THE EFFECT OF SURFACTANTS ON DISAGGREGATION OF COAL-WATER SLURRY PARTICLES DURING COMBUSTION

Changes in the particle size distribution of coal-water slurry droplets during water vaporization and early stages of combustion are investigated. Comparative studies for two hva bituminous coal slurries, one with and one without dispersants (surfactants), are conducted at high temperature (1900 K) in a laminar flow reactor during thc first 20 ms of residence time in an oxidizing (4 mol.% O2) environment. Results show that the initial droplet size distributions, before significant vaporization of water, are similar for both types of fuels. Slurries containing no surfactant disaggregate, producing significantly higher number densities of small particles (0.4-10-mu-m) than the slurry containing surfactant. Mass mean diameters of the slurry with no surfactant are 1.5-2.0 times smaller than those of the slurry with surfactant after slurry disaggregation. Disaggregation of slurry particles, if reproducible in large-scale systems, will have a significant positive impact on the combustion behavior of slurry-fired engines and boilers.