There are many granulation methods, which can be divided into: rolling granulation, fluid bed granulation, stirring granulation, compression granulation, extrusion granulation, melt granulation, thermal granulation and liquid granulation. Double roller dry powder granulator equipment is a common granulation method.
What is the principle of the double roller dry powder granulator equipment?
Powder particles are infiltrating bodies of water, and their surfaces can absorb and float water. After spraying the liquid binder in the granulator, the surface quickly absorbs enough water, and a liquid arch bridge such as a meniscus is formed between adjacent particles, which is called the granulation core. Due to collisions, these granulated nuclei will bond into larger agglomerates. Due to the rotation of the granulator, the drop between the powder and the agglomerate is gradually compacted with the rise and fall, and the strength is improved. When the water supply to the granulator stops, the particles continue to rise and fall repeatedly and roll continuously in the granulator, the capillary action of the liquid in the gap between the particles is strengthened, and negative pressure is generated to pull the particles closer together. Finally, all the liquid on the surface of the particles is absorbed by the dry powder of the outer layer, and the particles will not continue to grow larger. The formation process of granulation is through the generation of granulation core, the growth of agglomerates and the spheroidization of particles, so that the fine powder becomes particles with a certain size and strength. After drying, it becomes granulated material, also known as consolidation molding. When the solid powder is wetted, the following situations will occur depending on the amount of liquid added. The pendulum state, the cable state, the capillary state, and the particle in the droplet appear with the increase of the liquid amount. When the wet particles are dried, the particles are consolidated due to van der Waals and electrostatic forces; in addition, solid bridges between particles also play an important role in consolidation. Solid bridges are mainly formed by: (1) soluble constituents crystallize between adjacent particles due to solvent evaporation, bonding adjacent particles; (2) binder solidifies between particles; (3) there may be some The ingredients melt between the particles and then solidify. During compression and granulation, the distance between particles is close due to compression, and the particles are consolidated due to van der Waals force and surface free energy.
What are the performance and advantages?
1. The material is forcibly compressed by mechanical pressure without adding any wetting agent, and the product purity is guaranteed.
2. The process flow is short, the energy consumption is low, and the output is large.
3. The dry powder is directly granulated without subsequent drying process, which is more conducive to the connection and transformation of the existing production process.
4. The particle strength is high, and the increase in bulk specific gravity is more significant than other granulation methods. It is especially suitable for occasions where the bulk specific gravity of the product is increased.
5. The operation flexibility is large, the adaptability is wide, and the extrusion force can be adjusted by hydraulic pressure.