Biochars in Iron Ores Sintering Process: Effect on Sinter Quality and Emission

The article presents results of the research on the use of chars produced during pyrolysis of residual biomass as a substitutional fuel in the iron ore sintering process. Such an approach allows to implement circular economy and industrial symbiosis to the iron and steel branches. The effect of the substitution of conventional coke breeze fuel used in sintering on final sinter quality and emission was examined. With regard to productivity, fuel consumption, and properties of the sinter it was shown that the share of tested biochars in fuel may be kept at 10, and up to 30, wt.%, depending on the biochar type. It was observed that with the use of the biochars, the content of iron oxide in the sinter decreased, which was advantageous. Moreover, the sinter obtained in the presence of biochars was characterized with better strength and abrasion than the sinter obtained with coke breeze-based fuel, improving the final product quality. The presence of biochar influenced the raw exhaust gas composition and resulted in a slight increase of organic and inorganic carbon compounds content, while the amount of sulfur oxides was noticeably decreased. It was concluded that the biochars may be applied in the sintering process at established share in the fuel stream.

Modified coke breeze distribution in iron ore sintering - a novel technique of reducing energy consumption and improving quality

In normal sintering of iron ore, there is a wide difference in temperature of the sinter bed between top and bottom; i.e. the flame front temperature of the sinter bed gradually increases towards the bottom because the lower part gets longer time for drying and preheating by exit gas. Therefore, the top part may have insufficient fusion and the bottom is excessively fused. Thus, sinter quality may become inhomogeneous and the coke breeze requirement becomes higher than the actual thermal requirement. If it is charged in multiple layers; e.g. higher amount of coke at the top and a lower amount of coke at the bottom, heat will be homogeneously distributed and the actual coke requirement would be lower than the existing. However, no study has been done so far on this. Therefore, the current study explores the possibility of reducing energy consumption in iron ore sintering by reducing the coke ratio from top to bottom without deteriorating the sinter property. 12% reduction in coke breeze rate has been found and the sinter quality has been improved by the use of a triple layer of sinter mix with a lower coke rate towards the bottom. Further, when 5-vol% of oxygen has been enriched in suction gas along with using a triple layer of sinter mix, up to an 18-wt% reduction in coke breeze has been found.

Main stages of the technology and equipment perfection at JSC EVRAZ ZSMK sintering plant

Data on sintering plant of OJSC EVRAZ ZSMK, its structure, stages of construction, main designing solutions, operation indices and structural changes presented. Main directions of technology and equipment perfection shown. From the moment of the sintering plant putting into operation, it operated by the designed plan, which met the existing in early 70th of the former century requirements of fluxed sinter production technology. Later the flowchart, technology and the aggregates subjected to considerable modifications. The main efforts of researchers and the plant personal developments directed on the study of the burden components and obtained sinter properties, elaboration of a technology of new kinds of raw materials sintering, optimization of main parameters of the sintering process technological regime, external heating and the burden components preparation. Besides new technological units and equipment implemented and their operation modes mastered, as well as that of process intensification. In addition, the plant personal paid much attention to the sinter quality and technical and economic indices improving, to ecology and wastes utilization, as well as elaboration of a technology of special kinds of sinter production after BF No. 2 stop and some capacity releasing. At present, the two-layer burden sintering technology mastered at all the sintering machines with the layer height500 mm. The work on modernization of the main and auxiliary plant equipment accomplished continuously. Automated control systems widely used at the plant to control the following: the quality of the incoming raw materials, supply and consumption of raw materials, calculation of the stacks, concentrate liming, the burden components and fuel dozing, the burden moistening, the burden preparation and sintering, the plant running, sinter and energy carriers accounting as well as information and technological circuit. At present, a big volume of work planned, directed on polluting substances emissions lowering, volume of production increasing and sinter quality improving, as well as production and operation costs decreasing.

Microstructure and Minerals Evolution of Iron Ore Sinter: Influence of SiO2 and Al2O3

SiO2 and Al2O3 are two important minerals that can affect the mechanical and metallurgical properties of sinter. This investigation systematically studied the influences of these minerals and revealed their functional mechanisms on sinter quality. Results showed that with an increasing Al2O3 content in sinter, the sintering indexes presented an improvement before the content exceeded 1.80%, while the quality decreased obviously after the content exceeded 1.80%. With an increasing SiO2 content, the sinter quality presented a decreasing tendency, especially when the content exceeded 4.80%. Consequently, the optimal content of Al2O3 was ≤1.80% and that of SiO2 was ≤4.80%. The evolution of the microstructure and minerals in sinter showed that enhancing the Al2O3 content increased the proportion of SFCA generated, which improved the sinter’s mechanical strength, while excessive Al2O3 led to the formation of sheet-like SFCA with weak mechanical strength. Increasing the content of SiO2 strained the formation of SFCA and promoted the formation of calcium silicate, the mechanical strength of which is lower than that of SFCA. The research findings will be useful in guiding practical sintering processes.

Investigation of a granule structure that focused on reducing NOx emissions in sintering process

The pressure to reduce NOx emissions in iron ore sintering process is enlarging increasingly. The paper proposed a sintering granulation method to reduce NOx emissions. The main character of the method was to wrap all fuel on the surface of the pellet, and also increased the contact between iron ore and fluxes. The sinter-pot test results showed that NOx emissions of the method reduced by 19.9% and sinter quality improved, while SO2 emissions increased by 17.7% compared with that of the conventional method. The increase in the reducing atmosphere of the sinter bed and the development of calcium ferrite in sinter were the main causes of NOx emissions reduction and the improvement of the sinter quality. In addition, the promotion of the combustion of fuel resulted in the increase in SO2 emissions. The improvement of the sinter quality and the control of the sintering flue gas pollutants can also be realized through adjusting the distribution of fuel, fluxes and iron ore in the pellet reasonably.