Carbon dioxide capture by [emim][Ac] ionic liquid in a polysulfone hollow fiber membrane contactor

Abstract

CO2 emissions have to be controlled and reduced in order to avoid greenhouse effect. This work reports an analysis of the efficiency of CO2 separation using a hollow fiber membrane contactor and an ionic liquid. This process configuration contributes to the process intensification approach in the field of CO2 capture and storage. In this study, the ionic liquid 1-ethyl-3-methylimidazolium acetate, [emim][Ac], was used as absorbent due to its high solubility. The module selected was polysulfone (Ps) because it is a well characterized polymer that allows to operate at moderate temperatures. Results were compared to previous studies with a polypropylene module. The gas stream flowed through the inside of the hollow fibers. The CO2 removal efficiency was obtained from experimental data, showing a temperature dependence: from 30 to 45.0 %, corresponding to 291 K and 348 K respectively, when the Ps contactor was used. The overall mass transfer coefficient Koverall has also been evaluated. In addition, a numerical analysis was carried out to study the performance of the membrane contactor for the CO2 capture in order to estimate the process conditions to accomplish 90% CO2 capture as a target to be competitive with the conventional absorption process.

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

“…Koonaphapdeelert et al [52] found that the mass transfer in gas stripping membrane contactors was mainly controlled by the liquid film mass transfer coefficient. Gebremariam [53], were well within the range of values found in the literature for [emim][Ac] as an absorbent [38,54]. The mass transfer coefficient values calculated for ILs versus traditional amine-based absorbents were one order of magnitude lower, mainly due to their viscosity [48].…”

“…An absorbent with a high α N would result in small size equipment and low operation cost due to the low circulation volume required. [38,42]. From the obtained results, it can also be pointed out that this IL is suitable for the CO 2 desorption by MVR process.…”

“…Performance of the absorptiondesorption process has also been studied until a steady-state was reached in order to better understanding of the influence of the MVR process in the absorption process over time. Figure 10 shows the CO2 dimensionless average concentration , , over operation time for an absorption process using HFMC versus absorption-desorption process using MVR process at vacuum pressure (Pv) of 40 mbar and temperature of 310 K. Previous studies [38] have reported efficiencies of 20-35% in the absorption process when [emim][Ac] was used as an absorbent. In this work, the efficiency in the pseudo-steady-state of the absorption process, which determined the CO2 capture efficiency, increased from 25% obtained in the absorption process to 74% in the absorption-desorption process (coupled system) using the best operating conditions (studied in this work) for the MVR process.…”

Hybrid Solvent ([emim][Ac]+water) To Improve the CO2 Capture Efficiency in a PVDF Hollow Fiber Contactor

“…In addition, with a water volume around 30% in the [emim][Ac], the mass transfer was benefited for the process. The overall mass transfer coefficient, Koverall expressed in m s -1 was calculated as in previous works according to the equation 2 [14,30,50]. , , ,…”

“…The dimensionless differential mass balance on CO2 (eq. 4) was based on the following assumptions according to previous works [50,51,52]; (1) the absorption liquid has negligible concentration of the soluble gas, (2) the process is in steady state and isothermal conditions, (3) there is not an axial diffusion, (4) an ideal gas behavior, (5) constant both fiber and shell side pressures and finally (6) the velocity is fully developed in a laminar flow.…”