Fertilizer production technology - Granulation Section - Wet granulation - Disc granulation 2
Date:2024/07/05
Disc granulation principle-The particle formation process of disc granulation
The particle formation process in the Disc Granulator(Pan Granulator) can be divided into the following three stages.
First, Formation of crystal nuclei
The raw material particles are sent into the dish and are in contact with the liquid sprayed by the sprayer, so that the surface of the particles is wet, and a discontinuous liquid cross-linking is formed between the particles, thus making the particles caked. The coarse aggregate formed is gradually compressed through the rotation and rolling of the disc, forming a nearly spherical core with stable viscosity and strength. Because the liquid is sprayed into the fixed area of the disc, the core is formed only in this area. The number of nuclei formed at this stage is essentially the same as the number of particles at the end of future granulation. The strength of crystal nucleus is also related to the stability of particle growth. Particles grown from high-strength nucleons can also grow into large particles of high strength. Second, particle growth
There is a liquid film on the surface of the crystal nucleus formed, and the adhesion between the crystal nucleus and other small particles is also strong when the crystal nucleus is in contact with other small particles. In addition, there is a gap between the particles, which has a certain plasticity. Due to the rolling of the particles, the small particles adsorbed on the surface are rearranged, the liquid between the particles begins to immerse, and the surface tension makes the whole into a single particle. In addition, during the rolling process, due to the action of friction and gravity, as well as the impact of collision forces with other particles, the particles are gradually compressed, becoming more dense and spherical. This process is repeated, and the particles gradually grow larger.
Third, particle molding and completion
When the particles grow to a predetermined size, the amount of liquid between the particles reaches 85-90% of the theoretical saturation value, and the excess liquid penetrates from the surface of the particles to the inside of the particles, increasing the capillary force on the surface of the particles and making the binding force inside the particles stronger. At this stage, the water supply or granulation accelerator is stopped, the liquid film on the surface of the particles becomes thinner, and the particles lose the ability to adhere to smaller particles, and thus stop growing. However, as the particles continue to roll, the particles are further compressed and dense, and under the action of friction, their external shape becomes smooth and spherical. They are finally discharged from the rim of the disc and transported to the next drying process.
Supplement: There are two types of rolling granulation equipment commonly used in the fertilizer industry according to the type of granulation container: Disc Granulator (Pan Granulator) and Rotary Drum Granulator. Vibrating granulator (Horizontal Mixer , Vertical Disc Mixer) also belongs to the category of rolling granulator.
The particle formation process in the Disc Granulator(Pan Granulator) can be divided into the following three stages.
First, Formation of crystal nuclei
The raw material particles are sent into the dish and are in contact with the liquid sprayed by the sprayer, so that the surface of the particles is wet, and a discontinuous liquid cross-linking is formed between the particles, thus making the particles caked. The coarse aggregate formed is gradually compressed through the rotation and rolling of the disc, forming a nearly spherical core with stable viscosity and strength. Because the liquid is sprayed into the fixed area of the disc, the core is formed only in this area. The number of nuclei formed at this stage is essentially the same as the number of particles at the end of future granulation. The strength of crystal nucleus is also related to the stability of particle growth. Particles grown from high-strength nucleons can also grow into large particles of high strength. Second, particle growth
There is a liquid film on the surface of the crystal nucleus formed, and the adhesion between the crystal nucleus and other small particles is also strong when the crystal nucleus is in contact with other small particles. In addition, there is a gap between the particles, which has a certain plasticity. Due to the rolling of the particles, the small particles adsorbed on the surface are rearranged, the liquid between the particles begins to immerse, and the surface tension makes the whole into a single particle. In addition, during the rolling process, due to the action of friction and gravity, as well as the impact of collision forces with other particles, the particles are gradually compressed, becoming more dense and spherical. This process is repeated, and the particles gradually grow larger.
Third, particle molding and completion
When the particles grow to a predetermined size, the amount of liquid between the particles reaches 85-90% of the theoretical saturation value, and the excess liquid penetrates from the surface of the particles to the inside of the particles, increasing the capillary force on the surface of the particles and making the binding force inside the particles stronger. At this stage, the water supply or granulation accelerator is stopped, the liquid film on the surface of the particles becomes thinner, and the particles lose the ability to adhere to smaller particles, and thus stop growing. However, as the particles continue to roll, the particles are further compressed and dense, and under the action of friction, their external shape becomes smooth and spherical. They are finally discharged from the rim of the disc and transported to the next drying process.
Supplement: There are two types of rolling granulation equipment commonly used in the fertilizer industry according to the type of granulation container: Disc Granulator (Pan Granulator) and Rotary Drum Granulator. Vibrating granulator (Horizontal Mixer , Vertical Disc Mixer) also belongs to the category of rolling granulator.