Materials challenges and gasifier choices in IGCC processes for clean and efficient energy conversion

Abstract

In the 1970 and 1980s, gasifiers were envisaged for synthesising substitute natural gas (SNG) as well for IGCC (integrated gasification combined cycle) systems. Component temperatures were above 700°C, but stainless alloys did not have the required corrosion resistance. Experimental alloys developed in the UK were alumina formers, incorporating Ta, W, and Mo as gettering elements for sulphidation resistance. Sulphidation corrosion is solvable, but attack by HCl in gasification environments seems intractable. The supposed materials problems of gasification, plus the complexity of IGCC, have led to them being sidelined for power generation. However, commercial IGCC plants are not dependent on high temperature materials and offer higher efficiency than Rankine cycle steam. Best near term prospects for IGCC are for CO2 capture, but this constrains the type of gasifier. Gasifiers incorporating carbon capture and storage produce hydrogen, or with less capture, SNG. Such systems will supply SNG for space heating as well as electricity, and can cope with the intermittency of wind energy. High efficiency IGCCs will need very advanced gas turbines with 100 bar, 1500-1600°C turbine inlet conditions. Key requirements will be thermal barrier coatings and catalytic combustor materials. Such gas turbines would offer efficiencies of 70% in straight CCGTs, or 50% when used in carbon capture IGCCs.