After the mixed powdery feed is granulated, the nutrition and food quality of the feed can be improved and improved to varying degrees. Granulation is not only suitable for livestock and poultry feed, but also suitable for aquatic products and special feeds. Due to the different varieties and components of the feed ingredients, the scale of the finished products is different, and the performance and structural parameters of the granulation equipment also have different requirements. The granulation process is generally equipped with equipment such as granulation, cooling, granulation and grading, and some are equipped with a grease painting system. The selection criteria for the above several devices are as follows:
The granulator used in the feed mill has two types of ring molds and flat molds. The flat die is more suitable for granulation of roughage, so only the ring die granulator is described. Since the working principle of the ring die granulator is basically the same, the performance evaluation of the ring granulator mainly depends on the rationality of the structural design, the ease of operation, the selection of structural parameters, the processing means, the manufacturing level, the selection of parts, and the purchase channels. Control functions and other aspects to consider.
Cooling is to maintain good storage performance after granulation, and is an indispensable procedure after granulation. For a long time, the cooling after granulation uses cross-flow cooling. Although it can meet the requirements of use, the temperature of the cooling particles is less than 7oC, but it is easy to reach the standard if it is inadvertently operated. Therefore, the recent emergence of counterflow coolers is a more reasonable cooling principle, because the convection heat exchange system is the most complete and reasonable. The machine was quickly promoted as soon as it appeared. The cooling effect of the machine can be lower than room temperature 3oC, and the cooling effect is extremely ideal. The selection of this machine, because the models produced by each factory are similar, so pay attention to the quality of manufacturing, materials and accessories, such as: the automatic control effect of the inlet and outlet linkage mechanism, whether the main part is made of stainless steel. In addition, the output selection can be used not only for large-size models, but also for stacking two machines to increase production, and the selection and use of fans and separators is very effective. The suction pipe should be made of stainless steel sheet, otherwise the service life of the water vapor will be greatly affected, so it should be paid attention to, otherwise it is impossible to obtain the most ideal use effect.
The granules can save power consumption and increase the digestion and absorption rate of livestock and poultry. At present, almost all of the granulators use roll-type granules, and their performance is mainly evaluated by the structural rationality, structural parameters, process parameters and processing level of the machine. The roller has a large pressure and is easily crushed. There are two types of pressure roller profiles, one is crossed helical teeth, and the front is suitable for the front, the number of teeth should not be too much, which reduces the powder extraction rate; the second type is the combination of straight teeth and helical teeth, this combination The rate of disposal is also small, but both types of tooth arrangements can meet the requirements of use, and the powder extraction rate should be controlled within 3%. However, from the actual use, it is very important to adjust the distance between the two rollers. Otherwise, the work will be carried out under the condition that the distance between the two rollers is not uniform. The product is uneven, and a meter can be provided at the adjusting hand wheel for operation. In addition, you must pay attention to the inlet size of the crusher when selecting the model, which should be completely consistent with the cooler outlet, otherwise the powder extraction rate will be increased.
4, grading sieve
After the granules are grading, the powder fraction is removed to ensure that the material has pure small particles, so that the feeding effect is optimized. The existing grading screen mainly has a vibrating grading screen and a rotary vibrating screen, both of which can achieve better results. The vibrating sieving screen should adjust the amplitude of the screen according to the nature and flow of the material to achieve the best results. Due to the long distance of the screen surface, the rotary vibrating screen has a good classification effect and is also one of the commonly used equipment. In short, both types of models can meet the requirements of use, and the classification efficiency can reach 98% to 99%.
The aging is to improve the gelatinization degree of the feed, to improve the water-resistance of the pellet feed, and to improve the granulation performance and the eating quality. The curing process is still in its infancy. At present, the post-curing process selects the curing stabilizer with steam adding system and jacket insulation device to keep the material temperature at 80oC～90oC, and the particles can be kept in the machine for 20-40min (adjustable), so that the starch paste in the granules It can be made into a network structure, which can meet the requirements of water resistance of more than 6min.
6, extrusion (expansion), extruder
The working principle of the extrusion expander and the extruder is very similar, mainly due to the large difference between the structural parameters and the process parameters, such as the screw compression ratio of 1.05 to 1.2:1, the stability of the extrusion chamber is 120oC to 130oC, and the working pressure in the extrusion chamber is 9.8 x 10-5 to 4.9 x 10-6 Pa. The destruction rate of harmful factors is 80% to 90%, and the degree of gelatinization of starch is 85% to 90%. In addition, whether the material of the screw-threaded sleeve is alloy steel, whether the processing method is reasonable and advanced, and the performance after heat treatment, these parameters have a direct relationship with the use effect, and cannot be ignored, must be understood.