Ajay Kumar Shukla

COREX is one of the commercial smelting reduction processes. It uses the finer size ore and semi-soft coal instead of metallurgical coke to produce hot metal from iron ore. The use of top gas with high calorific value as a by-product export gas makes the process economical and green. The predictive thermochemical model of the COREX process presented here enables rapid computation of process parameters such as (1) required amount of ore, coal, and flux; (2) amount of slag and gas generated; and (3) gas compositions (based on the raw material and desired hot metal quality). The model helps in predicting the variations in process parameters with respect to the (1) degree of metallization and (2) post-combustion ratio for given raw material conditions. In general reduction in coal, flux, and oxygen, the requirement is concomitant with an increase in the degree of metallization and post-combustion ratio. The model reported here has been benchmarked using industrial data obtained from the JSW Steel Plant, India.

The scrap dissolution in an actual process like the BOF is affected both by mass transfer and heat transfer. In this paper, the mass transfer of carbon in liquid melt is considered along with heat transfer. The approaches used in this paper to model the scrap dissolution phenomenon include the application of Green's function, quasi-static, integral profile, and the finite difference approach for different Biot numbers. Mass transfer coefficients are calculated using the Chilton-Colburn's analogy for the case of forced convection. Since the quasi-static approach requires the least computational time, it is used for a detailed parametric study, including the effect of other parameters like different scrap ratios and heating rates of liquid melt. The region of control of heat transfer vs mass transfer is also identified. The dissolution of mixed scrap (light and heavy scrap) is investigated for different scrap ratios and the autogenous heating rates of liquid melt, with the help of mathematical models. The heat transfer coefficient is estimated as a function of mixing energy and the mass transfer coefficient by invoking the Chilton-Colburn analogy. The permissible limits of light scrap, which can be charged into the BOF, are also suggested from the results of this model. The Artificial Neural Network (ANN) model is trained on the dataset (patterns) generated by the coupled heat and mass transfer model. The accuracy of the results obtained using different ANN topologies is discussed followed by a recommendation for selecting the best approach. © 2013 The Minerals, Metals & Materials Society and ASM International.

The decarburisation process is studied with the help of mathematical modelling of RH degasser with reaction interface area approach, considering multi-component mixed phase mass transport theory. An algorithm is developed by considering Ar gas, bath surface and CO gas bubbles as the reaction sites for decarburisation process. On the basis of this, the model is developed using MATLAB. The model is tested with five sets of data which are obtained from JSW Steel Plant Ltd. The results obtained from the model have been compared with the industrial data as well as the data obtained from literature survey. It is shown that the nitrogen and hydrogen removal are triggered more for higher CO evolution rate. The relations between carbon removal and factors like area of interface, time and vacuum pressure are proposed.

Steel plants generally employ static BOF end point control models to arrive at a given temperature and chemistry at the end of blow. These end point models have now been supplemented with chaos control models to steer the blowing process in the right direction while the blow is in progress. Merely arriving at the correct end point temperature is however not adequate because in the subsequent stages as well the temperature variations can be large and unpredictable. The present paper deals with an integrated model to take into account the effect of all parameters affecting temperature and composition from tapping to the start of casting to minimize the use of LF or aluminum heating, and also minimize grade mixing. The application of lean operations strategy is explained in which the previous "Push System' is changed to a "Pull System", minimizing the use of ladle furnace or aluminum heating during steelmaking.

The simulation of the basic oxygen steelmaking process was conducted, incorporating transient compositions, temperature, and weight of liquid steel and slag. The simulation utilized a 3-reactor model that considered the thermodynamics of chemical reactions and the kinetic limitations governed by mass transfer. Additionally, the kinetics of scrap dissolution were taken into account. To describe the different parts of the combined blown oxygen steelmaking converter (top and bottom), three interconnected adiabatic reactors were employed. The refining reactions of the basic oxygen steelmaking process were perceived using the macro programming facility of FactSage™ software. Based on the model, the scrap dissolution time was determined to be 510 s, 400 s, and 300 s for scrap radii of 0.25 m, 0.18 m, and 0.14 m, respectively. The model’s predictions aligned well with the plant data regarding the removal of carbon, silicon, and phosphorus with respect to blowing time.

An improved computational model to describe the decarburization process in basic oxygen furnaces for steel making is presented in this work. A dynamic model was thus developed to calculate the decarburization rate and its breakup as a contribution coming from the hot-spot zone (under jet impact) and emulsion zone (by droplet and slag reactions). In this work, multiple interconnected equilibrium/adiabatic stoichiometric-reactor-based approaches are used to describe the overall basic oxygen steel-making process. The macroprogramming facility of FactSage™ software was used to understand the thermodynamics and kinetics of basic oxygen steel-making processes. The temperature, compositions, and volumes of various phases are estimated with the use of this model. Hot-spot temperatures in the range from 2000 to 3000 °C as a benchmark was considered for calculations. The major contribution of decarburization was established to come from hot-spot reactions in the major part of the blow, except in the last part when emulsion phase reactions govern it. This development represents an original contribution to our understanding of the BOF steel-making process.

The influence of Al2O3 in the range of 10–20 mass% and TiO2 in the range of 0.55–5 mass% on the flow behavior, viscosity, density, and surface tension of molten industrial blast furnace slag with CaO/SiO2 = 1.13 is investigated using a high-temperature microscope, a rotating viscometer, and the maximum bubble pressure method. The measurement results show that Al2O3 acts as a network former in the studied CaO–SiO2–MgO–Al2O3–TiO2 slags. With an increase in the Al2O3 content from 10 to 20 mass%, the viscosity and surface tension of the slags increase and the density decreases. In contrast to Al2O3, the TiO2 acts as a surfactant and network breaker in the range of up to 15 mass%. The addition of TiO2 up to 15 mass% results in a decrease in the viscosity in the liquid-dominated region and a decrease in the surface tension of the studied slags. Therefore, the density increases with the addition of TiO2 due to increasing molar volume. The behavior of the breakpoint temperature on all the viscosity curves is in complete agreement with the behavior of the flow point temperature and crystallization temperatures of melilite and perovskite.

The phosphorus partition between the unkilled liquid crude steel and the high basicity (CaO/SiO2 = 4.2), basic oxygen furnace (BOF) slags with varying compositions of Al2O3, TiO2, and MnO is studied at temperatures 1600 and 1650 °C. The tests are conducted in both “slag-to-metal” and “metal-to-slag” directions and for durations of 30 and 60 min. The measured results are compared with the values reported in literature and found to be in good agreement with some of them. It is found in the investigation of high-basicity BOF slags, that Al2O3, MnO, and TiO2 lower the phosphorus partition. The phosphorus partition increases with increasing optical basicity. The phosphorus partition shows a maximum when the FeO content is in range of 25–30 mass%. The MgO content slightly increases the phosphorus partition.