Basic Research On The Behaviors Of Limestone Addition In Oxygen Converter

Directly using limestone for slagging has aroused wide concern with its remarkable effects of energy conservation and cost reduction.Papers published by plants such as Baogang,Shigang,have proved the feasibility and economic benefits of this method.In recent years,many steel plants found that the use of limestone for slagging could achieve better results than lime in actual production process,however some people are still skeptical about this conclusion.So the decomposition behaviors of limestone,dissolution behaviors of limestone,as well as the interaction of CO2 and the molten iron were deeply studied in this paper for explaining the process of "limestone slagging".The decomposition process of limestone in different systems,which were acquired by mixed limestone with different amounts of FeOx,SiO2 or MnOx,were calculated by using thermogravimetric analysis as the detection method.Results show that FeOx.SiO2,MnOx can reduce the decomposition temperature and activation energy of limestone.The mechanism of slag reducing limestone decomposition temperatures can be attributed to the reactions between slag and CaO.which reduces the activity of decomposition product.TG-DSC scanning thermal analysis was used to compare the slagging performance of limestone and activated lime at the micro level.The slag performance of limestone/activated lime was determined by comparing the reaction temperature of slagging and the amount of liquid phase produced.Assimilation experiments were tested by micro sintering machines at the macro level and found that CaO newly decomposed by CaCO3 have higher activity.In view of the phenomenon that limestone can make slag quickly in the actual production steelmaking,the dissolution rate of limestone and lime in converter slag is compared directly under the laboratory conditions.Natural limestone is processed into a specific particle size of the cube.Then heated to a specific size of the lime in the muffle furnace.The limestone/lime of the same particle size were then put into the liquid slag.and the dissolution rate of the limestone/lime was gotten by comparing the intermediate section size of the slag erosion area.Finally.the mechanism of dissolution behavior of limestone/lime in liquid slag and the difference between limestone/lime were analyzed by micro-morphology.The speed of the limestone/lime and the dissolution behavior difference in the slag were compared,and the mechanism of the difference between the limestone/lime was studied.Finally,reaction of CO2 and hot metal was studied by high temperature experiments under the laboratory conditions.The increase of temperature is beneficial to the oxidation of[C]in molten iron,but is not conducive to the oxidation of[Si].The increase in stirring strength and CO2 injection flow will promote the reactivity of CO2 and the elements in molten iron.The thermodynamic calculations show that with the decrease of CO2 partial pressure in molten iron,the Gibbs free energy of the interaction of CO2 with[Si]reduces.As the temperature and stirring intensity increases the utilization of CO2 rises.The utilization of CO2 decreases with the increase of CO2 flow rate.In general,the CO2 utilization produced by the decomposition of limestone is higher than that of direct injection of CO2 into molten iron.