4 Direct Reduced Iron Production Technologies
1. Gas-based shaft furnace technology
The application of gas-based shaft furnace technology to produce direct-reduced iron can make it realize hot discharge, direct-reduced iron can be directly loaded into the electric furnace to complete the steelmaking. 500~700 ℃ direct-reduced iron hot-loaded electric furnace steelmaking can save 60~80 kW-h/t of electric energy. At the same time, after simplified treatment of direct-reduced iron, and then after the treatment of the furnace, can effectively reduce the re-oxidation of direct-reduced iron in the cooling and transportation process. In addition, coal-to-gas technology is also one of the relatively mature conventional technologies in coal chemical technology, which has been used for a long time in China. From the perspective of energy consumption, environmental protection and subsequent process connection, gas-based shaft furnace technology will become the main means of direct reduction of iron production in China.
2. Rotary kiln technology
Rotary kiln method is the most mature and largest scale process in the application of coal-based direct reduction technology. It has been widely used in various regions of China. For example, TPCO based on the introduction of rotary kiln technology, has implemented a large number of transformation programs, and has made great progress in technology, with the production exceeding 20% of the original plan in the best year. In addition, the rotary kiln technology has very strict requirements for raw fuel, high energy consumption, relatively high operating costs, greater difficulty in stabilizing production during operation, and certain limitations in the expansion of production scale. Therefore, the rotary kiln method has been widely used in small and medium-sized direct-reduced iron production in areas with suitable resource conditions, but it is difficult to become the core process of direct-reduced iron in China.
3. Tunnel kiln technology
The use of tunnel kiln technology for the production of direct reduced iron belongs to a relatively old ironmaking method, from the international application, the tunnel kiln method is only used in powder metallurgy to reduce iron powder reduction process. Except for our country, it is rare to see the production of direct-reduced iron by tunnel kiln technology. The technical content of the technology is low, very suitable for small-scale production, and less investment in private enterprises. Nowadays, a large number of tunnel kilns have been built in China, the design capacity has made a significant breakthrough, and the consumption of physical coal has been increasing up to now. But this method will emit more pollutants, product quality is very unstable, can not become the main development method of China's direct reduction of iron.
4. Fluidized bed method technology
Fluidized bed method is mainly the use of powdered raw materials and iron ore powder monomer particles, in the high-temperature reduction of gas flow reduction, in this process, the powdered ore does not have to block, the reduction speed is relatively fast. Its reduction mechanism is mainly the most reasonable process method in the gas-based method, and is highly valued in the direct reduction development and development process. However, in actual production practice, because the material fluidization of the gas flow required far more than the reduction of the gas volume required, the reduction of gas once through the utilization rate is low, which also makes the sticking problem has been plagued by the stability of fluidized bed production.
