CASE STUDY No. 9718
KEY WORDS COAL COMBUSTION BYPRODUCTS, GYPSUM WALLBOARD
Indianapolis Power & Light Company
1230 W. Morris Street
Indianapolis, IN 46221
Contact: Terry Hogan, Manager Environmental Affairs.
Tel: 317-261-8635. Fax: 317-630-5796.
Summary
Instead of landfilling the sludge produced by air pollution control devices at a coal-fired generating plant, the company converts the material into gypsum wallboard, avoiding disposal of up to 300,000 tons of material annually.
Action
IPL was required to install sulfur dioxide removal systems on coal fired boilers constructed in the late 1970s and mid 1980s. The flue gas desulfurization (FGD) systems, or "scrubbers," installed on these boilers utilized a limestone sorbant which produced a calcium sulfite scrubber sludge that required stabilization with flyash or quicklime prior to reuse or disposal. The majority of this material had been landfilled because of regulatory barriers concerning reuse. With the advent of the Clean Air Act Amendments of 1990, IPL was required to install additional scrubbers on the two remaining unscrubbed boilers.
The onsite landfill at the Petersburg Generating Station had been nearing capacity from the disposal of coal combustion byproducts produced at the site. With the installation of the additional air pollution control equipment, remaining capacity at the landfill would quickly be used up. IPL determined it would be more cost effective to spend the capital dollars to install an additional FGD system to produce a commercial grade gypsum product rather than build additional landfill capacity.
The new scrubbers came on line in March 1996. Gypsum production was estimated at 250,000 to 300,000 tons a year. Most of the gypsum produced has been utilized by a wallboard plant in a town about 40 miles away. A small amount has been barged to wallboard plants along the southern Mississippi River.
Research completed on synthetic gypsum has demonstrated that it is also a viable substitute for natrual rock gypsum used in agricultural applications to prevent soil erosion. This market is expected to expand as awareness grows within the agricultural community.
Payback
Revenue from the sale of gypsum to wallboard manufacturers is significant but so is transportation cost. A much more important benefit to IPL is avoiding the cost of building additional landfill capacity and disposing of of 300,000 tons of material annually. The company characterized the payback period on its investment as short-term.
Additional benefits
