A kind of lignite semi-coke reducing agent for industrial silicon production and preparation method thereof

Abstract

The invention relates to a brown coal semi-coke reducing agent used for industrial silicon production and a preparation method thereof, and belongs to the technical field of metallurgy chemical engineering. The brown coal semi-coke reducing agent used for the industrial silicon production is an oblate spheroid with the length being 30-40 mm, the width being 25-30 mm, the thickness being 15-30 mm and the compressive strength being larger than 5 MPa. The reducing agent comprises more than 80 wt% of fixed carbon, 3-15 wt% of a volatile component, smaller than 5 wt% of moisture and smaller than 4 wt% of ash. The ash comprises smaller than 2.4 wt% of Fe. The high-temperature specific resistance (1100 DEG C) is larger than 3500 microhm*m. The reactivity (1100 DEG C) of the reducing agent ranges from 80% to 90%. The brown coal semi-coke reducing agent used for the industrial silicon production is prepared through the method of brown coal rapid carbonization, brown coal semi-coke fine grinding, drainage oil agglomeration selective flocculation deep de-ashing and hot-press forming. The prepared novel brown coal semi-coke reducing agent is low in raw material price, wide in raw material source and good in impurity removal effect, product shaping is achieved, and performance is similar to that of charcoal.

Description

technical field [0001] The invention relates to a lignite semi-coke reducing agent for industrial silicon production and a preparation method thereof, belonging to the technical field of metallurgy and chemical industry. Background technique [0002] Charcoal is an important reducing agent used in electric furnace silicon smelting. At present, the reducing agent used in electric furnace silicon smelting is charcoal. The production of 1 ton of silicon-fixed carbon requires about 1.20t. In recent years, as the country has become increasingly strict on environmental protection, the protection of forest resources has become the consensus of everyone. Therefore, logging and burning charcoal has been controlled, the supply of charcoal is tight, and the price has risen, which has seriously affected the economic benefits of silicon refining enterprises. In order to solve the shortage of reducing agent resources and high cost in the silicon refining industry, domestic and foreign sc...

AI Technical Summary

Problems solved by technology

[0003] 1. The price of petroleum coke is cheaper than that of charcoal. At the same time, petroleum coke has the least ash content among various carbon materials, and the fixed carbon content can reach more than 90%. However, petroleum coke rapidly changes into a graphite structure with large grains as the temperature increases. , the conductivity is enhanced, the reaction ability is reduced, and all petroleum coke is used as the reducing agent. Although industrial silicon can be smelted, the gas permeability of the furnace material in production is poor, the furnace throat is easy to sinter, and processing is difficult, which increases the difficulty of smelting and increases power consumption.

[0004] 2. Bituminous coal is used as the reducing agent, which has large resistance and strong reaction ability. Its chemical activity is almost 5 times that of petroleum coke, and the price is cheap. The main problem is that the large amount of bituminous coal used will lead to sintering of the material surface and poor air permeability of the furnace charge. In addition, the high ash content of bituminous coal will reduce the quality of silicon products

[0005] 3. Using bituminous coal and petroleum coke to partially replace charcoal for metal silicon smelting can reduce the cost of industrial silicon production. However, due to the large difference in physical and chemical properties of various reducing agents for mixed materials, segregation of reducing agents will occur in the molten reduction layer , the consumption speed of each reducing agent is inconsistent, resulting in a large amount of mixed reducing agent and high power consumption

This method consumes a lot of energy, has low efficiency and high production cost

[0010] In addition, the reducing agent used in industrial silicon production, in addition to qualified composition (high fixed carbon content, low ash content), also needs to have a certain particle size and compressive strength: when the particle size of the reducing agent is too large, the charge is prone to segregation, and the reducing agent and The contact area of ​​silica, the raw material for silicon refining, is small, and the reduction efficiency is low; if the particle size of the reducing agent is too small, it is easy to segregate the furnace charge, and cause poor air permeability of the furnace charge, and the reducing agent is easy to blow and burn. The agent can withstand the throwing during the conveying process and the pressure of the charge in the furnace, and has good thermal explosion resistance, so as to maintain the good gas permeability and reactivity of the charge

The current reducing agent for silicon refining is charcoal, petroleum coke, and bituminous coal mixed together and added into the furnace. Inhomogeneity and segregation in the furnace reduce the reduction efficiency

[0011] The existing technologies in the industry have not fundamentally solved the dependence of silicon metal smelting on charcoal. At the same time, the substitutes sought are far behind charcoal in performance and cannot well meet the requirements of industrial silicon production. In the development of coal-based reducing agents, the problem of deep deashing of coal and the problem of product stereotypes and components cannot be effectively solved

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