In various industrial processes a dust free material with good flowing properties is required. Briquetting and compaction technology are used to form dust free granules from powder. The most economical way for briquetting and compaction is to use a roller press. Roller presses work from very low quantities of 10 kg/h (lab size) to max. 120 t/h. Based on the materials the machines often vary in their design. In mineral processes the design is focused on wear resistance and robustness of the machine, in chemical processes the machines can be made out of stainless steel and gas or dust tight.
Principle of Operation
Briquetting and compaction are the processes for densification in a roller press. This process takes place between 2 counter rotating rolls. The powder will be fed into the machine via force-feeding (by gravity or with a screw). The rolls will take the powder. In the sliding zone there will be a difference in speed between the powder and the rolls. The nib zone starts where the pressure rises from 0 to the maximum value. A further criterion of this zone is that the speed of the material is almost the speed of the rolls. The pressure in this zone is responsible for the strength of the pressed powder. It also differs from material to material. In the deforming zone, the pressure decreases to 0 again. The characteristics of the material and its elastic behavior influence the length of this zone. The material, which will be fed into the roller press, has the biggest influence on the result. Also the tools of the roller press like rolls, feeding system etc. can influence the process.
A roller press consists of: • A feeding system (screw feeding of gravity feeding) for pre-densification and dosing of the material into the rolls. • A pressing system (2 counter rotating rolls) for densification and shaping of the briquettes or flakes. The hydraulic system belongs to the pressing system. It contains of hydraulic piston, accumulator and hydraulic pump. The hydraulic force is the highest force, which could be created between the rolls. Regarding the design of the pressing frame machines can be divided into machines with cantilevered shafts and middle shafts.