Detailed Process Simulation of Pre-combustion IGCC Plants Using Coal-slurry and Dry Coal Gasifiers

Abstract

The selection of the gasifier in an Integrated Gasification Combined Cycle (IGCC) plant affects both downstream process configurations and net plant efficiency considerably. It is well known that a Shell gasifier using dry coal has lower operating pressure, higher carbon conversion, lower CO2 production and lower H2/CO ratio compared to a General Electric Energy (GEE) gasifier using coal slurry. These differences also affect how to configure downstream processes when an IGCC is retrofitted for carbon capture. The net plant efficiency decreases by different extents depending on the gasifier type as shown in the DOE NETL report The aim of this study is to elucidate how the differences between the two gasifiers correspond to the difference in plant performance without and with carbon capture. To achieve this, detailed process simulations of the two IGCC plants and an integrated Selexol carbon capture unit have been carried out based on literature configurations using the commercial software Honeywell UniSim Design R400®. From the analysis of the results an explanation is presented as to why the wet slurry gasifier configuration has a lower net efficiency loss when the carbon capture unit is integrated.