Granulation is an important process in the production of granular fertilizer. It is not only related to the internal and external quality of granular fertilizer products, but also to the size of output and the cost. In addition to the physical and chemical properties of the material itself, the granulation production process is also closely related to the form and mechanical properties of the granulation equipment. The main control index of the granulation process is the moisture content of the material. Generally, it is more appropriate to adjust the moisture content of the material to 50%~55%. The best granulation effect is achieved by steam humidification in production plants with conditions, followed by hot water granulation, which is better than cold water granulation. Excessive moisture content of the material will cause large-size spherical particles to be produced, and too little moisture content of the material will cause a low granulation rate of loose sandy powder. The main types of
organic fertilizer granulators include disc granulator, drum granulator, extrusion granulator and so on.
Disc granulator. The particles made by the
disc granulator are spherical. The particle size is related to the inclination angle of the disc and the amount of water added. The operation is intuitive, easy to control and adjust, and the cost is low. It is suitable for small organic fertilizer plants. The disadvantage of the equipment is that the output of a single device is low. If several devices are to be connected in parallel, more conveying equipment is required. The equipment cannot be sealed and the dust is large. Dust and exhaust gas are easy to overflow and difficult to control. The skill requirements of the granulator are relatively high.
Drum granulator. The advantages are that the single device has a large production capacity, good sealing, dust and exhaust gas do not overflow, it is easy to set the automatic control of feeding and water spraying, the material stays in the cylinder for a long time, and the particle strength is high. At present, large and medium-sized fertilizer production plants all use drum granulation. Some plants also connect
disc granulators and drum granulators in series for secondary granulation, and the effect is also good.
Extrusion granulator. It is mainly double-roller type, double-roller type, and single-axis type. The shape of the particles is mainly pressed according to the shape of the ball socket on the roller skin. There is a large range of choices at present: pillow-shaped, semi-circular granules, rods, tablets and pills, walnuts, flat balls and square strips, etc.
The extrusion granulator is a dry granulator, the moisture content of the material is less than 20%, and no additional water is required during the granulation process. After granulation, there is no need to use a dryer for drying, which saves equipment investment and drying energy consumption.
