HRSG Design for Integrated Reforming Combined Cycle With CO2 Capture

Abstract

This article illustrates aspects of heat recovery steam generator (HRSG) design when employing process integration in an integrated reforming combined cycle (IRCC) with precombustion CO2 capture. Specifically, the contribution of this paper is to show how heat integration in a precombustion CO2 capture plant impacts the selection of HRSG design. The purpose of such a plant is to generate power with very low CO2 emissions, typically below 100 g CO2/net kWh electricity. This should be compared with a state-of-the-art natural gas combined cycle (NGCC) plant with CO2 emissions around 380 g CO2/net kWh electricity. The design of the HRSG for the IRCC process was far from standard because of the significant amount of steam production from the heat generated by the autothermal reforming process. This externally generated steam was transferred to the HRSG superheaters and used in a steam turbine. For an NGCC plant, a triple-pressure reheat steam cycle would yield the highest net plant efficiency. However, when generating a significant amount of high-pressure steam external to the HRSG, the picture changed. The complexity of selecting an HRSG design increased when also considering that steam can be superheated and low-pressure and intermediate-pressure steam can be generated in the process heat exchangers. For the concepts studied, it was also of importance to maintain a high net plant efficiency when operating on natural gas. Therefore, the selection of HRSG design had to be a compromise between NGCC and IRCC operating modes.