Characteristics of alcohol-coal-water slurries spraying

Abstract

The aim of this work is to substantiate the efficiency of ethyl or isoamyl alcohol application as the third component of coal-water fuels based on the results of experimental study of coaxial spraying. Studies of alcohols influence on spraying characteristics of coal-water fuels can rarely be found in the literature. Instantaneous fields of fuel droplets velocities in several cross-sections of the jet were determined using Particle Image Velocimetry method. Interferometric Particle Imaging method was used to determine droplets distribution by size in the jet of sprayed coal-water fuel. It was experimentally established that substitution of water (no more than 3 % by weight) in the composition of coal-water slurry by fairly typical alcohols leads to decrease in droplet velocities of alcohol-coal-water slurries in comparison with conventional coal-water fuel by 15-18 %. Concentration of sufficiently small fuel droplets (up to 200 microns) increases by 13.4±0.2 % and by 6.6±0.2 % during atomization of alcohol-coal-water slurries with addition of ethyl and isoamyl alcohol, respectively. Introduction of no more than 5 % by weight of the studied alcohols into the coal-water slurry will reduce the cost of fuel by 15-73 % in comparison with fuel oil. Influence of small additives of ethyl and isoamyl alcohol in the composition of coal-water fuel on spraying characteristics proves the possibility of efficient application of such three-component slurries in thermal power engineering. The results obtained are of practical significance, since they illustrate the possibility of reducing the ignition delay time for droplets of alcohol-coal-water slurries after they are sprayed in the furnaces of boiler units.