By: FTM Machinery April 20th,2021
The froth flotation method has become one of the main methods of separating mineral raw materials in the world, and the flotation machine is an important equipment in the flotation process. The current mechanical flotation machine equipment is widely used, and the impeller system is one of the important working elements of the mechanical stirring flotation machine, which is composed of cover plates, middle blades and stators.
Due to the long-term contact with chemicals and the erosion of mineral pulp, the impeller becomes one of the vulnerable parts of the flotation machine, which will affect the aeration capacity and uniformity of the flotation machine, deteriorate the flotation effect, and increase the maintenance of the equipment. Therefore, it is necessary to understand the causes of flotation machine impeller wear and preventive methods.
1. Causes of flotation machine impeller wear
1.1 Erosion and wear
The solid particles mixed in the slurry impact the flow surface, causing the surface of the material to undergo elastic deformation and plastic deformation in sequence. After repeated impacts of the solid particles, the material undergoes fatigue failure and causes the surface material to fall off. When the wear is slight, the impeller has concentrated scratches and pitting ; when the wear is severe, the surface of the impeller is corrugated or grooved; when the wear is severe, the parts may perforate and fall into pieces.
1.2 Combined effect of cavitation wear and erosion wear
When the impeller rotates to remove the pulp, air pressure will be formed and bubbles will be generated. After the bubbles are formed, they move with the slurry, and the bubbles that contact the inner wall of the impeller are collapsed due to the increase in pressure, thus forming a micro jet toward the wall. This microjet completes the directional impact on the surface of the material in a very short time, and the force generated is equivalent to the effect of 'water hammer'.
The metal surface is gradually fatigued and peeled due to impact, causing material loss. The solid particles in the slurry are driven by cavitation and impact the metal surface. This damage includes both the impact of micro jets and the impact of solid particles, which is a combined effect of cavitation wear and impact wear.
2. Improvement of flotation machine impeller wear
2.1 Change the blade exit angle
Considering wear, the thickness of the inlet edge of the blade is generally larger. For flotation medium with strong abrasive property, a smaller blade outlet angle can minimize particle impact on the blade working face, and the blade outlet angle is generally selected as 30°-40°.
2.2 Adjust the width of the blade outlet
In order to reduce wear and tear, increase the width of the blade outlet, which reduces the relative speed at the impeller outlet and reduces the wear of the impeller on the one hand, and reduces the jet flow (wake effect) at the impeller outlet on the other hand, so that the outlet slurry velocity distribution is uniform.
2.3 Reduce the number of blades
The number of blades of the flotation machine is generally 4~7. Fewer blades can reduce the congestion at the inlet of the impeller, thereby reducing the wear of the pump.
2.4 Control the size and hardness of solid particles
The size and hardness of solid particles in the slurry are important factors that affect the wear behavior of impeller materials. The increase of particle size and hardness will lead to the increase of erosion. Therefore, in the daily work process of the flotation machine, the particle size of the flotation material should be strictly controlled to achieve the purpose of reducing the wear of the impeller of the flotation machine.
The above are the causes of flotation machine impeller wear and measures to reduce the occurrence of wear. In addition, the high quality of the flotation machine impeller itself is also an important factor in increasing the life of the flotation machine impeller. It is recommended to choose a qualified flotation machine equipment manufacturer to purchase a flotation machine. While ensuring the quality of the flotation machine, choose equipment that is more in line with the scale of the concentrator, so as to reduce the cost of beneficiation and increase the rate of return on investment.