Behavior of niobium, manganese and phosphorus during reducing roasting of rare earth-rare metal ore of the Chuktukon deposit

The article examines research on high-temperature reducing roasting of rare-earth-rare metal ores of the Chuktukon deposit. The effect of process temperature and consumption of reducing agent (coke) on distribution of niobium, manganese and phosphorus between metal and slag phases was studied. It was shown that a decrease in coke consumption in the range of 15–19 % promotes an increase in the extraction of niobium and manganese into the slag phase, while the reduction of phosphorus to metal increases with an excessive consumption of the reducing agent.

Resource Intensity vs. Investment in Production Installations—The Case of the Steel Industry in Poland

Resource intensity is a measure of the resources needed for the production, processing and disposal of good or services. Its level decides on the costs the companies have to bear both for production and for environmental protection, which in turn have a crucial importance for their competitiveness. Given these facts, our study analyses the issues of resource intensity in the Polish steel industry in correlation to investments made, and more specifically, to the impact of investments on the consumption of energy media used during steel production. Its key element is the development of econometric models presenting the impact of investments on resource consumption in steel production in Poland. Electricity and coke consumption were analysed according to manufacturing installation. The research was carried out on the basis of statistical data for the period of 2004–2018. The obtained findings confirmed the impact of the increase in investment on the decrease in the resource intensity in steel production in Poland. These facts have implications for both policy makers, as they confirm the thesis on a direct correlation between investments in technology and a reduction in resource intensity (environmental protection), as well as company managers. In the case of the latter, the data show the actions which companies should focus on in their activities.

Efficiency of injection of natural gas and pulverized coal at ironmaking

The method for calculating indicators of blast furnace smelting with replacement of part of coke with additional fuels has been developed on the basis of full and complex compensation and compensating measures. Efficiency of the use of natural gas and pulverized coal in the blast furnace conditions of the Enakievo Metallurgical Plant was calculated and it has been confirmed as rather high. Increase in the consumption of natural gas from the baseline (71.8 m3/t of iron) to 110 m3/t ensures a corresponding increase in productivity of the blast furnace to 107.6 % and a decrease in the consumption of coke to 417.3 kg/t of iron (–38.4 kg/t, –8.42 %). Replacing natural gas with pulverized coal in the amount of 160 kg/t of iron made it possible to completely remove it from the blast. At the same time, coke consumption decreased to 354.59 kg/t of iron (–101.1 kg/t; –22.18 %). Increasing the consumption of pulverized coal fuel up to 200 kg/t of iron with compensation of the blast temperature of1200 °Cand oxygen of the blast of 25 % provides an increase in the productivity of the blast furnace to 105.8 % and reduction of coke consumption to 303.8 kg/t of iron (–151.9 kg/t, –33.33 %). High efficiency of the use of pulverized coal in conditions of the Enakievo Metallurgical Plant is explained by its lower cost compared to natural gas, high carbon content in coal and a significantly lower effecton the theoretical combustion temperature and other technological parameters.

The Effects of Coke Parameters and Circulating Flue Gas Characteristics on NOx Emission during Flue Gas Recirculation Sintering Process

The new process of flue gas recirculation, which reduces coke consumption and reducing NOx emissions, is now extensively used. Compared with traditional sintering, the characteristics of circulating flue gas and coke parameters significantly affect the combustion atmosphere and coke combustion efficiency. Based on the actual complex process of sintering machine, this study proposes a relatively comprehensive one-dimensional, unsteady mathematical model for flue gas recirculation research. The model encompasses NOx pollutant generation and reduction, as well as SO2 generation and adsorption. We focus on the effects of cyclic flue gas characteristics on the sintering-bed temperature and NOx emissions, which are rarely studied, and provide a theoretical basis for NOx emission reduction. Simulation results show that during sintering, the fuel NOx is reduced by 50% and 10% when passing through the surface of coke particles and CO, respectively. During flue gas recirculation sintering, the increase in circulating gas O2 content, temperature, and supply-gas volume cause increased combustion efficiency of coke, reducing atmosphere, and NOx content in the circulating area; the temperature of the material layer also increases significantly and the sintering endpoint advances. During cyclic sintering, the small coke size and increased coke content increase the char-N release rate while promoting sufficient contact of NOx with the coke surface. Consequently, the NOx reduction rate increases. Compared with the conventional sintering, the designed flue gas recirculation condition saves 3.75% of coke consumption, i.e., for 1.2 kg of solid fuel per ton of sinter, the amount of flue gas treatment is reduced by 21.64% and NOx emissions is reduced by 23.59%. Moreover, without changing the existing sintering equipment, sintering capacity increases by about 5.56%.

Mastering technology of blast furnace iron smelting using pulverized-coal fuel in the PAO NLMK BF shop № 2

Application of pulverized-coal fuel (PCF) for coke saving is strategic direction of energy costs decreasing for iron smelting in PAO NLMK blast furnaces, which allows to change the structure of coals supply to the plant and to decrease their summarized consumption. Stages of the technology mastering considered, including period of adjusting the PCF preparation and their supplying to the blast furnaces and at the stage of charging system selection and blast regime adjustment ensuring the maximum degree of CO utilization and the specified performance. Analysis of the dynamics of coke consumption and fuel additives showed that the consumption of total carbon fuel remained almost unchanged, despite the difference in the amount of carbon supplied with natural gas and with the PCF. Calculations made by the mathematical model showed that with an increase in the PCF consumption and a decrease in the consumption of natural gas, the replacement rate of coke with natural gas increased by an average of 0.09 kg of coke per 1 cubic meter of natural gas. As a result of the iron smelting technology mastering, in the PAO NLMK BF № 2 a specific coke consumption decrease reached by more than 80 kg/t of iron and natural gas consumption decrease by more than 60 m3/t of iron. The conditions were revealed for the blast furnaces to operate as with minimum coke consumption and with maximum intensity. The blast furnaces operation in the determined regime parameters allow to decrease the fuel costs for iron production.

Increasing the efficiency of blast-furnace smelting by improving the quality of iron ore materials

It is noted in the work that when mastering the technology of pulverized coal injection (PUT) at the metallurgical enterprises of Ukraine, it is necessary to intensify work, including research, in the direction of improving the quality characteristics of the sinter, the stability of its chemical composition and strength parameters. The analysis of the quality of iron ore raw materials used in sintering production in Ukraine and foreign countries is carried out. The requirements of international and domestic standards for the quality of raw materials and fuels, providing for the injection of large quantities of firearms into the furnace, are given. A methodology for determining the quality of raw materials developed in the HMI is described. The results of a study of the quality of iron ore raw materials according to the developed method are presented. Based on the analysis of the results of the research, requirements were developed for the quality of granular iron ore wastes and their rational amount in the composition of the sinter charge, and the process for the production of granules was developed. Recommendations have been developed on the use in the sinter mixture of a part of the granular components of secondary waste, which allowed to increase the content of secondary resources in the mixture. As a result, the chemical composition of the sinter was stabilized, its strength was improved, the yield of sinter of the second grade was reduced, the removal of blast furnace dust and coke consumption were reduced. Improving the quality of the sinter and the rational distribution of charge materials over the cross-section of the top of the blast furnace allows for self-renewal of the protective skull, to reduce the removal of top dust by 4.3 kg / t of cast iron, and to reduce coke consumption by 19.6 kg / t of cast iron. The developed measures make it possible to increase the competitiveness of products, even at the additional cost of preparing the sinter mixture for sintering.

New Trends in the Application of Carbon-Bearing Materials in Blast Furnace Iron-Making

The iron and steel industry is still dependent on fossil coking coal. About 70% of the total steel production relies directly on fossil coal and coke inputs. Therefore, steel production contributes by ~7% of the global CO2 emission. The reduction of CO2 emission has been given highest priority by the iron- and steel-making sector due to the commitment of governments to mitigate CO2 emission according to Kyoto protocol. Utilization of auxiliary carbonaceous materials in the blast furnace and other iron-making technologies is one of the most efficient options to reduce the coke consumption and, consequently, the CO2 emission. The present review gives an insight of the trends in the applications of auxiliary carbon-bearing material in iron-making processes. Partial substitution of top charged coke by nut coke, lump charcoal, or carbon composite agglomerates were found to not only decrease the dependency on virgin fossil carbon, but also improve the blast furnace performance and increase the productivity. Partial or complete substitution of pulverized coal by waste plastics or renewable carbon-bearing materials like waste plastics or biomass help in mitigating the CO2 emission due to its high H2 content compared to fossil carbon. Injecting such reactive materials results in improved combustion and reduced coke consumption. Moreover, utilization of integrated steel plant fines and gases becomes necessary to achieve profitability to steel mill operation from both economic and environmental aspects. Recycling of such results in recovering the valuable components and thereby decrease the energy consumption and the need of landfills at the steel plants as well as reduce the consumption of virgin materials and reduce CO2 emission. On the other hand, developed technologies for iron-making rather than blast furnace opens a window and provide a good opportunity to utilize auxiliary carbon-bearing materials that are difficult to utilize in conventional blast furnace iron-making.

APPLICATION OF MARKOV CHAINS TO THE ANALYSIS OF BLAST FURNACE OPERATION EFFICIENCY

The article presents the results of modeling in a dynamic format of one of the most important parameters of any research object – the efficiency of its work. As the object of investigation, a blast furnace with a volume of 2014 m3 was chosen. The main parameters of the efficiency of this object are traditionally used daily productivity and specific consumption of coke; these two parameters were generalized in this paper. In this case, various algebraic signs of the influence of these parameters were taken into account in the generalized efficiency index. Taking into account the variation of each of these parameters at 3 levels, the number of levels of the generalized efficiency index was determined as 32 = 9, therefore it was rational to take a 9-point scale with the measuring scale of profitability from the efficient operation of the blast furnace. The two-dimensional array of primary data of the volume N = 177 was transformed into a 9×9 transitional matrix for processing of random transitions of the efficiency index from one state to another by the Markov chain method with discrete states and time. The set of parameters of the random process is calculated: for the long-term forecast – the stationary vector of state probabilities, the average time of recurrence (reversal) for each efficiency state, the evaluation of the blast furnace efficiency in points; for a short-term forecast – the first time of transition from each state to any other state, the step number for a “burst” of probability for each reliable state at the initial moment of time, and the components of the efficiency index are obtained. It was established that the average level of the analyzed efficiency of the blast furnace (daily output 3702 tons and specific coke consumption 470 kg/ton) is achieved mainly due to short-term transitions of low-efficiency states to high-efficiency states and vice versa. The transfer of the system to more efficient and prolonged conditions is possible, and as practice has shown on the same blast furnace after repair works to eliminate the distortion of the furnace profile, the daily productivity has increased to 5048 tons with a specific coke consumption of 445 kg/t, but the structure of the transition matrix and the calculated indicators of the Markov chain have fundamentally changed in the direction of increasing the probabilities of stay and transitions of the system in more efficient states. The use of the Markov chain method with discrete states and time makes it possible to estimate the probable value of the change in the parameters of the operation of a blast furnace in a given time interval with constant levels of parameters characterizing the conditions of its operation.