1 Purpose and method of feed drying

The purpose of drying the feed is to remove excess water from the feed ingredients for packaging, transportation, storage, processing and use. Drying is a complex process. Different drying objects have different drying methods, so it is necessary to determine a reasonable drying method according to the different composition and characteristics of the feed. There are many classification methods for dryers, which are classified according to the structure of the dryer. The commonly used dryers are: spray dryer, fluidized bed dryer, airflow dryer, rotary cylinder dryer, drum dryer, infrared dryer, high Frequency dryer, etc. These dryers have been widely used in the feed drying industry, which greatly supports the development of the feed industry, and its structure and working principle are well known. This article will introduce several emerging drying methods and dryers to help you understand the direction and prospects of dryers.

2 emerging dryer
2.1 Flash dryer
The spiral flash dryer is mainly composed of a feeder, a drying chamber, a cyclone separator and a bag collector. The material to be dried enters the drying chamber from the feeder, the hot air enters the drying chamber along the tangential direction, and flows upward from the bottom of the drying chamber at a high speed rotation state, and is in full contact with the material, so that the material is in a stable equilibrium fluidized state, and the agitator in the drying chamber Under the combined action of the impact and high-speed rotating airflow, the material block is dispersed into irregular granular shape, and the larger undried material moves toward the chamber wall, and the lower part of the drying chamber is repeated due to its large sedimentation speed. process. As the material is dispersed and the materials collide with each other, the dried particles on the surface of the block will be moved to the axis of rotation of the drying chamber gas, and discharged together with the gas stream to the material collector, thereby obtaining a uniform particle size and dryness. Dry the product. The outstanding advantages of this dryer are high drying efficiency, low energy consumption, uniform product drying, compact structure, and fusion of pulverization and drying. Suitable for dry viscous, paste, powder, filter cake materials. In the feed industry, it can be used to dry blood meal, meat and bone meal, fish meal, protein paste, dregs, etc.

2.2 spiral vibration dryer
The machine consists of inner and outer cylinders, annular orifice plates, vibration sources and so on. The two vibration motors are arranged in a cross arrangement. When the motor rotates, the excitation force in the vertical direction and the excitation force moment around the vertical axis are generated, so that the drying body is subjected to linear vibration in the vertical direction and torsional vibration around the vertical center line. The combination of the two vibrations causes the material to continuously jump from top to bottom along the horizontal annular orifice. The drying medium is blown into the drying cylinder by the air blower through the air inlet, and passes through the layers of the holes from bottom to top and passes through the material layer. As the material is continuously thrown and turned over, the material can be prevented from sticking to the surface of the spiral groove and the contact area between the material and the drying medium is greatly increased, thereby enhancing the heat transfer and mass transfer process of the material and the drying medium. The advantages of the spiral vibration dryer are energy saving, wide range of applicable materials, good quality of dry products and high production efficiency. It is suitable for drying all kinds of granular, powdery, blocky and flake materials. In the feed industry, the dryer can be used to dry fish and shrimp bait, various additives, vinasse, starch residue, vegetable protein and the like.

2.3 rotary vane dryer
The rotary vane dryer is a downstream dryer. The material is put into the rotary drum through the feeding device, and the lifting plate installed in the cylinder drops the material to the top, and the material is broken by the high-speed rotating blade in the cylinder when it falls, so that it 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 quickly dried and then discharged through the conveyor at the discharge end. Since the dryer has built-in broken blades, the materials entering the dryer can be immediately broken up, especially the materials with certain viscosity are broken into small pieces by large clumps, and contact with hot air to bring out a part of the water, so that It is in full contact with hot air to speed up drying. The dryer is characterized by a large heat transfer coefficient, high thermal efficiency, small oxidative degradation of the product, and large processing capacity. It is suitable for drying all kinds of granular, small block and sheet high humidity materials. In the feed industry, the machine can be used to dry chicken, pig manure, pasture, dregs, and the like.

3 emerging drying methods
3.1 Vacuum freeze drying
We know that the three states of solid, liquid and gas are determined by pressure and temperature. When the pressure drops to 610 Pa and the temperature is at 0.0098 °C, the three states of water can coexist. This state point is the three-phase equilibrium point. When the pressure is lower than 610 Pa, the liquid liquid cannot exist regardless of the temperature change. At this time, if the ice is heated, the ice can only be sublimated into a gaseous state over the liquid state. Similarly, if the pressure is kept constant while maintaining the temperature, the same result will be obtained. Vacuum freeze-drying is based on the nature of water. The refrigeration equipment is used to freeze the material into a solid state, and then vacuumed to make the solid ice directly sublimate into gaseous water vapor to achieve the purpose of drying. The advantages of freeze-drying are many: the material is not easy to oxidize and deteriorate under low pressure, and the activity of some cells is inhibited; the heat-sensitive component in the material is retained at low temperature, and the original component in the material can be retained to the maximum extent; the skeleton is formed during pre-freezing, and can be maintained after drying. The original shape of the material forms a microporous structure; the rehydration is good, and it can be quickly recovered by water absorption, and its quality is basically the same as before drying. The application range of freeze-drying is very wide, but its cost is relatively high. Therefore, economic benefits must be considered when choosing freeze-drying, and it should not be blindly adopted. 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 an emerging energy-saving drying method. It is a drying method that uses superheated steam to directly contact wet materials to remove moisture. Compared with traditional hot air drying, superheated steam drying uses water vapor as the drying medium, and the exhaust gas removed by the dryer is also water vapor. Therefore, only one gaseous component exists in the drying process, so the mass transfer resistance is very small. At the same time, the exhaust gas temperature is kept above 100 ° C, so the recovery is relatively easy, and the latent heat of the steam can be recovered by condensation, compression, etc., and then utilized, thereby having high thermal efficiency. In addition, since the heat capacity of water vapor is twice as large as that of air, the consumption of drying medium is significantly reduced, so the unit energy consumption is low. The superheat 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 disinfection. However, superheated steam drying also has a certain range of application. For heat sensitive materials, this drying method is not suitable. If the recovery is unfavorable, the energy saving effect will be greatly affected, and the cost is relatively high. In the feed industry, superheated steam drying technology can be applied to distiller's grains, pasture, fish bones and fish.