Process for recovering energy and chemicals from spent liquor in pulp preparation

A process for recovering energy and chemicals from spent liquor containing organic materials in pulp preparation, said liquor being thermally decomposed after concentration, forming gaseous and solid products and energy being recovered from the gases, the process comprising:

• concentrating said spent liquor containing organic materials;
• and thermally decomposing said concentrated spent liquor, wherein said thermal decomposition is carried out in a single step at a supply of oxygen in an amount corresponding to from 5 to 75% of the stoichiometric amount required for a complete oxidation, at a pressure of from 10 to 50 bar and at a temperature of from 700.degree. to 850.degree. C. such that no melt is formed, wherein the formation of carbon from included organic materials is suppressed and wherein the thermal decomposition forms sulfur-containing gases which are recovered by being absorbed in an alkaline solution.