Blast Furnace Gas Gas-steam Combined Cycle System Modeling And Load Control System Design

Blast furnace gas is the main waste gas produced in the steelmaking industry.Blast furnace gas gas-steam combined cycle uses blast furnace gas as the main fuel,which can effectively save energy and reduce emissions,and develop a circular economy.However,the structure and operation principle of blast furnace gas turbines are different from those of traditional natural gas turbines,and blast furnace gas has the characteristics of frequent changes in composition and calorific value,which leads to the combined cycle unit often deviating from the design conditions.In addition,the combined cycle itself has the characteristics of large inertia,strong coupling and strong nonlinearity.In the case of the total load adjustment process of the unit and the fluctuation of fuel heating value,it may be difficult for the traditional control system to obtain satisfactory control results.Therefore,it is of great significance to grasp the dynamic characteristics of the combined cycle of blast furnace gas and adopt advanced control algorithms to improve the control strategy.The main research contents of this article are as follows:(1)A complete blast furnace gas combined cycle dynamic mechanism model is built on the Matlab/Simulink platform.On this basis,the system was stepped dynamically from the perspective of fuel bypass valve opening,IGV opening and fuel calorific value Response test.According to the dynamic response curve,the dynamic characteristics among the main variables of the blast furnace gas combined cycle were analyzed from the perspective of mechanism.(2)In view of the characteristics that the inertia of the steam turbine in the combined cycle of the blast furnace gas is much larger than that of the gas turbine and the fluctuation of the calorific value of the blast furnace gas,the nonlinear and coupling analysis of the system is first carried out.On this basis,the front based on measurable disturbance is proposed.The load control scheme fed to MPC uses changes in IGV and fuel calorific value as measurable disturbance feedforward information.Aiming at the strong nonlinear problem of blast furnace gas combined cycle large-scale variable operating conditions,a multi-model MPC controller strategy is proposed,and the IGV opening is selected as a scheduling variable,which effectively reduces the influence of nonlinearity on control quality when the load changes widely.(3)In addition to the design of a core closed-loop control algorithm,other control logic and related design issues need to be considered for the development of a complete control system in engineering.For models with special structures and operating principles such as blast furnace gas turbines,there are few self-developed control systems on the domestic DCS platform.In response to this problem,a complete set of blast furnace gas turbine control system was developed based on the NT6000 platform.The content includes control point and IO interface design,control logic design(including analog control),data connection point,man-machine screen,etc.Finally the control system is put into operation test.