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A membrane contactor process for pre-combustion CO 2 capture from shifted synthesis gas originated from IGCC power plant is assessed from the technical and economical point of views. The process is designed as pressure swing absorption and desorption in a closed loop. The design basis for process simulation were synthesis gas containing CO 2 and H 2 only, and the CO 2 capture efficiency was fixed to 90%. The CO 2 gas was absorbed in ionic liquid [bmim][TCM] inside a hydrophobic, porous hollow fibre membrane contactor. One-dimensional mathematical model of membrane contactor developed in MATLAB was integrated to the process simulation software (HYSYS) through Cape-Open simulation compiler. The energy evaluation of this process revealed that compressors are the most energy demanding process equipment. The specific energy requirement for this process is estimated 0.75 MJ/kg CO 2 . A parametric study was also performed to analyse the effect of CO 2 concentration in feed gas and liquid to gas ratio. The capital cost investment and total operating costs of CO 2 capture unit were also evaluated. The capital investment required for capturing 0.14 M ton CO 2 /year including CO 2 compression is 47.4 M $, and the operating cost per year is 9.04 M $. The membrane absorber contributed about 39% to total investment cost. The specific cost of this capture unit is calculated to be 87 $/ton CO 2 . [ABSTRACT FROM AUTHOR]

The mixture of the ionic liquid 1-ethyl-3-methylimidazolium acetate (EmimAc) and dimethylsulfoxide (DMSO) was employed to dissolve microcrystalline cellulose (MCC). A 10 wt % cellulose dope solution was prepared for spinning cellulose hollow fibers (CHFs) under a mild temperature of 50 °C by a dry–wet spinning method. The defect-free CHFs were obtained with an average diameter and thickness of 270 and 38 µm, respectively. Both the XRD and FTIR characterization confirmed that a crystalline structure transition from cellulose I (MCC) to cellulose II (regenerated CHFs) occurred during the cellulose dissolution in ionic liquids and spinning processes. The thermogravimetric analysis (TGA) indicated that regenerated CHFs presented a similar pyrolysis behavior with deacetylated cellulose acetate during pyrolysis process. This study provided a suitable way to directly fabricate hollow fiber carbon membranes using cellulose hollow fiber precursors spun from cellulose/(EmimAc + DMSO)/H2O ternary system. [ABSTRACT FROM AUTHOR]

A computational approach is presented for prediction of cellulose solubilities in ionic liquids (ILs) based on COSMO-RS (Conductor-like Screening Model for Real Solvents). Thermodynamically stable molecular structures were optimized from 2D structures of cellulose and ILs following specific force-field based search of conformation lowest in energy and quantum chemical optimizations of molecular geometry. The thermodynamic property of logarithmic activity coefficient (lnγ) and excess enthalpy (H E ) were calculated by COSMO-RS based on the COSMO molecular surfaces of cellulose and ILs to qualitatively predict the ability of ILs for cellulose dissolution. To evaluate the method, four sets of ILs were used to calculate lnγ and H E based on four different cellulose models. The goodness-of-fit of linear regressions between the experimental cellulose solubilities and the calculated lnγ and H E shows that lnγ is more reliable than H E for prediction of the dissolving power of ILs to dissolve cellulose. However, H E is more suitable for prediction of the dissolution ability of halogen-based ILs. Moreover, all the cellulose models gave comparably good prediction results regarding of the dissolving power of ILs based on the calculated lnγ, but the cellobiose model was identified as the optimal model due to the relatively higher prediction ability (R 2 ) across different IL datasets. The approach is time efficient and robust, which provides a novel method for large-scale screening of ILs for cellulose dissolution. [ABSTRACT FROM AUTHOR]

Mass transfer and mathematical modelling of CO 2 absorption in a tubular membrane contactor using 1-Butyl-3-methylimidazolium Tricyanomethanide ([Bmim][TCM]) for pre-combustion CO 2 capture has been studied in this work. A 1D-model was developed based on resistance in series model and CO 2 material balance. The developed model was validated with the experimental data, and good agreement was observed between the simulated and experimental results. A new mass transfer resistance term is added to reflect the non-flat concentration profile in the liquid phase. Simulation results indicate that the liquid phase resistance contributes 67% and 44% to the total mass transfer resistance for non-wetted and wetted modes of membrane respectively. The resistance that occurred due to considering transport in liquid phase contributes 31 and 20% for non-wetted and wetted modes of membrane contactor respectively. CO 2 flux along the axial length of membrane contactor was modeled, giving the maxima at the gas outlet. The influences of operational constraints including liquid/gas flow rates, operation pressure/temperature, length of membrane contactor, and CO 2 concentration in feed gas were also inspected. [ABSTRACT FROM AUTHOR]

Amino acid ionic liquids are green solvents with low toxicities and properties suitable for precombustion CO2 capture, such as high CO2 absorption, good thermal stability, and negligible vapor pressure. However, their high viscosities and relatively high costs have hampered their industrial applications. In this work, we systematically studied the amino acid ionic liquid tetrabutylphosphonium glycinate ([P4444][Gly]) and its blends with the low-cost and less viscous cosolvent poly(ethylene glycol) (PEG400). The concentration of the blend solvent was optimized with respect to CO2 solubility, regeneration efficiency, and cyclic capacity. The solubilities of CO2 in [P4444][Gly], PEG400, and their blends of four different concentrations were measured experimentally in the temperature range of 60-140 °C and up to a pressure of 17 bar. The results showed that the CO2 solubility increased with increasing ionic liquid concentration in the blend and decreased with increasing temperature. The optimum CO2 absorption was determined to occur at 30 wt % of [P4444][Gly] in the blend. The regeneration study of the 30 wt % [P4444][Gly]-70 wt % PEG400 blend for three cycles verified its reusability in the process and confirmed that the reaction between [P4444][Gly] and CO2 can be reversed at 140 °C. The CO2 absorption capacity of the blend absorbent was found to be up to a loading of 1.23 mol of CO2/mol of absorbent. The parameter fitting of the experimental data using empirical correlations was evaluated, and these correlations were developed in particular to predict the blend solvent of an amino acid ionic liquid-PEG400 system based on the ionic liquid concentration and temperature. [ABSTRACT FROM AUTHOR]

Carbon hollow fiber membranes (CHFMs) were fabricated based on cellulose hollow fiber precursors spun from a cellulose/ionic liquid system. By a thermal treatment on the precursors using a preheating process before carbonization, the micropores of the prepared CHFMs were tightened and thus resulting in highly selective carbon molecular sieve (CMS) membranes. By increasing the drying temperature from RT to 140 °C, the cellulose hollow fiber precursors show a substantial shrinkage, which results in a reduction of average pore size of the derived CHFMs from 6 to 4.9 Å. Although the narrowed micropore size causes the decrease of gas diffusion coefficient, stronger resistance to the larger gas molecules, such as CH 4 , eventually results in an ultra-high CO 2 /CH 4 ideal selectivity of 917 tested at 2 bar for CHFM-140C due to the simultaneously enhanced diffusion and sorption selectivity. The CHFM-140C was further tested with a 10 mol%CO 2 /90 mol%CH 4 mixed gas at 60 °C and feed pressure ranging from 10 to 50 bar. The obtained remarkable CO 2 /CH 4 separation factor of 131 at 50 bar and good stability make these carbon membranes great potential candidates for CO 2 removal from high-pressure natural gas. • Highly CO 2 selective CMS membranes made from cellulose precursors. • CMS membranes present ultra-high CO 2 /CH 4 selectivity of 917 at 2 bar. • CO 2 /CH 4 mixed gas testing up to 50 bar shows potential for natural gas sweetening. [ABSTRACT FROM AUTHOR]