Effect of solvent hydrotreatment on product yield in the coal liquefaction process

Effects of solvent hydrotreatment on product yields in the NEDOL coal liquefaction process were examined based on the data obtained by a 150 t/d pilot plant operation. When the hydrogen gas consumption in the liquefaction stage was kept constant at 4.7 wt.%-daf(wt.% on the basis of dry and ash-free coal), the yield of the oil fraction increased from 51.0 to 54.9 wt.%-daf with an increase in the hydrogen gas consumption from 0.7 to 1.3 wt.%-daf in the hydrotreatment stage. In the hydrotreatment stage, about 30% of the hydrogen consumed was utilized for enrichment of naphthenic hydrogen content in the solvent, and the rest was used for both the removal of nitrogen from the solvent and the production of the light oil fraction. In the liquefaction stage, the hydrogen donated from the solvent was more efficiently utilized than the gaseous hydrogen for the production of the oil fraction. Under the conditions that the total hydrogen consumption in the hydrotreatment and liquefaction stages was kept constant, the yield of oil fraction and the nitrogen content in oil fraction were higher when the hydrogen consumption in the liquefaction stage increased with concomitant decrease in the hydrotreatment stage. (C) 2000 Elsevier Science B.V. All rights reserved.