THERMAL EVOLUTION OF A SHREDDED TIRE MONOFILL

Two 100x100 ft sites next to each other on the top of a shredded tire monofill were selected for the thermal probe measurements. The probes were anchored vertically at 3 ft interval to span the 16 ft thickness. One site is covered with a 6 mil white polyethylene sheets and the other site without. Observation made during July and August, 2005 showed that the temperatures of the covered site were from 30^oF (17^oC) near surface downward to 20^oF(11^oC) at depth higher than the exposed site. In addition, the temperature variation of the covered site could be as high as 35^oF (19^oC) as contrasted to the 9^oF (5^oC) maximum for the exposed site. These evidences indicate that heat is generated within the monofill. The temperature fluctuation at 4 ft depth follows that of the surface probe suggests that heat absorption by tire shreds can also be a factor in internal heating. Compression heating and transferring of surface mechanical energy due to elasticity of tires can also be a factor. The heat can quickly be dissipated if the surface is uncovered.

Oxidation of pyrite and coaly particles in the weekly covering material, and iron wire from tire shreds, can all contribute to the heating process. In a coal oxidation study, approximately 4% of the calorific values, or about 500 Btu/lb, could be lost after 218 days oxidation. Additional time in oxidation does not result in significant loss of calorific value. The heat generated from pyrite oxidation is estimated to be 370 Kcal/mole and iron wire 81.4 Kcal/mole. In the aeration zone of the monofill, both air and water are available for the oxidation.