EP0088456A1 - Process for the continuous removal of silicic acid from waste liquors deriving from cellulose pulp production - Google Patents
Process for the continuous removal of silicic acid from waste liquors deriving from cellulose pulp production Download PDFInfo
- Publication number
- EP0088456A1 EP0088456A1 EP83200178A EP83200178A EP0088456A1 EP 0088456 A1 EP0088456 A1 EP 0088456A1 EP 83200178 A EP83200178 A EP 83200178A EP 83200178 A EP83200178 A EP 83200178A EP 0088456 A1 EP0088456 A1 EP 0088456A1
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- European Patent Office
- Prior art keywords
- precipitate
- separated
- silica
- liquor
- treated
- Prior art date
- Legal status (The legal status 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 status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims description 30
- 239000002699 waste material Substances 0.000 title claims description 21
- 239000001913 cellulose Substances 0.000 title description 4
- 229920002678 cellulose Polymers 0.000 title description 4
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 title description 3
- 235000012239 silicon dioxide Nutrition 0.000 title description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 46
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 23
- 239000002244 precipitate Substances 0.000 claims abstract description 20
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims abstract description 15
- 235000011941 Tilia x europaea Nutrition 0.000 claims abstract description 15
- 239000004571 lime Substances 0.000 claims abstract description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 11
- 230000029087 digestion Effects 0.000 claims abstract description 5
- 239000007791 liquid phase Substances 0.000 claims abstract description 3
- 239000007790 solid phase Substances 0.000 claims abstract description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 35
- 239000007789 gas Substances 0.000 claims description 16
- 235000011121 sodium hydroxide Nutrition 0.000 claims description 15
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 13
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 12
- 239000003546 flue gas Substances 0.000 claims description 12
- 238000002485 combustion reaction Methods 0.000 claims description 9
- 239000000292 calcium oxide Substances 0.000 claims description 8
- 239000000706 filtrate Substances 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 8
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 239000008267 milk Substances 0.000 claims description 6
- 210000004080 milk Anatomy 0.000 claims description 6
- 235000013336 milk Nutrition 0.000 claims description 6
- 241000196324 Embryophyta Species 0.000 claims description 5
- 235000012255 calcium oxide Nutrition 0.000 claims description 5
- 239000000155 melt Substances 0.000 claims description 5
- 238000002844 melting Methods 0.000 claims description 5
- 230000008018 melting Effects 0.000 claims description 5
- 239000011734 sodium Substances 0.000 claims description 5
- 239000010902 straw Substances 0.000 claims description 5
- 235000017166 Bambusa arundinacea Nutrition 0.000 claims description 4
- 235000017491 Bambusa tulda Nutrition 0.000 claims description 4
- 235000014676 Phragmites communis Nutrition 0.000 claims description 4
- 244000273256 Phragmites communis Species 0.000 claims description 4
- 235000015334 Phyllostachys viridis Nutrition 0.000 claims description 4
- 239000011425 bamboo Substances 0.000 claims description 4
- 238000009993 causticizing Methods 0.000 claims description 4
- 238000002386 leaching Methods 0.000 claims description 4
- 238000004062 sedimentation Methods 0.000 claims description 4
- 241000609240 Ambelania acida Species 0.000 claims description 3
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 3
- 239000010905 bagasse Substances 0.000 claims description 3
- 238000005119 centrifugation Methods 0.000 claims description 3
- 239000000470 constituent Substances 0.000 claims description 3
- 238000010309 melting process Methods 0.000 claims description 3
- 239000003513 alkali Substances 0.000 claims description 2
- 230000005496 eutectics Effects 0.000 claims description 2
- 238000001914 filtration Methods 0.000 claims description 2
- 230000004927 fusion Effects 0.000 claims description 2
- 238000004094 preconcentration Methods 0.000 claims description 2
- -1 that the separated Chemical compound 0.000 claims description 2
- 244000082204 Phyllostachys viridis Species 0.000 claims 1
- 239000000920 calcium hydroxide Substances 0.000 abstract description 2
- 235000011116 calcium hydroxide Nutrition 0.000 abstract description 2
- 238000010924 continuous production Methods 0.000 abstract 1
- 239000003265 pulping liquor Substances 0.000 abstract 1
- 239000010802 sludge Substances 0.000 description 12
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 241001330002 Bambuseae Species 0.000 description 3
- 238000009835 boiling Methods 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000003245 coal Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012856 packing Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 240000007594 Oryza sativa Species 0.000 description 1
- 235000007164 Oryza sativa Nutrition 0.000 description 1
- 241000209504 Poaceae Species 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 239000000378 calcium silicate Substances 0.000 description 1
- 229910052918 calcium silicate Inorganic materials 0.000 description 1
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 description 1
- 235000013339 cereals Nutrition 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000004572 hydraulic lime Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000012716 precipitator Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 235000009566 rice Nutrition 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Images
Classifications
-
- 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
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S210/00—Liquid purification or separation
- Y10S210/928—Paper mill waste, e.g. white water, black liquor treated
-
- 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 invention relates to a process for the continuous removal of silica from alkaline digestion of annual plants, such as bamboo, bagasse, reeds and straw, from pulp leaching (black liquors) by treatment with gases containing Co 2 and removal of the precipitated silica.
- a process is also known for removing dissolved silica from alkaline pulp lye by precipitation with lime at boiling temperature and with stirring, the lye first being thickened to a dry matter content of about 30% before treatment and then mixed with burnt lime at the boiling point with stirring and after a short reaction time is separated from the precipitated reaction sludge in a manner known per se (DE-PS 10 46 465).
- Another known method works with two process stages, in the first stage the waste liquor is treated with carbon dioxide until a certain pH value is reached, at least about 75% of the silica in the waste liquor is precipitated and the precipitated silica is separated off, and in which the second stage, the partially decilified waste liquor is treated with lime milk in such a way that the desired degree of decilification is achieved by precipitation and separation of calcium silicate (DE-OS 30 03 090).
- the object of the invention is to avoid these and other disadvantages of the prior art.
- a method is to be proposed with which it is possible in a simple and economical manner, particularly from cellulose leaching those with a high silicic acid content, such as those that arise, for example, in the alkaline digestion of annual plants, to remove silicic acid as far as possible.
- the environment should not be polluted here.
- the silicate-containing waste product is said to be easily removable and, if appropriate, to be able to be used in other industries.
- This object is achieved in that the waste liquor is pre-concentrated and brought into intensive contact with the CO 2 -containing gases, that the amount of CO 2 -containing gases is measured to 30 to 40 m 3 per m 3 of spent liquor that one passes through the treated lye is freed from the precipitated silica, that the separated, silica-containing precipitates are diluted with water and washed, causticized by adding lime, the solid and liquid phases are separated and the residue thus obtained is burnt out to the melt, if appropriate, and the cooled melt is granulated.
- Flue gas is preferred as the gas containing CO 2 . This has the advantage that it is cheap and occurs in your own process.
- the CO 2 content can be very low, for example below 5% by volume.
- the waste liquor to be treated is expediently pre-concentrated to a concentration of 8 to 30, preferably 12 to 25,% by weight of dry matter.
- the preconcentrated waste liquor is brought into contact with the CO 2 -containing gases in a jacket-heated reaction vessel by means of a pipe bend gasifier, with a particularly intensive mass transfer taking place.
- the precipitate precipitated by the treatment with the CO 2 -containing gases can be separated from the waste liquor by sedimentation or centrifugation.
- the separated silica-containing precipitate is diluted and washed with water in a ratio of 1: 4 to 1: 1, depending on the further processing.
- Quicklime or lime milk is added to the washing water in an amount sufficient to convert the soda content of the precipitate into caustic soda by causticizing.
- the filtrate obtained after filtering off the washed precipitate is combined with the waste liquor freed from the silica and the mixture is returned to the pre-concentration.
- sodium hydroxide solution can also be added to the mixture in order to control the viscosity of the thick liquor after the evaporation process.
- any organic compounds still present can be removed from the separated precipitate by burning out.
- the heat supply can, if desired, be increased to such an extent that the precipitate leaves the incinerator as a melt. This is cooled in the air flow and e.g. Use a grinder with a sieve to grind the granules to the desired grain size. As a result, the residue can be disposed of in an environmentally friendly manner or reused.
- sa is advantageously carried out in such a way that when washing the precipitate and causticizing the soda content, the Na 2 O-SiO 2 -CaO ratio is set such that the lowest melting temperature of this eutectic fusion compound is ensured for the melting process.
- the advantages achieved by the invention consist in particular in the fact that it is possible with a simple, continuously carried out process to remove silica up to a residual content of 0.2 to 0.4 g / l from leaching liquors which are released during the alkaline digestion of annual plants such as bamboo, bagasse, reeds, straw, can be obtained, remove.
- By hiring can be melted down in conventional coal, gas or oil combustion boilers.
- the process is very economical because, with the exception of small amounts of lime, e.g. in the form of quicklime or lime milk, no foreign chemicals are required.
- the flue gas generated in your own process is available for decilification.
- the process works in an environmentally friendly way.
- decilified black liquor can be worked up to the combustion concentration of 60 to 65% DM in an indirect evaporator.
- Post-evaporation for example through direct contact of the liquor with flue gas in a cyclone or cascade evaporator, in order to achieve the combustion concentration, can thus be dispensed with.
- the invention is shown schematically in the drawing, for example, and is described in more detail below.
- Fiber-free thin liquor with a minimum concentration of 8 to 12% dissolved dry matter (TS) is pumped from the pulp factory or from one of the first evaporation stages to the reactor 4 in the decilification plant. Likewise, flue gas, the temperature of which should be above the dew point to prevent moisture precipitation, is blown into the reactor 4 via a blower 10.
- TS dissolved dry matter
- the action of the pipe elbow fumigator creates intensive contact between the lye and the flue gas.
- the exhaust gases escape via a mechanical foam separator via the dome of the reaction container.
- the treated lye leaves the reactor at the desired pH via a siphon and arrives at a continuously operating device 12 for separating the precipitated substances (centrifuge or sedimentation funnel + centrifuge). After separating the precipitate from the alkali, the clear filtrate is conveyed to an intermediate container 13.
- the separated silica sludge is pumped into a stirred tank 14. This is additionally supplied with water and quicklime or lime milk from a corresponding metering device 15 for sludge washing.
- the amount of lime corresponds to approximately 1.5 to 2 times the stoichiometric requirement, based on the soda (Na2Co3) content of the sludge.
- the sludge suspension is drawn off and centrifuged on a separator or decanter 17.
- the clear filtrate is passed to a separate stacking tank 18, from where it is either added to the clarified black liquor or used for other purposes.
- the dewatered, washed sludge is either delivered directly to the landfill or to one Furnace 22 for post-combustion of the remaining organic constituents still contained therein.
- a melting process brought about by combustion leads to an environmentally friendly, landfillable or processable waste product after the melt has cooled and granulated.
- Such burning and melting can e.g. take place in a coal, gas or oil-fired steam boiler, which is provided for this purpose with a combustion chamber, the bottom of which is designed as a melting bed with an extraction device for the melt.
- Waste liquor from a rice straw pulp factory is treated according to the above description using pilot plant trials for decilification.
- the inorganic components of the sludge from the first centrifugation stage 12 contain a certain proportion of soda (Na 2 CO 3 ).
- soda Na 2 CO 3
- the causticizing process -
Landscapes
- Removal Of Specific Substances (AREA)
- Paper (AREA)
- Processing Of Solid Wastes (AREA)
- Silicon Compounds (AREA)
- Treatment Of Sludge (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
- Treating Waste Gases (AREA)
Abstract
Description
Die Erfindung betrifft ein Verfahren zur kontinuierlichen Entfernung von Kieselsäure aus durch alkalischen Aufschluß von Einjahrespflanzen, wie Bambus, Bagasse, Schilf und Stroh, erhaltenen Zellstoffablaugen (Schwarzlaugen) durch Behandlung mit Co 2-haltigen Gasen und Abtrennung der ausgefällten Kieselsäure.The invention relates to a process for the continuous removal of silica from alkaline digestion of annual plants, such as bamboo, bagasse, reeds and straw, from pulp leaching (black liquors) by treatment with gases containing Co 2 and removal of the precipitated silica.
Es ist bekannt, zur Entkieselung alkalischer kieselsäurehaltiger Zellstoffablaugen bei der Verarbeitung von Gräsern, insbesondere Stroh, Bambus, Schilf usw., in die Schwarzlauge Kohlendioxid einzuleiten und die entstehende gallertige Kieselsäure durch Kochen bzw. durch Erhitzen unter Druck in eine filtrierbare kristallinische Masse überzuführen und diese von der Lauge zu trennen (DE-PS 522 730).It is known for the decalcification of alkaline silica-containing cellulose lye in the processing of grasses, in particular straw, bamboo, reeds, etc., to introduce carbon dioxide into the black liquor and to convert the resulting gelatinous silica into a filterable crystalline mass by boiling or by heating under pressure, and this to separate from the lye (DE-PS 522 730).
Es ist ferner ein Verfahren zur Entfernung gelöster Kieselsäure aus alkalischen Zellstoffablaugen durch Ausfällung mittels Kalk bei Siedetemperatur und unter Rühren bekannt, wobei die Lauge vor der Behandlung zunächst auf einen Trockengehalt von etwa 30 % eingedickt und erst dann in der Siedehitze unter Rühren mit gebranntem Kalk versetzt und nach kurzer Reaktionsdauer in an sich bekannter Weise vom ausgefällten Reaktionsschlamm getrennt wird (DE-PS 10 46 465).A process is also known for removing dissolved silica from alkaline pulp lye by precipitation with lime at boiling temperature and with stirring, the lye first being thickened to a dry matter content of about 30% before treatment and then mixed with burnt lime at the boiling point with stirring and after a short reaction time is separated from the precipitated reaction sludge in a manner known per se (DE-PS 10 46 465).
Ein weiteres bekanntes Verfahren arbeitet mit zwei Verfahrensstufen, wobei in der ersten Stufe die Ablauge mit Kohlendioxid bis zum Erreichen eines bestimmten pH-Wertes behandelt wird, mindestens ca. 75 % der Kieselsäure in der Ablauge ausgefällt werden und die ausgefällte Kieselsäure abgetrennt wird und wobei in der zweiten Stufe die in der ersten Stufe teilentkieselte Ablauge mit Kalkmilch derart behandelt wird, daß der gewünschte Entkieselungsgrad durch Ausfällen und Abtrennen von Calciumsilicat erzielt wird (DE-OS 30 03 090).Another known method works with two process stages, in the first stage the waste liquor is treated with carbon dioxide until a certain pH value is reached, at least about 75% of the silica in the waste liquor is precipitated and the precipitated silica is separated off, and in which the second stage, the partially decilified waste liquor is treated with lime milk in such a way that the desired degree of decilification is achieved by precipitation and separation of calcium silicate (DE-OS 30 03 090).
Diese bekannten Verfahren sind zum Teil umständlich und die eingesetzten Fällapparaturen liefern nicht immer befriedigende Entkieselungsergebnisse.These known methods are sometimes cumbersome and the precipitators used do not always provide satisfactory decilification results.
Die Anwendung von Wäscher- oder Strahlpumpensystemen zur Si02-Ausfällung bedarf sehr hoher Rauchgasmengen mit hohen C02-Gehalten. Der Einsatz hoher Gasmengen führt zu unerwünscht starker Schaumbildung während der Laugenbehandlung. Die Anwendung von mit Füllkörpern versehenen Absorptionstürmen ist über lange Betriebsperioden ebenfalls problematisch. Die Füllkörper werden sehr schnell mit ausgefällter Materie verunreinigt und bedürfen periodischer Spülung.The use of scrubber or jet pump systems for Si0 2 precipitation requires very high amounts of flue gas with high C0 2 contents. The use of large amounts of gas leads to undesirably strong foaming during the lye treatment. The use of absorption towers with packing elements is also problematic over long periods of operation. The packings are very quickly contaminated with precipitated matter and require periodic rinsing.
Die Behandlung mit Kalk führt zwar zu ähnlichen Entkieselungsergebnissen, jedoch ist die Methode aufgrund des hohen Kalkverbrauchs teuer und die organischen und alkalischen Verluste sind gleichfalls relativ hoch. Der Schlammanfall ist beträchtlich. Über eine umweltfreundliche Methode der Aufbereitung des Abfallschlammes oder dessen sinnvolle Wiederverwendung ist nichts bekannt-.The treatment with lime leads to similar de-silicification results, but the method is expensive due to the high lime consumption and the organic and alkaline losses are also relatively high. The amount of mud is considerable. Nothing is known about an environmentally friendly method of treating the waste sludge or reusing it.
Der Erfindung liegt die Aufgabe zugrunde, diese und andere Nachteile des Standes der Technik zu vermeiden. Es soll ein Verfahren vorgeschlagen werden, mit dem es auf einfache und wirtschaftliche Weise gelingt, aus Zellstoffablaugen, insbesondere solchen mit hohem Kieselsäuregehalt, wie sie z.B. beim alkalischen Aufschluß von Einjahrespflanzen entstehen, Kieselsäure möglichst weitgehend zu entfernen. Hierbei soll die Umwelt nicht belastet werden. Das silikathaltige Abfallprodukt soll leicht abführbar und gegebenenfalls in anderen Industrien verwendet werden können.The object of the invention is to avoid these and other disadvantages of the prior art. A method is to be proposed with which it is possible in a simple and economical manner, particularly from cellulose leaching those with a high silicic acid content, such as those that arise, for example, in the alkaline digestion of annual plants, to remove silicic acid as far as possible. The environment should not be polluted here. The silicate-containing waste product is said to be easily removable and, if appropriate, to be able to be used in other industries.
Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß man die Ablauge vorkonzentriert und mit den C02-haltigen Gasen in intensiven Kontakt bringt, daß man die Menge der C02-haltigen Gase auf 30 bis 40 m3 pro m3 durchgesetzter Ablauge bemißt, daß man die behandelte Lauge von der ausgefällten Kieselsäure befreit, daß man die abgetrennten, kieselsäurehaltigen Niederschläge mit Wasser verdünnt und wäscht, durch Zugabe von Kalk kaustiziert, Fest- und Flüssigphase voneinander trennt und den so erhaltenen Rückstand gegebenenfalls bis zur Schmelze ausbrennt und die abgekühlte Schmelze granuliert.This object is achieved in that the waste liquor is pre-concentrated and brought into intensive contact with the CO 2 -containing gases, that the amount of CO 2 -containing gases is measured to 30 to 40 m 3 per m 3 of spent liquor that one passes through the treated lye is freed from the precipitated silica, that the separated, silica-containing precipitates are diluted with water and washed, causticized by adding lime, the solid and liquid phases are separated and the residue thus obtained is burnt out to the melt, if appropriate, and the cooled melt is granulated.
Als CO2-haltiges Gas wird Rauchgas bevorzugt. Dies hat den Vorteil, daß es billig ist und im eigenen Verfahren anfällt. Der CO2-Gehalt kann hierbei sehr niedrig sein und zum Beispiel unter 5 Vol.-% liegen.Flue gas is preferred as the gas containing CO 2 . This has the advantage that it is cheap and occurs in your own process. The CO 2 content can be very low, for example below 5% by volume.
Die zu behandelnde Ablauge wird erfindungsgemäß zweckmäßig auf eine Konzentration von 8 bis 30, vorzugsweise 12 bis 25, Gew.-% TS vorkonzentriert.According to the invention, the waste liquor to be treated is expediently pre-concentrated to a concentration of 8 to 30, preferably 12 to 25,% by weight of dry matter.
Die vorkonzentrierte Ablauge wird im Rahmen der Erfindung in einem mantelbeheizten Reaktionsbehälter mittels Rohrbogenbegasers mit den CO2-haltigen Gasen in Kontakt gebracht, wobei ein besonders intensiver Stoffaustausch erfolgt.In the context of the invention, the preconcentrated waste liquor is brought into contact with the CO 2 -containing gases in a jacket-heated reaction vessel by means of a pipe bend gasifier, with a particularly intensive mass transfer taking place.
Der durch die Behandlung mit den C02-haltigen Gasen ausgefällte Niederschlag kann von der Ablauge durch Sedimentieren oder Zentrifugieren abgetrennt werden.The precipitate precipitated by the treatment with the CO 2 -containing gases can be separated from the waste liquor by sedimentation or centrifugation.
Nach einer Weiterbildung der Erfindung wird der abgetrennte kieselsäurehaltige Niederschlag je nach Weiterverarbeitung mit Wasser im Verhältnis 1 zu 4 bis 1 zu 1, verdünnt und gewaschen. Dem Waschwasser wird Branntkalk oder Kalkmilch zugegeben in einer Menge, die ausreichend ist, den Sodagehalt des Niederschlages durch Kaustizierreaktion in Natronlauge umzuwandeln.According to a development of the invention, the separated silica-containing precipitate is diluted and washed with water in a ratio of 1: 4 to 1: 1, depending on the further processing. Quicklime or lime milk is added to the washing water in an amount sufficient to convert the soda content of the precipitate into caustic soda by causticizing.
Nach einer weiteren Ausgestaltung der Erfindung vereinigt man das nach Abfiltrieren des gewaschenen Niederschlages erhaltene Filtrat mit der von der Kieselsäure befreiten Ablauge und führt das Gemisch in die Vorkonzentrierung zurück.According to a further embodiment of the invention, the filtrate obtained after filtering off the washed precipitate is combined with the waste liquor freed from the silica and the mixture is returned to the pre-concentration.
Falls erforderlich, kann dem Gemisch noch zusätzlich Natronlauge zudosiert werden, um die Viskosität der Dicklauge nach dem Eindampfvorgang zu steuern.If necessary, sodium hydroxide solution can also be added to the mixture in order to control the viscosity of the thick liquor after the evaporation process.
Aus dem abgetrennten Niederschlag können im Rahmen der Erfindung noch enthaltene organische Verbindungen durch Herausbrennen entfernt werden. Die Wärmezufuhr kann, falls gewünscht, so weit gesteigert werden, daß der Niederschlag den Verbrennungsofen als Schmelze verläßt. Diese wird im Luftstrom abgekühlt und z.B. mittels einer Mühle mit Siebeinsatz zu Granulat gewünschter Körnung vermahlen. Hierdurch kann der Rückstand umweltfreundlich deponiert oder weiterverwendet werden.In the context of the invention, any organic compounds still present can be removed from the separated precipitate by burning out. The heat supply can, if desired, be increased to such an extent that the precipitate leaves the incinerator as a melt. This is cooled in the air flow and e.g. Use a grinder with a sieve to grind the granules to the desired grain size. As a result, the residue can be disposed of in an environmentally friendly manner or reused.
Im Rahmen der Erfindung wird vorteilhafterweise sa verfahren, daß man bei der Wäsche des Niederschlages und der Kaustizierung des Sodaanteils das Na2O-SiO2-CaO-Verhältnis so einstellt, daß für den Schmelzvorgang die niedrigste Schmelztemperatur dieser eutektischen Schmelzverbindung gewährleistet ist.In the context of the invention, sa is advantageously carried out in such a way that when washing the precipitate and causticizing the soda content, the Na 2 O-SiO 2 -CaO ratio is set such that the lowest melting temperature of this eutectic fusion compound is ensured for the melting process.
Die mit der Erfindung erzielten Vorte-ile bestehen insbesondere darin, daß es mit einem einfachen, kontinuierlich durchzuführenden Verfahren gelingt, Kieselsäure bis auf einen Restgehalt von 0,2 bis 0,4 g/1 aus Ablaugen, die beim alkalischen Aufschluß von Einjahrespflanzen, wie Bambus, Bagasse, Schilf, Stroh, erhalten werden, zu entfernen. Durch die Einstellung können diese in herkömmlichen Kohle-, Gas- oder Ölverbrennungskesseln eingeschmolzen werden.The advantages achieved by the invention consist in particular in the fact that it is possible with a simple, continuously carried out process to remove silica up to a residual content of 0.2 to 0.4 g / l from leaching liquors which are released during the alkaline digestion of annual plants such as Bamboo, bagasse, reeds, straw, can be obtained, remove. By hiring can be melted down in conventional coal, gas or oil combustion boilers.
Das Verfahren ist sehr wirtschaftlich, weil mit Ausnahme geringer Kalkmengen, z.B. in Form von Branntkalk oder Kalkmilch, keine fremden Chemikalien erforderlich sind. Zur Entkieselung steht das im eigenen Verfahren kostenlos anfallende Rauchgas zur Verfügung. Das Verfahren arbeitet umweltfreundlich.The process is very economical because, with the exception of small amounts of lime, e.g. in the form of quicklime or lime milk, no foreign chemicals are required. The flue gas generated in your own process is available for decilification. The process works in an environmentally friendly way.
Ein weiterer Vorteil besteht darin, daß die entkieselte Schwarzlauge bis auf die Verbrennungs-Konzentration von 60 bis 65 % TS im indirekten Eindampfer aufgearbeitet werden kann. Eine Nachverdampfung beispielsweise durch direkten Kontakt der Lauge mit Rauchgas in einem Zyklon- oder Kaskaden-Verdampfer, um die Verbrennungs-Konzentration zu erreichen, kann somit entfallen.Another advantage is that the decilified black liquor can be worked up to the combustion concentration of 60 to 65% DM in an indirect evaporator. Post-evaporation, for example through direct contact of the liquor with flue gas in a cyclone or cascade evaporator, in order to achieve the combustion concentration, can thus be dispensed with.
Die Erfindung ist in der Zeichnung beispielsweise und schematisch dargestellt und wird im folgenden näher beschrieben.The invention is shown schematically in the drawing, for example, and is described in more detail below.
Es bedeuten:It means:
1 Zufuhr Zellstoffablauge (Schwarzlauge); 2 Eindampfeinrichtung; 3 Vorkonzentrierte Ablauge; 4 Reaktionsbehälter zum In-Kontakt-bringen von Ablauge mit CO2-haltigen Gasen (Rauchgas); 5 Laugenverbrennung; 6 Dampfkessel; 7 Abzug Rauchgas; 8 Abzug Rauchgas; 9 Leitung Rauchgas in Reaktionsbehälter 4; 10 Gebläse; 11 Abzug Schmelze; 12 Abtrenneinrichtung (Zentrifuge); Sedimentiertrichter + Zentrifuge); 13 Zwischenbehälter zur Aufnahme des Filtrats (entkieselte Schwarzlauge); 14 Rührbehälter zur Aufnahme des abgeschiedenen Kieselsäureschlamms; 15 Dosiereinrichtung für Zufuhr Kalk oder Kalkmilch; 16 Zufuhr Wasser; 17 Trenneinrichtung (Separator, Dekanter); 18 Behälter zur Aufnahme des Filtrats; 19 Leitung zum Zwischenbehälter 13 (entkieselte Schwarzlauge); 20 Leitung entkieselte Schwarzlauge; 21 Behälter zur Aufnahme von Natronlauge; 22 Verbrennung; 23 Verbrennungsrückstand oder Schmelze. -1 supply of cellulose waste liquor (black liquor); 2 evaporation device; 3 pre-concentrated waste liquor; 4 reaction vessels for bringing waste liquor into contact with gases containing CO 2 (flue gas); 5 lye burning; 6 steam boilers; 7 flue gas discharge; 8 flue gas discharge; 9 line of flue gas in reaction vessel 4; 10 blowers; 11 melt deduction; 12 separation device (centrifuge); Sedimentation funnel + centrifuge); 13 intermediate containers to hold the filtrate (decilified black liquor); 14 stirred tanks to hold the separated silica sludge; 15 dosing device for supplying lime or milk of lime; 16 water supply; 17 separating device (separator, decanter); 18 containers to hold the filtrate; 19 line to the intermediate container 13 (decilified black liquor); 20 pipe decalsified black liquor; 21 containers for absorbing sodium hydroxide solution; 22 combustion; 23 Combustion residue or melt. -
Faserfreie Dünnlauge mit einer Minimalkonzentration von 8 bis 12 % gelöster Trockensubstanz (TS) wird von der ZellstoffFabrik oder von einer der ersten Eindampfstufen zum Reaktor 4 in der Entkieselungsanlage gepumpt. Desgleichen wird über ein Gebläse 10 Rauchgas, dessen Temperatur zur Vermeidung von Feuchtigkeitsniederschlägen oberhalb des Taupunktes liegen soll, in den Reaktor 4 eingeblasen.Fiber-free thin liquor with a minimum concentration of 8 to 12% dissolved dry matter (TS) is pumped from the pulp factory or from one of the first evaporation stages to the reactor 4 in the decilification plant. Likewise, flue gas, the temperature of which should be above the dew point to prevent moisture precipitation, is blown into the reactor 4 via a
Durch die Wirkung des Rohrbogen-Begasers entsteht intensiver Kontakt der Lauge mit dem Rauchgas. Die Abgase entweichen über einen mechanischen Schaumabscheider über den Dom des Reaktionsbehälters.The action of the pipe elbow fumigator creates intensive contact between the lye and the flue gas. The exhaust gases escape via a mechanical foam separator via the dome of the reaction container.
Die behandelte Lauge verläßt den Reaktor mit dem gewünschten pH-Wert über einen Syphon und gelangt zu einer kontinuierlich arbeitenden Einrichtung 12 zur Abtrennung der ausgefällten Substanzen (Zentrifuge oder Sedimentiertrichter + Zentrifuge). Nach Abtrennung des Fällgutes von der Lauge wird das Klarfiltrat zu einem Zwischenbehälter 13 gefördert.The treated lye leaves the reactor at the desired pH via a siphon and arrives at a continuously
Der abgeschiedene Kieselsäureschlamm wird in einen Rührbehälter 14 gepumpt. Dieser wird zusätzlich mit Wasser und Branntkalk oder Kalkmilch aus einer entsprechenden Dosier-Einrichtung 15 zur Schlammwäsche beaufschlagt. Die Kalkmenge entspricht ca. dem 1,5- bis 2-fachen stöchiometrischen Bedarf, bezogen auf den Soda(Na2Co3)-Gehalt des Schlammes. Nach einer vorgegebenen Verweilzeit wird die Schlamm-Suspension abgezogen und auf einem Separator oder Dekanter 17 abzentrifugiert.The separated silica sludge is pumped into a stirred tank 14. This is additionally supplied with water and quicklime or lime milk from a
Das Klarfiltrat wird zu einem separaten Stapeltank 18 geleitet, von wo es entweder der geklärten Schwarzlauge zugegeben oder anderer Verwendung zugeführt wird. Der entwässerte, gewaschene Schlamm wird entweder direkt zur Deponie abgegeben oder einem Ofen 22 zur Nachverbrennung der restlichen, darin noch enthaltenen organischen Bestandteile zugeführt. Ein mit der Verbrennung herbeigeführter Schmelzvorgang führt nach Abkühlung der schmelze und deren Granulierung zu einem umweltfreundlichen, deponierfähigen oder weiterverarbeitbaren Abfallprodukt. Durch Steuerung des Verhältnisses Na2-SiO2-CaO während der Wäsche wird ein möglichst tiefer Schmelzpunkt eingestellt.The clear filtrate is passed to a
Ein solches Verbrennen und Einschmelzen kann z.B. in einem kohle-, gas- oder ölbefeuerten-Dampfkessel erfolgen, der zu diesem Zweck mit einer Brennkammer versehen ist, deren Boden als Schmelzbett mit Abzugsvorrichtung für die Schmelze ausgebildet ist.Such burning and melting can e.g. take place in a coal, gas or oil-fired steam boiler, which is provided for this purpose with a combustion chamber, the bottom of which is designed as a melting bed with an extraction device for the melt.
Ablauge einer Reisstroh-Zellstoff-Fabrik wird gemäß obiger Beschreibung anhand von Pilotanlagen-Versuchen zur Entkieselung behandelt.Waste liquor from a rice straw pulp factory is treated according to the above description using pilot plant trials for decilification.
-
l. Analyse der zu behandelnden Ablauge vor Eintritt in den Reaktionsbehälter 4:l. Analysis of the waste liquor to be treated before entering reaction vessel 4:
-
2. Analyse der mit Rauchgas behandelten Schwarzlauge nach der Rektion in 4. Die Mengenangaben beziehen sich auf einen Laugendurchsatz von 1.000 1/h:2. Analysis of the black liquor treated with flue gas after the rection in 4. The quantities given relate to a liquor throughput of 1,000 l / h:
-
3. Analyse der geklärten Lauge 13 nach der Zentrifugal-Abscheidung in 12:3. Analysis of the clarified
liquor 13 after centrifugal separation in 12: -
4. Analyse des in 12 abgetrennten Kieselsäure-Schlammes:Nach Aufschwämmen des Schlammes in 14 mit gleicher Gewichtsmenge Wasser und erneuter Zentrifugalabscheidung in 17 ergeben sich folgende Werte:4. Analysis of the silica sludge separated in 12:
After sponging the sludge in 14 with the same amount of water and centrifugal separation in 17, the following values result: -
5. Analyse des Klarfiltrates 18: - -5. Analysis of the clear filtrate 18: - -
-
6. Analyse des in 17 abgetrennten Schlammes:Verlustrechnung, bezogen auf 1.000 Liter eingesetzte Schwarzlauge: - 6. Analysis of the sludge separated in 17:
Loss calculation, based on 1,000 liters of black liquor used: - -
7. Organische TS7. Organic TS
-
8. Anorganische TS8. Inorganic TS
Die anorganischen Bestandteile des Schlammes aus der ersten Zentrifugierstufe 12 enthalten einen gewissen Anteil an Soda (Na2CO3). Bei Hinzugabe von Kalkmilch - Ca(OH)2 - über 15 zum Waschwasser 16 in 1,5- bis 2-fachem stöchiometrischem Verhältnis zur Menge der vorliegenden Soda wird durch den Kaustizier-Vorgang -
Natronlauge gebildet, die auf der Klarfiltratseite zum größten Teil rückgewonnen wird.Sodium hydroxide solution formed, which is largely recovered on the clear filtrate side.
Claims (13)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT83200178T ATE19416T1 (en) | 1982-03-06 | 1983-02-03 | PROCESS FOR THE CONTINUOUS REMOVAL OF SILICA FROM PULP WASTE. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19823208200 DE3208200A1 (en) | 1982-03-06 | 1982-03-06 | METHOD FOR THE CONTINUOUS REMOVAL OF SILICA FROM CELL FLUE |
| DE3208200 | 1982-03-06 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0088456A1 true EP0088456A1 (en) | 1983-09-14 |
| EP0088456B1 EP0088456B1 (en) | 1986-04-23 |
Family
ID=6157565
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP83200178A Expired EP0088456B1 (en) | 1982-03-06 | 1983-02-03 | Process for the continuous removal of silicic acid from waste liquors deriving from cellulose pulp production |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4504356A (en) |
| EP (1) | EP0088456B1 (en) |
| JP (1) | JPS58166983A (en) |
| AT (1) | ATE19416T1 (en) |
| DE (2) | DE3208200A1 (en) |
| EG (1) | EG15935A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1995017547A1 (en) * | 1993-12-23 | 1995-06-29 | Austrian Energy & Environment Sgp/Waagner-Biro Gmbh | Process for extracting pure, coarse grain silicic acid crystals |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6241390A (en) * | 1985-08-09 | 1987-02-23 | 株式会社荏原製作所 | Method and apparatus for concentrating black liquor |
| AT393284B (en) * | 1989-12-01 | 1991-09-25 | Waagner Biro Ag | METHOD FOR DESILIATING THE EXHAUST |
| US5965027A (en) | 1996-11-26 | 1999-10-12 | Microbar Incorporated | Process for removing silica from wastewater |
| US6428705B1 (en) | 1996-11-26 | 2002-08-06 | Microbar Incorporated | Process and apparatus for high flow and low pressure impurity removal |
| US5871648A (en) * | 1996-11-26 | 1999-02-16 | Environmental Chemistries, Inc. | Wastewater treatment process and apparatus for high flow impurity removal |
| US5900220A (en) * | 1997-01-16 | 1999-05-04 | Microbar Incorporated | Soda ash processing method |
| US6398964B1 (en) | 1999-08-19 | 2002-06-04 | Koch Microelectronic Service Company, Inc. | Process for treating aqueous waste containing copper and copper CMP particles |
| US6338803B1 (en) | 1999-08-30 | 2002-01-15 | Koch Microelectronic Service Co., Inc. | Process for treating waste water containing hydrofluoric acid and mixed acid etchant waste |
| US6203705B1 (en) | 1999-10-22 | 2001-03-20 | Koch Microelectronic Service Company, Inc. | Process for treating waste water containing copper |
| EP1094047A1 (en) * | 1999-10-22 | 2001-04-25 | Technische Universiteit Delft | Crystallisation of materials from aqueous solutions |
| EP1664421B1 (en) * | 2003-09-08 | 2011-12-07 | Alberta Innovates - Technology Futures | Chemimechanical desilication of nonwood plant materials |
| US20060225852A1 (en) * | 2005-04-11 | 2006-10-12 | Jan Pekarovic | Process for removing silica from cellulosic material |
| CN103693650B (en) * | 2013-12-25 | 2015-11-18 | 中盈长江国际新能源投资有限公司 | Biomass electric power plant rice hull ash and stack gas is utilized to produce the method for nano silicon and nano-calcium carbonate |
| CN113443737B (en) * | 2021-05-18 | 2022-05-13 | 中国环境科学研究院 | Process for preparing modified straw pulp papermaking white mud and process for producing gypsum through desulfurization |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1061756B (en) * | 1957-01-15 | 1959-07-23 | Pechiney Prod Chimiques Sa | Process for the production of alkali hydroxide solutions from the alkali digestion of bauxite u. like residues (red mud) |
| DE3003090A1 (en) * | 1980-01-29 | 1981-08-13 | Debendra Kumar Ph.D. Athinä Misra | Two=step alkali pulp waste liquor de:silicification - comprises carbon di:oxide addn. to ppte. silicic acid and subsequent lime addn. |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5381705A (en) * | 1976-12-24 | 1978-07-19 | Hokusan Kk | Regenerative treatment of waste liquor generated from pulping process oxidizing nonnwood plant by oxygen |
| JPS55103387A (en) * | 1979-02-05 | 1980-08-07 | Mitsubishi Heavy Ind Ltd | Silica removal from pulp digesting liqur |
| US4331507A (en) * | 1979-12-10 | 1982-05-25 | Dorr-Oliver Incorporated | Desilication in alkaline pulp processes |
-
1982
- 1982-03-06 DE DE19823208200 patent/DE3208200A1/en not_active Withdrawn
-
1983
- 1983-02-03 AT AT83200178T patent/ATE19416T1/en not_active IP Right Cessation
- 1983-02-03 DE DE8383200178T patent/DE3363132D1/en not_active Expired
- 1983-02-03 EP EP83200178A patent/EP0088456B1/en not_active Expired
- 1983-02-28 US US06/470,854 patent/US4504356A/en not_active Expired - Lifetime
- 1983-03-05 EG EG146/83A patent/EG15935A/en active
- 1983-03-07 JP JP58037213A patent/JPS58166983A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1061756B (en) * | 1957-01-15 | 1959-07-23 | Pechiney Prod Chimiques Sa | Process for the production of alkali hydroxide solutions from the alkali digestion of bauxite u. like residues (red mud) |
| DE3003090A1 (en) * | 1980-01-29 | 1981-08-13 | Debendra Kumar Ph.D. Athinä Misra | Two=step alkali pulp waste liquor de:silicification - comprises carbon di:oxide addn. to ppte. silicic acid and subsequent lime addn. |
Non-Patent Citations (2)
| Title |
|---|
| ABSTRACT BULLETIN OF THE INSTITUTE OF PAPER CHEMISTRY, Band 48, Nr. 9, März 1978, Seite 1004, Zusammenfassung Nr. 9355, Appleton, Wisconsin, USA * |
| TAPPI, JOURNAL OF THE TECHNICAL ASSOCIATION OF THE PULP AND PAPER INDUSTRY, Band 57, Nr. 7, Juli 1974, Seiten 101-104, Atlanta, GA., USA * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1995017547A1 (en) * | 1993-12-23 | 1995-06-29 | Austrian Energy & Environment Sgp/Waagner-Biro Gmbh | Process for extracting pure, coarse grain silicic acid crystals |
| CN1042359C (en) * | 1993-12-23 | 1999-03-03 | 奥地利能源及环境Sgp/瓦格纳-比罗有限公司 | Process for extracting pure, coarse grain silicic acid crystals |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0088456B1 (en) | 1986-04-23 |
| JPS58166983A (en) | 1983-10-03 |
| JPH0225674B2 (en) | 1990-06-05 |
| US4504356A (en) | 1985-03-12 |
| ATE19416T1 (en) | 1986-05-15 |
| EG15935A (en) | 1988-03-30 |
| DE3208200A1 (en) | 1983-09-08 |
| DE3363132D1 (en) | 1986-05-28 |
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