U.S. patent application number 09/738515 was filed with the patent office on 2001-09-06 for arrangement and method for recovery of energy in a paper machine.
This patent application is currently assigned to Aktiebolag, Valmet-Karlstad. Invention is credited to Eriksson, Soren.
Application Number | 20010018958 09/738515 |
Document ID | / |
Family ID | 27356005 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010018958 |
Kind Code |
A1 |
Eriksson, Soren |
September 6, 2001 |
Arrangement and method for recovery of energy in a paper
machine
Abstract
The invention relates to a method of recovering energy in a
forming section of a papermaking or boardmaking machine, wherein
stock from a headbox is fed into a forming zone of a forming
section, said forming zone including at least one looped forming
fabric curving along a convex surface of a support member, and
water is drained from the stock through said at least one forming
fabric in the forming zone to form a paper or board web, the water
passing through said at least one fabric being thrown out from the
forming zone and possessing kinetic energy, characterized by
placing a movable component in the water thrown out from the
forming zone, so as to cause the water to move the component, and
thereby recovering part of the kinetic energy. The invention also
relates to an arrangement in a papermaking or boardmaking
machine.
Inventors: |
Eriksson, Soren; (Charlote,
NC) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Assignee: |
Aktiebolag, Valmet-Karlstad
Karlstad
SE
|
Family ID: |
27356005 |
Appl. No.: |
09/738515 |
Filed: |
December 15, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60230945 |
Sep 6, 2000 |
|
|
|
Current U.S.
Class: |
162/190 ;
162/202; 162/203; 162/264; 162/289; 162/301 |
Current CPC
Class: |
D21F 1/00 20130101; Y02P
70/10 20151101; D21F 1/66 20130101; Y02P 70/24 20151101; D21G 9/00
20130101; D21F 9/003 20130101 |
Class at
Publication: |
162/190 ;
162/202; 162/203; 162/264; 162/289; 162/301 |
International
Class: |
D21F 001/00; D21F
001/66; D21F 011/04; D21F 011/00; D21F 011/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 1999 |
SE |
SE9904602-1 |
Claims
What is claimed is:
1. A method for operating a forming section of a papermaking
machine, the method comprising: discharging stock from a headbox
into a forming zone of the forming section, the forming zone
including at least one forming fabric arranged in a loop and
traveling in the forming zone along a path, water from the stock
being drained through the at least one forming fabric in the
forming zone such that the water exits from the at least one
forming fabric; and capturing the water exiting from the at least
one forming fabric and converting kinetic energy of the water into
a useful form for supplying power to a further device in the
papermaking machine.
2. The method of claim 1, wherein the water is captured by a
movable component that is moved by the captured water, the movable
component converting kinetic energy of the water into useful
form.
3. The method of claim 2, wherein the water is captured by a
turbine that is rotated by the water, the turbine converting
kinetic energy of the water into useful form.
4. The method of claim 3, wherein the at least one forming fabric
in the forming zone passes over a convex surface of a support
member, and the turbine and the support member are disposed on
opposite sides of the at least one forming fabric.
5. The method of claim 4, wherein at least one guide plate is
disposed adjacent the at least one forming fabric for guiding water
expelled therefrom into the turbine.
6. The method of claim 5, wherein the convex surface has a
substantially constant radius of curvature in the forming zone and
the at least one guide plate comprises a first guide plate a major
portion of which is spaced radially outward from and generally
parallel to the convex surface in the forming zone.
7. The method of claim 6, wherein the major portion of the first
guide plate has a substantially constant radius of curvature.
8. The method of claim 7, wherein the radius of curvature of the
major portion of the first guide plate is between about 100 percent
and 120 percent of the radius of curvature of the convex surface of
the support member.
9. The method of claim 7, wherein the support member comprises a
forming roll and the first guide plate has an angular extent of
about 20.degree. to 90.degree. about a center of the forming
roll.
10. The method of claim 9, wherein the forming roll has an
impermeable surface and the first guide plate has an angular extent
of about 40.degree. to 80.degree..
11. The method of claim 9, wherein the forming roll comprises a
vacuum forming roll having a surface that includes perforations and
the first guide plate has an angular extent of about 20.degree. to
50.degree..
12. The method of claim 1, wherein the at least one fabric is moved
through the forming zone at a speed exceeding about 1000 m/min.
13. The method of claim 1, wherein an electric generator is used
for converting the kinetic energy of the water into electrical
energy.
14. The method of claim 1, wherein the water is guided into a
cross-flow turbine by a first guide plate having a leading edge
proximate a location where the stock is discharged from the headbox
and a trailing edge proximate the turbine.
15. The method of claim 14, wherein the water is further guided
into the turbine by a second guide plate having a leading edge
downstream of the trailing edge of the first guide plate.
16. The method of claim 1, wherein the at least one forming fabric
comprises a pair of forming fabrics that converge to form a nip
into which the stock is discharged by the headbox, the forming
fabrics then running together through the forming zone and the
water being expelled through an outer one of the forming
fabrics.
17. An apparatus for forming a paper web in a papermaking machine,
comprising: a support member having a convex surface; at least one
forming fabric arranged in an endless loop and traveling over the
convex surface so as to form a forming zone; a headbox for
discharging stock into the forming zone such that the stock is
deposited onto the at least one forming fabric and water from the
stock is drained through the at least one forming fabric so as to
exit with a substantial velocity from a convex side of the at least
one forming fabric in the forming zone; and a movable component
located proximate the forming zone for capturing the water exiting
from the at least one forming fabric, the movable component being
moved by the exiting water and converting kinetic energy of the
water into a useful form for usage by a further device in the
papermaking machine.
18. The apparatus of claim 17, wherein the movable component
comprises a turbine that is rotated by the exiting water.
19. The apparatus of claim 18, wherein the turbine comprises a
reaction turbine.
20. The apparatus of claim 19, wherein the turbine comprises a
cross-flow turbine.
21. The apparatus of claim 17, wherein the at least one forming
fabric comprises an inner forming fabric that runs over the convex
surface in contact therewith and an outer forming fabric that runs
on top of the inner forming fabric in the forming zone, the outer
forming fabric being arranged in an endless loop and the movable
component being disposed inside the loop of the outer forming
fabric.
22. The apparatus of claim 17, wherein the support member comprises
a forming roll.
23. The apparatus of claim 17, further comprising at least one
guide plate for guiding water to the movable component.
24. The apparatus of claim 23, wherein the convex surface has a
substantially constant radius of curvature along a direction in
which the forming fabric travels in the forming zone and wherein
the at least one guide plate comprises a first guide plate a major
portion of which is spaced radially outward from and generally
parallel to the convex surface in the forming zone.
25. The apparatus of claim 24, wherein the major portion of the
first guide plate has a substantially constant radius of curvature
along the direction in which the forming fabric travels in the
forming zone.
26. The apparatus of claim 25, wherein the radius of curvature of
the major portion of the first guide plate is between about 100
percent and 120 percent of the radius of curvature of the convex
surface of the support member.
27. The apparatus of claim 25, wherein the first guide plate has a
leading edge and a trailing edge with respect to the direction in
which the forming fabric travels in the forming zone, and the first
guide plate has an angular extent between the leading and trailing
edges of about 20.degree. to 90.degree. about a center of the
radius of curvature of the convex surface.
28. The apparatus of claim 27, wherein the convex surface comprises
an impermeable surface of a forming roll and the first guide plate
has an angular extent of about 40.degree. to 80.degree. about a
center of the forming roll.
29. The apparatus of claim 27, wherein the convex surface comprises
a permeable surface of a vacuum forming roll and the first guide
plate has an angular extent of about 40.degree. to 80.degree. about
a center of the forming roll.
30. The apparatus of claim 25, wherein the at least one guide plate
further comprises a second guide plate located downstream of the
first guide plate.
31. The apparatus of claim 30, wherein the second guide plate has a
curvature in an opposite sense to that of the first guide
plate.
32. The apparatus of claim 31, wherein the second guide plate
comprises a wedge-shaped structure that becomes thicker in a
direction in which the water flows over the wedge-shaped
structure.
33. The apparatus of claim 25, wherein the support member comprises
a forming roll and the movable component comprises a turbine
rotatable about an axis parallel to an axis of the forming
roll.
34. The apparatus of claim 33, the turbine having an outer diameter
that is between about 50% and 90% of an outer radius of the forming
roll.
35. The apparatus of claim 33, wherein the turbine has an outer
periphery spaced from the convex surface of the forming roll by a
distance of about 5 mm to 700 mm.
36. The apparatus of claim 33, wherein the turbine comprises a
Banki turbine.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit of the filing
date of U.S. Provisional Patent Application No. 60/230,945, filed
Sep. 6, 2000.
FIELD OF THE INVENTION
[0002] This invention relates to a method of recovering energy in a
forming section of a papermaking or boardmaking machine, wherein
stock from a headbox is fed into a forming zone of a forming
section, the forming zone including at least one looped forming
fabric curving along a convex surface of a support member, and
water is drained from the stock through the forming fabric in the
forming zone to form a paper or board web, the water passing
through the fabric and being thrown out from the forming zone with
a substantial velocity. Moreover, the invention relates to an
apparatus for forming a web in a papermaking or boardmaking
machine.
BACKGROUND OF THE INVENTION
[0003] Paper and board is today produced at very high speeds, and
especially tissue paper, newsprint, and magazine paper. For tissue
the machine speed has today reached 2000 m/min. When forming the
fiber web, for instance in a double wire former, stock is injected
by the headbox in between two forming clothings, which both run
over a wire support, such as a forming roll. The outer clothing is
a wire, which is permeable to water. The other clothing (e.g. a
felt or a wire) is intended to carry the web for further
processing. The stock has a fiber concentration of between 0.1 to
0.5% and the flow is about 0.5 m.sup.3/sec per meter of web width
in the cross-machine direction. The forming of the web occurs by
means of the water within the stock being drained through the outer
flexible fabric, i.e. the wire, such that only a minor portion of
the water is carried on by the fiber web. The water is squeezed out
by the static pressure which is applied by means of the wire which
is pretensioned by lead rolls against the forming roll. Due to the
above mentioned force the water that leaves through the wire will
theoretically normally have a larger speed than the peripheral
speed of the forming roll. Since enormous amounts of water are
drained, e.g. in a normal large tissue machine (6 meters wide) the
flow of drainage water is about 3 m.sup.3/sec, it is realized that
large amounts of energy are released at this point of a paper
machine. Hitherto, none of this energy has been recovered, at least
not the kinetic part thereof, the water merely being collected in a
white water tray for recirculation. The same problem is relevant
also in connection with single wire formers using a single wire and
a forming roll or in a blade former type of a forming section,
wherein a forming roll is not required.
SUMMARY OF THE INVENTION
[0004] It is an object of the invention to minimize the
above-mentioned disadvantages by providing a method and an
apparatus for recovery of a substantial part of the kinetic energy
of the drained white water in a paper machine. In accordance with
the invention, a method for operating a forming section of a paper
machine comprises the steps of discharging stock from a headbox
into a forming zone of the forming section, the forming zone
including at least one forming fabric arranged in a loop and
traveling in the forming zone along a curvilinear path, water from
the stock being drained through the at least one forming fabric in
the forming zone such that the water exits with a substantial
velocity from the at least one forming fabric; and capturing the
water exiting from the at least one forming fabric and converting
kinetic energy of the water into a useful form for supplying power
to a further device in the papermaking machine.
[0005] Preferably, the kinetic energy of the water is converted
into useful form by a movable component placed in the path of the
water exiting from the forming zone such that the moving water
causes the movable component to be moved. In preferred embodiments
of the invention, the movable component is a turbine that is
rotated by the moving water. The turbine preferably is a reaction
turbine, more preferably a cross-flow type of reaction turbine such
as a Banki turbine. A rotating shaft of the turbine can be used for
supplying mechanical power to a further device such as a pump, or
can be used for operating an electrical generator, which in turn
can supply electrical power to a further device. It is particularly
preferred to use the energy provided by the turbine to power a
stock pump of the paper machine.
[0006] In preferred embodiments of the invention, the at least one
forming fabric in the forming zone passes over a convex surface of
a support member, and the turbine and the support member are
disposed on opposite sides of the forming fabric. Preferably, at
least one guide plate is disposed adjacent the forming fabric for
guiding water expelled therefrom into the turbine. The convex
surface preferably has a substantially constant radius of curvature
in the forming zone and the at least one guide plate comprises a
first guide plate a major portion of which is spaced radially
outward from and generally parallel to the convex surface in the
forming zone. The major portion of the first guide plate preferably
also has a substantially constant radius of curvature, which
advantageously is between about 100 percent and 120 percent of the
radius of curvature of the convex surface of the support member.
The support member can be of various types depending on the type of
former used in the paper machine. For example, the support member
can be a forming roll, a forming shoe, or a series of dewatering
blades. Where a forming roll is employed, the first guide plate
preferably has an angular extent of about 20.degree. to 90.degree.
about a center of the forming roll. The optimal angular extent of
the guide plate can depend on the type of forming roll used.
Advantageously, when the forming roll has an impermeable surface
the first guide plate has an angular extent of about 40.degree. to
80.degree., whereas when the forming roll comprises a vacuum
forming roll the first guide plate has an angular extent of about
20.degree. to 50.degree..
[0007] By the invention surprisingly large amounts of energy may be
recovered from the kinetic energy of the water which is taken out
from the stock during the dewatering process in connection with the
forming of the web. Calculations show that for a tissue twin wire
machine having a 6-meter wide headbox and a machine speed of 1800
m/min up to 800 kW can be recovered, which implies a saving of
about 2 million SEK/year. Since the investment cost is relatively
moderate, the pay-off time can be made very short depending on the
price of electricity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] In the following the invention is described in more detail
with reference to the accompanying drawings, in which:
[0009] FIG. 1 shows a schematic side view of an arrangement
according to the invention;
[0010] FIG. 2 shows a side view of essential parts of a preferred
embodiment according to the invention;
[0011] FIG. 3 shows a modification of the embodiment shown in FIG.
2;
[0012] FIG. 4 shows a second modification of the embodiment shown
in FIG. 2;
[0013] FIG. 5 shows a third modification of the embodiment shown in
FIG. 2;
[0014] FIG. 6 shows a perspective view of essential parts of an
embodiment of the invention;
[0015] FIG. 7 shows an embodiment of the invention in connection
with a so-called "C-former";
[0016] FIG. 8 shows the principle of the invention in connection
with a so-called "S-former";
[0017] FIG. 9 shows the principles of the invention in connection
with a C-former having a vacuum roll;
[0018] FIG. 10 shows the principles of the invention in connection
with a so called speed former;
[0019] FIG. 11 shows the principles of the invention in connection
with a speed former in a horizontal position;
[0020] FIG. 12 shows in principle the same as FIG. 10, but with a
vacuum roll as the forming roll;
[0021] FIG. 13 shows in principle the same as FIG. 11, but with a
vacuum roll as the forming roll; and
[0022] FIG. 14 shows an alternate embodiment of the invention with
a speed former.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout.
[0024] The invention may be used with all kinds of double-wire
formers, i.e. wherein two clothings (two wires, or one wire and a
felt, depending on the need of drainage capacity) run on top of
each other around a support member, e.g. a forming roll. In FIG. 1
there is shown a so-called crescent former comprising a headbox 2,
a forming roll 4, a wire 6 and a felt 10. The forming roll 4 has an
outer surface 4B which is impermeable, i.e. a so-called solid
surface. The forming roll 4 rotates about an axis 4A. The felt 10
runs around the forming roll, in contact with its outer surface 4B,
with an angular extension of contact .alpha. which is slightly more
than 180.degree.. The wire 6 runs around the forming roll 4 on top
of the felt 10 with an angular extension of contact .beta. which is
less than 180.degree.. The wire 6 is pressed against the felt on
top of the surface 4B of the forming roll 4 by means of an upper
guiding roll 8A and a lower guiding roll 8B. The headbox 2 injects
stock 21 through its discharge opening 22 into a nip 12, which is
formed where the wire 6 meets the felt 10. According to the
invention, a turbine 14 is positioned in close proximity to the
periphery of the forming roll 4. A guide plate 16 having a radius
R2 which is slightly larger than the radius R1 of the forming roll
4 (see FIG. 2) is positioned at a distance from the forming roll 4
between the nip 12 and the turbine 14. The angular extension
.gamma. of the guide plate 16 is about 35.degree., and its upstream
edge 16A is positioned close to the nip 2, whereas its downstream
end 16B is positioned close to the turbine 14. Downstream of the
turbine 14 close to the periphery of the forming roll 4 there is
positioned a second guide plate 17, behind and below the turbine
14. The axis 14A of the turbine is connected to an electric
generator 11 (schematically shown), preferably by means of a
transmission (not shown). The turbine 14 is of a reaction type,
preferably a so-called Banki turbine, which is also called a
cross-flow turbine due to its function. This kind of turbine is
especially suitable in connection with an arrangement according to
the invention, since it is very well suited for recovering energy
from water moving with relatively high speed, as will be the case
according to the invention. The guide plate 16 has a constant
curvature R2, which is slightly larger than the radius R1 of the
forming roll 4. Advantageously, the guide plate radius of curvature
R2 is between about 100 percent and 120 percent of the forming roll
radius R1, and more preferably is about 105 percent of the radius
R1 of the forming roll 4. The guide plate 16 is positioned such
that its concave surface 16C, which forms the path along which the
water is guided, is positioned about 20 to 50 mm above the surface
of the wire 6. There is a white water tray 18 for collecting the
water shed from the forming zone.
[0025] The function of an arrangement according to the invention is
as follows. Once the felt 10 and the wire 6 of the forming section
are running at the desired speed, e.g. 1500 m/min, stock 21 is
injected by means of discharge opening 22 of the headbox 2. The
stock is supplied into the nip 12 and thereafter it follows between
the two clothings 6, 10 and the forming roll 4. A major amount of
the water contained in the stock 21 will be squeezed out through
the wire 6 by wire tension. As a result, the water that is squeezed
out will have a slightly higher speed than the peripheral speed of
the forming roll 4. Tests show that if the peripheral speed is 30
m/sec, the speed of the water droplets will be about 30.4 m/sec.
For a roll with an impermeable surface as used in FIG. 1, the
dewatering will occur along about 60.degree. of an angular zone
starting at the nip 12. The dewatering flow is largest during the
first 10.degree. then slightly decreases. The droplets will be
collected on a curved surface 16C of the guide plate 16, which is
formed to create as little turbulence as possible, which is
achieved by having the surface 16C with as little irregularities as
possible and by using a constant curvature. The water will collect
along the guide plate 16 and finally be guided into the turbine 14
with an optimal direction of flow to recover as much of the kinetic
energy as possible. For a cross-flow turbine (e.g. Banki turbine)
14, about 80% of the energy is recovered during the flow into the
turbine and about 20% during the flow out of the turbine. This
cross-flow function is the reason why a Banki turbine is
particularly suitable. Downstream of the turbine 14 there is a
second guide plate 17, which has a reversed curvature in relation
to the first guide plate 16 to guide a further amount of water into
the turbine 14. The rotation of the turbine 14, which is caused by
the water, will be transferred by its axis 14A to a transmission
(not shown) coupled to an electric generator for producing electric
energy. A transmission is favorable in most applications to
transform the rotational speed of the turbine 14 to a rotational
speed which is optimal for the generator 11. It is evident that
different kinds of generators may be used, e.g. alternator or
continuous current generator, depending on the circumstances.
[0026] In the preferred embodiment the electrical power which is
produced by the generator 11 is supplied to the stock pumps (not
shown), which feed the headbox 2.
[0027] In accordance with the invention, large amounts of energy
may be recovered. With an optimized arrangement the total yield may
be about 60%. If the stock flow is about 0.5 m.sup.3/sec per cross
sectional meter, the power that can be recovered for a six meter
wide machine is about 810 kW. At a price of 0.30 SEK/kW, this will
lead to annual saving of about 2 MSEK with 350 days of operation
per year. Considering further aspects of the invention, e.g.
environmentally friendly, it is realized that the achievements of
the invention are surprisingly positive.
[0028] FIG. 2 shows a more detailed view of an embodiment according
to the invention. The basic principles thereof are exactly the same
as in relation to FIG. 1, except the positioning of the arrangement
and the use of a second wire instead of the felt 10. In FIG. 2 the
headbox 2 is positioned below the center 4A of the forming roll 4
and the injection discharge opening 22 is directed upwardly. The
radius R1 of the forming roll is 760 mm. The radius R2 of the guide
plate 16 is constant and about 810 mm. The center of the constant
curvature of the guide plate 16 is offset in relation to the center
4A of the forming roll, i.e. 50 mm above the center 4A of the
forming roll 4. The shortest distance 1.sub.1 between the guide
plate and the periphery of the forming roll (wire 6) is about 35
mm. Due to the offset location of the center 16E of curvature of
the guide plate 16 the distance increases constantly in the upward
direction. The distance between the turbine 14 and the periphery 4B
of the forming roll 4 is about 50 mm. (Normally the distance should
be between 10 and 100 mm, preferably between 20 and 70 mm.)
[0029] The second guide plate 17, which is substantially flat, is
positioned with its edge 17A close to the periphery 4B of the
forming roll 4, e.g. about 10 mm between the edge 17A and the wire
6. The cross sectional length 12 of the second guide plate 17 is
about 50 mm. The width of the guide plates in the cross-machine
direction would normally be the same, i.e., the same as the
turbine. Accordingly the first guide plate 16 directs the major
part of the moving water into the turbine 14 with a first direction
adapted to the angle of the turbine blades at the position of the
downstream end 16B of the guide plate at that position. The
direction of the extension of the second guide plate 17 is adapted
to the optimal angle of the turbine blades at that position. Around
the turbine 14 there is a housing 19. The housing comprises several
parts, namely, an innermost upper part 19A, an outermost lower part
19B, a lowermost inner part 19C, and a lowermost base part 19D. The
different parts are attached to each other by means of flanges 19F.
At the bottom of the housing 19, there are flanges 19E for
attachment of the housing to the white water tray 18 of the paper
machine. The uppermost part of the housing 19A (positioned
downstream of the guide plate 16) is fitted to enclose, at a short
distance, a large part of the periphery 14B of the turbine in order
to guide the water in a correct manner, to be further explained in
relation to FIG. 3. The outer diameter T of the turbine is 500 mm.
The inner diameter of the turbine B is 340 mm.
[0030] FIG. 3 shows an embodiment which is similar to FIG. 2, with
the exception that the turbine 14 is positioned further away from
the forming roll 4. As a consequence, the last part of the inner
surface 16C of the guide plate is made flat. It is important that
the transition from the constant curvature to this straight part is
smooth without formation of any turbulence-creating features. Also,
the second guide pate 17 is different from that of FIG. 2. In order
to guide the water, it is made substantially longer, such that its
length 13 is about {fraction (1/4)} of the radius R1 of the forming
roll, i.e. about 200 mm. The second guide plate is curved in an
opposite manner in comparison with the first guide plate 16.
[0031] The lines F.sub.1 to F.sub.4 show different flow patterns of
the water passing through the turbine. The major part of the water
will pass through the turbine 14 along the flow line F.sub.1.
Accordingly, the water is first redirected and imparts energy to
the turbine wheel 14 at the entrance, which gives the flow line
F.sub.1 through the inner part of the turbine and finally the
moving water hits the turbine crosswise, i.e. from the inside
moving out and imparts further kinetic energy thereto. The water
entering into the turbine by means of the second guide plate 17
will move through the turbine along a flow pattern according to
F.sub.4. This cross-flow pattern of the Banki turbine is especially
suitable for use in connection with the invention.
[0032] In FIG. 4 there is shown a number of guide plates 17, 17',
17" downstream of the first guide plate 16 for the turbine 14. The
different guide plates are positioned such that the innermost edges
17A, 17A', 17A" are about equally spaced apart. Each successive
guide plate captures water that managed to bypass earlier guide
plates. In other aspects, this embodiment is similar to what is
described in relation to FIG. 2.
[0033] In FIG. 5 there is shown a further embodiment using several
devices for guiding the water downstream of the turbine. Instead of
using a single plate-shaped element as a guide plate, V-shaped
elements 17, 21; 17', 23 are used to direct the water for the first
two guiding devices. A first device 17, 21 comprises a guide plate
17 which is substantially positioned as shown in FIG. 4. Joined
with its front edge 17A there is a further guide plate 21 which is
positioned substantially tangentially in relation to the periphery
of the forming roll 4. Behind its rear end 21B there is formed an
opening between it and the downstream end 17'A of the second guide
plate 17'. In a similar manner there is a second tangentially
positioned guide plate 23, which has its front end 23A joined with
the front end 17A' of the second guide plate 17', such that a
second opening is formed to allow the water to be directed along a
third downstream guide plate 17". Also here the different flow
patterns (F.sub.1 to F.sub.4) of the water coming from the
different guide plates can be seen.
[0034] In FIG. 6 there is shown a perspective view of some
essential parts of the arrangement according to the invention,
except for the headbox and the electric generator, which are not
shown. As can be seen, the cross-machine widths of the various
parts 4, 6, 8, 10, 14, 16 are substantially the same. It should be
noted that the turbine, the cover parts 19A, 19B and the guide
plate 16 are not shown in their working positions. As can be seen,
the turbine 14 is divided into sections by means of annular support
plates 14E, 14F, 14G, such that each section is about 1 m to 1.8 m
wide.
[0035] In the following the invention will be shown arranged in
different positions in relation to some known kinds of formers.
[0036] In FIG. 7 there is shown a C-former (as well as in FIG. 1),
wherein the headbox 2 is positioned underneath the forming roll 4.
Consequently, the web W is formed during an upward motion around
the forming roll 4. The other parts 6, 10, 8, 14, 16, 17 of the
invention are arranged accordingly, i.e. the guide plate 16 is
positioned below the turbine 14 (but upstream thereof as in FIG.
1). Also in FIG. 7 (as well as in FIG. 1) the forming roll 4 has an
impermeable surface.
[0037] In FIG. 8 there is also shown an impermeable forming roll 4
but of the so called S-former type. According to an S-former the
wire 10 moves around one of the lead rolls 8A and then again around
a third lead roll 8C. The wire 6 is guided substantially along the
same principles as within the C-former, i.e. around two lead rolls
8A, 8B which urges it against the forming roll 4. The arrangement
of the other parts 14, 16, 17 of this embodiment of the invention
is in principle the same as described above.
[0038] In FIG. 9 there is shown a C-former with a vacuum roll as
the forming roll 4. Accordingly, the guide plate 16 may preferably
have about half the angular extension .gamma. as if the forming
roll 4 has an impermeable surface, e.g. about 25 to 40.degree..
Furthermore, it is shown that a second turbine 14' is arranged on
the opposite side of the forming roll from the first turbine 14. It
has been shown that in connection with the vacuum roll 4 about 60%
of the water is drained within the first part, i.e. at the area
where the guide plate 16 is positioned. The remaining amount, i.e.
40%, is drained after the vacuum section of the roll. The vacuum
section of the roll 4 begins shortly in front of the nip 12 and
extends somewhat downstream (the same direction as the rotation of
the forming roll) of the position where the wire 10 gets out of
contact with the surface of the forming roll 4. Accordingly, the
water which has been sucked into the wire and the forming roll 4
will leave it at this position and the kinetic energy thereof is
recovered in the second turbine 14' in the same way as in
connection with the first turbine 14. Thus, there is a first guide
plate 16' and a second guide plate 17' for guiding the remaining
amount of the water into this second turbine 14'.
[0039] In FIG. 10 there is shown a speed former with an arrangement
according to the invention. In the speed former the wires 6 and 10
jointly move with the web W therebetween, firstly over the forming
roll 4, thereafter over a blade former 5, and thereafter over a
vacuum roll 3, after which the wire 6 and the web W are separated
from the wire 10, which is moved around a second lead roll 8A. The
principles for the use of the energy recovering parts 14, 16, 17,
19 according to this embodiment are generally the same as described
above. Alternatively the forming roll 4 may be substituted by a
blade former (not shown).
[0040] In FIG. 11 substantially the same arrangement as in FIG. 10
is shown, except that the speed former has been displaced about
90.degree..
[0041] In FIG. 12 there is shown a speed former positioned in the
same way as shown in FIG. 10. Contrary to what is shown in FIG. 10,
there is used a vacuum roll as the forming roll 4. Two energy
recovering units 14, 16; 14', 16' are used to recover energy from
the drained water, substantially in the same way as described in
relation to FIG. 9.
[0042] FIG. 13 is the same as FIG. 12 but with the speed former
displaced 90.degree..
[0043] FIG. 14 also shows in principle the same as FIG. 12 but with
the speed former displaced 180.degree..
[0044] The invention is not limited to the embodiments shown above
but they may be varied within the scope of the appending claims.
For instance, it is evident for the person skilled in the art that
other kinds of recovering means than a Banki turbine may be used,
e.g. other kind of turbines or even a device working along the
principles of an endless chain conveyor. Furthermore, it is evident
that the recovered energy may be used to directly drive another
unit/machine, e.g. to drive a pump via an appropriate transmission.
For the person skilled in the art it is also obvious that the
invention may be used in connection with a forming roll and a
single wire former, forming with different types of wire support.
However, in this case the water will not be squeezed out through
the forming clothing but drained therethrough by gravitation or by
means of a vacuum box, as is known per se. In order to recover the
kinetic energy the sides of the vacuum box will have to be adopted
to the direction of movement of the water leaving the forming
clothing, such that it is guided in an optimal manner to a turbine
or some other means which is positioned to receive the guided water
in an optimal manner, essentially in the same manner as described
above in relation to the guiding plate. Moreover the principles of
the invention may also be used in connection with a dewatering
section where the water flow is directed to the sides of the paper
machine, where turbines are positioned to recover the energy in
accordance with the principles of the invention as described above.
This latter embodiment would normally not be preferred since the
moving water would have to be guided a long distance from the
forming roll to the position where its kinetic energy is recovered.
Tests have shown that the kinetic energy decreases exponentially in
relation to a distance that the water has to flow along the guiding
plate, before entry into the turbine. Accordingly, it is preferred
to have the turbine positioned adjacent the forming roll as
described in connection with the embodiments shown in the figures.
Moreover, it is obvious for the skilled man that a felt 10 may in
many installations be exchanged by a wire and vice versa. Finally,
it is evident for the skilled man that the invention may be used in
connection with double-wire formers which do not use any roll in
the forming zone, e.g. in connection with a former described in
U.S. Pat. Nos. 4,308,097; 4,416,730; and 5,853,544.
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