Recent developments in gas turbine materials and technology and their implications for syngas firing

Abstract

Gas turbine combined-cycle systems burning natural gas represent a reliable and efficient power generation technology that is widely used. A critical factor in their development was the rapid adaptation of aero-engine technology (single crystal airfoils, sophisticated cooling techniques, and thermal barrier coatings) in order to operate at the high rotor-inlet temperatures required for high efficiency generation. Early reliability problems have been largely overcome, so that this type of power generation system is now considered to be a mature technology capable of achieving high levels of availability. Current interest in replacing natural gas with gas derived from coal (syngas or hydrogen) in these gas turbine systems focuses attention on implications for the critical turbine components. In this paper, the development requirements for materials for critical hot gas-path parts in large gas turbines burning coal-derived syngas fuels are briefly considered in the context of the state-of-the-art in materials for engines burning natural gas. It is shown that, despite some difficult design issues, many of the materials used in current engines will be applicable to units burning syngas. However, there is the potential that the durability of some components may be prejudiced because of differences in the combustion environment (especially in terms of water vapor content, and possibly sulfur compounds and particulates). Consequently, effort to develop improved coatings to resist erosion and also attack by S-containing compounds may be necessary.