Selective Crusher

Product Uses

The selective crusher is primarily used to process screened lump coal, but it can also be employed for raw coal. When processing raw coal, a fixed screen is typically installed at the feed end to pre-screen out fine coal; the oversize material then enters the crusher, resulting in improved crushing performance. Alternatively, no lift plates are installed at the drum’s feed end, allowing the fine coal to be screened out directly. Depending on the coal quality, the gangue discharged from the crusher can either be loaded directly onto trucks or subjected to reverse sorting. This equipment can replace the three separate processes of manual gangue removal, crushing, and screening.

Operating principle: A selective crusher exploits the difference in hardness between coal and gangue—specifically, their varying crushability under the same impact-crushing conditions—to separate the two materials. The material is then screened to remove oversized gangue pieces and other foreign matter. In practice, as the crusher’s crushing drum rotates, the feed coal lumps are lifted by lifting plates; when they reach a certain angle, they slide down from the elevated position. With the drum continuously turning, the coal lumps are repeatedly lifted and dropped. Coal that is crushed to a size smaller than the screen openings passes through the screens and is discharged from the machine, while larger, harder gangue pieces or metallic impurities are not easily broken and are conveyed by the machine to the discharge end, where they are expelled via the discharge chute. To effectively use a selective crusher, the following conditions should be met: (1) There must be a significant difference in hardness between coal and gangue; the greater the hardness disparity, the more pronounced the difference in crushability, and the better the performance of the selective crusher. (2) The product does not require retention of large coal lumps, meaning the user has no specific particle-size requirements. (3) Gangue particles larger than 50 mm must account for at least 30% of the total mass in that size fraction. (4) Oversized gangue pieces larger than 300 mm must be pre-separated to prevent damage to the screen plates.

Structural Features

The structure of the selective crusher consists of a drum, a drive system, inlet and outlet chutes, a sealing cover, and a hopper. The drum is the main component of the selective crusher; it is composed of two large drum rings, end caps, channel-section assemblies, screen plates, lifting plates, and guide plates. The end drum rings are monolithic cast steel parts, while the I-beam assemblies are bolted together to form the cylindrical frame. To reduce impact noise from the material, a 10-mm-thick rubber pad is placed between the screen plate and the main beam. The drum rotates by friction between the supporting rollers and the drum rings; the screen plates on the drum are cast from manganese steel, offering excellent wear resistance and impact resistance. The apertures are circular and tapered to prevent material blockage. The lifting plates are fabricated by welding steel plates and are used to lift the material inside the drum, guiding it axially along the drum’s length. Because the lifting plates are frequently subjected to friction and impact from the material within the drum, they, like the screen plates, are considered wear parts. To ensure that the material advances smoothly along the drum, to control the number of drops within the drum, and to adjust the residence time of the material inside the drum, the arrangement of the lifting plates can take several different forms:

1. The lifting plate is parallel to the roller axis, while the simplified axis forms a certain angle with the horizontal plane;

2. The lifting plate is arranged at a specified angle relative to the cylinder axis; in this configuration, the cylinder axis may be parallel to the horizontal plane or inclined at a certain angle.

3. Mixed form.

The selective crusher employs the third arrangement configuration. At the feed end of the drum, lift plates inclined at 12° relative to the drum’s longitudinal axis are installed to elevate the material and increase its axial flow velocity; these lift plates are pivotal in determining the equipment’s processing capacity. The installation angle of the lift plates can be adjusted according to the hardness difference between coal and gangue, thereby controlling the number of drops. The use of lift plates to regulate the drop count is one of the machine’s key features, broadening its application range and enabling it to achieve relatively optimal crushing performance under specific material conditions. Generally speaking, the greater the hardness disparity between coal and gangue, the fewer drops are required. The selective crusher is equipped with two independent drive systems—one at the front and one at the rear—each comprising a power unit, a set of drive idlers, support idlers, and axial thrust rollers. In addition to providing support, the drive idlers also perform the transmission function. Large flanges at both ends of the drum are mounted on the front and rear drive idlers as well as the support idlers. Power is transmitted from the electric motor through a reducer to the drive idlers, which then transfer the torque to the large flanges via friction, thereby driving the rotation of the drum. Compared with selective crushers that use gear or chain drives, this friction-drive system is simpler, easier to maintain, and more straightforward to manufacture. To prevent axial movement of the drum, thrust rollers are installed at both ends. During operation, the drum continuously crushes and screens the material, generating substantial dust that pollutes the environment and degrades working conditions. After years of research and testing, the machine has made notable progress in dust collection and noise reduction. A sealed enclosure fully surrounds the drum to isolate it from the external environment, with rubber seals used at the joints between the two ends. The large flanges at both ends of the drum are tightly sealed by two sealing covers, which themselves are also sealed with rubber gaskets.