Bolesław Machulec

Selection of Carbon Reducers for the Ferrosilicon Smelting Process

Selection of reducing agents for the ferrosilicon smelting process requires consideration of several difficult to reconcile criteria. The carbon reducers are not only a source of carbon as a substrate of the silica reduction reaction, but also play an important role by acting as a gas filter at the upper zones in working space of the ferrosilicon furnace. Reactivity of carbon reducers to SiO and degree of conversion on the SiC carbide are directly affecting the silicon recovery as well as the efficiency of the ferrosilicon process. The simultaneous fulfillment all requirements are difficult to satisfy by using only one type the reducer in the charge for the ferrosilicon process. This requires the use of a mixture reducers, and the adoption of a compromise that all requirements are met in the best possible extent. To choose the composition of carbon reducers mixture has been used simple physico-chemical model of the ferrosilicon process with two reaction zones between which there is a mass transfer. It has been shown that in the charge for the ferrosilicon furnace about 30% mass of Cfix carbon resulting from the reaction stoichiometry of silica reduction process should be in the form of the reducer with increased to SiO reactivity.

The Use of Thermo-Gravimetric Studies for the Assessment of Technological Properties of Quartzites for the Ferrosilicon Smelting Process

The most objective methods of determining the usefulness of quartzite for the ferrosilicon smelting process are industrial research methods, but such studies are long-lasting and costly. In order to test the usefulness of thermo-gravimetric method to evaluate technological properties of quartzites in a laboratory, thermo-gravimetric studies of quartzites samples from various deposits were carried out. These quartzites are used or were used as a raw material in industrial ferrosilicon process. The study consisted of measuring the weight loss of powder samples in the form of mixture of quartz with graphite of molar ratio SiO2 + 3C during heating under an argon atmosphere in the temperature range up to 1500°C. The evaluation of technological properties of quartzites was done by comparing the curves of relative weight loss with industrial technological data of the ferrosilicon smelting process. It was established that the results of thermo-gravimetric studies show satisfying agreement with observations of industrial process, whereas quartzites of improved technological properties revealed a lower weight loss in thermo-gravimetric studies. Studies of this type can be useful as one of the methods of objective assessment of usefulness of quartzites for the ferrosilicon smelting process.

Importance of Electrodes Slipping Algorithm for the Ferrosilicon Smelting Process

The electric arc is one of the most unstable parts of the electrical circuit of submerged-arc furnaces in the ferrosilicon smelting process. In the carbothermal silica reduction electric arc has an important role as a high temperature heat source, and its presence is essential for the proper ferrosilicon process flow. Presence of the of electric arc and temperature conditions of the ferrosilicon process have a direct relationship with position of the electrodes tip and electrodes slipping. In the ferroalloy industry position of electrodes tip as similar as metallurgical parameters of the process are not directly measured. Most often these assessments are still based to a large extent on intuition and experience operating staff of the furnaces, and have qualitative and subjective character. In order to check the existing algorithm of electrodes slipping was carried out statistical studies of the FeSi75 ferrosilicon smelting process. The study was conducted at discrete intervals ∆t = 8h using data recorded by the furnace computer measuring system and methods of statistical data processing. It was found that the size of the electrodes slipping, and Cfix ratio in the feed are correlated and are among the most important parameters which have an impact on the technical and economic indicators of the process.

Analysis of the Possibilities Using of the Post-Reaction Gases Enthalpy from the Ferrosilicon Smelting Process

The paper presents an analysis of the possibilities of using the enthalpy of post-reaction gases from the ferrosilicon smelting process to produce electricity. Ferrosilicon smelting in the submerged arc furnace is one of the most energy-consuming electro thermal processes. Post-reaction gases, generated during the silica reduction process with carbon, contain significant amounts of energy. In the past the issue of energy recovery from the ferrosilicon process has been repeatedly taken, but for the Polish ferroalloy industry it is still valid. In order to determine the amount of energy possible for recovery calculations based on mass and energy balances has been carried out and determined the stream enthalpy of post processing gas. For preparing the balance sheets has been used operational data from the 20 MVA furnace and the overall reaction of the silica reduction process. It was assumed that the reduction process occurs at a temperature of 1650°C, and the temperature of leaving post-reaction gas, whose main ingredients are oxides CO and SiO, is 750°C.

The Use of Trapezoidal Fuzzy Numbers in the Model to Optimize the Batch of Electric Arc Furnace

The classical models to optimize the batch of electric arc furnace require precise and predetermined numerical values. In order to determine the scrap steel properties (eg. chemical composition), we are not able to define these values precisely and accurately. This situation is due to the heterogeneity and specificity of this material, which is related to its origin and way of obtaining. Therefore the usefulness of classical models to optimize the batch of electric arc furnace is limited. The fuzzy numbers with trapezoidal membership function were applied as a model in order to describe the technological process of steelmaking, which is neither accurate nor of ambiguous nature of the parameters. The advantage of trapezoidal numbers is a simple algorithm of arithmetic operations as well as easy and intuitive interpretation. The structure of optimization model with fuzzy parameters is similar to the classical linear optimization model of the mixtures composition. The optimization model, that is formulated on the fuzzy ranges arithmetic principles, allows to ensure that the quality parameters of the batch mix for the electric arc furnace are as precise as the ones described by electro-steel works, even though the quality parameters of scrap steel as well as some of the parameters of steel melting technological process are described ambiguously.

Effects of Raw Material Contaminants on the Ferrosilicon Melting Process in the Submerged Arc Furnace

Based on the Minimum Gibbs Free Enthalpy algorithm (FEM) and a model of reaction zones located around electrode tips in the submerged arc furnace, an analysis of the raw material chemical composition influence on the ferrosilicon smelting process was carried out. A model of the ferrosilicon process in the submerged arc furnace is a system of two closed isothermal reactors: an upper one with a lower temperature T1, and a lower one with a higher temperature T2. Between the reactors and the environment as well as between the reactors inside the system, a periodical exchange of mass occurs at the moments when the equilibrium state is reached. Based on the model, sets of calculations were performed: for a Fe-Si-O-C system and, subsequently, for a more complex Fe-Si-O-C-Al-Ca-Mg-Ti system. For both systems, the energy and mass balance values were calculated and the effects of raw material contaminants on the efficiency of the ferrosilicon melting process were determined.

Evaluation of Refractory Lining of the Blast Furnace Hearth and Bottom in Five Years of its Operation on the Basis of the Isotherms Shapes

Based on archival temperature measurement data regarding a blast furnace (capacity of 3200 m3) hearth and bottom refractory lining, empirical isotherms T = 300°C, for various periods of the first five years of the furnace campaign were determined. This resulted in an attempt to assess the hearth and bottom refractory lining in the third month and subsequently, in the next years of the blast furnace operation. The empirical isotherms, determined after the first three months, were compared to the isotherms determined using the method of mathematical modelling. These empirical isotherms were compared to each other, respectively in one-year intervals. The most distinctive changes of the hearth and bottom refractory lining were observed during the first three months of the furnace campaign. In the further period of five years, the changes were insignificant. During the early stage of furnace operation, observed deterioration of the refractory lining was associated with partial damage of the bottom ceramic layer and elephants foot-shaped defects of the refractory lining in the lower, thickened parts of the hearth walls. Early, elephants foot-shaped wear of the refractory lining is related to the mechanism of its wash-out by liquid products of the process during tapping, which results from certain maladjustment of the hearth and bottom inner geometry in modern furnaces to the hydrodynamic conditions of metal and slag flow.