Study On The Technology Of High-Value Utilization Of Carbon Precipitation At Ironmaking-Steelmaking Interface Due To Temperature Drop

The steel industry is an energy-intensive and resource-intensive industry.Due to the large scale of production and complex process,the production of iron oxide-containing solid wastes in steel plants is very large and it is quite costly to process.At the ironmaking-steelmaking interface,during the transportation of molten iron through the torpedo tank,a large temperature drop will occur due to the long time transportation.Since the temperature of the molten iron drops,the carbon in the molten iron will be supersaturated to form flake graphite,floating in the air,furthermore,causing severe air pollution.In order to solve the environmental pollution caused by carbon precipitation at the interface of ironmaking and steelmaking,and to utilize the solid wastes from the steel plant,the iron oxide-containing solid wastes are charged into the torpedo tank for the oxidiaion of carbon that is possible precipitation.It brings the benefits of environmentally friendly and recycling of iron from the solid wates.In this paper,the oxidation reaction order of carbon and silicon in the molten iron has been determined by the thermodynamic calculation under the original operating conditions of torpedo tank car.The results show that the transition temperature for the changing of oxidation order of Silicon(Si)and Carbon(C)is 1477?,that is,when the temperature is higher than this temperature,carbon is preferentially oxidized,but when the temperature is lower than this temperature,Si in molten iron is preferentially oxidized.Under the laboratory conditions,five kinds of solid wastes containing iron oxide were selected as oxidants:LT dust of converter,oxide scale on hot rolled strip,blast furnace dust electric furnace dust and secondary dust of converter.The experiments of decarburization of molten iron were carried out under different feeding order,different additive amount and different temperature to explore the application effect of solid wastes containing iron oxide in the molten iron.The experimental results show that the reaction of powdery dust is more violent,and the splashing phenomenon is more serious.The utilization ratio of the powdery dust is only about 75%.LT dust and electric furnace dust have better effect than other solid wastes on the reduction of carbon and the iron recovery.The blast furnace dust contains high C,so that the mass fraction of C in molten iron does not decrease,but goes up.Therefore,the blast furnace dust is not suitable for the direct application.The secondary dust of converter has lower iron oxide content resuling in a poor application effect.When the adding amount of the secondary dust of converter changes from 2%?5%of the total mass of molten iron,the C content in the molten iron can only be reduced by 0.05%?0.12%.Furthermore,based on the high temperature experiments,the static model of material balance and heat balance is established for the torpedo tank car system.The influences of the different kind of iron oxide-containning solid wastes and different adding amount on the carbon reduction,iron recycling,slag generation,gas generation and final temperature of molten iron are determined by the analysis with the static model.The calculation results show that adding scrap steel to the torpedo tank car can reduce the precipitation of carbon and significantly increase the production of molten iron,but this operation causes a great temperature drop of molten iron.The process of using scrap steel with iron oxide-containing solid waste is better than using scrap steel or solid wate only,which can not only make full use of the carbon in the molten iron,but also reduce the production of exhaust gas and slag.In addition,the iron element in the scrap and the solid wastes can be recycled and the output of the molten iron can be greatly increased.Based on the analysis of using the five kinds of solid waste as raw materials,the LT dust of converter and the electric arc furnace dust have better application effects on the highvalue utilization of carbon precipitation at the ironmaking-steelmaking interface.