Load-following performance of IGCC with integrated CO2 capture using SEWGS pre-combustion technology

The performance assessment of an Integrated Gasification Combined Cycle (IGCC) integrated with the Sorption Enhanced Water Gas Shift (SEWGS) technology for pre-combustion CO2 capture at full-load and part-load modes of operation is investigated. Syngas from a coal gasifier is sent to the SEWGS system after going through solids and H2S removal units. A H2-rich stream is produced by the SEWGS system and used in a gas turbine (GT) for combustion. A control strategy including a buffer tank followed by a control valve, between the SEWGS system and the GT is implemented to smooth out the fluctuations in the H2-rich fuel flow rate, resulted from the cyclic operation of the PSA-based SEWGS system. Simulation of the IGCC integrated with the SEWGS system is first performed at full-load operation of the GT. For evaluating part-load performances, four different cases, introducing various load change strategies for the GT and gasifier are studied. Step/ramp changes of the GT and gasifier, unplanned/planned GT load changes and same/different GT and gasifier load change occurrence time are all addressed through these four cases. Simulation results indicate that the designed control strategy is able to minimize the H2-rich fuel flow rate fluctuations and dampen the fuel composition variations, while keeping the buffer tank pressure within the desired range. Dynamic characteristics of the SEWGS system are revealed and compared with those of the gasifier and the GT. Using the buffer tank between the SEWGS and the GT, improves part-load operation flexibility of the GT. Smooth operation and load following capability of the IGCC integrated with the SEWGS system are achievable, depending on the GT part-load level and load change strategy, taking into account the limited load gradient of the gasifier and the SEWGS units compared to the GT.