On the effects of running existing combined cycle power plants on syngas fuel

The use of gasified fuels for electricity production is of increasing interest as an alternative to traditional fuels especially in regions with abundant biomass or coal resources. Nevertheless, its use in current gas turbine technologies is challenging due to the differences in fuel composition with respect to conventional natural gas.In this paper, the effects of using a set of syngas fuels on the components of a reference combined cycle are studied. The analyses shown in this paper are focused on the expansion of the different combustion products through the turbine and on the bottoming cycle. In the gas turbine, the effect of the different combustion product properties and mass flows on the performance of the expansion process is studied first. Then the impact on the turbine cooling system of a standard natural gas engine is analyzed. In the bottoming cycle the higher load on each particular component is studied aiming to find bottlenecks to the operation under the new operating conditions.The results show that from the combined cycle power plant standpoint, excluding the gasification island, an adequate upgrade of the components of the power block results in a combined cycle performance in syngas operation that is similar to using natural gas. This provides the combined cycle owner/operator with a valuable perspective to evaluate technology risks and appraise potential retrofitting of their plants depending on fuel cost and availability.

► Gas turbine. Effect of the fuel on the turbine expansion and turbine cooling.
► Combined cycle. Effect of the syngas fuelling on the bottoming cycle components.
► Gas turbine updating for operating with syngas fuels.
► Bottoming cycle updating the new operating conditions with the syngas fuels.