Performance analysis of a water–gas shift membrane reactor for integrated coal gasification combined cycle plant

Abstract

In integrated gasification combined cycle (IGCC) systems, the water–gas shift reaction, which promotes the conversion of CO present in syngas mixtures into hydrogen, is an important step for hydrogen production. Application of the water–gas shift membrane reactor (WGSMR) in IGCC systems is an attractive option for CO2 capture compared with conventional methods because of smaller heat loss in gas purification and high CO conversion by selectively removing hydrogen from the reaction zone through the membrane. In this study, we proposed and evaluated commercial-scale WGSMR models combined with IGCC using reported laboratory-scale experimental data to optimize their operational parameters. Various models were developed using the Aspen Plus® Ver. 8.6 process simulator to investigate the impacts of hydrogen separation, pressure loss, and the flow direction between the sweep gas on the permeate side and syngas on the retentate side on the WGSMR performance with respect to CO conversion, H2 yield, and reactor temperature. The membrane reactor model gave approximately 20% higher CO conversion than a reactor model without H2 separation and approximately 4% lower CO conversion than a membrane reactor model with a pressure drop. A counter-current membrane reactor model gave approximately 2% higher CO conversion than a co-current model; the H2 yield on the permeate side was 9.3% higher in the counter-current model by separation of H2 through the membrane. A sensitivity analysis indicated that a high flow rate and low pressure of sweep gas are advantageous for H2 recovery, and high catalyst loading and high syngas inlet temperature are preferable for higher CO conversion.