A two-stage coal-water slurry fueled high-pressure gas turbine combustion system employing a primary zone with a hot refractory wall and an internal slag removal system has been designed, built and tested. The molten ash or slag is largely removed internally by aerodynamic means using a form of jet impaction. Some small amount of the mineral matter in the coal, however, does escape the primary zone and exits the combustor. The overall combustion system is extremely flexible and can be readily configured to operate either with a lean or a rich reaction (primary) zone. In most cases a rich primary zone and a lean secondary zone is used.
Results showing the emission signatures of a number of coal-water slurry fuels operating with the combustor arranged in a rich primary zone configuration have been presented in a previous paper (1). NOx emissions were obtained that meet EPA regulations for stationary gas turbines. Deposition on a rig simulation of a turbine nozzle guide vane has been measured. The deposition appears to be a strong function of coal type and ash composition.