Scrap tires incineration

E. Goodrich have burned a 10% tire chip mixture with coal (11—13). Tire grinding size reduction problems and deflvery costs have stymied projects based on combined tire and coal fuel. Transportation of tire scrap can cost 0.05 /kg, exclusive of grinding costs, thus tire-fired boilers are limited to areas with sample scrap tire suppHes, eg, large cities or tire manufacturers. The cost of burning one metric ton of tires per hour in an incinerator was ca 0.20—0.40 per tire in 1974, which increased to 0.35—0.70 per tire in 1987 (14). 

An integrated solution is needed to the waste tire problem. Both government and industry need to work together to develop markets for scrap tires and to ensure proper disposal of those tires that are not recycled and are not incinerated for their energy value. In the next two sections of this chapter, options for mitigating the scrap tire problem are discussed. 

However, it is believed that incineration of strap tires is not the most desirable long-run approach when the total natural resource situation is considered. Scrap tires, a discarded resource rich in hydrocarbons, should be returned to the production cycle as useful materials, such as reclaim, reinforcing carbon black, and carbon compounds that could be chemical feed stocks. This last approach would conserve gas and oil reserves. 

Each of the two incinerators has the capacity to burn 100 tons of waste per day and produce approximately 20,000 pounds per hour of steam for use in the tire manufacturing process. Twenty-five per cent of the load to the incinerator is whole tires and rubber scraps. The remainder consists of paper, wood, and miscellaneous solid waste. The percentage of rubber does not exceed 25 percent so that the flue gas can stay within the opacity limit. Even though only one quarter of the weight of the load is tires, the tires account for 80 percent of the Btu consumed by the furnaces. 

The use of PMDI as a binder for foimdry cores, rubber waste products, and solid rocket fuel are also known. Isocyanate-terminated prepolymers, often prepared from TDI or MDI with polyether polyols are also used as binders for composite products that require elastomeric properties. Athletic surfaces are sometimes prepared from groimd rubber tire scrap bonded with isocyanate-based prepolymers. Similarly, flexible polyurethane foam scrap is bonded with isocyanate prepolymers to form rebonded foam usefiil as carpet imderlay. Solidification of incineration ashes with PMDI-based binder systems is another waste disposal application. In this manner hazardous waste materials imdergo chemical fixation and detoxification. 

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