1 Purpose and Method of Feed Drying The purpose of feed drying is to remove excess moisture from feed ingredients for packaging, transportation, storage, processing, and use. Drying is a complex process. Different drying methods have different drying methods. Therefore, a reasonable drying method must be determined according to the different composition and characteristics of the feed. There are many classification methods of dryers, and they are classified according to the structure of dryers. The commonly used dryers include: spray dryers, fluidized bed dryers, air dryers, rotary drum dryers, drum dryers, infrared dryers, and high dryers. Frequency dryers. These dryers have been widely used in the feed drying industry and have greatly supported the development of the feed industry. Its structure and working principle are well known to us. This article will introduce several new drying methods and dryers so that everyone can understand the development direction and prospects of the dryer. 2 Emerging Dryers 2.1 Flash Dryer Helical Flash Dryer, which consists of a feeder, a drying chamber, a cyclone separator and a bag collector. The material to be dried is fed into the drying chamber by a feeder. The hot air enters the drying chamber in a tangential direction and flows upward from the bottom of the drying chamber in a high-speed rotation state. It is in full contact with the material and the material is in a stable equilibrium fluidized state. The agitator is in the drying chamber. Due to the combination of impact and high-speed swirling air flow, the mass of material is dispersed into irregular granules, and the larger undried material moves toward the wall of the chamber. Since it has a large settling velocity, it falls to the lower part of the drying chamber. process. As the material is dispersed and the materials collide with each other, the dried particles on the surface of the material block will move toward the axis of rotation of the gas in the drying chamber and be discharged together with the airflow to the material collector, resulting in uniform particle size and dryness. Dry product. The outstanding advantages of this dryer are high drying efficiency, low energy consumption, uniform product drying, compact structure, and melting and drying. Suitable for dry sticky, paste, powder, cake-like materials. In the feed industry, it can be used to dry blood meal, meat and bone meal, fish meal, protein ointment, dregs and so on. 2.2 Helical vibration dryer This machine consists of inner and outer cylinders, annular orifices, vibration sources and other components. The two vibrating motors are arranged in an intersecting manner. When the motor rotates, the vertical excitation force and the excitation force moment around the vertical axis are generated, so that the drying machine body performs the vertical vibration in the vertical direction and the torsion vibration around the vertical center line. The combination of two vibrations causes the material to make continuous jumping motions from the top to the bottom along the horizontal annular orifice plate. The drying medium is blown into the drying cylinder through the air inlet through the blower, passes through the layers of the orifice plate from bottom to top, and passes through the material layer. As the materials are continuously thrown and turned, both the material adheres to the spiral groove surface and the contact area of ​​the material with the drying medium is greatly increased, thereby strengthening the heat transfer and mass transfer process of the material and the drying medium. The advantages of spiral vibration dryer are energy saving, wide range of applicable materials, good quality of dried products, and high production efficiency. Suitable for drying all kinds of granular, powdery, blocky, sheet-like materials. In the feed industry, the dryer can be used to dry fish and shrimp bait, a variety of additives, distiller's grains, starch slag, vegetable protein and so on. 2.3 Rotary Dryer This machine belongs to the forward flow dryer. The material is fed into the rotary drum through the feeding device. The picking plate installed in the cylinder refers to the material and falls on the top. When the material falls, it is broken by the high-speed rotating blades in the cylinder, and thus reciprocates and moves to the outlet. At the same time, the hot air generated by the combustion furnace enters the cylinder and is in full contact with the material, so that the material is rapidly dried and then discharged through the conveyor at the discharge end. Because the dryer has a built-in crushing blade, the material entering the dryer can be immediately dispelled. In particular, a certain viscous material is broken into small pieces by a large mass and comes into contact with the hot air to bring out a part of the moisture. The full contact with the hot air to speed up the drying speed. The dryer is characterized by a large heat transfer coefficient, high thermal efficiency, small product oxidation, and a large amount of processing. It is suitable for drying all kinds of granular, small block, sheet-like high-humidity materials. In the feed industry, this machine can be used to dry chicken, pig manure, pasture, bad residue and so on. 3 Emerging Drying Methods 3.1 Vacuum Freeze Drying We know that the solid, liquid and gas states of water are determined by pressure and temperature. When the pressure drops to 610Pa and the temperature is 0.0098°C, the three states of water can coexist. This state point is Three-phase balance point. When the pressure is lower than 610 Pa, the liquid state of water cannot exist regardless of temperature changes. If the ice is heated at this time, the ice can only sublimate directly into the gaseous state over the liquid state. Similarly, the same result can be obtained if the temperature is kept constant and the pressure is reduced. Vacuum freeze-drying is based on the nature of water, the use of refrigeration
Equipment to freeze the material into a solid state, and then evacuated into a vacuum so that the solid ice directly sublimated into gaseous water vapor, so as to achieve the purpose of drying. The advantages of freeze-drying are many: the material under low pressure is not easy to oxidize and degenerate, and inhibit the vitality of some cells; the heat-sensitive components in the material remain at low temperature, and the original components in the material can be retained to the utmost; the skeleton is formed during pre-freezing, and can be maintained after drying. The original shape of the material forms a multi-microporous structure; the rehydration is good, and the water can be quickly recovered, and its quality is basically the same as before drying. The application range of freeze-drying is very extensive, but its cost is relatively high, so when choosing freeze-drying, we must consider the economic benefits, and we should not blindly adopt it. At present, vacuum freeze-drying technology is mainly used in food, medicine and feed additives. 3.2 Superheated steam drying Superheated steam drying technology is a new energy-saving drying method. It is a dry method of removing moisture by direct contact with wet materials using superheated steam. Compared with traditional hot air drying, superheated steam drying uses water vapor as the drying medium. The exhaust gas exhausted by the dryer is also all water vapor, so only one gaseous component exists in the drying process, so the mass transfer resistance is very small. At the same time, the temperature of the discharged exhaust gas is kept above 100° C., so it is easy to recover, and the latent heat of steam can be recovered by means of condensation, compression, and other methods, and the heat efficiency is high. In addition, since the heat capacity of water vapor is twice as large as that of air, the consumption of the drying medium is significantly reduced, so the unit energy consumption is low. The overheating and drying technology has many advantages: large heat transfer coefficient, low mass transfer resistance, low steam consumption, no risk of explosion and fire, environmental protection, sterilization and sterilization. However, the superheated steam drying also has a certain range of application, and the heat-sensitive material is not suitable for this drying method. If the recycling is unfavorable, the energy-saving effect will be greatly affected, and the cost thereof is also relatively high. In the feed industry, superheated steam drying technology can be applied to distillers grains, grasses, fish bones and fish.
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