performance of CO 2 at high concentration level of 50% from a mixture of CO 2 –NG gas stream at pressure condition of up to 5 MPa for 20 wt% monoethanolamine (MEA) aqueous solution and MEA hybrid solution consisting of 20 wt% MEA with 40 wt% N -methyl-2-pyrrolidone (NMP) + 40 wt% water in a countercurrent packed column. Comparison of absorption performance was also conducted with water and NMP in order to understand the effect of physical absorption by the individual solvent respectively. It was observed that water had minimal physical absorption for CO 2 . On the contrary, NMP was observed to be an efficient physical absorbent for CO 2 on its own. Increased pressure was found to have a positive impact on the CO 2 removal performance for water, NMP, MEA aqueous solution and MEA hybrid solution. This trend was especially significant when the pressure was at 5 MPa. [ABSTRACT FROM AUTHOR]

Highlights: [•] Performance of capture bulk CO2/CH4 with the presence of pentane was studied. [•] Various operating conditions including high pressure were investigated. [•] The performance of CO2 and CH4 in wet condition decreases compared to dry condition. [ABSTRACT FROM AUTHOR]

This review paper evaluates the critical selection criteria for slow and medium kinetic chemical solvents used in the CO 2 absorption process during natural gas purification. The chemical absorbents' reaction mechanism, capacities, chemical structure, and operating parameters on the CO 2 absorption performance was discussed. Other solvent properties such as vapor pressure, corrosively, viscosity, forming tendency, regeneration energy, thermal stability, and toxicity was investigated to portray their overall potentials industrial applications. Generally, the absorbents absorption rate is the superior determinant factor for their industrial applications. Thus, desirable solvent performance breakthrough will depend on CO 2 absorption rate enhancement research via chemical/mechanical methods. • A comprehensive review on the selection criteria of slow and medium kinetic solvents for the CO 2 absorption process. • Review of the reaction mechanism, advantages, and disadvantages for each absorbent. • Review of feasibility for each absorbent concerning the solvent selection criteria and operating conditions. [ABSTRACT FROM AUTHOR]

The continuously increasing of sour natural gas reservoirs worldwide necessitate a highly efficient CO 2 removal technology for offshore application. Therefore, the intensification technology for absorption attaches research interest to address this issue. This review covers the intensification factor, operating feasibility and perspective for each potential technology. Microchannel reactor offers the highest ideal intensification factor but suffers from offshore operation difficulties. Even-though high frequency ultrasonic reactor and rotating packed bed demonstrate high flexibility for long-term operation, yet both technologies require high energy consumption. Combination of hollow fibre membrane contactor and rotating packed bed is suggested to optimize the overall absorption process. • A comprehensive review on the intensified technologies for absorption process. • Review of the advantages and disadvantages for each technology. • Review of feasibility and perspective for each technology at offshore condition. [ABSTRACT FROM AUTHOR]