Crumb rubber, produced from recycled scrap tires, is an interesting product with an increasing variety of uses. Fine-grind crumb rubber, including the powder form, is used as an input material for the manufacture of molded products and in the production of paving-grade asphalt for roads and driveways. Uses for crumb rubber consisting of larger particle sizes includes safety and cushioning surfaces for playgrounds and fitness facilities, horse arenas, and bike, walking and jogging paths. Crumb rubber of larger particle sizes may also have uses in soil amendment, as a mulch, and as a filler and top-dressing for artificial turf surfaces. When a binding agent is added, crumb rubber may also be used as a base material in the construction of sports surfaces, including running tracks, race tracks, and sports fields.
Producing Crumb Rubber
Generally, crumb rubber is produced by reducing scrap tires down to sizes ranging from 3/8” to 40 mesh particles and removing 99 percent or more of the steel and fabric from the scrap tires. There are several processes for manufacturing crumb rubber. Two of the most common are ambient processing and cryogenic processing. A third technology, known as the wet grind or wet milling process, is also widely used to produce fine mesh crumb rubber whose particles range from 40 mesh to 200 mesh in size.
Using the parts from shredded tires, crumb rubber is usually produced using one of two processes: ambient processing or cryogenic processing. Ambient processing is a multi-step process carried out at room temperature using granulators or crackermills to grind the rubber feedstock to suitable size. Cryogenic processing uses liquid nitrogen or other cryogens to freeze the rubber chips and particles from recycled tires. The frozen particles are then ground in a hammermill to reduce their size. Further size reduction is achieved through a secondary grinding stage.
Ambient and cryogenic processing produces crumb rubber consisting of particles ranging in size from ¼” to 40 mesh. To produce crumb rubber with particle sizes of less than 40 mesh, wet grinding (or wet milling) is commonly used. This processing method results in the production of crumb rubber whose particle sizes range from 40 to more than 200 mesh.
Bucket Elevators & Bulk Bag Handlers for Crumb Rubber Production
Bucket elevators and bulk bag handlers have several uses in the crumb rubber manufacturing process. These include the following:
• Emptying feedstock supplied in bulk bags from tire recyclers and re-treaders. Some crumb rubber manufacturers receive all or a portion of their feedstock bags shipped from tire recyclers and re-treaders. Bulk bag dischargers can be used to empty the bags and ready the feedstock for conveying into the manufacturing process.
• Conveying feedstock to granulators, crackermills, or cryogenic freezing units. The bucket elevator can be used to handle and convey the feedstock to the production equipment used in either ambient, cryogenic or wet milling processing.
• Conveying and filling finished product into bulk bags. In some plants, wet milled fine-mesh crumb rubber particles are shipped to molding customers in pre-measured batch-inclusion bulk bags. Other facilities use bulk bags to ship crumb rubber produced from ambient or cryogenic processing to customers. In both cases, bucket elevators can be used to feed the bulk bag fillers which package the final product.
UniTrak supplies TipTrakTM bucket elevators and Bagstander bulk bag dischargers and fillers that can be used in crumb rubber production. TipTrakTM bucket elevators come in a variety of sizes and configurations to suit almost any processing facility. Bagstander bulk bag dischargers and fillers offer a proven way to safely and efficiently move material into and out of bulk bags. In addition to supplying equipment, UniTrak specializes in engineering systems which bring together the needed equipment in a fully integrated solution. To find out more about the bucket elevators and bulk bag handlers we can supply for crumb rubber production, please contact our sales department.