| The control system of the roller hearth reheating furnace in Lianyuan Steel Hot Strip Mill is imported from the USA. Through the application of a few years, the control system has some problems including unbalance temperature, slow speed of control loop response, unreasonable ratio between air flux and gas flux and temperature setting not meeting the actual production and so on. These problems not only affect the quality of the billet heating, but also result in the waste of gas resources. How to determine the appropriate gas flow rate and air flow rate, ensure the thermal efficiency and make it in the optimum burning state is the key problem of the combustion control of the roller hearth reheating furnace.This thesis fully analyzes the relation between the gas calorific value and the ratio between air flux and gas flux, and analyzes the relation between the change of the furnace temperature and gas flux, respectively. An optimization model of combustion control in reheating furnace based on intelligent control strategy is proposed to optimize the value of gas flux and the ratio between air flux and gas flux. The temperature of reheating furnace is set accurately using 2-inputs-1-output fuzzy controller in order to suppress the fluctuations of gas calorific value and gas pressure, enhancing the stability of furnace temperature. A self-optimizing method of the ratio between air flux and gas flux is developed to improve the efficiency of gas and ensure reasonable ratio between air flux and gas flux. According to the gas calorific value from calorimeters, fuzzy-expert controller of gas flux is used to optimize the value of gas flux, which ensures stability of the reheating furnace temperature, full combustion of gas, reducing the oxidation possibility of slab and energy consumption. In addition, closed-loop control method of valve is employed to improve accuracy of gas flow control, so that it makes the reheating furnace in the most reasonable state. The industrial application of the intelligent optimization model of roller hearth reheating furnace is also discussed in this thesis. The combustion control system is implemented using VC++ language as its development tool on the platform of In-Touch. The communication between application software and configuration software is realized by OPC technology. The results of tests and real-running show that the optimization model for combustion control improves the stability and balance of temperature effectively, and reduced the negative impacts from the fluctuation of gas calorific value. It provides an efficient method for the optimization control in the roller hearth reheating furnace burning process. |
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