Pyrolysis process

Abstract

Pyrolytic vapors, produced by the pyrolysis of coal, are contacted with a quench liquid which comprises a hydrogen donor solvent to condense the pyrolytic vapors and form a liquid mixture which comprises pyrolytic condensate. The liquid mixture is separated by vacuum flashing into a vapor containing tar acids and a liquid mixture containing the quench liquid and condensate remainder. This liquid mixture is then heated to transfer hydrogen from the hydrogen donor solvent to the condensate remainder. The hydrogenated liquid mixture is then separated into a heavy hydrocarbon stream and a solvent mixture which contains the spent and unused hydrogen donor solvent. The vapor produced by the vacuum flashing is then condensed and separated into a liquid stream containing tar acids, and a tar acid raffinate. A mixture of the solvent mixture and the tar acid raffinate is separated into light aromatics, intermediate coal liquids, and a mixture of two- and three-ring aromatics and the spent and unused hydrogen donor solvent. The latter mixture is then hydrogenated with gaseous hydrogen to produce two- and three-ring hydroaromatics and a hydrogenated spent hydrogen donor solvent, both of which are operative for recycle as a quench liquid and subsequently as a hydrogen donor solvent in the process. Coal is pyrolyzed, in the presence of a carbon containing solid particulate source of heat and a beneficially reactive transport gas, to form a pyrolysis product stream which contains a gaseous mixture and particulate solids. The beneficially reactive transport gas inhibits the reactivity of the char product and the carbon-containing solid particulate source of heat. The particulate solids are separated from the gaseous mixture to form a substantially solids-free gaseous stream which contains the pyrolytic vapors which are subsequently contacted with the quench liquid.