Patent ID: 7465372

Claim:
Method for treatment of black liquor at a pulp mill in order to recover its contents of chemicals and energy, comprising the following steps: passing a black liquor flow ( 10 ) from an evaporation plant to a pyrolysis reactor ( 1 ), pyrolysing the black liquor in the pyrolysis reactor at a temperature of 300-800° C. in the absence of an external gas component in order to separate evaporable compounds ( 12 ) from coke ( 11 ), said coke remaining in a solid state, the evaporable compounds containing vaporized water, recovering the evaporable compounds ( 12 ) from the pyrolysis reactor, passing the coke ( 11 ) from the pyrolysis reactor to a gasification reactor ( 3 ) for gasification, gasifying the coke in the gasification reactor under such conditions that sulphur compounds contained in the coke ( 11 ) and deriving from the cooking chemicals are reduced to sodium sulphide, and recovering product gases generated by gasification in the gasification reactor.