Screening Crumb Rubber at 325 Mesh (44 Microns)
Elcan was approached by a company who takes old tires and breaks them up into smaller ground pieces called crumb rubber. This ground rubber has numerous applications – one of the main uses is for FieldTurf. The crumb rubber in these turf fields provides a cushioning on and between the turf and the hard surface below the field. With the construction boom of these fields, a large demand for accurately screened crumb became critical. Crumb rubber with dust in it was thought to be a health concern.
One of the biggest problems screening crumb rubber is that it is very lively and wants to bounce away from the screening surface. Elcan used the Minox Tumbler screener which employed a vacuum under the screen to calm the particles down and pull them through the mesh. The unique air sweep feature on the Minox’s allowed the use of this vacuum as well as acting as a great de-duster of the crumb. This de-dusting also helped eliminate any health concerns by removing the dusty particles or satellites that wanted to cling on to the larger particles.
Several other companies are using crumb rubber in spray dry applications or for sealants. They were looking to screen crumb rubber at 325 Mesh (44 microns). They had no success with their conventional screeners and came to Elcan looking for help to find a solution. The difficulty screening crumb rubber results from the flowability of the product. This crumb rubber is extremely sticky and forms tight agglomerations. The particles also caused screen blinding after they coated the mesh cloth. The crumb rubber is naturally contaminated with nylon fibers that are used to form the biased ply tired. Elcan Industries tried numerous methods before finally being able to find one machine that provided solutions to these three problems. This again was the Minox Tumbler Screener.
The Minox machine has a number of unique devices and for this application, the air knife technology was perfect for cleaning the screens and the vacuum was again helpful for passing the particles through the mesh. Elcan used multiple decks to remove the coarse particles as well as the lint that formed from the nylon. The lint actually balled up like tumbleweeds and as it rolled across the surface of the top deck, it attracted and grabbed onto any loose lint. When the tumbleweed became dense, it would discharge itself out the overs chute.
The fine particles needed extra help to deagglomerate at the 325 mesh level so Elcan developed a system to beat in a flow aid that kept the individual particles separated. While the flow aid wasn’t harmful to the product, the end users wanted as little as possible in the crumb. The 325 mesh deck made a 94% efficient cut and the fines and the flow aid were then sent into a cyclone and baghouse.
When this fine stream passed through the cyclone, the flow aid and fine crumb rubber separated with the crumb falling out of the cyclone and the flow aid continuing to the baghouse with the air stream. This is the first time crumb rubber has ever been separated at this small of a size.
Elcan Industries was able to successfully create a new product for the customer and find a solution to their screening needs. Elcan toll screened thousands of pounds for the customer while the equipment was being manufactured and installed in their facility. Since then, Elcan has helped numerous crumb rubber companies found a solution to their separation problems using this custom technique.