Rotary drum granulator for npk compound fertilizer and its working principle

This article will introduce what a fertilizer drum granulator is and the structure and design principles of the drum granulator.

What is a npk compound fertilizer rotary drum granulator?

The drum granulator is a commonly used equipment in the granulation of phosphorus compound fertilizers. It produces monoammonium phosphate, diammonium phosphate, nitrogen-phosphorus-potassium compound fertilizer, double superphosphate and other products. The drum ammoniation granulator used in the continuous ammoniation granulation process is called a drum ammoniation granulator. The structure of a typical drum ammoniation granulator is similar to that of a shot granulation dryer. The cylindrical drum is supported by supporting wheels and gear wheels, and the cylinder is rotated by the driving device through gear transmission. The machine is equipped with a slurry spray pipe and an ammonia distributor, and the granulated products are discharged from the discharge box at the end of the drum.

What are the design parameters of a rotary drum granulator?

The drum ammoniation granulator was developed by American TVA in the early 1950s. So far it has been widely used in the production of phosphate and compound fertilizers in various countries around the world. According to the design guidelines of the American TVA drum ammoniation granulator, the length of the cylinder is very short, the diameter-to-length ratio is generally 12, and it is a light cylinder without copying plates. There is a retaining ring at 3/4 of the length of the cylinder, which will The cylinder is divided into two parts: ammoniation zone and granulation zone.
The height of the retaining ring is about 1/4 to 2/5 of the cylinder diameter, so that the material filling factor in the machine can reach 15% to 30% of the total volume. The residence time of materials is 2 to 15 minutes. The surface area of the cylindrical part is 0.1~0.2m2/(t·h). The flow rate of materials is 29.3~48.8t/(m2·h). In order to ensure good mixing performance of the materials, the optimal speed of the granulator is 11~15/D, r/min. D is the diameter of the granulator (m)

What is the liquid ammonia device of compound fertilizer drum granulator？

There is a pipe beam near the axis of the cylinder to install the ammonia distributor and slurry spray pipe. The return material is added from the head of the drum granulator, and a rolling material bed is formed under the rotation of the cylinder. The slurry is discharged from the material The slurry pump pressurizes the material and sprays it on the material bed from the nozzle of the slurry spray pipe for granulation.
The gaseous ammonia is sprayed out at a very high speed through the ammonia distributor buried deep under the material bed, so that the bed material can be further ammoniated to reach the required N/P ratio. The ammonia distributor adopts a duckbill type, or is inserted into several branch pipes with flat ends, and is buried in 1/3 of the total height of the material bed. The size of the gas ammonia outlet cross-section should be adapted to the gas volume and outlet speed to avoid being blocked by the material in the bed.
The length of the ammonia distributor recommended by TVA is approximately 3/4 of the length of the drum granulator. The drilled holes in the pipe usually have equal hole spacing. The total cross-sectional area of liquid ammonia openings is 0.0028cm2/(kg·h), and the total opening cross-sectional area of gas ammonia is 0.0142 cm2/(kg·h). The material of the tube is stainless steel 316L. The flow rate of air passing through the granulator can be 1.22m/s.

What is the anti-sticking device of compound fertilizer drum granulator?

The slurry nozzle adopts a standard centrifugal or spiral nozzle, which requires uniform spray droplets. The size and quantity of the slurry nozzles are determined according to the required spraying volume of the slurry; the material should be stainless steel.
In order to prevent materials from sticking in the carbon steel cylinder, several flexible rubber plate linings are laid along the circumference of the inner wall of the cylinder, and flat steel battens are used to fix each other to the cylinder wall with bolts.
There are several breathing holes on the cylinder wall behind each rubber plate. The cross-sectional area should be large enough to ensure that the air between the rubber plate and the cylinder wall is quickly discharged or inhaled, so that when the cylinder rotates upward, The rubber plate can automatically sag and deform by its own weight and the gravity of the adhesive material, causing the adhesive material to crack and fall off, thereby achieving the purpose of clearing the adhesive material on the cylinder wall.
In order to prevent materials from accumulating above the pipe beam, some drum granulators are equipped with pneumatic plate devices. Its working principle is like an air bag, that is, when materials accumulate on the pneumatic plate on the upper part of the pipe beam, the pressure of the compressed air will inflate the pneumatic plate, causing the material to crack and be removed. Its operation is automatically controlled with instruments.

What is a rotary double-shaft drum granulator?

The twin-shaft drum granulator is used in the reverse material granulation process. Because of its simple structure, high flexibility, and ability to adapt to large changes in process operating conditions, it is still widely used.
The double-shaft granulator is a horizontal U-shaped long trough. There are two parallel rotating shafts installed in the trough. Paddle mixing blades are installed on the shafts. The return material and slurry are discharged from the head of the granulator through the feeding port and slurry pipe respectively. join in.
Under the reverse rotation of the two shafts, the slurry and return material are fully mixed, bonded and coated, and granulated. The granulated fertilizer is continuously pushed to the rear of the granulator and discharged from the discharge port.
The operation of the double-shaft drum granulator is related to the properties of the slurry, the particle size composition of the returned material, the ratio of the returned material, the blade shape and its installation angle, the blade speed, etc.
Remember this type of granulator is only suitable for small scale fertilizer production line.

What is a rotary disc granulator?

The operating principle of the rotary disc drum granulator is that the powder added from the feeding tube into the tilted disc adheres to the droplets sprayed by the material liquid sprayer to form small particle groups. The gravity and centrifugal force generated by the rotation of the tilted disk make the small particles roll toward the lower edge of the disk and continuously adhere to the powder, making the particles larger.
At the same time, due to the friction force at the bottom of the disk, the particles roll upward with the disk. When they reach the position of the scraper plate, the unparticled powder passes through the gap between the scraper plate and the bottom of the disk, while most of the particles follow the scraper plate. The scraper flows down to the edge of the plate, and the powder adheres again during the continued rolling process. After multiple cycles, the particles grow from small to large, reaching the size of the finished product and overflowing from the edge of the disc.
The main granulation factors that affect the disc granulator are disc diameter, inclination angle, side height, rotation speed, liquid spray position, scraper position, etc.

What are the main advantages of rotary disc granulator?

It has good classification effect and can control the solution to be sprayed on fine particles, so the granulation rate is high and the generation of large particles is less;
All operations are intuitive and can be adjusted in time according to the granulation situation during the operation.
There is greater flexibility in what kind of goods are produced, and the particle size control range is wide;
It saves investment compared with drum granulator. Its main disadvantages are that it is difficult to collect dust and smoke and cannot effectively carry out ammoniation; at the same time, it is limited to the use of slurry or melt with low viscosity for granulation.

How to calculate the power of rotary disc granulator?

The power of the disc granulator can be calculated according to N (hp) = K,2, and the output can be calculated according to the empirical formula Q (t/h) = K22. where is the disk diameter (m); K1 and K2 are constants, approximately equal to 1.4. The calculation results are available for reference.

Conclusion：

So in this article we introduce 3 types of rotary granulator that is widely used in the fertilizer industry but the question is there are so many organic-inorganic fertilizer production equipment supplier in the world especially in China, so how to choose the correct fertilizer equipment supplier? Here is the Answer: Tongli, choose Tongli and you don;t have to worry about other things. 1 step solution once for all.