In the process of feed processing, raw material cleaning is one of the important sections. Impurities in raw materials not only affect the quality of finished feed products, but also cause damage to processing equipment, cause wear and tear of parts, reduce service life, and affect production. Therefore, a correct understanding of the cleaning process and equipment can ensure product quality and enable smooth production.
1. Design of cleaning process
1) Reasonably select cleaning equipment according to the characteristics of raw materials. Due to the difference in fluidity and sieving capacity between granular raw materials and powdered raw materials, cylindrical primary cleaning screens are usually used for granular raw materials, cone powder cleaning screens or flat rotary screens are used for powdered raw materials, and cones are usually used for cakes and dregs raw materials. Clean the sieve.
2) Determine the production capacity of the cleaning equipment according to the workshop production scale. Usually the production capacity of cleaning equipment is about 30% larger than the production scale;
3) When selecting cleaning equipment, try to use equipment that is small in size, convenient to change screens, good in sealing, and high in efficiency;
4) Ventilation and dust removal issues should be considered during process design to ensure workshop environment and sanitation;
5) According to the principle that is conducive to the cleaning efficiency of cleaning equipment, the position of various cleaning equipment in the process must be reasonably arranged. For example, the magnetic separation equipment is usually placed after the primary cleaning equipment.
2. Selection and use of cleaning equipment
There are three types of cleaning equipment commonly used in feed factories: grid screens, primary cleaning screens and magnetic separation equipment.
1) Grid screen
The grid screen is generally placed at the discharge opening and is the first link in the cleaning process. Its main function is to initially clean up large debris in the raw materials and protect the safety of subsequent conveying equipment and the workers.
The gap of the grid screen should be determined according to the geometrical size of the material, the corn and powdered auxiliary materials should be about 30 mm, and the gap for the cake materials should be about 40 mm, and at the same time, a certain strength should be guaranteed. It is usually welded with flat steel or 10 mm round steel with a thickness of 2 to 3 mm and a width of 10 to 20 mm. It should be fixed during installation, and an inclination angle of about 8°～10° should be ensured to facilitate the pouring out of the material in the bag and reduce the labor intensity of the blanking worker.
In the course of use, the sifted debris should be cleaned up in time, so as to effectively achieve the purpose of preliminary cleaning.
2) Preliminary cleaning
The primary cleaning screen is the main equipment in the cleaning process. It is used to clean the non-magnetic impurities in the raw materials. Its performance and process parameters directly affect the cleaning effect. Due to the difference in physical properties between pellets and powders, such as fluidity and sieving capacity, different raw materials should be used for different primary cleaning sieves.
SCY series cylindrical primary cleaning screens are widely used in the cleaning of granular materials because of their high output, low power consumption, simple structure, small footprint, and convenient screen change.
The SFJH series plane rotary screen is also used for the cleaning of powdery raw materials. The screen body is a flat type. Its movement combines circular movement, elliptical movement and linear reciprocating movement, which increases the sieve length of the material, so its output is large and the efficiency is high. , The power consumption is small, and the screen is equipped with a screen surface cleaning device, which can replace the screen body from above, which can effectively prevent the screen hole from clogging and reduce the area occupied.
The following points should be paid attention to when selecting the primary cleaning screen:
①The appropriate sieve holes should be selected according to the physical characteristics and geometric dimensions of the raw materials;
②Check whether the screen cylinder or the screen surface is intact or not, otherwise the cleaning effect will be affected;
③It should be equipped with adjustable dust suction volume. Under normal circumstances, the air suction volume of each initial cleaning screen is not less than 50m3/h, and a butterfly valve is installed at the appropriate position on the suction pipe to facilitate air volume adjustment;
④ Sufficient production capacity should be ensured.
3) Magnetic separation equipment
The permanent magnet cylinder is simple in structure, small in size, flexible in installation, low in price, no power required, and the iron removal efficiency is as high as 99%, so it is widely used, but it requires manual cleaning of impurities on a regular basis.
Pay attention to the following points when selecting magnetic separation equipment:
①In order to prevent large impurities from entering the magnetic separation equipment and causing blockage, it should generally be installed after the initial cleaning;
②The permanent magnet cylinder should be installed in the vertical slide pipe, and the height of the vertical slide pipe above it shall not be less than 400 mm to prevent the material from deviating and affecting the iron removal effect;
③There are certain requirements for the flow rate and thickness of the material in the slide pipe with the magnetic box installed. Generally, the material flow speed should be controlled within 0.1～0.12 m/s. The thickness of the material varies due to the difference in its fluidity. It should be controlled at about 10mm for pellets and 6mm for powders;
④ The adsorbed magnetic impurities in the magnetic separation equipment should be cleaned regularly, and the removed impurities should be treated in time to prevent them from entering the material again;
⑤Should choose to have sufficient production capacity.