Research On The End-point Control Strategy Of Argon-oxygen Refining Ferrochrome

Ferrochrome alloys are widely used in various industries such as metallurgy,chemical industry,casting,paint,and coating.The content of various elements in ferrochrome alloy,especially the carbon content,plays a key role in the quality of subsequent products,and its smelting end-point control strategy is the key to precisely control the product composition.The key to the argon-oxygen refining ferrochrome endpoint control strategy is to ensure a high rate of impurity removal while keeping the smelting temperature within a certain range.In order to optimize the argon-oxygen refining ferrochrome alloy end-point control strategy and improve the efficiency of end-point control,several aspects need to be carried out: first,to eliminate the influence of sputtering accidents on end-point control.Then,establish an accurate mathematical model to provide an object model for the end-point control strategy.Finally,develop an efficient end-point control strategy to shorten smelting time,reduce raw material consumption,lower waste emission and improve production efficiency.The oxygen supply flow rate,argon supply flow rate,and additive input are the direct factors affecting the smelting temperature and oxidation rate of the elements within the melt,and are also the main causes of sputtering accidents.Therefore,the essence of studying the end-point control strategy of argon-oxygen refining ferrochrome alloy is to precisely control the oxygen flow rate and argon flow rate blown into the furnace by the smelting system,as well as the weight of the additives put in.At present,China's argon and oxygen refining ferrochrome alloy endpoint control still adopts the method of manual experience combined with static models.Because this control method can only pre-set the end-point control of the gas supply flow and additive dosage based on historical experience and smelting objectives to,but cannot dynamically adjust the control parameters based on changes in the smelting state and interference,so this method has the disadvantages of unstable decarburization rate and large fluctuations in smelting temperature,often resulting in sputtering and re-blowing of the endpoint control.Therefore,it is necessary to study a more scientific and accurate argon oxygen refining ferrochrome alloy end-point control strategy to precisely control the smelting temperature and elemental oxidation rate,eliminate the influence of sputtering on the endpoint control,shorten the smelting time,reduce the consumption of raw materials,decrease the rate of metal into the slag,lower the waste emission,and improve the production efficiency.With reference to the current status of research at home and abroad,the study of argon oxygen refining ferrochrome alloy endpoint control strategy still needs to solve three core problems.(1)How to accurately forecast sputtering and effectively suppress sputtering accidents and eliminate the influence of sputtering on end-point control in response to the complex factors generated by sputtering.(2)How to build the end-point control system and establish an accurate mathematical model for end-point control to guide production in view of the high temperature,strong interference and large hysteresis of argon-oxygen refining ferrochrome alloy.(3)How to optimize the end-point control strategy of argon-oxygen refining ferrochrome alloy,improve the end-point control efficiency,and achieve the goal of energy saving and emission reduction in ferrochrome alloy production industry in view of the coupling relationship between gas supply flow and end-point control index.In this paper,the following studies were conducted around the above issues.(1)Research on the influence of sputtering on end-point control and suppression methods.According to the mechanism of sputtering generation,a sputtering prediction method based on wavelet packet decomposition reconstruction filtering and multiinformation weighted fusion is proposed,and a multi-object fuzzy control system is designed to suppress sputtering of argon-oxygen refining furnace.Firstly,according to the signal changes of furnace mouth audio,furnace vibration frequency and melt pool level before and after the occurrence of argon-oxygen refining ferrochrome sputtering,multiple sputtering feature signal detection methods are designed and sputtering feature signals are extracted by wavelet packet signal decomposition reconstruction algorithm;Then,the weighted fusion signal algorithm is proposed to represent the sputtering degree by the fusion signal.Subsequently,a multi-object fuzzy control system was designed to effectively suppress sputtering by controlling the top gun position,adjusting the oxygen supply flow rate and the argon supply flow rate,and controlling the sputtering inhibitor dosage.Finally,the sputter suppression simulation experiments were conducted by MATLAB,which verified that the sputter suppression method has better response speed,stability and sputter suppression effect,and eliminates the influence of sputtering accidents on the smelting endpoint control.(2)Research on argon-oxygen refining ferrochrome alloy end-point control modeling.Firstly,the argon-oxygen refining ferrochrome alloy end-point control system was constructed;then,the physical and chemical reaction mechanism of argon-oxygen refining ferrochrome alloy end-point control was studied,and the mathematical model of argonoxygen refining ferrochrome alloy end-point control based on heat balance and mass transfer theory was established,including the oxidation rate model of carbon,chromium and silicon elements and the temperature balance model of smelting process;finally,simulation experiments were conducted using the end-point control model,and the accuracy of the model was verified by comparing and analyzing the model simulation results with the production test data.The establishment of the mathematical model provides theoretical support for the development of the end-point control strategy.(3)Research on the end-point control strategy based on inferential control algorithm.First,based on the mathematical model of end-point control established in(2),simulation data were obtained;then,the data were used for system identification to obtain the transfer function matrix of oxygen supply flow rate and smelting temperature and the transfer function matrix of oxygen supply rate and carbon content,and the approximate transfer functions of smelting temperature and decarbonization rate were obtained by model decoupling.Then,the oxygen supply rate is selected as the characteristic signal for smelting temperature and carbon content control,and an argon-oxygen refining ferrochrome alloy end-point control strategy based on inference algorithm is designed,and the accurate control of melt pool temperature and carbon content is realized by using the feature of inference control without demanding the object model.Finally,the simulation experiments of temperature control and carbon content control with oxygen supply rate as the control object were completed.The simulation results show that compared with the original end-point control strategy based on the static model,the argon-oxygen refining ferrochrome end-point control strategy based on the inference algorithm has faster response speed and shorter adjustment time,thus demonstrating that the designed end-point control strategy can improve the production efficiency.(4)Research on the end-point control strategy of argon-oxygen refining ferrochrome alloy based on improved inference algorithm.First,in order to eliminate the steady-state error of the system response and further optimize the end-point control efficiency,the structure of the inferential control system is simplified by using the online temperature and carbon content detection results;then,the robustness and anti-interference of the inferential control algorithm is improved by optimizing the filtering time constant with the particle swarm seeking algorithm,and the end-point control strategy based on the improved inferential algorithm for argon-oxygen refining ferrochrome alloy is designed.Then,simulation experiments of argon-oxygen refining ferrochrome endpoint control were conducted to verify that the endpoint control strategy based on the improved inference algorithm has shorter adjustment time and no steady-state error than the endpoint control strategy based on the traditional inference algorithm;finally,the smelting time of the simulated endpoint control was compared and analyzed with the original production data to prove that the endpoint control strategy based on the improved inference algorithm can further improve the production efficiency.