Extruders are divided into single-screw extruders, twin-screw extruders, and triple-screw extruders. These three types of extruders can produce food and feed, as well as some special raw materials.
These three types of extruders are further divided into dry-process extruders and wet-process extruders. Dry-process extruders use friction and shear between the screw barrel and the screw to generate heat, supplemented by heating wrapped around the outside of the screw barrel. The external heat of the ring heats and extrudes the material, and the production method of puffing is more common in the small food industry. The puffed food produced is crispy and has a strong fragrance. In addition, small feed factories also use dry production, which has low investment costs and quick capital return.
The wet production extruder uses steam (generally the pressure is 0.3-0.4mpa and the temperature is 140-150°C) to preheat the material in the conditioner to 70-100°C, supplemented by the extruder’s own heat generation and screw barrel The production method of external heating (it can be steam water pipe or electric heating sheet) is commonly used in the production of aquatic feed, pet food, extruded corn feed, soybean feed, etc.
What is the difference between these three extruders, and what are their advantages?
1. The single-screw extruder consists of one screw to form the extruding chamber. Single-screw generally does not have external heating, and only in extremely cold regions or when soybeans are produced by the dry method, the external heating of the screw will be done. Therefore, in single-screw extrusion, the shear heat is guaranteed by the rotational speed, and the general single-screw rotational speed is 480-600 rpm. It is suitable for puffing grains with a single shape and not a spherical shape, for ripening, and the price is cheap.
2. The twin-screw extruder is composed of two screws in the puffing chamber, and the two screws are combined to form a set of meshing areas. While the materials are running in parallel in the puffing chamber, the effect of mixing and shearing is increased, so it is more efficient than single-screw. It is suitable for the production of mixed formula feed. Its advantages are: 1. Low speed, generally 200-300 rpm; 2. The two screws increase mutual shear, so the material has a high degree of homogenization and stable quality; 3. Make full use of the external heating and curing of the screw barrel 4. Using frequency conversion speed regulation, the operation is stable and reliable; 5. The screw has a self-cleaning function, and there is no need to disassemble the screw barrel for cleaning after stopping.
3. The three-screw extruder is composed of three screws in the puffing chamber, and the three screws shear each other, which is equivalent to three sets of twin screws operating simultaneously in one puffing chamber, with three meshing points, so the shearing efficiency is high and the material is easy to plasticize, At the same time, the pressure generated before puffing is greater, the degree of ripening is better, and the amount of nutrients such as protein and fresh meat is more added. Energy consumption is 30% lower than that of twin-screw extruders with the same output.
