The fineness of the raw material before puffing is not only related to the crushing equipment, but also needs to involve the screening equipment, that is, the fineness of the final raw material is guaranteed by the crushing equipment and the screening equipment.
First of all, the selection and control of crushing equipment is the key to the whole process design. The crushing fineness of raw materials is required to reach 80 meshes. At present, a vertical ultrafine pulverizer is generally selected, but the current hammer mill cannot meet the requirements. Moreover, the raw material is required to reach such a fineness, and there is also a strict control requirement for the ultrafine pulverizer used.
Secondly, we must pay attention to the requirements and control of screening equipment. After the material is crushed, there will be a small amount of large particles mixed in it, and there will be some impurities in the whole process. In addition, during the crushing process, due to the relatively small bulk density of the fibers in the material, there are also some fibers that are not well crushed. of crushing. Some of these impurities and fibers are "melted" during the extrusion process of the puffing machine, but some of them will block the die hole before reaching the die hole. Even if some fibers pass through the die hole, some of them will hang on the cutter, thus affecting the cutting The cutting of the puffed product by the knife will reduce the aesthetics of the puffed particles.
Therefore, it is necessary to set up a good screening equipment in the process before the puffing section. At present, it is a good practice to configure a square sieve after the crushing equipment, and to sieve the material through the high side sieve once before it reaches the puffing bin, so as to prevent impurities in the process from being mixed into the material.
Requirements for raw material formula
For starch-containing raw materials in the formula, it is better to use flour. The experiment used different starch-containing raw materials to process small particles with a mold size of 1.0 mm. Under the condition that other raw materials remain unchanged, the formula of starch-containing raw materials is to add 26% corn, wheat and flour respectively. Such different formulations are produced by single-screw extruders. Under the premise of consistent processing parameters, the effects of using wheat, corn and flour as starch raw materials on puffing are obtained. It is found that the floating rate of these three is that corn is not as good as wheat, and wheat is not as good as flour. The floating rate of flour can reach more than 98%, while that of corn is only about 80%. At the same time, it was found that when the corn was used as the raw material of the starch formula, more fibers were pasted on the blade, resulting in uneven incisions and easy roughening of the particle surface.
Requirements for fineness of raw materials before puffing
The processing of small particle extruded aquatic feed has extremely strict requirements on the crushing fineness of raw materials. Theoretically speaking, when the crushing fineness of raw materials reaches 100% and passes through a 60-mesh sieve, normal production can be guaranteed with an extruder with a die hole of 1.0mm. But practice has proved that when such a crushing fineness is produced, after the extruder runs for a period of time, the die holes will start to block, the expansion coefficient of the particles will gradually increase, and the expanded particles will become longer at the same time. When more die holes are blocked and the speed of the cutter reaches the limit and the length of the puffed particles cannot meet the requirement, the final choice is to stop the machine and clean the die.
In addition, special attention should be paid to the fact that when producing small particle extruded feed, if the formula contains cashmere, wool, leather, cotton materials and other special fiber materials that are difficult to meet the crushing requirements, it will bring a lot of unnecessary troubles to the production. , and even cannot be produced normally. Although these plush and fiber raw materials have been screened, even if they can be sieved, it is inevitable that there will still be plush and fiber aggregation that will cause mold blockage or stick to the cutter, affecting normal production.
Therefore, in order to be able to produce stably for a long time, it is recommended that the formula should not contain cashmere, fur, leather, cotton materials and other special fiber materials that are difficult to meet the crushing requirements, and the crushing fineness of the raw materials should reach 100% and pass through an 80 mesh sieve. Well, the minimum must reach 98% and the maximum particle size of the sieve shall not exceed 0.3mm. The fineness of the raw materials can ensure the stable production of the extruder for a long time. At the same time, the appearance of the puffed particles is relatively smooth and beautiful due to the finer crushing of the raw materials.
