Study On Process Optimization Of Hot Metal Pre-treatment In CISC

With increment of steel variety and improvement of quality requirements ,the hot metal desulfurization has become incapable of shortness procedure for steel production, which realizes prerequisite of economic steelmaking and was one of most effective technology of perfect steel production precess.The main problems of pre-treatment desulphurization of Chongqing Iron & Steelmaking Co.Ltd. were investigated, such as the lime-based(90%CaO+10%CaF2) and the Magnesium-based (90%CaO+10%Mg) desulfurizers and desulphurization technological parameters, the excessive consumption of desulfurizing agents, causing the sophisticated procedure, large quantities of heat drop, slag-off, ferrous loss, as well as the influences in the material flow structure of the whole steelmaking shop and production of high-quality steel.According to the calculation of the thermodynamics and kinetics of desulphurization and characteristic of desulfurization in Chongqing Iron & Steelmaking Co. Ltd. more Magnesium contents are added for desulphurization, shortening the process temporal hours and decreasing the heat drop, so as to meet the need of practical production. Generally,the desulphurization process of Magnesium-based desulfurizer, the influence of the surfacial properties of the slag to desulphurization were analyzed. hence several problems are generated, for example, poor fluidity and the aggregation of the slag, more iron content in desulfurized slag. So a certain kind of modifying agent is added into the desulfurizing slag to improve its performance and reduce the ferrous content loss. The composition and the quantities of the desulfurizer and modifying agent as well as other technological parameters were analyzed theoretically. Finally, the desulfurizers, with 15% and 20% of the Magnesium element separately and optimized technical parameters were chosen in the industrial experiment. The main results were as follows:①According to theoretical analyses and calculation, the time needed was 228s if the sulfur element content decreased from 0.032% to 0.005%, however while the blowing time was much lower in practical procedure and was approximately 300~400s, so Nitrogen was added for about 0.5~1min in order to promote string and the rising of powder and the reactant. other technological parameters were as follows:Baiting speed:40~50Kg/min;Aperture of larynx diameter:10mm; Inserting depth:200~300mm.②The relatively optimizational formulation and the consumption were obtained in the plant experiments, which were 80%CaO, 15%Mg, 5%CaF2 , the consumption was reduced from 6~8Kg/t with 10% Magnesium to 3.5~4Kg/t for desulphurizer.③According to theory and relative experiment and industrial trial,modifying agent contained 15% Magnesium and SiO2 44.58%,Al2O3 2.223%,Na2CO3 19.36%,CaF2 17.5%,K2O+Na2O 6.899%, the consumption was 40~80Kg/ladle .④The average periodic time of desulphurization was approximately 19.95min after optimization and the average periodic heat drop of desulphurization was approximately 19.38℃after optimization. The sulfur content of the pre-treat ment of the hot metal after optimization was less than 10×10-3%, the average desulphurization ratio was about 80%.The metallic iron content was reduced from 70~80% of the desulfurized slag with 10% Magnesium to 30~50% which contained 15% Magnesium.