Methods for producing pulp and treating black liquor
First Claim
1. A method for treating black liquor to produce inorganic material and a synthesis gas having as components CO2, CO, H2O, and H2 together with methane and, C2+ components, said process comprising:
- providing a reactor having a processing region provided with a mass of particulate material consisting of or containing an alkaline earth metal oxide;
supplying heated fluidizing gas to the processing region so as to induce a swirling flow of the particulate material within said processing region, the particulate material to assuming a compact band and circulating about an axis of said processing region in a turbulent manner, the fluidizing gas including a sub-stochiometric quantity of oxygen for partially oxidizing the organic material of the black liquor and for converting other organic material of the black liquor to said synthesis gas;
feeding the black liquor into said compact band of particulate material so that it is heated at a temperature of 650-725°
C. and becomes gasified;
recovering said synthesis gas as off-gas from said bed containing <
1% by volume of oxygen; and
recovering inorganic material from said black liquor as solids from said bed.
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Accused Products
Abstract
A method is provided for treating black liquor particularly derived from non-wood pulp, by heating with an alkaline earth metal oxide in a toroidal fluidised bed reactor at a temperature of above 650° C. The method may be used alone or as part of a method of converting graminaceous raw material to pulp for paper or board, said method comprising (a) digesting said raw material with a white liquor based on sodium hydroxide and further comprising calcium hydroxide in an amount effective to substantially convert silica of said raw material to calcium silicate; (b) recovering pulp and black liquor substantially free of uncombined silica; (c) heating the black liquor in a fluidized bed reactor containing calcium oxide for catalysing conversion of organic content of said black liquor to gas and for providing recovered solids including sodium values of said white liquor and calcium oxide; and regenerating said white liquor using said recovered solids. The use of the above mentioned white liquor permits treatment of wheat straw, rice straw and other high-silica materials without resulting in a black liquor that is difficult to treat.
88 Citations
20 Claims
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1. A method for treating black liquor to produce inorganic material and a synthesis gas having as components CO2, CO, H2O, and H2 together with methane and, C2+ components, said process comprising:
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providing a reactor having a processing region provided with a mass of particulate material consisting of or containing an alkaline earth metal oxide;
supplying heated fluidizing gas to the processing region so as to induce a swirling flow of the particulate material within said processing region, the particulate material to assuming a compact band and circulating about an axis of said processing region in a turbulent manner, the fluidizing gas including a sub-stochiometric quantity of oxygen for partially oxidizing the organic material of the black liquor and for converting other organic material of the black liquor to said synthesis gas;
feeding the black liquor into said compact band of particulate material so that it is heated at a temperature of 650-725°
C. and becomes gasified;
recovering said synthesis gas as off-gas from said bed containing <
1% by volume of oxygen; and
recovering inorganic material from said black liquor as solids from said bed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of converting graminaceous raw material to pulp for paper or board, said method comprising:
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digesting said raw material with a white liquor based on sodium hydroxide and further comprising calcium hydroxide in an amount effective to substantially convert silica of said raw material to calcium silicate;
recovering pulp from said digestion step;
recovering black liquor from said digestion step by washing said digested pulp and optionally also by recovering black liquor direct from said digestion step, said recovered black liquor being substantially free of soluble silicate;
heating the black liquor in a fluidized bed reactor containing calcium oxide for catalysing conversion of organic content of said black liquor to gas and for providing recovered solids including sodium values of said white liquor and calcium oxide; and
regenerating said white liquor using said recovered solids. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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- 19. Use of calcium hydroxide as an additive in the soda process digestion of a graminaceous starting material to form pulp for inhibiting scaling during black liquor concentration and recovery when processing black liquor at least partly from pulp washing.
Specification