Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C3/00—Pulping cellulose-containing materials
  • D21C3/04—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides
  • D21C3/06—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites
  • D21C3/14—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites ammonium bisulfite
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C3/00—Pulping cellulose-containing materials
  • D21C3/04—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides
  • D21C3/06—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites
  • D21C3/10—Pulping cellulose-containing materials with acids, acid salts or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sulfites magnesium bisulfite

Definitions

• the compounds used as active chemicals are all monocationic bisulphites, mainly of calcium, magnesium, sodium or ammonium.
• the pulping process with calcium bisulphite is an exception, when dolomite is used to prepare the acid.
• U.S. Pat. No. 463,499 discloses a special hardwood sulphite delignification process using exclusively the ammonium base.
• GB-A-734216 discloses a process for the treatment of wood chips with sulphur dioxide prior with digestion with alkali, namely caustic soda.
• U.S. Pat. No. 4,141,787 discloses a special acid bisulphite process using calcium or magnesium base, followed by the feed of liquid So 2 .
• DD-151581 discloses a special wood delignification process using a monocationic bisulphite.
• the present innovation refers to a chemical process for wood delignification and consists of the use of a reagent solution where ammonium and magnesium bisulphites are together the active chemicals.
• This new pulping process is particularly useful to those industrial plants where cellulose pulp is obtained by the magnesium acid bisulphite process.
• the bisulphite cooking is an aqueous solution of bisulphite containing an excess of SO 2 called “True free”.
• the composition of bisulphite cooking acid is determined by the total amount of dioxide sulphur in liquor and by ratio of Combined SO 2 to Free SO 2 .
• the amount of Free SO 2 is the total of the True Free plus one half of SO 2 in bisulphite form. It is the amount of SO 2 in excess of the amount theoretically required to form monosulphite.
• the Combined SO 2 is equal to one-half of SO 2 in the bisulphite, or equal to the amount of SO 2 held as monosulphite.
• the specific cooking acid of magnesium acid bisulphite pulping process is, physically, a gas-liquid system.
• the liquid phase is a magnesium bisulphite and sulphur dioxide aqueous solution in equilibrium with the SO 2 gas phase.
• the system is kept at temperature and pressure values of about 50° C. and 2 Kgcm ⁇ 2 , respectively.
• This particular cooking acid will be referred further on this document as the INICIAL COOKING ACID.
• ammonium hydroxide must drive the initial pH value of inicial cooking acid (1.5) to a final value between 2 and 4, depending on the needs of the process. This operation could be performed in a tank with the initial cooking acid under pressure (accumulator) or in the reactor (digester).
• the percentage of total SO2, free plus combined forms must be kept within 4% to 7%, depending on the requirements of the process, the percentage of combined SO 2 being between 1.8% and 3.0%.
• the total percentage of SO 2 total should be between 5% and 6%, the percentage of combined SO 2 being between 2.2% and 2.7%.
• the pulping process operated at a higher pH value such as that attained after ammonium hydroxide addition, decreases the wood degradation process, enables the production of cellulosic fibres with higher mechanico-physical index values, and decreases the specific consumption of wood.

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• Paper (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (8)

Families Citing this family (3)

Family Cites Families (7)

• 1997
  • 1997-04-28 PT PT101999A patent/PT101999B/pt not_active IP Right Cessation
• 1998
  • 1998-04-20 EP EP98914170A patent/EP0977918B1/en not_active Expired - Lifetime
  • 1998-04-20 BR BR9809423-8A patent/BR9809423A/pt not_active IP Right Cessation
  • 1998-04-20 AT AT98914170T patent/ATE362010T1/de not_active IP Right Cessation
  • 1998-04-20 WO PCT/PT1998/000002 patent/WO1998049390A1/en active IP Right Grant
  • 1998-04-20 AU AU68586/98A patent/AU738720B2/en not_active Ceased
  • 1998-04-20 DE DE69837755T patent/DE69837755T2/de not_active Expired - Fee Related
  • 1998-04-20 US US09/403,864 patent/US20020153108A1/en not_active Abandoned

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