(19)
(11) EP 0 309 998 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
17.07.1991 Bulletin 1991/29

(43) Date of publication A2:
05.04.1989 Bulletin 1989/14

(21) Application number: 88115896.8

(22) Date of filing: 27.09.1988
(51) International Patent Classification (IPC)4: D21C 11/06, D21C 9/00, D21C 9/10
(84) Designated Contracting States:
AT DE ES FR GB IT

(30) Priority: 28.09.1987 SE 8703718

(71) Applicant: MO OCH DOMSJÖ AKTIEBOLAG
S-891 80 Örnsköldsvik (SE)

(72) Inventor:
  • Samuelson, Hans Olof, Prof.
    S-412 74 Gothenburg (SE)

(74) Representative: Weinhold, Peter, Dr. et al
Patentanwälte Dr. Weinhold, Dannenberg, Dr. Gudel, Schubert Siegfriedstrasse 8
80803 München
80803 München (DE)


(56) References cited: : 
   
       


    (54) A method in the activation of lignocellulosic material with a gas containing nitrogen dioxide


    (57) Method of activating aqueous lignocellulosic material with a gas containing nitrogen oxide, followed by a delignification stage for the purpose of obtaining a high quality end product with no or only a slight effect on the environment. In accordance with the inventive method, the lignocellulosic material is brought into contact (18) with an oxygen-containing gas (19), and activating gas is separated from the lignocellulosic material during and/or subsequent to the activating process (9). The method is characterized by a) controlling the supply of oxygen-containing gas (12) such that the separated gas (27) contains at least 2 kg nitric oxide (NO) calculated on 1000 kg of dry lignocellulosic material, and by b) reacting the separated gas (27) in one or more stages (26) with absorption solution (25) whose original pH lies within the range 3-13.5, and by passing (28) the gas purified with the aid of absorption solution to atmosphere, or to a destruction plant optionally subsequent ot further purification of the gas.






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