Research on Optimization of Residual Natural Gas Distribution for Combined Cycle Unit Shutdown Process
Although combined cycle gas turbine (CCGT) has been utilized and studied intensively, little attention was paid on optimizing its shutdown process. Under limited residual natural gas, the optimization of shutdown process of CCGT becomes a problem needed to be solved, and no research has been conducted on solving this particular problem. In this study, the overall performance and characteristics of the shutdown process of CCGT were analyzed and modeled. This model was proposed to allocate gas consumption during shutdown process for creating maximum power generation and maximum economic benefit. Based on the shutdown process model, optimal shutdown scheme was proposed and proved, and optimizing algorithms were developed to facilitate the decision making procedure. The calculations of different load-up rates and load-off rates of CCGT showed that the total power generation is more relevant with the load-off rates rather than the load-up rates. When the residual natural gas volume assumed to be 105 m3, the shutdown optimization could generate an extra power of 28.41 MW⋅h and an extra profit of 4.79 million Yuan annually. This program was applied on three CCGTs in a power plant in Zhejiang Province, China, as a case study. The testing results proved that the obtained optimization scheme is technically stable and effective in the real working condition. Thus, the model and the optimization algorithms were also valid and feasible for potential applications.