Clean steel is a steel with very strict requirements for the content of impurity elements in steel, generally requiring S,P mass fraction of less than 0.01%, and the content of hydrogen, oxygen and low melting point metals also have strict requirements.
China's current production of clean steel mainly uses the blast furnace - converter traditional process. China's iron ore resource endowment is poor, although after complex processing of the beneficiation process can produce iron ore concentrate to meet the requirements of blast furnace smelting, however, iron liquid usually contains more impurities, these impurities need to be removed in steelmaking process, that is complex and costly. In addition, the blast furnace iron making process coke is the main energy source, emitting a large number of pollutants, and polluting the environment.
Precondition to make clean steel is to require high quality iron powder and direct reduction iron. In following aspects new technology have made good progress.
Breakthrough iron ore traditional beneficiation - blast furnace - converter - RH refining process limitations, cold physical selection method to remove most of the non-iron impurities in iron ore, instead of the traditional high-temperature melting, slagging process, the formation of "iron ore concentrate depth of quality - selective direct reduction - low-carbon electric furnace smelting" production of high-quality pure iron technology.
Prepare narrow grade materials to strengthen the efficient monomer dissociation of iron minerals, and then use the electromagnetic selector with compound force field for deep iron extraction and impurity removal, which can directly obtain high grade iron concentrate with TFe70.00%~71.50% and SiO2＜2.00%.
Develop the structure design of high efficiency desilication flotation agent at room temperature based on MS simulation. The agent is the key technology to control the very low content of SiO2 and other impurities (acid insoluble matter), and the ultra-pure iron concentrate with TFe>71.50% and SiO2＜0.20% can be obtained after desilicification by reverse flotation.
Selective direct reduction - low carbon smelting pure iron technology. The use of low-temperature selective reduction technology to reduce iron minerals in super iron concentrates to metallic iron, strict control of non-ferrous elements reduction into the metallic iron phase, reduction products by the electric furnace high-temperature rapid melting to obtain high-quality pure iron, compared with the traditional blast furnace - converter - RH refining process pure iron Fe> 99.90%, C content can be<0.0005%, tons of pure iron CO2 emissions reduced by more than 70%.
At presnet, these studies are processing forward industrialization, and shall promote green development of the whole steel & iron industry.
