Fertilizer production technology - Granulation -1- Wet granulation - Disk granulation 3
Date:2024/07/08
Factors affecting the quality of disc granulation
For the Disc Granulator, the factors that affect the particle size, hardness, yield and production efficiency after granulation are as follows:
One, Disc diameter
The disc diameter affects the productivity and hardness of the grain after granulation. It is the most important factor controlling production. The larger the diameter of the disc, the higher the output per unit time. In addition, the larger the diameter, the longer the rolling distance of the particles, the greater the gravity when falling, the greater the compression force of the particles, and the greater the density. However, due to the economy of equipment manufacturing, installation, operation and production, the diameter of the disc is often controlled below 6 meters.
Two, the height of the edge of the disc
The retention time of particles in the disc is affected by the height of the retaining edge of the disc. When the particles formed by the disc granulation roll, the friction with the disc causes the particles to be graded, with smaller particles sinking to the bottom of the disc, larger particles floating to the top, and when the particles reach a predetermined size, they are ejected from the edge of the disc.
The higher the retaining edge, the longer the resident time of the particles, and the larger the grain size of the grown particles. However, if the height of the flange is increased, it will also cause a decrease in productivity per unit time, and the weight of the formed large particles may exceed their own binding force, which will disintegrate again during the granulation process, resulting in low production efficiency.
Under normal circumstances, the height of the disc flange is proportional to the diameter of the disc. The commonly used formula is H=0.20D, where H is the height of the disk and D is the diameter of the disk. For special applications, such as the granulation of high strength particles, such as the granulation of low particle size, 2 heavy duty or truncated cone trays can be used. If you want to make granulation of large particles, use a multistage disc or a conical disc.
Three, disc tilt Angle
The Angle of the disc affects the particle roll. When the inclination is insufficient, the powder does not roll when the disc is rotating, and the powder is still stuck to the surface of the disc, and the crystal nucleus cannot be formed and grown. Therefore, the inclination of the disc should be greater than the inclination of the raw material wetted before granulation. However, the greater the inclination of the disc, the greater the inclination of the particle, the faster the particle will fall, and if it exceeds the binding force of the particle, the particle will disintegrate. At the same time, if the inclination exceeds the limit, the particles cannot rise along the rotation direction of the disc, stay at the bottom and deposit, and cannot grow. Under normal circumstances, the disc inclination is 35 to 55 degrees, and the most commonly used Angle range is 40 to 50 degrees. If conditions permit, it is best to determine the optimum inclination Angle in the preliminary test.
Four, disc rotation speed
The raw materials and particles are pulled up by the rotation of the disc, and after rising to a certain extent, they roll down under the action of gravity, and at the same time, under the action of centrifugal force, they are thrown to the outer edge of the disc. This rolling movement makes the particles collide and contact each other. The viscosity and surface tension of the surface liquid layer make the particles sticky and compressed, and the particles gradually grow up. Therefore, the rotation speed of the disc greatly affects the formation and growth of particles. If the rotation speed is too slow, the height of the particles is short, the rolling distance is not enough, and the formation and growth of the particles are slow. On the contrary, if the speed is too fast, the particles are thrown out of the pan under the action of centrifugal force, and the pellets are thrown out of the pan before they have time to form. Usually, the optimal speed of the disc depends on the type of powder or particle. This formula is explained in detail below.
Five, the amount of liquid
The liquid sprayed on the disc forms the liquid crosslinking needed for granulation, which is essential for nucleus aggregation and particle growth. Therefore, spraying too much liquid and too little will affect the formation and growth of particles. In addition, the more evenly distributed the liquid injected, the more uniform the formation and growth of spherical particles. Therefore, the spray width of the spray liquid should be the same as the input width of the raw material particles, the pressure should be constant, and the raw powder and particles can be evenly contacted. It should be noted that the ejected liquid must not be directly ejected to the bottom of the disc. If the liquid falls on the bottom of the disc, the powder there will become too wet and stick to the surface of the pan, interfering with the granulation process.
Six, Determination of the spray position of raw material powder and liquid
In order not to interfere with the rolling motion of the particles, the input of the raw powder and the spraying position of the liquid are removed from the rolling track zone of the particles. Under normal circumstances, if it is a clockwise disc, feed from the upper right corner of the disc, and then spray the feeding liquid from the middle right of the disc.
Seven, the position of the scraper
In many cases, a scraper is attached to the top of the disc to scrape off the ingredients stuck to the bottom and edges of the disc. The length of the scraper is about 0.15R (R: refers to the radius of the disc), and the vertical center line of the disc is tilted 15 to 25°, away from the track area of the particle rolling, set in the track area away from the particle rolling.
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.
For the Disc Granulator, the factors that affect the particle size, hardness, yield and production efficiency after granulation are as follows:
One, Disc diameter
The disc diameter affects the productivity and hardness of the grain after granulation. It is the most important factor controlling production. The larger the diameter of the disc, the higher the output per unit time. In addition, the larger the diameter, the longer the rolling distance of the particles, the greater the gravity when falling, the greater the compression force of the particles, and the greater the density. However, due to the economy of equipment manufacturing, installation, operation and production, the diameter of the disc is often controlled below 6 meters.
Two, the height of the edge of the disc
The retention time of particles in the disc is affected by the height of the retaining edge of the disc. When the particles formed by the disc granulation roll, the friction with the disc causes the particles to be graded, with smaller particles sinking to the bottom of the disc, larger particles floating to the top, and when the particles reach a predetermined size, they are ejected from the edge of the disc.
The higher the retaining edge, the longer the resident time of the particles, and the larger the grain size of the grown particles. However, if the height of the flange is increased, it will also cause a decrease in productivity per unit time, and the weight of the formed large particles may exceed their own binding force, which will disintegrate again during the granulation process, resulting in low production efficiency.
Under normal circumstances, the height of the disc flange is proportional to the diameter of the disc. The commonly used formula is H=0.20D, where H is the height of the disk and D is the diameter of the disk. For special applications, such as the granulation of high strength particles, such as the granulation of low particle size, 2 heavy duty or truncated cone trays can be used. If you want to make granulation of large particles, use a multistage disc or a conical disc.
Three, disc tilt Angle
The Angle of the disc affects the particle roll. When the inclination is insufficient, the powder does not roll when the disc is rotating, and the powder is still stuck to the surface of the disc, and the crystal nucleus cannot be formed and grown. Therefore, the inclination of the disc should be greater than the inclination of the raw material wetted before granulation. However, the greater the inclination of the disc, the greater the inclination of the particle, the faster the particle will fall, and if it exceeds the binding force of the particle, the particle will disintegrate. At the same time, if the inclination exceeds the limit, the particles cannot rise along the rotation direction of the disc, stay at the bottom and deposit, and cannot grow. Under normal circumstances, the disc inclination is 35 to 55 degrees, and the most commonly used Angle range is 40 to 50 degrees. If conditions permit, it is best to determine the optimum inclination Angle in the preliminary test.
Four, disc rotation speed
The raw materials and particles are pulled up by the rotation of the disc, and after rising to a certain extent, they roll down under the action of gravity, and at the same time, under the action of centrifugal force, they are thrown to the outer edge of the disc. This rolling movement makes the particles collide and contact each other. The viscosity and surface tension of the surface liquid layer make the particles sticky and compressed, and the particles gradually grow up. Therefore, the rotation speed of the disc greatly affects the formation and growth of particles. If the rotation speed is too slow, the height of the particles is short, the rolling distance is not enough, and the formation and growth of the particles are slow. On the contrary, if the speed is too fast, the particles are thrown out of the pan under the action of centrifugal force, and the pellets are thrown out of the pan before they have time to form. Usually, the optimal speed of the disc depends on the type of powder or particle. This formula is explained in detail below.
Five, the amount of liquid
The liquid sprayed on the disc forms the liquid crosslinking needed for granulation, which is essential for nucleus aggregation and particle growth. Therefore, spraying too much liquid and too little will affect the formation and growth of particles. In addition, the more evenly distributed the liquid injected, the more uniform the formation and growth of spherical particles. Therefore, the spray width of the spray liquid should be the same as the input width of the raw material particles, the pressure should be constant, and the raw powder and particles can be evenly contacted. It should be noted that the ejected liquid must not be directly ejected to the bottom of the disc. If the liquid falls on the bottom of the disc, the powder there will become too wet and stick to the surface of the pan, interfering with the granulation process.
Six, Determination of the spray position of raw material powder and liquid
In order not to interfere with the rolling motion of the particles, the input of the raw powder and the spraying position of the liquid are removed from the rolling track zone of the particles. Under normal circumstances, if it is a clockwise disc, feed from the upper right corner of the disc, and then spray the feeding liquid from the middle right of the disc.
Seven, the position of the scraper
In many cases, a scraper is attached to the top of the disc to scrape off the ingredients stuck to the bottom and edges of the disc. The length of the scraper is about 0.15R (R: refers to the radius of the disc), and the vertical center line of the disc is tilted 15 to 25°, away from the track area of the particle rolling, set in the track area away from the particle rolling.
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.