Research On Low-phosphorus Steel Smelting Process Using Limestone In Converter

Based on the "12.5" national science and technology support project "direct use of limestone slag steelmaking technology and equipment demonstration", project number: 2012BAC27B02,the key technology of smelting phosphorus steel with converter using limestone was reasearched in this study.In the current steel production, slagging technology is a process of critical operating unit in steelmaking process, directly related to the smooth and efficient completion of the smelting process and dephosphorization and decarbonization and other metallurgical tasks. For a long time, the converter steelmaking process is using lime as slagging material, smelting result is stable and efficient. But the lime is from calcination of limestone, CaO utilization is low, resulting in a waste of resources. And also in the lime production process, needing to go through "high-temperature calcination-cooling conveyor-heating slagging" then the lime can be used for converter steelmaking process, the calcination process spend a lot energy, the cooling process cause waste of heat. In the lime kiln calcination process will generate a lot of dust and SO2, NOx, pollute the environment. Using Limestone instead lime to slag in the smelting process, can make high energy consumption and serious pollution of the calcination process move to the converter, which can effectively solve these problems reducing the influence on resources, energy and the environment.In recent years, slagging of limestone for steelmaking production has stabilized, but the process of using limestone to product low phosphorus steel smelting has not yet been reported.This thesis established a analytical model of limestone steelmaking material and energy change to study the effect of different materials added to the amount of energy converter steelmaking process. Found using limestone steelmaking, using all the limestone slag can meet the requirements of the heat of steelmaking process. Using different structures and different ratio of limestone feed ratio to test 103 furnace smelting in 60t converter, compared to steel material consumption with different ratio of raw materials structure, the cost of production, oxygen consumption and gas generation analysis, found that when using the molten iron as raw materials, recycling of steel slag and lump ore as cooling agent, the steel material consumption and smelting cost are lowest.For the study of the influence of hot metal composition to the whole limestone dephosphorization steelmaking, founding with the increasing of iron and manganese content, the end dephosphorization slag MnO content, phosphorus distribution ratio increases, which is advantageous to slag and dephosphorization reaction, and the dephosphorization efficiency can be improved.Using Factsage software to analyze the effects of the slag melting point with different MnO and FeO content, designing the whole limestone steel dephosphorization period and the decarbonization slag composition, and make the hot experiment to verify. It found that in line with design expectations.Studying the influence of oxygen system to limestone dephosphorization steelmaking, the effect of oxygen blowing system on converter bath kinetic was studied by numerical simulation, in the 60t converter has carried on experimental study on the influence of the different lance position to the whole flow of limestone steelmaking dephosphorization bath temperature, slag FeO content, time of slagging and dephosphorization ability,which optimizing the oxygen supply system.On this basis, the 60t converter was carried on whole limestone phosphorus steel smelting industry tests. Compared with the use of steel-making lime, the process of using the limestone to slag steelmaking that energy saving effect is remarkable, saving the amount of limestone, considerably reducing BOF limestone resource consumption; save energy, reduce emissions CO2; reduce SO2, NOx and flue gas emissions, in favorite of protecting the environment. Endothermic decomposition of limestone and produces CO2 can improve the dephosphorization thermodynamic and kinetic conditions, improve the dephosphorization rate, reduce destination liquid steel carbon and oxygen product reduce, meet the quality requirements of low phosphorus steel, reduce production costs.Through this study, mastered basic data and key technology of converter smelting low phosphorus steel with limestone process, provided ideas and learn for conserving resources and protecting the environment, cost-efficient smelting converter.