Coal coprocessing with used oil

Waste oil coprocessing with coal appears to be an alternative to both conventional oil disposal and coal liquefaction using hydrogen donor solvents. Coprocessing experiments carried out in tubing bombs yielded coal conversions of up to 90% at temperatures from 400--450 C, at cold H{sub 2} pressures of 800--1,250 psig, and at reaction times of 15--60 minutes with and without iron-based catalyst. The effect of different coal loadings on conversion and selectivity was also investigated. The highest conversions were obtained for a coal loading on oil of about 20% w/w. The effect of ionic and non-ionic surfactants on coal liquefaction were studied with pure aliphatic compounds such as eicosane and octadecane as well as with mineral oil. A general increase in coal conversion and selectivity was observed with an increase in surfactant concentrations up to a limit for most surfactants. Hydropyrolysis of the used oil also occurs simultaneously, as indicated by the drop in oil viscosity. It was also found that up to 90% ash and 40% sulfur reductions in the oils may be due to metals deposition on to the solid coal residues and gas formation which occur respectively during liquefaction. These findings indicate that a once-through process could bemore » possible if no solvent has to be separated, hydrogenated and recycled to the reactor. this could reduce the equipment and operating costs considerably. The amount of aromatics in the product stream is also greatly reduced as compared to conventional liquefaction, making it environmentally more acceptable.« less