Production and disposal of wastes from dry and wet flue-gas cleaning systems

The design of a flue-gas cleaning system for the removal of particulates and sulfur dioxide contaminants must take into account many factors for there to be successful operation and no secondary environmental impacts. One of the factors which must be taken into account is the production of wastes and the procedures to be put into place for proper disposal. For many years, Argonne has had a high-sulfur dry scrubbing system in operation as the means of emissions control from its largest coal-fired boiler. During this period thousands of tons of a dry powdery waste have been produced and landfilled without any adverse environmental effects. This paper reviews the theory of operation of a dry scrubbing system, and briefly details the performance of the Argonne system over several years. Among the performance details given are the results of an experimental program utilizing a high-sulfur (s>4.2%) coal, done in co-operation with the Consol Coal Company, and the findings from a study on the leachate, toxicity, and disposal of the dry wastes. The experimental programs, to date, have shown that a dry scrubbing system can technically and economically remove sulfur dioxide and particulates from flue gas produced from the combustion of high-sulfur coal. In addition, mixtures of dry scrubber wastes and fly ash have been subjected to the standard U.S. Environmental Protection Agency toxicity tests. The results of these tests indicate that while the ash composition of the coal will have a bearing upon test results, for the most part mixtures of this waste and coal fly ash can be declared non-hazardous.