Effects of deashing and low-pressure hydrogen on hydrogen transferring liquefaction at reduced solvent/coal ratio

Abstract

Hydrogen transfer liquefaction of an Australian brown coal using tetrahydrofluoranthene (THFL) as the donor solvent was examined by varying the THFL/coal ratio from 3 1 to 1 1 . Solvent/coal ratios of 2 1 and 1.5 1 gave yields of 45% oil and 60% oil plus asphaltene at 450 °C for 10 min under 2.0 MPa of nitrogen pressure, while a decrease in oil yield to 33% was observed at a 1 1 ratio under the same conditions. Extending the reaction time to 20 min increased oil, and oil plus asphaltene yields to 60 and 66%, respectively, at the 2 1 ratio. A reaction time of 30 min produced a marked decrease in both oil and oil plus asphaltene yields. Demineralization of the coal greatly reduced the yield of gas, preasphaltene and residue, and significantly increased the oil yield to 65% at ratios of 2 1 and 1.5 1 at 450 °C and reaction time of 10 min. Low pressure (≈2.0 MPa) of hydrogen increased the oil yield from 46% under nitrogen, to 61% at 1.5 1 and 450 °C for 10 min and from 60% to 66% at 2 1 and 450 °C for 20 min, respectively. A combination of demineralization and low pressure hydrogen provided the best yield of oil plus asphaltene, 84% (oil yield, 66%) at 1.5 1 and 450 °C for 10 min. It is suggested that low pressure hydrogen can act as a substitute in some roles for the donor to a minor extent through its dissociation by its reactivity with radicals derived from the donor or coal molecules.