Gas turbines for APFBC repowering applications

It is often difficult to repower an existing steam unit with a natural gas fired power turbine. This is because the gas turbine exhaust is generally too low in temperature to meet the superheat and reheat steam needs of existing steam turbines without making compromises that make less than effective use of existing equipment. However, advanced circulating pressurized fluidized bed combustion combined cycle (APFBC) technology has several features that make it an effective option for repowering. The main feature is that existing steam turbine superheat and reheat steam demand can be met by firing char and, if necessary, coal in the fluid bed combustor. The heat energy rejected from the gas turbine can then be used as a supplement to the steam generated in the fluid bed combustor. APFBC repowering significantly improves plant efficiency, environmental performance, and reduces operating costs. This paper describes APFBC-modifications of gas turbines, from several manufacturers that have potential for repowering existing steam plants with high efficiency APFBC technology. The paper discusses the issues that must be addressed by the gas turbine manufacturers for APFBC repowering service.