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DEVELOPMENT OF A NEW GRAVITY SEDIMENTATION PROCESS FOR DEWATERING FLUE GAS CLEANING WASTES
Citation:
Tarrer, A. DEVELOPMENT OF A NEW GRAVITY SEDIMENTATION PROCESS FOR DEWATERING FLUE GAS CLEANING WASTES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/7-84/084.
Description:
The report gives results of a project to develop and test a novel system for dewatering flue gas cleaning (FGC) wastes at the pilot plant level. In this new system, the clarification and thickening functions are conducted in separate, but interconnected, pieces of equipment. The new system consists of a lamella clarifier and a conventional thickener that is smaller in diameter, but deeper (than the thickener/clarifier typically used to dewater FGC wastes), connected by a recycle stream between the two units to obtain a high degree of flexibility and control of operating conditions. Preliminary economic evaluation of this system indicates potential savings of 10 percent of the total capital costs and 6 percent of annual operating costs for the FGC waste management/disposal system. In pilot testing of this system, a completely new concept in thickener operation, known as the 'bang-bang' operation, evolved in which the thickener underflow rate is set as low as possible without plugging the underflow lines. Periodically, the underflow rate is increased briefly to remove additional solids from the system at the concentration established by the (previously set) low underflow rate. This mode of operation appears to make it possible to maintain the maximum solids concentration in the underflow.