CA2092004C - Method in contact-free air-drying of a material web as well as a nozzle-blow-box and a pulp dryer that make use of the method - Google Patents
Method in contact-free air-drying of a material web as well as a nozzle-blow-box and a pulp dryer that make use of the methodInfo
- Publication number
- CA2092004C CA2092004C CA002092004A CA2092004A CA2092004C CA 2092004 C CA2092004 C CA 2092004C CA 002092004 A CA002092004 A CA 002092004A CA 2092004 A CA2092004 A CA 2092004A CA 2092004 C CA2092004 C CA 2092004C
- Authority
- CA
- Canada
- Prior art keywords
- nozzle
- web
- blow
- air
- carrier
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000000034 method Methods 0.000 title claims abstract description 27
- 239000000463 material Substances 0.000 title claims abstract description 19
- 238000007605 air drying Methods 0.000 title claims abstract description 7
- 238000007664 blowing Methods 0.000 claims abstract description 73
- 238000012546 transfer Methods 0.000 claims abstract description 33
- 238000001035 drying Methods 0.000 claims description 14
- 230000006641 stabilisation Effects 0.000 claims description 14
- 238000011105 stabilization Methods 0.000 claims description 14
- 230000000694 effects Effects 0.000 claims description 11
- 230000003247 decreasing effect Effects 0.000 claims 1
- 230000001105 regulatory effect Effects 0.000 claims 1
- 238000010276 construction Methods 0.000 description 9
- 238000005259 measurement Methods 0.000 description 7
- 230000006866 deterioration Effects 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000005755 formation reaction Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 235000019506 cigar Nutrition 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 2
- 241000251468 Actinopterygii Species 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F5/00—Dryer section of machines for making continuous webs of paper
- D21F5/18—Drying webs by hot air
- D21F5/185—Supporting webs in hot air dryers
- D21F5/187—Supporting webs in hot air dryers by air jets
- D21F5/188—Blowing devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B13/00—Machines and apparatus for drying fabrics, fibres, yarns, or other materials in long lengths, with progressive movement
- F26B13/10—Arrangements for feeding, heating or supporting materials; Controlling movement, tension or position of materials
- F26B13/101—Supporting materials without tension, e.g. on or between foraminous belts
- F26B13/104—Supporting materials without tension, e.g. on or between foraminous belts supported by fluid jets only; Fluid blowing arrangements for flotation dryers, e.g. coanda nozzles
Landscapes
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Drying Of Solid Materials (AREA)
- Paper (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
The invention relates to a method for air-drying material webs, in particular material webs of relatively high grammage such as pulp webs. The invention also relates to a nozzle-blow-box and a pulp dryer that make use of the method. Air blowings in a direction substantially perpendicular to the web and air blowings in a direction substantially parallel to the plane of the web are applied to the web to be dried from underneath the web. By means of these blowings, both heat is transferred to the web and the web is supported by the air free of contact, and the run of the web through the dryer is stabilized. In order to improve the transfer of heat in comparison with a planar carrier face, the air flow velocity parallel to the plane of the web is initially kept substantially invariable. The air flow velocity is lowered in the lateral areas of the carrier face by employing lateral areas of the nozzle-carrier face that become rampwise and/or stepwise lower in the air-flow direction.
Description
09200~
- MBTHOD IN CONTACT-FREF AIR-DRYING OF A M~FRT~T- WEB A8 ~ELL A8 A NOZZLE-BLO~-BOX AND A PULP DRYER THAT NA~E U8E OF THE METHOD
~- 5 B~ ROUND OF THE ~v~h.lON
:::
The invention relates to a method for air-drying material ~-~ webs, in particular material webs having a relatively high ~- grammage, such as pulp webs. In the method, air blowings are applied in a direction substantially perpendicular to the web and 5 ~10 in a direction substantially parallel to the plane of the web to - be dried from underneath the web. The air blowings cause heat to be transferred to the web, supported the web by air free of contact, and stabilize the run of the web through the dryer.
~- ~ The invention also relates to a nozzle-blow-box of an air . . . - ~~ ~ . .
- - 15 dryer through which box air blowings are applied to the material - i ~
web to be dried. By means of the air blowings, both the transfer .; of heat is produced from the drying air to the web and a contact-free air support and stabilization of the run of the web are obtained. The nozzle-blow-box comprises a box part having a nozzle-carrier face placed against the web. A substantially V-section groove is arranged transverse to the running direction of the web in the middle of the nozzle-carrier face. The groove is opened toward the web and has opposite walls in which a series of nozzle holes are arranged. Support and stabilization air - 25 blowings can be applied out of the series of nozzle holes such that they are crosswise and of opposite directions in relation to each other. Plane nozzle-carrier-face portions are placed in the same plane with each other at both sides of the V-section groove in the nozzle-carrier face.
The invention further relates to a pulp dryer that makes use of the method of the invention and/or the nozzle-blow-box of the invention.
In prior art through-dryers used in the paper and pulp industry, blow boxes are commonly used w~ose nozzle-carrier face :
~ ~UY~IJV4 consists of a plane plate in which blow holes have been punched.
These nozzles are placed either at one side or at both sides of tne airborne web to be dried. The no~zle-carrier-face commonly includes a number of rows of holes, one row after the other in the running direction of the web. The blow air flows in a space between the web and the nozzle-carrier-face, and the blow air is collected away through suction slots placed between the nozzle boxes.
In the prior art direct-blow nozzle boxes of air dryers for paper, board or pulp webs, wherein the air blowings are directed perpendicularly to the material web to be dried, a well-known problem is the lateral flow of the consumed air between the web to be dried and the nozzle-carrier-face. As used in the art, the term "lateral flow" is understood as meaning air flows parallel to the plane of the carrier face and of the web. These air flows are additionally parallel or opposite to the running direction of the web. Since the air must escape from the treatment gap, a ~ -lateral flow cannot be avoided. The lateral flow deteriorates the transfer of heat in the prior art blow-nozzle boxes, and a disturbing effect is increased with an increase in the velocity of the exhaust-air flow. Further, the loss of pressure produced by the blow box is increased when the velocity increases in the lateral flow.
On the other hand, in view of the runnability of the web to be dried, it is preferable to make use of the lateral flow by shaping the blow face in the blow box and the geometry of its nozzle openings such that a zone of negative pressure is formed on the carrier face of the blow box. This zone of negative pressure stabilizes the run of the web and ensures a stable and unstrained run of the web.
With respect to the prior art most closely related to the present invention, reference is made to the Swedish Patent No. SE ~-- . ~
:~ ~
- MBTHOD IN CONTACT-FREF AIR-DRYING OF A M~FRT~T- WEB A8 ~ELL A8 A NOZZLE-BLO~-BOX AND A PULP DRYER THAT NA~E U8E OF THE METHOD
~- 5 B~ ROUND OF THE ~v~h.lON
:::
The invention relates to a method for air-drying material ~-~ webs, in particular material webs having a relatively high ~- grammage, such as pulp webs. In the method, air blowings are applied in a direction substantially perpendicular to the web and 5 ~10 in a direction substantially parallel to the plane of the web to - be dried from underneath the web. The air blowings cause heat to be transferred to the web, supported the web by air free of contact, and stabilize the run of the web through the dryer.
~- ~ The invention also relates to a nozzle-blow-box of an air . . . - ~~ ~ . .
- - 15 dryer through which box air blowings are applied to the material - i ~
web to be dried. By means of the air blowings, both the transfer .; of heat is produced from the drying air to the web and a contact-free air support and stabilization of the run of the web are obtained. The nozzle-blow-box comprises a box part having a nozzle-carrier face placed against the web. A substantially V-section groove is arranged transverse to the running direction of the web in the middle of the nozzle-carrier face. The groove is opened toward the web and has opposite walls in which a series of nozzle holes are arranged. Support and stabilization air - 25 blowings can be applied out of the series of nozzle holes such that they are crosswise and of opposite directions in relation to each other. Plane nozzle-carrier-face portions are placed in the same plane with each other at both sides of the V-section groove in the nozzle-carrier face.
The invention further relates to a pulp dryer that makes use of the method of the invention and/or the nozzle-blow-box of the invention.
In prior art through-dryers used in the paper and pulp industry, blow boxes are commonly used w~ose nozzle-carrier face :
~ ~UY~IJV4 consists of a plane plate in which blow holes have been punched.
These nozzles are placed either at one side or at both sides of tne airborne web to be dried. The no~zle-carrier-face commonly includes a number of rows of holes, one row after the other in the running direction of the web. The blow air flows in a space between the web and the nozzle-carrier-face, and the blow air is collected away through suction slots placed between the nozzle boxes.
In the prior art direct-blow nozzle boxes of air dryers for paper, board or pulp webs, wherein the air blowings are directed perpendicularly to the material web to be dried, a well-known problem is the lateral flow of the consumed air between the web to be dried and the nozzle-carrier-face. As used in the art, the term "lateral flow" is understood as meaning air flows parallel to the plane of the carrier face and of the web. These air flows are additionally parallel or opposite to the running direction of the web. Since the air must escape from the treatment gap, a ~ -lateral flow cannot be avoided. The lateral flow deteriorates the transfer of heat in the prior art blow-nozzle boxes, and a disturbing effect is increased with an increase in the velocity of the exhaust-air flow. Further, the loss of pressure produced by the blow box is increased when the velocity increases in the lateral flow.
On the other hand, in view of the runnability of the web to be dried, it is preferable to make use of the lateral flow by shaping the blow face in the blow box and the geometry of its nozzle openings such that a zone of negative pressure is formed on the carrier face of the blow box. This zone of negative pressure stabilizes the run of the web and ensures a stable and unstrained run of the web.
With respect to the prior art most closely related to the present invention, reference is made to the Swedish Patent No. SE ~-- . ~
:~ ~
2 ¢~ ¢ ) 0 4 .106,152 (corresponding to U.S. ~atent No. 4,50s,053) and to ~nternational Patent Application N.. Wo 88/08950 (corresponding to U.S. Patent No. 5,016,363).
In the blow boxes described in the Swedish patent, triangular openings, so-called "fish eyes", have been punched into the plane nozzle-carrier-face of the blow boxes. The front edge of the openings the front edge, i.e. the base of the triangle, has sharp edges. A sharp edge is not a major drawback as long as the amount of air discharged out of the nozzle is sufficient. However, at times, the amount of air receiv~d by the nozzle may be reduced considerably from the dimensioned value, for example, if the filters for drying air are blocked. In this case, the web starts to contact the nozzle face. It has been noticed that the sharp edges plane material out of the face of, e.g., a pulp web, in which case both the quality of the finished product is deteriorated and rubbish remains in the dryer.
Moreover, the rubbish remaining in the dryer disturbs the threading of the pulp web. In this regard, the formation of a "cigar" is spoken of, for the material detached out of the face of the pulp web by planing forms a roll resembling the structure of a cigar.
In the type of nozzle-blow-boxes employed in pulp dryers in which the web runs above the nozzle and carrier faces of the boxes, the function of the air blowings is both to transfer heat from the blown air to the web and to support the web free of contact. In view of the runnability of the web, it is preferable to blow part of the air in a direction parallel to the plane of the nozzle such that the web is stabilized at a distance of about 3 mm to about 6 mm from the carrier face. However, in such a case, in the prior art nozzle-blow-boxes, the velocity of the exhaust air in the space between the web and the nozzle becomes high. This results in deterioration of the transfer of heat and .
:~ ' ~
'~
20q2304 in extra and/or excessive pressure losses. The detrimental effect of the high velocity of the exhaust air can be reduced by making the nozzles sufficiently narrow, but then the number of the nozzles becomes so high that the cost of manufacture of the dryer is increased substantially.
The present invention is directed towards the further development of the prior art nozzle-blow-boxes described in the afore-mentioned patents while eliminating the drawbacks present therein.
The present invention is also directed towards the provision of a new and improved method and nozzle-blow-box construction by whose means it is possible to avoid the drawbacks discussed above and to improve the transfer of heat from the drying air to the airborne web to be dried. This improvement of the transfer of heat can be utilized most efficiently in the form of a smaller size being required for the dryer. In this manner, the cost of construction, e.g., of a pulp dryer, and the cost of the machine hall in which the dryer will operate can be lowered decisively, particularly the length of the building required to house the pulp dryer.
The present invention is also directed towards reducing the effect of the deterioration of the transfer of heat by the lateral flow while the run of the web is stabilized by means of the lateral flow.
In the method in accordance with one aspect of the present invention, an air flow velocity parallel to the plane of the web to be dried and air-supported in connection with the nozzle-carrier face is initially kept substantially invariable in order to improve the transfer of heat in comparison with a plane carrier face. In this manner, the air flow velocity is lowered in the lateral areas of the carrier face by employing lateral areas B
2092~4 of the nozzle-carrier face that become lower in the air-flow direction.
Accordingly, in one aspect of the present invention, there is provided a method for air-drying material webs in a dryer, comprising:
arranging nozzle-blow-boxes on one side of the web such that a top side of said nozzle-blow-boxes forms said carrier face, arranging a groove space in a middle portion of said carrier face and extending in a direction transverse to a running direction of the web, directing first air blowings to a web to be dried through said first nozzle means in said carrier face in a direction substantially perpendicular to the web, directing second air blowings to the web crosswise through said second nozzle means in a direction substantially parallel to the web, said first and second air blowings transferring heat to the web and supporting the web by air such that a run of the web through a dryer is stabilized, maintaining an initial velocity of said second air blowings to be substantially constant to improve the transfer of heat in comparison with said carrier face, and arranging lateral areas of said plane carrier face to become lower in the flow direction of said second air blowings to lower the velocity of said second air blowings in said lateral areas of said carrier face, and increase the cross-sectional flow area between the web and said carrier face in said lateral areas of said carrier face such that the time of effect of said second air blowings upon a lower face of the web is increased.
The nozzle-blow-box in accordance with one aspect of the invention includes nozzle-carrier face portions having extensions which comprise lateral carrier-face portions 2092G0~
placed further apart from the material web to be supported. The velocities of the support and stabilization air flows in the area of the carrier-face portions are lower as compared with the velocity prevailing in connectlon with the planar nozzle-carrier-face portions. The nozzle-carrier face is provided with nozzle perforations through which additional blowings can be directed from the nozzle-blow-box in a direction substantially perpendicular to the plane of the material web to be supported.
Accordingly, in a second aspect of this invention, there is provided a nozzle-blow-box of an air dryer for directing air blowings to a material web to be dried, the air blowings producing a transfer of heat from the drying air to the web and contact-free air support and stabilization of a run of the web through the air dryer, said nozzle-blow-box comprising:
a box part having a nozzle-carrier face arranged to face the web, a substantially V-section groove arranged in a middle portion of said nozzle-carrier face in a direction transverse to a running direction of the web, said groove being open toward the web and having a series of nozzle holes arranged in opposite walls for directing support and stabilization air blowings to the web, said support and stabilization air blowings being directed crosswise and in opposite directions in relation to each other, said nozzle-carrier face comprising planar nozzle-carrier faces arranged on both sides of said groove and in the same plane with each other, said planar nozzle-carrier faces having extensions comprising lateralcarrier face portions arranged further apart from the web, the velocity of said support and stabilization air blowings being lower in proximity to said lateral carrier-face portions as compared with the velocity of said support and stabilization air blowings prevailing in ~3 20q200~
proximity to said planar nozzle-carrier-face portions, said nozzle-carrier face further comprising nozzle perforations through which additional air blowings are directed from said nozzle-blow-box in a direction substantially perpendicular to the plane of the web.
The effect of the deterioration of the transfer of heat by the lateral flow has been minimized in the present invention by lowering the lateral portions of the nozzle to a level lower than the planar middle portion such that the velocity of the lateral flow is lowered. Moreover, the lateral flows are preferably directed so that they do not directly collide with the air jets being blown directly on the plane face or on the lowered lateral portions.
The lowering of the lateral areas of the nozzle-carrier-face portions in accordance with the invention is based on the idea that a high flow velocity of the exhaust air between the web and the nozzle-carrier face causes a deterioration in the coefficient of heat transfer. Thus, the lower the space between the web and the nozzle-carrier face, the higher the velocity of the exhaust air becomes.
The velocity of the exhaust air is increased in both directions from the center line of the nozzles toward the edges when more air is introduced. When the lateral areas of the nozzle-carrier-face are lowered in accordance with the present invention, the flow velocity in this area is lowered.
' 2~9200~ ~
The nozzle-blow-box in accordance with the invention is a combination of a nozzle with positive/negative pressure in which the magnitude of the lateral flow that produce- the negative pressure is selected appropriately in relation to the amount of air in the direct blowing.
It is an important feature of the hole-no~zle field in the carrier face in accordance with the invention that the coefficient of heat transfer is not substantially dependent on the distance given the relatively small nozzle-to-web distances with which the nozzles of the present invention operates. This feature is achieved, provided that the exhaust air does not disturb the air jets blown out of the nozzle holes to a significant extent. However, it is well known that, when there are several rows of nozzle holes, one row arranged after the other, the air discharged out of the nozzles generally passes toward the edges in the space between the nozzle and the web.
Thus, the higher the flow velocity of the discharged air, the greater the disturbance caused to the air jets blown out of the holes and the greater the deterioration of the coefficient of heat transfer.
In a preferred embodiment of the nozzle-blow-box in accordance with the invention, air jets are directed from the walls of a V-section groove placed in the middle of the nozzle face in a direction crosswise in relation to one another at continuous rounding points between the plane carrier face placed at each side of the walls of the V-section groove. The air jets are tangential to the rounding points so that they turn and become parallel to the plane portions of the carrier face as a result of the Coanda effect. In accordance with the Bernoulli principle, a zone of negative pressure is formed between the web and the carrier faces which stabilizes the web at a certain distance from the carrier face. The distance is generally from ~5 2~92~0~
~ut 3 mm to about 6 mm.
In addition, on the horizontal part of the carrier face in the present invention, attempts are made to avoid direct collisions between the jets of direct blowing and the air jets that flow in the lateral direction.
According to the present invention, the lateral areas of the nozzle-carrier face of the nozzle-blow-box have been lowered so that the velocity of the lateral flow is lowered as the cross-sectional flow area becomes larger. In this manner, the heat-transfer effect of the blow jets coming from the holes of direct blowing placed in the lowered inclined and~o- ~traight nozzle-carrier-face portion is improved.
The nozzle-blow-box in accordance with the invention is suitable for use for drying a web both in on~--ized/two-sided drying, in the case of low-grammage webs ( < 200 g/sq. m), and both underneath and above the web. In the ca~e of heavy webs, such as pulp webs, the nozzle-blow-boxes in accordance with the invention are preferably suitable tor lower nozzles together with direct-blow boxes that operate ~b upper nozzles, or alone as lower nozzle boxes in one-sided drying.
A further advantage is achieved by means of the geometry of the blow-carrier faces of the nozzle-blow-boxes in accordance with the invention. This advantage is that a smooth blow face with no sharp edges is obtained as the air of the lateral flow is introduced out of the central V-section groove while guided by rounded faces. If the web contacts the nozzle face, there are no sharp edges which will tear the web and cause a deterioration in the quality of the finished product and rubbish to remain in the dryer which will disturb the threading of the pulp web.
The transfer of heat to the web can be improved by about 5 to about 10% by means of the present invention, This improvement can be ; -~iately taken and put to use in the form of a reduced . ~ . " . ~ .
~ :
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.
209200~
size of the dryer whlch substantially lowers the cost of the investment of the dryer and the machine hall. Also, this improvement indirectly reduces the number of production interruptions and improves the operating time ratio of the dryer. The advantages mentioned above are particularly important in the case of large and complicated pulp dryers. The nature of the improvements has been quantified by measurements that have been carried out and that will be described in more detail later.
In a nozzle-blow-box in accordance with the invention, a V-section groove is used in the middle of its carrier face. Blowings parallel to the carrier face are applied crosswise through the groove. By means of this arrangement, a rigid mechanical construction is obtained in addition to a favorable blow/heat-transfer technique. The V-section groove rigidifies the nozzle carrier-face efficiently without any other rigidifying structures which would otherwise be necessary.
It is a minor drawback of the blow face of the blow box in accordance with the invention that it is somewhat more difficult to manufacture than a uniform plane face.
However, this drawback can be solved by means of development of the manufacturing technology.
In an additional aspect, the present invention provides a pulp dryer for drying material webs, comprising:
nozzle-blow-boxes arranged at horizontal distances from one another to form spaces therebetween, said nozzle-blow boxes being placed at a distance from a material web to form treatment gaps and directing air at least in a perpendicular direction to the web to support, dry and stabilize the webj the air being removed from said treatment gaps via said spaces, said nozzle-blow-boxes being arranged in the running direction of the web one after B
.
another in a horizontal plane such that rows of said nozzle-blow-boxes are formed in the dryer, a hood through which the web to be dried runs through the dryer supported by air, the web being arranged to run over said rows of said nozzle-blow-boxes in horizontal backward and forward runs arranged in a vertical orientation in the dryer, and reversing rolls for reversing the running direction of the web between said horizontal runs.
The following drawings are illustrative of embodiments of the invention and are not meant to limit the scope of the invention as encompassed by the claims.
Figure 1 is a schematic vertical sectional view in the machine direction of a pulp dryer in which the method and of a set of nozzle-blow-boxes in accordance with the invention are utilized.
Figure 2 is an axonometric view of the modular construction of a pulp dryer in which the method and of a set of nozzle-blow-20~21D0~ ~
es in accordance with the invention are utilized.
Figure 3 is a schematic vertical sectional view in the machine direction of a set of nozzle-blow-boxes in accordance with the invention and of a set of boxes of direct blowing placed above the set of boxes.
Figure 4 is an axonometric illustration of a nozzle-blow-box in accordance with the invention and of the principle of its blowings.
Figure 5 is an axonometric view of the construction of an upper direct-blow box in accordance with the invention and used in a method of the present invention.
Figure 6 shows an embodiment of a carrier face of a nozzle-blow-box in accordance with the invention and of the blow nozzles of the carrier face in more detail, together with important dimensioning parameters.
Figures 7A, 7B, 7C, 7D, and 7E illustrate different variations of different embodiments and dimensions of bevel and step formations of the nozzle-carrier laces ot ~ nozzle-blow-box in accordance with the invention.
Figure 8A shows a nozzle-blow-box as shown in Figs. 4 or 5, viewed from a side of the nozzle-carrier face.
Figure 8B is an enlarged schematic vertb:~l sectional view in the machine direction of a preferred geometry and dimensioning of the V-section groove of the nozzle.
Figure 9 illustrates different relative coefficients of heat transfer of the embodiments illustrated in Figs. 7A to 7E as a function of the distance of the ~eL at a first air-blow velocity.
Figure 10 illustrates the corresponding measurement results in a manner corresponding to Fig. 9, at a second, higher air-blow velocity.
_,.. .~ , ,, ,,. ,, ~
.;
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'' ..
.' 209200~
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~ ntion are utilized. The basic principle of the embodiment of Fig. 2 is, e.g., similar to that illustrated in Fig. 1. The dryer-blower module comprises blower towers 21 and blowers, which are provided with blade wheels 22. The module construction includes heating radiators 24 through which the blow air is passed into the gap between the upper nozzles and the lower nozzles, i.e. into web gap 25. Further, the module construction includes air filters 26. At the operating side of the blower module, a ten~;ng bridge 28 is arranged, in connection with which there are servicing gates 27 for the blower motors and servicing doors 29 for the blower modules. Fig. 2 shows the circulation of the drying air as illustrated by the arrows, and also the nozzle-blow-boxes 30,40 in accordance with the invention and the web gaps 25 between them.
With respect to the above description of Figs. 1 and 2, it is to be emphasized that only one field of application of the method and of the set of nozzle-blow-boxes 30,40 in accordance with the invention are described therein. The method and the set of nozzle-blow-boxes 30,40 in accordance with the invention can also be applied in numerous other environments and also in devices other than pulp dryers, for example in board and paper-web dryers. However, pulp dryers are the most advantageous and primary field of application of the invention wherein several different and distinct advantages of the invention are most appropriately and completely utilized.
Fig. 3 is a schematic illustration ol a s~t of nozzle-blow-boxes 30 in accordance with the invention and ~f an opposite set of boxes 40 of direct blowing. In the followin~J description, the shorter name "lower box" will be used for the no~zle-blow-boxes 30, because they are preferably placed undern~th the horizontally running web W. Free spaces 30a are arranged between the lower boxes 30 and, in a corresponding way, tree spaces 40a .
~: :
~, .
2~92~0~
are arranged between the direct-blow boxes 40. The blow air is , ssed through spaces 30a and 40a further through the heating radiators 24 shown in Fig. 2 and is carried or propelled by the blower 22 back to the blow boxes.
As shown in Fig. 3, the web W to be dried, typically a pulp web, runs as a horizontal run through the web gap 25. The web gap 25 is defined as the distance between the lower boxes 30 as a lower point and the direct-blow boxes 40 as an upper point. The lower boxes 30 are preferably uniformly spaced in one horizontal plane. The direct blow-boxes 40 are also uniformly spaced in a horizontal plane. The web W, which is usually heavy (the weight of a wet pulp web may be up to about 2000 g/sq.m), is supported on the blow boxes 30 by means of the blowings B2 and B3.
Blowings B1 are applied to the web W through nozzle holes 42 placed in the horizontal lower walls of the direct-blow boxes 40 in a direction perpendicular to the plane of the web W. The web W is dried from above by means of these blowings B1.
Figs. 4, 6, and 8A and 8B illustrate the construction of the lower boxes 30 in greater detail. A transverse groove 32 is arranged in the middle portion of a carrier face 31 of the lower boxes. Groove 32 passes across the width of the web W and is opened toward the web W in preferably a V-section. The opening angle of the V-section groove 32 is denoted with a. Angle a is generally from about 50~ to about 90~, preferably a is from about 60- to about 80'. The inclined walls of the V-section groove 32 are preferably plane and arranged to turn and join a horizontal plane portion 34 of the carrier face at an angle k by means of rounded portions 31b having a curve radius R. As shown in Fig.
6, between the angles a and _, there is a relationship a + 2b =
180-.
Both of the inclined plane faces of the V-section groove 32 .
have rows of blow holes 33. These blow holes 33 are arranged and 2()~ OO'1 d ~cted so that the air jets ~ are blown through the blow holes 33 in a direction tangential to the :ounded portions 31b between the plane faces. The rounded portions turn the air jets B3 by the Coanda effect onto the plane portions 34 of the carrier face 31 and make the jets parallel to the plane portions. The blow holes 33 are placed in the opposite sides of the v-section groove 32 and arranged in a staggered arrangement in relation to one another (Fig. 8) such that the blowings B3 are interlocked with one another crosswise in opposite directions. Thus, one set of the blowings B3 is directed parallel to the running direction of the web W and to its plane, whereas the other set of the blowings is directed parallel to the plane of the web W but in a direction opposite to the running direction of the web W.
In accordance with the Bernoulli principle, the blowings B3 induce a zone of negative pressure between the web W and the carrier face 31. This zone stabilizes the web W at a certain --~
distance H from the carrier face 31. The distance H is preferably from about 3 mm to about 6 mm, in which case the air drying of the web W is most efficient.
Lowered lateral portions 35 are placed in both of the lateral areas of the carrier face 31 over its length L in the direction of the web. The height of these lowered lateral portions 35 is lower in relation to the web W than the height of the middle-plane portions 34 of the carrier face 31. According to Fig. 6, lateral portions 35 are inclined plane bevel parts whose distance in relation to the plane parts 34 at the edges of the nozzle box 30 is denoted with h2.
In the nozzle-blow-box in accordance with the invention, the air velocity is first substantially invariable in connection with the plane carrier-face portions 31 in the web W treatment gap 25 underneath the web W. The air velocity is lowered in connection with the carrier-face portions 35,35b,35d,35e which are stepwise . . :~
.
~: '; ~
2092ao4 continuously lowered in height when moving towards the edges of the box 30 and towards spaces 30a in the treatment gap 25. In this manner, the transfer of heat can be intenblfied considerably, as will be described later in connection with the test results illustrated in Figs. 9 and lO. The intensification of the transfer of heat comes largely from th-- ~act that the air-flow velocity parallel to the plane of the web ~ is lowered considerably on the lowered carrier-face portions 35,35b,35d,35e. 5 This intensifies above all the heat transfer ot the direct blowings B2.
In a pulp dryer in accordar7~ ~ith the invention, the lower box 30 and the direct-blow box 40 as shown in Figs. 4 and 5 are placed one above the other and one facing the other so that faces 41 and 31 of the boxes 40,30, respectively, are substantially parallel to one another and generally horizontal. Rounded portions 43a may be arranged at the edges of the faces 41 of the -~
direct-blow boxes 40. Corresponding rounded portions 31a maybe -arranged at the edges of the carrier faces 31 of the lower boxes 30.
The opposite faces 31 and 41 on the lower box 30 and on the direct-blow box 40 are provided with nozzle perforations 42,36, respectively. A preferred distribution of the perforations 36 on the blow box 30 is illustrated in Fig. 8. Perpendicular blowings Bl,Bz are directed against the web W through the perforations 36,42 and the drying of the web W is promoted by means of these perpendicular blowings. The direct blowings B2 will have a longer time of effect on the lower face of the web W as a result of the decrease in the air-flow velocity on the carrier-face portions 35 because of an increased cross-sectional flow area.
Fig. 8B is a schematic illustration of a preferred embodiment of the geometry and a dimensioning example of the V-section groove 32 described above. The geometry shown in Fig. 8B
i' ~ .;
20g20~
!
i ~ymmetric in relation to a transverse vertical center plane K-K. It is important in the design of the V-section groove 32 that the air jets F1 and F2 which are blown from the opposite sides if the groove 32 can be directed tangential to the rounded portions 31b connected with the edges of the groove 32. These air jets will, by the Coanda effect, turn and become parallel to the carrier face 34. The area between the groove 33 and the carrier face 34 must be specifically rounded in such a way that the air starts following the carrier face 34.
Figs. 7A-7E show alternative embodiments of the carrier face of the blow box 30. The nozzle box 30A as shown in Fig. 7A
comprises a carrier face 31 in which plane portions 34 are arranged at both sides of the V-section groove 32. Plane inclined bevel portions 35 are arranged after the plane portions 34 in the air-flow direction.
Fig. 7B shows a particularly advantageous blow box 30B, in which plane portions 34b of the carrier face are arranged at both sides of the V-section groove 32. ~;-ep portions 37 are arranged after the plane portions 34b in t~e ~ir-flow direction. Step portions 37 are perpendicular both to the first plane portions 34b of the carrier face and to plane portions 35b of the carrier face that follow after the step portion 37 in the air-flow direction. The initial parts 34b of the carrier face 31 are preferably parallel to one another and in the same horizontal plane. In a corresponding way, the lateral portions of the carrier face 31 are preferably parallel to one another and in the same horizontal plane.
Fig. 7B also shows a preferred dimensioning example of the nozzle box 30B. According to Fig. 7B, the height h2 of the step portion 37 is about lO mm. Generally, the height of the step portion h2 may vary from about 7 mm to about 15 mm.
In Fig. 7C, a nozzle box 30C is illustrated as a reference, ~ .. , : :, ~ , w~ ~h box has a fully plane carrier face 31c. Properly speaking, this nozzle box 30C is not a preferred embodiment in accordance with the present invention, and it is illustrated in this connection for the sake of reference only. The results of a S comparison including this reference nozzle box are illustrated in Figs. 9 and 10, which will be described in more detail later.
Fig. 7D illustrates a blow box 30D in accordance with the invention, which box has relatively long plane carrier-face portions 34d and relatively short and steep, inclined lateral portions 35d. In Fig. 7D, a preferred dimensioning example is also provided.
In Fig. 7E, an alternative modification of the blow box as shown in Fig. 7B is illustrated. Blow box 30E has relatively long plane carrier-face portions 34e and step portions 37 which are followed by relatively short carrier-face portions 35e in the air-flow direction. Fig. 7E also shows an example of the ;
construction of blow box 3OE.
Fig. 8A shows the relative locations and staggering of the nozzle holes 33 in the V-section groove 32 so that the blowings B3 being blown in opposite directions are blowr crosswise. The perforations 36 in the nozzle-carrier face 31 are placed in four lines or rows, one line after the other, as stagyered in such a way that the blowings B2 and B3 neither meet ea~ other nor disturb each other. The mutual spacing of the rlozzle holes 33 is generally from about 20 mm to about ~,o mm. In a corresponding way, the mutual spacing of the nozz~- holes 36 in the transverse direction and in the machine direction is usually from about 40 mm to about 100 mm.
Further, as to the dimensioning of the blow boxes shown in Figs. 6 and 7, it can be stated as follows, with reference to the denotations in Fig. 6. The angle a of the V-section groove 32 in the middle of the carrier face is generally from about 50~ to c It 90-, in which case the angle k of the Coanda faces 31b is from about 45~ to about 65~. The height h1 of the V-section groove 32 is optimally obtained from the equation h1 = (2 - 5) x ~ wherein ~ is the diameter of the nozzle holes 33 in the walls of the V-section groove 32. The diameter ~ of the nozzle holes 33 is selected relative to the diameter of the direct-blow nozzles 36 in the carrier face so that the air quantity in the carrier-blowings B3 blown through the nozzle holes 33 is about 30% to about 60%, preferably 35~ to about 45%, of the overall air quantity of the blowings B2 and ~.
The length L1 ~f the bevelled or step-formed lateral portions 35,35b,35d,35e in the carrier face 31 is selected according to the equation L1= (0.1 - 0.3) x L, preferably L1 =
(0.2 - 0.25) x L, wherein L is the total length of the blow box 30 in the machine direction. Generally, length L is from about 300 mm to about 500 mm. The difference in height hz of the bevelled portions 35,35d or of the step-formed portions 35b and 35e is selected from about 7 mm to about 15 mm, preferably h2 is about 10 mm.
Figs. 9 and 10 graphically illustrate test results obtained with nozzles as shown in Figs. 7A-7E. In Figs. 9 and 10, the vertical axis represents the relative heat transfer coefficient ~R and the horizontal axis represents the distance of the web W
from the carrier face 31, expressly from its plane portion 34.
In Figs. 7A-7E, the letter symbol after the numeral "7"
corresponds to the curves A-E in Figs. 9 and 10. ~-Of the nozzle arrangement described above, versions as shown in Figs. 7A-7E were made and the transfer of heat was examined in a static test device by blowing hot air against a plane metal face. The efficiency of the transfer of heat w~s obtained by measuring the heating rate of the plate by mearls of temperature-measurement detectors inlaid in the plate.
.~. .
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209~Jo4 In Figs. 9 and 10, the measured relative heat-transfer coefficients ~R are illustrated as a function of the distance H
between the web and the carrier face 31 of the nozzle box at two different blow velocities. According to the results, a lowering h1 of the lateral portions 35,35b,35d,35e provides an increase in the range of about 5% to about 10% in the coefficient of heat transfer as compared with a plane carrier face (Fig. 7C, carrier face 31c), when the distance H equals the normal airborne distance of a pulp web W (between about 3 mm and 6 mm). In contrast, at larger distances H, a lowering or decrease of the lateral portions 35 does not give any corresponding advantage.
The increase was highest in the case of the nozzles at which the lateral portions 35,35b of the carrier face 31 had been lowered most, on the average (Figs. 7A and 7B). The measurement results provided in Fig. 9 were obtained with a blow velocity of w~h is -about 26 m/s of the blowings B2 and B3. The results given in Fig. 10 were obtained with a corresponding blow velocity of w~h is about 34 m/s, while the temperature T~h of the blow air was about 150~C. As shown in Figs. 9 and 10, there are substantially large differences in the relative heat-transfer coefficient ~R
exactly at the optimal airborne web W distances, i.e. when H is between 3 mm and 6 mm.
The simulation and measurement method employed in the measurements of Figs. 9 and 10 has been described in more detail in a paper by P. Heikkila and I. Jokioinen, "Airfoil Dryer Heat Transfer", published in The Helsinki Symposium on Alternate Methods of Pulp and Paper Drying in Helsinki, June 4-7 (1991).
Based on the measurements described above, the most advantageous embodiment of the invention is, according to the present-day opinion and on the basis of the available measurement results, the blow-nozzle box 30A as shown in Fig. 7A. According to the measurement results of Figs. 9 and 10, a carrier face 2~200 1 ,35b with a steep step formation ~7, as sho~n in Fig. 7B, is optimal in view of the transfer of heat. However, a nozzle-blow-box 30A as shown in Fig. 7A, whic~ 5 provided with continuously lowering ramp-formed lateral portions 35 of the carrier face, is preferable in an overall consideration because the risk of formation of a "cigar" is lower for this nozzle-blow-box 30A as the geometry of the blow face does not include sharp angles.
Thus, according to a present-day estimate, a nozzle-blow-box 30A 5 as shown in Fig. 7A (also in respect of its dimensions) is the most preferable embodiment of the invention in a situation in which the distance, e.g., of a pulp web W from the horizo~tal portion 34 of the carrier face 31 is about 5 mm.
The examples provided above are not meant to be exclusive.
Many other variations of the present invention would be obvious to those skilled in the art, and are contemplated to be within the scope of the appended claims.
. - ~
In the blow boxes described in the Swedish patent, triangular openings, so-called "fish eyes", have been punched into the plane nozzle-carrier-face of the blow boxes. The front edge of the openings the front edge, i.e. the base of the triangle, has sharp edges. A sharp edge is not a major drawback as long as the amount of air discharged out of the nozzle is sufficient. However, at times, the amount of air receiv~d by the nozzle may be reduced considerably from the dimensioned value, for example, if the filters for drying air are blocked. In this case, the web starts to contact the nozzle face. It has been noticed that the sharp edges plane material out of the face of, e.g., a pulp web, in which case both the quality of the finished product is deteriorated and rubbish remains in the dryer.
Moreover, the rubbish remaining in the dryer disturbs the threading of the pulp web. In this regard, the formation of a "cigar" is spoken of, for the material detached out of the face of the pulp web by planing forms a roll resembling the structure of a cigar.
In the type of nozzle-blow-boxes employed in pulp dryers in which the web runs above the nozzle and carrier faces of the boxes, the function of the air blowings is both to transfer heat from the blown air to the web and to support the web free of contact. In view of the runnability of the web, it is preferable to blow part of the air in a direction parallel to the plane of the nozzle such that the web is stabilized at a distance of about 3 mm to about 6 mm from the carrier face. However, in such a case, in the prior art nozzle-blow-boxes, the velocity of the exhaust air in the space between the web and the nozzle becomes high. This results in deterioration of the transfer of heat and .
:~ ' ~
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20q2304 in extra and/or excessive pressure losses. The detrimental effect of the high velocity of the exhaust air can be reduced by making the nozzles sufficiently narrow, but then the number of the nozzles becomes so high that the cost of manufacture of the dryer is increased substantially.
The present invention is directed towards the further development of the prior art nozzle-blow-boxes described in the afore-mentioned patents while eliminating the drawbacks present therein.
The present invention is also directed towards the provision of a new and improved method and nozzle-blow-box construction by whose means it is possible to avoid the drawbacks discussed above and to improve the transfer of heat from the drying air to the airborne web to be dried. This improvement of the transfer of heat can be utilized most efficiently in the form of a smaller size being required for the dryer. In this manner, the cost of construction, e.g., of a pulp dryer, and the cost of the machine hall in which the dryer will operate can be lowered decisively, particularly the length of the building required to house the pulp dryer.
The present invention is also directed towards reducing the effect of the deterioration of the transfer of heat by the lateral flow while the run of the web is stabilized by means of the lateral flow.
In the method in accordance with one aspect of the present invention, an air flow velocity parallel to the plane of the web to be dried and air-supported in connection with the nozzle-carrier face is initially kept substantially invariable in order to improve the transfer of heat in comparison with a plane carrier face. In this manner, the air flow velocity is lowered in the lateral areas of the carrier face by employing lateral areas B
2092~4 of the nozzle-carrier face that become lower in the air-flow direction.
Accordingly, in one aspect of the present invention, there is provided a method for air-drying material webs in a dryer, comprising:
arranging nozzle-blow-boxes on one side of the web such that a top side of said nozzle-blow-boxes forms said carrier face, arranging a groove space in a middle portion of said carrier face and extending in a direction transverse to a running direction of the web, directing first air blowings to a web to be dried through said first nozzle means in said carrier face in a direction substantially perpendicular to the web, directing second air blowings to the web crosswise through said second nozzle means in a direction substantially parallel to the web, said first and second air blowings transferring heat to the web and supporting the web by air such that a run of the web through a dryer is stabilized, maintaining an initial velocity of said second air blowings to be substantially constant to improve the transfer of heat in comparison with said carrier face, and arranging lateral areas of said plane carrier face to become lower in the flow direction of said second air blowings to lower the velocity of said second air blowings in said lateral areas of said carrier face, and increase the cross-sectional flow area between the web and said carrier face in said lateral areas of said carrier face such that the time of effect of said second air blowings upon a lower face of the web is increased.
The nozzle-blow-box in accordance with one aspect of the invention includes nozzle-carrier face portions having extensions which comprise lateral carrier-face portions 2092G0~
placed further apart from the material web to be supported. The velocities of the support and stabilization air flows in the area of the carrier-face portions are lower as compared with the velocity prevailing in connectlon with the planar nozzle-carrier-face portions. The nozzle-carrier face is provided with nozzle perforations through which additional blowings can be directed from the nozzle-blow-box in a direction substantially perpendicular to the plane of the material web to be supported.
Accordingly, in a second aspect of this invention, there is provided a nozzle-blow-box of an air dryer for directing air blowings to a material web to be dried, the air blowings producing a transfer of heat from the drying air to the web and contact-free air support and stabilization of a run of the web through the air dryer, said nozzle-blow-box comprising:
a box part having a nozzle-carrier face arranged to face the web, a substantially V-section groove arranged in a middle portion of said nozzle-carrier face in a direction transverse to a running direction of the web, said groove being open toward the web and having a series of nozzle holes arranged in opposite walls for directing support and stabilization air blowings to the web, said support and stabilization air blowings being directed crosswise and in opposite directions in relation to each other, said nozzle-carrier face comprising planar nozzle-carrier faces arranged on both sides of said groove and in the same plane with each other, said planar nozzle-carrier faces having extensions comprising lateralcarrier face portions arranged further apart from the web, the velocity of said support and stabilization air blowings being lower in proximity to said lateral carrier-face portions as compared with the velocity of said support and stabilization air blowings prevailing in ~3 20q200~
proximity to said planar nozzle-carrier-face portions, said nozzle-carrier face further comprising nozzle perforations through which additional air blowings are directed from said nozzle-blow-box in a direction substantially perpendicular to the plane of the web.
The effect of the deterioration of the transfer of heat by the lateral flow has been minimized in the present invention by lowering the lateral portions of the nozzle to a level lower than the planar middle portion such that the velocity of the lateral flow is lowered. Moreover, the lateral flows are preferably directed so that they do not directly collide with the air jets being blown directly on the plane face or on the lowered lateral portions.
The lowering of the lateral areas of the nozzle-carrier-face portions in accordance with the invention is based on the idea that a high flow velocity of the exhaust air between the web and the nozzle-carrier face causes a deterioration in the coefficient of heat transfer. Thus, the lower the space between the web and the nozzle-carrier face, the higher the velocity of the exhaust air becomes.
The velocity of the exhaust air is increased in both directions from the center line of the nozzles toward the edges when more air is introduced. When the lateral areas of the nozzle-carrier-face are lowered in accordance with the present invention, the flow velocity in this area is lowered.
' 2~9200~ ~
The nozzle-blow-box in accordance with the invention is a combination of a nozzle with positive/negative pressure in which the magnitude of the lateral flow that produce- the negative pressure is selected appropriately in relation to the amount of air in the direct blowing.
It is an important feature of the hole-no~zle field in the carrier face in accordance with the invention that the coefficient of heat transfer is not substantially dependent on the distance given the relatively small nozzle-to-web distances with which the nozzles of the present invention operates. This feature is achieved, provided that the exhaust air does not disturb the air jets blown out of the nozzle holes to a significant extent. However, it is well known that, when there are several rows of nozzle holes, one row arranged after the other, the air discharged out of the nozzles generally passes toward the edges in the space between the nozzle and the web.
Thus, the higher the flow velocity of the discharged air, the greater the disturbance caused to the air jets blown out of the holes and the greater the deterioration of the coefficient of heat transfer.
In a preferred embodiment of the nozzle-blow-box in accordance with the invention, air jets are directed from the walls of a V-section groove placed in the middle of the nozzle face in a direction crosswise in relation to one another at continuous rounding points between the plane carrier face placed at each side of the walls of the V-section groove. The air jets are tangential to the rounding points so that they turn and become parallel to the plane portions of the carrier face as a result of the Coanda effect. In accordance with the Bernoulli principle, a zone of negative pressure is formed between the web and the carrier faces which stabilizes the web at a certain distance from the carrier face. The distance is generally from ~5 2~92~0~
~ut 3 mm to about 6 mm.
In addition, on the horizontal part of the carrier face in the present invention, attempts are made to avoid direct collisions between the jets of direct blowing and the air jets that flow in the lateral direction.
According to the present invention, the lateral areas of the nozzle-carrier face of the nozzle-blow-box have been lowered so that the velocity of the lateral flow is lowered as the cross-sectional flow area becomes larger. In this manner, the heat-transfer effect of the blow jets coming from the holes of direct blowing placed in the lowered inclined and~o- ~traight nozzle-carrier-face portion is improved.
The nozzle-blow-box in accordance with the invention is suitable for use for drying a web both in on~--ized/two-sided drying, in the case of low-grammage webs ( < 200 g/sq. m), and both underneath and above the web. In the ca~e of heavy webs, such as pulp webs, the nozzle-blow-boxes in accordance with the invention are preferably suitable tor lower nozzles together with direct-blow boxes that operate ~b upper nozzles, or alone as lower nozzle boxes in one-sided drying.
A further advantage is achieved by means of the geometry of the blow-carrier faces of the nozzle-blow-boxes in accordance with the invention. This advantage is that a smooth blow face with no sharp edges is obtained as the air of the lateral flow is introduced out of the central V-section groove while guided by rounded faces. If the web contacts the nozzle face, there are no sharp edges which will tear the web and cause a deterioration in the quality of the finished product and rubbish to remain in the dryer which will disturb the threading of the pulp web.
The transfer of heat to the web can be improved by about 5 to about 10% by means of the present invention, This improvement can be ; -~iately taken and put to use in the form of a reduced . ~ . " . ~ .
~ :
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.
209200~
size of the dryer whlch substantially lowers the cost of the investment of the dryer and the machine hall. Also, this improvement indirectly reduces the number of production interruptions and improves the operating time ratio of the dryer. The advantages mentioned above are particularly important in the case of large and complicated pulp dryers. The nature of the improvements has been quantified by measurements that have been carried out and that will be described in more detail later.
In a nozzle-blow-box in accordance with the invention, a V-section groove is used in the middle of its carrier face. Blowings parallel to the carrier face are applied crosswise through the groove. By means of this arrangement, a rigid mechanical construction is obtained in addition to a favorable blow/heat-transfer technique. The V-section groove rigidifies the nozzle carrier-face efficiently without any other rigidifying structures which would otherwise be necessary.
It is a minor drawback of the blow face of the blow box in accordance with the invention that it is somewhat more difficult to manufacture than a uniform plane face.
However, this drawback can be solved by means of development of the manufacturing technology.
In an additional aspect, the present invention provides a pulp dryer for drying material webs, comprising:
nozzle-blow-boxes arranged at horizontal distances from one another to form spaces therebetween, said nozzle-blow boxes being placed at a distance from a material web to form treatment gaps and directing air at least in a perpendicular direction to the web to support, dry and stabilize the webj the air being removed from said treatment gaps via said spaces, said nozzle-blow-boxes being arranged in the running direction of the web one after B
.
another in a horizontal plane such that rows of said nozzle-blow-boxes are formed in the dryer, a hood through which the web to be dried runs through the dryer supported by air, the web being arranged to run over said rows of said nozzle-blow-boxes in horizontal backward and forward runs arranged in a vertical orientation in the dryer, and reversing rolls for reversing the running direction of the web between said horizontal runs.
The following drawings are illustrative of embodiments of the invention and are not meant to limit the scope of the invention as encompassed by the claims.
Figure 1 is a schematic vertical sectional view in the machine direction of a pulp dryer in which the method and of a set of nozzle-blow-boxes in accordance with the invention are utilized.
Figure 2 is an axonometric view of the modular construction of a pulp dryer in which the method and of a set of nozzle-blow-20~21D0~ ~
es in accordance with the invention are utilized.
Figure 3 is a schematic vertical sectional view in the machine direction of a set of nozzle-blow-boxes in accordance with the invention and of a set of boxes of direct blowing placed above the set of boxes.
Figure 4 is an axonometric illustration of a nozzle-blow-box in accordance with the invention and of the principle of its blowings.
Figure 5 is an axonometric view of the construction of an upper direct-blow box in accordance with the invention and used in a method of the present invention.
Figure 6 shows an embodiment of a carrier face of a nozzle-blow-box in accordance with the invention and of the blow nozzles of the carrier face in more detail, together with important dimensioning parameters.
Figures 7A, 7B, 7C, 7D, and 7E illustrate different variations of different embodiments and dimensions of bevel and step formations of the nozzle-carrier laces ot ~ nozzle-blow-box in accordance with the invention.
Figure 8A shows a nozzle-blow-box as shown in Figs. 4 or 5, viewed from a side of the nozzle-carrier face.
Figure 8B is an enlarged schematic vertb:~l sectional view in the machine direction of a preferred geometry and dimensioning of the V-section groove of the nozzle.
Figure 9 illustrates different relative coefficients of heat transfer of the embodiments illustrated in Figs. 7A to 7E as a function of the distance of the ~eL at a first air-blow velocity.
Figure 10 illustrates the corresponding measurement results in a manner corresponding to Fig. 9, at a second, higher air-blow velocity.
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.;
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.' 209200~
.
~ ntion are utilized. The basic principle of the embodiment of Fig. 2 is, e.g., similar to that illustrated in Fig. 1. The dryer-blower module comprises blower towers 21 and blowers, which are provided with blade wheels 22. The module construction includes heating radiators 24 through which the blow air is passed into the gap between the upper nozzles and the lower nozzles, i.e. into web gap 25. Further, the module construction includes air filters 26. At the operating side of the blower module, a ten~;ng bridge 28 is arranged, in connection with which there are servicing gates 27 for the blower motors and servicing doors 29 for the blower modules. Fig. 2 shows the circulation of the drying air as illustrated by the arrows, and also the nozzle-blow-boxes 30,40 in accordance with the invention and the web gaps 25 between them.
With respect to the above description of Figs. 1 and 2, it is to be emphasized that only one field of application of the method and of the set of nozzle-blow-boxes 30,40 in accordance with the invention are described therein. The method and the set of nozzle-blow-boxes 30,40 in accordance with the invention can also be applied in numerous other environments and also in devices other than pulp dryers, for example in board and paper-web dryers. However, pulp dryers are the most advantageous and primary field of application of the invention wherein several different and distinct advantages of the invention are most appropriately and completely utilized.
Fig. 3 is a schematic illustration ol a s~t of nozzle-blow-boxes 30 in accordance with the invention and ~f an opposite set of boxes 40 of direct blowing. In the followin~J description, the shorter name "lower box" will be used for the no~zle-blow-boxes 30, because they are preferably placed undern~th the horizontally running web W. Free spaces 30a are arranged between the lower boxes 30 and, in a corresponding way, tree spaces 40a .
~: :
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2~92~0~
are arranged between the direct-blow boxes 40. The blow air is , ssed through spaces 30a and 40a further through the heating radiators 24 shown in Fig. 2 and is carried or propelled by the blower 22 back to the blow boxes.
As shown in Fig. 3, the web W to be dried, typically a pulp web, runs as a horizontal run through the web gap 25. The web gap 25 is defined as the distance between the lower boxes 30 as a lower point and the direct-blow boxes 40 as an upper point. The lower boxes 30 are preferably uniformly spaced in one horizontal plane. The direct blow-boxes 40 are also uniformly spaced in a horizontal plane. The web W, which is usually heavy (the weight of a wet pulp web may be up to about 2000 g/sq.m), is supported on the blow boxes 30 by means of the blowings B2 and B3.
Blowings B1 are applied to the web W through nozzle holes 42 placed in the horizontal lower walls of the direct-blow boxes 40 in a direction perpendicular to the plane of the web W. The web W is dried from above by means of these blowings B1.
Figs. 4, 6, and 8A and 8B illustrate the construction of the lower boxes 30 in greater detail. A transverse groove 32 is arranged in the middle portion of a carrier face 31 of the lower boxes. Groove 32 passes across the width of the web W and is opened toward the web W in preferably a V-section. The opening angle of the V-section groove 32 is denoted with a. Angle a is generally from about 50~ to about 90~, preferably a is from about 60- to about 80'. The inclined walls of the V-section groove 32 are preferably plane and arranged to turn and join a horizontal plane portion 34 of the carrier face at an angle k by means of rounded portions 31b having a curve radius R. As shown in Fig.
6, between the angles a and _, there is a relationship a + 2b =
180-.
Both of the inclined plane faces of the V-section groove 32 .
have rows of blow holes 33. These blow holes 33 are arranged and 2()~ OO'1 d ~cted so that the air jets ~ are blown through the blow holes 33 in a direction tangential to the :ounded portions 31b between the plane faces. The rounded portions turn the air jets B3 by the Coanda effect onto the plane portions 34 of the carrier face 31 and make the jets parallel to the plane portions. The blow holes 33 are placed in the opposite sides of the v-section groove 32 and arranged in a staggered arrangement in relation to one another (Fig. 8) such that the blowings B3 are interlocked with one another crosswise in opposite directions. Thus, one set of the blowings B3 is directed parallel to the running direction of the web W and to its plane, whereas the other set of the blowings is directed parallel to the plane of the web W but in a direction opposite to the running direction of the web W.
In accordance with the Bernoulli principle, the blowings B3 induce a zone of negative pressure between the web W and the carrier face 31. This zone stabilizes the web W at a certain --~
distance H from the carrier face 31. The distance H is preferably from about 3 mm to about 6 mm, in which case the air drying of the web W is most efficient.
Lowered lateral portions 35 are placed in both of the lateral areas of the carrier face 31 over its length L in the direction of the web. The height of these lowered lateral portions 35 is lower in relation to the web W than the height of the middle-plane portions 34 of the carrier face 31. According to Fig. 6, lateral portions 35 are inclined plane bevel parts whose distance in relation to the plane parts 34 at the edges of the nozzle box 30 is denoted with h2.
In the nozzle-blow-box in accordance with the invention, the air velocity is first substantially invariable in connection with the plane carrier-face portions 31 in the web W treatment gap 25 underneath the web W. The air velocity is lowered in connection with the carrier-face portions 35,35b,35d,35e which are stepwise . . :~
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2092ao4 continuously lowered in height when moving towards the edges of the box 30 and towards spaces 30a in the treatment gap 25. In this manner, the transfer of heat can be intenblfied considerably, as will be described later in connection with the test results illustrated in Figs. 9 and lO. The intensification of the transfer of heat comes largely from th-- ~act that the air-flow velocity parallel to the plane of the web ~ is lowered considerably on the lowered carrier-face portions 35,35b,35d,35e. 5 This intensifies above all the heat transfer ot the direct blowings B2.
In a pulp dryer in accordar7~ ~ith the invention, the lower box 30 and the direct-blow box 40 as shown in Figs. 4 and 5 are placed one above the other and one facing the other so that faces 41 and 31 of the boxes 40,30, respectively, are substantially parallel to one another and generally horizontal. Rounded portions 43a may be arranged at the edges of the faces 41 of the -~
direct-blow boxes 40. Corresponding rounded portions 31a maybe -arranged at the edges of the carrier faces 31 of the lower boxes 30.
The opposite faces 31 and 41 on the lower box 30 and on the direct-blow box 40 are provided with nozzle perforations 42,36, respectively. A preferred distribution of the perforations 36 on the blow box 30 is illustrated in Fig. 8. Perpendicular blowings Bl,Bz are directed against the web W through the perforations 36,42 and the drying of the web W is promoted by means of these perpendicular blowings. The direct blowings B2 will have a longer time of effect on the lower face of the web W as a result of the decrease in the air-flow velocity on the carrier-face portions 35 because of an increased cross-sectional flow area.
Fig. 8B is a schematic illustration of a preferred embodiment of the geometry and a dimensioning example of the V-section groove 32 described above. The geometry shown in Fig. 8B
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20g20~
!
i ~ymmetric in relation to a transverse vertical center plane K-K. It is important in the design of the V-section groove 32 that the air jets F1 and F2 which are blown from the opposite sides if the groove 32 can be directed tangential to the rounded portions 31b connected with the edges of the groove 32. These air jets will, by the Coanda effect, turn and become parallel to the carrier face 34. The area between the groove 33 and the carrier face 34 must be specifically rounded in such a way that the air starts following the carrier face 34.
Figs. 7A-7E show alternative embodiments of the carrier face of the blow box 30. The nozzle box 30A as shown in Fig. 7A
comprises a carrier face 31 in which plane portions 34 are arranged at both sides of the V-section groove 32. Plane inclined bevel portions 35 are arranged after the plane portions 34 in the air-flow direction.
Fig. 7B shows a particularly advantageous blow box 30B, in which plane portions 34b of the carrier face are arranged at both sides of the V-section groove 32. ~;-ep portions 37 are arranged after the plane portions 34b in t~e ~ir-flow direction. Step portions 37 are perpendicular both to the first plane portions 34b of the carrier face and to plane portions 35b of the carrier face that follow after the step portion 37 in the air-flow direction. The initial parts 34b of the carrier face 31 are preferably parallel to one another and in the same horizontal plane. In a corresponding way, the lateral portions of the carrier face 31 are preferably parallel to one another and in the same horizontal plane.
Fig. 7B also shows a preferred dimensioning example of the nozzle box 30B. According to Fig. 7B, the height h2 of the step portion 37 is about lO mm. Generally, the height of the step portion h2 may vary from about 7 mm to about 15 mm.
In Fig. 7C, a nozzle box 30C is illustrated as a reference, ~ .. , : :, ~ , w~ ~h box has a fully plane carrier face 31c. Properly speaking, this nozzle box 30C is not a preferred embodiment in accordance with the present invention, and it is illustrated in this connection for the sake of reference only. The results of a S comparison including this reference nozzle box are illustrated in Figs. 9 and 10, which will be described in more detail later.
Fig. 7D illustrates a blow box 30D in accordance with the invention, which box has relatively long plane carrier-face portions 34d and relatively short and steep, inclined lateral portions 35d. In Fig. 7D, a preferred dimensioning example is also provided.
In Fig. 7E, an alternative modification of the blow box as shown in Fig. 7B is illustrated. Blow box 30E has relatively long plane carrier-face portions 34e and step portions 37 which are followed by relatively short carrier-face portions 35e in the air-flow direction. Fig. 7E also shows an example of the ;
construction of blow box 3OE.
Fig. 8A shows the relative locations and staggering of the nozzle holes 33 in the V-section groove 32 so that the blowings B3 being blown in opposite directions are blowr crosswise. The perforations 36 in the nozzle-carrier face 31 are placed in four lines or rows, one line after the other, as stagyered in such a way that the blowings B2 and B3 neither meet ea~ other nor disturb each other. The mutual spacing of the rlozzle holes 33 is generally from about 20 mm to about ~,o mm. In a corresponding way, the mutual spacing of the nozz~- holes 36 in the transverse direction and in the machine direction is usually from about 40 mm to about 100 mm.
Further, as to the dimensioning of the blow boxes shown in Figs. 6 and 7, it can be stated as follows, with reference to the denotations in Fig. 6. The angle a of the V-section groove 32 in the middle of the carrier face is generally from about 50~ to c It 90-, in which case the angle k of the Coanda faces 31b is from about 45~ to about 65~. The height h1 of the V-section groove 32 is optimally obtained from the equation h1 = (2 - 5) x ~ wherein ~ is the diameter of the nozzle holes 33 in the walls of the V-section groove 32. The diameter ~ of the nozzle holes 33 is selected relative to the diameter of the direct-blow nozzles 36 in the carrier face so that the air quantity in the carrier-blowings B3 blown through the nozzle holes 33 is about 30% to about 60%, preferably 35~ to about 45%, of the overall air quantity of the blowings B2 and ~.
The length L1 ~f the bevelled or step-formed lateral portions 35,35b,35d,35e in the carrier face 31 is selected according to the equation L1= (0.1 - 0.3) x L, preferably L1 =
(0.2 - 0.25) x L, wherein L is the total length of the blow box 30 in the machine direction. Generally, length L is from about 300 mm to about 500 mm. The difference in height hz of the bevelled portions 35,35d or of the step-formed portions 35b and 35e is selected from about 7 mm to about 15 mm, preferably h2 is about 10 mm.
Figs. 9 and 10 graphically illustrate test results obtained with nozzles as shown in Figs. 7A-7E. In Figs. 9 and 10, the vertical axis represents the relative heat transfer coefficient ~R and the horizontal axis represents the distance of the web W
from the carrier face 31, expressly from its plane portion 34.
In Figs. 7A-7E, the letter symbol after the numeral "7"
corresponds to the curves A-E in Figs. 9 and 10. ~-Of the nozzle arrangement described above, versions as shown in Figs. 7A-7E were made and the transfer of heat was examined in a static test device by blowing hot air against a plane metal face. The efficiency of the transfer of heat w~s obtained by measuring the heating rate of the plate by mearls of temperature-measurement detectors inlaid in the plate.
.~. .
'~
. ~
209~Jo4 In Figs. 9 and 10, the measured relative heat-transfer coefficients ~R are illustrated as a function of the distance H
between the web and the carrier face 31 of the nozzle box at two different blow velocities. According to the results, a lowering h1 of the lateral portions 35,35b,35d,35e provides an increase in the range of about 5% to about 10% in the coefficient of heat transfer as compared with a plane carrier face (Fig. 7C, carrier face 31c), when the distance H equals the normal airborne distance of a pulp web W (between about 3 mm and 6 mm). In contrast, at larger distances H, a lowering or decrease of the lateral portions 35 does not give any corresponding advantage.
The increase was highest in the case of the nozzles at which the lateral portions 35,35b of the carrier face 31 had been lowered most, on the average (Figs. 7A and 7B). The measurement results provided in Fig. 9 were obtained with a blow velocity of w~h is -about 26 m/s of the blowings B2 and B3. The results given in Fig. 10 were obtained with a corresponding blow velocity of w~h is about 34 m/s, while the temperature T~h of the blow air was about 150~C. As shown in Figs. 9 and 10, there are substantially large differences in the relative heat-transfer coefficient ~R
exactly at the optimal airborne web W distances, i.e. when H is between 3 mm and 6 mm.
The simulation and measurement method employed in the measurements of Figs. 9 and 10 has been described in more detail in a paper by P. Heikkila and I. Jokioinen, "Airfoil Dryer Heat Transfer", published in The Helsinki Symposium on Alternate Methods of Pulp and Paper Drying in Helsinki, June 4-7 (1991).
Based on the measurements described above, the most advantageous embodiment of the invention is, according to the present-day opinion and on the basis of the available measurement results, the blow-nozzle box 30A as shown in Fig. 7A. According to the measurement results of Figs. 9 and 10, a carrier face 2~200 1 ,35b with a steep step formation ~7, as sho~n in Fig. 7B, is optimal in view of the transfer of heat. However, a nozzle-blow-box 30A as shown in Fig. 7A, whic~ 5 provided with continuously lowering ramp-formed lateral portions 35 of the carrier face, is preferable in an overall consideration because the risk of formation of a "cigar" is lower for this nozzle-blow-box 30A as the geometry of the blow face does not include sharp angles.
Thus, according to a present-day estimate, a nozzle-blow-box 30A 5 as shown in Fig. 7A (also in respect of its dimensions) is the most preferable embodiment of the invention in a situation in which the distance, e.g., of a pulp web W from the horizo~tal portion 34 of the carrier face 31 is about 5 mm.
The examples provided above are not meant to be exclusive.
Many other variations of the present invention would be obvious to those skilled in the art, and are contemplated to be within the scope of the appended claims.
. - ~
Claims (20)
1. A method for air-drying material webs in a dryer, comprising:
arranging nozzle-blow-boxes on one side of the web such that a top side of said nozzle-blow-boxes forms said carrier face, arranging a groove space in a middle portion of said carrier face and extending in a direction transverse to a running direction of the web, directing first air blowings to a web to be dried through said first nozzle means in said carrier face in a direction substantially perpendicular to the web, directing second air blowings to the web crosswise through said second nozzle means in a direction substantially parallel to the web, said first and second air blowings transferring heat to the web and supporting the web by air such that a run of the web through a dryer is stabilized, maintaining an initial velocity of said second air blowings to be substantially constant to improve the transfer of heat in comparison with said carrier face, and arranging lateral areas of said plane carrier face to become lower in the flow direction of said second air blowings to lower the velocity of said second air blowings in said lateral areas of said carrier face, and increase the cross-sectional flow area between the web and said carrier face in said lateral areas of said carrier face such that the time of effect of said second air blowings upon a lower face of the web is increased.
arranging nozzle-blow-boxes on one side of the web such that a top side of said nozzle-blow-boxes forms said carrier face, arranging a groove space in a middle portion of said carrier face and extending in a direction transverse to a running direction of the web, directing first air blowings to a web to be dried through said first nozzle means in said carrier face in a direction substantially perpendicular to the web, directing second air blowings to the web crosswise through said second nozzle means in a direction substantially parallel to the web, said first and second air blowings transferring heat to the web and supporting the web by air such that a run of the web through a dryer is stabilized, maintaining an initial velocity of said second air blowings to be substantially constant to improve the transfer of heat in comparison with said carrier face, and arranging lateral areas of said plane carrier face to become lower in the flow direction of said second air blowings to lower the velocity of said second air blowings in said lateral areas of said carrier face, and increase the cross-sectional flow area between the web and said carrier face in said lateral areas of said carrier face such that the time of effect of said second air blowings upon a lower face of the web is increased.
2. The method of claim 1, further comprising optimizing the transfer of heat from said first and second air blowings to the web by means of said lateral areas of said carrier face and regulating the height at which the web runs and is supported in relation to said carrier face by means of said lateral areas of said carrier face.
3. The method of claim 1, wherein said second nozzle means comprises nozzle openings arranged in said groove in said carrier face, said second air blowings being directed crosswise from said nozzle openings in opposite directions and substantially tangential to curved guide faces arranged in said carrier face, said second air blowings being turned by the Coanda effect to become parallel to plane initial parts of said carrier face and a plane of the web.
4. The method of claim 1, further comprising providing that the blow-air quantity of said second air blowings is between about 30% to about 60% of the overall blow-air quantity of said nozzle-blow-boxes.
5. The method of claim 4, wherein the blow-air quantity of said second air blowings is between about 35%
to about 45% of the overall blow-air quantity of said nozzle-blow-boxes.
to about 45% of the overall blow-air quantity of said nozzle-blow-boxes.
6. The method of claim 1, further comprising decreasing the velocity of said second air blowings in said lateral areas of said carrier face of said nozzle box over a length L1, parallel to the run of the web, length L1 being computed from the equation L1 = L x (0.1 - 0.3) wherein L is the overall length of said carrier face of said nozzle box selected from about 300 mm to about 500 mm.
7. The method of claim 7, wherein the length L, parallel to the run of the web is computed from the equation L1 = L x (0.2 - 0.25).
8. The method of claim 1, further comprising arranging a plurality of nozzle boxes having spaces formed therebetween, and removing air out of a drying and support gap defined between said carrier face and the web through said spaces.
9. The method of claim 1, further comprising arranging direct-blow boxes on a side of the web opposite said nozzle-blow-boxes, and directing third air blowings out of said direct-blow boxes in a direction substantially perpendicular to the plane of the web such that both sides of the web are dried.
10. A nozzle-blow-box of an air dryer for directing air blowings to a material web to be dried, the air blowings producing a transfer of heat from the drying air to the web and contact-free air support and stabilization of a run of the web through the air dryer, said nozzle-blow-box comprising:
a box part having a nozzle-carrier face arranged to face the web, a substantially V-section groove arranged in a middle portion of said nozzle-carrier face in a direction transverse to a running direction of the web, said groove being open toward the web and having a series of nozzle holes arranged in opposite walls for directing support and stabilization air blowings to the web, said support and stabilization air blowings being directed crosswise and in opposite directions in relation to each other, said nozzle-carrier face comprising planar nozzle carrier faces arranged on both sides of said groove and in the same plane with each other, said planar nozzle-carrier faces having extensions comprising lateral carrier face portions arranged further apart from the web, the velocity of said support and stabilization air blowings being lower in proximity to said lateral carrier-face portions as compared with the velocity of said support and stabilization air blowings prevailing in proximity to said planar nozzle-carrier-face portions, said nozzle-carrier face further comprising nozzle perforations through which additional air blowings are directed from said nozzle-blow-box in a direction substantially perpendicular to the plane of the web.
a box part having a nozzle-carrier face arranged to face the web, a substantially V-section groove arranged in a middle portion of said nozzle-carrier face in a direction transverse to a running direction of the web, said groove being open toward the web and having a series of nozzle holes arranged in opposite walls for directing support and stabilization air blowings to the web, said support and stabilization air blowings being directed crosswise and in opposite directions in relation to each other, said nozzle-carrier face comprising planar nozzle carrier faces arranged on both sides of said groove and in the same plane with each other, said planar nozzle-carrier faces having extensions comprising lateral carrier face portions arranged further apart from the web, the velocity of said support and stabilization air blowings being lower in proximity to said lateral carrier-face portions as compared with the velocity of said support and stabilization air blowings prevailing in proximity to said planar nozzle-carrier-face portions, said nozzle-carrier face further comprising nozzle perforations through which additional air blowings are directed from said nozzle-blow-box in a direction substantially perpendicular to the plane of the web.
11. The nozzle-blow-box of claim 10, wherein said groove has extensions on said opposite walls of said groove, said extensions comprising curved Coanda guide faces which extend continuously and connect to said planar nozzle-carrier-face portions, said series of nozzle holes being arranged to direct said support and stabilization air blowings in a direction substantially tangential to said curved Coanda guide face on an opposing wall.
12. The nozzle-blow-box of claim 10, wherein an angle between said opposite walls of said groove is from about 50° to about 90°, and the depth h1 of said groove is computed from the equation h1 = (2 - 5) x ~, wherein ~
is the diameter of said series of nozzle holes in said walls of said groove.
is the diameter of said series of nozzle holes in said walls of said groove.
13. The nozzle-blow-box of claim 11, wherein the length L1 of said lateral carrier face portions in the running direction of the web is computed from the equation L1 = (0.1 - 0.3) x L, wherein L is the overall length of said nozzle-blow-box in the running direction of the web and is from about 300 mm to about 500 mm, and the maximum difference in height of said lateral carrier face portions, as compared with said planar nozzle-carrier-face portions, is from about 7 mm to about 15 mm.
14. The nozzle-blow-box of claim 13, wherein the length L1 of said lateral carrier face portions is computed from the equation L1 = (0.2 - 0.25) x L, and the maximum difference in height of said lateral carrier face portions, as compared with said planar nozzle-carrier-face portions, is about 10 mm.
15. The nozzle-blow-box of claim 10, wherein said series of nozzle holes are arranged in an alternating staggered arrangement and substantially uniformly spaced in said groove, the spacing of said series of nozzle holes being selected from about 20 mm to about 50 mm, said nozzle perforations being arranged in a staggered arrangement in relation to said series of nozzle holes, between 3 and 5 transverse rows in the running direction of the web and substantially uniformly spaced both in the running direction of the web and in the transverse direction, the spacing of said nozzle perforations being selected from about 40 mm to about 100 mm.
16. The nozzle-blow-box of claim 10 wherein said lateral carrier face portions are ramp-shaped.
17. The nozzle-blow-box of claim 10 wherein said lateral carrier face portions are stepwise.
18. A pulp dryer for drying material webs, comprising:
nozzle-blow-boxes arranged at horizontal distances from one another to form spaces therebetween, said nozzle-blow boxes being placed at a distance from a material web to form treatment gaps and directing air at least in a perpendicular direction to the web to support, dry and stabilize the web, the air being removed from said treatment gaps via said spaces, said nozzle-blow-boxes being arranged in the running direction of the web one after another in a horizontal plane such that rows of said nozzle-blow-boxes are formed in the dryer, a hood through which the web to be dried runs through the dryer supported by air, the web being arranged to run over said rows of said nozzle-blow-boxes in horizontal backward and forward runs arranged in a vertical orientation in the dryer, and reversing rolls for reversing the running direction of the web between said horizontal runs.
nozzle-blow-boxes arranged at horizontal distances from one another to form spaces therebetween, said nozzle-blow boxes being placed at a distance from a material web to form treatment gaps and directing air at least in a perpendicular direction to the web to support, dry and stabilize the web, the air being removed from said treatment gaps via said spaces, said nozzle-blow-boxes being arranged in the running direction of the web one after another in a horizontal plane such that rows of said nozzle-blow-boxes are formed in the dryer, a hood through which the web to be dried runs through the dryer supported by air, the web being arranged to run over said rows of said nozzle-blow-boxes in horizontal backward and forward runs arranged in a vertical orientation in the dryer, and reversing rolls for reversing the running direction of the web between said horizontal runs.
19. The pulp dryer of claim 18, further comprising direct-blow boxes arranged opposite said nozzle-blow-boxes and above the web, said direct-blow boxes directing blowings in a direction substantially perpendicular to the web through nozzle perforations arranged in a planar face of said direct-blow boxes, said direct-blow boxes being arranged to form intermediate spaces therebetween through which said air blowings from said direct-blow boxes flow.
20. The pulp dryer of claim 19, wherein the length of said nozzle-blow-boxes and said direct-blow boxes is substantially equal, and said nozzle-blow-boxes are arranged in a uniformly spaced arrangement in the dryer to face said direct-blow boxes.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI921193 | 1992-03-19 | ||
| FI921193A FI92421B (en) | 1992-03-19 | 1992-03-19 | Method for air drying air webs, air dryer nozzle-blow box and pulp dryer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2092004A1 CA2092004A1 (en) | 1993-09-20 |
| CA2092004C true CA2092004C (en) | 1998-05-19 |
Family
ID=8534948
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002092004A Expired - Lifetime CA2092004C (en) | 1992-03-19 | 1993-03-18 | Method in contact-free air-drying of a material web as well as a nozzle-blow-box and a pulp dryer that make use of the method |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0561256B1 (en) |
| JP (1) | JP3305802B2 (en) |
| KR (1) | KR0172974B1 (en) |
| CN (1) | CN1031656C (en) |
| AT (1) | ATE203071T1 (en) |
| BR (1) | BR9301228A (en) |
| CA (1) | CA2092004C (en) |
| DE (1) | DE69330413T2 (en) |
| ES (1) | ES2159510T3 (en) |
| FI (1) | FI92421B (en) |
Families Citing this family (29)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4334473C2 (en) | 1993-10-11 | 1997-07-03 | Krieger Gmbh & Co Kg | Device for levitating a running web |
| US5590480A (en) * | 1994-12-06 | 1997-01-07 | W. R. Grace & Co.-Conn. | combination air bar and hole bar flotation dryer |
| SE505113E (en) * | 1995-10-31 | 2000-05-29 | Flaekt Ab | Blow box for use in a plant for drying a web of material |
| FI107549B (en) * | 1996-06-19 | 2001-08-31 | Metso Paper Inc | Method and apparatus in connection with blow-drying and / or blow-drying of paper web or the corresponding web-shaped material |
| US6119362A (en) * | 1996-06-19 | 2000-09-19 | Valmet Corporation | Arrangements for impingement drying and/or through-drying of a paper or material web |
| FI991497A0 (en) | 1999-06-30 | 1999-06-30 | Valmet Corp | Blow nozzle device for fan dryer with airborne web |
| CN100404990C (en) * | 2000-09-24 | 2008-07-23 | 3M创新有限公司 | Vapor collection method |
| FI110626B (en) | 2000-11-29 | 2003-02-28 | Metso Paper Inc | Method and apparatus for pre-drying fiber-based pulp tape |
| US6564473B2 (en) | 2001-10-22 | 2003-05-20 | The Procter & Gamble Company | High efficiency heat transfer using asymmetric impinging jet |
| DE10335581A1 (en) * | 2003-07-31 | 2005-02-24 | Voith Paper Patent Gmbh | Device for guiding and drying a running fibrous web |
| DE102004039988A1 (en) * | 2004-08-18 | 2006-02-23 | Voith Paper Patent Gmbh | Drying assembly for paper, carton or fibrous web is assembled from a series of modular units |
| CN1329586C (en) * | 2005-02-28 | 2007-08-01 | 陈建辉 | Hot air penetration type toilet paper machine and processing technology for hot air penetration drying toilet paper |
| FI119153B (en) * | 2006-11-14 | 2008-08-15 | Metso Paper Inc | End portion of an air dryer, air dryer, procedure in the end portion of an air dryer and use of a fan |
| SE530625C2 (en) * | 2006-12-06 | 2008-07-22 | Andritz Tech & Asset Man Gmbh | drying box |
| US8088255B2 (en) | 2008-04-18 | 2012-01-03 | Honeywell Asca Inc | Sheet stabilizer with dual inline machine direction air clamps and backsteps |
| SE535179C2 (en) * | 2010-07-14 | 2012-05-08 | Andritz Tech & Asset Man Gmbh | Ways of drying a pulp web and apparatus for drying such web |
| SE536108C2 (en) * | 2010-11-16 | 2013-05-07 | Andritz Tech & Asset Man Gmbh | Drying box comprising at least two zones for drying a cellulose pulp web |
| SE535634C2 (en) * | 2010-11-16 | 2012-10-23 | Andritz Tech & Asset Man Gmbh | Cellulose dryer having lower blow boxes and method of drying a web of cellulose pulp |
| DE102010052044A1 (en) * | 2010-11-23 | 2012-05-24 | Vits Technology Gmbh | Method and installation for impregnating and drying a continuous paper web |
| DE102011006698A1 (en) * | 2011-04-04 | 2012-10-04 | Voith Patent Gmbh | Method for drying a fibrous web in a drying device and drying device |
| FI124793B (en) * | 2011-07-06 | 2015-01-30 | Balance Engineering Oy | Method and plant for increasing the drying efficiency and energy efficiency in connection with the drying portion in cellulose production |
| CN102733244B (en) * | 2012-07-12 | 2015-04-01 | 山东太阳纸业股份有限公司 | Method and structure for preventing paper scraping in drying box of dissolving pulp machine |
| SE538854C2 (en) | 2014-01-09 | 2017-01-03 | Valmet Oy | Wheelchair for receiving and rolling up a paper web, which comes from a drying cylinder in a paper machine, to a roll, as well as a paper machine using a wheelchair |
| KR101983889B1 (en) * | 2014-05-15 | 2019-05-29 | 인스파이론 엔지니어링 프라이빗 리미티드 | A manifold |
| CN105066619A (en) * | 2015-07-23 | 2015-11-18 | 滁州金春无纺布有限公司 | Spinning drying equipment with automatic cloth penetrating and guiding function |
| CN107940922A (en) * | 2017-12-12 | 2018-04-20 | 深圳市共享能源技术有限公司 | Box heat pump drying case |
| EP3916150B1 (en) * | 2020-05-26 | 2025-07-09 | Valmet Technologies Oy | Nozzle system of a device for contact-free treatment of a running fiber web |
| FI130158B (en) * | 2022-02-04 | 2023-03-21 | Valmet Technologies Oy | Airborne pulp dryer with cross-directional blow boxes |
| CN114993017B (en) * | 2022-07-29 | 2022-10-14 | 佛山市新飞卫生材料有限公司 | Fine-dispersing airflow suspension oven for release paper |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1143474B (en) * | 1960-02-08 | 1963-02-14 | Artos Maschb Dr Ing Meier Wind | Nozzle housing arrangement for the treatment and non-contact guidance of railway goods |
| BE645430A (en) * | 1963-03-19 | |||
| SE393826B (en) * | 1974-05-29 | 1977-05-23 | Svenska Flaektfabriken Ab | ARRANGEMENTS THAT WHEN TRANSPORTING A BAN OR SHEET OF AIR-SUPPORTED MATERIAL, IN FRONT OF THE MATERIAL IN A FIXED STABLE FLOATING THROUGH ONE OR SEVERAL FLOORS OF A TREATMENT PLANT, ONE ... |
| SE450644B (en) * | 1985-01-16 | 1987-07-13 | Flaekt Ab | DEVICE USED FOR A DRYING OF A MATERIAL INTENDED FOR PLANT |
| DE3715533C2 (en) * | 1987-05-09 | 1997-07-17 | Krieger Gmbh & Co Kg | Device for levitating material webs |
| EP0298299B1 (en) * | 1987-07-07 | 1991-10-09 | Hilmar Vits | Device for the contactless guiding of webs |
-
1992
- 1992-03-19 FI FI921193A patent/FI92421B/en active
-
1993
- 1993-03-09 EP EP93103768A patent/EP0561256B1/en not_active Expired - Lifetime
- 1993-03-09 ES ES93103768T patent/ES2159510T3/en not_active Expired - Lifetime
- 1993-03-09 AT AT93103768T patent/ATE203071T1/en active
- 1993-03-09 DE DE69330413T patent/DE69330413T2/en not_active Expired - Lifetime
- 1993-03-18 BR BR9301228A patent/BR9301228A/en not_active IP Right Cessation
- 1993-03-18 KR KR1019930004138A patent/KR0172974B1/en not_active Expired - Lifetime
- 1993-03-18 CA CA002092004A patent/CA2092004C/en not_active Expired - Lifetime
- 1993-03-19 CN CN93104033A patent/CN1031656C/en not_active Expired - Lifetime
- 1993-03-19 JP JP08388893A patent/JP3305802B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
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| JP3305802B2 (en) | 2002-07-24 |
| CN1031656C (en) | 1996-04-24 |
| ATE203071T1 (en) | 2001-07-15 |
| JPH06248593A (en) | 1994-09-06 |
| CN1081485A (en) | 1994-02-02 |
| FI92421B (en) | 1994-07-29 |
| DE69330413T2 (en) | 2002-06-20 |
| EP0561256B1 (en) | 2001-07-11 |
| CA2092004A1 (en) | 1993-09-20 |
| KR930019930A (en) | 1993-10-19 |
| DE69330413D1 (en) | 2001-08-16 |
| KR0172974B1 (en) | 1999-03-30 |
| BR9301228A (en) | 1993-09-21 |
| FI921193A0 (en) | 1992-03-19 |
| FI921193L (en) | 1993-09-20 |
| ES2159510T3 (en) | 2001-10-16 |
| EP0561256A1 (en) | 1993-09-22 |
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