EFFECTS OF PH AND IONIC-STRENGTH ON KINETICS OF OIL AGGLOMERATION OF FINE COAL

Batch agglomeration tests were conducted with a specially designed mixing unit to determine the effects of the pH and ionic strength of the aqueous medium in which coal particles were suspended on the oil agglomeration kinetics of the particles. Highly hydrophobic, No. 2 Gas Seam coal from West Virginia and moderately hydrophobic, Colchester Seam coal from Illinois were agglomerated with hexadecane in a series of tests in which oil dosage was varied as well as the pH and salt concentration of the aqueous medium. Changes in the aqueous medium had the greatest effect on the rate of agglomeration when the oil dosage was a minimum. The rate of agglomeration was a maximum at pH 9 for No. 2 Gas coal and at pH 4 for Colchester coal. Between pH 9 and 12, the rate of agglomeration of Colchester coal decreased markedly for any oil dosage, whereas the rate of agglomeration of No. 2 Gas coal declined less noticeably except al the lowest oil dosage. The rate of agglomeration of both coals increased when the ionic strength was increased. However, the effect was much greater on No. 2 Gas coal than on Colchester coal.