Modern Hot Metal Desulfurization

juvenile Hot Metal De reciprocal ohmizationModern Hot Metal Desulfurization And Dephosphorization TechnologiesIntroductionThe purpose of phosphorus and sulfur removal is to decrease the closeness of these particles along with the undesired inclusions (oxides, borides, nitrides, carbides, and chlorides) to accomplish the final clear quality requirements 5. Dephosphorization involves low temperature, amply slag basicity (CaO/ SiO2 ratio) and high oxygen natural action whereas desulphurization entails high temperature, high slag basicity (CaO/ SiO2 ratio) and low oxygen activity. Initially, dephosphorization was per tiered by the appurtenance of iron ores in the blast furnace runner. Soda ash (Na2CO3) was used in the blast furnace house during desulphurization. Subsequently, dephosphorization was advanced by the subsurface shooting of reagents in vass, such as torpedo or submarine cars. Desulfurization was enhanced by co-injection of lime and magnesium into the importunate alloy transfer ladles 6. The following dephosphorization and desulphurization technologies atomic number 18 reviewed1. Dephosphorization by the multirefining converter (MURC) process2. Dephosphorization using CaO aggregates3. Desulfurization by atomic number 124. Desulfurization by flux injection using a new kinetic feign5. Desulfurization by the CFD modal valueling1. Dephosphorization By The Murc ProcessThe multirefining converter (MURC) process claims to improve the ability of the dephosphorization procedure by reducing the cost and minimizing the slag volume. It is a new acid surface pretreatment in which dephosphorization and decarburization processes are real in the same converter for further reduction of the decarburization slag.The MURC process reduces the measuring stick of slag by 50 % in comparison to the conventional pretreatment processes (30 %). The decarburization slag is ceaselessly recycled (Figure 1). A low basicity dephosphorization slag is discharged fro m the MURC overdue to the high amount of total iron in the slag (T Fe) and no desiliconization treatment of the caustic surfacelic element. This results into a valuable utilization of the dephosphorization slag in the steelmaking process.2. Dephosphorization Using Cao AggregatesThe polyphase dephosphorization slag is analyzed through the addition of calcium ferrite flux pulverize into hot metal. It is detect that high Si content (0.15 %) shows a similar CaO cleverness for dephosphorization than low Si content (0.00 %). The low Si content exhibits calcium phosphate (3CaO.P2O5) whereas high Si content shows a combination of calcium silicate (2CaO.SiO2), and calcium phosphate. The formation of these hearty phases explains a similar CaO efficiency under different Si content.3. Desulfurization By MagnesiumDesulfurization is enhanced by the stirring effect of Mg bubbles in the hot metal. The answer speeds up by the addition of lime and CaC2. These desulfurization reagents were te sted in ArcelorMital Indiana Harbor. The typical inclusions before reagent injection were TiC and MnS. TiO2 is added to protect the graphite veneer in the blast furnace. MgS + TiC and MgS were the most sponsor inclusions after the reagent injection. MnS inclusions were not observed after this stage. This means, most of these inclusions floated up at the end of desulphurization. Further profit of desulfurization can be achieved by Al addition. The latter reacts with lime to form lower melting point calcium aluminates.4. Desulfurization By Flux dig Using A New Kinetic ModelDesulfurization is performed by introducing grind reagents (CaO, calcium carbonate, calcium diamide carbonate) into the hot metal using either union wired or a carrier flub (nitrogen). This creates a composite plant variety of interfaces in torpedo ladles (Figure 2) 7. There are two response modes that are present in the heterogeneous/ immiscible phases. The first mode is related to the flying reaction am ong the liquid steel and pulverization particles. The second mode is the permanent reaction between the slag on the surface and the molten steel.Desulfurization in torpedo ladles. The interfaces are (1) Jet regularise (2) bubbles and particles rise in the plume regularize (3) bubbles emerge in the uncovering zone (4) slag zone (5) gas-slag-metal emulsion forms in the dispersion zone (6) metal reacts with lining in the lining zone (7) lowest stirring intensity in the intermediate zoneSeveral parameters influence the desulfurization of hot metal and are addressed by a new model of submerge pulverization injection. The total amount of the flux is con fontred to be liquid at steelmaking temperature and the injection rate along with the time lapse can be determined. The total sulfur removal rate for both the permanent fill (top slag) and transitory (injection powderise) mode is obtained by the following equation,The right hand side of the reaction is related to the transitory re action. This equation is only useful during the powder injection. After that, the right hand side becomes worthless.sulphide solubility in slag is restricted. Once the sulfide solubility limit is collide withed, a unpolluted sulfide phase grows within the slag to absorb the excess of sulfur. Sulfide saturation may occur before the slag and metal reach equilibrium. The speed of the reaction is reduced until the sulfur content is dropped. Excess of sulfur in permanent reactions produces a reversion reaction and further desulphurization cannot occur. The transitory reaction removes the excess of sulfur by the continuously addition of sporting powder into the torpedo ladle. It is also recommended to deslag after powder injection.Figure 3 is divided into % S wt % and reaction rate. The experimental results are obtained from the 20 CaO-60CaF2-20Al2O3 (by weight) powder injection under an argon atmosphere into 3.4-3.8 kg cast iron at 1310 C. Once the slag (permanent-contact reaction) ex periences an excess of sulfur at 420 s, the sulfur concentration decreases continuously until 950 s. The contributions of the permanent and transitory reactions are also displayed. The permanent reaction increases with time until it is saturated. The transitory reaction never approaches to saturation conditions. The difference between these two reactions is not significant large. Therefore, the contribution of these both reactions is generally equal.5. Desulfurization By CFD ModelingSynthetic slag is used on the desulfurization process due to its reuse in several treatments. The sulfur is transferred to the synthetic slag followed by slag novelty. Slag regeneration is performed by the oxygen injection to produce gaseous sulfur dioxide (Equation 3). The sulfur distribution also differs from the slag and the metal once desulfurization begins (Figure 4). A porous plug at the bottom of the vessel is used to inject nitrogen in the hot metal. The fluid hurrying is increased to optimize the desulfurization rate to improve sulfur transport. Therefore, CFD analyzes the desulfurization and slag regeneration processes to optimize the plug position and calculate the drift velocity of gas bubbles, desulfurization rate, among other parameters, for future design of desulphurization processes.ConclusionsMultirefining converter (MURC)(1) Dephosphorization and decarburization are carried out in the same converter, reducing the slag volume for better industrial, economical and environmental purposes(2) The dephosphorization efficiency is increased by greater amounts of CaO to produce solid phases, such as 3CaOP2O5 and 2CaSiO2Desulfurization by Mg(1) TiC particles are nucleation sites for MnS and MgS(2) MgS inclusions are the most frequent particles after the reagent injectionDesulfurization by flux injection using a new kinetic model(1) A new model is developed to evaluate and identify separately the transitory and permanent reactions(2) This model helps to predict the excess of sulfur to avoid reversion of it in the hot metal(3) The contributions of the transitory and permanent contact reactions are observed to be in a similar proportion, concluding equal influence in the powder injection techniqueCFD Modelling(1) The desulfurization and slag regeneration are successfully modeled using thermal and transport mechanismsReferences1 S.Y. 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