The twin-screw extruder has wider raw material adaptability, wider product adaptability, better internal and external quality of the product, higher output under the same power, better ripening and homogenization effect, easier process operation, and wear of consumable parts. The many advantages of being lighter and lower in production costs give feed processing companies more reasons to choose twin-screw extruders when building or expanding special feed production lines such as aquatic feed and pet food.
Single-screw extruders have a simple structure and usually use belt transmission. The main shaft speed is constant and cannot be adjusted. Its transmission efficiency is low and process control is difficult. The screw of the single-screw extruder consists of a shaft connecting screw units of various structures. The entire screw consists of 3 sections: feeding section, kneading section or melting section and forming section. After the material enters the barrel from the feeding port, it undergoes solid transportation and melting processes in the screw, transforming the material from a loose state into a continuously plastic dough shape. The twin-screw extruder is developed on the basis of the single-screw extruder. In the barrel of the twin-screw extruder, two screws are placed side by side. According to the relative position of the screws and the direction of the screw, they are divided into different types. Engaged co-rotation, non-engaged relative rotation, engaged co-rotation, engaged relative rotation. The fully meshed co-rotating twin-screw extruder greatly improves the material conveying, pumping and mixing characteristics.
Advantages of the twin-screw extruder: (1) The raw materials have wider adaptability and can be adapted to high viscosity, low viscosity, high grease content, high moisture or viscosity, oily, very wet and other materials that are processed in a single screw (S S E ) will slip in the processing of raw materials. (2) There are fewer restrictions on the particle size of raw materials, and it can be adapted to the processing of raw materials with very wide particle sizes or from micro powder to coarse powder particles and single-screw processing of raw materials with particle sizes outside the specific range. (3) The material flow is more uniform in the barrel, and the proportion of steam, water and other auxiliary processing can be added more accurately and the actual required effect can be achieved. (4) The internal and external quality of the product is better. It can achieve a very good homogeneous state and make the molecular structure of the material evenly arranged. The surface is smooth during the extrusion and molding process, and the product particles have high uniformity and good uniformity. (5) The ripening and homogenizing effect is better. Usually the starch ripening degree can reach more than 95%, so that the processed aquatic feed can remain stable in the water and the product nutrients are not lost and are easy to digest and absorb. (6) The output is higher under the same power. The good mixing performance homogenizes the heat obtained from the material in time, accelerates the maturation of the material, reduces the fluctuation of material temperature, and increases the output of extruded and puffed products. (7) Product diversity and adaptability are wider, and it can process particulate aquatic feed, high-oil formula, high-moisture, high-adhesion products and multi-color, sandwich, and special-shaped products. (8) The process operation is easier, and the spindle speed can be adjusted according to the needs of the processed products. Due to the self-cleaning feature, cleaning is very convenient, and there is no need to disassemble and assemble the equipment after each processing. (9) Consumable parts wear less. It is usually a misconception that a single screw has less wear. In fact, during the twin-screw extrusion process, due to the characteristics of stable material transportation and material flow, the impact of the material on the screw and barrel is determined. The wear of the inner sleeve is less than that of a single screw. Although there is one more set than the number of screws, the cost of accessories is still lower than that of a single screw. (10) The production cost is lower. Since the twin-screw model has good operational stability, it requires less start-up materials, less water and gas waste, less man-hours, high heat transfer efficiency, high yield, and low electricity consumption during feed processing. The output index is high, and the cost of accessories is also low. Its production cost is still much lower than that of a single screw. (Document source: Wang Mu, New Feed, 2007, (1): 37-41. Anonymous editor)
