Liquefaction of coals and maceral concentrates in a flowing-solvent reactor

Abstract

A flowing‐solvent liquefaction reactor with a continuous solvent sweep through a fixed bed of coal has been developed. The reactor is heated by computer‐controlled direct electrical resistance heating, allowing the application of variable heating rates between 0.1 and 10 K/s to temperatures up to 450°C and holding times at peak temperature between zero and 1600 s. In contrast to liquefaction experiments using closed (batch) reactors, where products remain within the reactor for the duration of the experiment, solubilised liquefaction products are continuously swept out of the reaction zone, thus minimising the probability of secondary reactions. The apparatus has been proved by performing liquefaction experiments on a selection of European and American coals and maceral concentrates. Conversion data indicate that, unlike in microbomb experiments performed under similar conditions, high temperature, long residence time runs in the flowing solvent reactor show no increase in solid residue. Preliminary size exclusion chromatography results have shown that, in contrast with trends observed in microbomb reactors, products from the flowing‐solvent reactor increase in molecular mass with increasing reaction temperature and time. The work has been extended to cover the pyrolysis and liquefaction of maceral group concentrates, showing detailed differences between the behaviour of the lithotypes under different sets of reaction conditions.