The production method of high carbon ferro silicon is to melt silica, steel chips and carbon reducing agents in the mine and metallurgical electric Shanghai. The carbon reducing agent used is metallurgical coke, and it can also be used as gas coke, semi-coke, blue carbon and anthracite.
Steel scraps are mainly car scraps processed by the machinery manufacturing industry. However, the proportion of steel scrap pile is small, the volume is large, and the transportation is not economical; In addition, the steel chips machined are generally longer, can not be used directly, broken and difficult, and the cost is higher.
In the prior art, iron ore pellets, rolled steel sheet and massive iron ore are also used to replace steel chips as iron containing materials for the production of high-carbon ferro silicon. However, the iron ore materials used in this method are all iron oxides, and in the process of smelting high-carbon ferrosilicon, the reduction of these iron oxides will increase the consumption of reducing agents and heat, resulting in an increase in power consumption.
The processing of new high-carbon ferro silicon is a low-cost method of producing ferro silicon without metallurgical coke, without or less steel filings. The main raw materials used in the production of high-carbon ferro silicon are ferro silicon coke and silica, and no or a small amount of steel filings are added. In addition to carbon, iron-silicon coke also contains a certain amount of iron and silicon dioxide. This is made from high volatile medium binder coal, iron ore powder with low Al2O3 and high SiO2 and a certain amount of silica powder, after mixing, refining in a non-recovery coke oven. In order to make the refined ferro silicon coke have higher reactivity and higher specific resistance, and the crushing loss is small, it is necessary to use a lower coking temperature and a shorter coking time.
According to coal chemistry, amorphous carbon is not only higher than the resistance, but also strong reactivity. The process of coal pyrolysis and polycondensation into coke is the process of transforming amorphous carbon into graphite. The higher the coke forming temperature and the longer the coke forming time, the more the amorphous carbon in coal is converted to graphite. Therefore, the degree of graphitization of coke can be reduced as much as possible by using appropriate thermal system, lower coking temperature and shorter coking time. In this way, the use of high-quality main coking coal can be avoided, and special coke can be obtained to meet the needs of high-carbon ferro silicon production.
In the process of high-carbon ferro silicon coking, a series of pyrolysis and polycondensation of coal occurs, in which volatile hydrocarbons are cracked to produce a large amount of CO and H2 and other gases, forming a good reducing atmosphere, so that the iron ore powder uniformly dispersed in the coal has good reduction conditions, iron oxide in the iron ore is reduced to metallic iron, and the reduction rate of iron oxide is > 95%.
The fixed carbon in coal is not consumed during the reduction process. The reduction results enhanced the structural strength of coke. Silica powder does not change in the coking process, but it plays a role in preventing the graphitization of amorphous carbon and improving the iron-silicon coke ratio resistance. In the water quenching process of iron-silicon coke, part of the metal iron in the coke is oxidized to Fe3O4, that is, because the metal iron is surrounded by carbon in the coke, the reducing gas generated by water and carbon plays a protective role in the water quenching process.
Therefore, there is still most of the metal iron is not oxidized, X-ray diffraction and chemical analysis proved that the metal iron reoxidation rate in the coke is less than 50%, and there is no iron silicate in the iron silicon coke. At the same time, iron silicate is not produced in the process of high-carbon ferro silicon coking. When considering the raw material ratio of iron-silicon coke, the content of iron ore powder is first considered in the coal blending, while the content of silica powder of high-carbon ferro silicon is based on ensuring that the coke has a certain strength and a high specific resistance. At the same time, it is also necessary to consider the residual bonding capacity of coal and the change degree of iron ore powder in the coking process after the addition of iron ore powder.
The method of smelting high-carbon ferro silicon is based on ferro silicon coke and silica as the main raw materials, and in addition, no or less steel chips are smelted in the ore-smelting furnace. The raw material ratio (weight unit) of smelting iron silicon is based on silica 100(weight unit), iron silicon coke 65 ~ 90(weight unit), and steel chips < 18(weight unit).
Among them, iron-silicon coke is broken, 80% of the particle size is 2 ~ 15mm, and no more than 20% of the particle size is less than 2mm. Smelting high carbon ferrosilicon can be carried out in various capacity of ferrosilicon smelting furnace, can produce various grades of ferrosilicon. Compared with the prior art, the first feature of the smelting method of high-carbon ferrosilicon is that the consumption of reducing agent is low, and the silicon content of high-carbon ferrosilicon is high under the same conditions.
In the smelting process, the main chemical reactions in the electric furnace are as follows: Fe3O4 produced in the process of quenching coke is a highly dispersed substance of the new ecology. In the smelting process of ferro silicon, the charge is reduced to metal iron by the CO produced in the reduction process of SiO2 before falling to the furnace cylinder, so the direct reduction reaction of Fe3O4 does not occur in the furnace cylinder. That is, the reduction of Fe3O4 does not consume the carbon in coke, and only the CO generated by the reduction of SiO2 is enough to reduce the needs of Fe3O4. Due to the high CO2 content of the gas generated by the reaction, the combustible component of the gas at the outlet is low, so the flame on the furnace surface is significantly reduced, making the furnace temperature low, not only easy to operate, but also because of the low temperature of the furnace, coupled with the iron silicon coke itself contains relatively low fixed carbon, containing more inert matter, so that the iron silicon coke coal loss is greatly reduced. Therefore, the coal content of reducing agent can meet the requirement of smelting high-carbon ferro silicon according to the lower limit ratio, so the amount of reducing agent is saved.
On the other hand, because the iron-silicon coke contains high SiO2(SiO2 in coal, iron, SiO2 in ore and SiO2 in silica more than 10% of the sum of the three), and is highly dispersed in iron-silicon coke, close contact with the carbon in iron-silicon coke, resulting in good reduction kinetic conditions, easy to be reduced, under the same conditions to improve the silica content of high-carbon ferro silicon.
