Particle Sizing in Coal-Water Slurry Sprays Using the Visibility Technique

Measurements of atomized slurry particles were made using a medium-scale atomizer and a laser diagnostic technique. The nominal flow capacity of the atomizer was about 400 Ib/hr of slurry. Particle size was measured using a Particle Sizing Interferometry (PSI) Technique -- commonly referred to as the Visibility Technique. The visibility technique is a single particle measurement technique and, for opaque particles, utilizes light diffracted in the on-axis forward scatter direction. In order to meet the single particle criteria of the technique, a tube was used to shield all but a portion of the measurement volume from slurry particulates. The tube was provided with suction and purge air to draw air and particles through a confined region of the measurement volume. The particle size data indicate that very high air-to-fuel ratios are required to atomize large droplets to the fineness of the coal particles in the spray. However, the upper limit of particle size with the visibility techniques is insufficient to quantitatively characterize the atomized slurry for condition of poor atomization. A reasonable explanation consistent with observations of combustion tests is given.