COMPARISON OF PRIMARY CONVERSIONS FROM A FLOWING-SOLVENT AND A MINI-BOMB REACTOR - THE EFFECT OF EXTENDED RESIDENCE TIMES OF PRODUCTS IN THE REACTION ZONE

A flowing-solvent (F-S) liquefaction reactor with a continuous solvent sweep through a fixed bed of coal has been developed. In contrast to liquefaction experiments using closed (batch) reactors, where products remain within the reactor for the duration of the experiment, solubilized liquefaction products are continuously swept out of the reaction zone. In this way the possibility of retrogressive reactions is minimized. Results are presented and compared with data obtained in a mini-bomb (M-B) reactor under comparable conditions and using the same sample of Point of Ayr coal. Conversion data indicate that, unlike M-B experiments performed under similar conditions, no increase in solid residue is observed during long residence time-high temperature runs in the F-S reactor. Size-exclusion chromatography shows that products from the F-S reactor increase in molecular weight with increasing reaction time and temperature whereas, due to secondary reactions, products from the M-B reactor are generally observed to decrease in molecular weight as the severity of the reaction conditions is increased.