EP4286582A1 - Yankee-zylinder für die papierherstellung - Google Patents

Yankee-zylinder für die papierherstellung Download PDF

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Publication number
EP4286582A1
EP4286582A1 EP23020259.0A EP23020259A EP4286582A1 EP 4286582 A1 EP4286582 A1 EP 4286582A1 EP 23020259 A EP23020259 A EP 23020259A EP 4286582 A1 EP4286582 A1 EP 4286582A1
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EP
European Patent Office
Prior art keywords
yankee
mantle
inductors
electromagnetic induction
axis
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23020259.0A
Other languages
English (en)
French (fr)
Inventor
Luca Ghelli
Francesco Simoncini
Gaetano PASSANISI
Iacopo BIBBIANI
Marco VOLPI
Giulia MASIA
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toscotec SpA
Original Assignee
Toscotec SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toscotec SpA filed Critical Toscotec SpA
Publication of EP4286582A1 publication Critical patent/EP4286582A1/de
Pending legal-status Critical Current

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00—Dryer section of machines for making continuous webs of paper
    • D21F5/02—Drying on cylinders
    • D21F5/022—Heating the cylinders
    • D21F5/024—Heating the cylinders using electrical means
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00—Dryer section of machines for making continuous webs of paper
    • D21F5/18—Drying webs by hot air
    • D21F5/181—Drying webs by hot air on Yankee cylinder

Definitions

  • the present invention relates to a Yankee drier for the production of paper.
  • tissue paper is produced using a fibrous suspension containing cellulose fibers normally called pulp.
  • pulp is introduced on draining web-like supports.
  • the formation of the sheet takes place, that is, the fibers overlap and create bonds to form what, once the water has been removed, will be the sheet.
  • the removal of water takes place progressively through actions of drainage, suction, pressing and evaporation until obtaining rolls of paper with a residual humidity of around 5%.
  • the water present in the fibrous suspension is drained through a forming cloth, after which the formed sheet passes through a pressing section in which other water is eliminated and, subsequently, passes over a cylinder, commonly called “Yankee", heated from the inside by introducing high pressure steam.
  • a cylinder commonly called "Yankee”
  • the combined action of the heat transmitted to the sheet through the external surface of the Yankee and of the blowing of hot air and the suction operated by hoods arranged around the Yankee itself finally determines the achievement of the desired degree of dryness.
  • the sheet of paper can be detached from the Yankee by means of a creping blade and wound up in the form of a reel. In alternative systems, the detachment of the sheet from the Yankee can take place in different known ways.
  • the term "tissue” generally refers to low-weight paper products intended for hygienic and sanitary use, such as toilet paper, rolls of kitchen paper or towels, handkerchiefs, napkins, etc.
  • the present invention relates to a Yankee drier whose surface in contact with the sheet of paper is heated avoiding the use of steam.
  • the present invention provides for the construction of a Yankee drier with an electromagnetic induction system inside it and a mantle made of any electrically conductive material, such as for example carbon steel or cast iron, suitable to exploit the thermal effects connected to the electromagnetic induction. At the two ends of the mantle there are two respective end heads.
  • the Yankee mantle can also be stratified, with a primary layer, in correspondence with the radially inner surface of the cylindrical mantle, on which the electromagnetic field acts, made of electrically conductive material.
  • the mantle layers adjacent to the primary layer heat up by conduction by being in contact with the material of the primary layer.
  • the induction system placed inside the Yankee is static, i.e. it does not rotate together with the Yankee, and is supported by an axis passing through two pins formed on the end heads of the Yankee.
  • the internal surface of the Yankee i.e. the internal surface of the mantle, is free from circumferential grooves. These grooves are normally present in Yankees heated by steam and perform the dual function of increasing the convective exchange surface with the internal steam (which according to the present invention is not used) and to collect the condensed steam (which according to the present invention is not formed as a result of the steam not being used).
  • the electromagnetic induction system comprises a single inductor or more inductors, at a radial distance preferably between 30 cm and 1 mm from the inner surface of the mantle without contact with the latter. More preferably, said radial distance is between 5cm and 2mm and, still more preferably, between 2cm and 5mm.
  • the term radial distance means the radial distance between the internal electrically conductive cylindrical surface of the Yankee and the point of the induction system closest to it.
  • the inductors can be made in many ways.
  • the inductors are configured to heat the metallic inner surface of the mantle.
  • the heating is obtained by generating alternating electromagnetic fields through the inductors, with variable frequency and amplitude according to the power to be transmitted.
  • the electromagnetic fields which vary over time, generate induced currents in the metallic material of the mantle which, due to the Joule effect, produce localized overheating. In this way, the heat required for drying the paper is generated.
  • the heat produced at the internal surface of the Yankee diffuses by conduction through the thickness of the mantle, until it reaches the external surface with which the sheet being dried is in contact. A part of the heat will diffuse inside the cylinder itself both by radiation and by convection. However, since the internal volume of the Yankee is substantially closed, the heat diffused inside will not be dispersed but will cause a rise in the temperature of the air contained inside it. In this way, the corresponding portion of thermal energy will not be dispersed into the external environment, with the exception of the part transmitted to the outside through the end heads.
  • the heads can be suitably insulated with per se known systems so as to limit to a minimum the part of thermal energy transferred to the external environment, such that the maximum portion of thermal energy is transferred to the sheet being dried.
  • the electrical power to be transformed into thermal power for drying the sheet is of the same order of magnitude as the thermal power provided by the steam in traditional systems.
  • the thermal power does not depend on the source, but on the use that must be made of it.
  • the function of the Yankee is to provide heat to the paper in order to bring the dryness degree of the sheet adhered to it from a minimum value (normally in the range of 25%-50%) when the paper comes into contact with the external surface of the mantle, up to a maximum value (typically in the range of 55%-99%) when the paper is detached from the Yankee.
  • the thermal energy required for the correct functioning of the Yankee will therefore depend on the programmed production parameters and, for example, on: paper weight, sheet width, input dryness degree and output dryness degree from the Yankee, Yankee rotation speed and input sheet temperature. These parameters make it possible to calculate the exact amount and enthalpy content of the water that must be removed from the sheet. Overall, the power required to evaporate the water contained in the sheet until the desired degree of dryness is reached varies approximately between 2MW and 15MW, depending on the production rate, the inlet temperature of the sheet on the Yankee and various other parameters (grammage, degree of creping, etc.).
  • the Yankee may have an external cylindrical surface with an external layer that is harder than the base metal in order to increase its resistance to wear (due to the presence of paper and scrapers used for remove and/or crepe the dried sheet and/or clean the surface upstream of the sheet adhesion area).
  • said outer layer can be made by means of a metal deposition, or by a plating deposition (deposited by fusion) or by a surface treatment, for example by laser hardening.
  • Decarbonisation in traditional Yankee dryers, steam is normally produced in boilers that burn fossil fuels. Steam generation represents a large amount of the energy used to operate a paper mill. Increasingly, national and international regulations, in addition to the need to reduce the impact of the greenhouse effect on the climate, require that the production of carbon dioxide, one of the main greenhouse gases, be limited and possibly cancelled.
  • the electrification of the heat production to be used in the Yankee for drying paper in accordance with the present invention can allow to reduce (up to canceling) the production of CO 2 necessary for the operation of the Yankee since the required electrical energy can be produced using renewable sources and not the use of fossil fuels. Assuming that only electricity generated from renewable sources is used, it is possible to estimate a potential reduction of CO 2 emissions between 2500tons/year and 25000tons/year, depending on the productivity of the machine.
  • the condensate extraction system involves the use of large collection spoons rotating together with the Yankee: in this case, given the lower rotation speed of these systems, the condensate tends to accumulate on the lower part of the cylinder.
  • the spoons in number depending on the diameter of the cylinder) when they rotate, pass from the lower part, collect the condensate and guide it towards a central collector by exploiting the gravity and the particular path of the condensate removal ducts.
  • induction heaters makes it possible to eliminate the use of steam and all the components, systems and technical problems associated with the use of steam.
  • pressurized steam up to 10 bar
  • the need to use pressurized steam (up to 10 bar) inside traditional Yankee dryers also leads to a series of construction complications.
  • the resulting forces on the internal surfaces of the Yankee are significant (a circular head with an internal diameter of 6.6m, exposed to steam under pressure at 10bar, bears a resulting thrust equal to about 14000tons).
  • the use of pressurized steam means that the Yankee must be designed in compliance with the stringent rules imposed by national and international regulations for pressure vessels in order to avoid catastrophic accidents, such as an explosion of the Yankee.
  • the structure itself and the connection systems of the various structural components require care and very high levels of control in order to absolutely guarantee the structural reliability of the cylinder throughout its operating life, with a great increase in costs both for the materials used and for the necessary construction and control procedures, the latter to be repeated periodically during the life of the product.
  • the surface of the Yankee before coming into contact with the paper to be adhered, is sprinkled with substances whose function is to promote adhesion of the paper, to facilitate its detachment after drying, to give particular characteristics to the adhered paper and to protect the outer cylindrical surface of the Yankee.
  • This is normally referred to as an organic coating and its chemical composition can vary greatly depending on the product, the condition of the Yankee surface and the recipe used by the paper mill.
  • Some of the chemical substances contained in the coating (for example epichlorohydrin polyaminoamide resins which can be used in the adhesion components) require, in order to function correctly, to create cross-linking bonds which are facilitated by high temperatures.
  • This aspect also has an impact on the sizing of the Yankee and of the machine configuration; in fact, having to guarantee the cross-linking of the coating before contact with the paper, this causes the coating spray bar (or more simply, the coating bar) to be placed at a certain distance from the point of contact with the paper (depending on the type of coating and the rotation speed of the Yankee).
  • the surface between the coating bar and the point of contact with the paper develops along an arc which, in fact, is unused: the purpose of the Yankee is to transfer thermal power to the paper to dry and this can only take place in the zone where the paper adheres to the Yankee; if a part of the Yankee cannot accommodate the paper because the coating distributed on it is not "ready" to ensure correct adhesion, then the Yankee, in condition of same performance, must have a larger diameter to compensate for the unused area (the development of the wrapping of the paper around the Yankee and, therefore, the diameter of the Yankee, depend on the overall performance of the machine and of the Yankee, as well as on the grammage).
  • the use of an induction system placed inside the Yankee and not rotating together with it allows, by adopting a modular design, to adjust the intensity of thermal power also according to the involved sectors. In this way it is possible to control the temperature of the sector dedicated to the cross-linking of the coating. By optimizing the crosslinking process, it is possible to reduce the space dedicated to it. Reducing the space required for crosslinking allows a reduction of the Yankee diameter in conditions of same performance.
  • the current system provides for the generation of thermal power outside the Yankee (the steam is produced in a boiler outside the Yankee and, from this, via ducts and regulation components, is brought inside the Yankee).
  • the system object of the present invention instead provides that the thermal power is produced, thanks to the Joule effect caused by the induced currents, directly in the metal coat of the Yankee, i.e. in correspondence with the exchange zone with the paper being dried. This allows to reduce all the losses due to the transport of fluid at high temperature from a remote area inside the Yankee.
  • This fact if associated with a source of electricity production from renewable sources (i.e. without the need to produce a heat transfer fluid for the production of electricity via combustion), allows the path of the thermal power to be significantly shortened, thus improving the overall efficiency.
  • a Yankee drier (1) is a body comprising a metal mantle (2) with a circular cross section and two end heads (3) on which two respective coaxial pins (4) are formed or mounted, arranged along an axis of rotation (x-x) of the Yankee.
  • a transmission (5) acts on the pins (4) by which the rotation speed of the Yankee around the axis (x-x) is controlled.
  • the outer surface of the mantle (2) forms a heat exchange surface with a sheet of paper produced upstream of the Yankee to reduce its water content, i.e. increase its dryness.
  • the sheet of paper can be produced, with methods per se known to those skilled in the art, in a machine for the production of structured paper which, for example, comprises a forming zone (A) in which the sheet is formed starting from a fibrous suspension of predefined composition, a pre-drying zone (B) of the sheet downstream of the formation zone (A), along which the water content of the sheet is progressively reduced, and a drying zone (C) downstream of the pre-drying area (B), where the Yankee (1) is installed.
  • a forming zone (A) in which the sheet is formed starting from a fibrous suspension of predefined composition a pre-drying zone (B) of the sheet downstream of the formation zone (A), along which the water content of the sheet is progressively reduced, and a drying zone (C) downstream of the pre-drying area (B), where the Yankee (1) is installed.
  • a section (D) can be arranged for collecting the sheet in the form of reels (R1, R2).
  • the presser (6) which compresses the sheet of paper on the Yankee (1) with a pre-set pressure.
  • the presser (6) can consist of a shoe press, a blind-holes roller or a suction roller.
  • the section (B) can eventually integrate systems for reducing the water content of the sheet based on multiple concepts (application of vacuum using suction boxes or suction rollers in order to facilitate water drainage, pressing areas, devices for supplying thermal energy, devices based on the removal of water from the sheet through the principle of capillarity, forced blowing of hot air through the sheet, etc). All these systems, even in combination with each other, are known per se.
  • a hood (7) can be arranged on the Yankee (1).
  • the sheet In the drying section (C) the sheet is in contact with the outer surface of the mantle of the Yankee (1) from the entry point (P1) to the exit point (P2) for a section with an angular extension (a) greater than 180°.
  • the sheet In the scheme of Fig.2 , the sheet is indicated by the reference "S".
  • a creping scraper (8) can be arranged for detaching the sheet from the Yankee (1) and, downstream of the creping scraper (8) with respect to the direction of rotation (1C) of the Yankee, there is a cleaner scraper (80).
  • the sheet in alternative configurations, could be detached from the Yankee even without the use of a scraper, but through the use of support belts which collect the sheet at the end of its passage from the Yankee surface.
  • the sheet (F) is conveyed by a web (9) from the forming area (A) to the drying area (C) and is associated with the web (4) in the compression nip defined by the presser (6) in cooperation with the Yankee (1).
  • the presser (6) is a shoe press and web belt (9) is a felt.
  • the same diagram shows a suction roller (SR) onto which the web (9) is guided upstream of the presser (6).
  • the presser (6) is associated with a further presser (60), arranged downstream with respect to the direction of rotation (1C) of the Yankee.
  • the web (9) is associated with the sheet in both the nips defined by the presser (6) and by the further presser (60) in cooperation with the Yankee (1).
  • the additional presser (60) consists of a blind-holes press.
  • the linear pressure exerted by the presser (6) in correspondence of the Yankee is preferably between 60 and 200 kN/m, more preferably between 90 and 150 kN/m and, even more preferably, between 90 and 120 kN/m.
  • the linear pressure exerted by the additional presser (60) at the Yankee is preferably between 90 and 120 kN/m.
  • the Yankee (1) has an external diameter comprised between 2.00 m and 7.500 m, and an axial length comprised between 3.00 m and 7.400 m.
  • a fixed electromagnetic induction heating system made up of one or more inductors (H; HN) positioned and configured to produce alternating electromagnetic fields with pre-established frequency and amplitude according to the thermal power to be generated.
  • H; HN inductors
  • the electromagnetic fields produced by the inductors which vary over time, induce the generation of electric currents in the metallic material of the Yankee mantle and, due to the Joule effect, the mantle itself is subject to heating.
  • the heat thus generated is used to dry the sheet (F).
  • the induction heating system makes it possible to generate a uniform thermal imprint on the surface of the mantle (2) of the Yankee, i.e. a uniform heat distribution along the generatrix lines of the cylindrical surface which defines the mantle.
  • the electromagnetic induction heating system extends axially, i.e. parallel to the axis (x-x) of the Yankee, along the inner surface of the mantle (2) but is preferably shorter than the latter, leaving a free space (10) in front of each of the end heads (3).
  • the radially outer side of the electromagnetic induction system is at a radial distance from the inner surface of the mantle (2) comprised between 20cm and 1mm, more preferably said radial distance is comprised between 5cm and 2mm and, even more preferably, between 2cm and 5mm.
  • the inductor (H) extends axially inside the Yankee (1) for a length (LH) shorter than the length (L2) of the mantle (2).
  • the terminals (HT) of the inductor (H) can be passed through one of the pins (4).
  • a single toroidal inductor (H) developed parallel to the axis (x-x) of the Yankee.
  • the toroidal inductor is formed by coils parallel to the inner surface of the cladding (2).
  • the radially outer side of the inductor (H) is at a radial distance from the inner surface of the shell (2) between 20cm and 1mm, more preferably said radial distance is between 5cm and 2mm and, even more preferably, between 2cm and 5mm.
  • the terminals (HT) of the inductor (H) can be passed through one of the pins (4).
  • inductors (HN) each of which consists of a solenoid developed around the axis of the Yankee and formed by coil turns concentric to said axis.
  • the inductors (HN) are arranged axially side by side.
  • the terminals (HT) of the inductors (HN) can be passed through one of the pins (4).
  • inductors (HN) are provided, each of which is formed by a solenoid consisting of coil turns wound around respective radial axes (RHN).
  • the inductors (HN) in this case are arranged circumferentially around the axis of the Yankee. Also in this case, the terminals (HT) of the inductors (HN) can be passed through one of the pins (4).
  • the reference “HP” indicates cores of ferromagnetic material which can optionally be used to realize the inductors (HN).
  • S > P - d where "S” is the radial distance of the inductor from the internal surface of the Yankee mantle, “d” is the diameter of the conductors forming the coil turns (HS) and “P” is the pitch between the coil turns of the inductor (or the individual inductors).
  • a geometric configuration of the inductor system (understood as a single solenoid or as a plurality of solenoids) is achieved in which the distance between the spiral windings of the inductor system and the internal surfaces of the armature consisting of the Yankee mantle is higher than the pitch between the coil turns (HS) reduced by said diameter (d).
  • the magnetic fields of the individual turns intercepted the mantle material is not influenced by possible non-uniformity of the pitch of the coil turns and/or the diameter of the conductors forming the coil turns and/or possible non-uniformity of the material of which are made the single coil turns.
  • Figs, 5A and 5B schematically show two possible dispositions of the coil turns (HS) formed by conductors having a different diameter (d).
  • the inductor (H) has a side (HM) radially closer to the mantle (2) and a side (HW) radially more distant from the mantle (2), and said side (HM) radially closest to the mantle (2) is at a given radial distance from the inner surface of the mantle (2) and also in this case the inductors are formed by turns (HS) made up of conductors of predefined diameter spaced apart of a pitch of predefined value (P).
  • HS turns
  • P pitch of predefined value
  • a Yankee cylinder for the production of paper is a body comprising a metal mantle (2) with circular cross-section and two end heads (3) on which are formed or mounted two respective coaxial pins (4) arranged along a rotation axis (x-x) of the Yankee, said body being configured to rotate with a predetermined angular speed around said rotation axis (x-x), wherein inside said body is arranged a fixed electromagnetic induction heating system comprising one or more inductors (H; HN) interacting electromagnetically with the mantle (2) to produce induced electric currents in the same mantle, said one or more inductors (H; HN) being arranged in proximity of the radially innermost surface of the mantle (2).
  • H; HN inductors
  • a Yankee cylinder according to the present invention may also have one or more of the following features possibly combined between them:

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  • Paper (AREA)
EP23020259.0A 2022-06-03 2023-05-29 Yankee-zylinder für die papierherstellung Pending EP4286582A1 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT202200011747 2022-06-03

Publications (1)

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EP4286582A1 true EP4286582A1 (de) 2023-12-06

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2273423A (en) 1939-06-23 1942-02-17 Budd Industion Heating Inc Electrically heated roll
GB949484A (en) 1960-06-25 1964-02-12 Escher Wyss Gmbh Improvements in or relating to rotatable heating cylinders for paper webs or the like
EP0067786A2 (de) 1981-06-16 1982-12-22 Beloit Corporation Vorrichtung zur Erhitzung der zylindrischen Wand eines Drehzylinders in einer Papiermaschine
EP0277905A2 (de) * 1987-02-03 1988-08-10 Beloit Corporation Heizmethode zum Heizen einer Kalanderrolle
DE20217966U1 (de) * 2002-11-20 2004-04-01 Eduard Küsters, Maschinenfabrik, GmbH & Co. KG Induktionsbeheizte Kalanderwalze
US20100206505A1 (en) * 2009-02-13 2010-08-19 Dan Clarahan Method and apparatus for drying of fibrous webs

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2273423A (en) 1939-06-23 1942-02-17 Budd Industion Heating Inc Electrically heated roll
GB949484A (en) 1960-06-25 1964-02-12 Escher Wyss Gmbh Improvements in or relating to rotatable heating cylinders for paper webs or the like
EP0067786A2 (de) 1981-06-16 1982-12-22 Beloit Corporation Vorrichtung zur Erhitzung der zylindrischen Wand eines Drehzylinders in einer Papiermaschine
EP0277905A2 (de) * 1987-02-03 1988-08-10 Beloit Corporation Heizmethode zum Heizen einer Kalanderrolle
DE20217966U1 (de) * 2002-11-20 2004-04-01 Eduard Küsters, Maschinenfabrik, GmbH & Co. KG Induktionsbeheizte Kalanderwalze
US20100206505A1 (en) * 2009-02-13 2010-08-19 Dan Clarahan Method and apparatus for drying of fibrous webs

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"High Frequency Induction Heating, First Edition", 1 January 1944, article FRANK W. CURTIS: "High Frequency Induction Heating", pages: 1 - 64, XP093166386
STANLEY ZINN: "Coil design and Fabrication: basic design and modifications", HEAT TREATING, 1 June 1988 (1988-06-01), pages 32 - 41, XP093166373

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