Non-isothermal liquefaction of liptobiolith coal in supercritical water flow and effect of zinc additives

The liquefaction of liptobiolith coal in water vapor and supercritical water (SCW) flow at uniform increase in temperature from 300 up to 470 degrees C and in SCW flow at 400 degrees C (30 MPa) with addition of zinc shavings to coal has been investigated. Temperature dependences of the yield of liquid and volatile products and kinetic parameters of the process have been obtained. The yields of oil, resin, asphaltene and volatile products in relation to the coal organic matter (COM) are 23.2, 16.1, 5.1 and 14.1%, respectively. CO2, CO, H2S and C-1-C-4 alkanes prevail in the composition of volatile products. The generation of oil, resin and asphaltene are found to have occurred in terms of the simultaneous chemical reactions of cleavage of the COM aliphatic C-C bonds, while the volatile products result from the consecutive transformations of the COM components in the bulk and SCW solution. Participation of H2O molecules in thermochemical transformations of COM leads to increase in the oxygen amount in the conversion products and residue by 13.2%. Hydrogen and heat evolution during zinc oxidation by SCW provides for the hydrogenation of COM in situ. Addition of zinc to coal results in increase in the volatile products yield up to 48.6% and decrease in the conversion residue yield up to 20.8%. Under these conditions the yield of resin does not change, while the yields of oil and asphaltene decrease up to 21.2 and 2.5%, respectively. Based on the sulfur balance it is revealed that approximate to 40% of sulfur atoms pass into ZnS owing to the reactions of H2S with Zn and ZnO resulting in the removal of H2S from the volatile conversion products. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.