US3133789A - Chemical recovery of waste liquors - Google Patents

Chemical recovery of waste liquors Download PDF

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Publication number
US3133789A
US3133789A US109128A US10912861A US3133789A US 3133789 A US3133789 A US 3133789A US 109128 A US109128 A US 109128A US 10912861 A US10912861 A US 10912861A US 3133789 A US3133789 A US 3133789A
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United States
Prior art keywords
sodium
smelt
carbon dioxide
sodium carbonate
sulfide
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US109128A
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English (en)
Inventor
Salvatore A Guerrieri
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Lummus Technology LLC
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Lummus Co
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Priority to US109128A priority Critical patent/US3133789A/en
Priority to NO144236A priority patent/NO117826B/no
Priority to AT384262A priority patent/AT256608B/de
Priority to DEL42903A priority patent/DE1224599B/de
Priority to FR910132A priority patent/FR1341695A/fr
Application granted granted Critical
Publication of US3133789A publication Critical patent/US3133789A/en
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D7/00—Carbonates of sodium, potassium or alkali metals in general
    • C01D7/02—Preparation by double decomposition
    • 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
    • D21C11/12—Combustion of pulp liquors
    • D21C11/122—Treatment, e.g. dissolution, of the smelt
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S423/00—Chemistry of inorganic compounds
    • Y10S423/03—Papermaking liquor

Definitions

  • the present invention relates to a process for recovering chemicals from the waste liquors produced in the wood pulping industry. In its more specific aspects, this invention relates to a continuous process for the preparation of delignification liquors from sodium base waste sulfite liquors for reuse in the pulping processes.
  • Pulp may be prepared by several processes including mechanical, chemical and semi-chemical processes.
  • Mechanical processes are based upon the physical reduction of cellulosic material to a fibrous state whereas the chemical processes, such as the acid sulfite, sulfate and soda processes, are based upon the chemical removal of the capitaous compounds contained in the cellulosic material.
  • chemical and mechanical processes have been widely utilized, it has only been in recent years that semi-chemical processes have achieved substantial importance, even though such processes have a substantially higher pulp yield.
  • Semi-chemical processes normally comprise the steps of reacting the cellulosic material with a chemical liquor to partially remove the ligneous compounds and thereafter subjecting the partially delignified cellulosic material to a mechanical process to complete fiberization.
  • a residual waste liquor from a sodium sulfite or sodium bisulfite delignification contains sulfur dioxide bearing compounds of sodium, principally as ligno-sulfonic compounds or other organic sulfonic compounds formed by the action of the cooking liquor on the organic substances present in the ligneous cellulosic material, together with some residual sulfite compound or compounds. It also ordinarily contains other organic compounds derived from the cellulosic material or formed by the action of the cooking liquor on constituents of such material including, for example, sugars or other carbohydrates, and various organic acids, such as formic or acetic acid or the salts thereof.
  • the present invention is applicable to the treatment of the residual liquor obtained from delignifying processes utilizing various types of sodium base sulfite chemicals such as the sodium base acid sulfite processes, in which the cooking liquor contains sodium acid sulfite (NaHSO and generally free sulfurous acid, whereas the residual liquor contains some sodium acid sulfite together with ligno-sulfonic compounds and other organic compounds as mentioned hereinabove, and the neutral sodium base sulfiite processes in which the cooking liquor contains sodium sulfite (Na SO and one or more alkaline compounds of sodium such as sodium bicarbonate and/or sodium carbonate, whereas the residual liquor contains sodium sulfite with some of the other alkaline sodium compounds together with ligno-sulfonic compounds and other organic compounds as mentioned hereinbefore.
  • sodium base sulfite chemicals such as the sodium base acid sulfite processes
  • the cooking liquor contains sodium acid sulfite (NaHSO and generally free sulfurous acid
  • the residual liquor
  • Another object of this invention is to provide a novel method of treating the smelt formed by burning such waste liquors to convert the sodium sulfide content thereof to sodium carbonate.
  • the temperature in the reactor be maintained above the melting point of sodium carbonate to avoid clogging up the reactor.
  • the temperature in the reactor is maintained substantially above the melting point of sodium carbonate so as to convert substantially all of the sodium sulfide in the smelt to sodium carbonate. Further, with high conversion temperatures, the rate of reaction will be higher, thus resulting in smaller sized equipment.
  • the thus treated smelt is thereafter passed through a series of processing steps whereby cooking liquors are formed for use in delignifying cellulosic materials.
  • the preferred embodiment comprises the following principal components, namely a primary recovery furnace 10 for burning the concentrated waste or black liquor, a converter 11 in which sodium sulfide in the molten smelt received from the furnace is subjected to chemical reactions, a dissolver 12 and a clarifier 13 adapted to recover sodium carbonate from the smelt leaving the converter, and carbon dioxide and sulfur dioxide recovery units 15 and 17, respectively.
  • Concentrated black liquor is fed into the recovery furnace 10 through line 19.
  • the black liquor is burned to form gaseous products and a smelt primarily containing sodium carbonate and sodium sulfide.
  • the temperature in the furnace 10 is maintained at a value at which the concentrated black liquor will burn in the presence of a combustion supporting medium.
  • Combustion air and make-up sulfur for the system are admitted to the furnace through lines 21 and 21, respectively.
  • the gaseous products formed in the converter 11 consisting primarily of hydrogen sulfide, carbon dioxide and water vapors may also be passed into the furnace 10 via line 22 wherein the hydrogen sulfide is converted to sulfur dioxide.
  • the gaseous products leaving the furnace 10 are passed through line 23 to sulfur dioxide and carbon dioxide recovery units 15 and 17 which will be described in detail subsequently.
  • the combustion gases in line 23 consist primarily of carbon dioxide, water vapor, sulfur dioxide, and nitrogen.
  • the smelt in the converter is reacted with carbon dioxide and water vapor introduced through line 24 and which is heated prior to introduction in a suitable manner (not shown).
  • the conversion of sodium sulfide to sodium carbonate may be represented by the following reactions:
  • the conversion of the sodium sulfide to sodium carbonate is represented by the overall Equation 2 above. It will be appreciated that the above equations represent the primary reactions taking place. It is obvious that insignificant side reactions will also take place, such as, for example, the formation of minor amounts of sodium sulfate.
  • the converter 11 is maintained at a temperature above the melting point of sodium carbonate (i.e. 851 C.) and preferably at a substantially higher temperature above the melting point for efficient and effective operation.
  • the gaseous products formed in the converter 11 are passed into the furnace 10 through line 22 as previously stated. Alternatively, these gases may be vented to an auxiliary heat exchange unit to undergo combustion and heat recovery.
  • the thus treated smelt mainly consisting of sodium carbonate is passed to dissolver 12 through line 25 wherein water is added to form a solution which is known in the art as green liquor.
  • the green liquor sodium carbonate solution
  • the clarifier 13 is passed to the clarifier 13.
  • the sodium carbonate solution in clarifier 13 may be passed partially through line 27 directly to the second stage of a two-stage delignification cycle, partially through lines 28 and 29 to the carbon dioxide make-up unit 17, and partially to a sulfite reactor 16 via lines 30 and 31.
  • the use of the sodium carbonate solution in the latter two instances will be presently described in detail.
  • converter 11 Although only one converter 11 has been shown, it is obvious that either a plurality of converters or a multistage converter may be utilized. Similarly, it is obvious that the carbon dioxide and water vapor introduced into the converter 11 which is shown entering through line 24 may enter via separate lines.
  • the carbon dioxide and the steam used in the converter 11 may be supplied from any suitable source. For purposes of economy it is preferable to supply these reactants from sources within the instant system or from related sources within the plant.
  • gaseous carbon dioxide is withdrawn from the reactor 16, a reboiler 18, and a blow gas scrubber 14 and may be passed to converter 11 through lines 32, 33, and 34, respectively.
  • Blow gas primarily containing carbon dioxide and sulfur dioxide is introduced into the scrubber 14 from the digesters (not shown).
  • a sodium sulfite solution is passed in counter-current relation to the blow gas whereby the sulfur dioxide contained therein reacts with a portion of sodium sulfite to form sodium bisulfite in accordance with Equation 3.
  • the sodium sulfite solution is introduced into scrubber 14 through line 35 and is obtained from reactor 16.
  • the sodium sulfite-sodium bisulfite solution formed in the scrubber 14 is withdrawn through line 36 and is passed to sulfur dioxide recovery tower 15 through line 37.
  • the combustion products leaving the recovery furnace 10 may be vented to the atmosphere through a stack (not shown). However, it is preferable from an economic stand-point to pass these gases through various processing units to recover the sulfur dioxide and/ or carbon dioxide contents thereof.
  • the sulfur dioxide in the combustion gas flowing in the line 23 is removed by passing the combustion gases counter-current to a sodium sulfite-sodium bisulfite solution in accordance with Equation 3 above.
  • a portion of the sodium bisulfite solution formed is passed to a digester in another part of the plant through line 38, with the remaining portion being passed to the reactor 16 through lines 39 and 31.
  • the sodium bisulfite solution is contacted with the sodium carbonate solution from clarifier 13 to form a sodium sulfite solution in accordance with the following equation:
  • the sodium sulfite solution is transferred through line 35 to scrubber 14 and/or through line 37 to the recovery unit 15 for use in recovering the sulfur dioxide content of the furnace off-gas according to Equation 3 above.
  • the carbon dioxide produced in reactor 16 is passed via lines 32 and 24 to converter 11.
  • the sodium bicarbonate solution is removed from the unit 17 through line 40 and passed to reboiler 18 wherein the solution is heated to form carbon dioxide and sodium carbonate in accordance with the reverse reaction shown by Equation 5.
  • the sodium carbonate solution is passed to a digester as a second-stage cooking liquor through line 41 or is recycled to the unit 17 through line 29.
  • the steam and carbon dioxide which are formed are sent to the converter 11 through lines 33 and 24.
  • sulfur dioxide recovery unit 15 and the carbon dioxide recovery unit 17 are shown as superimposed, it is obvious that these units may be separated.
  • a mixture of 50% sodium carbonate and 50% sodium sulfide was placed in a cylindrical stainless steel cylinder about 1% inches in diameter and 8 to 10 inches long and this was placed in an electrical furnace. Heat was applied and when a temperature of about 1500 F. was reached, the mixture was a molten fluid mass. At this point, a mixture of CO and water vapor was introduced through a tube leading to the bottom of the cylindrical vessel and H 8 was driven off. Since this reaction was carried out in the open, the hydrogen sulfide formed, burned to sulfur dioxide. As the reaction proceeded and the ratio of sodium sulfide to sodium carbonate decreased, the melting point of the mixture increased and a cake of essentially sodium carbonate began to form in the tube.
  • the above described process may be modified by supplying air or oxygen) to the converter 11 through the optional air inlet 41.
  • the hydrogen sulfide formed in the converter 11 will be oxidized primarily to sulfur dioxide in the converter 11 rather than in the furnace 10.
  • the reaction will proceed according to the following equation:
  • reaction in converter 11 would proceed according to Equation 1.
  • the resultant reaction products may be used directly or may be carbonized by adding a carbonating agent, either carbon dioxide or carbonic acid at a subsequent point in the system, for example, at the dissolver 12. Reaction (1a) above would then take place with a resultant formation of sodium carbonate.
  • a process for treating sodium base waste liquors from a wood pulping process the steps of burning said waste liquors to form a smelt primarily comprised of sodium sulfide and sodium carbonate, removing the gases formed during this heat treatment, contacting said smelt with carbon dioxide and steam to convert sodium sulfide to sodium carbonate, maintaining said smelt in a substantially molten state during the above step, removing the gaseous products of reaction, and dissolving the thus treated smelt to form a solution primarily comprised of sodium carbonate.
  • a process for treating sodium base waste liquors the steps of burning said liquors in a furnace to form a smelt primarily comprised of sodium sulfide and sodium carbonate, passing said smelt to a reactor, contacting in said reactor said smelt with carbon dioxide and water vapor, maintaining the temperature of said contact above 851 C., passing the gaseous products of the reaction formed in said reactor to said furnace, dissolving the thus treated smelt to form a solution primarily comprised of sodium carbonate, and clarifying said solution.

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  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
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US109128A 1961-05-10 1961-05-10 Chemical recovery of waste liquors Expired - Lifetime US3133789A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US109128A US3133789A (en) 1961-05-10 1961-05-10 Chemical recovery of waste liquors
NO144236A NO117826B (cs) 1961-05-10 1962-05-03
AT384262A AT256608B (de) 1961-05-10 1962-05-10 Verfahren zur Behandlung von Ablaugen auf Natriumbasis
DEL42903A DE1224599B (de) 1961-05-10 1962-09-07 Regenerieren von sauren, neutralen und alkalischen Natriumsulfitzellstoffablaugen
FR910132A FR1341695A (fr) 1961-05-10 1962-09-21 Procédé de récupération des lessives résiduaires de la préparation des pâtes de bois

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AT (1) AT256608B (cs)
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3401010A (en) * 1964-09-17 1968-09-10 Lummus Co Preparation of alkali metal carbonates from the corresponding sulfates or sulfides
US3438728A (en) * 1967-05-15 1969-04-15 North American Rockwell Two-stage regeneration of absorbent for sulfur oxides
US3516796A (en) * 1968-11-26 1970-06-23 North American Rockwell Carbonaceous process for sulfur production
DE1769352A1 (de) * 1967-05-15 1971-11-25 North American Rockwell Regenerierung eines Absorptionsmittels unter Verwendung eines Kohlenstoff-Regenerierungsmittels

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1483160A (en) * 1922-03-28 1924-02-12 Darco Corp Recovering soda and active carbon
US2841561A (en) * 1954-03-12 1958-07-01 Rayonier Inc Recovery of chemicals from smelt solutions
US2849292A (en) * 1953-11-16 1958-08-26 Mead Corp Pulp manufacture
US2864669A (en) * 1954-11-01 1958-12-16 Stora Kopparbergs Bergslags Ab Method for recovering sulfur and alkali from waste liquors
US2967758A (en) * 1956-06-21 1961-01-10 Babcock & Wilcox Co Method of and apparatus for disintegrating and dispersing a molten smelt stream

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1483160A (en) * 1922-03-28 1924-02-12 Darco Corp Recovering soda and active carbon
US2849292A (en) * 1953-11-16 1958-08-26 Mead Corp Pulp manufacture
US2841561A (en) * 1954-03-12 1958-07-01 Rayonier Inc Recovery of chemicals from smelt solutions
US2864669A (en) * 1954-11-01 1958-12-16 Stora Kopparbergs Bergslags Ab Method for recovering sulfur and alkali from waste liquors
US2967758A (en) * 1956-06-21 1961-01-10 Babcock & Wilcox Co Method of and apparatus for disintegrating and dispersing a molten smelt stream

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3401010A (en) * 1964-09-17 1968-09-10 Lummus Co Preparation of alkali metal carbonates from the corresponding sulfates or sulfides
US3438728A (en) * 1967-05-15 1969-04-15 North American Rockwell Two-stage regeneration of absorbent for sulfur oxides
DE1769352A1 (de) * 1967-05-15 1971-11-25 North American Rockwell Regenerierung eines Absorptionsmittels unter Verwendung eines Kohlenstoff-Regenerierungsmittels
US3516796A (en) * 1968-11-26 1970-06-23 North American Rockwell Carbonaceous process for sulfur production

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NO117826B (cs) 1969-09-29
AT256608B (de) 1967-08-25

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