The basic characteristics of raw materials and finished products can be used as raw materials for tens of thousands of feeds. 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. Most of them are granular, accounting for about 70%-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%-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.
I. Physical properties of materials 1. Scattered scatter is the ability of a reaction material to diffuse around in a free state. It is a property of material flow. Powdered and granular materials are roughly divided into:
5.0 cm or more is called a "block", and it is less than 10 Î¼m 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 particles of the granular body is called internal friction, and the magnitude of the internal friction force 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.
3. In the process of transporting, flowing and vibrating, the phenomenon of reclassification of the particles according to their respective characteristics during the transportation, flow and vibration process is called automatic grading. Generally speaking, large and light particles tend to float on the upper part of the pile or float to the edge, and small and heavy materials tend to accumulate in the lower part. When the transport distance is long and the vibration is large, the automatic grading is serious. Automatic grading is advantageous for raw material cleaning and grading, because the aggregation of impurities is easy to clean, and it is a reaction to the mixing of feed, which is the main factor affecting the mixing uniformity. Therefore, in the design of feed processing technology, the mixing should be minimized. Grading and taking such as granulation, adding liquid feed, reducing the transport section to ensure product quality.
4. Density density is the mass per unit volume when the granular body is naturally deposited. The volumetric mass of the granules is related to factors such as particle size, surface smoothness and moisture. Density is an important indicator when calculating storage capacity.
Second, the physical and chemical properties of materials 1. Adsorption Adsorption is the ability of a substance atom or molecule to adsorb another substance. For the feed industry, adsorption is the property of certain feedstocks to adsorb other substances onto their surface. Adsorption is one of the basis for selecting carriers and diluents for feed trace additives. In order to make the trace additive evenly mixed in the feed, it is necessary to first select a material with good adsorption as a carrier, mix it with a small amount of small component material, and then uniformly mix it into a large amount of feed to ensure the feed price. And safety, the adsorption capacity of the feed is often related to the shape of the material (granular, flake), surface properties (smooth, rough) and water content.
2. Hygroscopic hygroscopicity refers to the ability of feed ingredients to absorb and release moisture from the surrounding air. Some feed ingredients have strong hygroscopicity, such as salt, sulfate, choline chloride and fish meal with higher salt content.
The hygroscopic feed has poor stability, is prone to failure, mildew, agglomeration or automatic decomposition. In addition, in the compound feed, it also affects the storage and quality maintenance of other feeds.
3. Thermal stability Thermal stability refers to the ability of certain chemical components in feed to resist thermal damage under hot processing conditions. Vitamins in feed (such as VC, VA, etc.) and amino acids are easily oxidized and failed at high temperatures. The biological potency of certain minerals is also reduced under high temperature. In addition, certain harmful components in the raw materials, such as antitrypsin in soybean, mustard enzyme in rapeseed meal, and some harmful microorganisms and bacteria, may also be inactivated or killed under high temperature.
4. Chemical stability Chemical stability refers to the resistance of a feed bioactive substance to the destruction of damage under the action of foreign chemicals. Chemical stability is the main condition for the selection of vitamins, trace element salts and certain other additives such as antioxidants, mildew inhibitors and the like.
5. Toxicity Some feed ingredients, mainly trace mineral additives and some drugs contain heavy metals and other toxic components harmful to human body and carcass, such as copper sulfate, zinc sulfate, etc., which contain lead and arsenic harmful to humans and animals. , harmful heavy metals such as cadmium. Therefore, when using trace mineral additives, we must use products that meet the national quality standards. Another example is a very small amount of additives such as sodium sulfite which is necessary for the growth of animals, and which is excessively used and easily poisoned. Moreover, these substances have certain harmful effects on the environment and operators during processing. Excessive content or uneven mixing in the finished product may cause poisoning or death after being eaten by livestock and poultry.
6. Electrostatic static phenomena are usually associated with active ingredients. Dry and pulverized materials often carry an electrostatic charge, which causes adsorption to adsorb the active ingredient on the mixer or conveyor, resulting in uneven mixing. In order to overcome static electricity, premixed feed mills usually have grounding devices on the main equipment.
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