An important link in cement production is grinding (stone or clinker grinding into fine powder), the traditional ball mill, large energy consumption, now the most used is vertical roller mill, the advantages of this mill is energy saving and high efficiency, but it has a feature is that the feed and discharge are from the upper part of the mill, simply said that the stone falls into the mill from above, the fine powder material grinding from above with high negative pressure.
The air will draw out the powder. So there is a problem, how to feed the raw materials in the normal environment (stones and clinker, etc.) into the mill at the same time without leaking air, and some problems need to be solved.
(1) The raw material can not leak into the mill, because the finished product is extracted from the mill, once there is air leakage, it will destroy the original negative pressure value, so that the negative pressure decreases, the result is insufficient pumping, the powder will have a part of the retention in the mill, destroy the grinding capacity of the mill, reduce output and increase power consumption. (2) The above negative pressure is not a stable and constant value, due to the changes in the material, the different degree of wear resistance of the material, the influence of the conveying mechanism, the water content of the material and so on, the negative pressure environment is constantly changing, and some changes can reach 100%. In such an environment, the stones and sand particles in the material will be blown all over the sky, how to achieve dynamic accurate measurement of the material in such a strong wind is a relatively difficult subject.
(3) If the system leaks, no matter how much air leaks in, it will be mixed into the finished product (powder). The air mixed with the powder will eventually be separated from the powder, and the air in the powder will be separated from the dust collector to prevent dust. The obvious reason is that the more air mixed in (pumped in), the more dust pollution produced when the powder and air are separated.
(4) When the water content of the material is too much, a part of the material will be attached to the equipment to cause blockage.
Summing up the past experience, now our company developed a new sealing apron feeder key equipment is the "sealing mechanism", now the use is called flap valve and rigid split wheel discharger, their principle is to use the fixed gap between the steel plate and the shell to make the material (raw material) can fall smoothly while the material will fill in the gap between the above. To achieve a certain sealing effect.
There is no problem in the use of this process in foreign production lines, because the control of raw materials in foreign production lines is more strict, that is, the particle size of raw materials (particle size) is more consistent and uniform. As long as the appropriate "gap" of the selected equipment, it can ensure the feeding and sealing at the same time, which refers to the cement production line in developed countries, the material is not uniform in the production line in domestic and underdeveloped countries, the particle size difference of the material is sometimes dozens of times or hundreds of times, that is, the particle size of the raw material has a diameter of 1mm and a diameter of 200mm (brick size) between. In the use of such raw materials, it will be difficult to choose the equipment described above
Gap ", this size particle raw material, and can achieve the degree of airtightness (complete seal), but also can accurately measure the dynamic flow of the material, can be stable and stable, can set the output of the sealed quantitative feeder, at the same time can be remote control, proving that it can perfect solve the problem of this key process of cement production. Because in developed countries, the cement production process in the grinding process, the use of vertical mill, due to the strict and standardized raw materials, so there is no problem, there is no need for transformation, so we have not found this form or similar products abroad. This equipment is a new type of high-precision dynamic airtight measuring equipment, which has been combined with the research and development of the relevant dynamic measuring products and the specific requirements of comprehensive solution of each link. Sealed apron feeder is a special feeding equipment designed according to the production process of vertical mill, which solves the problems of stuck material, empty material operation, skip stop due to material overload and loose seal of feed valve in vertical mill production. It has the following characteristics:
(1) It has the advantages of long durability, simple maintenance and low maintenance cost. The material of the direct contact part of the chain plate and the material is made of wear-resistant steel, but the higher the hardness of the steel, the more difficult it is to process and form, and it is easy to crack. The results of testing a variety of materials should not only ensure toughness but also have high wear-resistant properties. The wear-resistant sealing method of apron feeder is to add a curved surface to each chain plate, and fix 2 wear-resistant steel bars (square or round). The material falls into the chain plate from the feed port, and due to the natural particle grading effect of the material, the fine material and fine debris will automatically fall onto the bottom chain plate. The above two steel bars have a hard fixation on these powder particles without flowing away. The surface of the entire chain plate is covered with a layer of granular material, and the large granular material above is no longer in contact with the chain plate, effectively preventing the chain plate from being worn. The alloy structure of the chain plate and independent lubrication system as well as the structure and transmission form of the equipment make the maintenance and repair of the equipment more convenient and simple, and the damaged chain plate and slot plate can be replaced separately.