INVESTIGATION OF ATMOSPHERIC EMISSIONS FROM CO-COMBUSTION OF TIRE AND COAL

Scrap tires are a large waste problem in the United States. Nearly 300 million car, truck, bus, and airplane tires are discarded in the U.S. every year. Recovering energy from scrap tires through combustion is becoming a popular way to manage this waste problem. Many industrial and utility companies are choosing to combust tires as a supplementary fuel due to the higher energy content and lower price of tire-derived fuel (TDF) relative to coal. However, the co-combustion of tire with coal may significantly alter the emissions of the combustion facility.

The Purdue University Wade Utility Plant conducted a test burn to compare the atmospheric emissions and solid waste produced by the facility under two fuel conditions: pure coal and a 95 wt% pure coal + 5 wt% TDF. The results of this study show that the atmospheric emissions of most trace metals increase when TDF is co-combusted with coal. Zn emission increased dramatically to 160 times the pure coal emission rate when the TDF + coal fuel mixture was combusted. The Cd emissions when TDF was combusted with coal are approximately 5 times the emission rate for pure coal combustion. Hg emissions remained the same for both fuel types. Fluoride, HCl, and NOx emissions also increased when TDF was combusted. However, SO2, CO, particulate emissions, and total hydrocarbons (THC) emissions were not significantly affected by the addition of TDF to the fuel. Studying the atmospheric emissions of TDF and coal co-combustion will help to identify and solve possible risks to the environment posed by this method of scrap tire disposal.