This project focuses on the creditable demonstration of large volume utilization options for markets that potentially can absorb million of tons of gasification slag. Quantities of coal gasification slag will increase in the future due to this technology's inherent efficiency and potential for environmental cleanliness. Gasification slag is a heterogeneous material comprised of a siliceous vitreous phase (a.k.a. frit) mixed with a carbon char in varying proportions. The two materials are found to be simple mixtures, not compounds, which can be physically separated and concentrated into more usable carbon rich and vitreous frit fractions. This has already been demonstrated at TECO's Polk station in Florida, by Charah Environmental. "Zero emission" coal gasification, however, requires that all of the by-product slag be utilized.

In the current project, approximately 100 tons of slag from both the Polk station and Eastman's Kingsport, Tennessee gasifier will be classified into carbon-rich and vitreous fractions, using the installed equipment at Polk and a truck-mounted field test rig at the Kingsport plant. Applications for the carbonaceous char to be investigated include: recycle fuel to the gasifier, cement kiln fuel and adsorbent materials. The siliceous vitreous frit will be investigated as raw materials for kiln feed, pozzolanic concrete additive, roofing granules or blasting grit. The recycle fuel experiments will be conducted at Kingsport and will include operational trials. The assessments of the materials for use in cement manufacturing will be conducted by CEMEX at their facilities in Tennessee and Florida and will, if feasible, include full scale kiln tests. The remainder of the testing will be conducted at the CAER laboratory in Lexington, KY. All of the slag materials and appropriate slag products will be subjected to leaching assessments using multiple procedures to ensure the environmental safety of the materials and their uses.

The primary benefit of this project is that it is investigating important, large volume uses for the slag, using relatively large tonnages of materials under realistic test conditions. This will provide a very high level of confidence in the potential for the gasifier slag's marketability and environmental safety. This, in turn, will help to hasten the adoption of gasification technology, a cleaner and more efficient way to use coal.

The research team is headed by the University of Kentucky Center for Applied Energy Research, which has been conducting research in coal combustion by-product utilization for over 25 years. The team also includes: Eastman Chemical Co. and Tampa Electric Co. (TECO), which operate major gasification installations; Charah Environmental Inc., designers and operators of the first successful gasification ash beneficiation plant; and CEMEX Inc., the third largest cement producer in the world and a major consumer of coal combustion by-products.