Research On End-point Control Technology Of AOD Furnace Based On Improved Inference Control

In ferrochrome alloy smelting process,controlling the temperature and carbon content of the iron is the core of the whole blowing process,however,smelting ferroalloys is a very complex multi-phase high temperature state of the non-linear physicochemical reaction process,there are many uncertainties,both to consider a variety of interference,but also to consider the process of spattering and AOD furnace life and other issues,the traditional control method is difficult to achieve satisfactory results This paper takes AOD smelting low-carbon ferrochrome alloy production process as the research object,deeply studies the reaction mechanism of the smelting process,and establishes a mathematical model of the smelting process based on metallurgical physicochemical theory and thermodynamic heat transfer knowledge;based on the mathematical model,explores the use of internal mode control and optimization methods to control the smelting endpoint;finally,according to the actual smelting process needs to control the characteristics of temperature and carbon content dual output Finally,a multivariate inference control method based on expert system is proposed,which improves the robustness of the system,shortens the smelting time and enhances the quality of the smelted products.In summary,the main research completed in this paper is as follows:(1)The relationship between four smelting indexes,namely carbon content change in the reaction fluid,furnace temperature change,oxygen supply rate and argon supply rate,was studied in the production process flow and smelting process mechanism,and a mathematical model was established.(2)There is the current carbon content as well as temperature online monitoring technology as the basis,combined with the established mathematical model,the study of internal mode control method,the established mathematical model to take the inverse and series filter,the construction of the internal mode controller,to solve the problem of disturbance unmeasurable,but the method in the use of the controller saturation problem will occur.(3)In order to solve the above problems,an expert anti-wind internal mode control method for low carbon ferrochrome smelting process by AOD method is studied.The original internal mode controller is split and designed as a combination of a feedforward controller and a feedback controller to achieve compensation,and the filter time constants are selected according to different smelting states in combination with the expert control method.When this controller is used,the final smelting end point carbon content can achieve the expected target.(4)In order to achieve better control performance,a multivariable inference control method is proposed,in which the oxygen supply rate and argon supply rate are regarded as input quantities together,and the carbon content change rate and furnace temperature change rate are regarded as output quantities,and a V-shaped multivariable inference controller is designed.Under this control method,the furnace temperature can be controlled,but the smelting time is long due to the constraint of its middle filter time constant,which is not consistent with the expected goal of reducing the smelting cost.(5)To shorten the smelting time,expert control was added to the multivariate inference controller,and the control process was divided into five parts,and the filter time constants used in each stage were obtained to make the control system have faster response speed,which effectively shortened the smelting time while retaining the furnace temperature control effect.Finally,a centralized control system for smelting low carbon ferrochrome alloy by AOD method was built according to this method.According to the simulation and actual smelting results,the system shortened the smelting time by 9.53 %compared with the general method,and the furnace temperature was controlled below 2000 K,which achieved the expected goal.