Abstract: A combined cycle coal gasification power plant includes a coal gasifier which generates low BTU coal gas for consumption by a gas turbine. Before being applied to the gas turbine, the coal gas is passed through a clean-up system which removes undesirable constituents from the coal gas. Efficient operation of the clean-up system requires that a predetermined discharge pressure of clean coal gas leaving the clean-up system must be maintained. A control system controls the coal gasifier according to either one of the discharge pressure of clean coal gas and the turbine power output requirement while maintaining the clean coal gas discharge pressure and power output at predetermined values.