Note: Descriptions are shown in the official language in which they were submitted.
CA 02555809 2006-08-09
Voith Paper Patent GmbH P-1702 WO
Method for Heating a Roller, and Heatable Roller
This invention relates to a method for heating a roller used in the
production and/or finishing of a web of material, particularly a paper web
or paperboard web. It also relates to a heatable roller according to the
prior-art portion of claim 26.
For the usual heatable rollers used hitherto in the production and/or
finishing of paper, heat is transported into the roller by means of a heat
medium. As such, the heat required for heating the roller is transferred
indirectly. In this case the medium concerned, which as a rule is oil or
water, is heated by means of an external heating unit. As a rule provision
was made for operation with electricity, firing with gas or operation with
steam.
The object of the present invention is to create an improved method and
an improved heatable roller of the type initially referred to. In particular
the use of renewable fuels should also be possible.
With regard to the method, this object is accomplished in that the heat
required for heating the roller is generated at least in part inside the
roller
by combusting a fuel with air or oxygen at least in some regions inside the
roller.
Hence the heat is generated where it is required. Furthermore, renewable
energies can now be used to generate the heat required. In this case the
roller can be operated in particular in the manner of a catalytic burner.
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According to a preferred practical embodiment of the method according to
the invention the heat is generated at least in part on inner heat transfer
surfaces of the roller which are coated with a catalyst. The heat can be
generated at least in part in at least one space inside the roller which is
filled with a catalytic carrier or equipped with a catalytic surface.
A fuel gas is preferably used as fuel.
According to an advantageous practical embodiment of the method
according to the invention an exothermic reaction is made to take place on
the catalyst using a mixture of fuel gas and air in an adjustable or
adjusted mixture ratio.
According to another advantageous embodiment the mixture of fuel gas
and air is fed to peripheral bores in the roller and an exothermic reaction
is made to take place in these peripheral bores. The peripheral bores can
extend generally parallel to the roller axis. The heat gas from the
peripheral bores is fed preferably via radial ducts to a duct-filled annular
region near the roller surface. As such, the annular region in question can
be provided in particular in the roller casing.
The mixture of fuel gas and air is expediently fed to the roller via at least
one rotary inlet.
However, the exothermic reaction can also take place in a duct-filled
annular region near the roller surface. This duct-filled annular region can
be fed, for example, with fuel gas via peripheral bores in the roller and
radial ducts extending therefrom and, for example, with air via a central
roller bore and radial ducts extending therefrom. However, it is also
conceivable to supply a mixture of fuel gas and air.
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The significant advantage of a catalytic reaction is that the reaction takes
place locally on the catalytically coated surface (ducts in the annular
region). If supply lines (peripheral bores, radial bores and central roller
bores) are not coated, a mixture of fuel gas and air will not react here.
Only the ducts in the inside region are coated and it is only here that a
reaction of the reaction mixture with heat transfer takes place.
The mixing of air and fuel gas prior to feeding into the roller is not a
disadvantage therefore. However, mixing inside the roller requires
additional supply lines, ducts etc. and would be more complex. In
principle, such supplying of a mixture is also conceivable however.
Hence in this case too, peripheral bores extending in particular parallel to
the roller axis can again be provided. However, here the exothermic
reaction does not take place in these peripheral bores but in the duct-
filled annular region near the roller surface. The peripheral bores can be
used, for example, to feed the fuel gas, while air is fed via the central
roller
bore for example. In principle, however, such an embodiment in which a
mixture of fuel gas and air is fed via the peripheral bores is also
conceivable.
Again, the fuel gas or the air is expediently fed to the roller via at least
one
rotary inlet.
According to a preferred practical embodiment of the method according to
the invention, the roller is heatable on a zone basis viewed in the direction
of the roller axis, with the various zones being heatable independently of
each other at least in part. As such, the zones in question can be operated
singly or in groups.
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In the case of a roller with a casing rotating around a non-rotatable core
the exothermic reaction can also take place in particular in the region of
the surface of the roller core or in a duct-filled annular region of the
rotatable roller casing. Hence an expedient alternative to an exothermic
reaction in the region of the surface of the roller core is, as previously
explained, the reaction in the duct-filled annular region of the rotatable
roller casing.
In this case an embodiment is conceivable such that, for example, the
upright roller core is divided into two parts, namely into an air inlet and a
waste gas outlet. Between the upright roller core and the rotatable roller
casing provision can be made for seals which enclose the annular regions
between both bodies. Through bores in the roller core, connections can be
made alternately between the air inlet or the waste gas outlet and the
annular regions. Radial bores in the roller casing can be used for
connection of the catalytically coated ducts with the annular regions.
The roller is preferably divided by means of seals and several feed ducts or
bores opening into the duct structures for fuel gas and air or a mixture of
fuel gas and air into various axial zones that are heatable independently of
each other at least in part. Lines feeding the fuel gas can open into the
feed ducts or bores. Furthermore, these feed ducts or bores can
communicate with an air-conveying central bore of the roller core.
The reaction or roller temperature is advantageously set by means of the
fuel/air mass flow ratio (stoichiometry).
In certain cases an overstoichiometric combustion or combustion with a
surplus of oxygen can be expedient.
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The fuel used can be particularly hydrogen. In particular the use of
reformat or an I-~2-rich gas obtained from natural gas is also an advantage.
5 In particular at least one noble metal such as in particular platinum,
palladium, rhodium and/or the like can be used as catalyst.
The fuel gas mass flow is advantageously controlled such that particularly
a volumetric flow measurement and a corresponding control valve can be
provided as well.
It is also an advantage particularly if the fuel gas concentration in the air
is controlled preferably by means of a fuel gas sensor and a corresponding
control valve.
It is expedient for the roller temperature as well to be controlled.
Again, a respective control can also take place particularly on a zone
basis, whereby the zones can be controlled singly or in groups.
With regard to the heatable roller, the object of the invention mentioned
above is accomplished in that the heat required for heating is generated at
least in part by combusting a fuel with air or oxygen inside the roller.
Preferred embodiments of the heatable roller are specified in the
subclaims.
The duct structures provided on the surface of the roller core for the
embodiment in question can be produced by etching or milling at least in
part.
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The coating with the catalyst can be produced, for example, by rinse
coating, dip coating or spray coating.
The roller casing is preferably shrink-fitted and/or soldered to the roller
core.
The invention will be described in more detail in the following text using
exemplary embodiments and with reference to the drawing, in which:
figure 1 is a schematic representation, partly in section, of a heatable
roller fed with fuel gas and operated in the manner of a
catalytic burner,
figure 2 is a schematic representation in cross-section of an
embodiment of the heatable roller on which the mixture of fuel
gas and air is fed to peripheral bores in the roller and the
exothermic reaction takes place in these bores,
figure 3 is a plan view of the heatable roller according to figure 3
showing the ducts provided near the surface to which the heat
gas is fed from the peripheral bores,
figure 4 is a schematic representation in cross-section of another
embodiment of the heatable roller on which the exothermic
reaction takes place in a duct-filled annular region near the
roller surface,
figure 5 is a schematic perspective representation of the core of
another embodiment of the heatable roller on which the
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exothermic reaction takes place in the region of the surface of
the roller core,
figure 6 is a schematic perspective representation of an embodiment of
the heatable roller with a non-rotating core according to figure
5, also showing the casing that rotates around this core, and
figure 7 is a schematic partial representation in section of another
embodiment of the heatable roller with a non-rotating core,
but in this case the exothermic reaction again takes place in a
duct-filled annular region of the rotatable roller casing.
In a schematic representation, partly in section, figure 1 shows a heatable
roller 10 which is fed with fuel gas or a mixture of fuel gas and air and
operated in the manner of a catalytic burner. The roller 10 can be for use
particularly in the production and/or finishing of a web of material,
particularly a paper web or paperboard web.
The heat required for heating the roller 10 is generated at least in part by
combusting a fuel with air or oxygen inside the roller 10. Hence the roller
10 is configured in the manner of a catalytic burner.
In this case the roller 10 has inner heat transfer surfaces 12 coated with a
catalyst, on which the exothermic chemical reaction takes place.
Alternatively or in addition to this, the roller can also comprise at least
one inner space which is filled with a catalytic carrier or equipped with a
catalytic surface.
A fuel gas, for example hydrogen or the like, can be provided as fuel.
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In the case under consideration the heatable roller 10 is fed with a
mixture of fuel gas and air in a mixture ratio that is adjustable for an
exothermic reaction on the catalyst.
As is evident from figure 1, the air is made available by means of an air
blower 14 and fed first via a line section 16 to a mixing point 18, to which
the fuel gas is fed via another line section 20 in order to be mixed with the
air.
The mixture of fuel gas and air is then fed via a line section 22 to a heat
transfer device 24, from which the mixture is fed via a line section 26 to
the catalyst-coated heat transfer surfaces 12 and in which the freshly fed
mixture is preheated via a line section 26 by means of the waste gas or
waste air returned from the heat transfer surfaces 12 of the roller 10.
A control valve 28 and a device 30 for volumetric flow measurement are
provided in the line section 20 which feeds the fuel gas.
A fuel gas sensor 32 is arranged in the line section 22 provided between
the mixing point 18 and the heat transfer device 24.
The waste gas or the waste air is passed out of the heat transfer device via
a line section 34.
On the embodiment under consideration the mixture of fuel gas and air is
fed to the heat transfer device 24 at a temperature of around 20 °C for
example. In the heat transfer device 24 the mixture is preheated to a
temperature of around 200 °C for example. The waste gas or waste air
returned from the region of the heat transfer surfaces 12 of the roller 10 to
the heat transfer device 24 has a temperature of around 250 °C for
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example. The waste gas or waste air passed out of the heat transfer device
24 has a temperature of around 50 °C for example.
The fuel gas fed via the line section 20 can be in particular hydrogen or,
for example, a reformat or an Ha-rich gas obtained from natural gas.
The reaction or roller temperature can be set by means of the fuel/air
mass flow ratio (stoichiometry). In principle, an overstoichiometric
combustion or combustion with a surplus of oxygen can also take place.
The catalyst can be, for example, a noble metal such as in particular
platinum, palladium, rhodium and/or the like.
Control of the fuel gas mass flow is possible by means of the control valve
and the device 30 for volumetric flow measurement.
The fuel gas concentration in the air can be controlled by means of the
fuel gas sensor 32 and, for example, the control valve 38.
It is possible in particular for the roller temperature as well to be
controlled by means of a corresponding control valve.
In a schematic representation in cross-section, figure 2 shows an
embodiment of the heatable roller 10 on which the mixture of fuel gas and
air is fed to peripheral bores 36, E of the roller 10 extending generally
parallel to the roller axis.
The heat gas from the peripheral bores 36, E is fed via radial ducts 38, E
to an annular region 42 filled with ducts 40 near the roller surface. The
exothermic reaction takes place in these ducts 40.
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In the case under consideration, twelve peripheral bores 36 are provided
for example, whereby the mixture of fuel gas and air is fed via six (36, E)
of these peripheral bores to the roller. Here "E" stands for the German
5 "Eintritt", which means "inlet".
In addition, twelve radial bores 38 are provided. In this case the mixture of
fuel gas and air flows via six (38, E) of these twelve radial bores in the
direction of the distributor ducts 43, E.
As such, there are twelve bores in a sectional plane of the roller, while
several bore planes are provided in axial direction.
The gas mixture is distributed via the distributor ducts 43, E in axial
direction and then flows via the ducts 40 in the annular region 42 to the
distributor ducts 43, A. Here "A" stands for the German word "Austria"
which means "outlet".
The channels 40 in the annular region 42 are catalytically coated. The
exothermic reaction thus takes place here.
The reaction product flows via the remaining six radial bores 38, A into
the peripheral bores 36, A, through which it is discharged from the roller.
Figure 3 shows a plan view of a part of the heatable roller 10 according to
figure 3, showing the ducts 40 provided near the roller surface to which
the heat gas is fed from the peripheral bores 36, E (cf. figure 2).
The mixture of fuel gas and air can be fed to the roller 10 via at least one
rotary inlet.
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Figure 4 shows in a schematic representation in cross-section another
embodiment of the heatable roller 10 on which the exothermic reaction
takes place in a duct-filled annular region 44 near the roller surface.
Again, this duct-filled annular region 44 near the roller surface is fed with
a mixture of fuel gas and air via peripheral bores 46 of the roller 10, which
extend generally parallel to the roller axis, and radial ducts 48 extending
therefrom. The reaction products (waste gases) are discharged from the
roller via radial ducts 52 and the central roller bore 50.
Again, the mixture of fuel gas and air can be fed to the roller 10 via at
least one rotary inlet in the case under consideration as well.
Figure 5 shows in a schematic perspective representation the non-rotating
core 54 of another embodiment of the heatable roller 10 (cf. in particular
figure 6) on which the exothermic reaction takes place, for example, in the
region of the surface of the roller core 54. Such an embodiment is an
advantage particularly if the roller 10 is heatable on a zone basis viewed in
the direction of the roller axis, meaning the various zones are heatable
independently of each other at least in part.
Figure 6 shows in a schematic perspective representation a heatable roller
10 equipped with such a core 54 according to figure 5, including the
casing 54 that rotates around this core 54.
In the case under consideration the surface of the roller core 54, for
example, is thus coated with a catalyst at least in part.
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As is evident from figure 5, the roller 10 in the case under consideration is
divided by means of seals 58 and several feed ducts or bores 60 opening
into the duct structures for fuel gas and air or a mixture of fuel gas and
air into axial zones that are heatable independently of each other at least
in part. Lines 62 for the fuel gas open in the case under consideration into
the feed ducts or bores 60. Furthermore, the feed ducts or bores 60
communicate with an air-conveying central bore 64 of the roller core 54,
through which the resulting waste gas is also discharged.
Whereas on the embodiment just described the exothermic reaction takes
pace in the region of the surface of the roller core, figure 7 shows in a
schematic partial representation in section another embodiment of the
heatable roller 10 on which the reaction again takes place in an annular
region of the rotatable roller casing 56 filled with ducts 40. Again, the
roller 10 is heatable on a zone basis.
The non-rotating roller core 54 is divided in the middle. The division into
two parts results in an air inlet 66 and a waste gas outlet 68.
Between the upright roller core 54 and the rotatable roller casing 56
provision is made for seals 70 which enclose the annular regions 72
between the two bodies. Through radial bores 74 provided in the roller
core 54, connections are made alternately between the air inlet 66 or the
waste gas outlet 68 and the annular regions 72. Radial bores 76 in the
roller casing 56 connect the catalytically coated ducts 40 with the annular
regions 72.
Fuel gas is fed in via supply lines 78.
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Hence in the case under consideration the reaction zones lie in the
catalytically coated ducts 40.
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List of reference numerals
Heatable roller
12 Heat transfer surfaces coated with a
catalyst
5 14 Air blower
16 Line section
18 Mixing point
Line section
22 Line section
10 24 Heat transfer device
26 Line section
28 Control valve
Device for volumetric flow measurement
32 Fuel gas sensor
15 34 Line section
36 Peripheral bore
38 Radial duct
Ducts
42 Duct-filled annular region
20 43 Distributor duct
44 Duct-filled annular region
46 Peripheral bore
48 Radial duct
Central roller bore
25 52 Radial duct
54 Roller core
56 Roller casing
58 Seal
Feed duct, feed opening
30 62 Line
64 Central bore
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66 Air inlet
6g Waste gas outlet
70 Seal
72 Annular region
5 74 Radial bore
76 Radial bore
7g Fuel gas supply line
