Research on Crusher Hammer

Hammer mills are widely used due to their simple structure. It is a high-power-consumption machine in the feed plant, which generally accounts for 2/3 of the total powder production energy and accounts for more than 1/3 of the total energy production of the pellets. Therefore, how to make it more efficient and energy-saving is an important research topic in feed machinery. Many people paid a lot of effort for this, deduced a lot of formulas, and made a lot of experiments. Hammer is the core working part of the crusher, feed crushing depends on it. It has the greatest impact on the efficiency of the mill, so people have done special research on the hammer.

First, the status of research on the hammer of the crusher

What exactly is the crushing process of the feed in the crusher? The West Germany Institute of Science Films produced a film for this purpose. They were taken at a shooting speed of 7,500 frames per second per second, with an exposure time of 0.00001 seconds. From the single screen of the film, the whole process of smashing corn in the crushing room can be clearly seen. The conclusion drawn from this film is that corn requires only a small amount of energy to be broken when it is subjected to a positive impact; however, when it is subjected to an eccentric impact, much more energy is required to break it. The vast majority of the corn kernels in the crushing chamber are eccentric impacts, which inevitably wastes a lot of energy. This is why the crusher does not use much energy. This means that in order to increase the efficiency of the crusher, the frontal impact rate must be increased. The only way is to increase the thickness of the hammer.
Based on Rumpf's basic research on crush theory and the arguments of Herfz and Kranz, Friedish in Germany derived formulae for some factors that affect the ultimate stress of fragmentation of a material (the formula is very complicated, so it is omitted here). According to this formula, the smaller the overall radius of curvature r of the impact point during the crushing process, the easier the feed will break. The r value is composed of the radius of curvature r1 of the feed pellet and the radius of curvature r2 of the hammer, and the relationship is:
The radius of curvature r1 of the hammer can be considered as half the thickness of the hammer. When the feed type has been selected, the radius of curvature r1 of the particles is a constant value. In order to increase the crushing efficiency, it is necessary to reduce the r value. The only way is to make r2 smaller, that is, using a thinner hammer. Richard used hammers with thicknesses of 1/16, 1/8, and 1/4 inch, respectively, in experiments to crush corn. The following conclusions were obtained when other conditions were the same: 1/16 inch thickness A 1/8-inch hammer can increase efficiency by 23%; a 1/4-inch hammer can increase efficiency by 48%.
Liu Manru and others from the Chinese Academy of Agricultural Mechanization Science also conducted this experiment. He or she used a hammer with a thickness of 1.6, 3, 5, and 6.25 mm to make a comminution corn test. The result was: 1.6 mm hammer ratio 6.25 The efficiency of mm is increased by 45%; the efficiency is improved by 25% compared to 5mm.
The above two sets of experiments have proven that the hammers are thin and efficient. Thus Friedish's theory is recognized as a traditional theory and continues to this day. However, this theory and the conclusion of the film are contradictory.
People also made a lot of articles on shapes and materials, but they could not solve the above-mentioned contradictory conclusions. Since then, people's research on hammers has made little progress. The most commonly used is still a rectangular hammer. The professional standard and industry standard of the People's Republic of China "Hammer mill hammer" specifies that the hammer type is rectangular. Both Yueyang Zhengda and Wuhan Huamei are American crushers. Their hammers are also rectangular. Zhuzhou Xiangda's hammers imported from Switzerland are still rectangular.
So there are no articles on the hammer to do?
Practice is the sole criterion for testing truth. To do experiments for one purpose, the methods are different and the conclusions are reversed. This can only show that both methods have one-sidedness. To resolve the contradiction, we must start by analyzing contradictions. What the West German film sees is the shattering of corn in the shredding room. From the inside, the conclusion is correct. Both Friedish's theory and Richard's and Liu Manru's experiments were based on the number of corn husks detached from the crushing chamber and the conclusion was correct. If we can find a design scheme that can both increase the positive impact rate and enable the particles that have reached the particle size to come out of the sieve as soon as possible, then the above two opposing conclusions will be unified, so that the performance of the mill will be very good. Greatly improved. The T-shredder hammer I designed is designed from this idea, which can make two opposite conclusions unified.

Second, the characteristics of T-type grinder hammer

1. Increase the area of ​​the end of the hammer to increase the front impact rate.
After the material enters the crushing chamber, due to the centrifugal action, the feed makes a circular motion near the screen and the tooth plate, so that the impact portion of the hammer is at the end of the hammer. If the entire hammer is thickened, the frontal impact rate can be increased, but the area where the non-working part pushes the air is also increased, so that the air circulation speed is accelerated, thereby reducing the relative impact speed of the hammer on corn and reducing the corn's Breaking efficiency. If only the area of ​​the working part is increased and the area of ​​the non-working part is reduced, both the front impact rate and the air circulation speed are increased, thereby increasing the relative impact speed of the hammer on the corn and increasing the crushing efficiency of the corn. .
2. Add a majority of slopes to reduce the incidence of powder on the mesh. The end of the standard hammer is straight, and the corn, after being impacted by the hammer's frontal impact, returns almost at a right angle to the strike surface of the hammer. There are two problems with this movement route of corn granules: (1) The granules cannot escape from the range of hammer strikes quickly. Since the crumb speed is much slower than the speed of the hammer, it will be struck by the hammer that catches up quickly; (2) The angle of incidence of the granules to the mesh is large, and the crumbs which are much smaller than the diameter of the mesh are also It does not necessarily go out through the screen, jumps back to the hammer and impacts again after it hits the edge of the screen. Both of these conditions can cause unnecessary fine powder, reduce production efficiency, and waste energy. If the impact site is given a bevel angle α, the corn and the impact surface of the hammer impact, so that the impact of the hammer chip corn grain reflection to the direction of the screen, greatly reducing the angle of incidence of corn grains on the sieve hole. This speeds up the discharge of the powder and reduces repeated impacts. Therefore, the efficiency is improved, the energy consumption is reduced, and the uniformity of the powder particles is increased.
3. T-type hammer installed less than the standard hammer. As the working area of ​​the hammer is increased, the installed capacity of the hammer is reduced, and the weight of the crusher rotor is also reduced, thereby reducing the internal energy consumption of the crusher.

Third, T-type grinder hammer efficiency and energy-saving effect

The T-type crusher hammers can achieve remarkable efficiency and energy-saving effects when tested on various hammer mills. The existing hammer crusher has the same structure except that the spacer length changes. If the crusher rotor is redesigned with a T-type crusher hammer, the rotor can be further reduced, and the internal energy consumption of the crusher can be further reduced, thereby further enhancing energy efficiency.
1. Comparative inspection (test) test data
2. Economic Benefits It is not difficult to see from the data in the above table that the T-type hammer has 11.4% to 15.4% higher productivity than the standard hammer; the productivity is increased by 12.3% to 18.3% in the pure working hours, and the number of hammers is reduced by 1/2. ~3/4. Taking the SFSP11230 crusher as an example, a pair of hammers can grind 450 tons of corn, and the electricity price is calculated at 0.7 yuan per degree. A standard T-hammer hammer per month saves 440 yuan in electricity and saves 13.9 hours of working hours. Significant.

Fourth, the conclusion

Through the above comparison experiment, the conclusions are as follows:
1. T-type grinder hammer, hammer head, hammer body in two parts. Hammer head is impact material part. Its size varies with the type of crusher and it has an optimum value.
2. The hammer impact surface has an α angle with the longitudinal axis of the hammer. When α = 0, the product size is fine, but energy efficiency cannot be increased. When the value of α is within the optimal range, both energy efficiency and particle size uniformity are improved.
3. T-type grinder hammer installed only the original number of 1/2 to 1/4, the rotor weight is reduced, reducing the internal energy consumption of the grinder.