The replacement of the blast furnace—basic oxygen furnace (BF-BOF) steelmaking route with the direct reduced iron—electric arc furnace (DRI-EAF) route reduces the direct CO2 emissions from steelmaking by up to 68%; however, the DRI shaft furnace is one of the largest remaining point source emitters in steelmaking. The capital and operating expenses of two potential nearly carbon-neutral DRI process configurations were investigated as a modification to a standard Midrex DRI facility.

To overcome the limitations of the above two processes, and to achieve a more efficient direct reduction process of iron ore, the possibility of combining these two methods was investigated. The experiments focused on performing an initial direct reduction using ore-coal composite pellets followed by a second stage gas reduction. It was assumed that the initial reduction of the carbon composite pellets would enhance the efficiency of the subsequent reduction by gas and the total reduction efficiency. The porosity, as well as the carbon efficiency for direct reduction, were measured to determine the optimal conditions for the initial reduction, such as the size ratio of ore and coal particles. Thereafter, further reduction by the reducing gas was carried out to verify the effect of the preliminary reduction. The reduction kinetics of the reducing gas was also discussed.

Recently, direct reduced iron (DRI) has been highlighted as a promising iron source for electric arc furnace (EAF)-based steelmaking. The two typical production methods for DRI are gas-based reduction and reduction using carbon composite pellets. While the gas-based reduction is strongly dependent on the reliable supply of hydrocarbon fuel, reduction using ore-coal composite pellets has relatively low productivity due to solid–solid reactions.

In this paper, the research status of the thermal state, reduction mechanism of iron-bearing burden, coke degradation behavior, and formation of the cohesive zone in various areas of blast furnace after hydrogen-rich smelting is summarized, which can make a more clear and comprehensive understanding for the effect of H2 on blast furnace ironmaking.

In the past 20 years, many sintering plants have continued to innovate traditional sinter material preparation technology. Japanese companies such as Sumitomo and Nippon Steel were the first to use vertical intensive mixers for mixing sinter materials. Through research and practice at Sumitomo Wakayama Third Sintering Plant, the use of a vertical powerful mixer instead of a cylindrical mixer has enhanced the mixing effect of the sintered raw materials, and the corresponding granulation effect has also been enhanced, ultimately making the sintered raw materials highly breathable. The sintering speed is increased by 10%~12%, and the coke powder addition ratio can be reduced by 0.5%.

Rotary kiln is a commonly used production equipment in modern industrial production. It is widely used in chemical industry, building materials, non-ferrous metallurgy, ferrous metallurgy and other industries, such as: drying and oxidation roasting of materials in the chemical industry; drying of raw materials in the building materials industry and dolomite roasting; oxidative desulfurization of raw materials in the nonferrous industry, synthesis of reagents; drying of ore powder, preparation of smelting flux, production of oxidized pellets, production of direct reduced iron, and smelting of ferronickel in the steel industry.

In recent years, with the implementation of a series of new environmental protection policies, higher requirements have been placed on the environmental management methods of foundry companies and the occupational health and safety of employees. The pollution control technology and facilities of foundry enterprises during the production process are still relatively backward. Under such realistic conditions, there is an urgent need for environmentally friendly binders, and phosphate inorganic binders have emerged.

​Currently, most of the existing direct reduced iron production processes in the world use the briquetting process to solve the problems of DRI such as high powder content, low density, flammability, large dust, and insufficient latent heat utilization. Briquetting is the method of applying mechanical pressure to agglomerate the pellets or powdered DRI produced by direct reduction into dense closed blocks. Briquetting is divided into cold pressing process and hot pressing process.

The direct reduction technology of rotary hearth furnace has been developed for nearly forty years, and the device was firstly used in the heating furnace of steel rolling, and later used to treat the iron containing waste materials. The direct reduction technology of rotary hearth furnace is characterized by low fuel quality, no need for deep processing of raw materials, simple process, good utilization of waste resources, and protection of the human environment, therefore, it has received more and more attention from the industry.

First, using a certain proportion of DRI in the smelting process of high-quality steel in EAF can improve the mechanical properties and overall quality of high-quality steel. At the same time, reasonable control of the application proportion of DRI can achieve the purpose of energy saving and increase in production, which is of great significance to improving the comprehensive benefits of EAF steelmaking. Second, the application of DRI in BF steelmaking can reduce the coke ratio of BF steelmaking and increase the output of BF steelmaking. The economic benefits of BF steelmaking are greatly improved.