Commercialization of Coal-Water Slurries

B&W considers coal-water mixtures (CWMs) to be the most advantageous alternative to oil and gas fuels because the need for on-site coal handling and preparation equipment is excluded and because the use of oil is completely eliminated. In addition, if a low-ash coal is used in the mixture or if the coal is beneficiated, derating of the units will be minimized. Recent work has enabled a number of organizations to prepare pumpable mixtures (slurries) containing approximately 70 percent pulverized coal and 30 percent water. These slurries are stablilized to retard the settling of coal particles and rheological properties are tailored to insure good flow properties by careful variation of grinding processes and additives. Limited scale combustion tests have been performed to date and the most critical question of whether direct-fired un-dewatered slurry can achieve stable combustion without requiring support fuel has been answered positively. Once it had been determined that direct firing was feasible, a CWM commercialization program was initiated and is presently underway.