100 mesh sizes in hammer mills

Hammer mill is similar to hammer crusher used in general industry. The main purpose of the hammer crusher is to turn solid materials into small pieces of material under the action of mechanical force. Therefore, it is widely used in China’s metallurgy, coal, construction engineering and feed processing sectors. Mechanical operation to overcome the internal cohesion of the material and split it is called crushing or fine grinding. Generally speaking, large pieces of material are broken into small pieces of material, called crushing, and turning small pieces of material into fine powder is called fine grinding. Crushing and fine grinding are collectively called crushing. After the solid material is split into small pieces or fine powders, the surface area per unit weight will increase, thereby increasing the reaction speed of its physical and chemical effects.

Working principle of hammer mill

When the rotor of the hammer mill rotates at high speed, the hammer becomes radial due to the centrifugal force (for the rotor of a hanging hammer). The rubber material enters the machine after being pressed by the feeding roller, and is immediately broken into particles by the impact of the hammer and tearing. The granular rubber is discharged from the outlet sieve hole of the machine. Block until the hammer strikes again until it passes through the screen. The hammer mill does not rely on the full energy of the rotor components to break the rubber, but mainly uses the work done by the hammer’s kinetic energy to complete the crushing of the rubber.

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Main factors affecting hammer mill

As there are many factors that affect the production capacity and granulation effect of the hammer mill, so far, there is no theoretical calculation formula that summarizes various factors. In actual work, the production capacity can generally only be measured by experiments and comparison methods.

The main factors affecting the production capacity and granulation effect of the hammer mill are as follows:

The kinetic energy of the hammer is proportional to the weight of the hammer, that is, the heavier the hammer, the greater the kinetic energy of the hammer, and the better the breaking effect. However, the greater the weight of the hammer, the greater the centrifugal force generated by the rotation, which will increase the load on the rotor and other parts of the honing machine accordingly. Conversely, if the hammer is too light, the kinetic energy of the hammer will be small, the crushing capacity will be weakened, and even the hammer will easily be overloaded during work, thereby accelerating the wear of the pin.

The shape and material of the hammer also have a certain effect on the granulation effect. The “T” hammer has a sharp impact surface at the top of the hammer. Therefore, not only the impact effect is better, but also the tear effect is better than that of square, stepped and triple convex hammers. In addition, if the hammer is not wear-resistant, the crushing effect of the hammer after wear is poor, and the rubber particles produced are large and uneven, thereby affecting the drying of the rubber particles.

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Under the condition that the number of hammers is constant, the higher the rotation speed of the rotor, the greater the kinetic energy of the hammer (that is, the kinetic energy is proportional to the square of the speed). The more times the rubber is hammered per unit time, the higher the crushing efficiency and the particles. The smaller and smaller, but the higher the speed, the greater the load on the motor, the vibration and noise of the machine, and the higher the requirements for the strength of the machine parts and the balance of the rotor. The rotor speed of the domestic CM • 550X 500 hammer mill was increased from 2000r / min to 2500r / min. The comparison test results also show that the rotor speed cannot be increased too much. Because the rotation speed is too high, the load of the motor, the vibration and noise of the machine increase, and there is no obvious benefit to the output and the drying of the rubber particles. Therefore, the working speed of the rotor is set to 2000r / min.

When the total area of the discharge screen is unchanged, the opening ratio is related to the size of the openings, the number of holes, the distance between the holes, and the arrangement of the holes. With the increase of the opening ratio of the discharge sieve, the discharge capacity of the screen increases. It should be pointed out that the opening rate of the discharge screen must ensure that the discharge volume is greater than (minimum should be equal to) the feed volume, otherwise the machine will become blocked, and once blocked, the rubber particles that cannot be discharged inside the machine will roll. If a large rubber ball is formed, the motor will be overloaded and burned out.

Under the condition that the total area and hole diameter of the discharge screen are constant, the number of openings will increase with the decrease of the hole spacing, which will increase the discharge rate and reduce power consumption. However, in order to ensure the strength, rigidity and service life of the discharge screen, the hole spacing cannot be too small, otherwise, the discharge screen will be accelerated to wear or damage due to the impact, grinding and residual acid corrosion of the wide rubber. Under the condition that the opening pore rate of the discharge sieve is not changed, as the pore diameter is increased or decreased, the rubber particles produced will also increase or decrease, and different sizes of rubber particles have different drying effects. The size of the pore size must also be determined by the dryness test.

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Different properties refer to the coagulation concentration of the latex, the hardness of the clot, and the water content, etc., and they have a certain effect on the granulation effect. If fresh latex standard rubber is produced, the coagulation concentration of the latex is generally controlled at 20-25%. When the coagulation concentration is unchanged, the pretreatment methods of the clot are different, which has a great impact on the granulation effect. It has been proved that using a crepe machine (dehydrator) to treat the clot, although the rubber particles are relatively fine, However, the water content of the rubber particles is high, it is easy to stick into agglomerates when heated, and the drying time is longer, and the phenomenon of raw rubber or stickiness may also occur. The film rolled by multiple crepe sheeting machines is thin (generally 5 thickness —6mm), the surface is rough, and there are many small pores in the film. This is not only conducive to granulation, but also makes the granules uniform, with low water content, not easy to stick to agglomerates, and shortens the drying time. Therefore, at present, most factories use two to three crepe machines for pre-treatment of rubber compounds.

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