DE19600774A1 - Removal of cyanide from process water - Google Patents

Abstract

A process and device are disclosed for removing cyanide from process water from the foodstuff industry. The process water is recirculated and cyanide is continuously stripped from the process water in a stripping column (3). In a second stage, the cyanide contained in the stripping gas is destroyed by oxidation. Process water to be disposed of can be further purified by pursuing the stripping process in order to conform to permissible limit values.

Description

The present invention relates to a method and an apparatus for Removal of cyanides from industrial process water.

Cyanides are the salts of hydrocyanic acid HCN. They contain the colorless, toxic anion CN⁻. Because of the high toxicity of the cyanide its removal and destruction is of particular importance if it in the context of industrial production processes or in the form of Contaminated sites arise. There are therefore various methods in the prior art to destroy the cyanides or to extract them from a Carrier material known.

Biological and chemical can be used to destroy cyanides Use procedure. In the technical application, in particular chemical processes such as oxidative destruction (with hydrogen peroxide, ozone, hypochlorite or by alkaline chlorination), the electro chemical fission, destruction by ionizing radiation and a chemical conversion with aldehydes and subsequent hydrolysis described.  

The oxidative destruction of cyanides with chlorine or hypochlorite Procedure is a widespread procedure. Through the use of Hypochlorite salts cyanide is first in cyanate and then further in Nitrogen and ammonium in parallel. Because of problematic side reactions (absorbable organic halogen compounds: AOX formation) and intermediate products (e.g. Chlorine cyan) was increasingly sought after alternatives.

One such alternative is the use of hydrogen peroxide. This solves the problems of the hypochlorite process. By a Process combinations with monopersulfate can be very low Residual concentrations and the destruction of cyanide complexes. The reaction initially proceeds to the cyanate, which with excess Oxidizing agents reacted further to nitrogen and carbon dioxide.

By using UV light, the reaction of the hydrogen peroxide be optimized so that the speed is higher and the Oxidant consumption is lower. The reaction proceeds with the addition of the Oxidizing agent at pH values around 10 in batches Reaction kettles within a few minutes.

Cyanides can also be found in the air in the presence of catalysts such as copper or activated carbon and oxygen as reactants effectively in nitrogen and Carbon dioxide can be converted. Another option is the Combination of aldehydes / hydrogen peroxide. By reacting with Aldehydes, the cyanide is converted into corresponding nitriles. The use of formaldehyde is described in particular. In the The reaction initially produces glyconitrile, which is slowly split hydrolytically  becomes. The reaction is accelerated by hydrogen peroxide, and it formate and ammonium.

The oxidative cyanide destruction is e.g. B. described in DE-42 14 974 (Destruction of cyanide with hydrogen peroxide and UV activation), U.S. 5,246 598 (catalytic oxidation with peroxides), US 3,920,547 (oxidation of Cyanides with ozone), US-3,617,567 (oxidation of cyanides with Hydrogen peroxide and a copper catalyst).

Electrochemical is also used in certain applications Destruction of cyanide possible. This involves electrolysis of the cyanide-containing ones Metal complexes in the wastewater and a related destruction of the Cyanide to CO₂ and N₂ at the anode and a metal deposition at the Cathode. In principle, however, the method is only used in the Metalworking or in electroplating interesting because the recovered metals make the process inexpensive. Such Procedures are such. For example, described in U.S. 4,145,268 and U.S. 3,755,932.

Another variant is the hydrolytic destruction of cyanides. she runs through a water deposit to formate and Ammonium. The reaction is carried out by temperature, pressure or a suitable pH (<10) accelerated. At a temperature of approx. 190 ° C and the corresponding saturation pressure of approx. 30 bar in one Autoclaves completely saponify the cyanides in a short time. By Effective heat recovery can be an inexpensive alternative to the oxidation processes can be achieved.  

A similar process for cyanide destruction is used in hydrothermal Destruction used. The cyanides are initially around at temperatures 200 ° C released with oxygen from their metal complexes and then split hydrolytically. The method is particularly the case with Treatment of iron-cyanide complexes interesting.

There are currently biological processes with microorganisms. still in Research and development stage. As areas of application stand out Waste water or contaminated solids from which the cyanides are considered pure there is organic contamination. The exception is enzymatic processes in which at least partially metal or complex water can be decontaminated with cyanides.

In the treatment of cyanides, the problem often arises in practice, that the cyanides are distributed in a carrier medium that is not directly the undergo chemical or other treatment to destroy cyanide can be. A typical example of this is the presence of Cyanides in contaminated soil. Here, the entire floor can not appropriate oxidizing agents are exposed. In these cases So-called stripping methods can be used, in which a - usually gaseous - stripping fluid through the cyanide-contaminated sample is passed, whereby there is a transfer (solution) of the cyanides in the Stripping fluid is coming.

Stripping is used to remove a number of volatile substances such as ammonia, cyanide, chlorinated hydrocarbon (CHC), benzene / toluene / xylene (BTX) and hydrogen sulfide. In particular, procedures for  Groundwater remediation, soil air extraction and for the elimination of Ammonium nitrogen is already being used on an industrial scale.

An example of this is the air stripping of the BTX from wastewater and subsequent oxidation with a hydrophobic catalyst at 90-150 ° C directly in the air flow. When stripping the CHC from the wastewater the CKW usually carried out adsorbed on activated carbon and thus enriched. There are also models with stripping cascades for use volatile contamination proposed.

Stripping can also remove unwanted odors or Remove flavors that are then adsorbed on activated carbon or be destroyed by oxidation.

Groundwater stripping is mostly used for volatile substances CHC and BTX contamination. Process engineering exists for everyone ex situ approaches from a packed column, in which an intensive Contact with air the pollutants are expelled, and one downstream activated carbon adsorption.

An in situ purification of the groundwater is also possible Soil air extraction (floor stripping) possible, the floor withdrawn from volatile contaminants and redissolved from the groundwater will. In addition to cleaning the floor, Groundwater remediation achieved.

Another application is stripping ammonium nitrogen. Ammonium is particularly in the wastewater of the food industry  (Phytonutrients, fertilizer residues) a problem because the prescribed limit value (direct discharge VO) of 10 mg / l frequently is exceeded. Stripping with air or steam is required for elimination well suited and described several times in the literature. Basically can the ammonium nitrogen from basic liquids (pH 10-11) as volatile ammonia are expelled. This is both air steam is also used. Steam is due to the smaller one Quantity ratio (approx. 100 kg / m³ wastewater) to air (1000 m³ / m³ Waste water) advantageous, but more energy-intensive. The ammonia is either catalytically oxidized in the individual processes (N₂ + water), condensed or collected in acid and possibly obtained as a valuable substance (Fertilizer).

The literature also describes two processes in which cyanides carried out by stripping and then destroyed.

In the cyan-CAT process (Jola, Plating and Surface Finishing, 42-44, 1976) the cyanides with the addition of sulfuric acid (pH 3-4 for free and pH 1-3 in the case of complex-bound cyanides) is stripped out with air and oxidized directly in the stripping air by a catalyst at 300 to 400 ° C. The catalyst contains a composition of precious metals, which is not closer to be discribed. The strongly exothermic reaction is maintained via a Heat recovery almost itself, so that only the initial heating with a fuel must be generated. The treated cyanide solutions usually come from electroplating plants or are available as waste water and have a very high cyanide concentration (typically 20 g / l).  

With cyanide stripping with CO₂ air (Müller-Erlwein, Angerer, Chem.-Ing.-Tech. 65, 747-749, 1993) is by stripping with a CO₂ / air mixture (1: 1) the cyanide from soils or - experimentally - from solutions separated and at the same time by atmospheric oxygen at room temperature oxidized. The procedure is for the in situ treatment of contaminated Floors have been developed. The reduction of an initial concentration of 1000 mg / l to 5 mg / l required the test to be stripped for several hours solution. The reduction in the cyanide content showed a strong dependency on the type of binding of the CN⁻ ion (easily releasable vs. complex) and was therefore taken through additional measures such as cooling accelerates.

Another area of application for cyanide removal is the Food technology. This creates cyanide-containing wastewater especially when debittering raw materials. So z. B. at the Production of raw Persipan paste to debitter apricot kernels. This water is added to the cyanide - and thus the bitter Taste - to drain. This produces high levels of cyanides in the Water. The concentrations can be between 20 and 300 mg / l CN⁻ vary. For state-of-the-art systems (MVM Konsult AB, Solna, Sweden; Marcia Engineering A / 5, Noerre Aaby, Denmark) the water used for the debittering of the kernels after completion of the Leaching discarded as waste water. It is because of the high Detoxify cyanide content first. This happens through oxidative Destruction of the cyanide. A disadvantage of this method according to the prior art Technology is that it consumes large amounts of process water will. These must also be cleaned to the extent that they are in all chemical parameters the legal requirements for  Correspond to waste water discharge. The cyanide concentration should be below 1 mg / l (ATV guidelines).

The present invention has compared to the described state of the Technology set the task, a method and an apparatus for To provide with which industrial process water contaminated with cyanide can be freed from the cyanide in a simple and inexpensive manner. Here Reduced quantities are intended as the starting products of the cleaning process of waste water and exhaust air.

This object is achieved by a method in which one

• A) the process water in the cycle between the application process and Cyanide removal is carried out
• B) the process water may be physically treated,
• C) the process water in a stripping column of stripping gases is flowed through, in which the cyanides accumulate, and
• D) if necessary, the process water several times in a subcircuit Treatment steps B) and / or C) is subjected.

The inventive method is characterized first of all by the fact that Process water is circulated. It therefore stands that underlying application process, e.g. B. a bitterness in the Persipan production, repeatedly available. In contrast to the stand In technology, a batch of process water does not fall completely as Wastewater on after debittering has been performed once. So that Process water can fulfill its task in the application process the circuit is continuously cleaned of the substances  be from the application process and in the process water enrich. It can be z. B. are solids that are in Process step B) physically separated. In particular, must however, the cyanides are removed from the process water. this happens in the method according to the invention in step C) by stripping the cyanide with suitable stripping gases. This will Cyanide content in the process water in a quick and extremely simple way Reduced values that the process water for a new use in Make the application process usable. In particular, it is not necessary the cyanide content to values by a disproportionate effort lower that an introduction of the process water according to the legal Would allow regulations in the wastewater. Nevertheless, one can Purification of the process water to concentrations below 20 mg / l CN⁻ can be achieved by stripping in a short time. With the stripping process is a targeted separation of the cyanide (with subsequent Concentration and destruction) possible without accompanying substances of the Process water must be treated or chemical or biological Side reactions take place and residues of reagents remain. With the method according to the invention can therefore be the effort for Destruction of cyanide in the process water compared to the processes according to the prior art technology can be significantly simplified.

In a preferred form of the process, the cyanide-laden ones Stripping gases a further treatment step to destroy the cyanides subject.

The process water can several times in a subcircuit Treatment steps B) and / or C) are subjected. This happens,  by circulating it bypassing the application process. Such a sub-circuit may be required if the application process is interrupted or temporarily requires less process water. In In this case, however, the stripping process can continue will.

The cyanides that have accumulated in the stripping gases will destroyed according to the invention in a further treatment step. Here makes itself noticeably noticeable that the cyanides to be destroyed in one Gas and not in a large amount of process water together with various other accompanying substances.

Stripping gases which are suitable in the context of the invention are air, in particular compressed air, carbon dioxide and / or nitrogen specified. This On the one hand, gases are technically unproblematic and inexpensive, secondly, they have sufficient absorption capacity for gaseous gases Cyanides.

The physical treatment of the process water in treatment step B) can e.g. B. consist in that heavy and / or solid components in one Centrifuge centrifuged. As part of Persipan's manufacturing such physical processing z. B. necessary to contain To separate suspended particles or microorganisms.

A further physical processing according to the invention can be carried out by Filtration, preferably micro, ultra and / or nanofiltration take place. Furthermore, the process water can be irradiated with UV light, in particular  as aftertreatment of a centrifugation to increase the disinfection of the To achieve process water.

The destruction of the cyanides in the stripping gases preferably takes place on chemical way. In particular, according to the invention, a three-stage Procedure applied consisting of the steps

• E1) Washing out the cyanides from the stripping gas by washing the gas with lye, preferably sodium hydroxide solution NaOH,
• E2) treatment of the cyanide enriched in the alkali with Hydrogen peroxide in a basic environment,
• E3) Oxidation of the treated cyanide to nitrogen and carbon dioxide by adding hydrogen peroxide and / or monopersulfate Reaction initially in a basic environment and subsequent final reaction in an acidic environment and / or by adding ozone as an oxidizing agent.

This type of process control can process large quantities of process water be detoxified, and the cyanide is leached in a small amount collected.

Treatment step E2) is preferably greater at a pH 10 instead of and the treatment step E3) initially at a pH value greater 10 and then at a pH of around 6. It is possible to Oxidation reactions with hydrogen peroxide in treatment stages E2), E3) to accelerate by irradiation with UV light.

In the described destruction of the cyanides, preference is given to the Stripping air circulated the wash liquor. With the The procedure according to the invention is efficient and inexpensive  Destruction of the cyanides possible. In particular, it is ensured that the Stripping gases are freed of cyanide to the extent that they are purified exhaust air can leave the facility.

Through the circulation of the wash liquor is also achieved here that Amount of waste water is minimized.

For the destruction of the cyanides in the stripping gas in process step E) in addition to the procedure described above, all others from the Methods known in the art are possible. In particular, a Oxidation of the cyanides with oxygen take place, preferably copper or activated carbon can be used as a catalyst. Likewise, initially a conversion of the cyanides with aldehydes, preferably with Formaldehyde take place, the conversion products then be hydrolyzed. An additional use of Hydrogen peroxide can be beneficial.

The stripping gas can be switched on or in the stripping column in process step C) go through several times. Usually, however, it will not be afterwards be saturated with cyanides. It is therefore possible to pass the stripping gas through a to conduct the second fluid loaded with cyanides, and from this further cyanides to extract. The second fluid can in particular be trade a lot that is no longer used in a process cycle, but should only be freed from cyanides as much as possible, e.g. B. um can then be discharged into the wastewater. It can it only makes sense to remove the cyanides by stripping up to a certain cyanide content and the residual cyanide  then using the methods described above, e.g. B. a chemical Oxidation.

The second fluid, cleaned with the stripping gas, may be especially to process water to be disposed of from the Act actual application process according to treatment level A). For it it is possible that this process water is completely renewed from time to time must become. It is then based on its chemical load Clean values that allow discharge into the wastewater. With the The procedure described can be such process water to be disposed of pass through the stripping gases used anyway and thereby being freed from cyanides. Such disposal can be done without special procedural effort or further use of materials in integrate the existing system.

The invention also relates to a device for performing the above described inventive method. This device is thereby characterizes that in the cycle of the process water different Components are arranged, which flows through the process water will. These components include:

• a) an installation for carrying out the application process,
• b) if necessary, one or more buffer tanks for the process water,
• c) a centrifuge if necessary,
• d) if necessary, a filter, preferably a micro, ultra and / or nanofilter,
• e) if necessary, a UV radiation station for disinfection,
• f) a stripping column with a supply line for stripping gas,
• g) a circulation pump,  
• h) if necessary, an adjustable bypass to circumvent the application process.

This device according to the invention allows with relatively few and simple components to carry out the invention Procedure and the achievement of the associated advantages. That's why through the circular process in particular to a considerable saving Process water.

The invention also relates to a device for carrying out the inventive method for the destruction of the cyanides in the Stripping gases. This device is characterized in that

• a) it contains an exhaust air scrubber which contains the stripping gases contaminated with cyanide are supplied and the cleaned exhaust air leaves, and the one inlet and Drain for the wash liquor contains
• b) behind the said wash liquor outlet a treatment container for the destruction of the cyanide is ordered
• c) the treatment tank is connected to chemical tanks, and
• d) if necessary, the outflow of the treatment container in a circuit with the The wash water inlet of the scrubber is connected.

The treatment container can preferably be provided with a Neutralization reactor, which in turn is connected to chemicals container (acid, alkali) is connected. The neutralization reactor has thereby an exit for purified wastewater, which it after completion of the Neutralization reaction leaves. By connecting this reactor behind the treatment tank it is possible to add the wash liquor if necessary to dispose. This lye cannot be discharged directly into the wastewater,  because it is too alkaline. Your pH must therefore be controlled in a controlled manner the neutralization reactor to a pH between 5 and 6 will.

The described device according to the invention for destroying the cyanides achieved in the stripping gases with relatively few and simple Components an efficient implementation of the invention Procedure. It thus achieves the advantages associated with the process. In particular, it is also here due to the circulation of the wash liquor possible to minimize the amount of waste water.

In a further embodiment of the invention, the device for Destruction of the stripping gas supplied by the cyanide is first caused by another Stripping column are passed before it reaches the scrubber. This stripping column can preferably be used with chemical storage containers be linked to a defined setting of different chemical Parameters such as B. allow the pH. The advantage of the arrangement Another stripping column is that there is a cyanide in it Fluid can be found by the stripping gas flowing through is cleaned. This stripping gas can be used in a previous process stage may already be cyanide contaminated, however it usually has is far from reaching the saturation limit for cyanides, so it can also extract cyanides in the further stripping column. in the Within the scope of the invention it is also possible to insert the second stripping column supply unloaded stripping gas.

So that in the upstream stripping column described above z. B. the Disposal of the process cycle water from the application process of time  can be done at the time, there is preferably an opening and closing final connection from this application process to the stripping column.

The method according to the invention and the Device according to the invention in the food industry, especially in Relation to debittering processes, as they are especially the case with The bitterness of kernels arises in the manufacture of Persipan.

In the following the invention is explained by way of example with reference to the figures.

Fig. 1 shows schematically a process water treatment and purification plant for Persipan production.

Fig. 2 shows the operating principle of the cyanide stripping.

The cyanides are extracted from the food to be treated in a cascade of containers. Representative of this, a container of the cascade 1 is shown in Fig. 1, from which the resulting extraction water first reaches a buffer container 4 '. The buffering of the water enables the subsequent continuously working treatment steps of the process water treatment to be evenly applied to the water. The effects of disturbances in the production process are thus prevented or at least mitigated in the processing plant.

Starting from this buffer tank, the water containing cyanide and solids is fed evenly to a centrifuge 2 , or to a filtration and / or UV disinfection. The solids are separated from the water in the centrifugal field. At the same time as the solids are separated, occurring microorganisms are separated or their number is greatly reduced. The organisms are both associated with the solid and, if they are sufficiently large, are separated off directly. The solids are sent to composting along with other food waste.

This process step also removes solids controls the hygienic properties of the process water.

The second important processing step is the subsequent stripping column 3 . An intensive mixing of the cyanide-containing water with compressed air from a supply 3 c is generated therein and the associated mass transfer between the liquid and gaseous phases ensures that the free cyanide is discharged in the form of the hydrocyanic acid with the exhaust air. The relationships are clearly shown in FIG. 2.

Fig. 2 shows the functional principle of the cyanide stripping shows in detail. The stripping column 3 is fed on one side 3e via the feed line 3 a to the process water. This leaves the stripping column via the outlet 3 b. In countercurrent to this, the stripping gas, preferably compressed air, is supplied via the feed line 3 c. This migrates as gas phase 3 f in countercurrent parallel to the liquid phase 3 e (process water) of the process water and leaves the stripping column at the outlet 3 d again. By reversing the dissociation reaction, the gaseous cyanide HCN forms within the stripping column and passes into the stripping gas. Since the gas is not saturated with cyanide, this is an imbalance, so that undissociated cyanide is continuously formed in the liquid phase, which passes into the gas phase.

The processed process water is passed into a further buffer vessel 4 and is available to the production process as a supply. Via a pump 5 , the process water can now be conveyed either into the extraction container 1 or via a bypass 6 into the centrifuge buffer 4 '. Due to the short circuit via the bypass 6 , a continuous treatment of the water is possible, even if the production comes to a standstill. The internal circulation system takes into account the hygienic requirements in particular, since a constant separation of any growing microorganisms is achieved in the centrifuge.

In summary, the process water treatment can be done with one Compare waterworks, depending on the requirements of the Production process water removed and fed for treatment can be.

Process-related water losses and evaporation deficits during stripping are compensated with fresh water via a control in the storage buffer 4 .

By means of the multifunction pump 5 , the entire circulation water can be conveyed into the post-cleaning part of the system if necessary and the treatment circuit can be filled with fresh water after cleaning. The water gets into the container 8 and is finally treated there. For this purpose, the residual cyanides are stripped with compressed air in the container operated as a stripping column. The cyanide content is reduced to a minimum in a treatment time of 10 to 24 hours.

After the completion of this treatment, it may be necessary to add small amounts of oxidizing agents and to add sodium hydroxide solution to adjust the pH in order to completely destroy any cyanide residues that are still present. For this purpose, the container 8 is connected to corresponding chemical containers 11 a, 11 b. The stripping air used is to be used from an economic point of view both in process water treatment (stripping column 3 ) and in post-cleaning (container 8 ), since the saturation limit for cyanide is not reached with the air quantities used.

The cleaned wastewater is passed through a neutralization station 12 and, after setting a suitable pH value, is introduced into the municipal wastewater network (indirect discharge). The specified limit values are set in the wastewater treatment plant 8 or undercut.

The cyanide-enriched stripping air is fed to a lye wash with integrated cyanide destruction. In the case of lye washing, consisting of a storage and dosing container 10 and a washing column cascade 9 , a consistent cycle is also used. The chemical destruction reaction can be defined as follows:

I. Lye washing reaction (exhaust air purification)

The cyanide (in the form of hydrocyanic acid) is extracted from the sodium hydroxide solution Stripping air eliminated and chemically bound:

The reaction consumes the sodium hydroxide solution and the oxidizing agent and has to be replenished accordingly from the chemical containers 11 a, b.

II. Oxidation reaction of sodium cyanide in basic

In the further reaction the sodium cyanide enriched in the alkali becomes destroyed with hydrogen peroxide:

III. Oxidation reaction of the cyanate in acid

In another reaction in a slightly acidic environment and one Oxidizing agent mixture of hydrogen peroxide and monopersulfate will Cyanate completely destroyed. The addition of monopersulfate optimizes the Reaction and ensures minimal use of oxidants.

The resulting end products are nitrogen (N₂) and carbon dioxide (CO₂) completely harmless and leave the destruction facility as gases.

Claims (21)

1. A method for removing cyanides from industrial process water, characterized in that

• A) the process water is circulated between the application process ( 1 ) and cyanide removal ( 3 ),
• B) if necessary, the process water is physically treated in one stage ( 2 b),
• C) stripping gases flow through the process water in a stripping column ( 3 ), in which the cyanides accumulate, and D) the process water is subjected to treatment steps B) and / or C) several times in a sub-circuit.

2. The method according to claim 1, characterized in that the cyanide-laden Stripping gases another treatment step to destroy the Cyanides are subjected. 3. The method according to any one of claims 1 to 2, characterized in that air as stripping gases, Carbon dioxide and / or nitrogen are used, preferably Compressed air.   4. The method according to any one of claims 1 to 3, characterized in that the process water by centrifuging heavy and / or solid components in a centrifuge ( 2 ), by filtration, preferably micro, ultra and / or nanofiltration, or by UV Irradiation is physically processed for the purpose of disinfection. 5. The method according to any one of claims 2 to 4, characterized in that the destruction of the cyanides in step E) takes place in three stages:

• E1) washing out the cyanides from the stripping gas by washing the gas with lye, preferably sodium hydroxide solution NaOH,
• E2) treatment of the cyanide enriched in the base with hydrogen peroxide in a basic medium, and
• E3) Oxidation of the treated cyanide to nitrogen and carbon dioxide by adding hydrogen peroxide and / or monopersulfate in a reaction initially in a basic environment and / or by adding ozone as an oxidizing agent.

6. The method according to claim 5, characterized in that treatment stage E2) takes place at a pH greater than 10. 7. The method according to claim 5 or 6, characterized in that treatment stage E3) takes place at a pH of 5 to 6.5, preferably 6.   8. The method according to any one of claims 5 to 7, characterized in that the oxidation with Hydrogen peroxide in stages E2), E3) by connecting one Irradiation with UV light can be supported. 9. The method according to any one of claims 5 to 8, characterized in that the wash liquor in the circuit to be led. 10. The method according to any one of claims 2 to 4, characterized in that the destruction of the cyanides by catalytic oxidation, preferably on copper or activated carbon, done with oxygen. 11. The method according to any one of claims 2 to 4, characterized in that the destruction of the cyanides by conversion with aldehydes, preferably with formaldehyde, and subsequent hydrolysis is carried out, preferably under additional use of hydrogen peroxide. 12. The method according to any one of claims 1 to 11, characterized in that the stripping gas after passing through the stripping column ( 3 ) once or several times in process step C) is passed through a second fluid loaded with cyanides ( 8 ) and absorbs further cyanides therefrom , whereby fresh stripping gas may also be used. 13. The method according to claim 12, characterized in that the second fluid ( 8 ) is cleaned until it, if necessary. After chemical oxidation of the residual cyanides, can be introduced into the waste water. 14. The method according to any one of claims 12 to 13, characterized in that the second fluid ( 8 ) process water to be disposed of is from the application circuit after stage A). 15. Device for removing cyanides from industrial process water in a process according to one of claims 1 to 14, characterized in that it contains a circuit of the process water, in which are arranged:

• a) an installation ( 1 ) for carrying out the application process,
• b) if necessary. one or more buffer tanks ( 4 ) for the process water,
• c) if necessary, a centrifuge ( 2 ),
• d) if necessary, a filter, preferably a micro, ultra and / or nanofilter,
• e) if necessary, a UV radiation station for disinfection,
• f) a stripping column ( 3 ) with an inlet ( 3 c) and outlet ( 3 d) for stripping gas,
• g) one or more circulation pumps ( 5 ), and
• h) if necessary. an adjustable bypass ( 6 ) to circumvent the application process in the system ( 1 ).

16. Device for performing the method according to one of claims 5 to 9,
characterized in that

• a) it contains an exhaust air washer ( 9 ) with a feed ( 9 a) of cyanide-contaminated gases and an outlet ( 9 b) of purified gases and an inlet ( 9 c) and outlet ( 9 d) of the wash liquor,
• b) a treatment container ( 10 ) for destroying the cyanide is arranged behind the outlet ( 9 d) of the wash liquor,
• c) the treatment container ( 10 ) is connected to chemical containers ( 11 a, b), and
• d) if necessary. The outflow of the treatment container ( 10 b) is connected in a circuit with the wash liquor inlet ( 9 c) of the exhaust air scrubber ( 9 ).

17. The apparatus according to claim 16, characterized in that the treatment tank ( 10 ) is connected to a neutralization reactor ( 12 ) which is connected to the chemical tank ( 11 b, c) and has an outlet ( 13 ) for purified waste water. 18. Device according to one of claims 16 or 17, characterized in that a stripping column ( 8 ) is arranged in front of the exhaust air scrubber ( 9 ) through which the stripping gas is passed. 19. The apparatus according to claim 18, characterized in that the stripping column ( 8 ) with chemical containers ( 11 a, b) is connected. 20. The apparatus of claim 18 or 19 in connection with a device according to one of claims 15 to 17, characterized in that the stripping column ( 8 ) has an inlet ( 8 a) for process water to be disposed of from the circuit of the application process. 21. Use of the device according to one of claims 15 to 20 in the food industry, preferably in the debittering process of Cores, preferably in Persipan production.