Thermo-economic analyses of isothermal water gas shift reactor integrations into IGCC power plant

Abstract

Thermodynamic performance and economics of integrating three different types of isothermal water gas shift (WGS) reactors into integrated gasification combined cycle (IGCC) power plants have been analyzed and compared to an IGCC with adiabatic WGS reactors. Isothermal shifting has shown to shift the steam generation from intermediate pressure (IP) steam towards high pressure (HP) steam. More HP steam generation leads to increased power output of the Rankine cycle and ultimately increases efficiency. Another factor impacting the efficiency is the amount of shift steam added to the WGS reactor. By lowering the amount of shift steam needed, more power is generated by the Rankine cycle. Shift steam requirement is reduced at higher temperatures which is favorable for HP steam generation. Integrating an isothermal WGS reactor into an IGCC remains challenging in cases of high carbon capture as thermodynamic equilibrium favors CO conversion at lower temperatures. The relatively low cooling density when HP boiler feedwater is used in the isothermal reactor poses economic challenges as it increases reactor size and catalyst requirement. Using the Ro-number to optimize the isothermal WGS reactor offers the best economic results with reduced capital cost, operating cost and cost of electricity.