Crushers are machines for crushing lumpy feed material into smaller grain sizes in the coarse to medium size range. They are mainly used to produce broken minerals from stones , but are also used in the food industry, e.g. B. to be found in carcass recycling .
In contrast, one speaks of mills when the target grain size is to be in the fine or very fine range. As a rule, this limit is seen with a target grain size in the range from 1 mm to 10 mm. Crushers are most widespread in the industrial processing of mineral raw materials, see quarries , lime works , gravel works , mining and secondary materials, see recycling , building rubble . Crushers can be used both stationary and mobile (on wheels or on caterpillars).
In the past, stationary systems were the only solution for processing residual construction waste. In the mid-1990s, mobile recycling with compact systems developed and is now on the advance worldwide. Mobile crushers can not only move around the construction site, but are mobile as a whole. Due to the relatively low transport weight, they can be brought to the processing site in order to directly recycle the material there. In the opposite case, all material has to be transported from the construction site to the stationary processing plant, which is associated with transport costs and causes increased truck traffic.
Goals of shredding
- Reduction of the upper grain sizes
- Change in grain size distribution
- Change in grain shape
- Selective opening of compounds in order to separate and expose the individual components
Crushers can be classified according to the prevailing crushing principle.
The shredding energy acts with great forces and at low speed on the material to be processed.
The material to be shredded hits a work surface with high energy. In impact crushers with a horizontal shaft, the energy is introduced into the working surface (rotor with blow bars), which then acts on the incoming rock, and in impact crushers with a vertical shaft, the material inside a rotor is accelerated by centrifugal force , and then selectively against a fixed work surface to be guided.
The work surface is accelerated and guided against the material to be shredded, which ideally lies in front of a solid surface.
Shear / friction
The material to be shredded is located between two working lines (shear) or working surfaces (friction), which exert contact pressure and are simultaneously moved in opposite directions.
Areas of application
- Production of sand , gravel , chippings and crushed stone in quarries and gravel works
- Processing of ores , salts , coal , minerals in mining
- Coal processing in the power plant
- Processing of solids in the chemical and pharmaceutical industry
- Processing of cement
- Food industry
- Recycling industry
- Processing of secondary building materials , such as B. Concrete recycling
Assessment of crushers
The main criterion for assessing crushers is the crushing effect. Since every crusher inevitably not only delivers a single desired grain size , but always a spectrum of sizes, the comparison of the grain size distribution in the feed material versus the grain size distribution in the end product is used for assessment. This distribution curves are grading curves called.
Typical degrees of size reduction in rock processing:
|designation||Degree of shredding|
|Primary gyratory crusher||6 to 8|
|Jaw crusher||3 to 5|
|Horizontal impact crusher||5 to 8|
|Secondary cone / gyratory crusher||3 to 4|
|Vertical impact crusher||1.5 to 3|
In addition to the crushing effect, other crushing effects can be important, such as cubic grain shape , fracture surface , hardness , selectivity of the crushing. Other important aspects are throughput, operating costs (especially for wear and tear and energy consumption), investment costs and ease of maintenance.