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One-Pass Classification Of Rubber Granules Boosts Output By 30 Percent

A Canadian rubber recycler increased production of crumb rubber by 30%, and sales and profits by a like amount, with adding a new production line employing a circular vibratory screener that separated large and small rubber particles in one pass.

This contrasts with an original two-step process in which two 4'x10' rectangular screens classified particle sizes from 6 mesh to below 20 mesh in two stages after shredding passenger car tires. The 2 in. shredded tire particles exited a primary cracker mill, then were separated on a 5'x12' rectangular screen to 6 mesh and smaller size. After a magnet removed metallic particles, the rubber particles were granulated in a second cracker mill, then classified by the two 4'x10' screens. The screens first separated the large 6-10 mesh sizes, then the operator changed screens and re-ran the 10 mesh to below 20 mesh particle sizes.

This double handling created a production bottleneck because a pile of semi-finished material outstripped the capacity of the screens. The bunker, growing as high as 30 feet, also consumed valuable plant floor space. Depending on customer requirements, The company occasionally needed to run the material a third time with smaller-mesh rectangular screens.

The rubber recycler switched to classifying the large sizes with the original two 4'x10' screens while classifying the below-10-mesh granules with a 60 in. diameter VIBROSCREEN® circular vibratory separator from Kason Corporation. By eliminating the double handling, production rose by 30 percent.

The recycler's former owner said, "We were able to run two or three different size products at the same time where we could only run one size at a time. Now, finished product awaiting shipment filled the space vacated by bunker storage.

"Cost savings were tremendous." He said the VIBROSCREEN separator paid for itself in a few months from the increased production. Moreover, the circular screener's high throughput rate opened the potential for higher production and plant expansion. He said, "The VIBROSCREEN screener could handle three times the 2 ton/hour volume that we were feeding it. It identified processes we needed to speed up."

Product Goes into Rubber Parts

The recycler manufactures various sizes of crumb rubber by granulating scrap passenger car tires after removing the metal bead wire and fiber reinforcing cords. Bulk density of the free flowing, granular particles is 30-lb/cu ft, angle of repose is 70°, and moisture content is less than 1%. The product, sold in 2000-pound bulk bags, goes into the manufacture of molded and extruded rubber parts such as mats, hoses, tiles and asphalt crack sealant. The company boasts that its crumb rubber is free of contaminants such as rocks, steel, fiber and moisture.


Removes all Contaminants

In the revised process, the original two 4x10 screens separated the 6-10 mesh granules. The under-10-mesh particles were cleaned via a filter/receiver and an air lock before a magnet removed ferrous metal particles. After the granules passed through another air lock, a gravity table took out sand and fiber particles. A bucket elevator lifted the rubber particles for screening through the 60 in. Kason circular vibratory separator mounted on a structural steel platform. Via gravity discharge, three classifications of particles filled 2000-lb bags.

The VIBROSCREEN circular vibratory screener is equipped with one imbalanced-weight gyratory motor positioned beneath the screening chamber. The motor imparts multi-plane inertial vibration to two spring-mounted screening decks, causing oversize particles to vibrate across the screen surface in controlled pathways to the screen periphery where they are discharged. Screening efficiency improves by forcing material to pass over a maximum amount of screen surface. Undersized particles pass rapidly through the screen.

Each screen is equipped with a feed tray to redirect the undersize particles to the center of the screen beneath. The top deck, with a 10-mesh screen, discharges particles between 6 and 10-mesh size. The second deck, with a 20-mesh screen, separates particles from 10 to 20-mesh size. Particles smaller than 20-mesh exit through the bottom frame discharge.


Opportunities for Expansion

The recycler selected the Kason circular vibratory separator based on published performance, price and factory support. The owner also was impressed with the separator's results in another rubber industry application. The unit was engineered and sold by Kason's Canadian sister company Separator Engineering Ltd., Scarborough, Ont.

"Apart from regular lubrication and inspection, we did not spent a penny on maintenance," he said.

Performance of the circular vibratory separator opened opportunities for the recycler to expand its plant and production and integrate another processing line.

One-Pass Classification Of Rubber Granules Boosts Output By 30 Percent
 

Kason VIBROSCREEN circular vibratory separator eliminated double handling in classifying rubber granules. Three classifications of particles, by gravity discharge, filled 2000-lb bulk bags. Also on platform are different mesh size screens and top deck of separator.


One-Pass Classification Of Rubber Granules Boosts Output By 30 Percent
 

Crumb rubber particles were conveyed and elevated from gravity table (left foreground) to Kason VIBROSCREEN circular vibratory separator, which classified particles and filled 2000-lb bulk bags by gravity discharge.

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