Model Development of Additives Dissolution in the Bof Process

Abstract

Since the beginning of BOF process, slag formation has been subjected to extensive development. During the initial stages of the blow, fast slag formation is primordial for the process performance. This is mainly to allow oxidizing reactions, and also to protect the refractory. A modeling of BOF process for the purpose of process optimization requires precise knowledge concerning the dissolution of CaO and MgO based materials. Using this knowledge, the optimal process conditions can be ensured by a controlling of the slag formation during the converter steelmaking process. Taking into account an application of large amount of different raw materials, as well as location-specific process conditions, the characterization of the dissolution behavior of different additives is an important key to improve the technological process. Thereby, in the frames of this project, an appropriate model for slag formation is established and compared to operational results for a 330t BOF, operating at ThyssenKrupp CSA, Santa Cruz, Brazil.

Application of mass and energy balance in oxygen steelmaking

“…Equilibrium phase diagram relation: The saturation limit of MgO dissolution at 1600°C is computed via an empirical fit to an equilibrium phase data [10] expressed using Equation (10). For tap temperature above 1600°C, the equation developed by Carvalho [12] given by Equation ( 11) is used.…”

“…where PCR:Post Combustion ratio (12) The details of the iterative loop and associated calculations involved in the static mass balance model are described in the recent paper [8] using a flowchart. With the converged solutions, the model proceeds to consider the heat balance.…”

General mass balance for oxygen steelmaking

“…Previous studies [37,41] reveal that the assumptions like steady-state process, deterministic model, complete oxidation of silicon, complete utilization of oxygen and no oxygen presence in hot steel do not impair the accuracy of the solution. Considering the different types of variables and assumptions, the elemental mass balance equation can be written in the form: The simultaneous control equations formulated using the mass of hot charge, hot steel and slag are coupled via empirical relations represented as Equations (9–17) [1,8,13,23,42,43]. The mass balance model considers the final mass percentage of carbon and phosphorus in steel, hot charge mass and scrap mass as the input.…”

“…The saturation limit of MgO dissolution at 1600°C is calculated from Equation (16) that is derived from an empirical fit to an equilibrium phase data represented in Figure 4 [9] for FeO percentage ranging from 20 to 30%. For tapping temperature above 1600°C, the amount of MgO dissolved in the quaternary slag containing CaO–FeO–SiO 2 is calculated by Equation (17) developed by Carvalho [43] that depends on the tapping temperature. Further calculations inside the iteration loop are carried out by solving the simultaneous Fe, Mn and P mass balance equations along with the semi-empirical relations.…”