The application of vibrating screens in the feed processing industry is mainly concentrated in two aspects:
1. Clean up impurities in raw materials;
2. The raw materials or products are classified according to the particle size (including the cleaning of impurities in the raw materials, the classification of the crushed materials, the cleaning of impurities in the powder before granulation, and the classification of the granulated products.)
First,the cleaning of pellets
Feed mills are used to refer to materials that need to be crushed as pellets, including cereals and terpenoids.
The raw materials of cereals come directly from the field, and the impurities contained are relatively complicated. There are mainly two types of impurities: one is impurities larger than the grain size of the grain raw materials, such as stones, corn cobs, hemp tablets, straw, hemp rope, plastic sheets, etc.; It is a soil with a small particle size and fine sand. At present, the most common grain cleaning equipment in feed mills is the cylinder primary clearing screen, which is characterized by large output, low power consumption and high removal rate of large impurities, up to 99%.
Second, the cleaning of powder
Raw materials that do not need to be pulverized are generally referred to as powders. There are many kinds of powders in feed mills, and the dosages are different. Most of them are by-products of the grain industry or other industries. Therefore, the impurity content is not high, and the large impurities such as hemp rope and sack pieces mixed in the process are mainly used.
Third, the classification of crushed materials
The secondary pulverization process requires the use of screening techniques. In the production of common livestock and poultry feed, a rotary screen or a vibrating screen is generally used to form a closed loop, and the sieved material is returned to the crusher, and the sieved material enters the batching bin. Generally, the mesh size is φ1.2 mm.
Fourth, the classification of pellet feed
In the processing of pellet feed, in order to increase the output of the granulator and reduce the energy consumption of granulation, large-diameter die holes are often used for production and then broken into small particles. After the particles are broken, they are classified, and the fine powdery material (the unformed powder in the granulation process or the powder produced during the crushing process) and the excessively coarse particles (the particles which are not sufficiently broken) are separated to make it enter. The particles in the finished product processing section meet the product particle size requirements. The granule feed is graded by using a two-layer sieve surface, the upper sieve surface is subjected to a reflux crusher, the lower sieve mesh is returned to the granulator, and the intermediate layer is a finished product. It can be seen that the size of the mesh used in the grading screen directly affects the product size.
Screen size of products with different grain size specifications: The particle size (mm) of the graded products is 2.40, 3.20, 4.00, 4.75, 6.35, 9.50, 12.7 and granules, and the corresponding sieve size (mm) is 1.65. 2.23, 2.92, 3.89, 5.21, 8.97, 11.5 and 1.16. It can be seen that to control the particles of a certain particle size not to pass through the mesh, a mesh diameter smaller than the particle size value should be used.