DE102008042285A1 - Heatable cylinder i.e. drying cylinder, for use in material web manufacturing and/or treatment machine i.e. paper machine, has heating resistors influencing temperature gradient and middle temperature of inner cylinder barrel - Google Patents

Abstract

The cylinder i.e. drying cylinder (1) has an outer cylinder barrel (7) heatable and aligned to a material web and including a middle temperature (T1). An inner cylinder barrel (2) is formed as thick-walled pipe and includes another middle temperature (T2) such that a temperature gradient (delta T) between the cylinder barrels is formed. Heating resistors (100.1-100.6) influence the temperature gradient and one of the temperatures (T2). The resistors are formed as a cooling device and an electrical resistor heater and supply a medium e.g. hot fluid or hot gas such as hot air or vapor. An independent claim is also included for a method of controlling and/or regulating temperature gradients of a heatable cylinder.

Description

Field of the invention

The The present invention relates to a heatable cylinder for heating and draining a paper, board, tissue or other web with an outer cylinder jacket and an inner cylinder Cylinder shell, the outer cylinder shell is heated and directed to the material web.

Next The heated cylinder, the invention also provides a machine for producing and / or treating a material web, in particular Paper or board web, with at least one heatable cylinder available as well as a method of control and / or Regulation of the temperature gradient of a heated cylinder.

State of the art

heated Cylinder, for example, as a drying cylinder in paper machines are used, have long been known. Such cylinders will be from the inside with a heating fluid applied to the outer Surface of the cylinder and the guided on it To heat web and thereby dry. Usually For example, in such a heated cylinder vaporous fluid, in particular water vapor, as heating fluid used. The vaporous fluid flows under, for example Pressure in the cylinder and condenses on the second cylinder wall, wherein the heat of condensation passes into the cylinder jacket and thus on the outside as heating heat is available. The resulting condensate settles in normal operation of the heated cylinder, which is about its longitudinal axis rotates, due to the centrifugal force in the form of a film inside the Cylinder wall and is sucked through a siphon over a pressure difference.

Alternatively, there are heatable drying cylinder with an inner cylinder shell and an outer cylinder shell, wherein below the surface of the outer cylinder shell at least one channel is formed for the passage of a heating fluid. Such a heatable cylinder arrangement is for example in the WO 2006/072505 specified. In a heated cylinder according to the WO 2006/072505 the heating fluid is brought very close to the outer surface of the heated cylinder.

The Wall thickness of the outer cylinder jacket can be kept low in such a heated drying cylinder become.

A heated cylinder with channels for passing a heating fluid shows, for example, the DE 10 2005 043 734 or the WO 2006/072505 ,

In order to further increase the drying capacity, there are drying devices in which a heatable cylinder is additionally acted upon from outside by a medium, for example a medium which flows out of a pressure hood under pressure and strikes a circulating around the outer cylinder surface area band. Such systems are for example from the EP 1793038 or the EP 1081277 known.

In all the previously mentioned embodiments of heatable cylinders, both with and without pressure hood, there is the problem that the outer shell of the cylinder, in particular during heating, has a higher temperature than the inner shell of the cylinder. In the case of stationary operation, the situation is reversed. The cylinder, which is completely warmed up, emits heat on the outside, so the outer cylinder jacket is colder than the inner cylinder. In heated cylinders, in which not the entire volume of the cylinder is occupied by the hot steam, but only a small area, preferably the area directly under the cylinder surface is supplied with steam, there is the problem that the core of the cylinder is a non-heated and so that steam-free room is. Such cylinder shows, for example, the WO 2006/072505 , If the steam-free interior is not hermetically sealed, a heat exchange with the immediate environment through convection occurs and the inner mantle surface as well as the internal cylinder structures cool off very strongly. In the case of cylinders of this kind, this then leads to thermal stresses in the cylinder structure which lead to damage to the cylinder, in the worst case of which it is destroyed.

Description of the invention

task The invention is to overcome the disadvantages of the prior art and in particular to specify a heatable cylinder having an outer and an inner cylinder shell, in which thermal stresses be largely avoided in the cylinder structure.

According to the invention, this object is achieved in that in a heatable cylinder for heating a paper, cardboard, tissue or other material web with an outer cylinder shell and an inner cylinder shell, wherein the outer cylinder shell has a first average temperature and the inner cylinder shell a second average temperature, a device is provided, with a temperature gradient resulting from the difference of mean first and middle second Tem results can be influenced.

Prefers is it in such a device to influence the temperature gradient around a heating device or a cooling device, the second average temperature on the inner cylinder surface can influence.

A allows such heater or cooler it, purposefully heat up the inner cylinder surface or to cool and thus to influence the temperature gradient. Possible heaters would be an electrical Resistance heater, but also heaters, which means hot Media such as hot gases or hot fluids, for example Hot air or steam.

The Influence of the second average temperature on the inner cylindrical surface happens preferably depending on the first and / or the second mean temperature. To determine the first and / or second average temperature are preferred temperature measuring devices intended.

The Temperature measuring devices can at one point of the heated cylinder can be arranged or in several places. As well it is possible to determine the temperature at a time or at different times. It can then both local how time averages are formed which, if a control device is provided, serve to control the heater and Although such that a predetermined temperature gradient over set the cylinder between first and second mean temperature becomes.

The heatable cylinder is particularly preferably one in which a heating fluid is passed directly below the outer cylinder jacket in order to heat this outer cylinder jacket. Such a heated cylinder is for example in the WO 2006/072505 shown. By the conduction of the heating fluid below the outer cylinder jacket surface, it is possible to guide the heating fluid very close to the outer surface of the heated cylinder and increase the heating power at the outer upper surface and thus the drying performance of the heated cylinder by such an arrangement.

In A particularly preferred embodiment of the invention is for Formation of the channel at least one more cylinder jacket inside of the cylinder jacket arranged to the outside Cylinder jacket is spaced. This has the advantage that the entire Inside of the outer cylinder jacket with heating fluid can be acted upon.

Around to be able to increase the drying performance even further, can be provided that the outer cylinder shell supported on the inner cylinder jacket. In this manner And way, it is possible to change the wall thickness of the outer Cylinder mantle very small form, since, for example, the inner Cylinder shell acts as a support cylinder. Also other load-bearing constructions are possible. This in turn increases the drying performance further.

to Support of the outer cylinder jacket on the inner cylinder shell, in particular webs, Pins, rivets, bolts, screws and / or other fasteners be provided. It is also conceivable a one-piece design from the outer or inner cylinder jacket. Prefers are the fasteners over the surface both cylinder jackets distributed, in such a way that They ensure a uniform support.

Especially it is preferred if the webs or other fasteners axially or circumferentially and / or in an intermediate Direction. This is a particularly good support reached. Especially with circumferentially extending webs it is advantageous if these at least partially with openings are provided for the heating fluid. The heating fluid can then not only in the circumferential direction, but also in the longitudinal direction flow of the cylinder.

inner Cylinder shell and outer cylinder shell of the Drying cylinders can be the same or different Consist of materials. It is advantageous in any case, if it is a metallic material, because then a good heat conduction and ensures sufficient stability are. As a material especially for the outer Cylinder jacket is preferably a material with a high thermal conductivity used. In particular steel, preferably boiler steel, Copper, aluminum, composite materials or bronze into consideration. In order to can be a good heat transfer to the over the cylinder in particular the outer cylinder shell guided fibrous web can be achieved. To have a good load capacity To ensure it is advantageous if the inner cylinder jacket is designed as a thick-walled tube. The inner cylinder can but also consist of two or more shells, which, for example the thermal expansion behavior and the load capacity clearly can be improved. In addition to a design as Tube but it is also considered, the inner cylinder jacket as a framework or as chip-rib construction form what in certain applications is advantageous.

As described above, it is particularly advantageous if the heated cylinder is also an off Value and / or control unit includes, which receives a temperature measurement signal of the temperature measuring device for determining the average first and / or second temperature. The recorded by the evaluation and / or control unit temperature measurement signal can then be used to control the heater, so that on the inner cylinder shell a predetermined temperature and thus a predetermined temperature gradient is achieved or maintained.

Preferably, the heatable cylinder according to the invention is used in a dry arrangement in a paper machine for producing a fibrous web. Such a drying arrangement of a paper machine may consist of one or more drying cylinders according to the invention. Conceivable are drying cylinders, in which the fibrous web is guided over the outer cylinder surface, or else drying cylinders, which are surrounded on the outer circumference of a pressure hood. The pressure hood is sealingly arranged to an impermeable band, for example a metal band. This in turn is based on at least one permeable band. The web lies directly on the cylinder surface and has contact with the at least one permeable belt. The hood is pressurized with cooling fluid. The vaporized from the web water condenses due to the temperature gradient generated in at least one permeable band and is led out in this from the drying phase. A drying arrangement with such a pressure hood is for example in the DE 10 2004 017 829 shown.

Dry arrangements with one or more cylinders, for example, show EP 0 657 580 B1 , the disclosure of which is incorporated in full in the present application.

It is particularly preferred if, together with the overpressure hood, which encloses the heatable cylinder at least over part of the outer circumference, the heatable cylinder is wrapped on a part of its outer circumference by at least one wire and one outer sealing tape. Such a drying arrangement is for example from the DE 10 2004 017 810 known. In the arrangement according to the DE 10 2004 017 810 is caused by the pressure of the medium in the pressure hood in the direction of the cylinder, that the impermeable belt, which is guided above the fabric with the fibrous web, against the fabric and thus against the fibrous web is pressed so as to adjust their dry content. The pressure of the medium in such an arrangement on the drying cylinder, which flows from the pressure hood in the direction of the drying cylinder, is considerable. Therefore, it is particularly advantageous if, in a construction with an outer cylinder jacket and an inner cylinder jacket, bending of the cylinder jacket is prevented by corresponding support construction surfaces.

Next the heatable cylinder and a paper machine with a drying arrangement, comprising at least one heatable according to the invention Cylinder, is also a method of control and / or regulation the temperature gradient of a heated cylinder indicated. Here, the mean first temperature of the outer Cylinder jacket and the middle second temperature of the inner Cylinder jacket determined, for example by means of temperature measuring devices like PT100 probe. From the middle first and middle second temperature, a temperature gradient can be determined. For example, depending on this temperature gradient Heating devices can be controlled, the medium first temperature on the inner cylinder surface in such a way adjust that a given temperature gradient is formed becomes. Such a temperature measurement can be temporal as well as local at different times or in different places take place and then averaging based on these measurements respectively.

The Invention will be described below with reference to the embodiments being represented.

It demonstrate

1 a schematic cross section through a drying cylinder according to a first embodiment;

2 a schematic cross section through an alternative drying cylinder according to embodiment 2; and

3 a cross section through a drying arrangement with a pressure hood.

1 shows a schematic cross section of a first embodiment of a heatable cylinder according to the invention, which also serves as a drying cylinder 1 can be designated. The heated cylinder has an outer cylinder jacket 7 on and an inner cylinder jacket 2 on. In the present case, the inner cylinder jacket 2 from a supporting body 8th , which also has a cylindrical shape and a relatively large wall thickness D formed. In principle, this is a thick-walled pipe. The outer cylinder jacket 7 is chosen as thin as possible, for example, with thicknesses in the range of a few millimeters, for example between 50 mm and 4 mm. It is particularly preferred if a steel is used as outer jacket layer, the thermal conductivity being as high as possible is selected.

The fluid, the outer cylinder shell 7 heated, is between the support cylinder 8th , which forms the inner cylinder shell of the heated cylinder jacket, and the outer cylinder shell 7 by a plurality of axially extending cavities 12 passed. As a medium for heating the outer cylinder jacket 7 It is preferred to use a gas, in particular hot steam. The heating medium, in particular the hot steam, causes heating of the outer cylinder jacket to a mean first temperature T1 on the outer circumferential surface. Due to the heat release to the environment inside the cylinder, the temperature T2 on the inner cylinder jacket surface is always lower than the temperature T1.

The lower temperature T2 inside results, therefore, in the core (INSIDE) of the cylinder, a free space of hot medium. If this space is not hermetically sealed inside, then a direct heat exchange with the environment arises, for example by convection and the temperature of the inner cylinder jacket 2 is lower than that of the outer cylinder shell 7 , For example, the temperature T1 may be 100 ° C, whereas the temperature at the outer cylinder shell is 170 ° C.

By the release of heat to the environment and the different temperatures inside the cylinder and the outer cylinder shell large temperature gradients can arise, which can lead to a thermal stress in the cylinder structure. In order to be able to influence the temperature gradient ΔT via the cylinder structure, a heating device, for example heating resistors, can be provided in the interior of the cylinder structure 100.1 . 100.2 . 100.4 . 100.4 . 100.5 . 100.6 be provided, which is in direct contact with the inner cylinder surface. The heating resistors can via supply lines of a central power supply 110 can be supplied with power, so that on the inside of the cylinder, a desired temperature is set, in response to a temperature measurement signal, for example, a temperature sensor via a temperature measuring device 200 on the outer cylinder jacket 7 measured and sent to the control unit 120 which in turn is transmitted via lines 130 the power supply 110 the individual heating elements 100.1 . 100.2 . 100.3 . 100.4 . 100.5 . 100.6 controls. That through the cavities 12 passed medium, for example steam, can be under pressure, for example, have a pressure between 1.5 and 13 bar. To the heat transfer from the heating medium, such as steam to the outer cylinder jacket 7 to improve, is provided with advantage, on the inside of the outer cylinder shell 7 To provide grooves or profiles. Between the support body 8th and the outer cylinder jacket 7 are located in the illustrated embodiment distributed over the circumference arranged tie rods 9 , which the outer cylinder jacket 7 against the overpressure of the vapor in the cavities 12 hold on the support body.

In 2 is an alternative embodiment of the embodiment according to 1 shown. Same components as in 1 are again denoted by the same reference numerals. In contrast to the embodiment in FIG 1 be in 2 the cavities 12 from a thinner outer cylinder jacket layer 7 and a thin inner cylinder jacket layer 11 limited. The thin inner cylinder surface layer 11 rests on supports 30 on the support body and is over side walls 6 as a stabilizing connecting element with the outer cylinder jacket 7 connected. Again marked are individual heating elements 100.1 . 100.2 . 100.3 . 100.4 . 100.5 . 100.6 . 100.7 such as 100.8 , which purposefully serve to increase the temperature T2 on the inner cylinder jacket, so that the temperature gradient ΔT is lowered. The measuring device for measuring the temperature on the outer cylindrical surface and the individual control lines to the power supply angle in 2 not be shown in detail. It would also be possible, heating devices (not shown) or heating elements on the support body 8th provide, indirectly via convection or heat conduction to the inner cylinder shell 11 heat.

In 3 is a dry arrangement 1000 in a machine for producing a fibrous web comprising a drying cylinder 1 as in 1 and 2 pictured on his top of a hood 1003 , a so-called pressure hood, surrounded, shown. The train 1004 will be together with the seven 1005 . 1006 over the drying cylinder 1 guided. In addition, when the print medium is a liquid, a dense and moisture-impermeable belt runs 1007 together with the train 1004 on the cylinder 1 away so that the print media does not wet the web. The moisture evaporated from the web in this case is from one or more fabrics 1006 . 1007 added. Below the cylinder 1 are each equidistant from the vertical center axis of the cylinder 1 two back-up rolls 1008 . 1009 attached to the cylinder 1002 in the direction of arrows B and C.

By putting pressure on the cylinder in the direction 1 inflowing gas, the force on the cylinder is greatly increased. These can, for example, via the support rollers 1008 . 1009 be compensated. Another embodiment provides that the rollers serve only the web guide and have no support function.

With The invention is the first time a heatable cylinder, in particular indicated for a dryer section in a paper machine, in the one between the outer cylinder jacket and inner cylinder jacket applied temperature gradient set can be.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - WO 2006/072505 [0004, 0004, 0006, 0008, 0015]
• - DE 102005043734 [0006]
• EP 1793038 [0007]
• - EP 1081277 [0007]
• - DE 102004017829 [0022]
• EP 0657580 B1 [0023]
• - DE 102004017810 [0024, 0024]

Claims (21)

Heatable cylinder ( 1 ) for heating and / or dewatering a paper, cardboard, tissue or other material web with an outer cylinder jacket ( 7 ) and an inner cylinder shell ( 2 ), wherein the outer cylinder jacket is heatable and directed towards the material web and has a first average temperature (T1) and the inner cylinder jacket has a second average temperature (T2), so that a temperature gradient (.DELTA.T) between the outer ( 7 ) and inner cylinder shell ( 2 ), characterized in that a device ( 100.1 . 100.2 . 100.3 . 100.4 . 100.5 . 100.6 ) is provided for influencing the temperature gradient (.DELTA.T). Heated cylinder according to claim 1, characterized in that the device ( 100.1 . 100.2 . 100.3 . 100.4 . 100.5 . 100.6 ) is a heating device for influencing the temperature gradient, which influences the second average temperature (T2). Heated cylinder according to claim 1, characterized in that the means for influencing the temperature gradient is a cooling device, the the second mean temperature (T2) influences. Heated cylinder according to claim 2, characterized in that the heating device has an electrical Resistance heating is. Heated cylinder according to claim 2, characterized in that the heating device means that is a medium, especially a hot gas or a medium hot fluid provides. Heated cylinder according to claim 4, characterized in that the hot gas is either hot air or steam is. Heated cylinder according to one of claims 1 to 6, characterized in that a temperature measuring device ( 200 ) is provided for determining the first middle and / or the second average temperature. Heated cylinder according to one of claims 1 to 7, characterized in that below the outer cylinder shell at least one channel ( 12 ) is formed for the passage of a heating fluid. Heated cylinder according to claim 8, characterized in that the channel ( 12 ) between outer ( 7 ) and inner cylinder shell ( 2 ) is formed. Heated cylinder according to one of claims 1 to 9, characterized in that the outer cylinder shell ( 7 ) on the inner cylinder shell ( 2 ) is supported. Heated cylinder, characterized in that the outer cylinder shell ( 7 ) with the inner cylinder jacket ( 2 ) is connected via radial webs, rods, pins, rivets, bolts, screws and / or other connecting means. Heated cylinder according to one of claims 1 to 11, characterized in that the inner cylinder shell ( 2 ) and the outer cylinder jacket ( 7 ) consist of the same or different metallic material. Heated cylinder according to one of the claims 1 to 12, characterized in that the outer Cylinder shell and / or the inner cylinder shell made of material with high thermal conductivity, in particular steel, preferably boiler steel, copper, aluminum or bronze is made. Heated cylinder according to one of claims 1 to 13, characterized in that the inner cylinder shell ( 2 ) is designed as a thick-walled tube. Heated cylinder according to one of claims 1 to 14, characterized in that an evaluation and / or control unit ( 120 ) is provided, which is a temperature measurement signal of the temperature measuring device ( 200 ) for determining the mean first (T1) and / or second temperature (T2). Heated cylinder according to claim 15, characterized in that the evaluation and / or control unit ( 120 ) in response to the temperature measurement signal drives the heater. Machine for producing and / or treating a material web, in particular paper or board web, with at least one heatable cylinder ( 6 ) according to one of claims 1 to 16. Machine according to claim 17, characterized in that the heatable cylinder ( 1 ) at least on a part of its outer periphery of a pressure hood ( 1003 ) is entwined. Machine according to claim 18, characterized in that the heatable cylinder ( 1 ) on a part of its outer circumference of at least one sieve ( 1005 ) and an impermeable band ( 1007 ) is entwined. Method for controlling and / or regulating the temperature gradient of a heatable cylinder ( 1 ), wherein the cylinder has a heated, äuß his cylinder jacket ( 7 ) having a mean first temperature (T1) and a heatable inner cylinder jacket ( 2 ) having a mean second temperature (T2) and a temperature measuring device ( 200 ) for determining the mean first and / or middle second temperature, comprising the following steps: - the mean first (T1) and / or middle second temperature (T2) is determined by means of the temperature measuring device ( 200 ) and the temperature gradient (ΔT) is determined; - In dependence on the temperature gradient, the heater is controlled and set the average first temperature on the inner cylinder jacket surface. A method according to claim 20, characterized in that the average first (T1) and / or the middle second temperature (T2) of the temperature measuring device ( 200 ) at one or more points of the inner and / or outer cylinder jacket ( 2 . 7 ) are measured in time and for setting a constant average temperature gradient (.DELTA.T) between the outer and the inner cylinder jacket surface, the heating device ( 100.1 . 100.2 . 100.3 . 100.4 . 100.5 . 100.6 ) is regulated.