Study On Kinetics Of Hot Metal In-situ Desulfurization By Magnesite Based Desulfurizer Electrolytic Reduction Process

In the modern steel production process, the hot metal pretreatment process is overall already universal in steel business enterprise because of its outstanding advantages. The application of hot metal pretreatment technology relieves the converter steelmaking process from the onerous impurity removal tasks like desulfurization and dephosphorization. So the hot metal pretreatment technology is playing an irreplaceable role in the modern steel production industry. The desulfuritzation of pig iron by magnesium is one of the most widely used hot metal pretreatment desulfurization technology. But the special properties of the magnesium as animation alkali metal raise the burden of the use.The innovations of molten salt electrochemistry technology provide some new ideas to use the magnesium, that is to say, it is maybe feasible to use the magnesite resource, which is abundant in Liaoning Province, to desulfurize the pig iron in hot metal pretreatment process directly by high-temperature molten salt electrochemistry methods.The research takes the feasibility of use magnesite to desulfurize pig iron carry on the discussion and give the possible mechanisms and mathematical model in this thesis. This thesis puts forward two different desulfurization mechanisms based on two desulfurization process, which act by two phase of magnesium, liquid magnesium dissolving in the liquid metal and magnesium vapor forming by magnesium vaporization under the liquid metal temperature. For convenience, this two desulfurization processes are called single-phase desulfurization process and multiphase desulfurization process respectively in this thesis. The occurrence and transformation conditions are investigated and discussed in this thesis to research the relation between the electrolytic current and the magnesium action modes and to determine the mechanisms of desulfurization by magnesium. Get the critical current density of the two different desulfurization process by theoretical derivation.Two different mathematical model about hot molten desulfurization using the magnesite by high-temperature molten salt electrochemistry method are established in this thesis based on themodynamics and kinetics of pig iron desulfurization by magnesium and electrode process kinetics corresponding to different desulfurization mechanism. The optimum conditions of desulfurization process are discussed through orthogonal experiments and the results show that the optimum desulfurization condition is0.2A/cm2 current density, 1623 K temperature and 2000 ppm initial sulfur content. The best desulfurization rate is about 24ppm/min under the conditions mentioned above.Then discuss the correctness of the mechanisms and investigate the commonrule each factor influence on desulfurization by controlling experimental variable method, the factors include: electrolysis current density, reaction temperature and initial sulfur content. Making a concrete analysis and discussion on the occurrence conditions of single phase desulfurization and multiphase desulfurization, and the results show some conclusions. The conclusions are as follow: the desulfurization method will change from single phase desulfurization to multiphase desulfurizaiton as the current density rise from 0.1A/cm2 to 0.15A/cm2 under 1623K temperature, the higher the current density is, the faster the multiphase desulfurization take place under the same temperature and the higher temperature it is, the slower the multiphase desulfurization take place under the same current density.In conclusion the results mentioned in this thesis have some degree of guiding significance in developing this new hot metal pretreatment desulfurization technology and promoting the generalization this method to industrial application.