Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
  • B01J19/10—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing sonic or ultrasonic vibrations
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/0018—Devices for dispensing fibres in a fluid
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/02—Head boxes of Fourdrinier machines
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/02—Head boxes of Fourdrinier machines
  • D21F1/028—Details of the nozzle section

Definitions

• the ultrasonic energy is hereby added to the part of the process generally referred to as the short white water system, i.e. headbox or headboxes, the white water which is separated in the wire part and which is used for dilution of the stock to a desired stock consistency and to white water trays and tanks within this white water system.
• ultrasonic energy is added to wash systems for wires and felts in order to maintain them completely clean and to prevent the blocking of them, which leads to constant and high dewatering capacities for those parts of the papermaking process. In summary this means, improved paper quality, increased yield for paper constituents, reduced steam consumption and increased production capacity per production unit.
• ultrasonic energy to the white water system is done in order to prevent the forming of fibre flockulation in the paper, and to prevent microbiological growth, which leads to the forming of lumps of slime which in combination with lumps of fibres will cause breaks and machine stops for wash-ups and thereby loss of production time. It will in some cases, when a microbiological contamination has been found to come from a certain raw material which is added to the white water system be necessary to add ultrasonic energy also to that raw material in order to prevent the development of such a source of contamina ⁇ tion.
• Patent GB A 1 577 664 describes a method whereby one uses ultrasonic energy to remove a very troublesome type of resin from a pulp manufactured from specific wood species, a resin which caused big problems in the form of percipitations of resin of different paper machine parts.
• the patent thus addresses a completely different problem than those addressed in this patent, and the addition of ultrasonic energy is made far ahead of the paper machine.
• SU 896130 describes a method whereby ultrasonic energy is added to high consistency screens, used for the screening of pulp particularily to prevent the forming of fibre knots, i.e. far ahead of the paper machine.
• S ⁇ 887610 describes a method whereby ultrasonic energy has been used in the stock preparation in order to improve the coloring of the stock, which also is done far ahead of the paper machine.
• the patent describes a batch processing method, which has not been foreseen to be used in a continuous process.
• SU 746012 is also dealing with a batch process in the stock preparation, where ultrasonic energy has been used in order to be able to add a paraffin-wax dis ⁇ persion and copolymers in order to manufacture a paper with improved mechanical strength and with water repelling properties.
• Fig. 1 is a schematic, partly sectioned profile of a head box with an air cushion and equipped with ultrasonic transducers 1, suitable to utilize for this invention.
• Figs. 2-5 are schematic, partly sectioned profiles of different hydraulic head boxes equipped with ultrasonic transducers 1, suitable to utilize for this invention.
• Fig. 6 is a two layer hydraulic head box equipped with ultrasonic transducers 1, suitable to utilize for this invention.
• Fig. 7 is a head box where the perforated roll has been replaced by submersible units equipped with ultrasonic transducers 1, suitable to utilize for this invention.
• Figs. 8 and 9 are examples of washing systems for wires and felts, equipped with ultrasonic transducers 1, suitable for the utilization of this invention.
• the floes are built up by fibres and fillers but are initially made up by fibres. Higher pulp consistency, higher degree of refining and longer fibres will increase the flocculation, which in turn forces the paper manufacturers to work with very low consistencies during the production of e.g. sack paper.
• the size and form of the floes can easily be determined by observing the paper sheet by means of translucent light. The floes are then represented by the darker parts of the paper with lighter parts between them.
• the paper is thus built-up by darker parts with a higher weight per unit area and lighter parts with lower weight per unit area.
• the mechanical strength properties of the paper are increased by higher and decreased by lower weight per unit area. This means, that the strength properties of the paper are controlled by the lighter parts between the darker parts of the paper. Filler and fibre retention, particularily the retention of fines, is higher in the floes, whereas they in the lighter parts tend to follow the white water which is drained from the paper machine wet end, i.e. the wire and press sections.
• a reduction of the flocculation referred to as improvement of the formation by the paper maker, thus leads to either that one can manufacture a paper with improved strength properties with the same weight of fibres per unit area, or manufacture a paper with the same strength properties from less fibres per unit area.
• An improvement of the formation thus gives the possibility of better fibre yield and in turn to an improved raw material economy.
• the floes also contain more water and will reduce the dewatering on the wire as well as in the press section which in turn leads to an increased tendency of crushing in the press section which is caused by the fast water flow caused by that more water must be separated from the sheet will tear fibres away from it, and when the hydraulic pressure is large enough cause a break.
• the ultrasonic energy is in this case added to the stock in the head box either by gluing the ultraso ⁇ nic transducers which are mounted on aluminium bars onto the head box for air cushion and open head boxes preferably underneath the head box, and all around the head box for hydraulic head boxes (figs. 1-6) .
• the ultrasonic transducers are installed such that the ultrasonic energy is added to the stock within the entire length, width and height of the head box using several parallel combinations of transducers. In this way one assertains that sufficient amount of ultrasonic energy to solve the problem is added to the stock.
• the stock is pumped into the head box via a manifold and a diffusor bank.
• a very rapid reduction of flow velocity occurs which assertains that the floes are dispersed.
• the reforming of the floes occurs very rapidly and it is desirable that one assertains that the reforming of the floes is prevented.
• the present technology has not made it possible to arrive at these results in spite of the many different designs that have been tested and been in operation during decades.
• the dispersing effect of the ultrasonic energy is caused by the well known cavitation which is used for ultrasonic cleaning of different components, e.g. anilox rolls or gravured rolls for flexo- and rotogravure printing and where it is also possible to remove even dried waterbased ink from the gravured cells.
• cavitation which is used for ultrasonic cleaning of different components, e.g. anilox rolls or gravured rolls for flexo- and rotogravure printing and where it is also possible to remove even dried waterbased ink from the gravured cells.
• these small bubbles When these small bubbles are irradiated with ultrasound, they will continuously absorb energy from the compression and expansion cycles of the ultraso ⁇ nic sound waves and grow to their critical size which is dependent upon wave length after which they start to grow in size very rapidly and will finally implode which they do in less than a microsecond.
• the imploding bubbles will transmit energy to the nearby medium which in a fibre suspension means that they disperse existing floes as well as prevent new floes to occur and in addition increase the fibrillation. That the fibrillation occurs has been verified by measurements of freeness values, where the difference of freeness values before and after the addition of ultrasonic energy has been verified.
• the dispersing effect has also been documented in the Swedish patent application 9002006-6 (468754) where the dispersing effect of the ultrasonic energy has resulted in print quality improvements and to ink savings.
• ultrasonic energy will prevent the regeneration of floes and disperse already formed floes. If the ultrasonic energy is added over a range of wavelengths with wavelength sweeps over that range, it will since the length of one wave ⁇ length is directly dependent upon frequency, cause, that wavelengths of different frequencies are located on different distances from the transducer and is transmitted through the medium in multiples of these distances. In that way the ultraso ⁇ nic cavitation will be distributed in the entire fibre suspension and prevent regeneration or forming of floes. It will furthermore contribute to degassing and reduced foaming.
• retention aids which are polymers
• the ultrasonic energy disperses each component of these chemicals which increases the reactivity and improves the yield. They will in addition distribute them more evenly which leads to improved retention for the same amount of retention aid or the same retention with less retention aids.
• Fibre agglomerations on machine parts which after some time will come off and eventually cause breaks, are other areas wehre the dispersing effect of ultrasonic energy can be used. They are generally formed at locations where there are eddy currents e.g. around transducers, inspection doors, deckel boards and the like. An installation of ultrasonic transducers near these locations will prevent the forming of such fibre agglomorations.
• the lumen is completely filled with water and that the cell walls also absorb a large volume of water.
• the entire volume of cellulose suspension acts as a liquid and the ultraso ⁇ nic energy can, if sufficient ultrasonic energy is added, be distributed throughout the entire stock volume in the head box.
• Increased degree of refining, increased pulp consistency and increased speed of stock flow will increase the specific energy requirements.
• the utilisation of systems for installation in the paper machine wet end for inspection and measurements of formation and fibre weight, can be used for the optimisation and control of stock consitency, ultrasonic power and other production parameters, e.g. sufficient paper grammage to meet paper property specifica ⁇ tions.
• the specific utilisation of raw materials such as paper making pulp, chemicals and energy can be optimised in a way that until now has not been possible, and with revolutionary possibi ⁇ lities for improvements of quality and profitability.
• Microbiological growth in the stock and water circulations has traditionally been a big problem in the paper making process. Aerobic as well as anaerobic slime forming microorganisms form slime build-up onto machine components and walls of white water and stock tanks. The presence of anaerobic growth is explained by the fact, that the aerobic growth forms anaerobic conditions under itself due to the fact that the aerobic organisms will consume all available oxygen.
• the anaerobic growth of, among, aggregateula ⁇ rily sulphate reducing bacteria such as Desulfovibrio Desulfuric- nas, will increase metal corrosion, and will directly influence brightness, amongularily when reducing beaching with zinc or sodium hydrosuphite is used.
• microbiological growth causes slime build-up onto machine parts, which build-up, sooner or later will come off as lumps, which are very difficult to dissolve. They are e.g. passing through fan pumps or other pumps and through diffusor banks and perforated rolls and causes slime spots and production breaks.
• the lumps consists many times as well of fungi and bacteria as of organic and inorganic substances. The presence of eddy currents in water and stock systems will favour the growth and forming of fibre lumps, which will agravate the situation.
• Ultrasonic energy will solve this problem.
• An addition of ultrasonic energy to the part where microbiological growth occurs will effectively prevent agglomerations there.
• the ultrasonic energy can be added externally as is done onto the head box for components and tanks made of metal, juxtaposularily stainless steel.
• tanks made of concrete, tiled or plastic coated it will have to be added by means of submersible units, in which case the distance to the wall and the energy level will have to be matched so that the cavitation is powerful enough to solve the problem, but not so powerful that it will peel of the tile or coating.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

Country Status (8)

Cited By (9)

Families Citing this family (19)

Citations (4)

• 1994
  • 1994-04-14 SE SE9401272A patent/SE9401272L/sv not_active Application Discontinuation
• 1995
  • 1995-04-12 AU AU23778/95A patent/AU2377895A/en not_active Abandoned
  • 1995-04-12 WO PCT/SE1995/000398 patent/WO1995028521A1/en not_active Application Discontinuation
  • 1995-04-12 CA CA 2187734 patent/CA2187734A1/en not_active Abandoned
  • 1995-04-12 CN CN 95193438 patent/CN1149898A/zh active Pending
  • 1995-04-12 JP JP7526899A patent/JPH09512063A/ja active Pending
  • 1995-04-12 EP EP95916891A patent/EP0755469A1/en not_active Withdrawn
• 1996
  • 1996-10-11 FI FI964078A patent/FI964078A0/sv not_active Application Discontinuation

Patent Citations (4)

Non-Patent Citations (4)

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