Combustion studies on concentrated distillery effluents

Abstract

Studies on ignition and combustion of distillery effluent containing solids consisting of 38±2% inorganics and 62±2% of organics (cane sugar derivatives) have been carried out in order to investigate the role of droplet size and ambient temperature in the process of combustion. Experiments were conducted on (1) liquid droplets of effluent having solids concentration 65% and (2) spheres of dried (100% solids) effluent of diameters ranging from 0.5 to 25 mm. These spheres were introduced into a furnace where air temperature ranged from 500 to 1000 °C, and they burned with two distinct regimes of combustion-flaming and glowing. The ignition delay of the 65% concentration effluent increases with diameter as in the case of nonvolatile droplets, while that of dried spheres appears to be independent of size. The ignition delay shows Arrhenius dependence on temperature. The flaming combustion involves a weight loss of 50-80%, depending on ambient temperature, and the flaming time is given by t_f≈d₀² as in the case of liquid fuel droplets and wood spheres. Char glowing involves weight loss of an additional 10-20%, with glowing time behaving as t_c≈d_o² as in the case of wood char, even though the inert content of effluent char is as large as 50% compared to 2-3% in wood char. Char combustion has been modeled, and the results of this model compare well with the experimental results.