EP1891266B1 - Method for treating non-woven fibrous materials and bleaching device - Google Patents

Description

The invention is in the field of industrial treatment of fibrous materials.

The invention relates to a device for bleaching unwoven fibrous materials in a suspension, in particular as pulp or pulp, in or on a given by boundary walls treatment volume, wherein in / by the treatment volume, the suspension is fillable or flowable.

Furthermore, the invention relates to a method for treating unwoven fibers in a suspension, in particular as pulp or pulp, preferably for the operation of the bleaching apparatus according to the invention.

Out S. Ihara, T, Miichi, S. Satoh and C. Yamabe, "Ozone Generation by a Discharge in bubbled water", Digest of Technical Papers 12th IEEE International Pulsed Power Conference, 1999 , a method and apparatus for water purification is known.

Out WO2004 / 10189 A1 For example, a method of surface treating paper or bonded fibers with plasma is known. FR 2 711 680 A1 describes a bleaching process for a fiber web using an electrically generated plasma.

One goal in the treatment of unwoven pulps is the bleaching of the pulps. When bleaching pulp, for example, it is u.a. an objective to remove the lignin contained in the pulp or to destroy certain "colored" molecular groups. This type of treatment preferably leads to a higher degree of whiteness of the pulp.

Today's bleaching processes are based on the chemical treatment of the fibrous material. Typical bleaching chemicals are Chlorine, chlorine dioxide, sulphurous acids, extraction with caustic soda, oxygen, hydrogen peroxide and ozone. Depending on the method used, alkaline or acidic ambient conditions are required. Modern bleaching processes often utilize various bleaching stages employing various bleaching chemicals, each bleaching stage typically consisting of a mixing unit and a subsequent reaction tower. In these processes, some highly toxic (chlorine dioxide) or highly corrosive acids, alkalis or reagents must be transported in large quantities, stored and also worked up or disposed of after the end of the process.

Effectiveness of the bleaching process generally depends on the proper concentration of certain reagents in a fibrous suspension. For a peroxide bleach, the effectiveness of the bleaching process depends very much on the concentration of a perhydroxide (HOO ^- ).

A reaction rate depends inter alia on a pH and a temperature of the suspension. A typical value for the temperature is e.g. 60 ° C to 70 ° C and a typical value for a pH is about 10.5. The pH is usually controlled by the addition of additional chemicals such as sodium hydroxide or sodium silicate. Some methods use pressure and higher temperatures to reduce a necessary residence time in, for example, a reaction tower. A significant cost factor in a bleaching process depends to a large extent on the type and amount of chemicals used and their further treatment, such as a separation or disposal.

The invention has for its object to provide an apparatus and a method to reduce the use of chemicals in the bleaching of unwoven fibers.
The object is based on the above-mentioned device according to the invention by a solved with a first Electrode connected high voltage pulse generator with which in the treatment volume and / or in the immediate vicinity of a plasma can be generated. Since the process of plasma generation in the bleaching apparatus is well controllable and has short reaction times, an easy-to-control, improved bleaching process is obtained in a bleaching apparatus.

In a preferred embodiment, the plasma is generated at a distance of <20 cm, preferably <10 cm, preferably <5 cm, from the treatment volume. The direct treatment of the fibers, preferably pulp fibers, with - preferably cold - plasma generated in the suspension certain radicals. These radicals result in bleaching chemical reactions.

With additional advantage, the bleaching apparatus for fibrous materials is suitable for the production of paper, paperboard or cardboard and / or the fibrous materials can be fed to such a production process as process material.

It is also expedient that the treatment volume is suitable for filling or flowing through the suspension, preferably a starting material in paper, paperboard or paperboard production, in particular a pulp to be bleached or a pulp to be bleached. By filling or flowing through the suspension through the treatment volume, the bleaching process can already be started during an automated filling phase of the suspension. Also, the time of flowing or flowing on to a next process step can be used for the bleaching process and thus an effective bleaching time can be greatly reduced.

Another preferred embodiment is that at least one second electrode for plasma generation is present. By selectively providing a second electrode at locations which are advantageous for the bleaching process, the plasma generated can be used or the generated gas discharge can be applied specifically to the suspension or in the suspension.

A further gradient of the bleaching result is achieved in that at least one of the electrodes is arranged in such a way that it comes into contact with the suspension when the suspension is filled in or flows through the treatment volume.

In a further preferred embodiment, at least one of the electrodes is arranged such that the plasma is generated, preferably for the most part, in a surface-near volume below or above the surface of the filled suspension. By a - preferably pulsed - discharge in the near-surface gas region of the suspension, in particular pulp, between an electrode system, radicals generated in the gas discharge can easily enter the suspension by diffusion.

With further advantage, the electrodes are formed flat, wherein in particular the second electrode is at least partially submersed in the suspension and / or the first electrode is arranged parallel to the second electrode outside the suspension. The already mentioned diffusing of, for example, radicals into the suspension takes place in this way even more efficiently. Such an arrangement preferably causes a hybrid discharge.

It is also expedient that the electrodes are formed flat, wherein the first electrode and the second electrode are arranged parallel to each other in the near-surface region of the suspension. The plasma is applied in an advantageous manner, for example in the near-surface region of a bleaching tub, by means of a planarized electrode system. If the suspension flows, preferably during papermaking, onto a sieve and is thus distributed over a wide area, a bleaching device with a surface-configured electrode system can be advantageously used.

According to a further embodiment feature, a boundary wall of the treatment volume is prepared as an electrode. By this type of device, the plasma or the gas discharge can also be applied to the entire surface, which forms the suspension in the treatment volume.

Furthermore, the device can be designed such that the treatment volume is designed as a pipeline, in particular as a connecting element, for the transport of the suspension. A device for transporting the suspension can thus be advantageously used both as a transport device and as a bleaching device.

In a device according to the invention of the electrode system, preferably at least one electrode is designed as a plate.

In particular, the electrodes are arranged as at least two opposing, preferably mutually parallel, plates.

According to a further embodiment of the bleaching device, at least one electrode is designed as a wire.

Furthermore, it is expedient that at least one electrode is designed as a wire mesh, in particular as a wire mesh.

Furthermore, the bleaching device can be prepared in such a way that at least one electrode is designed as a grid, in particular as an arrangement of right-angled or obliquely crossing round bars and / or flat bars, preferably in the form of a sieve.

In a further advantageous embodiment of the invention, the electrodes are at least two opposing, preferably arranged parallel to each other, arranged grid. In a flowing suspension, in particular a falling curtain of suspension, the electrode arrangement can be used with advantage for a two-sided application of plasma to the suspension curtain.

In a further preferred embodiment of the bleaching device, preferably at least one electrode has one or more tips. It is known that particularly high field strengths occur at electrodes with tips, which can be used here in an advantageous manner for plasma formation.

In another embodiment variant of the bleaching apparatus, at least one electrode is preferably designed as a tube. For example, a discharge opening of the bleaching apparatus expediently opens into the pipe. During the flow through or the outflow of the suspension through the tube, the suspension, in particular the fibers or pulps contained therein, can be bleached by means of the electrode designed as a tube.

Further preferred design features of the bleaching apparatus, in particular the electrode arrangements of the bleaching apparatus, are represented by the claims 20-22.

In a further preferred embodiment of the invention, the bleaching device has a means for injecting gas, in particular air or oxygen, preferably pure oxygen or oxygen with, for example, noble gas as the carrier gas, into the treatment volume. By this advantageous arrangement, preferably finely divided air bubbles or oxygen or oxygen with a carrier gas such as argon, flowed into the suspension. By means of the means for injecting gas finest "gas bubbles" are present in the discharge area. With the help of these "gas bubbles" can be generated in a particularly advantageous manner radicals which dissolve quickly and well distributed in the suspension.

After the process-side solution of the aforementioned object is provided by the invention that the suspension or a dilution water to be added with, preferably non-thermal, large-area plasma brought under contact at least atmospheric pressure, the plasma generated in the immediate vicinity of the suspension or the dilution water or in the suspension or in the dilution water or in the immediate vicinity of the suspension or of the dilution water, a gas discharge, in particular a corona discharge, is generated under at least atmospheric pressure. The direct treatment of the suspension or of the dilution water, in particular pulp fibers, with "cold plasma" generates radicals in the suspension or in the dilution water. These radicals trigger bleaching chemical reactions in the suspension or in the fibers.

Advantageously, the plasma is generated at a distance of <20 cm, preferably <10 cm, preferably <5 cm from the suspension. To achieve a good bleaching result, it is advantageous to generate the plasma in the immediate vicinity of the suspension.

With particular advantage, especially in the paper industry, the suspension is suitable for the production of paper, cardboard or cardboard.

A preferably deposited suspension may be used as a moist or wet leaf. Advantageously, the wet or wet sheet is treated with plasma.

In a particularly advantageous manner, high-voltage pulses having a duration of less than 10 μs are generated between electrodes to produce the plasma or the gas discharge. The use of such short high voltage single pulses has been found to be particularly advantageous, whereas the use of radio frequency (RF) or microwave pulses or high voltage single pulses of more than 10 μs duration is far less efficient.

The plasma or the gas discharge is preferably applied to the suspension before and / or during the formation of the leaves, in particular when passing through or via a sieve device. It is advantageous here that the plasma or the gas discharge is applied at different locations within a papermaking process.

In order to achieve the highest possible treatment efficiency, preferably when bleaching, it is advantageous that the suspension is brought into contact with the plasma on both sides or treated by means of the gas discharge.

Advantageously, the plasma or the gas discharge is used for bleaching the suspension, the pulp or the pulp, in particular in a digester, in a bleaching container or in a conduit.

In this case, it is of particular advantage that the suspension, the pulp or pulp, is brought into contact with at least one electrode for generating the plasma or the gas discharge.

Preferably, the plasma or the gas discharge is generated in the suspension. To initiate a possible streamer discharge with efficient radical generation in the suspension, it is advantageous to generate the plasma directly in the suspension with short high voltage single pulses. When using long pulses, the largest part of the pulse energy is converted into heat. The reason lies in the high conductivity of the suspension, which is mixed with a variety of chemicals, so that the largest part of the pulse energy remains unused when using long pulses. Conveniently, the method is applied to various types or states of suspensions. In a preferred application, the content of carrier liquid, in particular water, in the suspension is in the range between 40% and 99.9%, preferably in the range between 80% and 98% and in particular in the range between 85% and 98%.

Advantageously, radicals are generated in the plasma or by means of the gas discharge, which act on the fibers. These radicals trigger bleaching chemical reactions that either replace bleach chemicals or greatly reduce their consumption.

It is particularly preferred and expedient for different states of suspensions to be used in a paper, board or paperboard production process, in particular at different process stages, for radicals of different types or compositions. Possible process stages, especially in a papermaking process, can be: cooking, painting, bleaching, sifting, pressing. Advantageously, already during the cooking of the starting materials, the suspension can be treated with plasma or a gas discharge. Also in screening, which is the precursor to sheet formation in a papermaking process, the suspension is preferably treated with a different type of radical than used in cooking.

In a further preferred embodiment of the invention, the suspension is exposed within a process stage in a paper or paperboard manufacturing process radicals of different nature or composition, preferably sequentially in time. Advantageously, such an optimal treatment result is achieved step by step.

Ozone (O ₃ ), hydrogen peroxide (H ₂ O ₂ ), hydroxyl radicals (OH), HO ₂ and / or HO ₂ ^- are preferably generated as radicals. When using H ₂ O ₂ as an OH radical source in addition, non-radical reaction pathways are possible. there Adducts of nucleophiles and H ₂ O ₂ , which are stronger oxidizing agents than the hydrogen peroxide itself, are preferably formed.

Advantageously, during bleaching in the suspension or in the pulp or in the pulp, the plasma or the gas discharge is applied in such a way that as radicals increased ozone (O ₃ ) and / or hydrogen peroxide (H ₂ O ₂ ) is formed.

In another advantageous embodiment, the plasma or the gas discharge is preferably applied during sieving and / or in / in the areal distributed suspension or pulp or pulp or in the forming or formed, still unpressed sheet in such a way that as radicals increased hydroxyl radicals, HO ₂ and / or HO ₂ ^{- is} formed.

It is expedient that a generation rate of the radicals and / or the composition of the radicals generated be controlled by influencing an amplitude, a pulse duration and / or a pulse repetition rate of the high voltage pulses. Since the concentration of radicals generated by an electrical process and thus very well controlled in real time, such a method is very economical and can be readjusted within a very short time for different treatment outcomes.

It is also expedient that a concentration of the generated radicals is measured to control and regulate the rate of generation and / or the type of radicals generated.

Furthermore, it is expedient that a property of the suspension, preferably a quality property, in particular its opacity, gloss, whiteness, fluorescence or color point, is measured to control and regulate the rate of production or the composition of the radicals produced. On the basis of the measurement of the quality properties, a feedback message is obtained which allows optimal control of the treatment process.

With regard to an automation solution used for the process, it is of particular advantage that the concentration or the property "online" is measured.

In order to control or control the generation rate of the radicals, it is preferable to vary the amplitude of the high voltage pulses at a constant repetition rate.

Furthermore, the repetition rate of the high-voltage pulses at constant amplitude is preferably changed in order to influence the generation rate.

A further increase in the treatment result, in particular a bleaching result, is achieved by enriching the suspension, the pulp, or the pulp, preferably with oxygen, for bleaching in the plasma-exposed area.

It is also advantageous with regard to a treatment result that a high-voltage pulse duration of less than 100 ns is used in the suspension, in the pulp or in the pulp, preferably for bleaching. For example, if the electrode system of a bleaching device is arranged completely inside the suspension, it is very advantageous to work with small high-voltage pulse durations due to the high conductivity of the suspension.

Furthermore, it is expedient for a good treatment result that areal distributed suspension, pulp or pulp or forming or formed, still unpressed sheet, especially in screening, in the plasma-exposed area is surrounded by a water vapor-enriched atmosphere.

Furthermore, it is expedient that, in the case of a surface-spread suspension, pulp or pulp or a sheet which is still not pressed and which forms or is formed, in particular when sieving, a high voltage pulse duration of 100 ns to 1 μs is used.

Furthermore, it is advantageous that, in the case of a surface-spread suspension, pulp or pulp or sheet which still forms or is undeformed, in particular during screening, a high-voltage amplitude corresponding to at least twice the value, preferably at least three times the value, of a corona threshold voltage the electrodes are applied.

Preferably, a DC corona discharge is generated to generate the plasma or the corona discharge and the DC voltage corona discharge superimposed on the high voltage pulses. The superposition of the high voltage pulses on a DC voltage has the particular advantage that the high-energy high-voltage pulses can start from a very high energy level.

Depending on the lifetime or type or composition of the generated radicals, it is also appropriate that a pulse repetition rate between 10 Hz and 5 kHz, in particular from the range of 10 Hz to 10 kHz, is used.

Furthermore, it is advantageous if the power coupling of electrical energy into the plasma is controlled predominantly via the regulation of amplitude, pulse duration and pulse repetition rate of the superposed high-voltage pulses.

Preferably, for suspensions with extremely high conductivity, it is expedient that high-voltage pulses having a duration of less than 3 μs, preferably less than 1 μs, preferably less than 500 ns, are used.

It is also expedient that a homogeneous, large-volume plasma with high power density is produced, without resulting in plasma constrictions or punctures. By generating a "stable" plasma, the rate of generation can be kept high and constant; on the other hand, plasma constrictions occur or breakdowns, the production rate drops again.

It is furthermore preferred that a DC voltage of such height is used that a stable DC corona discharge is formed in the plasma only in conjunction with superposed high-voltage pulses.

With particular advantage, the DC voltage used is below the voltage for stable operation without high-voltage pulse superimposition.

Furthermore, it is expedient that the total amplitude used (DC voltage + pulse amplitude) is above the static breakdown voltage of the electrode arrangement.

It is expedient that, preferably for a high power input, the total amplitude used corresponds to two to five times the static breakdown voltage of the electrode arrangement.

For the application of the preferably used DC voltage, it is of further advantage if the amplitude of the high voltage pulses is between 10% and 1000% of the DC voltage used.

A further increase in a treatment result or a bleaching process is preferably achieved by generating a gas flow perpendicular to the electrode arrangement.

Alternatively, it is possible that a gas flow is generated parallel to the electrode assembly.

In an advantageous embodiment of the invention, impurities formed in the suspension by organic dyes, biocatalytic substances and / or microorganisms and / or other biological material are reduced. Impurities in the sense of the invention are, for example, dissolved organic substances which are undesirable in the suspension or generally in a water system of a bleaching apparatus or a papermaking plant. Such and other contaminants often cause dewatering deterioration, leading to unfavorable sheet formation and lower opticity. 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 spots and holes in the paper at a papermaking facility. Colored impurities are caused by the dyes used for example in today's printing process, 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, water-soluble red dyes are responsible for the water becoming a reddish tint which transfers to the final product, preferably a paper. A high desired whiteness, for example in the production of white papers, can not be achieved with colored water. In particular, under conditions of restricted water cycles, an increased increase of the microorganisms contained in the water is generally observed. For example, the dissolved oxygen present in the water is rapidly consumed and this can lead to the formation of anerobic conditions in the water. The microorganisms can then multiply rapidly and metabolic products of these microorganisms, for example, lead to strong odor in the form of hydrogen sulfide and / or organic acids or yeasts and bacteria. In addition, in some cases, by the action of the above-mentioned metabolic products of the anerobic microorganisms, corrosion of plant parts. Cause are in particular microorganisms which, inter alia, carbohydrate-splitting enzymes, such as the enzyme cellulase with which the cellulose present in the preferably paper-making 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. A biocatalytic substance is understood to mean, for example, a chemical interaction between a protein and other particles (molecules, ions, protons, electrons) during which the nature of these particles changes. The generated radicals have a favorable effect on the reduction of the impurities and the addition of complementary dyes or biocides can be limited or prevented.

In a further preferred embodiment of the invention, adhesive impurities are reduced. In a recycling process of, for example, waste paper as a starting material, dissolved and very finely divided "stickies" from the waste paper pass into the papermaking plant. "Stickies" is a term for small hotmelt or adhesive contaminants, which later appear as mistakes in the paper or in cardboard as, for example, disturbing stains. In particular, in a waste paper processing, the water used for this purpose is heavily contaminated. The adhesive contaminants in a pulp or fiber suspension as an intermediate and in the general circulation waters of a papermaking machine tend to deposit on, for example, papermachine clothing such as felting and screening, as well as on cylinders and rollers. In addition, they lead to defects in the paper ultimately produced, which can lead to errors in the further processing or limit their use value. These sticky impurities are now one of the biggest problems in the recycling of waste paper. While so-called macro Stickis can be largely separated using mechanical separation process, so-called micro Stickis are very difficult to remove from the suspension or generally from a water cycle. Micro stickies are so small that they can also pass through a slotted screen with a slot width of approx. 100 μm. By treating the suspension, including the adhesive contaminants, a surface of the adhesive contaminants is changed so that they reduce their adhesive properties or lose completely. As a result, it is advantageously avoided that the contaminants continue to deposit on, for example, clothing, felts, rolls and in a dryer section.

In a further expedient embodiment of the invention, the dilution water is additionally treated with the plasma or the gas discharge before the dilution water is added to the suspension. The treatment of the dilution water with cold plasma or a gas discharge triggers chemical reactions in the dilution water or in the stock suspension formed with the dilution water, which already at an early stage, for example in a bleacher upstream stock preparation plant, the quality properties of the suspension to be used later improve significantly. The dilution water thus treated can be used in addition to the bleaching of the pulps also for reducing impurities.

FIG 1

eine schematische Darstellung einer Papierherstellungsanlage mit einer Siebvorrichtung, einer Pressenvorrichtung und einer Veredelungs- und/oder Trockenanlage,

FIG 2

eine Bleichvorrichtung nach der Erfindung,

FIG 3

eine Darstellung (Schnitt) einer Anordnung zur Erzeugung von Radikalen in Koronaplasmen in Pulpe oder Luft: Parallelplatten- oder Rohranordnung mit Draht, dem eine gepulste Hochspannung überlagert wird,

FIG 4

eine Prinzipdarstellung von Impulsen zur Erzeugung von Radikalen in Koronaentladungen in Luft oder wässrigen Medien bei Einsatz kurzer (typisch < 1 µs) Hochspannungsimpulse mit hoher Impulswiederholrate,

FIG 5

bis FIG 10 Elektrodenanordnungen und Elektrodensysteme zur Erzeugung von Koronaentladungen: Platte-Platte-, Platte-Draht-Platte-, koaxiale Draht-Rohr-, Spitze-Platte-, Mehrfachspitzen-Platte-, Gitter-Platte (Rohr)-, Gitter-Gitter-Anordnungen,

FIG 11

eine hybride Entladung, wobei sich eine Elektrode vollständig oberhalb des Mediums auf dem Sieb befindet, wogegen die zweite Elektrode durch das Sieb selbst gebildet wird,

FIG 12

eine Platten- oder Gitteranordnung mit gekrümmten Oberflächen zur Anpassung an Gefäßwände bzw. Nutzung derselben als Elektrode, konzentrische Elektroden in Rohrform zur Nutzung der vorhandenen Verrohrung oder Türme für die Pulpe als Reaktorgefäß,

FIG 13

eine gepulste Entladung im oberflächennahen Gasraum über Stoffauflauf auf dem Sieb mit Vielfachdraht-Platte-Anordnung, und

FIG 14

ein gepulstes Koronaentladungssystem mit koaxialem Draht-Rohr, mit eingeperlten, feinstverteilten Gasblasen, so dass im Entladungsbereich feinste Gasperlen vorhanden sind und eine Streamerbildung vorwiegend in den Gasblasen abläuft,

FIG 15

eine schematische Darstellung einer Stoffaufbereitungsanlage mit Plasmareaktoren,

FIG 16

Plasmareaktor für ein Verdünnungswasser.

Preferred, but by no means limiting embodiments of the invention will now be explained in more detail with reference to the drawing. For clarity, the drawing is not drawn to scale, and certain features are shown only schematically. Corresponding parts are provided in the figures with the same reference numerals. In detail, the shows

FIG. 1

a schematic representation of a papermaking plant with a screening device, a press device and a finishing and / or drying plant,

FIG. 2

a bleaching apparatus according to the invention,

FIG. 3

a representation (section) of an arrangement for generating radicals in corona plaques in pulp or Air: parallel plate or tube assembly with wire overlaid with pulsed high voltage,

FIG. 4

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

FIG. 5

to FIG. 10 Electrode arrays and electrode systems for generating corona discharges: plate-plate, plate-wire-plate, coaxial-wire-tube, tip-plate, multi-tip-plate, grid-plate (tube), grid-grid-arrangements,

FIG. 11

a hybrid discharge, with one electrode located completely above the medium on the screen, whereas the second electrode is formed by the screen itself,

FIG. 12

a plate or grid assembly with curved surfaces for fitting to vessel walls or using same as an electrode, concentric electrodes in tube form to use the existing casing or towers for the pulp as a reactor vessel,

FIG. 13

a pulsed discharge in the near-surface gas space over headbox on the wire with multi-wire plate arrangement, and

FIG. 14

a pulsed corona discharge system with coaxial wire tube, with beaded, very finely divided gas bubbles, so that in the discharge region finest gas bubbles are present and a streamer formation takes place mainly in the gas bubbles,

FIG. 15

a schematic representation of a stock preparation plant with plasma reactors,

FIG. 16

Plasma reactor for a dilution water.

FIG. 1 shows a schematic representation of a complex papermaking plant 1, as used in today's paper mills. Their construction and the combination of different aggregates are determined by the type of paper, cardboard and paperboard types to be produced as well as the raw materials used. The papermaking plant 1 has a spatial extent of about 10 m in width and about 120 m in length. The papermaking plant produces up to 1400 m of paper per minute 27. It only takes a few seconds from the first impingement of the suspension or the pulp 39 on the screening device 9 to the finished paper 27, which is finally rolled up in a reel 15. Diluted with water at a ratio of 1: 100, the fibers 30 (see FIG. 2 ) applied together with excipients on the sieve 9 with the sieve 10. The fibers are deposited on the screen 10 side by side and on each other. The white water 23 can drain or be sucked off by means of several suction chamber regions 24. In this way, a uniform fiber composite, which is further dehydrated by mechanical pressure in a press device 11 and with the aid of steam heat. The entire papermaking process is essentially subdivided into the areas of stock preparation, paper machine, finishing and equipment.

Waste paper and, as a rule, also pulp reach the paper mill in dry form, while wood pulp is normally produced in the same factory and pumped into the material center 3 as a fiber / water mixture, ie a suspension of unvarnished pulp. Waste paper and pulp 30 (see FIG. 2 ) are also added with the addition of water in a fiber trough 35 (FIG. FIG. 2 ) dissolved. Non-paper components are discharged via various sorting aggregates (not shown here). In the fabric center 3, depending on the desired type of paper, the mixture of different raw materials. Fillers and auxiliaries are also added here to improve paper quality and increase productivity.

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

Another dewatering process is carried out by mechanical pressure in the press device 11. In this case, the paper web 27 is guided by means of an absorbent endless felt cloth between rolls of steel, granite or hard rubber and thereby dehydrated. The white water 23 taken up by the suction chamber region 24 is fed to a sorter 5 in part and returned to another part to a fabric scavenger 17. The press device 11 is followed by a drying system 13. The remaining residual water is evaporated in the drying plant 13. Slalom-like, the paper web 27 passes through several steam-heated drying cylinders. In the end, the paper 27 has a residual moisture of a few percent. The water vapor formed in the drying plant 13 is sucked off and passed into a heat recovery system, not shown.

For a treatment of the fiber suspension 39 according to the invention, in a first exemplary embodiment a first electrode 43 is arranged below the sieve device 9 and a second electrode 44 is arranged above the sieve device 9 between the headbox 7 and the starting region of the sieve device 9. The electrodes 43 and 44 are arranged such that the surface-distributed fiber suspension 39 extends between them. So that a large-area plasma under atmospheric pressure in the immediate vicinity of the fiber suspension 39 can be produced for the treatment of the fiber suspension 39, the electrodes 43 and 44 are connected to a high-voltage pulse generator 46. With the aid of this high-voltage pulse generator 46, a large-volume plasma with a large cross section and with high power density is produced between the electrodes 43 and 44. Here, a plasma density is homogeneously distributed over the treatment area which is covered by the electrodes 43 and 44. According to the invention, this large-volume plasma with high power density is produced by superimposing intensive, short-lasting high-voltage pulses having a high pulse repetition rate of 1 kHz on a DC corona discharge. In this mode, a very homogeneous, large-volume plasma with a high power density produced without the plasma constrictions known in DC corona discharges.

In order to support the treatment effect which the cold large-area plasma exerts on the fiber suspension, oxygen with argon as carrier gas is optionally introduced into the treatment space between the electrodes 43 and 44 via a gas distributor 81. Hydroxyl radicals are particularly advantageously produced with the aid of the oxygen-argon mixture. Hydroxyl radicals are particularly aggressive and oxidizing, thereby a bleaching effect is achieved at the only a few seconds in the treatment area between the electrodes 43 and 44 lingering fiber suspension.

Analogous to that described above, an electrode system 47, 48 in the press device 11 generates a large-area plasma for the treatment of the paper web 27. The first electrode 47 in the press apparatus 11 is designed as a semicircular grid electrode. Due to the semicircular configuration of the electrode 47, it can follow the course of the paper web over a transport roller 12. The second electrode 48 in the press device 11 is configured as a plate electrode and arranged such that the transport roller 12 can be guided between the electrodes 47 and 48. In order to stimulate the formation of radicals in the plasma here as well, the plasma treatment area is optionally also supplied via the gas distributor 81 with the gas line 80 with an oxygen-argon mixture here.

The pressing process compacts the paper structure, a strength increases and a surface quality is decisively influenced. By treating the pressed paper with cold plasma, especially with the generated radicals, the molecular structure of the paper surface is further altered. The strength of the paper 27 is increased and printability improved.

With the above-mentioned electrode arrangements 43 and 44 as well as 47 and 48, it is possible according to the inventive method to guide the paper web 27 between streamer discharges. A streamer is a special form of a linearly moving plasma cloud or a developing discharge channel that forms due to the excited high external field strength. An assembly of such streamer takes place within less than 10 ns and merges very quickly into a thermal breakdown channel. The aforementioned arrangements of the electrode systems, with the paper web 27 between the electrodes used for streamer discharge, is particularly advantageous, as the paper 27 thereby partially acts as a dielectric barrier, thereby suppressing the transition from the streamer puncture.

FIG. 2 shows a bleaching device 38 according to the invention with a second embodiment. A raw material 30, in particular pulp, is conveyed via a conveyor belt 33 into a fiber trough 35. In the fiber trough 35, the raw material 30 is mixed with water and pumped via a pipeline 36 into a bleaching trough 37. A first electrode 43 'and a second electrode 44' are each designed as a circular-area grid electrode. The first electrode 43 'is arranged in the gas space of the pulp fiber suspension 39 filled in the bleaching trough 37. The second electrode 44 'is arranged inside the bleaching trough 37 and is thus completely covered by the pulp fiber suspension 39. Between the two electrodes 43 'and 44', a large-area cold plasma is generated by means of the high-voltage pulse generator 46.

, HOO ^{- -} by direct treatment of the pulp fiber suspension 39 with the cold plasma, the radical OH in the suspension 39 is preferably, O, O ₃ produced. These radicals trigger a bleaching chemical reaction. The high voltage pulse generator 46 is operated to generate high voltage pulses of 1 μs duration between the electrodes 43 'and 44'. One for the generation of radicals and ozone in the pulp fiber suspension necessary DC voltage is approximately at some 10 kV to 100 kV. The high voltage pulses are superimposed on the DC voltage to form a total amplitude of a few 10 kV to over 100 kV. By treating the pulp fiber suspension 39 with a cold electrical discharge, so the plasma, the radicals are generated in situ. Thus, large total amounts of radicals can be introduced into the suspension 39. The radicals are also very finely distributed in the suspension generated, so that the previous effort required to mix chemicals with the suspension can be reduced.

For a further increase in the bleaching process, an oxygen-argon mixture, which has been treated in a gas distributor 81, is introduced into the bleaching trough 37 via a gas line 80.

FIG. 3 shows as a third embodiment, a sectional view of a bleaching vessel. In the middle of the bleaching vessel, a high voltage electrode 50 is arranged. The outer jacket of the bleaching vessel is prepared as a counterelectrode 51. In the bleaching vessel is a pulp fiber suspension 39. Between the electrodes 50 and 51, a streamer 53 is shown. Radicals 59 are generated in streamers by the collision of energetic electrons with water molecules or suspension molecules, thereby dissociating or exciting them. Upon dissociation, radicals 59 are immediately released, while upon excitation by a subsequent radiant transition, UV light is generated. This generated UV light in turn reacts with water molecules and dissociates them.

This in FIG. 3 Bleaching vessel shown can also be used as a device for the passage of the suspension 39. For this purpose, the device is not designed as a bleaching vessel, but as a kind of tubular reactor, ie without a bottom. With this tube reactor, a passage of the suspension can be carried out with simultaneous plasma generation.

With regard to colored impurities, these radicals 59 and oxidants 57 directly attack the high-molecular-weight dyes and destroy them to such an extent that the color effect of the molecules is eliminated.

With regard to microbiological contaminants, these are attacked and destroyed by the UV light, the radicals 59 and oxidants 57. The simultaneous action of several such biocidal components a synergy effect is achieved, which leads to a particularly effective sterilization of the suspension 39. In particular, the high electric field also applied at the beginning of the process leads to a further increase in synergy due to pre-damage of the biological cells by electroporation of the cell walls, which are then particularly vulnerable to the subsequently generated chemically active agents, in particular the radicals 59 and the oxidants 57.

Microorganisms which release, for example, carbohydrate-cleaved enzymes such as the enzyme cellulase, with which the cellulose in the suspension 39 is decomposed as a fiber base and serves as a decomposed, short-chain carbohydrate for the microorganisms, are also inhibited or completely destroyed. The microorganisms are killed, minimizing cellulase production. By a simultaneous degradation of a catalase can build up in addition to the radicals and a H ₂ O 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. 4 the voltage curve of the high voltage pulses used is shown. A first pulse 66 and a second pulse 67, each having a pulse width 62, have a spacing of one pulse repetition time 63. The abscissa shows the time in ms and the ordinate the voltage in kV. The units are chosen arbitrarily. A level of about 100 kV DC voltage coincides with the abscissa shown. The illustrated pulse voltage is thus superimposed on the DC voltage. The result is a total amplitude of about 500 kV. The pulses 66 and 67 have a pulse width 62 of less than 1 μs, wherein the individual pulses 66, 67 have a high rising edge with a rise time 64 and a less steeply sloping edge. The pulse repetition time 63 is typically between 10 μs and 100 ms.

In this case, the individual pulses 66, 67 have such a total amplitude that a predefined energy density is achieved beyond the predetermined direct voltage. As mentioned, the pulse rise time 64 is usually short compared to the pulse drop time. By such a kind of pulses is achieved that electrical breakdowns that would lead to spatial and temporal disturbances in the homogeneous plasma density distribution can be avoided.

FIG. 5 to FIG. 10 show further examples of electrode systems for generating corona discharges in preferably aqueous media, in particular for alternative use in the aforementioned embodiments. In FIG. 5 For example, a plate-and-plate arrangement of a first plate 70a as an electrode and a second plate 70b as an electrode is illustrated. 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 to the high voltage pulse generator 46 via a high voltage cable. The second plate 70b forms the counter electrode and is connected as a grounded electrode to the high voltage pulse generator 46 in connection.

A corresponding arrangement with specially flat plate electrodes is in FIG. 6 shown. Again there are two solid plate electrodes 70a and 70c at a fixed distance with a high voltage electrode 71 in the middle. In this plate-wire plate assembly, the high voltage electrode 71 executed as a solid wire and connected to the high voltage output of the high voltage pulse generator 46. The grounded plates 70a, 70c are also in communication with the high voltage pulse generator.

FIG. 7 shows a wire-tube arrangement as an electrode system. A high-voltage electrode 71 projects centrally into a cylindrical electrode 72. As in FIG. 6 the high voltage electrode 71 is made as a solid wire and connected to the high voltage pulse generator 46. The cylindrical electrode 72, which is preferably configured as a wire mesh, is grounded and communicates with the high voltage pulse generator 46.

FIG. 8 shows a tip-plate assembly as an electrode system. The example, three tips 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 of the tip electrodes 73 to the plate electrode 74 is adjustable and thus can be adapted for different process conditions.

FIG. 9 shows an electrode system assembly 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 arranged centrally between two solid plates 70d and 70e. The plates 70a and 70b are connected via a 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.

FIG. 10 shows an electrode system as a grid-grid arrangement. Analogous to FIG. 5 Here, a first grid 75a and a second grid 75b are parallel to each other. The first grid 75a forms the high voltage electrode and is with the high voltage pulse generator 46 connected. The second grid 75b forms the grounded counter electrode and communicates with the high voltage pulse generator 46.

All of the above-mentioned electrode arrangements have in common that, instead of the connection of high-voltage pulses 66, 67 - as in FIG. 3 shown - can also be applied to produce a continuous electrolysis with a DC voltage, for example in the range of 1 V to 10 V, in particular from 2 V to 5 V.

A hybrid discharge in which an electrode 75a is entirely outside a pulp 39 to be bleached and a second electrode 76b is wholly or partially immersed in the pulp 39 is shown in FIG FIG. 11 generated. 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 suspension 39, a first charge cloud 68a is formed. With the aid of this charge cloud 68a, the chemically active substances can enter the suspension 39 and eliminate unwanted impurities in addition to the bleaching effect. Also in the suspension 39, charge clouds 68b, 68c are preferably formed at locations with locally increased field strength. The charge clouds 68a, 68b, 68c release in the suspension 39 radicals, such as O, OH, HOO, but above all strong oxidants such as ozone and / or H ₂ O ₂ . Among other things, these chemically active substances destroy microorganisms such as bacteria and yeasts with high efficiency.

In FIG. 12 is shown as another embodiment, a bleaching tub with a vessel wall 77 in a plan view. For the bleaching tub, a plate or grid arrangement with curved surfaces for adaptation to the vessel walls or use of the vessel walls is used as the electrode. A multiple wire electrode 79 is considered a concentric electrode, arranged following the course of the vessel wall 77 and communicates with the high voltage pulse generator 46 in connection. 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 each other and thus form the grounded counterelectrodes which are in communication with the high voltage pulse generator 46.

In order to generate pulsed discharges in the near-surface gas space above the pulp 39 is in FIG. 13 represented as a further embodiment, a special electrode arrangement. A high-voltage electrode 50 comprises a plurality of electrically connected rod electrodes and is arranged in the near-surface gas space of the pulp 39 such that their rods are parallel to the surface. A grounded counter electrode 51 is designed as a solid plate and arranged in distributed over the entire surface equidistant distances to the high voltage electrode 50. In this electrode arrangement as well, 39 charge clouds develop at the boundary layer between air and suspension, as indicated for example by the charge clouds 68d and 68e. The charge clouds also ensure penetration of the chemically active substances into the suspension 39. The suspension 39 is guided in this case in an upwardly open suspension channel 37a. The wall of the suspension channel 37a is additionally connected to the counterelectrode 51.

FIG. 14 shows in a last embodiment, a pulsed corona discharge system in an aqueous solution or pulp 39. The electrode system is analogous to FIG. 3 formed as a coaxial wire tube electrode system. The high voltage electrode 50 is arranged coaxially with the counter electrode 51 forming the vessel wall. In order to support the bleaching effect, finest gas bubbles are introduced into the discharge area via a gas line 80 by means of a gas distributor 81 initiated. In the gas bubbles 82 and 83 are preferably formed to FIG. 3 explained streamers. Owing to the streamer discharges, oxidants 57 are formed. Thus, certain radicals are generated in the suspension.

FIG. 15 shows a schematic representation of a stock preparation plant 1a. With a dissolver 90, fibrous materials are suspended in an aqueous binder at the beginning of the stock preparation process. The dissolution device 90 is connected to a chemical addition device 91 via a piping system. Further, the piping between the dissolver 90 and the chemical addition device 91 is connected to a first dilution water inlet 26a. The chemical addition device 91 is connected to a first purification stage 92 via a pipe system. The first cleaning stage 92 is further connected to a flotation stage 93 via a pipe system. Between the first purification stage 92 and the flotation stage 93, a second dilution water inlet 26b is arranged. A second purification stage 94 connects to the flotation stage 93 via a piping system. From the second purification stage 94, the suspension or pulp also passes through a piping system in a thickening device 95. The thickening device 95 is connected via a piping system with a bleaching container 96 in connection. From the bleaching container 96, the suspension or pulp 39 is pumped into a chest 97. From the bin 97, the treated fibrous materials or pulp 39 are available for further processing.

The chemical addition device 5 may add various chemical adjuncts, i.a. Bleaching agents supplementing a plasma bleaching effect.

As the suspension or pulp 39 is pumped through the stock preparation process, dilution water 26 is added at locations 26a and 26b. In the material resolution of fibrous materials in the dissolution apparatus 3 is preferably carried out with a consistency of up to 17%. Thereafter, the suspension of fibrous materials for the subsequent chemical addition device 91 and the first purification stage 92 with the dilution water 26 at the dilution water inlet 26a is diluted to about 5.8 to 6%.

The dilution water 26 is treated at the first dilution water inlet 19a by means of a first plasma reactor 23a with a cold plasma or a gas discharge. By treating the dilution water 26 before the actual dilution point at which the dilution water 26 is mixed with the suspension in the pipeline system, certain radicals are generated in the dilution water 26 (OH ^- , HOO ^- , O, O ₃ ). These radicals, which pass through the dilution water 26 into the stock suspension, trigger bleaching chemical reactions in the stock suspension at the beginning of the stock preparation process. Also, they can mask or eliminate sticky contaminants of the pulps. These bleaching chemical reactions or radicals act directly on the fibrous materials and thus provide the desired bleaching result. For the subsequent flotation stage 93, between the first purification stage 92 and the flotation stage 93, the stock suspension is diluted to approximately 1 to 1.3% by a second dilution water feed 26b. Also at the point 26b, the dilution water 26 is treated via a second plasma reactor 23b before being mixed with the suspension with a cold plasma or a gas discharge.

The plasma reactors 98a and 98b are preferably arranged directly in the vicinity of the respective feed points of the dilution water 26, in particular at a distance such that the remaining pipe length to the feed point is preferably a few meters, preferably about 50 cm, in particular only a few cm.

After passing through the second cleaning stage 94, the stock suspension 39 is thickened with a consistency of about 1% in a thickening device 13. A further treatment with a kneading disperger, for the reduction of, for example, residual color particles, can optionally be used at this point.

FIG. 16 shows one of the two in a first embodiment example FIG. 15 known plasma reactors 98a and 98b in a sectional view. The plasma reactor 23 a is prepared in such a way that an unhindered flow through the dilution water 26 is made possible. The dilution water 26 falls or flows - preferably as a free water jet in the flow direction S - through a gap, which is given by two spaced-apart electrodes 43 "and 44". The first electrode 43 "is connected via a high-voltage line to a high-voltage pulse generator 46. To generate a plasma, a corona discharge or a gas discharge between the two electrodes 43" and 44 ", the second electrode 44 is also connected to the high-voltage pulse generator 46 via a high-voltage line With this arrangement, it is possible to create a series of differently oxidizing radicals in the dilution water 24 simultaneously, so that after later intimate mixing with the more highly consistent aqueous suspension of fibrous materials, these fibers can be treated with free radicals.

Claims (66)

1. Bleaching device (38) for bleaching non-woven fibrous materials in a suspension, in particular as a pulp or a fibre slurry in or at a treatment volume provided by delimiting walls, wherein the suspension can be filled into or can flow through the treatment volume, characterised by at least one first electrode (43') and a high voltage pulse generator (46) which is connected to the first electrode (43') and with which a plasma can be generated in the treatment volume and/or in the immediate vicinity thereof.
2. Bleaching device (38) according to claim 1,
   characterised in that the plasma is generated at a distance of less than 20 cm, preferably less than 10 cm, more preferably less than 5 cm from the treatment volume.
3. Bleaching device (38) according to claim 1 or 2,
   characterised in that the fibrous materials are suitable for the manufacturing of paper, paperboard or cardboard and/or can be fed to such a manufacturing process as the processing material.
4. Bleaching device (38) according to one of the claims 1 to 3, characterised in that the treatment volume is suitable to be filled with or flowed through by the suspension, preferably of a starting material (30) for paper, paperboard or cardboard manufacturing, in particular a pulp (39) to be bleached or a fibre slurry to be bleached.
5. Bleaching device (38) according to one of the claims 1 to 4, characterised in that at least one second electrode (44') is provided for plasma generation.
6. Bleaching device (38) according to one of the claims 1 to 5, characterised in that at least one of the electrodes (44') is arranged such that, with suspension filled into or flowing through the treatment volume, said electrode comes into contact with the suspension.
7. Bleaching device (38) according to one of the claims 1 to 6, characterised in that at least one of the electrodes (43', 44') is arranged such that the plasma is generated, at least mostly, in a volume close to and below or above the surface of the filled suspension.
8. Bleaching device (38) according to one of the claims 5 to 7, characterised in that the electrodes (43', 44') are configured planar, wherein in particular the second electrode (44') can be at least partially immersed in the suspension and/or the first electrode (43') is arranged parallel to the second electrode (44') outside the suspension.
9. Bleaching device (38) according to one of the claims 5 to 8, characterised in that the electrodes (43', 44') are configured planar, wherein the first electrode (43') and the second electrode (44') are arranged parallel to one another in the region of the suspension close to the surface.
10. Bleaching device (38) according to one of the claims 1 to 9, characterised in that a delimiting wall (51) of the treatment volume is configured as an electrode.
11. Bleaching device (38) according to one of the claims 1 to 10, characterised in that the treatment volume is configured as a tubular conduit (36, 72, 77), in particular as a connecting element for the transport of the suspension.
12. Bleaching device (38) according to one of the claims 1 to 11, characterised in that at least one electrode is configured as a plate (70a, 70b).
13. Bleaching device (38) according to claim 12, characterised in that the electrodes are arranged as at least two plates (70a, 70b) opposing one another and preferably extending parallel to one another.
14. Bleaching device (38) according to one of the claims 1 to 13, characterised in that at least one electrode is configured as a wire (71).
15. Bleaching device (38) according to one of the claims 1 to 14, characterised in that at least one electrode is configured as a wire mesh, in particular as a wire grid (75a, 75b).
16. Bleaching device (38) according to one of the claims 1 to 15, characterised in that at least one electrode is configured as a grid (75a, 75b), in particular as an arrangement of round rods and/or flat strips crossing one another at right angles or obliquely, preferably in the form of a sieve.
17. Bleaching device (38) according to one of the claims 14 to 16, characterised in that the electrodes are arranged as at least two grids (75a, 75b) opposing one another and preferably extending parallel to one another.
18. Bleaching device (38) according to one of the claims 1 to 15, characterised in that at least one electrode has one or more spike(s) (73).
19. Bleaching device (38) according to one of the claims 1 to 16, characterised in that at least one electrode is configured as a tube (36, 72, 77).
20. Bleaching device (38) according to claim 19, characterised in that the electrodes are configured as a tube (72) with a, preferably coaxial, wire (71) arranged therein.
21. Bleaching device (38) according to one of the claims 5 to 20, characterised in that the electrodes are arranged such that a wire (71) or a grid (75a) is arranged as the second electrode between two plates (70d, 70e) electrically connected to one another by means of at least one plate connector (70f), said plates constituting the first electrode.
22. Bleaching device (38) according to one of the claims 1 to 21, characterised in that the at least one - preferably planar configured - electrode (78, 79) is arranged at least partially parallel to a, particularly curved, lateral surface or to a delimiting wall (77) of the treatment volume.
23. Bleaching device (38) according to one of the claims 1 to 22, characterised by a means (81) for injecting gas, in particular air or oxygen, preferably pure oxygen or oxygen with, for example, a noble gas as the carrier gas, into the treatment volume.
24. Method for treating non-woven fibrous materials in a suspension, in particular as a pulp or a fibre slurry, preferably for operating the bleaching device according to one of the preceding claims, characterised in that the suspension or a dilution water (26) to be added thereto is brought into contact with, preferably non-thermal, large-area plasma under at least atmospheric pressure, the plasma is generated in the immediate vicinity of the suspension or the dilution water (26) or a gas discharge, in particular a corona discharge is generated under at least atmospheric pressure in the suspension or in the dilution water (26) or in the immediate vicinity of the suspension or of the dilution water (26).
25. Method according to claim 24,
    characterised in that the plasma is generated at a distance of less than 20 cm, preferably less than 10 cm, more preferably less than 5 cm from the suspension.
26. Method according to claim 24 or 25,
    characterised in that the suspension is suitable for the manufacturing of paper, paperboard or cardboard.
27. Method according to one of the claims 24 to 26,
    characterised in that a moist or wet sheet is used as the suspension.
28. Method according to one of the claims 24 to 27,
    characterised in that, in order to generate the plasma or the gas discharge, high voltage pulses (66, 67) with a duration (62) of less than 10 µs are generated between electrodes (43, 44).
29. Method according to one of the claims 24 to 28,
    characterised in that the plasma or the gas discharge is applied to the suspension before and/or during the sheet formation, in particular during passage through or over a wire device (9).
30. Method according to one of the claims 24 to 29,
    characterised in that the suspension is brought into contact with the plasma or is treated by means of the gas discharge on both sides.
31. Method according to one of the claims 24 to 30,
    characterised in that the plasma or the gas discharge is used for bleaching the suspension, the pulp (39) or the fibre slurry, in particular in a boiling apparatus, in a bleaching vessel (37) or in a conduit.
32. Method according to one of the claims 24 to 31,
    characterised in that the suspension, the pulp (39) or the fibre slurry is brought into contact with at least one electrode for generating the plasma or the gas discharge.
33. Method according to one of the claims 24 to 32,
    characterised in that the plasma or the gas discharge is generated in the suspension.
34. Method according to one of the claims 24 to 33,
    characterised in that the content of carrier fluid, in particular water, in the suspension is in the range between 40% and 99.9%, preferably in the range between 80% and 98% and in particular in the range between 85% and 98%.
35. Method according to one of the claims 28 to 34,
    characterised in that radicals (59) which act upon the fibrous materials are generated in the plasma or by means of the gas discharge.
36. Method according to claim 35,
    characterised in that radicals (59) of different types or compositions are used for different states of suspension in a paper, paperboard or cardboard manufacturing process, in particular at different processing steps.
37. Method according to claim 35 or 36,
    characterised in that the suspension is exposed within a processing step in a paper, paperboard or cardboard manufacturing process to radicals (59) of different types or compositions, preferably chronologically one after another.
38. Method according to one of the claims 35 to 37,
    characterised in that as the radicals (59) ozone (O₃), hydrogen peroxide (H₂O₂), hydroxyl radicals (OH), HO₂ and/or HO₂ ^- are generated.
39. Method according to one of the claims 35 to 38,
    characterised in that, during bleaching in the suspension or in the pulp (39) or in the fibre slurry, the plasma or the gas discharge is applied such that as the radicals (59), ozone (O₃) and/or hydrogen peroxide (H₂O₂) are often generated.
40. Method according to one of the claims 35 to 39,
    characterised in that, during straining and/or in the areally distributed suspension or pulp (39) or fibre slurry or in the forming or already formed, still unpressed sheet, the plasma or the gas discharge is applied such that as the radicals (59), hydroxyl (OH), HO₂ and/or HO₂ ^- are often generated.
41. Method according to one of the claims 35 to 40,
    characterised in that a rate of generation of the radicals (59) and/or the composition of the radicals (59) generated is controlled by influencing an amplitude (U), a pulse duration (62) and/or a pulse repetition rate (63) of the high voltage pulse (66, 67).
42. Method according to claim 41, characterised in that for controlling and regulating the generation rate and/or the type of the radicals (59) generated, a concentration of the radicals (59) generated is measured.
43. Method according to claim 41 or 42,
    characterised in that for controlling and regulating the generation rate or the composition of the radicals (59) generated, a property of the suspension, preferably a quality property, in particular the opacity, sheen, whiteness, fluorescence or colour location thereof is measured.
44. Method according to one of the claims 42 or 43,
    characterised in that the concentration or the property is measured "online".
45. Method according to one of the claims 41 to 44,
    characterised in that, for regulation, the amplitude (U) of the high voltage pulses (66, 67) is adjusted at a constant repetition rate (63).
46. Method according to one of the claims 41 to 45,
    characterised in that, for regulation, the repetition rate (63) of the high voltage pulses (66, 67) is adjusted at a constant amplitude (U).
47. Method according to one of the claims 24 to 46,
    characterised in that the suspension, the pulp (39) or the fibre slurry is enriched with oxygen in the plasma-generating region, preferably for bleaching.
48. Method according to one of the claims 24 to 47,
    characterised in that in the suspension, in the pulp (39) or in the fibre slurry, a high voltage pulse duration (62) of less than 100 ns is used, preferably for bleaching.
49. Method according to one of the claims 24 to 48,
    characterised in that the areally distributed suspension, pulp (39) or fibre slurry or the forming or already formed, still unpressed sheet, is surrounded in the region to which plasma is applied by an atmosphere enriched with water vapour, particularly during straining.
50. Method according to one of the claims 41 to 49,
    characterised in that a high voltage pulse duration (62) of between 100 ns and 1 µs is used on the areally distributed suspension, pulp (39) or fibre slurry or the forming or already formed, still unpressed sheet, particularly during straining.
51. Method according to one of the claims 41 to 50,
    characterised in that a high voltage amplitude (U) corresponding to at least twice the value, preferably at least three times the value of a corona operating voltage is applied to the electrodes for the areally distributed suspension, pulp (39) or fibre slurry or the forming or already formed, still unpressed sheet, particularly during straining.
52. Method according to one of the claims 41 to 51,
    characterised in that, in order to generate the plasma or the corona discharge, a direct current corona discharge is generated and the high voltage pulses (66, 67) are overlaid on the direct current corona discharge.
53. Method according to one of the claims 41 to 52,
    characterised in that a pulse repetition rate (63) of between 10 Hz and 5 kHz, in particular between 10 Hz and 10 kHz is used.
54. Method according to one of the claims 41 to 53,
    characterised in that the power coupling of electrical energy into the plasma is controlled primarily by means of the regulation of amplitude (U), pulse duration (62) and pulse repetition rate (63) of the overlaid high voltage pulses.
55. Method according to one of the claims 28 to 54,
    characterised in that high voltage pulses (66, 67) with a duration (62) of less than 3 µs, preferably less than 1 µs, more preferably less than 500 ns are used.
56. Method according to one of the claims 28 to 55,
    characterised in that a homogeneous, large-volume plasma with a high power density is generated without plasma pinching or breakdown occurring.
57. Method according to one of the claims 28 to 56,
    characterised in that a DC voltage of a sufficient level is used such that a stable DC corona discharge is formed in the plasma only in conjunction with overlaid high voltage pulses.
58. Method according to claim 57,
    characterised in that that the DC voltage used lies below the voltage for a stable operation without the overlaying of high voltage pulses.
59. Method according to claim 57 or 58,
    characterised in that the total amplitude used (DC voltage + pulse amplitude) lies above the static breakdown voltage of the electrode arrangement.
60. Method according to one of the claims 57 to 59,
    characterised in that the total amplitude used corresponds to between two times and five times the static breakdown voltage of the electrode arrangement.
61. Method according to one of the claims 57 to 60,
    characterised in that the amplitude (U) of the high voltage pulses lies in the range between 10% and 1000% of the DC voltage used.
62. Method according to one of the claims 28 to 61,
    characterised in that a gas stream is generated perpendicularly to the electrode arrangement (43, 44).
63. Method according to one of the claims 28 to 62,
    characterised in that a gas stream is generated parallel to the electrode arrangement (43, 44).
64. Method according to one of the claims 24 to 63,
    characterised in that impurities formed by means of organic dyes, biocatalytic substances and/or microorganisms and/or other biological material formed in the suspension are reduced.
65. Method according to one of the claims 24 to 64,
    characterised in that adhesive impurities are reduced.
66. Method according to claim 24,
    characterised in that the dilution water (26) is also treated with the plasma or the gas discharge before the dilution water (26) is added to the suspension.

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