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Roller press pellets are widely used for the production of compound fertilizers. There are more than 20 kinds of materials that have been successfully applied to granulating. Ammonium nitrate, urea, ammonium chloride and calcium nitrate in nitrogen fertilizer. Phosphate fertilizer includes ammonium phosphate, calcium phosphate, heavy calcium, phosphate rock, potassium chloride and potassium sulfate, and can add trace elements such as boron, iron, copper, zinc, and so on. Extrusion granulation has no special requirements on the granularity of the raw materials, 1-4mm granular materials and fine powdery materials are available, it’s better to use the granularity of powder material and powdery products , and the cost can be reduced with powdery materials.
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The process of roller press granulator production:
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1
Storage and measurement
Mixed fertilizer raw materials such as urea, ammonium phosphate and potassium chloride are transported from bucket elevator and belt to storage bins.
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2
Squeeze
After mixing, the mixture of fertilizers is extruded by roller. The principle is to shape the material through extrusion. The mixture is fed into the gap between the two oppositely rotating rollers through a vertical screw feeder. During the extrusion process, the pressure of the material gradually increases, and when the gap between the two axes is in a very small position, The material is relatively stressed and then gradually decreases until reach the zero.
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3
Crushing and classified
The plate formed in the roller press should be further broken, and if you want to reach the demanded particle size, you need to through the classified. There is a particular designed plate crusher under the roller press machine, the plates have been crushed the slices by it. The fine particles on the lowest sieve are recycled to the mixer and then extruded. However, the large particles retained on the top of the multi- stage sieve need to be further broken. After crushing, it returns to sieving. It’s very important to make a correct choice about the crushing and screening machine, it has a great effect to the economic of the press and granulator system.
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4
Polishing and dressing
In usual, the final products need to through the polishing and dressing. Irregular shaped particles are worn round the drum to circle the edges and corners. The fine powder produced during polishing is recycled through screening . When dressing, the anti caking agent is usually added. The final product of the plant is granular fertilizer (1-4mm) within a certain range of granularity.
