Powder granulation technology, as one of the major branch of powder processing, with the requirement of environment protection and the improvement of production process automation degree, its importance is becoming more and more obvious day by day. “Powder product being granulation” is the inexorable trend of powder reprocessing technology in the world.
Processing the powder product into the grain, the major purposes is as the below 3 sides:
（1） Reduce powder dust pollution, improve the working operation condition.
（2） Satisfy the production request, for example, increase porosity rate and specific surface area, improve heat transference etc.
（3） Improve the product physical property (like flowability, ventilation property, bulk density) so as to avoid bad affects like segregation, pulsating movement, agglomeration, bridging etc in next operation process( dry, screening, measuring) and using process(measuring, dosing etc.). It |
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creates the condition for improving the production, automation and operation in closure.
Normally there are two kinds of powder granulation technology, i.e. wet and dry granulation. The present developed fertilizer granulation usually has wet and dry methods, the dry method is under the condition without adding adhesion agent, through pressing or extruding, it becomes agglomerate or slice, then fall to pieces and sieve into grain. The wet methods are using roller, disk, melting, spraying or guniting to granulation.
Take the example of agriculture production: Before 20’s of last century, the fertilizer is used with powder. Although it is convenient to mix the powder fertilizer, it has many disadvantages: segregation, agglomeration, poor fluidity. When used, it easily becomes powder and loose. But with the continuous development of granulation technology, these disadvantageous factors are gradually solved.
During wet granulation, the wet strength of the capillary effect of liquid adhesion agent plays the utmost important role.
When the nest drying, the chemical reaction of the group and the crystallization of dissolved matter forms the solid and crystal and makes grain forming. This technology uses the cone crusher, roller, liquidation equipment etc. The extrusion granulation technology without adhesion agent is a very competitive. Under normal condition, the grain is not formed through the grains’ solid bridging, but through the action force between molecules forming the grain strength. Due to the distance of action force is short and the sizes of the grain requested are almost same, it needs the external extrusion. The compression method can adopt extrusion method (hole pressed material with the fixed diameter) or pressed method (compression on the two sides of material).If the compression happens in the gap of two rollers rolling in different direction, this process is called rolling granulation.
