FINAL TECHNICAL REPORT

September 1, 1997, through August 31, 1998

Project Title: A FIELD DEMONSTRATION OF PONDED FLY ASH AND SCRUBBER RESIDUE IN FLOWABLE FILLS

ICCI Project Number: 97-1/3.1C-1

Principal Investigator: Dr. B. C. Paul, Southern Illinois University at Carbondale

Other Investigators: Dr. Y. P. Chugh, Mr. S. Chaturvedula; Southern Illinois University at Carbondale

Project Manager: Dr. Dan Banerjee, ICCI

ABSTRACT

Electric utilities that elect to scrub for control of SO2 emissions face solid byproduct volumes about 4 times greater than unscrubbed stations. Costs of handling these materials can amount to a surcharge of about $1.50 to $5.00/ton of coal. A cooperative project has been undertaken with an Illinois utility having a scrubbed power station to develop more economically handlable and potentially beneficial paste fill mixes from their fly ash and scrubber residue. Mixes have been developed with mild soil like strengths to enhance potential for revegetation. The mixes are pumpable as a paste without expensive dewatering system additions at the power plant. The pastes do not have problems with bleed water and inhibit the leaching of boron. Equipment for producing and handling the pastes have been identified and the components tested. Configurations have been developed that should reduce materials rehandling at the power plant and consequently save money.

Page(s) 3-21 contain proprietary information.

EXECUTIVE SUMMARY

The primary intent of the present proposal is to produce a fast setting variable strength paste fill from a combination of sulfite rich FGD sludge, and ponded F type fly ash from the combustion of Illinois coal, in order to provide electric utilities with more cost effective methods of using and storing the larger volumes of byproduct material that result for flue gas desulfurization. The project will aid the economy of Illinois by helping utility companies to lower the bus bar cost of electricity while using Illinois coal and employing Illinois coal miners. When utilities can store or utilize the scrubber and fly ash products of Illinois coal consumption onsite, the cost amounts to $1.50/ton of coal. When off-site landfilling is used that cost becomes $5/ton or more.

Scrubber byproduct and fly ash from Duck Creek Station of CILCO were mixed in various ratios and with various activators in order to produce structural materials that could be pumped and placed to provide rolling topographic features that blend with and can be revegetated to match the surrounding landscape. Pumpable pastes should be more economic to handle than the current system of excavation, trucking, stacking, and compacting. The blended pastes should also inhibit the leachability of boron reducing build-up in ponds and potential release into the surrounding ground and surface waters.

Mix ranges found suitable would allow CILCO to operate extracting material from previous years from pond #2 and pump them to topographic reclamation features on pond #1 as part of the pond #1 closure program. Other mixes were developed that are compatible with addition of a dry fly ash handling system that would market a portion of the current ash production. Marketing of all the fly ash production is likely to be problematic in handling only scrubber byproduct.

Mixes were also developed for handling by truck or belt conveyor. These mixes were intended to have significantly greater strength and durability against the action of weather. Such mixes would have additives and would require deviations in materials ratio from the production ratio.

Tests have been conducted to determine the type of feeding, mixing and pumping equipment that would be needed to handle the CILCO material on a large scale. A likely equipment configuration was determined and components were tested. The equipment can be coupled to 4 or 5 different materials handling scenarios for removal of the byproducts from the power plant. The configurations should significantly reduce rehandling and consequential costs over the present system.

The remainder of this report contains proprietary information and is not available for distribution except to the sponsor(s) of this project.