Pelletizing Analysis on MgO-Fluxed Pellets by DEM

The Discrete Element Method (DEM) was used to analyze the pelletization process of MgO-fluxed pellets. The effects of the charge ratio and rotational speed of the disc pelletizer on the behavior of MgO-fluxed pellets were investigated by using a simulation. The simulation results show that under the condition of a certain tilt angle of the disc pelletizer (the tilt angle is 49°), the suitable parameters of the disc pelletizer are that the charge ratio is 20% and the rotational speedis 0.7 N/NC. This simulation model proposed will be useful to research pellets behavior and for the design of disc pelletizers.

Influence of Type and Consumption of Pellets on Indicators of Blast-Furnace Smelting in the JSC Ural Steel

The article presents the results of the analysis of production data on the operation of the blast furnace No. 1 of Ural Steel JSC for the period from 2013 to 2018. During this period, the Mikhailovsky GOK pellets with different basicities were used. It has been established, that the effectiveness of the use of pellets of different basicities is determined by their behavior in a blast furnace and depends on the proportion of pellets in the iron ore part of the charge. The gas-dynamic conditions of melting deteriorate with an increase in the proportion of pellets in the charge, which is accompanied by an increase in the specific pressure drop and forces the blast rate, to be adjusted. It is necessary to work on 40-45% of fluxed pellets and 20-25% acid pellets in a charge at a blast rate of 2000-2100 m3/min, to minimize coke rate and increase rate of work of blast furnace No. 1 of Ural Steel JSC. An increase in pellet consumption is possible while maintaining the efficiency of blast-furnace smelting only if their high-temperature properties are improved, as a result of optimization of basicity and increase in MgO content, which affects the structure and properties of the silicate binder.

Influence of the consumption of pellets with different basicity on indicators of blast-furnace smelting

The results of the analysis of production data on the operation of blast furnace No. 1 (useful volume 1007 m3) of Ural Steel JSC for the period from 2013 to 2018 are presented. During this period, pellets from the Mikhailovsky GOK were used with varying degrees of fluxing: pellets of natural basicity in the ratio of CaO/SiO2 equal to 0.08 ± 0.02 units. (2013-2015) and partially fluxed pellets with a basicity of 0.52 ± 0.05 units. (from 2016 to the present). It has been established that the effectiveness of the use of pellets of various basicities is determined by their behavior in the blast furnace and depends on the proportion of pellets in the iron ore part of the charge. The gas-dynamic conditions of the smelting worsen with an increase in the proportion of pellets in the charge, which is accompanied by an increase in the specific pressure drop and forces the flow rate to be adjusted. There is an optimal level of specific pressure drop (53–55 Pa per 1 m3 of blast per minute) for the operating conditions of blast furnace No. 1 of Ural Steel, which ensures the optimum combination of the melting characteristics. Deviation from the optimal level of pressure drop leads to an increase in coke rate and a decrease in the degree of CO use, which is associated with gas distribution disturbance. Due to the increase in high-temperature properties, the replacement of non-fluxed pellets with off-fluxed pellets improves the gas-dynamic conditions in the lower part of the mine (in the cohesive zone). This leads to a decrease in the total pressure drop and specific pressure drop at a constant flow rate of the blast, and is a reserve for melting intensification. To minimize coke rate and maintain the high-performance operation of blast furnaces of Ural Steel JSC, it is necessary to work on 40–45 % of fluxed or 20–25 % acid pellets in a charge. An increase in pellet consumption while maintaining the efficiency of blast-furnace smelting is possible only if their high-temperature properties are improved. The improvement of these properties is possible as a result of optimizing the basicity and increasing the MgO content, which affects the structure and properties of the silicate bond. This work is carried out within a framework of the government order (No. FZRU-2020-0011) of the Ministry of Science and Higher Education of the Russian Federation.

Development of the Process for Obtaining Iron-Ore Pellets with Required Metallurgical Properties

We have studied the influence of oxidation-reduction reactions on the structure and strength behavior of the Kachkanar fluxed pellets both in their initial condition and during reduction. It has been discovered that at heating rates and temperatures found in industrial units the roasted pellets that are not oxidized to a full extent and are characterized by zonal structure do not meet the requirements imposed for the blast-furnace smelting raw materials. To develop a process that would ensure high metallurgical properties, we have analyzed the hematite dissociation reaction. It was found that the temperature and the content of slag-forming oxides influence this reaction. A sinter pot was used to carry out the research and determine metallurgical properties of partially dissociated pellets. The obtained results helped to develop a process to dissociate hematite at lower temperatures with calcium ferrosilicate melt. Such pellets are reduced at the temperatures of over 700оС, which prevents their destruction in blast furnaces.

Application of manganous limestone as a fluxing addition at pellets production

Usage of non-fluxed pellets in blast furnaces results in blocking of hearth coke filling, decreasing of blast furnaces productivity and increasing of coke rate. The wide range of plastic-viscous state and non-sufficient filterability of pellets slag portion through the coke filling are the main reasons of the consequences. Fluxed pellets have narrower interval of plastic-viscous state and better filterability of pellets slag portion through the coke filling. Their utilization enables to decrease the gas-dynamic resistance of blast furnace cohesion zone, to eliminate progressive hearth blocking, to intensify the hot metal production process and to increase its economic efficiency. In 70–80thof the previous century attempts were made to substitute the bentonite in burden at pellets production by hydrated lime and burnt lime, by marl, by nontronite clay, by red sludge and other additives, combining properties of the raw pellets strengthening and fluxing. But the methods listed were not implemented practically, in particular, because of difficulties in those two properties effective combining. Last years a new raw material appeared at the fluxes market – the manganous limestone. Manganese oxide, contained in it, decreases the sinter smelting temperature, calcium carbonate acts as a flux, while water and physical properties of the limestone improve the increase of the burden lump-forming capacity and sinter strength. The aim of the study was to check the manganous limestone influence on the production process and raw pellets strength, change of roasting parameters and strength of roasted pellets, as well as change of high-temperature properties of fluxed pellets made of Stojlensky GOK concentrates. The study were carried out in laboratory conditions by usage of Dash-Salakhlin bentonite and manganous limestone. The results of laboratory study of both raw and roasted pellets, obtained at utilization of manganous limestone as a fluxing additive to burden, showed, that their physical and mechanical properties are higher and metallurgical properties are higher, compared with non-fluxed pellets.