Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F9/00—Complete machines for making continuous webs of paper
  • D21F9/003—Complete machines for making continuous webs of paper of the twin-wire type
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/14—Making cellulose wadding, filter or blotting paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F3/00—Press section of machines for making continuous webs of paper
  • D21F3/02—Wet presses
  • D21F3/0209—Wet presses with extended press nip
  • D21F3/0218—Shoe presses
• • 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
  • D21F5/021—Construction of the cylinders

Definitions

• the invention relates to a machine for producing a fibrous web, in particular a tissue or tissue paper web or a single-sided smooth fibrous web, comprising at least one press nip formed between a press shoe comprising a press shoe and a drying cylinder, through which a water-absorbent carrier tape, a water-impermeable press belt and the fibrous web passed are, wherein the drying cylinder comprises a cylindrical part and the end face in each case a front cover.
• the invention also relates to a method for producing a fibrous web, in particular a tissue or tissue paper web or a single-sided smooth fibrous web.
• Machines of this type are known.
• document DE 19860687 A1 describes a machine with a press nip formed between a shoe press unit and a drying cylinder for dewatering tissue webs. It is proposed to use a short press shoe in order to achieve a higher maximum pressing pressure in the press nip at a maximum permitted line load of 90 kN / m for Yankee cylinders. This achieves a higher dry content after the shoe press unit.
• the object of the invention is to improve machines of this type and methods for producing such fibrous webs in terms of drying efficiency and cost-effectiveness.
• the object is achieved by a machine for producing a fibrous web, in particular a tissue or hygienic paper web or a single-sided smooth fibrous web, with at least one press nip formed between a shoe press unit comprising a press shoe and a drying cylinder, through which a water-absorbent carrier tape, a water-impermeable press belt and the Fiber web are passed, wherein the drying cylinder comprises a cylindrical part and the end face in each case a front cover.
• the cylindrical part of the drying cylinder is at least partially made of steel.
• the heat flow to the fibrous web can be increased for more efficient dewatering compared to a cast iron drying cylinder.
• the drying cylinder is exposed during operation mechanical and thermal loads.
• the mechanical loads are essentially composed of the vapor pressure inside the drying cylinder and the pressure of the shoe press unit. Thermal stress results from the heating and the different thermal conditions between the center of the drying cylinder and the two edge zones.
• the use of steel instead of cast iron requires lower safety margins in the strength-appropriate dimensioning.
• the resulting higher mechanical load capacity of the steel drying cylinder allows higher line forces through the shoe press unit.
• the wall thickness at the same mechanical load by the internal pressure of the steam-heated drying cylinder can be made thinner than cast iron cylinder. This leads to a lower heat conduction resistance and to a higher heat flow.
• the vapor pressure inside the drying cylinder can be increased. This allows higher temperatures to be achieved. This also leads to a higher heat flow and increased dewatering of the fibrous web. Due to the invention thus higher dry contents can be achieved after the press nip and the paper production can be increased by increasing the machine speed.
• the machine is particularly suitable for making light weight papers such as tissue papers or plain papers.
• the basis weight is in the range of less than 45 g / m 2 , in particular less than 30 g / m 2 , preferably less than 25 g / m 2 .
• a preferred basis weight range is between 11 g / m 2 and 45 g / m 2 .
• the drying cylinder has a creping doctor for creping the fibrous web. The compression results in a higher specific volume and a higher softness. In the production of one-sided smooth papers, no creping doctor is provided, however, a cleaning scraper for keeping clean thezelzylinderoberfizze the cylindrical part.
• the drying cylinder may also comprise an outer coating of the cylindrical part of metallic or ceramic material for the production of tissue paper.
• the water-absorbing carrier tape can be designed as a felt belt.
• the press nip formed in the web running direction has a length of less than 125 mm, in particular less than 80 mm, preferably less than 70 mm, in particular less than 60 mm.
• a higher maximum pressing pressure in the press nip can be achieved for a given maximum line force.
• the pressure curve has over the press nip length in the web running direction, by specifying a maximum length of the press nip, a steep rise and a steep drop, whereby the fibrous web is only briefly applied to the high maximum pressing pressure. The fibrous web is not compacted thereby. The specific volume thus remains almost intact.
• the press shoe is pressed against the drying cylinder to form the press nip. It is advantageous if the press shoe made of metal, in particular bronze or aluminum. This achieves a uniform pressure profile in the transverse direction of the machine as well as in the web running direction. This in turn results in improved transverse moisture profiles and moisture longitudinal profiles in the fibrous web and thus improves the quality of the fibrous web produced.
• the shoe press unit comprises at least two, each extending in the transverse direction and in the web running direction side by side, pressing elements for pressing the press shoe against the drying cylinder.
• the pressing elements can each be designed, for example, as pressure hoses.
• the pressure hoses are preferably independently pressurizable.
• the profile of the pressing pressure in the web running direction can be adapted to the given production conditions.
• the maximum pressing pressure itself and also its position in the web running direction can be set exactly.
• the second contact pressure element considered in the web running direction is pressed more strongly than the first contact pressure element.
• the exact adjustment of the compression pressure profiles in the transverse direction and in the web running direction is particularly at high heat flux densities, as they are possible by using a drying cylinder made of steel, an advantage.
• the pressing elements extend substantially over the entire press nip in the transverse direction, but at least in the region of the fibrous web width. Additional pressing elements in the edge regions of the press nip can be avoided.
• the press shoe at least in the region of the press nip, has an average press shoe thickness which is equal to or less than 20 mm, in particular equal to or less than 18 mm, preferably equal to or less than 16 mm.
• This has the advantage that the pressing pressure profile in the transverse direction, in particular in the edge regions of the press nip, runs uniformly and constantly.
• the effects of geometric variations of the drying cylinder, for example in the edge regions due to the vapor pressure and the different thermal conditions between the drying cylinder center and the two edge zones can be compensated.
• the flexible soft press shoe can conform to the contour of the drying cylinder during operation of the machine.
• the press shoe Since the press shoe is adapted to the diameter of the drying cylinder, the press shoe thickness in the web running direction is not quite constant. Approximately in the middle of the press nip the press shoe thickness is thereby slightly thinner than at the beginning and at the end of the press nip. The median press shoe thickness is therefore the average of the values of the press shoe thickness at the beginning, in the middle and at the end of the press nip.
• the press shoe at least in the region of the press nip, has an average press shoe thickness which is equal to or greater than 10 mm, in particular equal to or greater than 12 mm, preferably equal to or greater than 14 mm.
• the press shoe thus has a minimum thickness, which on the one hand enables a uniform pressure profile in the web running direction over the entire press nip.
• This resulting minimum bending stiffness ensures a constant position of the press nip end in the web running direction over the entire width of the press nip in the transverse direction. Due to the sharp limitation of the press-nip end, a very strong and even over the width constant pressure drop of the pressing pressure at the end of the press nip can be achieved. A rewetting of the fibrous web by the water-absorbing carrier tape at the end of the press nip can be avoided or at least greatly reduced. The Drainage efficiency is thereby increased considerably.
• the front side of the cylindrical part of the drying cylinder arranged end covers are made of steel and are bolted or welded to the cylindrical part of the drying cylinder or the end covers are made of cast iron and bolted to the cylindrical part of the drying cylinder.
• the drying cylinder is associated with a drying hood for impinging the fibrous web with steam and / or hot air.
• the drying cylinder expediently has a diameter of more than 3 m, in particular more than 4 m, and the interior is filled with steam at a pressure equal to or greater than 0.5 MPa (5 bar), in particular equal to or greater than 0.6 MPa (6 bar), preferably of equal to or greater than 0.7 MPa (7 bar) acted upon.
• the drying cylinder can advantageously be so charged with steam that the surface temperature of the cylindrical part on the outside after the creping doctor or after removal of the fibrous web is more than 100.degree. C., in particular more than 120.degree.
• This temperature level reduces the viscosity of the water contained in the fibrous web in the press nip to optimum values.
• the end covers have a thermal insulation on the outside and / or on the inside. This reduces heat losses and improves the energy balance.
• the shoe press unit is assigned a safety device for opening the press nip, which controls or control unit, wherein the control unit, in the absence of the fibrous web on the water-absorbing carrier tape, causes the pressing elements to be deactivated and / or the shoe press unit to be swung off , Damage to or impairment of the water-absorbing carrier tape or the water-impermeable press belt can be avoided.
• the press shoe with a line force of equal to or more than 90 kN / m, in particular equal to or more than 110 kN / m, preferably equal to or more than 120 kN / m can be pressed against the drying cylinder.
• the drying cylinder is designed and dimensioned in a preferred embodiment so that it can be acted upon by a line force between 60 kN / m and 140 kN / m, preferably between 60 kN / m and 120 kN / m.
• the drying cylinder advantageously has grooves on the inside of the cylindrical part for increasing the mechanical stability and increasing the heat flow.
• the wall thickness of the cylindrical part of the drying cylinder is, without consideration of optional grooves, expediently less than 55 mm, preferably less than or equal to 45 mm. It is possible and advantageous in one embodiment of the invention if the pressure profile resulting in the press nip in the web running direction at a line force of less than or equal to 140 kN / m; in particular of less than or equal to 120 kN / m has a maximum pressure of more than 2 MPa, in particular more than 3 MPa and preferably more than 4 MPa.
• the pressure profile resulting in the press nip in the web running direction at the end of the press nip has a pressure drop of more than 800 kPa / mm, in particular more than 1000 kPa / mm, preferably more than 1100 kPa / mm. This minimizes or prevents rewetting of the fibrous web by the water-absorbing carrier tape.
• the machine comprises a headbox, a peripheral outer sieve, a circulating water-absorbing carrier tape, wherein the headbox emits a pulp suspension between the rotating outer sieve and the circulating water-absorbing carrier tape in the form of a jet, and the outer sieve and the water-absorbing carrier tape partially wrap around a forming roller and wherein the fiber suspension is dewatered in the looping area and the formed fibrous web is guided on the water-accepting carrier belt for further dewatering over an evacuated roller and through the press nip.
• the headbox emits a pulp suspension between the rotating outer sieve and the circulating water-absorbing carrier tape in the form of a jet
• the outer sieve and the water-absorbing carrier tape partially wrap around a forming roller and wherein the fiber suspension is dewatered in the looping area and the formed fibrous web is guided on the water-accepting carrier belt for further dewatering over an evacuated roller and through the press nip.
• the object is also achieved by a method for producing a fibrous web, in particular a tissue or tissue paper web or a one-sided smooth
• Fibrous web dissolved.
• the fibrous web and a water-absorbent carrier tape, and a water-impermeable press belt are formed by at least one shoe press unit comprising a press shoe and a drying cylinder
• the drying cylinder comprises a cylindrical part and the end face in each case a front cover.
• the cylindrical part of the drying cylinder is at least partially made of steel.
• FIG. 1 shows a machine according to the invention for producing a tissue
• FIG. 2 shows a detail of Figure 1 with a shoe press unit and a
• FIG. 3 shows a press shoe in a simplified representation and a pressure-pressure curve in FIG
• FIG. 1 shows a machine 1 according to the invention using the example of a known crescent former.
• the usual Sauganpress roller is replaced by a shoe press unit 5.
• the drying cylinder 7 is associated with a creping doctor as it is commonly used for the production of creped tissue papers.
• This machine 1 is also suitable for the production of one-sided smooth papers with small modifications.
• no creping doctor is provided. It is replaced by a cleaning scraper to keep clean the drying cylinder surface of the cylindrical part 8.
• This is very smooth and preferably has a coating, such as a coating of chromium. In this case, the fibrous web 2 produced is drawn off the drying cylinder surface 8 in free tension.
• the machine 1 comprises a headbox which emits a fibrous suspension between a peripheral outer sieve and a circulating water-absorbing carrier band 11 in the form of a jet.
• the water-absorbing carrier tape 11 is designed as felt.
• the outer screen and the felt 11 partially wrap around a forming roller.
• the pulp suspension is dewatered and the formed fibrous web 2 lying on the felt 11 is guided for further dewatering over an evacuated roll and through the press nip 10.
• the press nip 10 is formed by a press shoe 6 comprising a shoe press unit 5 and the drying cylinder 10. Immediately after the press nip 10, the fibrous web 2 is transferred to the hot surface of the cylindrical part 8 of the steam-heated drying cylinder 7 and dried.
• the drying cylinder 7 is partially surrounded by a drying hood 14 for impinging the fibrous web 2 with steam and / or hot air. Thereafter, the fibrous web 2 is creped by a creping doctor and removed from the surface of the cylindrical portion 8 of the steam-heated drying cylinder 7 and fed via a measuring frame for measuring quality parameters of the fibrous web 2 of the reeling.
• the shoe press unit 5 comprises two, each in the transverse direction 4 extending and in the web running direction 3 side by side, pressing elements (13.1, 13.2) for pressing the press shoe 6 against the drying cylinder 7.
• the pressing elements (13.1, 13.2) are designed as pressure hoses.
• the pressure hoses are pressurized independently of each other.
• the profile of the pressing pressure in the web running direction 3 can be adapted to the given production conditions.
• the maximum pressing pressure itself and also its position in the web running direction 3 can be set exactly.
• the second contact pressure element (13.2), viewed in the web running direction 3 is pressed more strongly than the first pressure element (13.1).
• the exact adjustment of the compression pressure profiles in the transverse direction 4 and in the web running direction 3 is particularly at high heat flux densities, as they are possible by using a drying cylinder 7 made of steel advantage.
• the steam-heated drying cylinder 7 comprises an end cap on the front side.
• the front cover 9 are executed on its outside with a thermal insulation. This reduces heat losses and improves the energy balance.
• the drying cylinder 7 has a diameter of 4.8 m and the interior can be acted upon with steam at a pressure of 0.7 MPa (7 bar).
• the cylindrical part 8 has an outer coating to assist the creping process.
• the press nip 10 has a length of 55 mm in the web running direction 3. As a result, a higher maximum pressing pressure in the press nip 10 can be achieved for a given maximum line force.
• the press shoe 6 is pressed against the drying cylinder 7 to form the press nip 10.
• the press shoe 6 is made of metal, in particular bronze or aluminum and has a ground surface.
• the shoe press unit 5 is associated with a safety device for opening the press nip 10 which includes a control unit - or control unit, in the absence of the fibrous web 2 on the water-absorbing carrier tape 11, causes the pressing elements (13.1, 13.2) of the press shoe to deactivate and / or the shoe press unit 5 to swing. Damage to or impairment of the water-absorbing carrier tape 11 or the water-impermeable press belt 12 can thus be avoided.
• the shoe press unit 5 comprises a press shoe 6 and pressing elements (13.1, 13.2) which are supported on a machine-width yoke mounted in the edge regions of the machine 1. These elements are surrounded by a circumferential, water-impermeable press belt 12. The interior of the water-impermeable press belt 12 is sealed from the environment.
• the two pressing elements (13.1, 13.2) each extend in the transverse direction 4 and are arranged next to one another in the web running direction 3. They press the press shoe 6 to form a press nip 10 against the drying cylinder 7.
• the pressing elements (13.1, 13.2) are designed as pressure hoses.
• FIG. 3 shows a press shoe 6 in a simplified representation from the machine 1 according to FIG. 1 and a pressing pressure profile in the press nip 10 in the web running direction 3.
• the press shoe 6 has an average press shoe thickness 15 in the region of the press nip 10 which is smaller than 20 mm. This has the advantage that the pressing pressure profile in the transverse direction 4, in particular in the edge regions of the press nip 10, runs uniformly and constantly. The effects of geometric variations of the drying cylinder 7, for example in the edge regions due to the vapor pressure and the different thermal conditions between the drying cylinder center and the two edge zones can be compensated.
• the flexible flexible press shoe 10 can conform to the contour of the drying cylinder during operation of the machine, so that the compression pressure profile in the transverse direction 4 is constant. Since the press shoe 6 is adapted to the diameter of the drying cylinder 7, the press shoe thickness (15.1, 15.2) in the web running direction 3 is not completely constant.
• the press shoe thickness is thereby slightly thinner than at the beginning and at the end of the press nip 10.
• the average press shoe thickness is therefore the mean of the values of the press shoe thickness (15.1, 15.2) at the beginning, in the middle and at the end of the press nip 10.
• the press shoe has an average press shoe thickness (15), which is 10 mm, of the press nip 10.
• the press shoe 10 thus has a minimum thickness, which on the one hand enables a uniform pressure profile in the web running direction 3 over the entire press nip. This resulting minimum bending stiffness ensures a constant position of the press nip end in Web running direction 3 and this over the entire width of the press nip in the transverse direction 4.
• the sharp boundary of the press nip can be a very strong and also across the width constant pressure drop of the pressing pressure at the end of the press nip 10 reach.
• a rewetting of the fibrous web 2 by the water-absorbing carrier tape 1 1 at the end of the press nip 10 can be avoided or at least greatly reduced.
• the drainage efficiency is thereby significantly increased. Moisture streaks in the fibrous web due to uneven remoistening can be avoided by the high and constant width pressure drop.
• a pressure profile in the web running direction 3 is shown schematically. The pressing pressure begins at the beginning of the press shoe 6 with a gentle rise and reached shortly before the end of the press shoe 6, the maximum pressing pressure, which drops very steeply to the end.

Landscapes

• Paper (AREA)
• Sanitary Thin Papers (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=52692621

Family Applications (1)

Country Status (5)

Cited By (3)

Families Citing this family (3)

Citations (7)

Family Cites Families (3)

• 2014
  • 2014-07-11 DE DE102014213512.5A patent/DE102014213512A1/de not_active Withdrawn
• 2015
  • 2015-03-13 WO PCT/EP2015/055284 patent/WO2016005064A1/de active Application Filing
  • 2015-03-13 BR BR112017000527A patent/BR112017000527A2/pt active Search and Examination
  • 2015-03-13 CN CN201580037203.0A patent/CN106661836B/zh not_active Expired - Fee Related
  • 2015-03-13 EP EP15710756.6A patent/EP3167115B1/de active Active

Patent Citations (7)

Also Published As

Similar Documents

Legal Events