Oil agglomeration of weakly hydrophobic coals and coal/pyrite mixtures

Fine particle suspensions of various materials in water were agglomerated with heptane in a modified blender to determine the agglomeration characteristics of the solids. The materials included Upper Freeport coal, oxidized Upper Freeport coal, two batches of Illinois No. 6 coal, graphite, and iron pyrite. The response of these materials to oil agglomeration varied over a wide range and seemed to depend on their relative hydrophobicity. Treating the weakly hydrophobic materials with traces of sodium oleate greatly enhanced their response to oil agglomeration. The separation of mixtures of pyrite and various carbonaceous materials by selective agglomeration with heptane was also studied. While an excellent separation of graphite and pyrite was achieved, the separation of coal and pyrite proved elusive. Disciplines Catalysis and Reaction Engineering | Other Chemical Engineering | Petroleum Engineering Comments Reprinted (adapted) with permission from Energy Fuels, 1988, 2 (2), pp 145–150. Copyright 1988 American Chemical Society. This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/cbe_pubs/268 Energy & Fuels 1988, 2, 145-150 145 Table III. Effect of Particle Size on Coal Surface/Interfacial Properties (ash= 28.6%, (ash= 23.5%, SP = 1.52) SP = 1.45) -28 + -100 -28 -200 par am 100 mesh mesh mesh mesh 9 in liquid C02, deg 140 149 136 145 surface area, m2 / g of coal 87 98 95 109 g of C02/g of coal at P = P0 0.057 0.065 0.069 0.082 g of C02/100 m2 of coal at P 0.066 0.063 0.073 0.075 = Po 1r,., Njm 0.0904 0.0889 0.0852 0.0816 surface areas, and adsorption isotherms for these samples were experimentally determined. The results (Table III) show that the measured contact angles in the large particle size fractions (-28 + 100 mesh and -28 mesh) are slightly smaller than those in the small particle size fractions (-100 mesh and -200 mesh). This may be attributed to the apparent differences in surface condition of the compressed coal pellet samples formed with large and small particle sizes. Hence the measured contact angle for the large particle size coal tends to underestimate the true contact angle. This phenomenon was also observed by Murata.15 Considering the small differences in measured contact angles between these two size fractions of each group, it can be said that the particle size has only a minor effect on the contact angle. As expected, the surface area is smaller for the large size fraction than the small size fraction of coal samples. It is also found that coal with the smaller size fraction adsorbed more C02 on a unit weight basis. The increase in (15) Murata, T. Fuel 1981, 60, 744-746. the external surface area for the finer coal particles is known to be the teason for the increased amount of C02 adsorption on a unit weight bases. However, when expressed on a unit surface area basis, the same amount of adsorption is observed. Similarly, the film pressure of each size fraction of these coal samples was compared, and little difference between the two size fractions was found for both of the tested groups. These results can be explained by the fact that when the coal particles are ground into smaller sizes, the increase in the total surface area is mostly due to the increase in the external surface area (assuming very few dead pores in the original coal particles), while the internal micropore surface area is the same for both the larger and smaller sizes of coal particles.