Hollow fiber carbon membranes: Investigations for CO2 capture

Hollow fiber carbon membranes were prepared from the cellulosic precursors by controlling the carbonization protocol of CO2 using 823-4 K/min for 2 h. The prepared carbon membranes presented a symmetric structure and a much smaller wall thickness of 25 mu m compared to the precursor (40 mu m) from the SEM images. Single gas (i.e. O-2, N-2, CO2) permeation tests indicated that the molecular sieve mechanism was the dominating transportation mechanism for the gas species through the carbon membranes. The influences of operating parameters on the carbon membrane separation performance include pressure, temperature, retentate flow rate and feed CO2 composition. These parameters were systematically investigated by factorial design method. The experimental and process simulation results indicated that the CO2 purity can only achieve ca. 75% with one stage membrane configuration. Therefore, a simple two stage cascade configuration without sweep was designed for the process optimization based on the capital cost estimation of the major equipments. A CO2-purity of 90% was then achieved with 60% CO2 capture. Although the specific capital cost for carbon membrane technology is still high compared to the traditional chemical absorption method, simulation results also proved that the costs can be significantly decreased by reducing the carbon membrane wall thickness from 25 to 10 mu m-this is considered to be a realistic option. Therefore, the prepared hollow fiber carbon membranes needs to be further optimized in order to be a potential candidate for CO2 capture. (C) 2010 Elsevier B.V. All rights reserved.