How to choose aquaculture fish feed extruder

When choosing aquafeed production equipment, you must first understand the many characteristics of aquafeed:

1. Small particle size. Due to the short digestive tract and related physiological characteristics of aquatic animals, in order to speed up digestion and absorption, the crushed particle size of aquatic feed should be smaller than that of livestock and poultry feed. For example, in the production of eel and shrimp feed, the particle size should reach 80 to 120 mesh.

2. High protein content and low carbohydrate content. The protein content of livestock and poultry feeds is generally less than 20%, while the protein content of aquatic animal feeds is mostly 30% to 40%, and the protein content of turtle and eel feeds is as high as 65% to 70%.

3. The pellet feed has a compact structure, high cohesion and water resistance, and the shrimp feed requires the pellet feed to be stable in water for more than 2 hours.

4. In the production of aquatic feed, cross-contamination is strictly prohibited. Some raw materials need to be treated aseptically. The selected equipment is easy to clean and has less residue. Especially when producing shrimp and eel feed, other types of feed should not be produced at the same time to prevent cross-contamination. .

To produce high-quality aquatic feed, we must rely on scientific and reasonable processing technology and combine it with advanced, reliable and stable processing machinery. In this regard, the choice of processing equipment is particularly critical.

Selection of crushing equipment

 Generally, when producing ordinary fish feed, the particle size of the raw materials is required to be about 40 mesh to 60 mesh, but when producing special aquatic pellet feed (shrimp feed, eel feed, turtle feed, etc.), the particle size of the raw materials must be more than 80 mesh. The crushing particle size of the raw material determines the surface area of the feed composition. The finer the particle size, the larger the surface area. The ability to absorb water in the steam before granulation is strong, which is conducive to conditioning and particle forming, so that the pellets have good water stability. The residence time in the body of the product is good, and the absorption effect is good, which can improve the feeding return and reduce water pollution. In order to achieve the ideal crushing particle size, the previously commonly used hammer mill is no longer suitable for the production of fish feed. At present, the popular "drop-type" pulverizer at home and abroad is an advanced pulverizer model introduced by developed countries in Europe and the United States in the 1990s. This machine fully exploits the advantages of horizontal pulverizers, and uses unique design ideas. The pulverizer can form two kinds of hammer-screen gaps, which are used for ordinary pulverization and fine pulverization respectively. The pulverization particle size is more uniform, and the fine pulverization particle size meets the production requirements of ordinary fish feed.

01 Secondary crushing system

The micro-grinding of aquatic feed often adopts the secondary grinding process, that is, the first coarse grinding and then the micro-grinding, of which the second micro-grinding is used. This process covers a large area, and the size of the crushing size is achieved by replacing the sieve plates with different apertures and adjusting the air volume of the system, and it is easy to cause the temperature of the crushed material to rise sharply, the nutrients are destroyed, and the phenomenon of screen blocking often occurs, resulting in equipment wear and energy waste. If a sieveless pulverizer is used, the influence of the sieve plate can be eliminated, and the fine pulverizer with its own classifier can save the processing of returning materials. The material temperature is low, the power consumption is low, and the output is high. A separate micro-classifier is available.

The vertical shaft micro-grinder is a micro-grinding equipment that integrates grinding, screening and separation, and can meet the grinding particle size requirements of special aquatic feeds. Since the crushing chamber and the grading chamber are located in the same body, the equipment can simultaneously complete the processes of crushing, air screening, separation and re-crushing, which can effectively prevent over crushing. Built-in high-precision micron-level wind classification, the crushed particles can reach 60 meshes to 200 meshes, and can be adjusted arbitrarily. The temperature rise of the crushed material is low, especially for heat-sensitive materials. The whole process has a compact structure, small footprint, low power consumption per ton of material, uniform product particle size and high output. It is an ideal micro-grinding equipment for the production of special aquatic feed.

Ultrafine grinding unit

02 Selection of mixing equipment

The mixer is one of the key equipment of the feed factory, and the batching mixing system is an important section of the whole feed factory. The performance of the mixer and the effect of its use directly affect the production efficiency and product quality of the feed factory. The mixers used in general feed mills are still dominated by conventional leaf-belt horizontal screw mixers. This mixer has a long mixing cycle and the mixing uniformity is not suitable for the production of aquatic feed. In recent years, with the rapid development of high-performance computers, batching scales, and electronic technology, its performance is better than that of ordinary computer batching scales, and the batching accuracy is high, especially the batching cycle has been gradually shortened to about 2 minutes. Therefore, an ideal mixer should be selected in the batching mixing section. The production cycle of the mixer should be equal or similar to that of the batching scale, so as to ensure that the batching mixing system has an accurate ratio, high mixing quality and can operate normally, so that the production rate of this section can reach The best state, so as to effectively ensure the mixing effect, improve the output and reduce the cost. From this point of view, the currently used leaf-belt horizontal screw mixer can no longer be used in conjunction with more and more advanced computerized batching scales, which obviously hinders the improvement of productivity in this important link of ingredient mixing in feed mills.

To sum up, it is best to use a horizontal biaxial paddle mixer for the production of aquatic feed. This biaxial paddle high-efficiency mixer uses a new mixing mechanism and can achieve the required mixing uniformity. The machine utilizes the principle of instantaneous weight loss, so that the material is subjected to mechanical action in the body to produce an all-round composite cycle, which is widely interlaced without dead ends, so as to achieve uniform diffusion and mixing. The entire mixing process is mild, without segregation, and will not destroy the original physical state of the material . The mixing uniformity is high, the optimal mixing time is 30 seconds to 120 seconds, and the variable range of the filling amount is large. The discharge adopts the bottom discharge and large door structure, and the discharge is rapid and no residue; the discharge door is sealed reliably and there is no leakage; the discharge control can be electric or pneumatic as required. The machine is equipped with a liquid adding tube, which can add oil and other liquids, mainly adding soybean oil, rapeseed oil and fish oil. (2) Enhance the protection of water-soluble vitamins. The amount of oil added can be determined according to the species of aquatic animals and feed materials.

Selection of twin-screw extruder

Feed extrusion technology is mainly used in the production of special aquatic feed, pet feed and other animal feed. In addition to the advantages of general full-price pellet feed, extruded feed can improve the digestion and absorption rate of feeding animals, and can effectively prevent animal digestive tract diseases. Extruded feed is not only suitable for materials with high starch and fat content because of the gelatinization and gelatinization effect of starch, but also because of the high temperature and high pressure curing effect, the disinfection and sterilization effects are more obvious, and the applicability is strong. . It is precisely because of the advantages of puffing that more and more feed mills have begun to puff aquafeed. The main working principle of the extruder used is that the powdery material containing a certain amount of starch (more than 20%) is conditioned and tempered by a conditioner, so that the moisture content of the material can reach 25% to 27%, and the temperature is raised to 80℃～ 100°C. The extruder consists of a feeding system, a transmission system, an extrusion system, a discharging die and an electrical control system. The quenched and tempered material enters the screw extrusion zone. Since the volume of the extrusion zone gradually decreases along the axis, the pressure on the material gradually increases, and the compression ratio can reach 4 to 10. The material is pushed by the screw extrusion, and accompanied by strong shear and friction, the pressure and temperature rise sharply. Under the action of high temperature and high pressure, the starch in the material can be basically completely gelatinized, and the protein is partially deformed. When the material is squeezed out of the die hole by a great pressure, the temperature and pressure drop sharply due to the sudden departure from the machine body and into the atmosphere. Under the combined action of the pressure difference and temperature difference, the volume of the feed expands rapidly, and the material flashes, that is, the water evaporates rapidly. , dehydration and solidification, and then through the customized discharge mold to achieve various shapes and structures required, the extruded pellet feed is made.