EP1738022B1 - Heated cylinder - Google Patents

Abstract

Disclosed is a heated cylinder ( 1 ) for heating a paper web, cardboard web, tissue web, or another fiber web in a machine used for producing and/or refining the fiber web. Said heated cylinder ( 1 ) comprises a cylinder sleeve which is impinged upon at least in part from the inside by a hot fluid and is provided with at least one inner and an outer sleeve layer ( 5, 6 ). The inventive heated cylinder ( 1 ) is characterized in that the two sleeve layers ( 5, 6 ) are separated from each other by a hollow space into which the fluid can be introduced.

Description

The invention relates to a heated cylinder for heating a paper, cardboard, tissue or another fibrous web in a machine for producing and / or finishing the fibrous web with a cylinder jacket, which is acted upon at least partially from the inside by means of a hot fluid and at least one inner and outer sheath layer.

Such a heated cylinder is known from the DE 102 60 509.2 , In the known cylinder, tensile stresses, which arise because the inner region of the cylinder expands more than the outer region, are minimized by the fact that the cylinder jacket consists of at least two cladding layers and the material of the outer cladding layer at a mounting temperature below the average operating temperature is, a larger coefficient of thermal expansion and at a mounting temperature, which is above the average operating temperature, a smaller coefficient of thermal expansion than the material of the inner cladding layer has. Another measure is that the layer thickness of the outer cladding layer is less than that of the inner cladding layer.

In drying cylinders of this kind, a temperature gradient arises in the paper drying process towards the surface. The surface temperature of the cylinder is less than the temperature of the steam used to heat the cylinder; and thus the drying capacity is limited. Increasing the saturated steam temperature is usually not useful for economic reasons.

From the EP 0 559 628 B1 a dryer for drying a fibrous web is known in which a flow cylinder is used in conjunction with a Anblasaube. This is provided with a nozzle arrangement, with the aid of which drying gas jets are applied to the outer surface of the web to be dried, while this is guided around the heated cylinder over a sector of about 270 ° or more. The mantle of the cylinder is with a system of Cylinder is led around. The jacket of the cylinder is provided with a system of ductwork into which a coolant can be directed from a coolant source. By the drying gas jets, water in the web is evaporated to the outside and removed through spaces in the Anblasaube. On the other hand, water condenses from the web on the cooled surface of the cylinder and is sucked through the perforation in the outer shell of the cylinder and a pressure prevailing in the interior of the cylinder vacuum. The entire interior of the cylinder is available to receive the condensate. As a result, the inner wall of the cylinder must have a certain minimum wall thickness in order to withstand the pressure loads at the cylinder diameters used can.

From the US 3,425,488 . DE 38 19 391 . US 4,781,795 . DE 199 360 77 and US 4,453,593 are known double-shell cylinder, in which extend from the outer to the inner shell webs, which serve to support the outer on the inner shell and to form a channel for conducting fluid.

It is the object of the invention to increase the drying performance of a heatable cylinder.

This object is achieved in a heatable cylinder of the type mentioned above in that the two cladding layers are separated from each other by a cavity into which the fluid is introduced, wherein on the cavity facing inner surface of the outer cladding layer, a structure with ribs or Slats is applied by which the inner surface is increased. The twin-shell design of the drying cylinder reduces and keeps the temperature gradient between the cylinder surface and the steam low. During operation, the condensate collects at the bottom of the ribbing. Even a small condensate film thickness would have a strong heat insulating effect and increase the temperature gradient to the cylinder surface. The flank area of the ribbing, however, is not covered with condensate and therefore is in direct contact with the steam; This ensures a high heat flow. Also, due to the increased surface area of the outer shell of the cylinder as a result of the ribbing, the heat transfer becomes due to the enlargement of the contact surface with the steam improved.

By the invention, the wall thickness of the outer cladding layer can be kept low; In particular, the loads of the outer wall of the cylinder by supports against the core of the cylinder or by cross struts can be kept low. Due to the thus possible low wall thickness of the outer jacket layer of the cylinder and the temperature gradient is kept low in this cladding layer. By reducing the thermal resistance over the conventional cylinders, the drying performance of the cylinder can be increased with the same vapor pressure by improving the heat flow through the outer jacket layer and increasing the temperature at the outer cylinder surface.

Interior pressure is applied, the pressure acts in the bivalve solution according to the invention only in the annular cross section between the inside of the outer shell and the outside of the inner shell, which are fixed to each other by means of connecting elements. The outer shell is thereby retained on the connecting elements by the pressure acting in the opposite direction on the inner shell, and also reduces the burden on the inner shell. The load remaining for both shells is due to the pressure and the difference in the areas subjected to pressure, which corresponds to the difference between their diameters.

The shells can be made much thinner by reducing the load and allow for the same load capacity, a reduction in dead weight and the lower wall thickness of the outer sheath an improvement in heat transfer.

The measure according to the invention proves to be particularly advantageous in the case of a drying arrangement in which the cylinder, as shown in FIG EP 0 559 628 B1 is known, over a large, for example 270 ° sweeping area of its mantle surface is covered with a hood.

The hood is filled with a medium, in particular with water, under an overpressure of 1 to 5 bar. The fact that the hood is stationary and does not surround the entire circumference, acts on the mantle surface, a cyclic load. At a point on the lateral surface of the cylinder, therefore, a compressive load acts as soon as the point moves into the area wrapped by the pressure hood. A discharge takes place as soon as he leaves this area. The pressurization causes a high mechanical load, which still acts cyclically with each revolution on the cylinder surface. Drying cylinders of conventional design could not withstand such a pressure load.

Advantageous developments emerge from the dependent claims, the Advantageous developments emerge from the subclaims, the description and the drawings.

In particular, it is advantageous if the inner cladding layer is thicker in relation to the outer cladding layer.

The outer shell is preferably made thin-walled and has a wall thickness in the range between 5 and 15 mm, in particular between 8 to 15 mm. It is connected to the rigid core of the cylinder via webs. Between the thin outer shell and the core is the vapor space.

Advantageously, the vapor in the cavity between the two cladding layers has an overpressure between 2 and 13 bar.

An advantageous embodiment provides that by using the ribs or other structures on the inside of the cylinder jacket whose inner surface can be increased by a factor of 10 to 100. In other words, the surface area of the rib, honeycomb or lattice structure is ten to hundreds times the inner surface of the inner surface outer cladding layer.

For good heat conduction, at least the ribs or, in addition, the inside of the roll shell are made of copper or aluminum. However, the applied on the inside of the roll shell structures can also be made of steel or stainless steel or other metal or other metal alloy, if the factor is chosen to increase the surface sufficiently large.

Preferably, the material used to improve the thermal conductivity is the same as that of the cylinder jacket connected to the structures, to ensure that no stresses arise due to different thermal expansions.

Advantageously, a cylinder is used in which the outer cladding layer of a material with high thermal conductivity, d. H. with a high thermal conductivity exists.

Preferably, the outer jacket layer is made of boiler steel. Steels with an austenitic structure are less suitable.

The material that makes up the inner cladding layer does not have to meet any special thermal conductivity requirements; It is advantageous, however, if the inner cladding layer has a high modulus of elasticity and at least the strength of an average structural steel.

The advantages of the invention are that, since the steam propagates only in channels, there is little mechanical stress. A high heat flux density is possible by a reduced temperature gradient to the surface. The heated cylinder is suitable for high pressure loads from the outside and for high temperature stresses.

If the cylinder according to the invention is used with the same surface temperature as conventional drying cylinders, a steam with a lower saturated steam pressure can be used. When the steam is used in a combined heat and power system, it can expand to a lower pressure in the turbine and thus generate more electrical energy.

It is advantageous if the cylinder is connected via lines between the inner and the outer jacket layer via rotary feedthroughs with a stationary steam supply or an evaporation and condensate water tank.

Because the inner cladding layer has the supporting function and serves as a stiff core, it absorbs the loads acting on the outer cladding layer.

In one embodiment of the invention it is provided that the inner and outer cladding layer via pins, screws, rivets u. Like. Are connected.

As an alternative or in addition to the above-described embodiments of the cylinder in which ribs or webs are used between the inner and the outer shell wall, in one embodiment of the invention it is provided that laminations are arranged between the inner and the outer shell layer.

The lamellae are preferably arranged parallel to one another, in particular in the axial direction or also in the circumferential direction of the cylinder, but alternatively also crosswise, helically or in a honeycomb or lattice structure. In the case of a helical structure, a few fins form a helical coil around the longitudinal axis of the cylinder. In all structures, it is ensured that the vapor is led back out of the cylinder from an inlet side of the cylinder on the inside of its outer jacket wall, giving off a considerable part of its heat content to the outer jacket wall.

The slats have either a flat or a profiled surface. It is also advantageous if the lamellae spread to the outer shell shell.

In one embodiment of the invention, it is provided that the surface of the structure on the inside of the outer circumferential side cladding layer in the vicinity of the end face decreases. This is achieved either by a lesser height of the fins, the honeycomb or the grille, or the distances between the fins or the walls of the honeycomb or the grille are greater in the edge region than in the middle of the outer jacket layer. By reducing the surface of the heat-transmitting structure overheating of the front edges of the cladding layer is avoided.

The invention also relates to a heated cylinder for heating a paper, board, tissue or other fibrous web in a machine for producing and / or finishing the fibrous web, which has only a single outer cylinder jacket.

This is inventively characterized by a high stability that it is supported by struts in the interior of the cylinder. The struts are, for example, radially extending rods; However, it can also be provided support walls that pass through the longitudinal axis. The struts or walls give the cylinder such stability that the shell wall must have only a small thickness. It consists of a highly thermally conductive material which releases the introduced into the interior of the cylinder via a fluid heat to the guided over the outer jacket wall fibrous web. This achieves an increased energy yield compared with the prior art and a reduction in operating costs.

Fig. 1

einen Querschnitt durch einen ersten Zylinder,

Fig. 2

einen Längsschnitt durch den Zylinder gemäß Fig. 1,

Fig. 3

eine perspektivische Teilansicht auf einen zweiten Zylinder,

Fig. 4

ein stark vergrößertes Detail aus dem Mantel des zweiten Zylinders in einer Schnittansicht entlang einer Linie IV - IV in Fig. 3,

Fig. 5

einen Ausschnitt aus einer Schnittansicht eines dritten Zylinders und

The invention will be explained in more detail in a single embodiment. In the attached drawing show:

Fig. 1

a cross section through a first cylinder,

Fig. 2

a longitudinal section through the cylinder according to Fig. 1 .

Fig. 3

a partial perspective view of a second cylinder,

Fig. 4

a greatly enlarged detail of the shell of the second cylinder in a sectional view taken along a line IV - IV in Fig. 3 .

Fig. 5

a section of a sectional view of a third cylinder and

An inserted as a heated cylinder cylinder 1 ( Fig. 1 ) comprises a core with a central axis 2 and ei ne with this over end walls 3, 4 ( Fig. 2 In addition, (not shown here) may be present in the radial direction extending struts between the central axis 2 and the inner shell 5 to increase the stability of the cylinder 1.

The inner shell 5 has a much greater thickness than an outer jacket layer 6. Via webs 7, the inner jacket layer or inner shell 5 is separated from the outer jacket layer 6 and firmly connected to it. The areas between the webs 7 form parallel to the longitudinal axis of the cylinder 1 extending channels, which together constitute the vapor space. Further, ribs 8 are attached on the inside of the cladding layer 6, which enlarge the surface of the cladding layer 6.

The cylinder 1 has in at least one of its bearing journals 9, 10 an outer annular conduit 11 and an inner conduit 12. Instead of the single outer line 11, a plurality of outer lines may be present. Via the outer conduit 11, hot steam flows into the cylinder 1, which is first passed along the end wall 3 and then between the outer shell-side wall of the inner shell 5 and the inner wall of the äuße ren shell layer 6. In this case, heat is released from the steam via the jacket layer 6 to the fibrous web running along it and along the blowing hood. As a result, the steam cools and partially condenses to water. The cooled steam and the condensate from the steam are passed between the end wall 4 of the inner shell 5 and then through a central conduit 13 in the axis 2. The conduit 13 merges into the conduit 12 in the bearing journal 9.

About (not shown here) rotary feedthroughs, the lines 11, 12 are connected to a stationary steam supply or an evaporative and condensate water tank. Instead of guiding both lines 11, 12 through the same bearing pin 9, alternatively, one of the two lines 11, 12 can be passed through the other bearing pin 10.

Also in a further embodiment ( Fig. 3 ), a cylinder 14 is double-shelled. In this case, mainly an inner shell 15 assumes the supporting function and serves as a rigid core which, inter alia, also absorbs the stresses of an outer thin jacket layer 16. The ribbing is in Fig. 3 Not shown.

The connection between the inner shell 15 and the jacket layer 16 is preferably via pins 17, which are either hollow-walled or made of solid material. These can have any cross-sectional shape and be, for example, round, rectangular or hexagonal. The cross-sectional shape can also change over the pin length. The pins 17 are pushed through openings in the cladding layer 16 or in the inner shell 15 and preferably connected by welding, in particular friction welding, or by gluing, screwing, soldering, clamping or other techniques with the cladding layer 16 and / or with the inner shell 15.

The pins 17 may also be designed in two or more parts. For the connection of the parts of the pins 17 under each other com men various methods such as screws, gluing, clamping, welding or plastically deforming methods such as rivets into consideration.

For example, the pins 17 can be prepared in the inner shell 15 in it Screw holes, punched holes or flame cuts in the outer shell with screw threads and connect or glued to the inside of the jacket layer 16 by friction welding. If n the pins 17 consist of two parts, the first part can be, for example, attached to the inside of the cladding layer by friction welding, while the second pin member is pressed with the inner shell 15.

Alternatively, a cylinder 18 constructed essentially like the cylinder 1 (FIG. Fig. 5 ) equipped with an inner wall 19 and an outer wall 20. Between the two walls 19, 20 slats 21 are attached. The fins 21 extend either parallel to the longitudinal axis of the cylinder 18 or are helical. The cavities between the fins 21 are, as in Fig. 2 represented by the cylinder 1, supplied with steam to heat in relation to the inner wall 20 much thinner outer wall 19. The fins 21 are either all the same thickness under each other and all carry the outer wall 20; or between the fins 21 additional reinforced fins 22 are provided, which mainly have a support function, while the fins 21 mainly take over the function of heat conduction. The cylinder 18 is like the cylinder 1 or the cylinder 14 made of steel, in particular stainless steel. The ribbing is in Fig. 5 Not shown.

The fins 21, 22 either have the same cross-section over their entire length, or they widen towards the outer wall 20, as in FIG Fig. 5 shown. In addition, an outer structure can be applied to the lamellae 21, 22 in order to increase the area for the heat transfer between the steam and the outer wall 20 again.

Claims (17)

1. Heated cylinder (1, 14, 18) for heating a paper, board, tissue or another fibrous web in a machine for producing and/or finishing the fibrous web, having a cylinder shell upon which action is taken, at least partly, from the inside by means of a hot fluid and which comprises at least an inner (5, 15, 19) and an outer shell layer (6, 16, 20), the two shell layers (5, 6; 15, 16; 19, 20) being separated from each other by a hollow space, into which the fluid can be introduced,
   characterized in that
   on the inner surface of the outer shell layer (6, 16, 20), facing the hollow space, there is applied a rib structure (8) which extends in the axial or circumferential direction or is helical, a honeycomb or lattice structure, by means of which the inner surface of the outer shell layer is enlarged.
2. Cylinder (1, 14, 18) according to Claim 1, characterized in that the inner shell layer (5, 15, 19) is thicker in relation to the outer shell layer (6, 16, 20).
3. Cylinder (1, 14, 18) according to Claim 1 or 2, characterized in that the outer shell layer (6, 16, 20) has a wall thickness of 8 to 15 mm.
4. Cylinder (1, 14, 18) according to one of Claims 1 to 3, characterized in that the fluid is steam and in that the steam in the hollow space between the two shell layers (5, 6; 15, 16; 19, 20) has a positive pressure between 2 and 13 bar.
5. Cylinder (1, 14, 18) according to one of Claims 1 to 4, characterized in that the rib, honeycomb or lattice structure (8) consists of a material with a high thermal conductivity, in particular of copper or aluminium.
6. Cylinder (1, 14, 18) according to one of Claims 1 to 5, characterized in that the surface of the rib, honeycomb or lattice structure (8) is 10 to 100 times the inner surface of the outer shell layer (6, 16, 20).
7. Cylinder (1, 14, 18) according to one of Claims 1 to 6, characterized in that the outer shell layer (6, 16, 20) consists of a material with a high thermal conductivity.
8. Cylinder (1, 14, 18) according to Claim 7, characterized in that the outer shell layer (6, 16) consists of boiler steel.
9. Cylinder (1, 14, 18) according to one of Claims 1 to 8, characterized in that the inner shell layer (5, 15, 19) has a high modulus of elasticity.
10. Cylinder (1, 14, 18) according to one of Claims 1 to 9, characterized in that lines (11, 12) between the inner (5, 15, 19) and the outer shell layer (6, 16, 20) are connected via rotary leadthroughs to a stationary steam supply and to an exhaust steam and condensate container.
11. Cylinder (14, 18) according to one of Claims 1 to 10, characterized in that the inner shell layer (15, 19) has the loadbearing function and is used as a stiffer core which absorbs loadings acting on the outer shell layer (16, 20).
12. Cylinder (14) according to one of Claims 1 to 11, characterized in that the inner (15) and the outer shell layer (16) are connected by webs, pins (17), screws, rivets and the like.
13. Cylinder (18) according to one of Claims 1 to 12, characterized in that slats (21, 22) are fitted between the inner (19) and the outer shell layer (20).
14. Cylinder (18) according to Claim 13, characterized in that the slats (21, 22) are arranged in parallel, in particular in the axial direction of the cylinder (18), crosswise, helically or in a honeycomb structure.
15. Cylinder (18) according to Claim 13 or 14, characterized in that the slats (21, 22) have a planar or a profiled surface.
16. Cylinder (18) according to one of Claims 13 to 15, characterized in that the slats (21, 22) broaden towards the outer shell layer (20).
17. Cylinder (1, 14, 18) according to one of Claims 1 to 16, characterized in that the size of the surface of the rib, honeycomb or lattice structure on the inside of the outer shell layer (6, 16, 20) on the circumference decreases in the vicinity of the end faces (3, 4) of the cylinder (1, 14, 18).

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