The machinery used for compaction and briquetting is basically identical, but there is one noteworthy difference: in lieu of the matching molds used in briquetting the surfaces of the compaction rollers are smooth, corrugated or waffled. In the event that the fineness of a single- or multi-component bulk material causes drawbacks such as segregation, agglomeration, unfavorable flow characteristics or dust losses the process of compaction/granulation is employed for size enlargement.
Press agglomeration in the absence of binders via roller presses is a basic process by means of which a size enlargement is achieved primarily without the material bridges between particles being established with the aid of binding agents. Instead, the molecular forces of interaction play a significant role, but only if the individual particles can be brought together as closely as possible. This calls for external compressive forces to be applied.
If solid substances compression takes place in the gap between two smooth or profiled rollers running counter to each other, this is known as compaction. A compaction in conjunction with downstream crushing or classifying operations forms the compaction/granulation process. The principle design of a compaction/granulation system is evident from the following diagram assuming a multi-component bulk material to be processed which is used, for example, in the compaction of mixed fertilizers/NPK.
The system comprises four machinery and vessel groups essentially used to perform the following process steps:
- Storage, dosing and blending
- Crushing and classifying
- Final treatment
By means of various conveying systems such as bucket elevator, belt and chain conveyors as well as other conveying devices, the material is transferred to the individual process steps.
This technology is frequently used for the compaction/granulation of potassium chloride (MOP). Millions of tons of granulate are thus produced each year. The largest Köppern presses in operation feature a throughput capacity close to 130 t/h. The granulate yield depends on the particle size range as well as type and treatment of the crude salt and ranges between 35 and 55 t/h with a granulate size of 1-4 mm.
Aside from using the compaction/granulation process for the treatment of individual fertilizers ((i.e. potassium chloride (MOP), potassium sulfate (SOP), ammonium sulfate(AS)) it is also employed for mixed fertilizers ( NPK fertilizers).
Further applications are in the chemical industry and salt mining.