Process of recovering sodium carbonate from spent pulping liquors
First Claim
1. A process for the manufacture of cellulose pulp by means of a soda process in which spent liquors are concentrated by evaporation and the concentrated liquors are incinerated in a fluidized bed incinerator to produce a granular sodium carbonate incinerator product contaminated by chlorides, sulphates and potassium compounds, the incinerator product being dissolved in water and causticized in known manner to form white liquor comprising essentially sodium hydroxide, which white liquor is re-used in the said soda process to provide a closed system, the improvement comprising:
- treating the incinerator product with water to form a slurry, agitating the slurry so as to dissolve incinerator product with its contaminants and at the same time crystallize substantially pure sodium carbonate monohydrate leaving a major proportion of the contaminants in solution, separating the substantially pure sodium carbonate from the liquor containing the contaminants, and washing the separated sodium carbonate with water;
converting sodium carbonate remaining with the contaminants in solution to sodium bicarbonate by carbonation with carbon dioxide, separating the precipitate so formed from the mother liquor, and converting the precipitate thus recovered to substantially pure sodium carbonate;
utilizing sodium carbonate recovered in the formation of white liquor; and
discharging the contaminant bearing mother liquor from the system.
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Accused Products
Abstract
The incinerator product obtained from the incineration of black liquor and other spent liquors from a soda pulping process is treated to remove contaminants including chlorides, sulphates and potassium compounds and to recover a high proportion of the sodium carbonate. The incinerator product is treated with water to form a slurry in which substantially pure sodium carbonate monohydrate is crystallized and a major proportion of the contaminants are dissolved, the sodium carbonate monohydrate is then separated and dissolved sodium carbonate is recovered as a bicarbonate or sesquicarbonate precipitate by carbonation of the solution. The preferred process involves an initial flue gas carbonation of the separated mother liquor after removal of sodium carbonate monohydrate to produce a sodium sesquicarbonate precipitate and a subsequent carbonation of the mother liquor, after separation of the sodium sesquicarbonate therefrom, with pure carbon dioxide to precipitate sodium bicarbonate.
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Citations
9 Claims
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1. A process for the manufacture of cellulose pulp by means of a soda process in which spent liquors are concentrated by evaporation and the concentrated liquors are incinerated in a fluidized bed incinerator to produce a granular sodium carbonate incinerator product contaminated by chlorides, sulphates and potassium compounds, the incinerator product being dissolved in water and causticized in known manner to form white liquor comprising essentially sodium hydroxide, which white liquor is re-used in the said soda process to provide a closed system, the improvement comprising:
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treating the incinerator product with water to form a slurry, agitating the slurry so as to dissolve incinerator product with its contaminants and at the same time crystallize substantially pure sodium carbonate monohydrate leaving a major proportion of the contaminants in solution, separating the substantially pure sodium carbonate from the liquor containing the contaminants, and washing the separated sodium carbonate with water; converting sodium carbonate remaining with the contaminants in solution to sodium bicarbonate by carbonation with carbon dioxide, separating the precipitate so formed from the mother liquor, and converting the precipitate thus recovered to substantially pure sodium carbonate; utilizing sodium carbonate recovered in the formation of white liquor; and discharging the contaminant bearing mother liquor from the system. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A process for the manufacture of cellulose pulp by means of a soda process in which spent liquors are concentrated by evaporation and the concentrated liquors are incincerated in a fluidized bed incinerator to produce a granular sodium carbonate incinerator product contaminated by chlorides, sulphates and potassium compounds, the incinerator product being dissolved in water and causticized in known manner to form white liquor comprising essentially sodium hydroxide, which white liquor is re-used in the said soda process to provide a closed system, the improvement comprising:
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treating the incinerator product with water to form a slurry, agitating the slurry so as to dissolve incinerator product with its contaminants and at the same time crystallize substantially pure sodium carbonate monohydrate leaving a major proportion of the contaminants in solution, separating the substantially pure sodium carbonate from the first mother liquor containing the contaminants, and washing the separated sodium carbonate with water; carbonating the first mother liquor with a flue gas containing carbon dioxide, maintaining the liquor at a temperature of about 45°
C. producing a precipitate consisting mainly of sodium sesquicarbonate, separating the precipitate from the resulting second mother liquor, and converting the precipitate to substantially pure sodium carbonate;converting sodium carbonate in the second mother liquor to sodium bicarbonate by carbonation with substantially pure carbon dioxide, separating the sodium bicarbonate precipitate so formed from the mother liquor, and converting the precipitate thus recovered to substantially pure sodium carbonate; utilizing sodium carbonate recovered in the formation of white liquor; and discharging the contaminant bearing second mother liquor from the system. - View Dependent Claims (8)
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9. A process for the manufacture of cellulose pulp by means of a soda process in which spent liquors are concentrated by evaporation and the concentrated liquors are incinerated in a fluidized bed incinerator to produce a granular sodium carbonate incinerator product contaminated by chlorides, sulphates and potassium compounds, the incinerator product being dissolved in water and causticized in known manner to form white liquor comprising essentially sodium hydroxide, which white liquor is re-used in the said soda process to provide a closed system, the improvement comprising:
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treating the incinerator product with water to form a slurry, agitating the slurry so as to dissolve incinerator product with its contaminants and at the same time crystallize substantially pure sodium carbonate monohydrate leaving a major proportion of the contaminants in solution, separating the substantially pure sodium carbonate from the mother liquor containing the contaminants, and washing the separated sodium carbonate with water; and carbonating the mother liquor with a flue gas containing carbon dioxide, maintaining the liquor at a temperature of about 45°
C. producing a precipitate consisting mainly of sodium sesquicarbonate, separating the precipitate from the mother liquor, and converting the precipitate to substantially pure sodium carbonate;utilizing sodium carbonate recovered in the formation of white liquor; and discharging the contaminant bearing second mother liquor from the system.
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Specification