WO1993006298A1 - A method of producing sodium hydroxide - Google Patents

A method of producing sodium hydroxide Download PDF

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Publication number
WO1993006298A1
WO1993006298A1 PCT/FI1992/000247 FI9200247W WO9306298A1 WO 1993006298 A1 WO1993006298 A1 WO 1993006298A1 FI 9200247 W FI9200247 W FI 9200247W WO 9306298 A1 WO9306298 A1 WO 9306298A1
Authority
WO
WIPO (PCT)
Prior art keywords
sodium
melt
produced
sodium hydroxide
reduction reaction
Prior art date
Application number
PCT/FI1992/000247
Other languages
French (fr)
Inventor
Kaj Henricson
Anja Klarin
Original Assignee
A. Ahlstrom Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by A. Ahlstrom Corporation filed Critical A. Ahlstrom Corporation
Publication of WO1993006298A1 publication Critical patent/WO1993006298A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D1/00—Oxides or hydroxides of sodium, potassium or alkali metals in general
    • C01D1/04—Hydroxides
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/0064—Aspects concerning the production and the treatment of green and white liquors, e.g. causticizing green liquor
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/04—Regeneration of pulp liquors or effluent waste waters of alkali lye
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/40—Production or processing of lime, e.g. limestone regeneration of lime in pulp and sugar mills

Definitions

  • the high Na2C ⁇ 3-content melt produced in the chemical recovery of a pulp mill can be formed in either a conven ⁇ tional recovery boiler or in an other type of boiler, such as a boiler operating in oxidizing conditions. It is desirable to convert all or some of this carbonate to sodium hydroxide, needed, e.g., as a cooking chemical in the production of pulp. In a pulp mill this is accomplished by dissolving the melt in dilute white liquor, thus produc ⁇ ing green liquor containing sodium carbonate and sodium sul ⁇ phide. The sodium carbonate contained by the green liquor is converted into sodium hydroxide by causticizing it with calcium hydroxide. The calcium carbonate formed in the reaction is regenerated in a lime kiln to be used again in causticizing. The process of producing cellulose pulp would be much more efficient if it were possible to produce sodium hydroxide in a simpler way.
  • the object of the present invention is to provide a method of producing sodium hydroxide without causticizing. This is accomplished by converting the sodium carbonate, formed in the boiler in the combustion of black liquor, into sodium oxide or sodium, which is then dissolved in water to form sodium hydroxide.
  • a method of producing sodium hydroxide by reducing, with a carbon-containing material, the sodium carbonate-containing melt produced in the combustion of black liquor and by heating it to form sodium oxide and/or sodium, wherein in the reduction reaction the amount of the sodium oxide and/or sodium formed is determined by controlling the reaction condition, such as carbon content and/or tempera ⁇ ture, and that the sodium-containing fumes produced in the reduction reaction are led into contact with water in order to produce a solution of sodium hydroxide.
  • Fig. 1 is a schematic illsutration of an apparatus for performing the method according the invention
  • Fig. 2 is a detail on enlarged scale of an apparatus for performing an alternative embodiment of the invention.
  • Melt 1 produced in a boiler in the combustion of black liquor, is directed into a melt reactor 10, in which strongly reducing conditions are prevalent. Heat is intro ⁇ fied in the reactor by means 2 of, e.g, electric resistors or hot gases.
  • the heat from the hot gases can also be indirectly transferred, by means of a heat exchanger, into the melt, in which case the heat exchanger is located in the melt reactor or in the combustion chamber, in which the hot gases are produced.
  • the hot gases are available from any combustion chamber, e.g., a recovery boiler.
  • Graphite or carbon 3 is also introduced into the melt for maintaining the reduction conditions. In these conditions the sodium carbonate contained by the melt is decomposed according to the following reactions:
  • the produced fumes (fumes in this case meaning vapours, exhausts and melt spouts) and carbon monoxide are intro ⁇ quizd via 7 into a scrubber 13, in which sodium oxide and sodium are absorbed in water, whereby sodium hydroxide is formed. Most preferably it is hot water that is used in the absorbing in order to prevent carbon monoxide from dissolving in the water.
  • an inert gas 12 such as a rare gas or nitrogen, can be introduced into the melt reactor so as to reduce the partial pressure of carbon monoxide.
  • the carbon monoxide 8 is directed from the scrubber, e.g., back to the recovery boiler for combustion.
  • the sodium hydroxide solution 5 produced in the absorbtion can be used in the pulp mill, for example at the digester or bleach plant. If the amount of sodium hydroxide needed is not great, only a portion of the melt is directed to the melt reactor or only a portion of the sodium carbonate is converted into sodium oxide and sodium at the melt reactor by controlling the reaction conditions, such as carbon content and/
  • the remaining melt 4 is directed to a dissolving tank 11, in which the melt is dissolved to form green liquor.
  • the sulphidity of the produced liquor 6 increases with the amount of sodium oxide and sodium separated in the melt reactor.
  • the green liquor can be utilized as such in the digester or after further treatment, if any.
  • the further treatment can comprise clarifying and/or causticizing.
  • the cooking liquor having a higher sulphidity than the original melt, is most preferably used in the initial stages of the cook.
  • the liquor 6 and sodium hydroxide solution 5 can also be mixed together in order to obtain the desired sodium sulphide/sodium hydroxide ratio.
  • the sulphidity, especially the sodium sulphide content, of the melts 1 and 4 can further be increased by treating the melts with a gas containing hydrogen sulphide and/or ethene.
  • the treatment can be effected in the melt flow 1, reactor 10 or melt flow 4, according to the method described in Finnish patent application FI 914585.
  • Sodium sulphide is formed when the molten sodium carbonate reacts with hydrogen sulphide and sodium sulphate reacts with ethene.
  • the decomposition of sodium carbonate can be further enhanced by carrying such out in the presence of molten carbon-saturated iron (fig. 2).
  • the melt reactor 20 is filled with molten iron, through which the melt 21 is directed from the boiler via the bottom of the melt reactor. Because of its lightness, this sodium-containing melt rises on the surface, wherefrom it is withdrawn into the dissolving tank as described previously. The following reaction takes place in the melt reactor 20 in the presence of carbon:
  • Carbon and heat are added so as to keep both of the melts in a molten phase and to replace the carbon expended in the reaction.
  • the produced mixture of sodium and sodium oxide fumes is directed into the scrubber to form sodium hydroxide as described above.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Paper (AREA)

Abstract

The invention relates to a method of producing sodium hydroxide in a pulp mill without causticizing. This is accomplished by converting the sodium carbonate, formed in the boiler in the combustion of black liquor, into carbon monoxide and vapours of sodium oxide or sodium, which are subsequently dissolved in water to form sodium hydroxide.

Description

A METHOD OF PRODUCING SODIUM HYDROXIDE
The high Na2Cθ3-content melt produced in the chemical recovery of a pulp mill can be formed in either a conven¬ tional recovery boiler or in an other type of boiler, such as a boiler operating in oxidizing conditions. It is desirable to convert all or some of this carbonate to sodium hydroxide, needed, e.g., as a cooking chemical in the production of pulp. In a pulp mill this is accomplished by dissolving the melt in dilute white liquor, thus produc¬ ing green liquor containing sodium carbonate and sodium sul¬ phide. The sodium carbonate contained by the green liquor is converted into sodium hydroxide by causticizing it with calcium hydroxide. The calcium carbonate formed in the reaction is regenerated in a lime kiln to be used again in causticizing. The process of producing cellulose pulp would be much more efficient if it were possible to produce sodium hydroxide in a simpler way.
The object of the present invention is to provide a method of producing sodium hydroxide without causticizing. This is accomplished by converting the sodium carbonate, formed in the boiler in the combustion of black liquor, into sodium oxide or sodium, which is then dissolved in water to form sodium hydroxide.
Thus, according to the present invention there is provided a method of producing sodium hydroxide by reducing, with a carbon-containing material, the sodium carbonate-containing melt produced in the combustion of black liquor and by heating it to form sodium oxide and/or sodium, wherein in the reduction reaction the amount of the sodium oxide and/or sodium formed is determined by controlling the reaction condition, such as carbon content and/or tempera¬ ture, and that the sodium-containing fumes produced in the reduction reaction are led into contact with water in order to produce a solution of sodium hydroxide. The invention will be described further by way of example with reference to the accompanying drawings, in which Fig. 1 is a schematic illsutration of an apparatus for performing the method according the invention, and
Fig. 2 is a detail on enlarged scale of an apparatus for performing an alternative embodiment of the invention.
Melt 1, produced in a boiler in the combustion of black liquor, is directed into a melt reactor 10, in which strongly reducing conditions are prevalent. Heat is intro¬ duced in the reactor by means 2 of, e.g, electric resistors or hot gases. The heat from the hot gases can also be indirectly transferred, by means of a heat exchanger, into the melt, in which case the heat exchanger is located in the melt reactor or in the combustion chamber, in which the hot gases are produced. The hot gases are available from any combustion chamber, e.g., a recovery boiler. Graphite or carbon 3 is also introduced into the melt for maintaining the reduction conditions. In these conditions the sodium carbonate contained by the melt is decomposed according to the following reactions:
Na2C03 + 2 C -> 2 Na T + 3 CO T or Na2C03 + C -> Na20 T + 2 CO T.
The produced fumes (fumes in this case meaning vapours, exhausts and melt spouts) and carbon monoxide are intro¬ duced via 7 into a scrubber 13, in which sodium oxide and sodium are absorbed in water, whereby sodium hydroxide is formed. Most preferably it is hot water that is used in the absorbing in order to prevent carbon monoxide from dissolving in the water. If needed, an inert gas 12, such as a rare gas or nitrogen, can be introduced into the melt reactor so as to reduce the partial pressure of carbon monoxide. The carbon monoxide 8 is directed from the scrubber, e.g., back to the recovery boiler for combustion. The sodium hydroxide solution 5 produced in the absorbtion can be used in the pulp mill, for example at the digester or bleach plant. If the amount of sodium hydroxide needed is not great, only a portion of the melt is directed to the melt reactor or only a portion of the sodium carbonate is converted into sodium oxide and sodium at the melt reactor by controlling the reaction conditions, such as carbon content and/or temperature.
The remaining melt 4 is directed to a dissolving tank 11, in which the melt is dissolved to form green liquor. The sulphidity of the produced liquor 6 increases with the amount of sodium oxide and sodium separated in the melt reactor. The green liquor can be utilized as such in the digester or after further treatment, if any. The further treatment can comprise clarifying and/or causticizing.
The cooking liquor, having a higher sulphidity than the original melt, is most preferably used in the initial stages of the cook. The liquor 6 and sodium hydroxide solution 5 can also be mixed together in order to obtain the desired sodium sulphide/sodium hydroxide ratio.
The sulphidity, especially the sodium sulphide content, of the melts 1 and 4, can further be increased by treating the melts with a gas containing hydrogen sulphide and/or ethene. The treatment can be effected in the melt flow 1, reactor 10 or melt flow 4, according to the method described in Finnish patent application FI 914585. Sodium sulphide is formed when the molten sodium carbonate reacts with hydrogen sulphide and sodium sulphate reacts with ethene.
The decomposition of sodium carbonate can be further enhanced by carrying such out in the presence of molten carbon-saturated iron (fig. 2). The melt reactor 20 is filled with molten iron, through which the melt 21 is directed from the boiler via the bottom of the melt reactor. Because of its lightness, this sodium-containing melt rises on the surface, wherefrom it is withdrawn into the dissolving tank as described previously. The following reaction takes place in the melt reactor 20 in the presence of carbon:
Na2C03 + [C]Fe -> Na20 T + 2 CO T or
Na2C03 + 2 [C]Fe -> 2 Na T + 3 CO T.
Carbon and heat are added so as to keep both of the melts in a molten phase and to replace the carbon expended in the reaction. The produced mixture of sodium and sodium oxide fumes is directed into the scrubber to form sodium hydroxide as described above.

Claims

We claim:
1. A method of producing sodium hydroxide by reducing, with a carbon-containing material, the sodium carbonate- containing melt produced in the combustion of black liquor and by heating it to form sodium oxide and/or sodium, characterized in that in the reduction reaction the amount of the sodium oxide and/or sodium formed is determined by controlling the reaction conditions, such as carbon content and/or temperature, and that the sodium-containing fumes produced in the reduction reaction are led into contact with water in order to produce a solution of sodium hydroxide.
2. A method according to claim 1, characterized in that iron is utilized to enhance the reduction reaction, whereby the reduction reaction is effected in carbon-containing molten iron.
3. A method according to claim 1 or 2, characterized in that inert gas is introduced into the reaction to reduce the partial pressure of the produced carbon monoxide.
4. A method according to claim 1, 2 or 3, characterized in that heat is introduced into the reaction, preferably by means of electric resistors or hot gases, to maintain the melt in a molten phase.
5. A method according to claim 4, characterized in that heat is transferred from the gases to the melt by means of indirect heat exchange.
6. A method according to claim 5, characterized in that the heat exchanger is located in the melt reactor.
7. A method according to claim 5, characterized in that the heat exchanger is located in the combustion chamber, in which the hot gases are produced.
8. A method according to any of the preceding claims, characterized in that the reacted melt, the sodium carbonate content of which is thus reduced, is dissolved in water to form green liquor.
9. A method according to any of the preceding claims, characterized in that the carbon monoxide produced in the reduction reaction is recovered, preferably for subsequent combustion.
10. An apparatus for use in the production of sodium hydroxide as claimed in claim 1 constructed and arranged to operate substantially as herein described with reference to the accompanying drawings.
PCT/FI1992/000247 1991-09-27 1992-09-22 A method of producing sodium hydroxide WO1993006298A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI914587 1991-09-27
FI914587A FI914587A (en) 1991-09-27 1991-09-27 FOERFARANDE FOER FRAMSTAELLNING AV SODRIUMHYDROXID

Publications (1)

Publication Number Publication Date
WO1993006298A1 true WO1993006298A1 (en) 1993-04-01

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1992/000247 WO1993006298A1 (en) 1991-09-27 1992-09-22 A method of producing sodium hydroxide

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FI (1) FI914587A (en)
WO (1) WO1993006298A1 (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0090568A1 (en) * 1982-03-25 1983-10-05 Australian Paper Manufacturers Limited Improved alkali regeneration process
US4637858A (en) * 1985-02-25 1987-01-20 Crown Zellerbach Corporation Pyrolysis of black liquor at high temperatures using radiant energy
FI78748B (en) * 1988-01-20 1989-05-31 Teraesbetoni Oy Process and device for reclaiming chemicals from a slurry yielded by the burning of pulp by-product containing sodium carbonate
US4917763A (en) * 1984-10-19 1990-04-17 Skf Steel Engineering Ab Method of recovering chemical from spent pulp liquors

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0090568A1 (en) * 1982-03-25 1983-10-05 Australian Paper Manufacturers Limited Improved alkali regeneration process
US4917763A (en) * 1984-10-19 1990-04-17 Skf Steel Engineering Ab Method of recovering chemical from spent pulp liquors
US4637858A (en) * 1985-02-25 1987-01-20 Crown Zellerbach Corporation Pyrolysis of black liquor at high temperatures using radiant energy
FI78748B (en) * 1988-01-20 1989-05-31 Teraesbetoni Oy Process and device for reclaiming chemicals from a slurry yielded by the burning of pulp by-product containing sodium carbonate

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DERWENT'S ABSTRACT, No. 486 69 B/26; & SU,A,621 818, Publ. week 7926. *

Also Published As

Publication number Publication date
FI914587A0 (en) 1991-09-27
FI914587A (en) 1993-03-28

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