Waste plastics are broken and cleaned to avoid secondary pollution by paying attention to these|plastics recycling machine

Waste plastics are broken and cleaned to avoid secondary pollution by paying attention to these|plastics recycling machine

Aug 25 2021

After plastic products are discarded, they must be crushed by some means before they can be recycled or further molded into various recycled products. In the process of secondary utilization of waste plastics, attention should be paid to these links in order to avoid secondary pollution and make the recycling of waste plastics lose the significance of environmental protection.
Broken link
From the different technical principles, there are four basic forms of crushing. They are:
Crushing technology
The material is crushed into small pieces by the relative compression force of the material. It is suitable for large-volume waste plastic products.
The mode of action includes, for example, the squeezing action of two relatively moving metal plates, the rolling action of two relatively rotating rollers, and the squeezing action of the inner cone rotating eccentrically in the outer cone.
Crushing technology
The material is crushed by the external impact force, which is suitable for brittle materials. Its mode of action includes the impact of external hard objects (such as hammering with a hammer), the high-speed impact between the material itself and the fixed hard steel plate, and the impact between the materials.
Grinding technology
The material is crushed into fine particles by rolling between the grinding bodies of different shapes, which is suitable for block materials.
Shearing technology
The material is broken into small pieces or fragments under the action of cutting, puncturing and shredding by sharp tools such as blades. It is suitable for tough materials, films, sheets and soft products.

Selection of crushing equipment

The choice of crushing equipment mainly depends on the type and shape of the material to be crushed and the degree of crushing required. Different materials of waste plastics have different properties, and the crushing equipment used may be different.
For example, rigid PVC, PS, plexiglass and other materials are brittle plastics, which are easily broken into small pieces under the action of compression or impact force. Such plastics are suitable for compression or impact crushing equipment; while PE For materials with good toughness at room temperature, such as PP, PA and ABS, shear crushing equipment is suitable; for some low-temperature brittle materials, such as soft PVC, low-temperature crushing equipment is suitable.

Waste plastic cleaning technology

Intermittent wet cleaning
First, put the waste plastic into a sink for washing, and use a plastic mixing machine to remove the loose dirt adhering to the surface of the plastic, so that it sinks to the bottom of the tank; For further purification in the medium; for firmly adhered dirt, such as printing inks and paper labels coated with adhesives, the larger ones can be picked out manually, and after being crushed by a plastic crusher, they can be immersed in a hot alkali aqueous solution tank for a period of time. , And then use mechanical stirring to make them rub and collide with each other to remove dirt; finally, the cleaned crushed waste plastic is sent to a centrifuge to be dried, and dried by two steps of hot air until the residual moisture is less than 0.5%.
Continuous wet cleaning
The waste plastics are sent to the plastic shredder by the conveyor belt for coarse crushing, and then sent to the bulk separation section, where sand and gravel are sunk into the bottom of the water and sent away at regular intervals. The floating material enters the wet mill through the conveying roller, and then enters the sedimentation tank. All things heavier than water are separated out, even the smallest particles are no exception, to achieve the best cleaning effect.
Hot washing of bottle flakes
The hot washing of bottle flakes includes steps such as floating washing and rinsing. The hot washing and floating washing unit can effectively remove bottle caps, bottle rings, oil and beverages remaining in the bottle, external glue and other impurities; the rinsing unit can remove the residual medicine after hot washing, and make the surface of the bottle flakes The PH value tends to be neutral, ensuring the cleanliness and transparency of the bottle flakes.
Anhydrous cleaning
The waterless cleaning of waste plastics is to use physical forces such as friction, grinding, and collision to remove and disperse the dirt attached to the flakes to the fragments of a certain thickness and to a certain size, and separate them in the air medium through a dust collector and a cyclone. Dust removal and separation by the filter to obtain clean plastic fragments.
Anhydrous cleaning produces no waste water, and the secondary pollution is greatly reduced. It is currently the key area of ​​related research, and its technology, process and equipment are in the exploratory stage.

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