With the development of iron and steel technology, blast furnaces have new requirements for pellet production and quality. Compared with the traditional pelletizing process, the use of a large number of additives also increases the corresponding grinding system, such as anthracite (or coke powder, petroleum coke) grinding system, limestone (dolomite) grinding system, bentonite grinding system system etc. Among them, in order to improve the quality and metallurgical properties of the pellets and supplement the shortage of SiO2 in the iron concentrate, a certain amount of acidic flux, such as olivine, serpentine, and silica sand, will be added. As a kind of acidic flux with high hardness, silica sand is the most difficult to grind. What are the requirements for pelletized silicon powder? What kind of mill is used for silica sand grinding for pellets? This article will explain it in detail for you today.
What are the requirements for pelletized silicon powder? Silica sand is a hard, wear-resistant and chemically stable silicate mineral with SiO2 as the main mineral component and a particle size of 0.020-3.350 mm. Its color is milky white, light yellow, brown and gray, hardness 7, brittle without cleavage, shell-like fracture, oily luster, relative density 2.65, insoluble in acid, slightly soluble in KOH solution, melting point 1750°C. The requirements for silica sand grinding powder are that the grain size should be<0.15mm, and the moisture content should be <10%. -200 mesh accounts for 60%. The requirements for pelletized silicon powder are as follows: specific surface area 4500c㎡/g, -325 mesh accounted for 90%, -200 mesh accounted for more than 90%, water content 5%, silica content greater than or equal to 90%. So, what kind of grinding mill can be used to grind silica sand to meet the requirements of pelletized silicon powder?
In industrial production, it is believed that rollers, vertical mills and ball mills can all be used for the production of silica sand powder, so let’s compare and see which equipment is used for the best grinding effect of silica sand:
1. Roller mill: The theoretical basis of the roller mill is the theory of laminated crushing. When the roller mill is working, one roller is fixed on the machine base, and the other moving roller moves on the machine base in a small range. The silica sand enters the crushing chamber of the roller mill and is The silica sand is compacted and crushed, and the ground silica sand is discharged out of the machine in the form of flakes.
①The output of a single machine is high, and the production capacity reaches 1000 tons/hour.
② High energy consumption per unit.
③ Small footprint.
The investment is large, and the particle size of the product is not fine enough. Secondary grinding is required to meet the requirements of pelletized silicon powder.
2. Vertical grinding mill:The motor drives the grinding disc of the vertical mill to rotate through the reducer, and the silica sand enters the center of the grinding disc through the feeding device, and the silica sand is ground after repeated rolling under the action of centrifugal force.
①It integrates grinding, drying, grading and conveying, and has a high degree of automation.
②Adjustable grinding fineness, high powder selection efficiency.
③little wear, low steel consumption.
3. Ball mill:After the silica sand with a particle size of 0.020-3.350mm is ground by a ball mill, a silica sand fine powder of about 0.074mm can be obtained, which can then be used in pellet production and other processes.
advantage:The silica sand powder after grinding is relatively fine, and the initial investment in equipment is low.
shortcoming:It is easy to over-grind, resulting in high fine powder content. the equipment occupies a large area and consumes a lot of energy.
From the above comparison, it can be seen that the double roller is used as a silica sand grinding equipment, although the production capacity is relatively large. However, the system investment is high, and the particle size of the strict product is difficult to meet the requirements of pelletized silicon powder, and the quotation is relatively high. The powder particle size of the ball mill is relatively fine. Although the initial investment in the equipment is low, the equipment occupies a large area, and the loss of steel balls is large, and the energy consumption is high, resulting in high equipment operation and infrastructure costs. Silica sand vertical mill integrates drying and grinding powder, low powder cost, low humidity, low energy consumption, and adjustable fineness. The content of fine silicon powder above 325 mesh can be controlled at about 3%, which can better meet the requirements of pelletized silicon powder . In addition, the silica sand vertical mill adopts negative pressure production, the air volume is recycled, the continuity is relatively good, and the system design is relatively reasonable. The dust concentration inside the factory building of the silicon powder processing device is very low, and there is no phenomenon of flying silicon dust, which fundamentally eliminates the possibility of dust explosion in the silicon dust space.
Therefore, the silica sand vertical mill is an ideal equipment to meet the requirements of pelletized silicon powder. Guilin Hongcheng is a manufacturer of silica sand mills. The HLM series of silica sand vertical mills we produce have been widely used and recognized in the market. If you have relevant needs, please leave us a message to learn more about the equipment.