Basic characteristics of raw materials and finished products
There are tens of thousands of raw materials that can be used as feed. There are hundreds of types that can enter the feed processing plant, but there are thousands or nearly 10,000 kinds of raw materials in a specific feed processing plant. In addition, there are many types of finished products. According to the processing characteristics of raw materials and finished products, they can be roughly classified into the following categories.
1. The components to be pulverized, mainly including grains, oil seeds, and cakes. It is mostly granular, accounting for about 70% to 80% of the total.
2. Various grain and animal processing by-products, such as rice bran, bran, protein powder, soy flour, blood meal, etc., account for about 20% to 30% of the total, and the state is mostly powdery.
3. Inorganic salts with large bulk density, such as sulfate, phosphate, stone powder, salt, etc. Most of these substances are in packaging. Because salt has a corrosive effect on metals and is easy to absorb moisture and agglomerate, it is necessary to pay attention to its characteristics when storing.
4. Liquid raw materials such as molasses, oils, and certain liquid amino acids, vitamins, etc.
5. Drugs and trace components, mainly antibiotics, antibiotics, vitamins, fragrances and so on. These materials are characterized by a large variety, a small quantity, and a high price. Some varieties are harmful to humans. They must be stored in a special place and managed by a special person during storage, and cannot be mixed with other materials.
6. The finished products are powdered, pelletized, packaged and in bulk.
It can be seen from the types of raw materials and finished products that in addition to a small amount of liquid in feed processing, most of them are granular and powdery raw materials. Granules and powders are collectively referred to as granules. In the storage and processing of feed, the following characteristics of the granular body need to be studied.
1. Physical properties of the material
Scattered
Scatter property is the ability of a reaction material to diffuse around in a free state, which is a property of material flow. Powdered and granular materials are roughly divided into:
Powder: 10μm～2.0mm
Granules: 1.0mm to 5.0cm
5.0 cm or more is called a "block", and it is less than 10 μm in the category of colloids.
The granular body has a flow property similar to that of a liquid, and this fluidity appears to be scattered. Due to the certain shear stress between the particles, this flow property has great limitations. The shear stress of the granular body is composed of friction and adsorption force, and the shear stress and the vertical pressure of the granular body are Just proportional. When the vertical pressure is zero, the shear stress is also called the initial shear stress (Ï„0), and the granule of Ï„0 is the good granularity of the fluid, also known as the ideal granular body. Powdery or flaked materials are bulky bodies with poor fluidity. In addition, the moisture, particle size and compaction of the material will affect its scattering.
The fluidity of the granules is usually expressed by its angle of repose (the angle of repose or the angle of accumulation). That is, the maximum inclination angle formed by the free surface of the granular body and the horizontal plane. The angle of repose of an ideal particle is equal to the angle of internal friction. It is independent of the way the tilt angle is formed. Granular grain usually uses its angle of repose to indicate its friction angle, and the granular body with poor fluidity has an angle of repose greater than the angle of internal friction.
2. Friction coefficient
The friction between the granular particles is called internal friction, and the magnitude of the internal friction is usually expressed by the internal friction angle. The tangent of the internal friction angle is the internal friction coefficient. The friction factor between the granular body and the surface of various solid materials is called the external friction factor. Correspondingly, there is an external friction angle, also called the self-flow angle, which is the minimum angle formed by the surface and the horizontal plane when the granular body slides down along the surface of the solid material.
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