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Sodium sulfide pulping with hydrogen sulfide generation

  • US 4,113,553 A
  • Filed: 01/27/1977
  • Issued: 09/12/1978
  • Est. Priority Date: 02/05/1976
  • Status: Expired due to Term
First Claim
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1. A process for pulping hardwood to produce cellulose pulp in good yield and of high quality, with a low requirement for causticized pulping liquor, which comprises in a first pulping stage, in the absence of added carbon dioxide, pulping the hardwood in an alkaline pulping liquor containing sodium sulfide at a pH within the range from about 10.5 to about 13 and at a temperature within the range from about 110°

  • to about 170°

    C for a time sufficient to consume at least 3%, based on the dry weight of the wood, of alkali in the pulping liquor, determined as titratable alkali, in chemical reactions with the wood, thereby forming a large proportion of soluble organic acids in the pulping liquor, and generating hydrogen sulfide in situ in the alkaline pulping liquor by reaction of sodium sulfide with said organic acids; and

    then in a second pulping stage, following directly after the first pulping stage, continuing the pulping at a pH higher than said first stage pH, within the range from about 12.5 to about 14, and at a temperature higher than said first stage temperature, within the range from about 145°

    to about 190°

    C, in the presence of added alkaline pulping liquor comprising sodium hydroxide and sodium sulfide until cellulose pulp is produced.

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