EP0150023A2 - Process for the purification of a mercerisation liquor - Google Patents

Process for the purification of a mercerisation liquor Download PDF

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EP0150023A2
EP0150023A2 EP85100263A EP85100263A EP0150023A2 EP 0150023 A2 EP0150023 A2 EP 0150023A2 EP 85100263 A EP85100263 A EP 85100263A EP 85100263 A EP85100263 A EP 85100263A EP 0150023 A2 EP0150023 A2 EP 0150023A2
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Prior art keywords
flotation
mercerizing
liquor
lye
naoh
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German (de)
French (fr)
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EP0150023B1 (en
EP0150023A3 (en
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Thomas Bechtold
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Verein Zur Forderung der Forschung u Entwicklung der Textilwirts
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Verein Zur Forderung der Forschung u Entwicklung der Textilwirts
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    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M11/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising
    • D06M11/32—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with oxygen, ozone, ozonides, oxides, hydroxides or percompounds; Salts derived from anions with an amphoteric element-oxygen bond
    • D06M11/36—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with oxygen, ozone, ozonides, oxides, hydroxides or percompounds; Salts derived from anions with an amphoteric element-oxygen bond with oxides, hydroxides or mixed oxides; with salts derived from anions with an amphoteric element-oxygen bond
    • D06M11/38—Oxides or hydroxides of elements of Groups 1 or 11 of the Periodic System

Definitions

  • the invention relates to a process for the purification of a least 20 g / l NaOH containing mercerization particularly solid impurities, wherein an addition of at least O, 1 vol .-% to 30% H 2 0 2 corresponding quantity of H 2 O 2 added to the mercerizing liquor and the impurities are separated off by flotation.
  • CH-A-604 815 describes such a process, which is aimed at soot particles, which were formed by burning away free-standing fibers before the mercerization and which got into the liquor during the mercerization, either to oxidize or to coagulate to such an extent that they from the Lye can be separated.
  • the decomposition of H 2 0 2 is catalyzed with manganese dioxide, since both the oxidation and the coagulation depend on a sufficient supply of nascent oxygen.
  • the coagulated particles are separated in a separate process step, the flotation being mentioned as the separation method.
  • finely dispersed soot particles are by no means the first of the contaminants that have to be removed from a used mercerizing liquor, in particular the problem of soot dust does not arise at all if the cotton is not seared before mercerizing.
  • a process for cleaning mercerizing lye will find a wide range of applications, especially if it is possible to remove not only fibers and dispersed dirt particles, but above all dyes, especially vat dyes, from the lye.
  • CH-PS 604 815 In contrast to the situation on which CH-PS 604 815 is based, it is generally not the lack of coagulation of finely dispersed particles that is the problem which prevents the efficient cleaning of mercerizing liquors, but rather the lack of simple and inexpensive separation processes, especially flotation processes. Even if the coagulation of the impurities obtained according to the prior art should make it possible to separate them by simple filtration, the known method has the disadvantage that the heavy metal oxide used in a later peroxide bleaching, which in itself is the preferred bleaching method, acts as a bleaching poison and is also a cost factor.
  • the invention is based on the surprising finding that, even without the use of catalysts and thus the rapid decomposition of H 2 0 2 , which is the basis of the process according to CH-A-604 815, it is possible to purify mercerizing solutions by means of H 2 0 2 is. In this case, however, the cleaning effect is based primarily on the chemical flotation which the oxygen released during H 2 0 2 decomposition brings about. It is known in principle that the gas bubbles on which every flotation process is based can be generated using peroxide compounds, but was still referred to in 1969 (cf. Reinhold Köhler in "Water, Air and Operation", page 324) as only of theoretical interest.
  • the invention is therefore based on the object of modifying a method of the type outlined in CH-A-604 815 such that on the one hand the use of bleaching poisons can be dispensed with and on the other hand an additional separation process is unnecessary. This is achieved in that the mixture of mercerizing liquor and H 2 ⁇ 2 is kept essentially free of heavy metal catalysts and allowed to stand for at least 15 minutes so that the oxygen released upon decomposition of the H 2 O 2 causes the flotation.
  • the density of the treated lye is only critical for the process insofar as the decomposition of the H 2 O 2 without catalysts only takes place sufficiently quickly in the sufficiently basic range, for example from a pH of 13.7.
  • the mercerizing solution is obtained anyway with a concentration of 40 g / 1, which corresponds to a pH value of 14.
  • it is now advantageous to thicken the alkali since evaporation of the alkali is cheaper than using large amounts of H 2 O 2 .
  • the thickening of the alkali also has the advantage that the contaminants float more easily, whereas an excessively thick alkali hinders the floating due to its high viscosity.
  • Usual cleaning methods such as centrifugation, filtration, compressed air flotation or electroflotation, are inferior to the described method, especially with higher viscosities.
  • the optimal value of the concentration is 300g / 1 or - more often - between 400 and 420 g / 1, depending on the type of the main impurities.
  • the influence of temperature on the process is comparable to that of the H 2 O 2 concentration: if the temperature is increased, the HzOz decomposes more quickly. However, this leads to turbulence in the liquid and a poorer degree of cleaning.
  • the temperature will therefore be chosen high enough not to lead to unreasonably long treatment times, but on the other hand not higher than necessary in order not to deteriorate the result of the process. Temperatures in the range between 20 ° C and 40 ° C have proven to be favorable in most cases. In the case of various crude mercerization liquors, it has proven advantageous to heat the liquor to temperatures of up to 80 ° C., preferably 40-60 ° C. for 10 minutes and then to allow it to cool to room temperature within 1-2 hours. The flotation of the contaminants occurs especially during the cooling phase.
  • a Mischbe container 3 which contains a mixer 6, unpurified lye from container 2 and H 2 0 2 from container 1 mixed.
  • the mixing time should not exceed 30 minutes, preferably 15 minutes, particularly advantageously 5 minutes. Otherwise the H 2 0 2 decomposition already begins to a noticeable extent.
  • the mixing temperature is advantageously set between 15 ° and 30 ° C. Higher temperatures up to 90 ° C can also be used.
  • the mixing time should then be as short as possible. Instead of a 30% HzOz solution, an appropriately diluted solution can be used for easier dosing.
  • the mixture is passed into the flotation tank 4. A speed control of the flotation is possible by setting a certain temperature of the lye.
  • the caustic solution itself could be heated before the HzGz admixture, between the mixing container 3 and the flotation container 4 or in the flotation container 4.
  • the mixture is passed through a heat exchanger 5 for this purpose, which can work in a known manner according to the countercurrent principle.
  • the device shown can be operated continuously or in batches. Valves 7 - 14 and peristaltic pumps 15 - 18 are used to control the process.
  • a flocculation of the alkali contaminants and above all a flotation of the undissolved contaminants takes place in the flotation container 4.
  • dissolved colored compounds are also bleached, so that cleaning does not only take place with regard to the dispersed contaminants.
  • an oxidizing flotation agent is particularly advantageous for the removal of vat dyes, since these become water-insoluble as a result of oxidation and are thus completely removed by flotation. Especially It is noteworthy that the flotation process is also able to accumulate certain dissolved compounds, such as starch, polyethylene glycols, fatty acids, in the foam layer. It is therefore not only possible to remove oxidatively but also to remove dissolved contaminants.
  • the foam layer formed during the flotation of mercerizing liquors or evaporated mercerizing liquors is sufficiently stable to be removed by conventional methods for separating flotation foams.
  • the removal is carried out by sucking air through the pump 19 and valves 9 and 12, whereby the foam is deposited in the container 20.
  • the pure liquor is pumped into the container 21 by means of the hose pump 18 via the valve 10, a remaining sediment reaches the container 22 under the influence of the vacuum pump 19 via the valve 11.
  • the equipment required for the device shown is low compared to electroflotation for lye cleaning. Compared to pressure relaxation flotation, chemical gas bubble generation according to the invention leads to incomparably higher amounts of gas available.
  • a mercerizing liquor concentrated by evaporation was used as the unpurified lye.
  • the liquor contained 402 g / l NaOH and 37.5 g / 1 Na 2 CO 3 .
  • 50 ml of alkali were vigorously mixed with 0.5 ml and 13% H 2 O 2 for one minute at 20 ° C.
  • the mixture was slowly warmed to 30 ° C in a water bath without stirring.
  • the course of the boundary between foam and purified lye is shown in Table 1.
  • the foam layer was removed by suction.
  • the cleaning effect was assessed by determining the COD value (chemical oxygen requirement for the breakdown of the impurities to CO 2 and water).
  • the dispersed impurities were removed, the remaining COD was caused by dissolved impurities.
  • the lye was cleaned in a continuously operating apparatus, as shown in the drawing. H 2 O 2 and NaOH were fed into the mixing tank by a metering pump containers were conveyed from there to the flotation tank (volume approx. 2 1). The cleaned lye was continuously removed from the container.

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Abstract

1. A process for cleaning a mercerizing lye containing at least 20 g/l NaOH, in particular in respect of solid impurities, wherein an amount of H2 O2 corresponding to the addition of at least 0.1% by volume of 30% H2 O2 is mixed with the mercerizing lye and then the impurities are separated off by flotation characterised in that the mixture of mercerizing lye and H2 O2 is kept substantially free of heavy metal catalysts and the flotation operation is performed solely with oxygen which is produced by self-decomposition of the added H2 O2 , wherein a minimum duration of 15 minutes is used.

Description

Die Erfindung bezieht sich auf ein Verfahren zur Reinigung einer mindestens 20g/l NaOH enthaltenden Mercerisierlauge insbesondere von festen Verunreinigungen, wobei eine der Zugabe von mindestens O,1 Vol.-% an 30%igem H202 entsprechende Menge an H2O2 der Mercerisierlauge zugemischt und die Verunreinigungen durch Flotation abgetrennt werden.The invention relates to a process for the purification of a least 20 g / l NaOH containing mercerization particularly solid impurities, wherein an addition of at least O, 1 vol .-% to 30% H 2 0 2 corresponding quantity of H 2 O 2 added to the mercerizing liquor and the impurities are separated off by flotation.

CH-A- 604 815 beschreibt ein derartiges Verfahren, welches darauf gerichtet ist, Rußteilchen, welche durch das Wegbrennen freistehender Fasern vor dem Mercerisieren entstanden und beim Mercerisieren in die Lauge gelangt sind, entweder zu oxidieren oder so weit zu koagulieren, daß sie aus der Lauge abgetrennt werden können. Im Sinne dieser speziellen Aufgabenstellung wird der Zerfall des H202 mit Mangandioxid katalysiert, da sowohl die Oxidation wie die Koagulation von einem hinreichenden Angebot an naszierendem Sauerstoff abhängen. Die Abtrennung der koagulierten Teilchen erfolgt in einem gesonderten Verfahrensschritt, wobei als Trennmethode u.a. die Flotation genannt ist.CH-A-604 815 describes such a process, which is aimed at soot particles, which were formed by burning away free-standing fibers before the mercerization and which got into the liquor during the mercerization, either to oxidize or to coagulate to such an extent that they from the Lye can be separated. In the sense of this special task, the decomposition of H 2 0 2 is catalyzed with manganese dioxide, since both the oxidation and the coagulation depend on a sufficient supply of nascent oxygen. The coagulated particles are separated in a separate process step, the flotation being mentioned as the separation method.

In der Praxis stehen feindispergierte Rußteilchen keineswegs an erster Stelle der Verunreinigungen, die aus einer vewendeten Mercerisierlauge entfernt werden müssen, insbesondere tritt das Problem des Rußstaubes überhaupt nicht auf, wenn ein Sengen der Baumwolle vor dem Mercerisieren unterbleibt. Ein Verfahren zur Reinigung von Mercerisierlaugen wird vor allem dann einen weiten Anwendungsbereich vorfinden, wenn es damit gelingt, nicht nur Fasern und dispergierte Schmutzteilchen, sondern vor allem Farbstoffe, insbesondere Küpenfarbstoffe, aus der Lauge zu entfernen.In practice, finely dispersed soot particles are by no means the first of the contaminants that have to be removed from a used mercerizing liquor, in particular the problem of soot dust does not arise at all if the cotton is not seared before mercerizing. A process for cleaning mercerizing lye will find a wide range of applications, especially if it is possible to remove not only fibers and dispersed dirt particles, but above all dyes, especially vat dyes, from the lye.

Im Gegensatz zu der Situation, welche CH-PS 604 815 zugrundeliegt, bildet im allgemeinen nicht die mangelnde Koagulation feindisperser Teilchen dasder wirksamen Reinigung von Mercerisierlaugen im Wege stehende Problem, sondern das Fehlen einfacher und preiswerter Abtrennverfahren, insbesondere Flotationsverfahren. Selbst wenn außerdem die nach dem Stand der Technik erzielte Koagulation der Verunreinigungen deren Abtrennung durch einfaches Filtrieren möglich ".achen sollte, hat das bekannte Verfahren den Nachteil, daß das eingesetzte Schwermetalloxid bei einer späteren Peroxid-Bleiche, welche an sich das bevorzugte Bleichverfahren darstellt, als Bleichgift wirkt und überdies einen Kostenfaktor darstellt.In contrast to the situation on which CH-PS 604 815 is based, it is generally not the lack of coagulation of finely dispersed particles that is the problem which prevents the efficient cleaning of mercerizing liquors, but rather the lack of simple and inexpensive separation processes, especially flotation processes. Even if the coagulation of the impurities obtained according to the prior art should make it possible to separate them by simple filtration, the known method has the disadvantage that the heavy metal oxide used in a later peroxide bleaching, which in itself is the preferred bleaching method, acts as a bleaching poison and is also a cost factor.

Der Erfindung liegt die überraschende Erkenntnis zugrunde, daß auch bei Verzicht auf Katalysatoren und damit einem Verzicht auf die rasche Zersetzung von H202, welche dem Verfahren nach CH-A- 604 815 zugrundeliegt, eine Reinigung von Mercerisierlaugen mittels H202 möglich ist. Der Reinigungseffekt beruht in diesem Falle jedoch primär auf der chemischen Flotation, welche der bei der H202-Zersetzung frei werdende Sauerstoff bewirkt. Daß unter Anwendung von Peroxid-Verbindungen die jedem Flotationsprozeß zugrundeliegenden Gasblasen erzeugt werden können, ist zwar prinzipiell bekannt, wurde aber noch 1969 (vgl. Reinhold Köhler in "Wasser, Luft und Betrieb", Seite 324) als nur von theoretischem Interesse bezeichnet. Insbesondere gab es keinen Hinweis darauf, daß die langsame Gasfreisetzung, welche in Mercerisierlaugen mit hohem pH-Wert bei Verzicht auf Katalysatoren erzielbar ist, ausreichen könnte, die Lauge durch Flotation zu reinigen, wogegen die bei Verwendung von Katalysatoren auftretende stürmische Gasentwicklung einen gesonderten Abtrennvorgang nicht überflüssig macht.The invention is based on the surprising finding that, even without the use of catalysts and thus the rapid decomposition of H 2 0 2 , which is the basis of the process according to CH-A-604 815, it is possible to purify mercerizing solutions by means of H 2 0 2 is. In this case, however, the cleaning effect is based primarily on the chemical flotation which the oxygen released during H 2 0 2 decomposition brings about. It is known in principle that the gas bubbles on which every flotation process is based can be generated using peroxide compounds, but was still referred to in 1969 (cf. Reinhold Köhler in "Water, Air and Operation", page 324) as only of theoretical interest. In particular, there was no indication that the slow gas release, which can be achieved in mercerizing lyes with a high pH value without the use of catalysts, could be sufficient to purify the lye by flotation, whereas the stormy gas development which occurs when using catalysts does not require a separate separation process makes redundant.

Der Erfindung liegt somit die Aufgabe zugrunde, ein Verfahren der in CH-A- 604 815 skizzierten Art so zu modifizieren, daß einerseits auf die Verwendung von Bleichgiften verzichtet werden kann und andererseits ein zusätzlicher Abtrennvorgang überflüssig wird. Dies wird dadurch erreicht, daß die Mischung von Mercerisierlauge und H2Ö2 im wesentlichen von Schwermetallkatalysatoren freigehalten und mindestens 15 Minuten lang stehen gelassen wird, damit der bei der Zersetzung des H2O2 freiwerdende Sauerstoff die Flotation bewirkt.The invention is therefore based on the object of modifying a method of the type outlined in CH-A-604 815 such that on the one hand the use of bleaching poisons can be dispensed with and on the other hand an additional separation process is unnecessary. This is achieved in that the mixture of mercerizing liquor and H 2 Ö 2 is kept essentially free of heavy metal catalysts and allowed to stand for at least 15 minutes so that the oxygen released upon decomposition of the H 2 O 2 causes the flotation.

Die Dichte der behandelten Lauge ist für das Verfahren nur insoweit kritisch, als die Zersetzung des H202 ohne Katalysatoren nur im hinreichend basischen Bereich, etwa ab einem pH-Wert von 13,7 hinreichend schnell vor sich geht. In der Praxis fällt die Mercerisierlauge ohnedies mit einer Konzentration von 40g/1, welche einem pH-Wert 14 entspricht, an. In Hinblick auf die Kosten des eingesetzten H2 O2 ist es nun günstig, die Lauge zu verdicken, da das Eindampfen der Lauge billiger kommt als der Einsatz großer Mengen H2O2. Das Eindicken der Lauge hat überdies den Vorteil, daß die Verunreinigungen leichter aufschwimmen, wogegen eine allzu dicke Lauge aufgrund ihrer hohen Viskosität das Aufschwimmen wieder behindert. Übliche Reinigungsverfahren, wie Zentrifugieren, Filtration, Druckluftflotation oder Elektroflotation, sind dem beschriebenen Verfahren insbesondere bei höheren Viskositäten unterlegen. Der optimale Wert der Konzentration liegt je nach der Art der hauptsächlich anfallenden Verunreinigungen bei 300g/1 oder - häufiger - zwischen 400 und 420 g/1.The density of the treated lye is only critical for the process insofar as the decomposition of the H 2 O 2 without catalysts only takes place sufficiently quickly in the sufficiently basic range, for example from a pH of 13.7. In practice, the mercerizing solution is obtained anyway with a concentration of 40 g / 1, which corresponds to a pH value of 14. In view of the cost of the H 2 O 2 used , it is now advantageous to thicken the alkali, since evaporation of the alkali is cheaper than using large amounts of H 2 O 2 . The thickening of the alkali also has the advantage that the contaminants float more easily, whereas an excessively thick alkali hinders the floating due to its high viscosity. Usual cleaning methods, such as centrifugation, filtration, compressed air flotation or electroflotation, are inferior to the described method, especially with higher viscosities. The optimal value of the concentration is 300g / 1 or - more often - between 400 and 420 g / 1, depending on the type of the main impurities.

Im Zusammenhang mit der Frage, welche Menge an H2O2 der Lauge zuzugeben ist, zeigt sich am deutlichsten der Unterschied zwischen der Erfindung und bekannten Verfahren: kommt es primär auf Oxidation und Koagulation an, so verbessert jede Vermehrung des Angebots an H2O2 das Ergebnis und eine obere Grenze der eingesetzten Menge ergibt sich nur aus der Abwägung der Kosten, die für eine weitere Verbesserung aufzuwenden wären. Erfindungsgemäß hingegen genügen nicht nur an sich schon geringe Mengen von H2O2, um eine weitgehende Abtrennung der Verunreinigungen durch Flotation zu bewirken. Es zeigt sich überdies, daß bei an sich möglichen Konzentrationen von H2O2 von über 5 Vol.-% an 30%igem H202 zwar eine verstärkte Sauerstoffentwicklung auftritt, die höhere Flotationsgeschwindigkeit und die Vergrößerung der auftretenden Gasblasen jedoch mit einer Verminderung des Reinigungseffektes einhergeht. Während bei bekannten technischen Flotationsverfahren Turbulenzen zum Teil absichtlich erzeugt werden, um die Gasblasen zu verteilen, können solche den Reinigungsgrad verschlechternde Turbulenzen erfindungsgemäß vermieden werden.In connection with the question of how much H 2 O 2 is to be added to the lye, the difference between the invention and known processes is most clearly evident: if oxidation and coagulation are of primary importance, any increase in the supply of H 2 O improves 2 The result and an upper limit of the amount used result only from the weighing up of the costs that would have to be expended for a further improvement. In contrast, according to the invention, not only small amounts of H 2 O 2 are sufficient in themselves to effect extensive separation of the contaminants by flotation. It is found, moreover, that in itself possible concentrations of H 2 O 2 of about 5 vol .-% to 30% H 2 0 2, although an increased oxygen evolution occurs, the higher flotation and the United Increasing the gas bubbles occurring, however, is accompanied by a reduction in the cleaning effect. While in the case of known technical flotation processes, turbulence is sometimes intentionally generated in order to distribute the gas bubbles, turbulence which deteriorates the degree of cleaning can be avoided according to the invention.

Nicht nur aus Kostengründen, sondern vor allem auch um das erzielte Ergebnis zu verbessern, empfiehlt es sich also, den Zusatz an H202 so niedrig zu halten, wie dies möglich ist, ohne die Flotationsdauer allzu sehr zu verlängern. Konzentrationen von 0,25 - 0,5 Vol.-% an 30%igem H202 haben sich in diesem Sinn als optimal herausgestellt.Not only for cost reasons, but above all to improve the result achieved, it is therefore advisable to keep the addition of H 2 0 2 as low as possible without extending the flotation period too much. Concentrations of 0.25-0.5% by volume of 30% H 2 0 2 have been found to be optimal in this sense.

Der Einfluß der Temperatur auf den Verfahrensablauf ist jenem der H2O2 -Konzentration vergleichbar.: erhöht man die Temperatur, folgt eine raschere Zersetzung des HzOz. Hiedurch kommt es jedoch zu Turbulenzen in der Flüssigkeit und zu einem verschlechterten Reinigungsgrad. Man wird die Temperatur somit hoch genug wählen, um nicht auf unzumutbar lange Behandlungsdauern zu kommen, andererseits aber nicht höher als nötig, um das Verfahrensergebnis nicht zu verschlechtern. Temperaturen im Bereich zwischen 20°C und 40°C haben sich in den meisten Fällen als günstig herausgestellt. Bei verschiedenen Rohmercerisationslaugen hat es sich als günstig erwiesen, die Lauge fürlO min auf Temperaturen bis zu 80°C, vorzugsweise 40 - 60°C zu erwärmen und anschließend innerhalb von 1 - 2 Stunden auf Raumtemperatur abkühlen zu lassen. Die Flotation der Verunreinigungen tritt insbesondere während der Abkühlphase ein.The influence of temperature on the process is comparable to that of the H 2 O 2 concentration: if the temperature is increased, the HzOz decomposes more quickly. However, this leads to turbulence in the liquid and a poorer degree of cleaning. The temperature will therefore be chosen high enough not to lead to unreasonably long treatment times, but on the other hand not higher than necessary in order not to deteriorate the result of the process. Temperatures in the range between 20 ° C and 40 ° C have proven to be favorable in most cases. In the case of various crude mercerization liquors, it has proven advantageous to heat the liquor to temperatures of up to 80 ° C., preferably 40-60 ° C. for 10 minutes and then to allow it to cool to room temperature within 1-2 hours. The flotation of the contaminants occurs especially during the cooling phase.

Weitere Einzelheiten der Erfindung werden anschließend anhand der Zeichnung beschrieben, in welcher eine Einrichtung zur Durchführung des Verfahrens schematisch dargestellt ist.Further details of the invention are described below with reference to the drawing, in which a device for performing the method is shown schematically.

Wie in der Zeichnung angedeutet, wird in einem Mischbehälter 3, der einen Mischer 6 enthält, ungereinigte Lauge aus dem Behälter 2 und H202 aus dem Behälter 1 gemischt. Die Mischdauer sollte 30 Minuten, vorzugsweise 15 Minuten, besonders vorteilhaft 5 Minuten, nicht überschreiten. Ansonsten beginnt die H202 Zersetzung bereits in merklichem Ausmaß. Die Mischtemperatur wird vorteilhaft zwischen 15° und 30°C eingestellt. Auch höhere Temperaturen bis 90°C sind verwendbar. Die Mischungszeit sollte dann aber so kurz wie möglich gewählt werden. Anstelle einer 30%igen HzOz-Lösung kann zur leichteren Zudosierung eine entsprechend verdünnte Lösung verwendet werden. Nach der H2O2-Zudosierung wird die Mischung in den Flotationsbehälter 4 geleitet. Eine Geschwindigkeitssteuerung der Flotation ist durch Einstellung einer bestimmten Temperatur der Lauge möglich. Eine Erwärmung der Lauge könnte an sich vor der HzGz-Zumischung, zwischen Mischbehälter 3 und Flotationsbehälter 4 oder im Flotationsbehälter 4 erfolgen. Im vorliegenden Fall wird zu diesem Zweck die Mischung durch einen Wärmetauscher 5 geführt, welcher in bekannter Weise nach dem Gegenstromprinzip funktionieren kann.As indicated in the drawing, is in a Mischbe container 3, which contains a mixer 6, unpurified lye from container 2 and H 2 0 2 from container 1 mixed. The mixing time should not exceed 30 minutes, preferably 15 minutes, particularly advantageously 5 minutes. Otherwise the H 2 0 2 decomposition already begins to a noticeable extent. The mixing temperature is advantageously set between 15 ° and 30 ° C. Higher temperatures up to 90 ° C can also be used. The mixing time should then be as short as possible. Instead of a 30% HzOz solution, an appropriately diluted solution can be used for easier dosing. After the H 2 O 2 addition, the mixture is passed into the flotation tank 4. A speed control of the flotation is possible by setting a certain temperature of the lye. The caustic solution itself could be heated before the HzGz admixture, between the mixing container 3 and the flotation container 4 or in the flotation container 4. In the present case, the mixture is passed through a heat exchanger 5 for this purpose, which can work in a known manner according to the countercurrent principle.

Der Betrieb der dargestellten Einrichtung kann kontinuierlich oder chargenweise erfolgen. Zur Steuerung des Verfahrens dienen dabei Ventile 7 - 14 und Schlauchpumpen 15 - 18.The device shown can be operated continuously or in batches. Valves 7 - 14 and peristaltic pumps 15 - 18 are used to control the process.

Im Flotationsbehälter 4 findet neben einer teilweisen Oxidation der Laugenverunreinigungen eine Flockung derselben und vor allem eine Flotation der ungelösten Verunreinigungen statt. Neben einer Entfernung der dispergierten Verunreinigungen werden auch gelöste gefärbte Verbindungen gebleicht, sodaß eine Reinigung nicht nur in Hinblick auf die dispergierten Verunreinigungen eintritt.In addition to a partial oxidation of the alkali contaminants, a flocculation of the alkali contaminants and above all a flotation of the undissolved contaminants takes place in the flotation container 4. In addition to removing the dispersed contaminants, dissolved colored compounds are also bleached, so that cleaning does not only take place with regard to the dispersed contaminants.

Insbesondere für die Entfernung von Küpenfarbstoffen ist der Einsatz eines oxidierenden Flotationsmittels vorteilhaft, da diese durch Oxidation wasserunlöslich werden und so durch Flotation vollständig entfernt werden. Besonders bemerkenswert ist, daß das Flotationsverfahren auch in der Lage ist, bestimmte gelöste Verbindungen,wie z.B. Stärke, Polyethylenglykole, Fettsäuren, in der Schaumschicht anzureichern. Es ist daher nicht nur eine oxidative Entfernung sondern auch eine flctative Entfernung gelöster Verunreinigungen moglich.The use of an oxidizing flotation agent is particularly advantageous for the removal of vat dyes, since these become water-insoluble as a result of oxidation and are thus completely removed by flotation. Especially It is noteworthy that the flotation process is also able to accumulate certain dissolved compounds, such as starch, polyethylene glycols, fatty acids, in the foam layer. It is therefore not only possible to remove oxidatively but also to remove dissolved contaminants.

Die bei der Flotation von Mercerisierlaugen bzw. eingedampften Mercerisierlaugen entstehende Schaumschicht ist ausreichend stabil, um durch übliche Verfahren zur Abtrennung von Flotationsschäumen entfernt zu werden. Die Entfernung erfolgt, indem über die Pumpe 19 und Ventile 9 und 12 Luft abgesaugt wird, wodurch der Schaum in den Behälter 20 abgelagert wird.The foam layer formed during the flotation of mercerizing liquors or evaporated mercerizing liquors is sufficiently stable to be removed by conventional methods for separating flotation foams. The removal is carried out by sucking air through the pump 19 and valves 9 and 12, whereby the foam is deposited in the container 20.

Die Reinlauge wird mittels der Schlauchpumpe 18 über das Ventil 10 in den Behälter 21 gepumpt, ein verbleibender Bodensatz gelangt unter dem Einfluß der Vakuumpumpe 19 über das Ventil 11 in den Behälter 22.The pure liquor is pumped into the container 21 by means of the hose pump 18 via the valve 10, a remaining sediment reaches the container 22 under the influence of the vacuum pump 19 via the valve 11.

Ein Zusatz von speziellen Sammlern oder Schäumern erübrigt sich, was besonders für eine Wiederverwertung der Lauge von grcßer Eedeutung ist, da alle zugesetzten Hilfsmittel potentielle Störungsfaktoren darstellen. Durch den Zusatz anionischer Tenside, wie Dodecylhydrogensulfat-Na-Salz, kationischer Tenside, wie Hyamin 1622, oder nichtionischer Tenside, wie Nonylphenolpolyethylenglokolether kann jedoch eine deutliche Verbesserung der Flotierbarkeit erzielt werden. Auch die Flotationsgeschwindigkeit steigt in bemerkenswerten Maße an.There is no need to add special collectors or foaming agents, which is of particular importance for the recycling of the lye, since all the auxiliaries added represent potential disruptive factors. However, the addition of anionic surfactants, such as dodecyl hydrogen sulfate sodium salt, cationic surfactants, such as Hyamin 1622, or nonionic surfactants, such as nonylphenol polyethylene glycol ether, can significantly improve the floatability. The flotation speed also increases remarkably.

Der apparative Aufwand der dargestellten Einrichtung ist im Vergleich zur Elektroflotation zur Laugenreinigung gering. Im Vergleich zur Druckentspannungsflotation führt die chemische Gasblasenerzeugung nach der Erfindung zu ungleich höheren verfügbaren Gasmengen.The equipment required for the device shown is low compared to electroflotation for lye cleaning. Compared to pressure relaxation flotation, chemical gas bubble generation according to the invention leads to incomparably higher amounts of gas available.

Anwendungsbeispiel 1 (diskontinuierlich):Application example 1 (discontinuous):

Als ungereinigte Lauge wurde eine durch Eindampfen aufkonzentrierte Mercerisierablauge verwendet. Die Lauge enthielt 402 g/l NaOH und 37,5 g/1 Na2CO3 . 50 ml Lauge wurden bei 20°C mit 0,5 ml und 13% igem H2O2 eine Minute lang heftig vermischt. Die Mischung wurde in einem Wasserbad ohne Rühren langsam auf 30°C erwärmt. Der zeitliche Verlauf der Grenze zwischen Schaum und gereinigter Lauge ist in Tabelle 1 dargestellt.

Figure imgb0001
A mercerizing liquor concentrated by evaporation was used as the unpurified lye. The liquor contained 402 g / l NaOH and 37.5 g / 1 Na 2 CO 3 . 50 ml of alkali were vigorously mixed with 0.5 ml and 13% H 2 O 2 for one minute at 20 ° C. The mixture was slowly warmed to 30 ° C in a water bath without stirring. The course of the boundary between foam and purified lye is shown in Table 1.
Figure imgb0001

Die Schaumschicht wurde durch Absaugen entfernt. Der Reinigungseffekt wurde durch Bestimmung des COD-Wertes (chem. Sauerstoffbedarf für den Abbau der Verunreinigungen zu CO2 und Wasser) beurteilt.The foam layer was removed by suction. The cleaning effect was assessed by determining the COD value (chemical oxygen requirement for the breakdown of the impurities to CO 2 and water).

COD ungereinigte Lauge 70,4 g/1 K2Cr2O7 - 100 % COD gereinigte Lauge 31,3 g/1 -"- - 44,5 %COD unpurified alkali 70.4 g / 1 K 2 Cr 2 O 7 - 100% COD purified alkali 31.3 g / 1 - "- - 44.5%

Die dispergierten Verunreinigungen wurden entfernt, der verbleibende COD-Wert wurde durch gelöste Verunreinigungen hervorgerufen.The dispersed impurities were removed, the remaining COD was caused by dissolved impurities.

Anwendungsbeispiel 2Example of use 2

Verwendet wurde eine wiedereingedampfte Mercerisierlauge mit folgenden Daten:

  • NaOH 438,8 g/1
  • Na2C03 20,1 g/l
  • COD 49,9 g/1 trüb, dunkel
A re-evaporated mercerizing liquor was used with the following data:
  • NaOH 438.8 g / 1
  • Na 2 CO 3 20.1 g / l
  • COD 49.9 g / 1 cloudy, dark

Die Lauge wurde in einer kontinuierlich arbeitenden Apparatur, wie sie in der Zeichnung dargestellt ist, gereinigt. H2O2 und NaOH wurden durch eine Dosierpumpe in den Mischbehälter gefördert und gelangten von dort in den Flotationsbehälter (Vol. ca. 2 1). Die gereinigte Lauge wurde dem Behälter laufend entnommen.The lye was cleaned in a continuously operating apparatus, as shown in the drawing. H 2 O 2 and NaOH were fed into the mixing tank by a metering pump containers were conveyed from there to the flotation tank (volume approx. 2 1). The cleaned lye was continuously removed from the container.

Exp. Daten des Versuchs: Gereinigte Laugenmenge: 3500 ml zudos. H2O2 Volumen : 1 Vol.-% Laugentemperatur: 30°C Ausbeute: 88% COD-Reinlauge: 32 g/1 COD-Schaum: 142 g/1 Leistung der Apparatur: 4,3 1/h Behandlungsdauer: 30 minExp. Data of the experiment: purified amount of alkali: 3500 ml added. H 2 O 2 volume: 1% by volume alkali temperature: 30 ° C yield: 88% COD pure alkali: 32 g / 1 COD foam: 142 g / 1 performance of the apparatus: 4.3 1 / h treatment time: 30 min

Die in der Reinlauge verbleibenden Fremdstoffe machten diese farblos bis leicht gelblich und stellten somit kein Hindernis für deren Wiederverwendung dar.The foreign substances remaining in the pure liquor made them colorless to slightly yellow and therefore did not constitute an obstacle to their reuse.

Claims (5)

1. Verfahren zur Reinigung einer mindestens 20 g/1 NaOH enthaltenden Mercerisierlauge insbesondere von festen Verunreinigungen, wobei eine der Zugabe von mindestens 0,1 Vol.-% an 30%igem H202 entsprechende Menge an H2O2 der Mercerisierlauge zugemischt und die Verunreinigungen durch Flotation abgetrennt werden, dadurch gekennzeichnet, daß die Mischung von Mercerisierlauge und H202 im wesentlichen von Schwermetallkatalysatoren freigehalten und mindestens 15 Minuten lang stehen gelassen wird, damit der bei der Zersetzung des H2O2 freiwerdende Sauerstoff die Flotation bewirkt.1. A method for cleaning a minimum of 20 g / 1 NaOH containing mercerization particularly solid impurities, wherein an addition of at least 0.1 vol .-% to 30% H 2 0 2 mixed in appropriate amount of H 2 O 2 the mercerization and the impurities are separated by flotation, characterized in that the mixture of mercerizing liquor and H 2 0 2 is kept essentially free of heavy metal catalysts and is left to stand for at least 15 minutes so that the oxygen released during the decomposition of the H 2 O 2 causes the flotation . 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Mercerisierlauge vor der Mischung mit H202 auf einen Gehalt von 140 - 475 g/1 NaOH, vorzugsweise 400 - 420 g/1 NaOH, eingedickt wird.2. The method according to claim 1, characterized in that the Mercerisierlauge before mixing with H 2 0 2 to a content of 140 - 475 g / 1 NaOH, preferably 400 - 420 g / 1 NaOH, is thickened. 3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der Mercerisierlauge von 0,1 - 5,0 Vol.-%, vorzugsweise von 0,25 - 0,5 Vol.-% HzOz, bezogen auf 30%iges H2O2, zugemischt wird.3. The method according to claim 1 or 2, characterized in that the Mercerisierlauge from 0.1 - 5.0 vol .-%, preferably from 0.25 - 0.5 vol .-% HzOz, based on 30% H 2 O 2 , is added. 4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Flotation bei Temperaturen zwischen 20°C und 80°C, vorzugsweise zwischen 20°C und 40°C erfolgt.4. The method according to any one of claims 1 to 3, characterized in that the flotation takes place at temperatures between 20 ° C and 80 ° C, preferably between 20 ° C and 40 ° C. 5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die Mischung von Mercerisierlauge und H2O2 mindestens eine Stunde lang stehen gelassen wird.5. The method according to any one of claims 1 to 4, characterized in that the mixture of mercerizing liquor and H 2 O 2 is left to stand for at least one hour.
EP19850100263 1984-01-19 1985-01-12 Process for the purification of a mercerisation liquor Expired EP0150023B1 (en)

Applications Claiming Priority (2)

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AT0016284A AT392097B (en) 1984-01-19 1984-01-19 METHOD FOR CLEANING MERCERIZING LYE
AT162/84 1984-01-19

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EP0150023A2 true EP0150023A2 (en) 1985-07-31
EP0150023A3 EP0150023A3 (en) 1986-02-12
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US5837977A (en) * 1995-06-07 1998-11-17 Quiclave, L.L.C. Microwave heating container with microwave reflective dummy load

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CN111847626B (en) * 2020-07-27 2022-08-05 南昌航空大学 Use method of device for pretreating complex heavy metal in electroplating cleaning wastewater by catalytic oxidation method

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Publication number Priority date Publication date Assignee Title
DE2521157A1 (en) * 1975-05-13 1976-11-25 Ags Ausruestungsgesellschaft F METHOD AND DEVICE FOR CLEANING MERCERIZING LIQUID
DE2641094A1 (en) * 1976-08-24 1978-03-02 Bbc Brown Boveri & Cie METHOD OF CLEANING AN ALKALINE SOLUTION AND EQUIPMENT FOR CARRYING OUT THE PROCEDURE

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2521157A1 (en) * 1975-05-13 1976-11-25 Ags Ausruestungsgesellschaft F METHOD AND DEVICE FOR CLEANING MERCERIZING LIQUID
DE2641094A1 (en) * 1976-08-24 1978-03-02 Bbc Brown Boveri & Cie METHOD OF CLEANING AN ALKALINE SOLUTION AND EQUIPMENT FOR CARRYING OUT THE PROCEDURE

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5837977A (en) * 1995-06-07 1998-11-17 Quiclave, L.L.C. Microwave heating container with microwave reflective dummy load

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EP0150023B1 (en) 1988-12-21
EP0150023A3 (en) 1986-02-12
AT392097B (en) 1991-01-25
DE3566914D1 (en) 1989-01-26

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