Tens of millions of tires are discarded every year by countries all over the world. Disposal of these tires has become a task that is challenging, as rubber, the main constituent, is not biodegradable and has a long life. Traditionally, tires have been disposed of by dumping in landfills, but they then make perfect breeding grounds for vermin, snakes, and mosquitos. Fires in these dumps can rage for months and release toxic fumes. Tires have large volumes and a lot of voids and thus occupy a lot of space in landfills. Pyrolysis equipment is the thermal decomposition of tires in the absence of oxygen.
In most rubber pyrolysis plants tire chips act as the primary feedstock. There are also some other waste rubber products. The material is heated to temperatures that range between 450 and 700 degrees Centigrade in the absence of oxygen. This heated rubber decomposes into fuel, synthetic gas, steel wire, and carbon black. Carbon black is the solid material that remains after the other materials are released.
The fuel oil that is derived from waste rubber pyrolysis plant is widely used in industries. Use is made of this oil in boiler heating, cement factory kilns, steel and other factories and generators that use heavy oil. The steel wire is removed from the final residue with magnets and can be sold to recycling mills that will remelt the steel and recycle it into other products. The char, which is mainly carbon, can be made into pellets that can be used as coal for burning or heating or used for refining and made into other products, like carbon black.
In the pyrolysis method for the recycling of tires, shredded tires are heated in a reactor in an atmosphere that is free of oxygen. The rubber gets softened, and the polymers in it disintegrate and vaporize and leave the reactor as vapor. The vapor can be burned directly, and often part of the vapor is used for the heating process itself. The unburnt part of the vapor is then sent to condensers that covert it into bio-oil. Molecules that do not condense remains as a gas and can be burned as fuel in the plant itself. The other minerals that made for 40 percent of the weight of the tire remain as solid or char, which can be further processed. The process of pyrolysis emits no waste and is a relatively clean operation.
Temperatures and heating rates play a large part in the decomposition of tires that convert the material that can be recycled. At 450 degrees, the product is liquid, but at temperatures above 700 degrees, the product is synthetic gas as liquids go through a process of further cracking. Pyrolysis has been the highly accepted method for recycling tires compared to the other methods like ambient mechanical grinding or cryogenic grinding. The byproducts from pyrolysis oils, synthetic gas, and carbon black are all useful products that find use in industries in various forms. Hence, tyre recycling equipment South Africa is very popular.
A rubber pyrolysis plant produces no smell or smoke and is thus an eminently favorable environmental solution. Scrap tires get converted into useful products and are no more a problem for disposal.