Stand-alone machine for recycling tasks

Having performed the previous tasks, such as screening and sorting the materials on the demolition site or reducing the volume of the materials to recycling using the additional equipment describes in the previous section 8.1, the recycling tasks can start.

Such recycling operations can be carried out with stand-alone machines designed specifically for recycling tasks. A standalone or stand-alone equipment is any machine or system that performs its function without needing another device or attachment.

The use of these machines has the great advantage of performing the operations with machines designed specifically for recycling tasks, which can reach very high performances and achieve final products of very high quality. Moreover, being independent pieces of equipment of the ones use for demolition tasks, both jobs can be performed at the same time.

Although, this type of equipment has the disadvantage of needing a higher investment and needing more planning for the transport and placing of the recycling machines.

Jaw Crusher

This is a type of crusher that is widely used in the crushing processes.

It is usually preferred for the crushing of large blocks of hard and abrasive materials.

All jaw crushers feature two jaws: one of which is fixed while the other moves. The working principle of jaw crushers is based on the reciprocating movement of the movable jaw that compresses and crushes the materials between itself and the fixed jaw, as the material enters the zone between the jaws.

The moving jaw moves back and forward against the fixed jaw, and material fed from the top of the machine is compressed between the two, breaking it into smaller pieces. As the moving jaw moves away from the fixed jaw, the crushed material is discharged from the crusher at the bottom, with the size of the ejected material determined by the gap between the jaws.

Jaw crushers can also be equipped with an after-screen and return conveyor. In closed circuits, they produce a higher-defined end product.

Jaw crushers are generally defined by their opening size.

It is important to take into account that jaw crushers have limitations in producing small-sized gradations and products with high shape requirements.

Jaw crushers can be equipped with overband magnets behind the crusher discharge to extract the metals.

Impact Crusher

Impact crushers reduce mineral materials such as concrete, asphalt and natural rock in size to produce a valuable commodity product.

A fast-spinning rotor throws the material against solid stationary impact walls. The striking and impact cause the material to shatter into smaller pieces due to the impact to the walls, impact hammers and own material. The result is a very homogenous and cubical product leaving the crusher box.

This machine is ideal for producing a spec product without the need for a primary jaw crusher. It produces superior finished material compaction, that is easier to grade and compact making it perfect for base and subbase.

It is a piece of equipment intended to produce specific end products. It can produce perfect aggregates from construction & demolition waste or can recycle asphalt.

There are 3 main types of impact crushers: Horizontal Shaft Impactor (HSI),  Vertical Shaft Impactor (VSI), and Reversible Vertical Impact Crusher.

However, VSI crushers are not used in recycling applications as they are very vulnerable to metal and other inconsistencies and can only handle a very limited feed size. Normally they are used in tertiary or quarternary crushing stages, mostly for the shaping of natural rock aggregates.

The Horizontal Shaft Impactor is the most widely used machine in recycling as it can handle large feed sizes, achieves a high reduction ratio and creates well-shaped quality products. HISs are uncritical with uncrushable components like steel reinforcement or wood and other impurities. The separation of concrete from steel reinforcements is very efficient and optional overband magnets behind the crusher discharge can extract the metals from the material flow on the conveyor belt. In closed circuit, with after screen and return conveyor, it produces several specific fractions which can be reused in several ways. A windsifter can be installed to take out lightweight contaminants like paper, plastics or wood.

The reversible impact crusher is more vulnerable and is only used in secondary and tertiary crushing of rock, oversized gravel and recycling building materials (e.g. Asphalt).

Recycling universal shredder

A C&D shredder more or less disintegrates the material by cutting and tearing.  It contains 2 to four shafts and can run at high and low speeds. Several shafts can be installed in case specific material needs to be shredded.  The recyclable use after shredding depends highly on the feed material. An overbelt magnet can extract the metal.

The feed material is loosely filled into the infeed hopper. A hydraulically driven slide pushes the material along the base plate and toward the cutting unit. The feed material is shredded between the rotor equipped with blades and the counter-blade mounted on the static blade seat. Once a defined particle size is reached, the shredded material falls down out of the machine through a screen basket. The size of the discharge material is defined by the hole pitch of the screen. It can range from 10 to 120 mm.

Since it is never possible to completely avoid contaminants getting into the feed material, the universal shredder has a hydraulically movable base plate that can be retracted if necessary. This allows for the fast removal of contaminants.

Screening equipment (scalping and classifying)

In recycling applications scalpers and classifiers are used for screening, scalping, separating C&D waste, aggregate, soil

Classifiers are specially designed for fine screening with a limited feed size. Scalpers have a more robust design and optimized material flow for heavy-duty applications with large feed sizes, but can also be used for fine-screening applications. Depending on the application and preferred screening fractions, suitable screen media need to be selected.

Screens are also used for washing applications, where gradations get separated from adherent particles like dust or soil or where sticky impurities impede dry screening processes. Washing screens are usually modified classifier screens with water piping and spray nozzles, to apply high water volumes. The fines conveyors are removed and substituted by a troth, collecting the dirty water to be forwarded to subsequent separation, dewatering and cleaning processes.

The major task that can be achieved with this equipment are:

  • Separating material for recovery and recycling
  • Sizing and classifying
  • Dewatering materials
  • Removing metals (with overband magnet(s)
  • Removing contaminations like paper, plastic, and wood with windsifter
  • Sorting with the picking station on the main conveyor
  • Removing sticky material from solid materials (like sticky ground to aggregate)
  • Recirculate load by scalping off oversized materials
  • Check screening12

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