Basic Theory And Application Research On Predictive Model For Steelmaking Process In Combined Blowing Converter

The process of converter smelting involves many complex phenomena such as the flow,mass transfer,heat transfer,melting,and chemical reactions of gases,liquids,and solids between steel,slag,and furnace gas.Establishing a predictive model that is consistent with the actual reaction kinetics and smelting laws is of great theoretical significance and application value to achieve stable control of the converter smelting process and hitting the smelting endpoint.This article analyzed the mixing and stirring characteristics of the melt pool under different blowing regimes through numerical and physical simulations,and obtained a kinetic energy model for converter stirring.By studying the laws and mechanisms of converter smelting process,a model of three converter reaction zones（impact zone,emulsification zone,slag zone）and a coupled thermodynamic and kinetic reaction interface model were established;A predictive model for converter steelmaking process was built using Visual Studio,Microsoft SQL Server,and OPC software;The industrial application results indicated that the model can guide the production of converter smelting.The main tasks were as follows:（1）Research on dynamic stirring law of converterThe smelting and blowing system of the converter was the key factor affecting the changes in the reaction law of the molten pool.The position of the oxygen gun,the flow rate of the oxygen gun,and the bottom blowing flow rate at all times affected the velocity field,turbulent energy,and mixing effect of the converter molten pool.At the same time,it was also the key factor determining the smelting reaction efficiency of the impact zone,emulsification zone,and slag zone of the converter.The research results indicated that as the height of the oxygen gun decreases,the flow rate of the oxygen gun increases,and the intensity of the bottom blowing gas supply increased,the average velocity and average turbulent kinetic energy of the cross-section of the molten pool both increased;The fluctuation range of the mixing intensity of the molten pool with the flow rate of the oxygen gun,the position of the oxygen gun,and the bottom blowing intensity was 4%～8%;The relationship equations between stirring energy,mixing time,and turbulent kinetic energy wereτ_mix=440·ε_Z^-0.4 and k=（3.5～5.4）×10^-6·ε_Z.（2）Research on the three zone model of smelting reaction based on stirring dynamicsOn site sampling revealed that the converter melt exhibited obvious synchronous characteristics of FeO accumulation and consumption,an equilibrium state in the reaction interface layer,and the slag formation route was influenced by the low melting point slag phase.A calculation method for dividing the melt into three reaction zones and transforming the oxide carriers in the three reaction zones was used to establish an oxygen distribution model that dynamically matches the actual blowing and feeding systems and conforms to the metallurgical laws of the converter melt.The dynamic oxygen distribution range of the three reaction zones was:15%～20%:45%～55%:40%～25%.（3）Study on the coupled reaction model of thermodynamics and dynamicsThe coupling analysis method of thermodynamics and dynamics was used to study the oxygen distribution of steel components at the reaction interfaces in three reaction zones,including activity calculation,thermodynamic analysis,kinetic analysis,coupled reaction mechanism,"scrap steel liquid"melting model,"liquid slag molten slag"slag slagging model,and material system analysis.The key control point of the reaction interface model was to establish a normalized analysis of the equilibrium state of the reaction interface,that is,the reaction interfaces a_（CO）of the three reaction regions have different states,a_[O]ranging from20 to 60,1 to 3,and 0.05 to 0.2,respectively,the equilibrium state of the reaction interface can match the limit values of various elements in the actual smelting process of the converter.In addition,research on multiple reaction products of the same element has found that over94%of the oxidation of carbon at the interface of the molten pool reaction is due to CO reaction;More than 99%of the oxidation of steel components[Fe]generates（Fe O）.（4）Development and application of a predictive model for steelmaking processVisual Studio,Microsoft SQL Server,and OPC software were used to build a converter steelmaking process prediction model for three reaction zones,and practical applications were achieved.Research has shown that when the equivalent stirring energy of the melt pool was 0.6～0.75,the corresponding change range of the equivalent mass transfer coefficient at the reaction interface was 1.019～1.024;In the middle and later stages of smelting,the oxygen distribution in the"slag steel liquid（metal droplets）"reaction zone accounted for 25%to 35%,while the oxygen distribution in the"gas steel liquid"jet impact zone and the"slag metal droplets furnace gas"emulsification zone accounted for 15%to 20%and 47%to 55%,respectively.The equilibrium w（[C]）of the reaction interface in the slag zone showed a trend of first increasing and then decreasing,with a smelting endpoint of around 0.03%;The increase of equilibrium w（[Mn]）and equilibrium w（[P]）at the reaction interface in the slag zone was the thermodynamic basis for the"manganese and phosphorus recovery"of molten steel during the smelting process.The oxygen distribution of molten steel[C]stabilized at around 40%in the early stage of smelting,and rapidly increased to 100%in the middle stage of smelting.The decarbonization rate in the middle stage of smelting was affected by the reduction rate of slag（Fe O）.The endpoint of smelting decreases with the mass transfer rate of[C],and the oxygen distribution of[Fe]in the molten steel rapidly increased to around70%.（5）Research on accurate prediction of carbon content at the end of smeltingThe parameter improvement algorithm based on the mechanism model,including dynamic fitting of limit carbon content,real-time driving of melt stirring energy,normalization treatment of multiple reaction zones,and dynamic optimization of equivalent mass transfer coefficient,has achieved the following results in predicting the carbon content at the endpoint of smelting in different steel plants:the dynamic correction of the 210 ton top and bottom combined blowing converter in a certain plant was sub gun detection,with a target carbon content of 0.06%.The predicted carbon content has a±0.01%hit rate of 69.4%,a±0.015%hit rate of 86.9%,and a±0.02%hit rate of 96.0%.