The flat die granulator is a granulator that uses a horizontal disc pressure roller and its matching pressure roller as the main multi-working component (granulator), also known as a vertical axis flat mold granulator (Figure 5-9). Compared with the ring mold granulator, there are many similarities in trench formation, working principle and process. For example, the structure of the feeder and conditioner is basically the same, and the extrusion raw material is also used. The differences between them are mainly manifested in the following points:
1. The radial linear speed of the die roll: the contact point of the ring die roll and the inner diameter of the die are on the same circumference, so the linear velocity is the same; while the flat die pressing roller rotates around the center of a flat circular template, the radial die contact points The linear speed (ie, the axial direction of the pressure roller) is different, which will affect the uniformity of the finished product and cause uneven wear on various parts of the mold and the roller. Therefore, the circumferential speed of the flat die and the ring die is different: the flat touch is generally 2~5m/s, and the ring die is 4~8m/s.
2. The number of rollers and their diameter: the ring film is limited by the inner diameter of the ring die, and the inner cavity of the flat die is less restricted, so the flat die can appropriately increase the number of rollers and its diameter. The number of pressing rollers of the flat die granulator is generally 2~5, and 4 are common; while the ring die is generally 2~3, with 2 being the best, because 2 can provide more space for materials than 3 . For the ring die of two pressure rollers, the ratio of the diameter of the roller die is 0.4~0.47.
3. Grab angle (clamp angle) and power consumption: due to the different internal cavity structure of the flat die and ring die (the ring die pressing particle chamber is a cylindrical groove, the flat die pressing particle chamber is controlled by the housing cover), under the condition of the same material layer, The grab angle of the ring die is larger than that of the flat die, that is, the ring die extrusion time is longer, the density of the extruded particles is larger, the ring die consumes more power during the extrusion process, and the quality of the extruded particles is better. According to calculations, to make the two compacted layers the same, the diameter of the flat die roller should be 1.6 times the ring die.
4. Transmission mode: the ring die is active, and the pressure roller is follow-up. Flat die action roller type, dynamic mode, as well as both moving mold and moving roller, currently the main die is fixed and moving roller, so the structure is simple, and the die is replaced quickly.
5. Others: flat die structure is simple, easy to manufacture, low cost, and suitable for pressing fibrous materials. Except for a few imported large flat dies in my country, they are mostly small flat dies; large and medium-sized feed mills often use ring dies.