Research On Control Method Of Carbon Content In Argon-Oxygen Refining Ferro-chromium Alloy

This paper takes the argon-oxygen refining process of low-carbon ferrochrome as the research object,analyzes the mechanism of the smelting process,uses the knowledge of metallurgical thermodynamics and kinetics,establishes a mathematical model of the argonoxygen refining process of low-carbon ferrochrome,and uses process control on the basis of it Models and strategies provide certain theoretical support for the process of argon-oxygen refining low-carbon ferrochromium alloys.Based on the above objectives,the main research contents completed in this paper are as follows:1.Through analysis and research on the mechanism of the smelting process,the relationship between the oxygen and argon supply rate and the change rate of the molten iron carbon content in the AOD furnace is given,and the oxygen and argon supply rate and the change rate of the molten iron temperature in the AOD furnace are obtained.The relationship between oxygen supply rate and molten iron decarburization rate,oxygen supply rate and molten iron temperature,argon supply rate and molten iron decarburization rate,and mathematical models between argon supply rate and molten iron temperature are established.2.In the traditional smelting process,the detection of the carbon content in the molten iron often needs to stop the furnace.For this situation,based on the model,select the temperature of the molten iron as the secondary output,and the carbon content of the molten iron as the main output,and design the corresponding PID control It constructs a classic carbon content control method for argon-oxygen refining low-carbon ferrochromium alloys.Because the final carbon content output of this method often has a certain error than expected,the required carbon content target cannot be accurately obtained.3.Aiming at the above problems,the carbon content control method of argon-oxygen refining low-carbon ferrochrome based on internal model control is studied.Take the reciprocal of the internal model,connect the filter in series,and construct the corresponding internal model controller,which can effectively solve the problem of unpredictable external disturbance and achieve steady state error-free.This method controls the process of argonoxygen refining low-carbon ferrochromium alloys,and finally The obtained hot metal carbon content can reach the expected smelting target,but the smelting time is restricted by the filter time constant in the internal model controller,which leads to a long smelting time and low smelting efficiency.4.In order to improve smelting efficiency,a control method combining expert control and internal model control is given.According to actual industrial production conditions,the entire smelting process is divided into five stages,and the filter time corresponding to each stage is calculated In order to adjust the internal model controller of different smelting stages,this method can make the system have a faster dynamic response and effectively shorten the smelting time,compared with the traditional internal model control method.However,at the expense of the steady-state characteristics of traditional internal model control methods,it is difficult to achieve the expected smelting goal.5.Aiming at the smelting accuracy problem of the expert internal model control system,an improved internal model control method is designed.Through the anti-saturation design of the internal model controller,it is decomposed into a feedforward controller and a feedback controller.This achieves the purpose of saturation compensation.At the same time,the expert system table of the anti-saturation controller is established on the basis of the previous expert internal model control,so that the system controller can get effective saturation compensation at different carbon content stages.Compared with the traditional internal model control method and the expert internal model control method,this method has the characteristics of fast dynamic response,short smelting time,high smelting efficiency,and small steady-state error.Finally,an argon-oxygen refining low-carbon ferrochrome DCS system was built with this.Simulation and operating results showed that the system reached the expected smelting target of 65 minutes for smelting time and 0.25% carbon content.