High-yield semi-chemical carbonate pulping process

• US 4,229,251 A
• Filed: 03/31/1976
• Issued: 10/21/1980
• Est. Priority Date: 12/09/1974
• Status: Expired due to Term

• Current Assignee: Domtar Incorporated (PT Sinar Mas Group)
• Original Assignee: Domtar Incorporated (PT Sinar Mas Group)
• Inventors: Temler, Jan S.
• Primary Examiner(s): Bashore, S. Leon
• Assistant Examiner(s): Alvo, Steve
• Application Number:
  US05/672,138
• Time in Patent Office: 1,665 Days
• Field of Search: 162/20, 162/28, 162/90, 162/30 R, 162/24
• US Class Current: 162/28
• CPC Class Codes: D21C 3/02 with inorganic bases or alkaline reacting compounds, e.g. sulfate processes

Abstract

High-yield pulp suitable for the production of corrugating medium is produced by cooking hardwood chips at a temperature 180°-192° with sodium carbonate solutions of a concentration 65 to 120 g/l as Na₂ O, at a liquor to wood ratio of 1.2-2.5, and mechanically refining the cooked chips in a primary refining stage to a C. S. Freeness less than 480, and then refining the pulp in a secondary refining stage.

Claims

1. A method of producing high-yield semi-chemical pulp suitable for the manufacture of corrugating medium comprising mixing hardwood chips with a liquor consisting essentially of an aqueous solution of sodium carbonate having a concentration of carbonate between 65 and 120 grams per liter expressed as Na₂ O, cooking the chips with said liquor at a temperature between 170°

C. and 200°

C. to a pulp yield of about 70-85%, separating the cooked chips from residual liquor and immediately thereafter passing said chips to a primary refining state, mechanically refining the cooked chips in said primary refining state to a pulp of a C.S.F. value not greater than 480, and mechanically refining said pulp in a secondary refining stage.

2. The method of claim 1 wherein said cooking is carried out in a continuous digester with a liquor to wood ratio between 1.2 and 2.5 and a charge of chemical on wood between 5 and 12%.

3. The method of claim 2 wherein the cooking temperature is maintained between 180°

C. and 192°

C. for a time between 8 and 30 minutes.

4. The method of claim 3 wherein said cooked chips are refined in said primary refining stage to a pulp of a C.S.F. value of 400-480.

5. The method of claim 3 wherein said pulp is refined in said secondary refining stage to a C.S.F. value of 180-350.

6. The method of claim 1 wherein said cooked chips are refined in said primary refining stage to a pulp of a C.S.F. value of 400-480.

7. The method of claim 1 wherein said pulp is refined in said secondary refining stage to a C.S.F. value of 180-350.

8. The method of claim 1 wherein the liquor separated from the pulp is burnt in oxidative conditions in a recovery furnace to produce heat and a sodium carbonate residue and said sodium carbonate is re-used for the making of the cooking liquor.

9. The method of claim 1 wherein the liquor separated from the pulp is fed to a fluidized bed recovery furnace, the fluidized bed being formed of particles of sodium carbonate, the liquor is burnt in said fluidized bed to produce heat and a residue consisting of particles of sodium carbonate, and at least a portion of said particles of sodium carbonate is reused for the making of cooking liquor.