Process for the manufacture of pulp using sodium carbonate and oxygen
First Claim
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.
1 Assignment
0 Petitions
Accused Products
Abstract
A process for preparing pulp in a closed system by pre-cooking fibrous raw material in an alkaline aqueous solution of sodium carbonate or a mixture of sodium carbonate and sodium bicarbonate as the only alkaline ingredients at 90°-190° C, defibrating the pre-cooked material, pulping the defibrated material in an alkaline aqueous solution of sodium carbonate or a mixture of sodium carbonate and sodium bicarbonate as the only alkaline ingredients in a pressurized vessel at 90°-170° C in the presence of an oxygen-containing gas, subjecting waste liquor discharged from the pre-cooking and pulping steps to wet combustion to recover an alkaline aqueous substance and recycling the alkaline aqueous substance resulting from combustion to the pre-cooking and/or pulping steps.
-
Citations
5 Claims
-
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. - View Dependent Claims (2, 3, 4, 5)
- to 190°
Specification