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.

​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.

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.

Direct reduced iron has a relatively stable composition, low content of harmful impurities and relatively uniform particle size. As a high-quality raw material in modern metallurgy, direct reduced iron plays a vital role in metallurgy. In recent years, the application of direct reduced iron in the smelting of high-quality steel in electric furnaces, blast furnaces and other smelting furnaces is relatively common, which can effectively improve the production efficiency and reduce the coke ratio, and has positive significance for improving the overall efficiency of modern metallurgy. In addition, direct reduced iron can also be used in LD converter coolant and flat furnace effective metal raw materials, can also play a positive role.

Directly reduced iron added to the electric arc furnace proportion varies, if the proportion of direct reduction of iron is less than 30%, can be used cans of material loading. The bottom of the basket is filled with light scrap, followed by heavy scrap and direct-reduced iron, to avoid too much lumping of direct-reduced iron. However, when the arc heats the thicker layers of direct reduced iron, the molten metal fills the spaces between the direct reduced iron and condenses, causing the charge to sinter into a single piece, making it difficult to add the charge as a whole to the molten pool and extending the melting cycle. When more than 30% of the charge is added in batches, due to the slow heat transfer of the direct-reduced iron, the relevant technical indicators are poor, and should be fed into the furnace by means of continuous charging.

Four cases were compared: carbon-free and carbon-containing DRI from DR-grade pellets as well as fines from a fluidized bed reactor were melted batch-wise. A slag layer’s influence was investigated using DRI from the BF-grade pellets and the continuous addition of slag-forming oxides. While carbon-free materials show a porous structure with gangue entrapments, the carburized DRI forms a dense regulus with the oxides collected on top. The test with slag-forming oxides demonstrates the mixing effect of the arc’s electromagnetic forces. The cross-section shows a steel melt framed by a slag layer. These experiments match the past work in that carburized DRI is preferable, and material feed to the hotspot is critical for the EAF operation.

Hydrogen-based direct reduction is a promising technology for CO2 lean steelmaking. The electric arc furnace is the most relevant aggregate for processing direct reduced iron (DRI). As DRI is usually added into the arc, the behavior in this area is of great interest. A laboratory-scale hydrogen plasma smelting reduction (HPSR) reactor was used to analyze that under inert conditions.

The HBI imported in the current season is all used in converter production, and the main charge for the Basic Oxygen Furnace (BOF) is molten pig iron from the blast furnace, commonly referred to as "hot metal" (HM). In addition to iron, blast furnace hot metal contains a certain amount of oxidizable elements, such as carbon, silicon, manganese, and phosphorus.

Limited by resources, technology and other factors, the production of DRI (direct reduced iron) in China started late and developed slowly. The production enterprises of DRI in China are small in scale, mainly produced by tunnel kilns, scattered in origin and unstable in production organization, which lead to the difficulties in production statistics. The products are mostly used in powder metallurgy raw materials.