Influence of Gas Turbine Off-design Operating Conditions on the Performance of an IGCC (Integrated Gasification Combined Cycle) System

By using the proven commercial software Thermoflex,a simulation was performed of an IGCC (integrated gasification combined cycle) demonstration unit rated at 200 MW,which is to be built in China.A mass and heat balance calculation of the unit was also conducted.By adopting an IGV (inlet guide vane) regulation mode during a load reduction featuring a constant T3 (temperature before a steam turbine),which is currently often used by combined cycle gas turbines,the authors have first analyzed the changes of T3,T4 (exhaust gas temperature) and QGe (gas turbine exhaust gas flow rate) caused by gas turbine off-design operating conditions under the present control mode and then calculated the influence of the change of T3,T4 and QGe on the efficiency,power output,fuel consumption of the system as well as on the main parameters at the steam side.As a result,the off-design characteristics of the IGCC system and a general law governing the change of its main parameters were obtained.A requisite analysis of the safety and cost-effectiveness of the system operating under off-design conditions was performed.It has been found that the regulation modes can directly affect the off-design performance of the IGCC system.To ensure the cost-effectiveness and safety of the IGCC system when it is operating under off-design conditions,the gas turbine should be controlled as much as possible within the IGV regulation limits.