Evaluation of a dense skin hollow fiber gas-liquid membrane contactor for high pressure removal of CO2 from syngas using Selexol as the absorbent

摘要

Integrated Gasification Combined Cycle (IGCC) technologies involve the processing of synthesis gas (syngas) produced by carbonaceous fuels gasification. CO2 removal from syngas is a key requirement for combined CO2 capture and hydrogen production in IGCC power plant processes for both power generation and greenhouse-gas emission mitigation. Conventional absorption in packed columns using pressurized physical solvents such as Dimethyl Ether of Polyethylene Glycol (DEPG) (Selexo (TM)) is commonly used for this application. In this work, a dense skin hollow fiber membrane contactor (HFMC) based process for CO2 absorption and desorption using Selexol as a physical absorbent is investigated by simulation and compared to the conventional process. The ability of dense membranes to withstand high transmembrane pressure differentials allows the absorbent to circulate in a closed loop system at a fixed pressure set independently of the syngas pressure. Differing from the conventional process, neither absorbent depressurization before the desorber nor absorbent recompression before the absorber are needed. Under the investigated operating conditions wherein we used polydimetylsiloxane (PDMS), one of the most gas permeable polymeric membrane materials available, this process allowed for recovery of up to 94.6% of CO2, with CO2 and H-2 purity of 92.4% and 96.6% respectively. The corresponding energy requirement for the absorption and desorption loop was of 0.19 MJ(eI)/kg CO2 which is approximately two times lower than that reported in the literature under comparable gas inlet conditions and separation specifications using packed columns. Without flash recovery, the corresponding H-2 loss was of 4.8%. The overall mass transfer coefficient was of 1.2 . 10(5) m/s and 6.8 . 10(6) m/s in the absorber and desorber respectively. Membrane mass transfer lower or comparable to that of the absorbent combined with higher CO2/H-2 membrane selectivity is required for H-2 loss decrease. Lower