Since there are many factors that affect the production capacity and granulation effect of hammer mills, there is no theoretical calculation formula that summarizes various factors so far. In actual work, production capacity can generally only be measured through experiments and comparisons.
The main factors affecting the production capacity and granulation effect of the hammer mill are as follows:
1. The weight, shape and material of the hammer
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 crushing effect. But the heavier the weight of the hammer, the greater the centrifugal force generated by the rotation, which also increases the load on the rotor and other parts of the hammer mill. On the contrary, if the hammer is too light, the kinetic energy of the hammer will be small, the crushing ability will be weakened, and even the hammer will be prone to overload during work, thereby accelerating the wear of the pin.
The shape and material of the hammer also have a certain influence on the granulation effect. The "T"-shaped hammer has a sharp impact surface on the top of the hammer, so it not only has a good impact effect, but also has a better tearing effect than square, stepped, and three-convex hammers. In addition, if the hammer is not wear-resistant, the broken effect of the worn hammer will be poor, and the resulting rubber particles will be larger and uneven, which will affect the drying of the rubber particles.
2. Rotation speed of the rotor
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 smaller the size, but the increase in the speed, the load of the motor, the vibration and noise of the machine will increase, and the strength of the machine parts and the balance of the rotor will also be required. The rotor speed of the domestic CM·550X 500 hammer mill has been increased from 2000r/min to 2500r/min. The comparative test results also show that the rotor speed cannot be increased excessively. Because the 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 at 2000r/min.
3. The opening rate of the discharge screen
Under the condition that the total area of the discharging screen is constant, the opening rate is related to the size of the opening, the number of holes, the distance between the holes and the arrangement of the holes. As the opening rate of the discharging screen increases, the discharge amount 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 (at least equal to) the feed volume, otherwise the machine will be blocked, and once blocked, the rubber particles that cannot be discharged from the machine will roll. Into a big rubber ball, the motor will be overloaded and burned out.
Under the condition that the total area and aperture of the discharging screen remain unchanged, as the hole spacing decreases, the number of openings will increase, and the opening rate will increase, which is beneficial to increase the discharge volume and reduce power consumption. However, in order to ensure the strength, rigidity and service life of the discharge screen, the hole spacing should not be too small, otherwise, the discharge screen will be accelerated by the impact, grinding and corrosion of the residual acid from the rubber material. Under the condition that the opening rate of the discharging screen remains unchanged, with the increase or decrease of the hole diameter, the rubber particles produced will also increase or decrease, and the rubber particles of different sizes have different drying effects, so choose The pore size must also be determined due to dry tests.
4. Pretreatment methods for different properties of rubber and agglomerates
Different properties refer to the coagulation concentration of latex, the hardness and water content of the clot, etc. They have a certain influence on the granulation effect. When producing fresh latex standard rubber, the coagulation concentration of latex is generally controlled at 20-25%. When the coagulation concentration is constant, the pretreatment method of the clot is different, which has a great impact on the granulation effect. Practice has proved that using a crepe machine (dewatering machine) to treat the clot, although the rubber particles produced are relatively fine, However, the water content of the rubber particles is high, and they are easy to bond into agglomerates after being heated. The drying time is longer, and the phenomenon of sandwiching or sticking may occur. The film rolled by multiple creping machines is relatively thin (the thickness is generally 5 —6mm), the surface is rough, and the film has many small pores. This is not only good for granulation, but also the produced rubber particles are uniform, have low water content, are not easy to stick and form agglomerates, and the drying time can be shortened. Therefore, most factories currently use two to three crepe machines for pretreatment of rubber materials.