The Crushing Characteristics and Conditions of Double-Roller Crusher

Double-Roller crusher is also called extruding mill or roller mill. Because it is a kind of highly efficient and energy saving device, it is quickly popularized in cement industry and gradually expanded to be used for crushing all sorts of hard materials and it can also be used to finely crush cement raw material and clinker, blast-furnace slag, limestone, coal and other brittle materials. In addition, it is gradually used in the industrial fields of fertilizer and ore dressing.

Double-roller crusher is very similar to traditional roller crusher in the form, but there are two essential differences between them: double-roller crusher adopts the principle of quasi static crushing. Compared with impact crusher, it can save about 30% of energy; it implements lamination crushing on the materials, which is intergranular crushing and the crushing efficiency is high and the extrusion stress between the materials can be adjusted through the roller pressure which generally can reach 150-300Mpa.

The material crushing of roller crusher depends on the two rollers that have smooth roll surface and rotate with the opposite direction and at the same speed and the two rollers crush materials relying on the extruding action of high pressure. The Materials are delivered by belt conveyor into quantitative bin. The sensor is used to control the quality of the materials in the bin. Materials are discharged from the feeding mouth on the upper side of the roller and go into the gap between the two rollers. Under the extruding action of high pressure (50~300MPa), the materials are presses into compact material cakes filled with crack. The mechanical strength of the material cakes is low, and a lot of fine powders are contained in them, so that they can be easily crushed even by fingers.

The crushing principle of double-roller crusher is high-pressure lamination crushing or intergranular crushing. The conditions for lamination crushing are as follows:

(1) Materials should have a certain material pressure before nipped by the roller, otherwise it will be difficult to obtain the required material layer, and it is achieved with the aid of column feeder with a certain height.

(2) The particle size of the materials must be smaller than the value of roller gap (working opening), otherwise crushing material layer cannot be formed. As for materials whose particle size is bigger than the roller gap, the crusher will first conduct grain crushing before material layer forms. But if the particle size of the feeding material changes frequently, the vibration of the equipment would increase, which will have a bad effect on the service life of the spare parts.

(3) The hydraulic system should have enough extrusion force; otherwise the layers cannot be crushed with high pressure. The test proves that intergranular crushing will not realize if the extrusion force is less than 500 Mpa. But it does not mean that the higher the pressure is, the better the effect will be. When the pressure exceeds a certain value, increasing the pressure not only cannot improve the effect, but will have some bad effects. The best pressure value should be determined after the test, analysis and comparison.