Since January 2005, Dow Electrodeionization modules have provided leak-free, reliable performance at the Madison Gas and Electric Cogeneration power plant in Madison, Wis. Located on the University of Wisconsin-Madison campus, the MGE facility is one of the cleanest burning Cogeneration plants in the U.S. The facility can produce 150 MW of electricity, 20,000 tons of chilled water and 500,000 lb/hour of steam.
The Dow EDI units at the plant were sized to produce 360 gpm (2 x 180 gpm) on a continuous basis for high-purity steam make-up water. Contract design criteria for the plant specified a minimum resistivity ≥ 15 MΩ-cm. Since start-up, the Dow EDI performance has exceeded requirements, producing product water quality averaging 17.7 MΩ-cm water with no need for module cleanings or maintenance shutdowns.
One key factor stimulating the selection of Dow EDI at this site was the desire to adopt a water treatment approach that used fewer chemicals. A main benefit of the electrodeionization process is eliminating the need for on-site bulk storage of concentrated acid and caustic regenerants, and associated operator exposure. Also, no hazardous waste stream is generated by this technology.
In combination with RO, EDI provides a continuous, chemical-free system. Since the incoming West Campus Cogeneration Facility municipal water has sporadically high ingress of dissolved solid impurities, the primary demineralization system consists of double pass RO, with caustic dosing between the two passes for the boiler makeup water system. Two-pass RO helps protect the EDI system from variable quality feedwater that can end up scaling or fouling EDI modules. With inter-pass caustic injection, higher removal of organics, carbon dioxide, silica and boron can be achieved.
The operation and maintenance of the Dow EDI modules at the MGE plant has become routine, requiring little involvement from plant personnel. The operators at the facility have come to rely on the leak-free operation, exceptional performance and minimal maintenance requirements of the Dow EDI systems.
The MGE boiler feedwater consists of two sources, namely returned steam condensate from UW and boiler makeup water. Condensate plus the makeup water then flows through a deaerator that removes dissolved air from the water, further purifying and reducing its corrosivity to meet 7 parts per billion dissolved oxygen specification.
| -End- |