The production process in the production of shrimp feed
The crushing of shrimp feed raw materials is a basic processing technology, and the crushing particle size should be above 40-60 mesh. Considering the processing energy consumption, the energy consumption of the hammer mill when it reaches 100 mesh is more than 3 times higher than that of 40 mesh. Therefore, the fineness of the raw material is not less than 40 meshes, but the finer the grinding fineness, the better the water resistance of the extruded particles. In addition, it can improve the mixing uniformity of the compound feed, improve the pressing quality of the pellet feed, and facilitate the contact between the digestive enzymes and the feed, and promote digestion.
The crushing of raw materials requires two processes. The first process is coarse crushing, such as peanut cakes and shrimp head shells, which require a 400-type hammer-type bean cake crusher, equipped with a sieve with a sieve hole of 3 mm, to crush the raw materials into coarse powder; The second step is fine grinding, which can be used with a superfine pulverizer or a 50-type hammer pulverizer. The latter should be equipped with a sieve with a sieve hole of 0.5 mm. The crushing must meet the requirements of all passing 40 meshes and 80% passing 60 meshes.
Raw materials must be cleaned before crushing, such as hammers, paper scraps, wood, stones and other debris. Mix the ingredients such as peanut cake powder, fish meal, blood globulin powder, squid powder, etc. according to the formula ratio before the second pulverization. Pulverize it into powder of more than 40 mesh, then add standard flour, additives, etc. for stirring to make it evenly mixed, and the coefficient of variation is not more than 10%.
Quenching and tempering process
The moisture content of the pulverized raw materials is generally about 13%. The material is not easy to soften and gelatinize during granulation, which has an impact on the granulation and water resistance. Therefore, appropriate moisture addition is another important condition for powder bonding and starch gelatinization. First, when stirring, spray water with a high-pressure water pump for a few minutes to achieve a powder moisture content of about 18%; secondly, add steam. In this way, the moisture content is uniform, and the material meets the softening requirements. After the steam is added, the temperature of the material increases rapidly, prolonging the gelatinization time of the material, the starch is fully gelatinized, the working temperature of the die is correspondingly reduced, and the service life of the die is improved. The processing effect is good, and the steam pressure should be controlled between 4-15 kg/cm 2 and kept stable. The produced feed is dark brown with a smooth surface. The particles have the same length, delicious taste and strong appetite. After steam treatment, the temperature is below 80°C. The particles are yellowish-white, with a lot of powder, poor water resistance, and shrimp anorexia, because the feed is not effectively gelatinized and cooked. Like a plywood. When the discharge temperature exceeds 105°C, the granulation becomes black and the adhesion is good, but the nutrients are greatly damaged, and the shrimp are anorexia and difficult to digest. The amount of moisture added should make the moisture content of the material around 17%-18%. Generally, after adding and tempering with steam, take the material from the reclaiming hole of the main machine, hold it into a ball, and vibrate a little, and it can be cracked. When the moisture is too low, the gelatinization speed is slow, the granulation current is large, the particles are irregular, and the output is reduced; The steam addition in actual operation is limited to the fact that the pellet machine does not slip and block the die hole.
The conditioner of the shrimp feed host is different from that of livestock feed, and should be increased and lengthened. Usually two conditioners are used, which can make the steam penetrate the material evenly and achieve the purpose of starch softening and gelatinization. The main ring die has been used for a long time, the inner diameter is worn, and the bell mouth is deformed, which affects the normal granulation or blocks the die hole. The lower ring die should be disassembled, the powder of the die hole should be punched out, and the inner wall of the hole should be smoothed by immersion in oil; if the inner wall of the ring die is seriously worn, the inner wall should be polished and the bell mouth should be reprocessed. Imported machinery is best to use the original ring die. The diameter of shrimp feed pellets is preferably 2-25 cm. The juvenile shrimp material is crushed and processed into micro-particles of 0.3-0.6 mm.
After the main machine extrudes the pellets, the moisture content is high, and it needs to be dried. It can be dried by electric heating or steam. Its function is to reduce the moisture content of the pellets, which is usually below 10%, and the feed will not deteriorate for more than 2 months; the second is to promote re-gelatinization, which plays the role of post-cooking and increasing the cohesion of the pellets.
The temperature of the electric heating dryer is generally required to be 90 ℃, and the passage time of the pellets is about 20 minutes. If it exceeds 90 °C or the drying time is too long, the pellets may be burnt, and the vitamins will be damaged, which will affect the preference of shrimp and the full value of the feed. The temperature of steam drying can be relatively increased to 105 ℃.
Cooling and cooling process
The cooling of the pellets is usually carried out in a cooling tower, using an exhaust fan to suck in a large amount of cold air to take away the heat and part of the moisture of the pellets in the tower.
If the pellets directly enter the cooling tower without being processed by the dryer, the surface of the pellets will be rapidly cooled and dehydrated inside, and a large number of fine cracks will appear on the surface and expand to the deep. Phenomenon. When feeding, soaked in water, it will decompose into several clumps along the cracks, which will make the water resistance worse. If it is dried, the above phenomenon will be much less.
The moisture content of pellets is 17%-18% when they leave the granulator, 12%-13% after drying, and 10%-11% after cooling.
Grading screen process
The semi-finished products after the powder is granulated by a granulator, heated and cooled by a dryer, including granules, powder and slag, must be sieved by a grading sieve, and the powder and broken particles are filtered out from the bottom layer, and the overlong particles and slag are removed from the upper layer. The slag is screened out, and the finished material flows from the middle layer to the feed tower for packaging. Shrimp feed series are divided into young, small, medium and adult shrimp feeds, with different nutritional components and different requirements for particle size. Young shrimp need 0.3-1.5 mm of shrimp seed material, medium shrimp requires 2 mm, and adult shrimp is 2.7 mm. The particle length requirements are also different. With the growth and development of shrimp, the particle length increases from broken particles to several millimeters. The middle layer of the grading screen should also be replaced with the replacement, and the pellets should be neat, pure and beautiful. The prawn seedlings should also be crushed, graded and packaged once or twice.