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Title:
METHOD FOR RECOVERING CHEMICALS IN A PROCESS OF PRODUCING PULP BY KRAFT PROCESS
Document Type and Number:
WIPO Patent Application WO/2000/073578
Kind Code:
A1
Abstract:
A method for recovering chemicals in a process of producing pulp by the kraft process, characterized in that an alkaline solution containing Na¿2?S which flows in a process of producing pulp by the kraft process is electrolyzed by the electrolytic oxidation method; a liquid which is formed in a positive electrode side and contains a polysulfide type sulfur in an amount of 6 g/L or more is added, as it is or after being caustificated, to the process before a chip has the maximum temperature, and a NaOH solution formed in a negative electrode side is added to at least one step of the process from a step wherein a chip has the maximum temperature to a final bleaching step; and at least the chemicals discharged from one or more steps, wherein NaOH is added, of those discharged from all the steps from a digestion step to a final leaching stage are recovered and reused. The method can be employed for rendering the process to be a closed system, and at the same time for improving the yield of pulp and for reducing the occurrence of environmental problems.

Inventors:
WATANABE KEIGO (JP)
NANRI YASUNORI (JP)
ANDOH TATSUYA (JP)
NAKAO MAKOTO (JP)
Application Number:
PCT/JP2000/003401
Publication Date:
December 07, 2000
Filing Date:
May 26, 2000
Export Citation:
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Assignee:
ASAHI GLASS CO LTD (JP)
KAWASAKI KASEI CHEMICALS (JP)
JUJO PAPER CO LTD (JP)
SAKAI KAZUAKI (JP)
WATANABE KEIGO (JP)
NANRI YASUNORI (JP)
ANDOH TATSUYA (JP)
NAKAO MAKOTO (JP)
International Classes:
D21C3/02; D21C11/00; D21C11/04; (IPC1-7): D21C11/04
Domestic Patent References:
WO1997041295A11997-11-06
WO1994012720A11994-06-09
Foreign References:
SE501204C21994-12-05
JPH08311790A1996-11-26
SE391357B1977-02-14
Other References:
See also references of EP 1245723A4
Attorney, Agent or Firm:
Senmyo, Kenji (Kanda-Higashimatsushitacho Chiyoda-ku Tokyo, JP)
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