Study Control System Of Carbon Content In AOD Furnace And Converter Based On Bottom Gun

Metallurgical industry is a national basic industry.In order to ensure the quality of ferrochrome,shorten smelting time and reduce blow rate,further research on smelting process is needed.The carbon content of molten iron is one of the most important parameters in metallurgical production and is the target parameter for making production process.It is of great significance to study the control strategy of end-point carbon content.The objective is to take the smelting process of low-carbon ferrochrome as the specific research object,establish a mathematical model of the production process of low-carbon ferrochrome on the basis of in-depth analysis of the smelting process mechanism,and study the control strategy of carbon content in the smelting process and smelting endpoint.Based on the above objectives,the main research contents completed in this paper are as follows:1.The process of refining ferroalloy with argon and oxygen introduced in this paper is that after high carbon ferrochrome is melted in electric arc furnace,it is directly mixed into AOD furnace for blowing,and argon and oxygen mixed gas is blown at the top and bottom.Oxygen blowing at the top of hyperbaric oxygen lance makes molten iron decarburize fast,which can shorten smelting time and improve production capacity.Different proportions of oxygen and argon mixed gas are blown through the bottom lance to reduce partial pressure of carbon monoxide,so that decarburization reaction is carried out in a positive direction,thus achieving the purpose of carbon reduction and chromium preservation.2.The coupling relation of parameters such as gas supply rate and oxidation reaction rate is studied,and the mathematical model between oxygen supply rate and decarburization rate of molten iron is established.The mathematical model between the argon supply rate and the decarburization rate of molten iron is established by using the grey system modeling method.The model can cooperate with basic level automation to automatically control the oxygen supply flow in the whole decarburization process,adjust the oxygen supply flow in time according to the calculation results of the model,improve the hit rate of end-point carbon content,avoid the peroxidation of chromium in molten iron,and achieve better decarburization effect.3.Based on the detectability of carbon content,the internal model control strategy of carbon content is researched and designed.Internal model control solves the problem ofmeasurable output and unmeasurable disturbance.Through establishing process model and designing controller,the carbon content of molten iron can be controlled.4.Due to the high price of the on-line carbon content detection equipment and the strict requirements on the environment,the internal model control strategy is not applicable in practical application at present.To solve this problem,a carbon content inference controller is designed.Based on the estimation model,the oxygen flow rate is selected as the secondary output and the carbon content of molten iron is selected as the main output,and the estimator and inference controller are designed.5.Finally,the dynamic and static performances of inference control and internal model control are analyzed by MATLABA simulation.The simulation results show that when the carbon content is set at 0.5%,when the filter time constant is 800,the internal model control adjustment time is 40 minutes,and the smelting time is 76 minutes,the system is stable regardless of the model error.However,the inference control adjustment time is 40 minutes and the smelting time is 76 minutes.When the model is accurate,the system is stable and has no difference.When the model is mismatched,the maximum deviation of the system is 0.11%,which can also meet the actual engineering needs and save expensive on-line carbon content detection equipment.Finally,an AOD furnace endpoint carbon control system based on DCS system is designed and implemented.