Evaluation of Using Supercritical Rankine Cycles in Integrated Coal Gasification Combined Cycles (IGCC)

Abstract

Coal is a prominent energy resource in the modern world, particularly in countries with emerging economies. In order to reduce emissions, it is necessary to find a way to utilize coal in a cleaner manner, such as through supercritical and ultra-supercritical Rankine cycles and the Integrated Gasification Combined Cycle (IGCC). Two approaches — raising the boiler pressure and using a reheat scheme — have been proven to notably increase the Rankine cycle efficiency. Thus, this study aims to investigate the effects of implementing reheat and supercritical or ultra-supercritical pressure in the bottom Rankine cycle on the IGCC cycle efficiency. First, reference cases of a standalone Rankine cycle were studied with single and double reheat, including boiler pressure levels from subcritical to ultra-supercritical conditions, followed by similar combined cycle cases, and finally IGCC systems. The results indicate that the notable efficiency enhancement in the standalone subcritical Rankine cycle do not prevail in the studied IGCC systems. Thus, it is not economically worthwhile to implement supercritical or ultra-supercritical bottom Rankine cycles in IGCC applications.