The main differences between the forming principles of extrusion puffing and ring die granulation are as follows:
Principle of extrusion puffing:
1. Containing a certain amount of starch Powdered raw materials, such as corn, soybeans, etc., are tempered to make the material moisture reach 10-27% and the temperature rises to 70-98°C.
2. The quenched and tempered material enters the screw extrusion chamber. Since the volume of the extrusion chamber gradually becomes smaller along the axis, the pressure on the material gradually increases, and the compression ratio can reach 4 to 10.
3. The material is extruded and pushed by the screw, accompanied by strong shear and friction. If necessary, the material can be heated by the steam flowing through the barrel jacket to keep the material in a Under high temperature and high pressure, the starch in the material gelatinizes.
4. When the material is extruded out of the die hole by great pressure, due to suddenly leaving the body and entering the atmosphere, the temperature and pressure drop sharply. Under the combined action of the pressure difference and temperature difference, the feed volume decreases. It expands rapidly, the water evaporates quickly, dehydrates and solidifies, and then is cut into short particles by a cutter to form puffed pellet feed.
Principles of ring die granulation:
1. The die is a porous cylindrical tube that rotates due to transmission. There are 2-4 grooved freely rotating or Driven self-rotating roller (pressure roller).
2. The raw materials enter the steel mold, are pressed into the working area by the rotating rollers, are embedded in the die holes, are extruded from the outer wall of the steel mold, and are cut into cylindrical particles by the cutter.
3. Working principle of flat die pellet machine: Its main components are a flat circular steel die and a set (2-4) of grooved free-rotating rollers. The raw material falls into the gap between the rollers from top to bottom, is pressed into the die hole by the rotating roller, and a long cylindrical object is extruded from the bottom of the die hole, and is cut into granules by the cutter.