Scrap tires fuel value

Cement Kilns. The use of scrap tires as a supplemental fuel in cement kilns has had a fairly long history in Germany and Japan, where tires have been used for fuel since the early 1970s. Initially, the scrap tires were purchased by kilns for thek fuel value. As the relative cost of other fuels has... 

With the conversion to a mechanical feed system, they expect to double their tdf feed capacity and run 4 tons per hour. This should result in a considerable fuel cost savings, because they can obtain tdf for about 1 per million Btu, whereas they would otherwise be burning more coal which costs about 2 per million Btu. With the new configuration they could obtain 10 percent of their heating value from tdf, 10 percent from natural gas, and 80 percent from coal. Both their old and new configurations utilize 2-inch by 2-inch pieces of tdf. With the new capacity Arizona Portland could increase its capacity to over 3 million scrap tires per year. In 1990, Arizona Portland utilized approximately 1 million scrap tires (54). 

Overall, burning tires or TDF in cement kilns appear to be an economically satisfactory and environmentally sound way of not only disposing scrap tires, but also reclaiming their fuel value. 

With waste rubber goods, as with nonsegregated plastic wastes, it is possible to simply burn the rubber and regain the considerable fuel value. Whole scrap tires have been burned in cement kilns, for example, to obtain a proportionate saving in the usual oil or gas fuel supply used in these operations. At the extremely high kiln temperatures the combustion is complete and any steel belts or beading are incorporated into the cement klinker without problems. 

In the depolymerized scrap mbber (DSR) experimental process, ground scrap mbber tires produce a carbon black dispersion in oil (35). Initially, aromatic oils are blended with the tire crumb, and the mixture is heated at 250—275°C in an autoclave for 12—24 h. The oil acts as a heat-transfer medium and swelling agent, and the heat and oil cause the mbber to depolymerize. As more DSR is produced and mbber is added, less aromatic oil is needed, and eventually virtually 100% of the oil is replaced by DSR. The DSR reduces thermal oxidation of polymers and increases the tack of uncured mbber (36,37). Depolymerized scrap mbber has a heat value of 40 MJ/kg (17,200 Btu/lb) and is blended with No. 2 fuel oil as fuel extender (38). 

---