Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/001—Modification of pulp properties
  • D21C9/007—Modification of pulp properties by mechanical or physical means
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
  • D21H25/04—Physical treatment, e.g. heating, irradiating

Definitions

• the invention relates to a process for the treatment of a process material in the production of paper, cardboard or paperboard, wherein a, preferably non-thermal, large-area plasma or a gas discharge, in particular a corona discharge is applied under at least atmospheric pressure and in the plasma generation and / or during the gas discharge, the resulting radicals act on the process material.
• bleaching chemicals are used to a high degree. Typical bleaching chemicals are chlorine, chlorine dioxide, sulfurous acids, Ex ⁇ traction with sodium hydroxide, oxygen, hydrogen peroxide and ozone. Depending on the method used, alkaline or acidic ambient conditions are required. Modern bleaching processes often make use of various bleaching stages in which various bleaching chemicals are used, each bleaching stage typically consisting of a mixing unit and a subsequent reaction tower. In these processes, some of the highly toxic (chlorine dioxide) or highly corrosive acids, bases or reagents have to be transported in large quantities, stored, and after completion of the process also reprocessed or disposed of.
• highly toxic (chlorine dioxide) or highly corrosive acids, bases or reagents have to be transported in large quantities, stored, and after completion of the process also reprocessed or disposed of.
• the object is achieved by using radicals of different types or compositions for at least two different types of process goods or at at least two different process stages.
• radicals of different types or compositions for at least two different types of process goods or at at least two different process stages.
• Process material at different points in the process can advantageously be reduced in papermaking the addition of solid and / or liquid chemicals.
• process goods are selected from the following starting materials and / or intermediates:
• the process goods mentioned above occur, for example as starting materials and / or intermediates, at different Pro ⁇ zessrasen to within the paper making process.
• the radicals generated are ozone, hydrogen peroxide, hydroxyl radicals, HO 2 and / or HO 2.
• Radicals are preferentially generated in gas discharges by the collision of energetic electrons with molecules, which dissociate or excite them radicals are released immediately, while stirring in the presence UV light it is evidence ⁇ by subsequent radiative transitions, which in turn reacts with cool air and / or Wassermole ⁇ and dissociates them.
• the plasma or gas discharge is applied in such a way that as radicals increasingly ozone and / or water are formed ⁇ peroxide.
• the plasma or the gas discharge is applied in such a way during screening and / or surface distributed process material or in that formed as Ra ⁇ cals increasingly OH, HO 2 and / or HO 2 " becomes.
• a generation rate of the radicals and / or the composition of the generated radicals is controlled and / or regulated by influencing an amplitude, a pulse duration and / or a pulse repetition rate of high-voltage pulses. Since the generation rate of the radicals generated by an electrical process and thus very well controlled in real time, such a method is very economical ⁇ Lich and can be readjusted within a very short time for different treatment outcomes, for example by a learning algorithm.
• Another preferred embodiment of the invention is that for controlling and / or regulating the rate of production and / or the type of radicals generated a concentration of the generated radicals is measured.
• the concentration or the property "online” is measured.
• the quality characteristics descriptive reading quasi evaluated simultaneously and can play as reacts at ⁇ by influencing the production rate at him.
• for regulating the amplitude of the high voltage pulses can in konstan ⁇ ter repetition rate and / or the repetition rate of the high tensioning ⁇ voltage pulses are varied at a constant amplitude.
• a further increase in the treatment result is achieved by enriching the process material with oxygen in the plasma-exposed area.
• the plasma or the gas discharge between the electrodes are generated high voltage pulses with a duration of less than 10 microseconds he ⁇ for generating.
• 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 pulse pulses or of high-voltage single pulses with a duration of more than 10 ⁇ s, is far less efficient.
• RF radio frequency
• high-voltage pulses are applied with a duration of less than 3 microseconds, preferably less than 1 s, before ⁇ preferably of less than 500 ns.
• a high-voltage pulse duration of less than 100 ns is used.
• a high-voltage pulse duration of 100 ns to 1 ⁇ s is used in flatly distributed process material or in a sheet which is still forming, or which is still undpressed, in particular during sieving.
• Process material or in forming or formed, still non-pressed sheet, in particular during screening, surrounded by the plasma be ⁇ impacted area of an enriched with water vapor atmosphere.
• an amplitude ent ⁇ speaking at least twice the value, preferably at least three times the value of a corona threshold voltage, to the electrodes are applied.
• a DC corona discharge is generated to generate the plasma or the corona discharge and the DC voltage corona discharge, the high voltage pulses are superimposed.
• the superimposition of the high-voltage pulses with a DC voltage has the particular advantage that the high-energy high-voltage pulses can already start from a very high energy level.
• a pulse repetition rate between 10 Hz and 5 kHz, in particular from the range of 10 Hz to 10 kHz, is used.
• the power input electrical energy is controlled in the plasma primarily via the regulation of amplitude, pulse duration and pulse repetition rate of the superimposed high-voltage pulses ⁇ th.
• the DC voltage used lies below the clamping ⁇ voltage for stable operation without high voltage pulse superimposition ⁇ .
• the total used ⁇ amplitude (DC voltage + pulse amplitude) lies above the static breakdown voltage of the electrode assembly. It is expedient if the total amplitude used corresponds to two to five times the static breakdown voltage of the electrode arrangement.
• the voltage is chosen so that the amplitude of high voltage pulses is between 10% and 1000% of the translated ⁇ is DC voltage.
• the plasma is generated at a distance of less than 20 cm, preferably less than 10 cm, preferably less than 5 cm from the process material.
• FIG 1 shows a schematic representation of a Toiletherstel ⁇ treatment plant with a screening device, a pressing device and a finishing and / or drying plant
• FIG 2 is a bleaching apparatus
• FIG. 3 shows a representation (section) of an arrangement for generating radicals in corona plasmas in pulp or air: parallel plate or tube arrangement with wire, which is superimposed on a pulsed high voltage
• FIG. 4 shows a schematic representation of pulses for generating radicals in corona discharges in air or aqueous Media using short (typically ⁇ 1 ⁇ s) high voltage pulses with high pulse repetition rate
• FIG 5 to FIG 10 electrode assemblies and electrode systems for generating corona discharges plate-plate, plate-wire plate, coaxial wire tube, tip plate, multi-tip plate, grid plate (tube), grid lattice arrangements
• FIG 11 is a hybrid discharge, wherein one electrode is completely above the medium on the sieve befin ⁇ det, whereas the second electrode through the screen itself is formed
• 12 is a plate or grid assemblies with curved surfaces to conform to vessel walls or using the same
• 13 shows a pulsed discharge in the near-surface gas space above the headbox on the sieve with a multi-wire plate arrangement
• FIG. 14 shows a pulsed corona discharge system with a coaxial one
• Wire tube with baffled, very finely divided gas bubbles, so that the finest particles of gas are present in the discharge area and streamer formation takes place predominantly in the gas bubbles.
• the papermaking plant 1 shows a schematic representation of a complex paper-making plant 1, as it is 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. Per minute, the paper ⁇ produces manufacturing facility up to 1400 m of paper 27. It takes only we ⁇ nige seconds from the first impact of the suspension or of the pulp 39 on the sieving device 9 to the finished paper 27, which is ultimately wound up in a reel 15 °. In the ratio 1: 100 diluted with water, the Fa ⁇ hydro- 30 (see FIG 2) is applied together with excipients on the screening device 9 with the wire 10 degrees.
• the white water 23 can flow from ⁇ or are sucked by a plurality of Saughunt Schemee 24th In this way, a uniform fiber composite is created, which is activated by mechanical pressure in a press device 11 and with the aid of steam heat. dehydrated.
• the entire papermaking process is essentially subdivided into the areas of substance preparation , paper machine, finishing and equipment.
• Waste paper and, as a rule, also pulp reach a paper mill in dry form, while 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 likewise dissolved with the addition of water in a fiber trough 35 (FIG. 2).
• Non-paper components are ⁇ the discharged via different sorting aggregates (not shown here).
• the mixture of different raw materials 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 sieve ⁇ width.
• the paper web 27 still contains about 80% water.
• Another dewatering process is carried out by mechanical pressure in the press device 11.
• 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.
• To the press apparatus 11 joins ei ⁇ ne drying plant. 13
• the remaining residual water is evaporated in the drying plant 13.
• 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 fed into a heat recovery system, not shown ⁇ .
• a first electrode 43 below the sieve device 9 and a second electrode 44 above the sieve device 9 are arranged according to the inventive method between the headbox 7 and the beginning of the screening 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 can be produced under atmospheric pressure in the immediate vicinity of the fiber suspension 39 in order to treat 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 a high power density is produced between the electrodes 43 and 44.
• a plasma density is homogeneously distributed over the treatment area, which is covered by the electrodes 43 and 44.
• this large-volume plasma with high power density characterized ⁇ he witnesses that a DC corona discharge intense short-last over ernde high voltage pulses with a high Impulswiederholra ⁇ te be superimposed of typically 1 kHz.
• a very homogeneous, large-volume plasma with a high power density is produced without the plasma constrictions that are known in DC corona discharges.
• Hydroxyl radicals are particularly aggressive and oxidizing, is characterized in which only a few Se ⁇ customer in the treatment area between the electrodes 43 and 44 lingering fiber suspension obtained a bleaching effect.
• an electrode system 47, 48 in the press device 11 generates a large-area plasma for treating the paper web 27 as a second type of process material.
• the first electrode 47 in the direction Pressenvor- 11 is provided as a semi-circular grid electrode ⁇ out. 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 designed as a plate electrode and arranged in such a way that the transport roller 12 can be guided between the electrodes 47 and 48.
• the plasma treatment area can also be flowed via the gas distributor 81 with the gas line 80 with an oxygen-argon mixture here.
• the pressing process compresses the paper structure, a strength increases and a surface quality is decisively influenced.
• the molecular structure of the paper surface is further changed ⁇ changed.
• the strength of the paper 27 is increased and improved printability.
• 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.
• Aforesaid Anord ⁇ voltages of the electrode systems, where the paper web is sawn between the used for the streamer discharge electrodes 27, is particularly advantageous, since the paper 27 thereby partially acts as a dielectric barrier, thus the transition can delay or suppress the streamer breakdown ,
• a raw material 30, in particular pulp as a third type of process material on a conveyor belt 33 in a fiber ⁇ trough 35 is conveyed.
• the raw material 30 is mixed with water and pumped via a pipeline 36 into a bleaching trough 37.
• a first electrode 43 'and second electrode 44' are each designed as a circular planar Git ⁇ terelektrode.
• the first electrode 43 ' is arranged in the gas space ⁇ of the filled into the bleaching trough 37 pulp fiber suspension 39.
• the second electrode 44 ' is in ⁇ Neren the bleaching tray 37 is arranged and is thus completeness, ⁇ dig 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.
• the radicals OH “ , HOO " , O, O 3 are preferably produced in the suspension 39. These radicals trigger a bleaching chemical reaction.
• the high-voltage pulse tension ⁇ generator 46 is operated so that it produces high voltage pulses with a duration of typically 1 s between the electrodes 43 'and 44'.
• a voltage necessary for the generation of radicals and ozone in the pulp fiber suspension is about 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.
• oxygen-argon can be fed into the bleaching trough 37 via a gas line 80.
• Mixture, which was treated in a gas distributor 81, are introduced.
• FIG. 3 shows a sectional view of a bleaching vessel, which is alternative to FIG. 2.
• a bleaching vessel In the middle of the bleaching vessel ei ⁇ ne high voltage electrode 50 is arranged.
• the outer jacket of the bleaching vessel is prepared as a counterelectrode 51.
• a pulp fiber suspension 39 In the bleaching vessel is a pulp fiber suspension 39.
• a streamer 53 is shown between the electrodes 50 and 51. Radicals are generated in streamers by high-energy electrons colliding with and dissociating or exciting molecules. Upon dissociation, radicals 59 are immediately released, while upon excitation by a subsequent radiant transition, UV light is generated. This generated UV light reacts as ⁇ derum with water molecules and dissociated this.
• a first pulse 66 and a second pulse 67 each having a pulse width 62, have a distance 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 some 10 kV of the DC voltage coincides with the abscissa shown.
• the illustrated pulse voltage is thus superimposed on the DC voltage.
• the pulses 66 and 67 have a pulse width of less than 1 62 microseconds, the individual pulses 66, 67 a strongly rising edge with a rise time on ⁇ 64 and HA ben a less steep flank.
• the pulse repetition time 63 is typically Zvi ⁇ rule 10 microseconds and 100 milliseconds.
• the individual pulses 66, 67 such total ⁇ amplitude that more than the predetermined DC voltage, a predetermined energy density is achieved.
• the pulse rise time 64 is short in comparison to the pulse ⁇ fall time.
• Such a kind of impulse ensures that electrical breakdowns which are too spatial and temporal disturbances in the homogeneous distribution of the plasma density would be avoided.
• FIGS. 5 to 10 show examples of further electrode systems for generating corona discharges in preferably aqueous media.
• FIG. 5 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 in ⁇ pulse generator 46.
• the second plate 70b forms the counter electrode and, as a grounded electrode, is connected to the high-voltage pulse generator 46.
• FIG. 70 A corresponding arrangement with specially flat plate ⁇ electrodes is shown in FIG. Again there are two solid plate electrodes 70a and 70c at a fixed distance with a high voltage electrode 71 in the middle.
• the high voltage electrode 71 is made of 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 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. 6
• 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.
• FIG. 8 shows a tip-plate arrangement as Elektrodensys ⁇ tem.
• three tips 73 are connected to the high voltage pulse generator 46 via a high voltage line.
• the tips 73 are at right angles to a ground th plate electrode 74 is arranged.
• the distance of the tip electrodes ⁇ 73 to the plate electrode 74 is adjustable and can thus be adapted for different process conditions.
• FIG. 9 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 arranged centrally between two solid plates 70d and 70e.
• 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.
• FIG. 10 shows an electrode system as a grid-grid Anord ⁇ tion.
• a first grid 75a and a second grid 75b are parallel to one another here.
• the first grid 75a 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.
• a hybrid discharge wherein one electrode is fully 75a ⁇ constantly outside a to be bleached pulp 39, and a second electrode 76b fully or partially in the pulp 39 is submerged, is produced with the arrangement in Fig. 11
• the electrode 76a is configured as a grid electrode and forms the high voltage electrode, which is in communication with the high voltage pulse generator clamping ⁇ 46th
• the geothermal te counter-electrode 76 b is designed as a grid electrode and communicates with the high-voltage pulse generator 46 in connection.
• FIG. 12 shows a plan view of a bleaching tub with a vessel wall 77.
• 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 multi-wire electrode 79 is disposed as a concentric electrode, the shape of the vessel wall 77 sequentially and communicates with the high-voltage pulse genes ⁇ rator 46 in connection. It shall have two counter electrodes opposite: first, the vessel wall 77 and on the other a plate electrode 78.
• the high voltage electrode 79 is be- see the vessel wall 77 and the plate electrode 78 is located approximately ⁇ berüh free.
• the vessel wall 77 and the plate electrode ⁇ erode 78 are electrically conductively connected to each other and thus form the grounded counter-electrodes, which are connected to the high voltage pulse generator 46 in connection.
• 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.
• FIG. 14 shows a pulsed corona discharge system in an aqueous solution or pulp 39.
• the electrode system is designed analogously to FIG. 3 as a coaxial wire tube electrode system.
• the high voltage electrode 50 is arranged coaxially with the counter electrode 51 forming the vessel wall.
• the streamer mentioned in FIG. 3 preferably forms. Owing to the streamer discharges, oxidants 57 are formed. Thus, certain radicals are generated in the suspension.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Mechanical Engineering (AREA)
• Paper (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)

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• 2005
  • 2005-10-14 DE DE102005049231A patent/DE102005049231A1/de not_active Ceased
• 2006
  • 2006-06-08 WO PCT/EP2006/063011 patent/WO2006134064A1/fr not_active Application Discontinuation
  • 2006-06-08 EP EP06763585A patent/EP1893803B9/fr not_active Not-in-force
  • 2006-06-08 AT AT06763585T patent/ATE487823T1/de active
  • 2006-06-08 DE DE502006008282T patent/DE502006008282D1/de active Active

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