Recycling of used tires and waste

Recently, a novel continuous process has been developed for devulcanization of rubbers as a suitable way to recycle used tires and waste rubbers [83-119]. This technology is based on the use of high-power ultrasounds. The ultrasonic waves of certain levels, in the presence of pressure and heat, can quickly break up the three-dimensional network in crosslinked rubber. The process of ultrasonic devulcanization is very fast, simple, efficient, and solvent and chemical free. Devulcanization occurs at the order of a second and may... 

Tire dealers need ready access to information on reputable or licensed haulers, recyclers, or disposers of waste tires. They also need information on companies that sell used tires and that retread tires. Information on the location of large tire piles is helpful to entrepreneurs seeking to process these tires for eventual recycling or energy recovery. 

A considerable number of reports regarding the formation of compounds that may represent a health hazard are related to the formation of polycyclic aromatic hydrocarbons (PAHs) during industrial pyrolysis processes (recycling of waste, incineration, etc.). This interest is particularly geared toward the study of polyolefins pyrolysis and synthetic and natural rubber pyrolysis. The formation of PAHs during polyethylene pyrolysis has been reported frequently in literature [6, 12] and is further discussed in Section 6.1. The formation of PAHs during tire pyrolysis is also of considerable concern. The concentrations of some components in the oils generated from the pyrolysis of used tires as a function of temperature are indicated in Table 5.3 1 [13]. 

The process is being used on a commercial scale on Hokkaido, Japan, but appears to be uneconomical in the United States. (Mixtures of scrap tires with waste plastics have also been pyrolyzed.247) It appears to be cheaper in the United States to burn the tires for energy at lime kilns, paper mills, and such.248 The sulfur in the tires must be trapped by the lime or by other means. The combustion conditions must be such that the usual thick black smoke of burning rubber is not present. Recycling the rubber in the tires to more items of rubber would be preferable to just burning them as fuel. The real key to fewer tires to recycle is to devise better land use systems that require fewer automobiles (see Chap. 15). 

Besides all the gaseous and liquid wastes of transportation that result from energy use, and the loss of natural environment to roadv ays, there is also the solid-waste problem of disposal— vehicles and components such as tires and batteries. Responding to the growing disposal problem, many manufacturers are building automobiles that contain far more recyclable parts. 

N. Mandal, S. Dasgupta, and R. Mukhopadhyay, Regeneration of carbon black from waste automobile tires and its use in carcass compound. Progress in Rubber, Plastics and Recycling Technology, 21(1), 55, 2005. 

According to E.W.M.C. International Inc., the Emery microwave process has been used commercially to recycle rubber tires and process medical waste. Research and development is currently being conducted on the application of the technology to treat contaminated media. All information is from the vendor and has not been independently verified. 

Another means to aid recycling of tires and the utilization of tires as fuel is to expand the use of existing solid waste exchanges to include tires. Classified advertisements in magazines and newsletters can help those who have sources of... 

A pyrolysis system has been developed to recover useful material from scrap tires. An actual plant was constructed in 1979 The plant will be on a trial for a year to demonstrate that the equipment of the plant satisfies the test specifications and that the recovered carbon black has the quality demanded by the rubber industry. After passing one year tests, it will be put into commercial operation. This project is a full scale recycling for scrap tires supported by public agencies which also supported the pulverizing plant in Osaka. It is expected that the completion of the project will open a new course for recycling and disposal of waste. 

A growing volume of waste materials, especially vulcanized rubbers and crosslinked polymers are proving difficult to recycle. As an alternative to their disposal in landfills, there have been many attempts to grind these materials and use the products as a substitute for fillers in composite materials. Other non-plastic materials such as glass, paper, natural fibrous materials, and fly ash are also used for filler replacement. There is extensive literature on the use of ground tires as filler replacements. This is a specialized topic with only a minor relationship to fillers. 

Tlie first approach may involve cleaner synthesis processes, improved technology, recycling of residues, improved use of catalysts, and generally, every technique integrated into tire process tliat leads to less waste whereas the second one is an end-of-pipe treatment of tire waste tliat is inevitably produced by a chemical process. Botli approaches have to be combined so tliat oru releases into tlie eiivuoiiment are as minimal and haiiiiless as possible. 

Another application of the injection system consists of recycling old and waste rubber. The reactive mixing of crumb rubber with a melted polymer represents an innovative way of recycling these waste rubbers [6]. Some thermoplastic elastomer may contain up to 60% recycled rubber derived from used vehicle tires, and thus through the reactive injection system the rubber scrap is revulcanized [7]. 

In search for a more economical process for recycling used tires, the ultrasonic devulcanization technology was further investigated to develop a feasible process to minimize the stockpiles of waste tires. This process induces the cleavage of the chemical networks through the combination of ultrasonic and chemical devulcanization (Kim et al., 2003). According to authors, the products from devulcanization of tires are carbon black and extended oil that can be used in many applications. A claim was also made that the technology can separate sulfur. 

Fig. 8 Waste volume and recycling of tires from used vehicles [25, 26]...

A number of methods [11,13-17] have been applied in an attempt to solve the problem and to find more effective ways of tire rubber recycling and waste rubber utilization. These methods include retreading, reclaiming, grinding, pulverization, microwave and ultrasonic processes, pyrolysis, and incineration. Processes for utilization of recycled rubber are also being developed, including the use of reclaimed rubber to manufacture rubber products and thermoplastic-rubber blends and the use of GRT to modify asphalt and cement. 

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