Effect of preparation techniques on kinetics of oil agglomeration of fine coal

Abstract

The present study was carried out to establish whether the air adsorbed on fresh coal particle surfaces created by dry grinding affects the subsequent agglomeration of an aqueous suspension of the particles with oil. The agglomeration response of coal suspensions which had been degassed by applying a moderate vacuum were compared to those which had not been degassed. Aqueous suspensions of No. 2 Gas Seam coal from Raleigh County, West Virginia, were agglomerated with hexadecane in a closed mixing system. A photometric dispersion analyzer was used to monitor the turbidity of a suspension undergoing agglomeration. The behavior of both wet- and dry-ground samples was established in a series of runs made with oil dosages ranging from 1 to 33 v/w%. The presence of an air film on highly hydrophobic coal particles appeared t increase both the initial rate and final extent of agglomeration by making it easier for the oil to wet the coal particle surface and by reducing the amount of oil required to bond the agglomerates. The effects were particularly pronounced when low oil dosages were used. The presence of an air film was significant only for dry-ground coal. Since different results were achieved with wet-ground coal and dry-ground coal which had been degassed, it does not seem possible to simulate wet grinding by degassing dry-ground coal prior to agglomeration.