A Numerical Study on the Performance of the H2 Shaft Furnace with Dual-Row Top Gas Recycling

Given the urgent pursuit of carbon neutrality and stringent climate policies, the H2 shaft furnace (H2-SF) is starting to gain widespread attention in the steel industry. In this study, the performance of the H2-SF under operation with a dual-row injection top gas recycling system was investigated by a one-dimensional mathematical model. The potential of microwave heating as a means to supply thermal energy in regions of energy deficit was also assessed briefly. The results showed that for scenarios without microwave heating, increasing the upper-row injection rate can improve the furnace performance, and increasing the distance of the upper-row injection level from the furnace top also has a positive effect. A high microwave heating efficiency is expected in regions above the upper-row injection level. For scenarios with microwave heating, a higher microwave power leads to a better furnace performance. Thus, a higher furnace productivity can be achieved by increasing either the upper-row injection rate or the microwave power. However, the latter seems more promising as it decreases the total energy demand due to a better utilization of thermal energy. Based on the comparison of two representative examples, the decrease in the total energy demand is about 0.2 GJ/t-Fe.

Understanding of Blast Furnace Performance with Biomass Introduction

The blast furnace still dominates the production and supply of metallic units for steelmaking. Coke and coal used in the blast furnace contribute substantially to CO2 emissions from the steel sector. Therefore, blast furnace operators are making great efforts to lower the fossil CO2 emissions and transition to fossil-free steelmaking. In previous studies the use of pre-treated biomass has been indicated to have great potential to significantly lower fossil CO2 emissions. Even negative CO2 emission can be achieved if biomass is used together with carbon capture and storage. Blast furnace conditions will change at substantial inputs of biomass but can be defined through model calculations when using a model calibrated with actual operational data to define the key blast furnace performance parameters. To understand the effect, the modelling results for different biomass cases are evaluated in detail and the overall performance is visualised in Rist- and carbon direct reduction rate (CDRR) diagrams. In this study injection of torrefied biomass or charcoal, top charging of charcoal as well as the use of a combination of both methods are evaluated in model calculations. It was found that significant impact on the blast furnace conditions by the injection of 142 kg/tHM of torrefied biomass could be counteracted by also top-charging 30 kg/tHM of charcoal. With combined use of the latter methods, CO2-emissions can be potentially reduced by up to 34% with moderate change in blast furnace conditions and limited investments.

Technological suitability of semi-coke as a carbon reducer in production of manganese and silicon alloys

The article presents results of testing semi-coke as a carbon reducing agent in the production of manganese and silicon alloys. The fundamental possibility of using semi-coke in carbon part of the charge as a basic reducing agent for the production of ferrosilicon manganese is established. It is noted that the new reducing agent in its pure form works worse than in the mixture with coal. The greatest synergistic effect in the production of ferrosilicon manganese was achieved during the interaction of semi-coke with coal, while the following indicators were obtained: maximum furnace productivity of 43 t/day, maximum extraction coefficient of 87.9 %, and minimum specific dust formation of 49 kg/t of alloy. In the production of ferrosilicon the use of a new reducing agent did not give a significant positive effect, due to its low structural strength. It was revealed that the structure and type of the reducing agent affect the furnace performance: when using a reducing agent with a higher reactivity in the charge, it is possible to obtain higher furnace performance. In the production of ferrosilicon, a change in the specific dust generation is closely related to the level of daily production and specific energy consumption and can serve as an indicator of the furnace operation. The furnace performance, ceteris paribus, is determined by the amount of useful power input. With an excess of carbon in the charge an increase in useful power leads to a slight increase in the furnace performance, but at the same time, the energy consumption and specific dust formation significantly increase. It is shown, that the influence of technological factors on the technical and economic indicators of melting is determined by the degree of electrode seating in the furnace.

Comparison parameters for carbon ferrochrome smelting in AC and DC furnaces

One of the interesting technical solutions is technology of ferroalloys smelting using direct current (DC). In DC ferroalloy furnaces, apparently, it is possible to eliminate such a parameter as power factor in furnace circuit after current converter. Many researchers assume that melting at direct current allows intensification of the process of charge melting, increases reduction of leading elements of ferroalloy and reduces specific consumption of electricity. In this paper, brief analysis of carbon ferrochromium smelting in alternating current (AC) and in direct current (DC) furnaces is made based on energotechnological criterion of ferroalloy electric furnace performance. It is shown that with comparable active capacity in bath, AC furnaces have higher energotechnological criteria (0.2185 – 0.2381), compared to DC furnaces (0.1109 – 0.1320), at current level of technology used for carbonaceous ferrochrome smelting. Thus, in AC furnaces, specific electric power consumption in ferrochrome smelting is lower than in DC furnaces by 20 – 28 %.