Low-Cost Mercury Sorbents Derived From Waste Tires

This project addresses two environmental problems: (1) removal and recovery of mercury from combustion/incineration flue gas with concurrent control of SO2 and NOx; and (2) reprocessing of waste tires into value-added products. Coal combustion and incineration of municipal and hazardous wastes result in air pollution due to emissions of trace amounts of heavy metals. Because of the high toxicity of these species, their emissions are or will be regulated. The high volatility of mercury makes control of this metal particularly difficult. Scrap tires present formidable disposal problems, as they are known to be immune to biological degradation. Landfilling of the 280 million tires that are generated each year in the United States is becoming an unacceptable solution. In addition to the continuous flow of waste tires, there are approximately 2¿3 billion tires already stored in piles throughout the country; illegal dumping also is becoming a problem. The tires take up large amounts of valuable landfill space, provide breeding sites for mosquitoes and rodents, and present fire and health hazards. The proposed approach is based on mercury adsorption on low-cost, sulfur-rich activated carbons derived from scrap tires. The sulfur added to tire rubber in the process of vulcanization makes the tire-derived sorbents particularly effective in mercury removal due to the high chemical affinity between mercury and sulfur. Two implementations of the process are envisaged: (1) sorbent injection into the flue-gas duct (near-term application); and (2) a patented regenerative scheme (long-term application). The overall objective of the Phase I and II projects is to develop a novel and effective technology for mercury control using sorbents derived from waste tires. The specific objective of the Phase I project is to demonstrate the superior mercury-sorption performance of low-cost activated carbons derived from waste tires under simulated industrial conditions. Advanced Fuel Research, Inc. will accomplish this via three tasks: (1) sorbent development (prepare several sorbents with different surface areas, pore-size distributions, and sulfur contents); (2) sorbent testing (determine the effects of temperature, gas composition, the presence of water vapor, sorbent pore-size distribution, sorbent history, etc.); and (3) process assessment.