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Process for the manufacture of pulp using sodium carbonate and oxygen

  • US 4,045,279 A
  • Filed: 09/09/1976
  • Issued: 08/30/1977
  • Est. Priority Date: 01/17/1972
  • Status: Expired due to Term
First Claim
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1. A process for the manufacture of pulp in a closed system, which comprisesmixing a fibrous raw material with an alkaline aqueous solution of sodium carbonate or a mixture of a major proportion of sodium carbonate and a minor proportion of sodium bicarbonate as the only alkaline ingredients, which alkaline aqueous solution is completely free of sulfite and sulfide compounds and sulfur-containing ions resulting from dissolution of said compounds, the amount of sodium carbonate or mixture of sodium carbonate and sodium bicarbonate being 5 - 20% by weight, as sodium oxide, based on the weight of the raw material,pre-cooking the fibrous raw material in the alkaline aqueous solution at a temperature of 90°

  • to 190°

    C,3. defibrating the pre-cooked material by mechanical means,4. removing a major proportion of waste liquor, formed during the pre-cooking step, from the defibrated material,5. pulping the defibrated material in an alkaline aqueous solution of sodium carbonate or a mixture of a major proportion of sodium carbonate and a minor proportion of sodium bicarbonate as the only alkaline ingredients, which alkaline aqueous solution is completely free of sulfite and sulfide compounds and sulfur-containing ions resulting from dissolution of said compounds, the amount of sodium carbonate or mixture of sodium carbonate and sodium bicarbonate being 5 - 20% by weight, as sodium oxide, based on the weight of the raw material, in a pressurized pulping vessel at a temperature of 90°

    to 170°

    C in the presence of an oxygen-containing gas,6. discharging waste liquor, formed during the pulping step, from the pulping vessel,7. subjecting the waste liquor discharged from at least one of the pre-cooking and pulping steps to wet combustion, in which the waste liquor is treated at a temperature exceeding 230°

    C in the presence of an oxygen-containing gas, to recover an alkaline aqueous substance containing sodium carbonate or a mixture of a major proportion of sodium carbonate and a minor proportion of sodium bicarbonate as the only alkaline ingredients and8. recycling the recovered alkaline aqueous substance, without any chemical treatment thereof, to at least one of the pre-cooking and pulping steps.

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