WO2007144252A1 - Method for reducing impurities in a water system during the production of flat structures - Google Patents

Abstract

The invention relates to a method for reducing impurities which are formed by organic dyestuffs, biocatalytic substances and/or microorganisms and/or other biological material in a water system (90) during the production of flat structures from fibrous material in aqueous suspension. A method is provided for reducing the use of chemicals and/or complementary dyestuffs in order to reduce the impurities formed in the water system by a gas discharge and/or a plasma being generated by application of a voltage (U) to electrodes (50, 51) in the water (23) or in the suspension, wherein a voltage profile (60) of the voltage (U) has voltage pulses (66, 67) having a pulse duration of less than 10 μs, wherein a streamer discharge (53) is generated. A papermaking plant (1) can thus be operated in a more environmentally friendly manner.

Description

description

Method for reducing impurities in a water system in the production of fabrics

The invention relates to a method for reducing by organic dyes, biocatalytic substances and / or microorganisms / or other biological material and ge ^¬ impurities formed in a water system during the production of of fabrics made from fibrous material in aqueous suspension ger.

The use of short high voltage pulses for ozone generation for water purification is e.g. known from the specialist article by S. Ihara, T. Miichi, S. Satoh, C. Yamabe,

"Ozone generation by a discharge in bubbled water", Digest of technical papers 12th IEEE International Pulsed Power Confer ^¬ ence 1999th

WO 02/070816 A2 discloses a method and a device for treating a fluid with a high-voltage electric field. This method is to be improved in terms of its efficiency.

In the production of fabrics and felts of natural fibers, in particular in the production of paper and pulp from wood fibers and / or waste paper, a very large amount of water is required, based on a final product. In the prior art, the water is recycled in a nearly closed cycle. A water system is understood to mean all in ^¬ nerbetrieblichen circuits in, for example, a paper mill. In principle, despite a large variety of existing water cycle circuits, a generally valid design of the operational water cycles can be given as follows.

A primary circuit is formed by a direct Wiederverwen ^¬ a dung-rich effluent from a first drainage tion stage of an example paper machine and is used for dilution purposes or for solid adjustment in and, in terms of process technology, in front of the paper machine. Waste water with a high solids concentration, the fertil during Blattbil- incurred on the paper machine are to be correspondingly fed back in a short cycle, a white water circulation system for Pa ^¬ piermaschine.

A secondary circuit is characterized by a material recovery stage and serves to return accumulated press and spray waste water to the paper machine.

For example, a tertiary cycle occurs when a wastewater surplus from the secondary cycle is combined with other wastewater from production. This common sewage ^¬ serstrom can then be treated in a factory sewage treatment plant, treated together with fresh water from an example surface water and recycled as fresh water in the operation.

Through this reprocessing of the water, a fresh water requirement or a wastewater quantity can be limited. But a high average residence time of the water used in the example ^¬ as paper manufacturing process impurities accumulate in the water.

For the purposes of the invention, impurities are, for example, dissolved organic substances whose concentration in the water system increases with increasing closed circuit. Such and other impurities often cause dewatering deterioration, resulting in less favorable sheet formation and less opticity in the case of papermaking. Furthermore, for example, a reaction of the impurities with chemical aids can lead to the formation of undesired deposits. These deposits can eventually lead to stains and holes in the paper during papermaking. Colored impurities are caused by the dyes used in today's printing process, for example, which are largely water-soluble. High solubility in water of the dyes used, especially when using recycled paper as starting material, means that even in a flotation process, the dyes can not be completely eliminated. In particular, what ^¬ serlösliche red dyes responsible for ensuring that the water takes on a reddish tinge which product to the end ^¬, preferably a paper transfers. To a high ^¬ aspiring whiteness, for example, in the preparation of white papers, can not be achieved in colored water.

Especially under the conditions narrowed cycles increased proliferation of requested in the water contained ^¬ microorganisms can be observed in general. For example, the dissolved oxygen present in the water is rapidly consumed and this can lead to the formation of anaerobic conditions in the water. The microorganisms can then rapidly proliferate and micro Orga ^¬ mechanisms can, for example, to strong odor pollution in the form of hydrogen sulfide and / or organic acids or yeasts and bacteria lead metabolic products of these. In addition, in some

Cases, due to the effect of the above-mentioned metabolites of anaerobic microorganisms, corrosion on system components. Cause are in particular microorganisms, which among other things carbohydrate-splitting enzymes such. release the enzyme celloulase, with which celloulose, which is preferably present in the papermaking process, is decomposed as a fiber base and serves as a decomposed, short-chain carbohydrate as food for the microorganisms.

For the definition of biological material, see Rule 23b (3) EPC. Under biocatalysis, for example, a chemical change ^¬ effective between a protein and other particles (molecules, ions, protons, electrons), in the course of which the nature of these particles varies, to understand. A biocatalytic substance, such as an enzyme or protein, promotes biocatalysis. Conventionally, the unwanted organic impurities, microorganisms and enzymes are counteracted by the addition of other dyes or biocides in ^{Papierherstel ¬ ment} .

The invention has for its object to provide a method to reduce the use of chemicals and / or complementary dyes to reduce the impurities formed in the water system.

The object is based on the above-mentioned method achieved by applying a voltage to electrodes in the water or in the suspension, a gas discharge and / or a plasma is generated, wherein a voltage waveform of the voltage has voltage pulses with a pulse duration of less than lOμs, wherein a streamer discharge is generated. The advantage of this is that the use of higher field strengths is made possible by the short pulses, which advantageously cause a streamer discharge. Furthermore, an early voltage breakdown between the electrodes can be avoided by the short pulses. A streamer discharge is a special form of a linearly moving plasma cloud or a developing discharge channel that forms due to the applied high external field strength under a short pulse duration. By streamer discharge is a particularly efficient Erzeu ^¬ supply of radicals reached in the water system, which improves the cleaning effect. In the water of the water system, a streamer discharge can be generated at almost any point of the different circuits. As a result, different levels of contamination can be treated with, for example, under ^¬ different intensity of the discharge. By means of a plasma and / or a gas discharge in the water or In the immediate vicinity of the water chemically active substances are released, which make the impurities present in the water harmless. Thus, both the micro-organisms or simultaneously with these mutually-promoting enzymes, such as cellulase, adversely affected the ^¬ by e- lektrochemische reaction in the papermaking process.

A further increase in the generation of radicals or of chemically active substances is achieved by the pulse duration is less than 1 microseconds, in particular in the range of 100 ns to 900 ns. When a voltage is applied to the electrodes with such intense pulses, due to the short duration of time and the high field strength, locally very effective gas discharges occur. Since the withstand voltage of water, in particular water of high conductivity is very low, with decreasing duration of voltage stress however, dramatically increases, short pulses are particularly advantageous ^¬ way. The conductivity of the water in the white water circuit is in the range of 4 to 5 mS / cm. In this case, it is particularly important to an electric field with a high field strength ^¬ generate without causing a current strong local punch.

It is expedient that at least one of the following chemically active substances is produced:

a radical, in particular O, OH, HOO,

- An oxide, in particular ozone O ₃ , H ₂ O ₂ .

The generation of radicals as chemically active substances in the water of the water system, in particular in the white water circuit and / or in the clear water circuit, can be done at one or more points of different water cycles. In particular, by the gas discharge in the water, the radicals mentioned can be particularly easily generated (see here the above mentioned technical article).

Furthermore, it is expedient that by the voltage electric field in the range of 1 MV / cm, preferably 1 MV / cm to 10 MV / cm, is generated. Such a high field strength between the electrodes promotes the advantageous generation of gas discharges. When using non-metallic electrodes, the field strength may be reduced. Another advantage of using non-metallic electrodes is that more chemically active substances such as OH or H can be generated. Depending on the use of the electrodes, the electric field may also be in the range of 0.1 MV / cm to 1 MV / cm.

It is expedient to achieve a further effect effect that is generated by the voltage, in particular by the voltage pulses, ultraviolet radiation. The streamer discharge favors that, for example, electrons from the water molecules are excited by collisions in such a way that they emit ultraviolet radiation. It is sufficient therefore ER- with ^¬ means of the voltage pulses such a high electron tempera ture in ^¬ a streamer discharge or a gas discharge, that ultraviolet radiation and / or radicals and / or oxidizing substances are produced with a high efficiency. These radicals, oxidants and / or lettering ultravio ^¬ radiation directly access the unwanted impurities and destroy them. In a first step, for example, the ultraviolet radiation strikes the cell walls of the cells of the contaminants, causing pre-damage in the cell walls of the contaminants. The pores of the cells can be opened under certain circumstances and it comes to a "bleeding" of the cell. After the destructive effect of the UV light, the chemically active substances, in particular the radicals, can now easily penetrate into the cells and destroy them completely.

Advantageously, a concentration of the chemically active substances in the water or in the suspension is measured in real time, in particular "online". With regard to the regulation or control of a rate of production of the chemically active substances, it is advantageous to have knowledge of the current concentra- tion of the generated chemically active substances to obtain continuously.

In a further embodiment, a concentration of the impurities in the water or in the suspension, in particular in real time or "online", is measured. The Kon ^¬ concentration of the impurities is also a measure of the effectiveness of the process, for example, a Erzeu ^¬ transmission rate of chemically active substances become more and more comparable Ringert the smaller the measured concentration of the impurities in the water.

In a further advantageous embodiment of the measurements for determining a controlled variable, a concentration of proteins and / or DNA residues in the water or in the suspension, in particular in real time or "online", is measured for controlling and / or regulating a microbiological sterilization , Characterized in that the cell walls and / or the cell h ^¬ len by the aforementioned method steps at least in part be destroyed, can be controlled by measurement of DNA residues of the electrochemical sterilization process. A control over a measured value of the concentration of enzymes is also possible.

Advantageously, a value of the concentration is used as a controlled variable for the voltage triggering the electrochemical process.

The object of the invention can therefore be used so that no auxiliaries, e.g. Chemicals or biocides, and / or complementary dyes are used for the purpose of reducing the impurities. This measure allows a very environmentally friendly operation of an example papermaking plant.

If, depending on the water conditions, it is not possible to completely dispense with auxiliaries or complementary colors, it is advantageous to use auxiliaries and / or complements. color is added in an amount that is less than the amount that would be required without applying the voltage. An accurate knowledge of the concentration and the effect of chemically active substances in the water or the suspension opens up the possibility, excipients and / or complementary ^¬ colors in terms of a to be achieved result opti ^¬ times to dose and so the possible environmental impact too low hold. After all, biocides, algicides, bactericides, fungicides and others, which are sometimes used as auxiliaries, pollute the environment. Also a cost advantage is achieved by abandoning or curtailing ^¬ kende addition of dyes or excipients.

It is expedient that one or more of the following substances be used as the fibrous material:

- waste paper,

- natural fiber, in particular wood pulp and pulp,

- textile fiber.

Advantageously, the water system has one or more of the following material and / or water cycles:

- a primary circuit, in particular a Siebwasserkreis ^¬ run,

a secondary circuit, in particular a clear water circuit,

- A tertiary cycle, in particular a cycle for purified wastewater.

Embodiments and other advantages of the invention will become apparent from the drawing described below, in whose

FIG 1 cycles a papermaking system with water ^¬, FIG 2 is a view (sectional) of an arrangement for generation of free radicals in corona plasmas in an aqueous solution or in air: parallel plate or tube assembly with wire, to which a pulsed high voltage is superimposed,

3 is a schematic diagram of pulses for generating radicals in corona discharges in air or aqueous media using short (typically less than 1 μs) high voltage pulses with high pulse repetition rate,

FIG. 4 to FIG. 9 Electrode arrangements and electrode systems for generating corona discharges: plate-plate, plate-wire-plate, coaxial

Wire Pipe, Tip Plate, Multiple Pit ^¬ zen Plate, Lattice Plate (Pipe, Lattice Grid Arrangements,

Figure 10 is a hybrid discharge, wherein one electrode is located entirely above a wässri ^¬ gene solution and the second electrode is immersed in the aqueous solution,

11 shows a plate or grid arrangement with curved surfaces for adaptation to vessel walls or use thereof as an electrode, concentric electrodes in tubular form for use of the existing piping or towers for the pulp as reactor vessel,

12 shows a pulsed discharge in the near-surface space of the aqueous solution,

FIG. 13 shows a pulsed corona discharge system with a coaxial wire tube, with embedded, finely distributed gas bubbles, so that finest gas beads are present in the discharge region and streamer formation predominantly takes place in the gas bubbles,

FIG 14 is a schematic overview of a Wassersys ^¬ tems,

is illustrated.

Corresponding parts are provided in Figures 1 to 14 with the same reference numerals. 1 shows a schematic representation of a papermaking plant 1, in which the operating method is realized according to the invention. Diluted with water in the ratio of about 1: 100, fibrous materials or fibrous materials are applied together with excipients to a sieve device 9 with a sieve 10. The fibrous materials are deposited on the screen 10 side by side and on each other. A Kreislaufwas ^¬ ser 23 can flow off or sucked by means of several Saugkammerbereiche 24 and are recycled into a cycle of the circuit ^¬ water 23. Explanations of the different circuits and / or material and water flows of the water system of the paper mill are given with FIG. 14 and the associated description.

Waste paper and, as a rule, pulp in dry form reach the paper mill as starting material, while wood pulp is normally produced in the same factory and pumped into a material center 3 as a fiber / water mixture, ie a suspension of non-fibrous fibers. Waste paper and / or pulp are also dissolved by adding water in a fiber trough. Paper strangers Be ^¬ constituents are various sorting aggregates of ^¬ discharged (not shown here). In the material center 3, depending on the desired type of paper, the mixture of different raw materials takes place. Fillers, auxiliaries and complementary colors are also added here to improve paper quality and increase productivity. ^{According to the} invention, the addition of at least one of these substances can at least be restricted.

The headbox 7 of the papermaking plant 1 distributes the pulp suspension uniformly over the entire sieve ^¬ width. At the end of the screening device 9, the paper web 27 still contains about 80% water.

On the basis of waste paper as a raw material for ^¬ Papierherstel development of paper production plant 1 is a stock preparation upstream (not shown here). A pipe system connecting the paper making system 1 with the circulation water stock preparation ^¬ 21st

For a treatment of the water or material flow for stock preparation 21 and the circulating water 23 according to the invention, plasma reactors IIa to Hd are arranged in the papermaking plant 1 at different points of the pipeline system.

To reduce colored impurities in the circulating water 23, a first plasma reactor Ha is arranged in the return line of the circulating water 23 from a suction chamber area 24 to a sorter 5. A second plasma reactor Hb is disposed in the return line of the circulating water 23 between a suction chamber portion 24 and a fabric catcher 17. Behind the fabric catcher 17, as seen in the flow direction S, the piping system is divided into a piping system for the water or material flow for Stoffauf- preparation 21, the material cycle and the other in a piping system, which to a not shown cleaning system (indicated by arrow 19) leads to. A third plasma reactor Hc for generating an electrochemical process is disposed in the piping for the recycling water circulation system 21 behind the fabric catcher 17. A fourth plasma reactor Hd is arranged in the piping system, which leads to the cleaning system 19, behind the fabric catcher 17. The process of the invention shown by way of example is characterized in that at the indicated points by means of the plasma reactors Ha to Hd in the pipe system of the circulating water 23, the water and material streams for the ^{preparation ¬} material 21 and in the piping to the cleaning system 19, electrodes in the interior of the piping system are introduced, which are acted upon by a high pulsed voltage ^¬ . A high voltage pulse generator 46 is individually connected via high voltage lines 47 to the plasma reactors Ha to Hd. As a dielectric strength of Water, especially of high conductivity water, as it has the circulating water 23, is very low, but increases dramatically with decreasing duration of the stress load, short pulses with pulse durations of typically 10 μs, in some applications of only lμs, and below are used. In the paper industry typical values for the conductivity are 4 to 5 mS / cm.

FIG. 2 shows, as a particular embodiment, one of the plasma reactors IIa to Hd shown in FIG. 1. The device in FIG. 2 is designed to pass through the circulating water 23 and simultaneously generate plasma in the stream of water or material. In the middle of the device, a high voltage electrode 50 is arranged. The outer sheath of the cylindrical shaped means is provided as a counter-electrode 51 depends Herge ^¬. By applying the pulsed voltage to the electrodes 50, 51, a streamer 53 is generated between the electrodes 50 and 51 by the electric field. Radicals 59 are formed in streamers by the fact that high-energy electrons 55 collide with water molecules and thereby dissociate or excite them. Upon dissociation, the radicals 59 and oxidants 57 are released immediately, while UV light is produced upon excitation by a subsequent radiant transition. This generated UV light in turn reacts with water molecules and dissociates them.

With regard to the colored impurities these radicals and oxidants 59 57 directly access the high-molecular dyes to and destroy them so far that the Farbwir ^¬ effect of the molecules is eliminated.

With regard to the microbiological contaminants, these are attacked and destroyed by the UV light, the radicals 59 and oxidants 57. By the simultaneous action of meh ^¬ rerer such biocidal components, a synergy effect is achieved, which leads to a particularly effective sterilization of the circulating water 23. In particular, that leads already At the beginning of the treatment of the Klreislaufwassers 23 high electric field applied to a further increase in synergy by a pre-damage of the biological cells by Ele- electroporation of the cell walls, which are then particularly vulnerable to the subsequently generated chemically active agents, in particular the radicals 59 and the Oxi

Microorganisms which release carbohydrate-cleaved enzymes, such as the cellulase enzyme, which decompose the cellulose in-process as a fiber base and thus serve as decomposed, short-chain carbohydrate for the microorganisms, are also inhibited or totally destroyed. The microorganisms, such as bacteria or yeast, are killed, minimizing cellulase production.

By a simultaneous degradation of a catalase can build up in addition to the radicals and a H ₂ 0 ₂ concentration. This in turn contributes to the direct cellulase degradation as well as to the sterilization of the microorganisms produced by the cellulase.

In FIG 3, the voltage waveform 60 of the high tensioning ^¬ used is shown voltage pulses. A first pulse 66 and a two ^¬ ter pulse 67, each with a pulse duration 62, have a distance-from a pulse repetition rate 63. The abscissa shows the time in ms and the ordinate the voltage in kV. The units are chosen arbitrarily. A level of subordinate DC voltage may coincide with the abscissa shown. The DC voltage required for the generation of preferably radicals and ozone is approximately 100 kV. The high voltage pulses are of equal tension superimposed ^¬ voltage and thus form a total amplitude of about 500 kV. The voltage curve 60 shown can thus before ^¬ preferably a DC voltage are superimposed, this is highly dependent on the conductivity of the water to behandeinen. The pulses 66 and 67 have a pulse duration 62 of less than 1 .mu.s, wherein the individual pulses 66, 67 have a steeply rising edge with a rise time 64, which is significantly less than the pulse duration 62. The falling edge associated with the pulse 66 or 67 is less pronounced. The pulse repetition time 63 is typically between 10 μs and 100 ms. The DC component already generates the damaging effects from the electrochemical process.

Preferably, the individual pulses 66, 67 have such a total amplitude that a predefined energy density is achieved beyond a predetermined direct voltage. As he ^mentions , the pulse rise time 64 is usually short in ^comparison to the pulse fall time. Through such kind of Impul ^¬ se 66, 67 ensures that electric breakdowns, which would lead to spatial and temporal disruptions in the homogeneous plasma madichteverteilung be avoided.

FIG 4 to FIG 9 show further examples of Elektrodensyste ^¬ me for generating plasma and / or corona discharges in the water system or the suspension of Papierherstellungs- Anläge 1, in particular for alternative use in the aforementioned embodiment. 4 shows a plate-and-plate arrangement of a first plate 70a as an electrode and a second plate 70b as an electrode. The first plate 70a and the second plate 70b are arranged parallel to each other. The first plate 70a forms the high ^¬ voltage electrode and is connected via a high voltage cable to the high voltage pulse generator 46. The second plate 70b forms the counter electrode and stands as a grounded electrode with the high voltage pulse generator 46 in conjunction fertil.

A corresponding arrangement with specially flat plate ^¬ electrodes is shown in FIG 5. In turn, there are two solid plate electrodes 70a and 70c at a fixed distance, wherein a high-voltage electrode 71 runs in the middle. In this plate-wire plate assembly, the high voltage electrode 71 is made as a solid wire and connected to the high voltage output of the high voltage pulse generator 46 connected. The grounded plates 70a, 70c are also in communication with the high voltage pulse generator 46.

6 shows a wire-tube arrangement as an electrode system. In a cylindrical electrode 72 projects centrally a high ^¬ voltage electrode 71 inside. As the high voltage electrode 71 ^¬ is implemented as a solid wire and connected to the high voltage pulse generator 46 in Fig. 5 The cylindrical electrode 72, which is preferably configured as a braid Drahtge- is grounded and is connected to the high voltage pulse generator 46 in ^¬ compound.

7 shows a tip-plate arrangement as Elektrodensys ^¬ tem. The example, three peaks 73 are connected via a high voltage line to the high voltage pulse generator 46. The tips 73 are arranged at right angles to a grounded plate electrode 74. The distance between the tip ^electrodes 73 to the plate electrode 74 is adjustable and can thus be adapted for different process conditions.

8 shows an electrode system arrangement comprising 3 plates 70a, 70d and 70e. The first plate 70a, which is connected as a high voltage electrode to the high voltage pulse generator 46, is centered between two solid plates

70d and 70e arranged. The plates 70a and 70b are connected via ei ^¬ nen plate connector 70f. Since the plate 70d as a grounded counter electrode is in communication with the high voltage pulse generator 46, the plate 70e above the plate connector 70f also functions as a grounded counter electrode.

9 shows an electrode system as a grid-grid arrangement. Analogous to FIG. 4, a first grid 75a and a second grid 75b are parallel here. The first grid

In this case, 75 a forms the high-voltage electrode and is connected to the high-voltage pulse generator 46. The second grid 75b forms the grounded counter electrode and communicates with the high voltage pulse generator 46.

Common to all electrode arrangements already mentioned is that, instead of applying high-voltage pulses 66, 67, as shown in FIG. 3, they also ^{apply a DC} voltage, for example in the range from IV to 10V, in particular 2V to 5V, to produce a continuous electrolysis can be.

An alternative hybrid discharge, wherein an electrode 76a is completely outside the Kreislaufwas ^¬ sers 23 to be treated and a second electrode 76b is completely or partially immersed in the circulating water 23 is generated with the arrangement in FIG. In this further embodiment, the electrode 76a is designed as a grid electrode and is connected to the high-voltage pulse generator 46. The grounded counter-electrode 76b is also designed as a grid electrode. At the boundary layer between air and circulating water 23, a first charge ^¬ cloud 68a is formed. With the help of this charge cloud 68a, the chemically active substances can enter the circulation water 23 and eliminate the unwanted impurities. Also in the circulating water 23, charge clouds 68b, 68c are preferably formed at locations with locally increased field strength. The charge clouds 68a, 68b, 68c release in the circulating water 23 radicals such as O, OH, HOO but above all also strong oxidants such as ozone and / or H2O2. These chemically active substances destruc ^¬ ren with high efficiency micro-organisms such as bacteria and yeasts.

In FIG. 11, as a further exemplary embodiment of the plasma reactors 11a to 11d known from FIG. 1, a pipe, preferably a pipe for transporting the circulating water 23, is shown with an outer wall 77 in a section. It is a Plat ^¬ TEN or grid configuration having curved surfaces to adapt to the outer wall 77 and a vessel wall used. A multiple wire electrode 79 is referred to as a concentric E electrode, following the course of the outer wall 77, and communicating with the high-voltage pulse generator 46. It faces two counterelectrodes: on the one hand the vessel wall 77 and on the other hand a plate electrode 78. The high voltage electrode 79 is arranged without contact between the vessel wall 77 and the plate electrode 78. The vessel ^¬ wall 77 and the plate electrode 78 are electrically conductively connected to one another and thus form the earthed counter-electrodes, which are associated with the high voltage pulse generator 46 in connection. With S, a flow direction of the circulating water 23 is indicated.

In order to generate pulsed discharges in the near-surface gas space above the circulatory water 23 is shown in FIG 12 Darge as a further embodiment a special electrode assembly ^¬ represents. The circulating water 23 is guided in this case in an upwardly open circulating water channel 37. A high ^¬ voltage electrode 50 includes a plurality of electrically interconnected rod electrodes and is arranged in the near-surface gas space of the circulating water 23 such that their rods are parallel to the surface. A grounded Gegenelekt ^¬ rode 51 is designed as a solid plate and arranged in distributed over the entire surface equidistant distances to the high voltage electrode 50. The wall of the Kreislaufwasserka- channel 37 is additionally connected to the counter electrode 51.

In the case of this electrode arrangement too, charge clouds develop at the boundary layer between air and circulating water, as indicated by way of example with the charge clouds 68d and 68e. The charge clouds also ensure penetration of the chemically active substances into the circulation water 23.

FIG 13 shows a final embodiment, a ge ^¬ pulstes plasma or corona discharge system Kreislaufwas- ser 23. The electrode system is formed analogous to FIG 2 as a Ko ^¬ axialdraht tube electrode system. The high voltage electrode 50 is coaxial with the counter electrode 51, wel ^¬ che forms the vessel wall arranged. In support of the Radical generation or the generation of chemically active substances are introduced via a gas line 80 by means of a gas distributor 81 finest gas bubbles in the discharge area. In the gas bubbles 82 and 83, the streamers illustrated in FIG. 2 preferably form. Because of the streamer discharges, oxidants 57 are formed. Thus, in the circulating water 23, certain radicals are generated.

FIG. 14 shows the substance and water flows or material and water cycles as they occur in the water system 90 in the paper mill with the operating method according to the invention. The central point of the water system 90 is the paper ^¬ manufacturing plant 1. In FIG 14 is of a large lot ^¬ diversity of existing water circulation circuits out a frequently conventional structure of the operational water circuits ei ^¬ ner paper mill shown schematically. There are three main water cycles: a primary circuit I, a secondary circuit II and a tertiary circuit III. The primary circuit I is obtained by a direct reuse of the hydrogen-rich effluent from a first dewatering stage of the paper making system 1 and serves preference ^¬ example for dilution purposes or to a Feststoffeinstel- lung in and before the papermaking equipment 1. wastewater and / or the aqueous suspension with Preferably, a highest solids concentration incurred during the sheet formation in the papermaking plant 1, can be accordingly ^¬ speaking in a short cycle, the white water circulation 98, returned to the papermaking plant 1. From ^¬ aqueous and / or aqueous suspension having a significantly lower solids concentration are in the primary circuit II, the clear water circuit 99, passed.

The primary circuit II is characterized by a Stoffrückge ^¬ winnungsstufe, here the saveall 17 from. The fabric catcher 17 serves to return the resulting press and spray effluents, which occur in the papermaking plant 1. This is represented by box 94, in which various white water portions, marked by straight lines, point outwards. introduce. More Siebwasseranteile lead to a Stofffän ^¬ gererweiterung 17a. The saveall 17 divides the different Siebwasseranteile in a smaller-rich portion, which leads to the clarified water circuit 99 and the turn direction as dilution water for the Stoffaufbereitungsein- 93 serves, and in a major portion with a lower fiber content, the treatment plant spray pipe water for Papierherstel ^¬ 1 can be used further. The proportion with the lower substance content is passed through a wastewater treatment plant 96 and added to the tertiary cycle III, ie the ^cycle for purified water 100. The water wel ^¬ ches is not recycled through the wastewater treatment plant 96 in the Tertiary ^¬ ärkreislauf III, can be returned through a waste water ^¬ derivative 97 purified of the environment.

The tertiary cycle III arises, for example, when a wastewater surplus from the secondary circuit II is combined with other production wastewater. As already mentioned, this common wastewater stream is treated in a factory sewage treatment plant, treated together with fresh water from, for example, surface water, and returned to the plant as fresh water. Such a ^¬ direction of a circuit for purified wastewater 100, so the tertiary circuit III leads to a quantitative decision-utilization of the secondary circuit II, a reduced accumulation of residual water from the paper production plant 1 and thus overall 90th in improved fresh water use efficiency in the water system via a fresh water feed 91, the water system 90 is basically supplied with the required fresh water via a fresh water treatment plant 92. The secondary circuit II and the tertiary circuit III are fed to the papermaking plant 1 via a stock preparation device 93. A return of the secondary circuit II to Papierher- positioner 1, wherein a side stream is not performed on the fabric ^{¬ treatment} device 93, is also possible. Via a waste disposal 101, solids arising in the stock preparation device 93 can be separated out. the. Evaporation losses 102, which can no longer be returned to the three main ^loops I, II and III, escape from the papermaking plant 1.

Exemplary water flow rates for the circuits are as follows: a white water circuit 98 is at about 100 to 200 m ³ per day, a clear water circuit at 10 to 50 m ³ per day and a purified water circuit 100 at 1 to 5 m ³ per day with water and or aqueous suspension.

Further thoughts essential to the invention:

Microbiological contaminants, which can lead to a reduction of the fiber or paper quality in papermaking, are, for example, microorganisms which release, among other things, carbohydrate-cleaved enzymes, such as the enzyme cellulase, with which the cellulose in the process decomposes as a fiber base is used as a decomposed, short-chain carbohydrate as food for the microorganisms. A previous solution to prevent this exploited ^aus¬ finally chemical methods, ie adding chemicals, especially biocides, such as lutaraldehyde, in the material cycle or the water cycle to kill the microorganisms and so the contamination both during the manufacturing process as well to minimize in the final product. The otherwise widely used agent Wasserstoffper ^¬ oxide H2O2 can often not be used, since the peroxide-cleaving enzyme catalase is often also miterzeugt and the hydrogen peroxide H ₂ O _{2 is} rapidly decomposed.

Claims

claims

1. A method for reducing formed by organic dyes, biocatalytic substances and / or microorganisms and / or other biological material contaminants in a water system (90) in the manufacture of fabrics made from fibrous material in aqueous suspension, characterized in that gene under Anle ^¬ a Voltage (U) at electrodes (50,51) in the water (23) or in the suspension a gas discharge and / or a plasma is generated, wherein a voltage curve (60) of the voltage (U) voltage pulses (66,67) with a pulse duration (62) of less than 10 μs, producing a streamer discharge (53).

2. The method of claim 1, wherein the pulse duration (62) is less than 1 microseconds, in particular ^¬ is in the range of 100 ns to 900 ns.

3. The method according to any one of claims 1 to 2, wherein at least one of the following chemically active substances is generated:

a radical (59), in particular O, OH, HOO,

- An oxydantium (57), in particular ozone O ₃ , H ₂ O ₂ .

4. The method according to any one of claims 1 to 3, wherein by the voltage (U) an electric field in the range of 1 MV / cm, preferably with a value in the range of 1 MV / cm to 10 MV / cm, is generated.

5. The method according to any one of claims 1 to 4, wherein by the voltage (U), in particular by the clamping voltage pulses ^¬ (66,67), ultraviolet radiation is generated.

6. The method according to any one of claims 1 to 5, wherein a concentration of the chemically active substances in the water (23) or in the suspension in real time, in particular "online", is measured.

7. The method according to any one of claims 1 to 6, wherein a concentration of impurities in the water (23) or in the suspension, in particular in real time or "online", is measured.

8. The method according to any one of claims 1 to 7, wherein for controlling and / or regulating a microbiological sterilization, a concentration of proteins and / or DNA residues in the water (23) or in the suspension, in particular in real time or " online ", is measured.

9. The method of claim 8, wherein a value of the concentration is used as a controlled variable for the streamer discharge (53) triggering voltage (U).

10. The method according to any one of claims 1 to 9, wherein no auxiliaries and / or complementary dyes are used for the purpose of reducing the impurities.

11. The method according to any one of claims 1 to 10, wherein the auxiliary and / or complementary color is added in an amount which is lower than would be required without application of the voltage (U).

12. The method according to any one of claims 1 to 11, wherein as fibrous material one or more of the following substances is used:

- waste paper, - natural fibers, in particular wood pulp and pulp,

- textile fiber.

13. The method of claim 1, wherein the water system has one or more of the following material and / or water cycles:

- a primary circuit (I), in particular a white water ^¬ circuit (98), - a secondary circuit (II), in particular a Klarwas ^¬ water circuit (99),

- A tertiary cycle (III), in particular a cycle for purified wastewater (100).