CASE STUDY No. 9610
KEY WORDS COAL-ASH UTILIZATION, CEMENT PRODUCTION
American Electric Power Company, Rockport Plant
Route 2, Box 24A
Rockport, IN 47635
Contact: Carl R. Scaggs, Admin. Asst. Tel: 812-649-9171, ext. 2004. David A. Shipe, Environmental Specialist. Tel: 219-425-2111.
Summary
Instead of landfilling the coal ash produced at an electric power plant, the utility sells it as an ingredient of cement, and for other secondary uses, thus avoiding 95% of previous disposal costs and generating a significant new stream of income for the company.
Action
The AEP Rockport Plant, located near the Ohio River in Southern Indiana, is a 2,600 megawatt, coal-burning facility employing 450 persons. In 1994 the plant produced 373,827 tons of Class C fly ash and 152,000 tons of bottom ash. Before development of the reuse program, virtually all ash was disposed in a 600-acre landfill on company property. Only 24 acres have been used, however, because of the diversion program; and even ash deposited some years ago in the landfill has been reclaimed to meet market demand.
Coal fly ash reacts chemically with portland cement and water to form compounds possessing cementitous properties. The amount of fly ash in typical concrete applications ranges from 15% to 35% by weight of total cementitious material. The ash utilization program at the Rockport Plant is a team effort involving members of the plant's Waste Minimization Committee, home-office engineering and marketing staff, and an ash broker, American Fly Ash.
Thanks to a vigorous marketing program, 96% of the fly ash and all of the bottom ash produced at the Rockport Plant in 1994 was sold or used in construction projects on site. For example, Rockport fly ash was used in the ice rink floor at Kiel Center, home of the St. Louis Blues professional hockey team; in paving projects on Interstate highways 70, 55, and 270 in Missouri; in a runway expansion at Indianapolis International Airport; and in construction of the Metropolitan Nashville (Tennessee) Arena. Other secondary uses of fly ash and bottom ash include the manufacture of Flash Fill, a flowable backfill material that sets like concrete; and the demonstration of the use of fly ash to raise soil pH and to supply soil micronutrients. Bottom ash has been utilized in the leachate layer of landfills and mixed with road salt for snow and ice control.
Payback
In 1992, the company reported net revenues of $755,000 from ash sales and $1,910,000 in avoided landfill costs. Sales of fly ash alone have risen from $500,000 in 1991 to more than $1 million in 1994.
Additional Waste Prevented
The company believes that significant savings accrue when ash is used as a substitute for products that must be mined and transported to produce cement, such as limestone. But it would be very difficult if not impossible to document the savings.
To store fly ash in marketable condition through the winter months, when demand for
cement is low, the company located an inflatable dome that had been used originally to
store grain in Salina, Kansas, but had been disassembled and was in storage. It covers
60,000 square feet and is large enough to store 30,000 tons of fly ash, or about one-tenth
of annual production. The structure cost about $22 per ton to purchase and build, a
fraction of the cost of conventional storage structures. Staff have named this unique
storage building "The Ashtrodome."