Study And Design Of Blast Furnace Top Gas Pressure Control System In TRT

TRT is the abbreviation of Top Gas Pressure Recovery Turbine Unit, which is widely accepted as an effective secondary energy recycling device by domestic and international iron and steel enterprises. It works by blowing the blast furnace top gas into a turbo-expander, then converting the pressure and heat energy of the top gas to mechanical energy, and finally driving electrical generators. TRT produces electricity power at a low price, with no pollution. Its effect of recycling energy is outstanding. As an energy recycling device, the precondition of applying a TRT unit is the stability of blast furnace's top gas pressure, and thus no disturbance will be introduced to the main process of iron-making.Traditional TRT top gas pressure control system is cascade structure, using PID as the control method both in primary and secondary control loop. However, with modern iron-making technology's development and blast furnace's expansion, the demand on top pressure stability becomes increasingly high. And the traditional control strategy is no longer able to achieve the expected control requirements.In this thesis the main factors which influence the stability of TRT top gas pressure are analyzed, and an advanced solution of top gas pressure control is presented.(1) For primary control loop: This thesis analyzes the blast furnace burden'seffect to top gas pressure, and establishes a dynamical model of the TRT system—the opening of static blade and the height of blast furnace burden as inputs, the top gaspressure as output—by mechanism analysis and parameter identification based ondata from industrial field. Validating experiments are carried out on this dynamic model, and simulation results show that the model is precise. Based on the established model of top pressure, a Feedforward-DMC controller is designed. The simulation experiments are carried out on matching and mismatching models, and the performances of Feedforward-DMC, DMC, Feedforward-PID and PID are compared. The results show that Feedforward-DMC has high performances with good robustness.(2) For secondary control loop: A FPGA based digital electro-hydraulic servo controller is designed to replace the traditional analog electro-hydraulic servo controller. The new servo controller solves the problems of traditional one, such as unchangeable controller parameters etc. New servo controller also shows the possibility of applying advanced control method in electro-hydraulic servo system, so as to improve the stability of top gas pressure.