Material selection of impeller cover of flotation machine
Writer： admin Time：2020-04-02 11:40 Browse：℃
Flotation machine is a commonly used equipment in beneficiation production time. It has many types, models and specifications, including aerated mechanical agitation flotation machine, self-aspirating mechanical agitation flotation machine, and pneumatic flotation machine. Since the material processed by the flotation machine is usually a slurry containing a large number of solid particles, the components of the flotation machine blades, the flotation machine cover and other components are very worn and corroded. It is necessary to choose some materials with good wear resistance, and Perform regular replacement. The following briefly introduces the material selection of the flotation machine blade and cover plate together with the wear mechanism.
The impeller rotates at a high speed, creating a negative pressure in the central area, the air in the air duct is sucked in, and the slurry is sucked in from the side holes or cover holes at the same time, forming a solid, liquid, and gas three-phase flow. Under the action of centrifugal force, the solid and liquid When the three-phase gas flows outward, passing through the cover screen, the flow rate changes suddenly, the fluid is divided, and the gas phase becomes fine bubbles. This cycle makes the solid, liquid, and gas three-phase mixed uniformly, and the bubbles become a dispersed slurry mixture. . Due to the different pressure distribution, movement direction and velocity of the slurry, the wear of the impeller and the cover plate varies greatly. The wear of the impeller mainly occurs on the outer facing surface of the blade, the outer edge of the disc, and the bottom of the disc. Zone A has the highest flow velocity and the highest relative velocity to the slurry. The streamline direction changes from the direction following the impeller to the direction parallel to the cover grid. This change in flow direction causes the slurry to have the largest impact on the blade's outer facing surface. At first, the right angle of the upper edge is worn away, and then it develops downward. The outer wear of the disc is caused by the relative movement of the pulp and the disc, and it may also be caused by friction with a false bottom with too little clearance. Of course, the further away from the center, the higher the relative speed of the disc and the pulp, and the greater the wear caused thereby. The wear of the cover plate mainly occurs on the inner edge of the grille. The slurry flow direction in this area is forcibly changed. The inner edge is strongly impacted, causing crescent-type wear. After the blade and cover plate are worn, the clearance increases, the cutting effect on the pulp decreases, the bubbles become thicker, the degree of solid, liquid, and gas three-phase mixing decreases, and the degree of bubble dispersion decreases. When the abrasion is severe, the flotation index will be significantly affected. The selection of the material of the flotation machine impeller should meet the following conditions: good abrasion resistance; thermal stability at 20-60 ℃; a certain impact strength; the price of raw materials can be accepted for production.
The flotation machine impeller cover is composed of a vacuum chamber to cause negative pressure, so that the pulp flows and sucks air. The performance of the flotation machine mainly depends on the impeller cover. The quality of the impeller cover directly affects the working efficiency of the flotation machine and Beneficiation index. In the past, the material of the impeller cover plate of the flotation machine was usually cast iron, but there were the following problems:
1, the cover and impeller have a short service life: the impeller and the cover of the flotation machine have always used cast iron materials. Although the hardness of the cast iron material is high, the brittleness is large, it cannot bear the impact load, and the erosion resistance is poor. In the flotation process, due to the erosion and grinding of the ore and the corrosion of the flotation agent, its service life is short. Generally, the set of impeller cover of each flotation machine must be replaced for a maximum of 3 months.
2. Large amount of maintenance and replacement of the impeller cover: The impeller cover of the flotation machine needs to be replaced every 3 months, and the amount of equipment maintenance is large, which seriously affects normal production.
3. High input cost of spare parts for the impeller cover: At present, the cast iron impeller cover of the flotation machine is based on the 2011 market price. Each 6A model is 3076 yuan, and the 6A retrofit model is 6036 yuan. The production cost is high, which is not conducive to cost control management.
4. A certain impact on production indicators: cast iron material impeller cover plate has poor abrasion resistance and corrosion resistance, and is easily corroded by ore sand impact friction and flotation agent during the production process. When the impeller cover plate is used for a period of time, when the impeller cover plate is worn or worn, the gap between the impeller and the cover plate increases, resulting in insufficient flotation aeration volume and insufficient stirring force, and the flotation slurry flow is not smooth, and the flotation liquid appears. The negative phenomena such as "turning flowers" and low flotation froth have a great impact on the stability of the flotation index.
During the operation of the flotation machine, the blades rotate at a high speed, and a certain negative pressure is generated in the central area of ??the blade. Due to the negative pressure, the air duct continuously sucks gas to the outside, and the cover plate holes and side holes continuously suck in the slurry, thereby forming a solid -Liquid-gas three-phase flow. Under the action of inertial centrifugal force, the three-phase flow continuously moves to the outside. When passing through the cover grid, the flow rate changes abruptly, the fluid is divided, and the gas phase becomes fine bubbles. During the operation of the flotation machine, solid-liquid-gas three-phase fluid, solid-liquid two-phase fluid and single-phase fluid have a strong impact on the blade and the cover plate, resulting in strong impact corrosion. In addition, due to the existence of sulfide and other acidic minerals in the pulp slurry, or the requirements of flotation pH, the pulp exhibits a certain acidity or alkalinity, and different acidity and alkalinity will cause chemical corrosion to the blades and the cover plate. Practice and research show that the corrosion of the flotation blade and the cover plate is not uniform. The corrosion of the blade mainly occurs on the outer facing surface of the blade, the outer edge of the disc, and the point of the disc. The abrasion of the flotation machine cover plate mainly occurs on the inner edge of the grille, causing crescent-shaped corrosion.
For the selection of the material of the flotation blade and cover, the following requirements should be met:
1. It has good abrasion and corrosion resistance, for the reasons mentioned above.
2, with thermal stability above 20 ~ 60 ℃, this is because many flotation reagents require higher temperature conditions to work.
3. It has a certain impact strength. This is because the ore slurry contains many ore particles, and it will have a strong impact on the blade and the cover plate during the stirring process.
4. The price is in an acceptable range. This is because the cost of the flotation itself is high, and the flotation blades and cover plates are wearing parts and need to be replaced frequently, so the price needs to be in a lower range. In industrial production, the materials of the blades and cover plates of the flotation machine include cemented carbide, silicon carbide, ultra-high molecular polyethylene, polyurethane, wear-resistant rubber and so on.
The above is the question of how to choose the impeller cover material introduced by Chaishang Trading Co., Ltd. I hope it can help you. For other questions about the impeller cover, please refer to other content on this site, or call for more information.
