JP3305802B2 - Non-contact air drying method for web material, nozzle blowing box and pulp dryer by the method - Google Patents

Abstract

The invention concerns a method in air-drying of material webs, in particular of material webs of relatively high grammage, such as pulp webs. Also, the invention concerns a nozzle-blow-box and a pulp dryer that make use of the method. To the web (W) to be dried, from underneath the web, air blowings (B2) substantially perpendicular to the web and air blowings (B3) substantially parallel to the plane of the web (W) are applied. By means of these blowings (B2,B3), both heat is transferred to the web (W) and the web is supported by 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 plane carrier face (FIG. 7C; 31c), the air flow velocity parallel to the plane of the web (W) to be dried and air-supported in connection with the nozzle-carrier face (31) is initially (34) kept substantially invariable, whereupon the air flow velocity is lowered in the lateral areas (35;35b;35d;35e) of said carrier face (31) by employing lateral areas (35, 35b,35e) of the nozzle-carrier face (31) that become rampwise and/or stepwise lower in the air-flow direction. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for air-drying a web material having a relatively high basis weight, such as a pulp web, and more particularly to an air blow from below the web to be dried, substantially perpendicular to the web. Air blowing substantially parallel to the plane of the web, heat is sent to the web by both blowings, the web is supported by air without contact, and air drying of the web material stabilizes the running of the web through the dryer It is about the method.

Further, the present invention relates to a nozzle blowing box of an air dryer for blowing air to a web material to be dried, and more particularly, to a method of transferring heat from dry air to a web by blowing air, and a non-contact method. The running of the web is stabilized by air support, and the nozzle blowing box has a box portion provided with a nozzle supporting surface arranged opposite to the web, and the center of this supporting surface is in the running direction of the web. A V-shaped groove that intersects with the groove is provided, and the groove has a shape that is open toward the web, and a series of nozzle holes are provided in the opposing wall, and support and stabilization are performed outside the nozzle hole. The air blowing is performed in a direction opposite to each other, and a flat nozzle supporting surface is provided on both sides of a V-shaped groove in the same plane. It is intended.

[0003] The present invention further relates to a pulp dryer used when using the method for air-drying web material according to the present invention and / or when using the nozzle blowing box according to the present invention.

[0004]

BACKGROUND OF THE INVENTION In the field of paper and pulp industry, blow-out boxes are commonly used in paper pass dryers. The nozzle support surface of the blow-out box is formed of a flat plate, and a blow-out hole is punched in this plate. Such nozzles are to be dried by air blowing and are located on one or both sides of the air-supported web. In addition, holes are formed in the nozzle support surface in many rows in the running direction of the web. The blown air flows through the space between the web and the nozzle support surface and is collected and escaped through suction slots between the nozzle blowout boxes.

In conventional air dryer direct blow nozzle boxes for paper, board, or pulp webs, the blow of air is directed perpendicular to the web material to be dried. The problem heretofore has been the cross flow of air flowing between the web material to be dried and the nozzle support surface. The term "cross flow" as used herein refers to an air flow parallel to the plane of the nozzle support surface and the plane of the web, and parallel to or opposite to the running direction of the web. The "cross-flow" problem cannot be avoided because the air blast must escape from the processing gap. In a conventional blow-off nozzle box, such cross-flow causes poor heat transfer and the obstruction increases as the speed of the exhaust air flow increases. Further, the pressure loss generated in the blow-off nozzle box also increases as the speed of the cross flow increases. On the other hand, in consideration of the running property of the web material to be dried in the blowing nozzle box, a negative pressure region is formed on the support surface of the blowing nozzle box, thereby stabilizing the running of the web material, and thereby stabilizing the web material without distortion. It is desirable to address the problem of cross flow by taking into account the geometry of the outlet surface and its nozzle openings, so as to guarantee the running of the nozzle.

With regard closest prior art to the present invention, Fureekuto's Swedenborg - Den Patent No. 8,106,152 (corresponding to U.S. Pat. No. 4,505,053) and K. Chestnut - there is moth International Patent WO88 / 08950 (corresponding to US Pat. No. 5,016,363).

In the blow-off nozzle box disclosed in the Swedish patent, a triangular opening, the so-called "fish eye", is punched into its flat nozzle support surface and the front edge or triangular shape of the opening. Has a sharp edge at the bottom. Sharp edges are not a major disadvantage as long as the amount of air emitted from the nozzle is sufficient. Sometimes the amount of air received by the nozzle is significantly reduced. For example, when the air drying filter is closed, the web comes into contact with the nozzle support surface. Said sharp edges, for example, unravel the pulp web and make it flat.
In this case, the quality of the final product is degraded and waste is left in the dryer. The waste left in the dryer hinders the passage of the pulp web. This is referred to as the production of "cigars" because the shape of the material separated from the surface of the pulp web is cigar-shaped.

The present invention relates primarily to a nozzle blowout box used in pulp dryers, wherein the web travels above the nozzles and support surfaces of the blowout box. The function of the air blowing is to transfer heat from the blowing air to the web and to support the web in a contactless manner. In view of the running property of the web, it is desirable to blow air in parallel with the plane of the nozzle. In this case, the web is 3
It is stably supported at an interval of about 6 mm. However, in this case, in the conventional nozzle blowing box, the speed of the exhaust air flowing in the space between the web and the nozzle increases. As a result, heat transfer is degraded and significant pressure loss occurs. To reduce the adverse effects caused by the high speed of the exhaust air, the nozzles may be made sufficiently narrow, but this increases the number of nozzles and considerably increases the manufacturing cost of the dryer.

[0009]

SUMMARY OF THE INVENTION The present invention overcomes these disadvantages of the prior art and provides a novel method and a novel nozzle blow-off box that can improve the heat transfer from the dry air to the web to be dried. The purpose is to provide. Such an improvement in heat transfer can be achieved sufficiently effectively with a small-sized dryer, so that, for example, the construction cost of pulp dryers and the cost of machinery and equipment can be reliably reduced.

[0010] Another object of the present invention is to reduce the deterioration effect of heat transfer due to cross flow and to stabilize the running of the web.

[0011]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and the method of the present invention is air-supported with respect to a nozzle support surface to improve heat transfer as compared to a planar support surface. The nozzle support surface is provided with side walls such that the flow velocity of the air running parallel to the plane of the web to be dried is initially kept substantially constant, and thereafter is reduced steplessly and / or stepwise in the outflow direction of the air. Thus, the main feature is that the flow velocity of the air is reduced in the side area of the nozzle support surface.

[0012] The nozzle blow-out box of the present invention has a stepless and / or stepless support surface further away from the web material to be supported.
Alternatively, an extended portion of the nozzle support surface portion is formed by gradually separating the nozzle support surface portion. In the area of the extended support surface portion, the flow velocity of air for the stable support is lower than that of the flat nozzle support surface portion, and the nozzle support surface is further provided with a plurality of nozzle holes, thereby being supported by the nozzle support surface. The main feature is that it is blown substantially perpendicularly from a nozzle blowing box to the plane of the web material.

In accordance with the present invention, the reduction in heat transfer due to cross flow is minimized by lowering the side area of the nozzle to a level lower than the center of the plane, thereby reducing the speed of the cross flow. Furthermore, the cross flow is preferably directed such that it does not directly hit the direct jet air jet stream at the nozzle plane or lower side.

In the present invention, the lower side area of the nozzle supporting surface is based on the fact that the efficiency of heat transfer is deteriorated when the flow velocity of the exhaust air flowing through the web and the nozzle supporting surface is high. The smaller the gap between the web and the nozzle support surface, the higher the flow rate of the exhaust air. As more air is generated, the speed of the discharged air increases in the direction from the center of the nozzle toward both ends. By lowering the side area of the nozzle support surface according to the present invention, the flow rate of air in this side area can be reduced.

The nozzle blowing box of the present invention is based on a combination of the nozzle and the positive / negative pressure, and the magnitude of the cross flow for generating the negative pressure is approximately selected in relation to the direct blowing air amount. .

The characteristics of the hole-nozzle area of the present invention at the nozzle support surface are such that even if the gap between the web and the nozzle support surface is very small enough to operate the nozzle of the present invention, the exhaust air blows out of the nozzle hole. Unless the jet of air is substantially obstructed to a certain extent, the heat transfer efficiency is essentially unaffected by the gap. On the other hand, when the rows of nozzle holes are provided in multiple rows, the air discharged from the nozzle passes through the end of the space between the web and the nozzle, and if the speed increases, As the height increases, the discharged air hinders the jet of air blown out from the nozzle holes, thereby reducing the efficiency of heat transfer.

In a preferred embodiment of the nozzle blowing box of the present invention, air is jetted from the wall of a V-shaped groove located at the center of the nozzle support surface, and this air jet is formed on both sides of the V-shaped groove. It is made in a direction intersecting each other at a curved point extending from each side of the wall so as to be continuous with the plane portion of the support surface. Since this air jet is directed tangentially to the bending point, it changes direction at the bending point due to the Coanda effect and becomes parallel to the plane portion of the support surface. A negative pressure region is formed between the web and the nozzle support surface according to Bernoulli's law, whereby the position of the web is maintained at a certain distance from the support surface, and is generally about 3 to 6 mm. Keep distance and stabilize. Attempts have also been made to avoid direct collisions between the direct jet and the lateral air jet on the horizontal portion of the support surface.

[0018]

According to the present invention, the web to be dried is placed on the web from below.
Air blowing substantially perpendicular to the web and air blowing substantially parallel to the plane of the web, heat is sent to the web by the two blows, the web is contactlessly air supported, and the web is passed through a dryer. Is stabilized. To improve the heat transfer compared to a flat support surface,
A lateral zone such that the flow velocity of the air, which runs parallel to the plane of the web to be air-supported to be dried with respect to the nozzle support surface, is initially kept substantially constant and then decreases rapidly and / or gradually in the direction of the outflow of the air. Is provided on the nozzle support surface, whereby the flow velocity of air is reduced in the side area of the nozzle support surface.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to several examples shown in the accompanying drawings and test results relating to the examples.

FIG. 1 is a schematic longitudinal section in the machine direction of a pulp dryer using a method according to the invention and a set of nozzle blow-out boxes. The pulp dryer has a closed hood 12 having a set of nozzle blowing boxes 30 according to the present invention therein and arranged facing the boxes,
It consists of a set of direct blow boxes 40,
A web W to be dried is conveyed through a processing gap 25 formed by the set of boxes, supported by contactless air. Things such equivalent to the pulp web W _in or which are sent through a dryer wet press 10 and Russia - through Le 11, the tension is adjusted, off through the inlet 12a - are sent to de 12. In the hood 12, the web W to be dried is guided by the guide rolls 13 and is pulled forward or backward in the horizontal direction and continues running. The dried web W is taken out from the outlet 12b at the bottom of the hood 12, and is further aligned with the aligning roll 14.
And taken out through the drive roll 15 (W
_out ). The path of the web passing belt or loop is indicated by the dashed line 16.

In FIG. 1, the circulation of the dry air generated in the hood 12 is indicated by arrows A ₁ . . . It indicated by A _2. Duct - Air related thereto to the arrow A ₁
17 indicates that the replacement air is introduced from the heat recovery unit,
Arrow A ₂ air related thereto - duct 18 is shown to carry the discharged air to the heat recovery unit.

FIG. 2 shows the method according to the invention and the module structure of a pulp dryer using a nozzle blow-out box, the basic principle of which is shown, for example, in FIG.
It is similar to that of The dryer blower module comprises a blower tower 21 and a blower having an impeller 22. The module structure has a thermal radiator 24 through which the blown air flows into the gap between the upper and lower nozzles, ie, the web gap 25. In addition, this module structure provides an air filter 26
including. On the operating side of the blower module there is a maintenance bridge 28, in connection with which an inspection gate 27 for the blower motor and an inspection door 29 for the blower module are provided. FIG. 2 shows the circulation of dry air as indicated by the arrows, and the nozzle blow-out boxes 30, 40 according to the invention.
, And a web gap 25 between them.

With reference to FIGS. 1 and 2, the above description shows an example of application of the method according to the invention and the nozzle blow-off boxes 30, 40 for one application, whereas the method according to the invention and the nozzle blow-out boxes 30,40 The application is also possible in many other fields. Other than the pulp dryer, for example, application to boards and paper webs can be considered. Although the pulp dryer is the most effective and basic field of application of the present invention, different effects are expected in other fields depending on the purpose.

FIG. 3 shows a set of nozzle outlet boxes 30 according to the present invention and a set of direct blow type boxes 40 on the opposite side. In the following, they will be simply referred to as "lower boxes" since they are preferably positioned below the horizontally running web W with respect to the nozzle outlet boxes 30. Each lower box 30
There is a free space 30a between them, and correspondingly, there is a free space 40a between the direct blow boxes 40, and the blown air is blown by these free spaces 30a and 40a, and FIG.
Is returned by the blower 22 through the heat radiator 24 shown in FIG. As shown in FIG. 3, the web W to be dried, typically a pulp web, runs horizontally through a web gap 25. Web gap 25
Is defined by a lower box 30 arranged with a uniform space on the lower horizontal plane, and a direct blow box 40 arranged with a uniform space on the upper horizontal plane. Regard the lower box 30, the web W is normally intended to heavy (on the order of 2000 g / sq.m by weight of the wet pulp web), which is supported by the balloon B ₂ and B _3. Direct blow - horizontal B ₁ blowoff a direction perpendicular to the plane of the web W through the nozzle holes 42 provided in the lower wall of the box 40 is applied to the web W,
This balloon B _1, the web W is dried from above.

FIGS. 4 and 6 and FIGS. 8A and 8B show the structure of the lower box 30 in more detail. In the center of the support surface 31 of the lower box 30, there is provided a transverse groove 32, that is, a groove 32 crossing the web W in the lateral direction, and this groove is open toward the web W. The opening angle a of the V-shaped groove 32 is generally a = 50 ° to 90 °, preferably a = 60 ° to 80 °. V-shaped groove 32
Inclined wall, which is preferably planar and has a radius of curvature R
At a middle angle b in the curved portion 31b of the support surface, it is connected to the horizontal surface portion 34 of the support surface. As can be seen from FIG.
And the angle b, a relationship of a + 2b = 180 ° is established. A plurality of blowout holes 33 are provided in a row on both sides of the inclined plane of the V-shaped groove 32. Blowing holes 33, the jet B ₃ of air blown therefrom is directed tangentially to the curved portion 31b, bending the air jets B ₃ of the Coanda effect in the curved portion 31b along the flat portion 34 of the support surface 31 , as the jet B ₃ becomes parallel to the plane portion 34, it is configured. Blow-out hole 33
Is provided alternately staggered on opposite sides of the V-shaped groove 32, the jet B ₃ are disposed so as to intersect in opposite directions. Thus, one set of jets B ₃ are parallel to the running direction and the plane of the web W, the other set web W
, But in the direction opposite to the running direction of the web W. Verne - Jet B ₃ according to the law of Lee generates a region of negative pressure between the web W and the support surface 31, whereby the web W is kept a certain distance H from the support surface, generally, H = 3 It is stabilized while maintaining a distance of about 6 mm.
In this case, air drying of the web W is generally most efficient.

On both sides of the support surface 31, there are side regions 35 which are lowered over the length L ₁ in the direction of travel of the web. Lower than the height of the web W. In FIG. 6, the side area 35 is a plane ramp with a slope, the distance of which in relation to the central plane 34 is indicated by h ₂ at the end of the box 30.

In the nozzle blowing box according to the invention, at the web processing gap 25 below the web W, the air velocity is initially substantially constant with respect to the plane of the support surface 31 and thereafter towards the end of the lower box 30 As it proceeds toward the space 30a of the web processing gap 25,
The speed decreases stepwise or continuously with respect to b, 35d, and 35e. This significantly increases heat transfer, as can be seen from the test results shown in FIGS. Increased heat transfer is mainly due to the lower support surface 35; 35b, 35d, 3
In 5e, parallel air flow rate to the plane of the web W is significantly reduced, based on the fact that the for heat transfer directly balloon B ₂ in inter alia increases.

In the pulp dryer, FIGS. 4 and 5
The lower box 30 and the direct blowing box 40 shown in FIG. Therefore,
Surfaces 41 and 31 are substantially parallel to each other and generally define a horizontal plane. The end of the face 41 of the direct blowing box 40 is formed with a rounded rim 43, and the end of the face 31 of the lower box 30 is formed with the corresponding rounded rim 31
a is formed.

The lower box 30 and the direct blowing box 40
The nozzle holes 42 and 36 are provided on the opposing surfaces 31 and 41. A preferred example of the distribution of the nozzle holes 36 in the lower box 30 is shown in FIG. 8A. Nozzle hole 42; web W from 36
Callout B ₁ in the vertical direction towards; is performed B _2, whereby drying of the web W is promoted. Since flow velocity in the support surface 35 in order to cross the basin between the web supporting surface is increased is reduced, balloon vertical air towards the lower surface of the web, i.e. directly balloon B ₂ is made longer time.

FIG. 8B is a view for explaining a preferred embodiment in terms of the shape and dimensions of the V-shaped groove 32 described above.
The shape of FIG. 8B is bilaterally symmetric with respect to the transverse vertical center plane KK. The jets F ₁ and F _{2 of} air blown from opposite directions may be tangential to the curved portion 31 b leading to the end of the V-shaped groove 32, change direction by the Coanda effect and become parallel to the plane portion 34. This is the starting point of the design of the V-shaped groove 32. Air is a flat part between the groove 32 and the flat part 34
Especially rounded to be guided along 34.

FIGS. 7A to 7E show various examples of the support surface of the lower box 30. FIG. The nozzle box 30A shown in FIG. 7A includes a support surface 31, in which a flat portion 34 and a subsequent inclined portion 35 having a flat slope are provided on both sides of a V-shaped groove 32.

FIG. 7B shows a particularly effective blow box 30B.
Is shown. In the box 30B, on both sides of the V-shaped groove 32, a plane portion 34b of the support surface and a step portion 37 following the flat portion 34b are provided. The step portion 37 has a surface perpendicular to both the first flat portion 34b of the support surface and the flat portion 35b following the step portion 37. The first portions 34b of the support surfaces 31 on both sides are parallel to each other and are on the same horizontal plane. Similarly, the support surface
31 are also parallel to each other and are on the same horizontal plane. FIG. 7B also illustrates a preferred example of the dimensions of box 30B. According to FIG. 7B, the height h ₂ of the step 37 is 10 mm, and can be changed approximately in the range of h ₂ = 7 to 15 mm.

FIG. 7C shows the nozzle box 30C in a basic form. In this box, the support surface 31c is a flat surface over both sides of the V-shaped groove 32. Strictly speaking, this nozzle box 30C is not according to the present invention, but is shown for comparison with the present invention, and the comparison result will be apparent from FIGS. 9 and 10 described later.

FIG. 7D shows a blow box 30 according to the present invention.
D is shown. The box 30D has a relatively long flat supporting surface 34d and a relatively short and steeply inclined side area.
35d. FIG. 7D also shows a preferred example of the dimensions of the box.

FIG. 7E shows a modification of the blow box shown in FIG. 7B. The box 30E is provided with a relatively long flat support surface portion 34e, a step portion 37 following it, and a relatively short support surface portion 35e following it.
FIG. 7E also shows a structural example of box 30E.

[0036] Figure 8A shows the relative position and staggered arrangement of the nozzle holes 33 of the V-shaped groove 32, the opposite direction of the jet B ₃ is blown out to intersect with such sequences. Opening 36 of the nozzle support surfaces 31 are aligned in four rows, but the jet B ₂ and B ₃ are staggered so as never collide with each other. The distance between the nozzle holes 33 is generally in the range of 20 to 50 mm, and the distance between the nozzle openings 36 is generally in the range of 40 to 100 mm.

The dimensions of the blow box shown in FIGS. 6 and 7 are as follows. With respect to the dimensions of FIG. 6, the angle a between the two flat walls of the V-shaped groove 32 is approximately a = 50
From 90 ° to 90 °, and the angle b of the Coanda surface 31b.
Is approximately in the range of b = 45 ° to 65 °,
The depth h ₁ of the V-shaped groove 32 is approximately in the range of h ₁ = (2 to 5) × Φ, where Φ is the diameter of the nozzle hole 33 in the wall of the V-shaped groove 32. It is. Nozzle hole 33 diameter Φ
Is selected in relation to the diameter of the nozzle holes 36 in the support surface, the amount of air jets B ₃ blown from the nozzle hole 33, balloon entire nozzle blowout box (jet B ₂ and B ₃₎
It is chosen to be between 30% and 60% of the air volume, preferably between 35% and 45%. Relates the length L ₁ in the web travel direction, the side regions 35,35b supporting surface 31 of the nozzle blowout box, 35d, the 35e, which may be any shape that bends gradually or rapidly, L ₁ = (0 .
1 to 0.3) × L, preferably L ₁ = (0.2 to 0.25) × L, where L is the total length of the support surface of the nozzle blowing box 30 and L っ て 300 to 5
Within the range of 00mm, and the side areas 35, 35b, 35 of the support surface 31
d, select the maximum value h ₂ of the difference when comparing the height of 35e and the plane of the nozzle support surfaces to the range of h ₂ = 7 to 15 mm, preferably with h ₂ ≒ 10 mm.

FIGS. 9 and 10 graphically illustrate test results obtained for the nozzles shown in FIGS. 7A through 7E. 9 and 10, the vertical axis represents the relative heat transfer coefficient α.
_R is shown, and the horizontal axis is the distance from the support surface 31, especially the plane portion 34 thereof, to the web W. The letters AE added to the respective boxes 30A-E in FIGS. 7A-7E.
Corresponds to AE in FIGS. 9 and 10.

FIGS. 9 and 10 were tested with respect to the nozzles shown in FIGS. 7A to 7E, but their heat transfer was tested by blowing hot air onto a flat metal surface using a static test apparatus. It is. The efficiency of heat transfer was obtained by measuring the heat transfer rate of a metal plate using a temperature measuring detector. 9 and 10, the measured relative heat transfer coefficient α _R is a function of the distance H between the web and the support surface 31 of the nozzle box, varying the blowing speed as a parameter. The results show that where the distance H is equal to the normal air transmission distance of the pulp web (3 to 6 mm), the heat transfer coefficient is reduced by lowering the side areas 35, 35b, 35d, 35e of the support surface 31. With just a flat support surface (Fig. 7
It is increased by about 5% to 10% as compared with the C support surface 31c). Further, even if the distance H is set to be longer than that, the effect corresponding thereto cannot be obtained. The increase in heat transfer coefficient is due to the lower nozzle in the side areas 35, 35b of the support surface 31 (FIGS. 7A and 7B).
In the case of the highest. The measurement results in FIG. 9 are _obtained when the blowing speed W _puh of the jets B ₂ and B ₃ is W _puh = 26 m / s, and the measurement results in FIG. 10 indicate that the blowing speed W _puh of the jets B ₂ and B ₃ is W _puh = 34 m / s. In any case, the temperature T _{puh of the} blown air is T _puh = 15.
It is the one at 0 ° C. As is evident from FIGS. 9 and 10, the difference in the relative heat transfer coefficient α _R in each case is correctly pronounced at the optimum air transmission web distance H = 3 to 6 mm.

The simulations and methods used in the measurements of FIGS. 9 and 10 are published in Helsinxin Podium on June 4-7, 1991 in Helsinki on alternative methods of pulp and paper drying. "Air-
Entitled "Foil Dryer Heat Transfer"
P. Hikyre and I. It is described in detail in the literature by Jokioinen.

Based on the measurements described above, the most effective embodiment of the present invention is the nozzle box 30A so far shown in FIG. 7A. According to the measurement results of FIGS. 9 and 10, the support surfaces 34b and 35b having the steep steps 37 as shown in FIG. 7B are optimal from the viewpoint of heat transfer, but considering the overall surface, FIG. The nozzle box 30A shown in FIG. 7A is preferred. The nozzle box 30A has a continuous downwardly sloped side portion 35 of the support surface, and the shape of the blowing surface does not include an acute angle, so that there is a low risk of forming "sigma". Thus, so far, the nozzle box shown in FIG.
30A is the most preferred embodiment of the present invention. In this case, the distance from the horizontal surface portion 34 of the support surface 31 to the pulp web W is
For example, it is about 5 mm.

[0042] The present invention has been described by way of some embodiments, the present invention is not limited to these examples,
Many modifications and variations are possible within the scope of the inventive concept as set forth in the appended claims.

[0043]

As described above, according to the present invention, the side area of the nozzle support surface of the nozzle blowing box is lowered so that the cross flow velocity decreases as the cross-sectional flow area between the web and the support surface increases. Thus, the efficiency of the heat transfer of the air jet blown from the directly blow-off opening provided on the nozzle support surface portion which is lowered and / or the straight nozzle support surface portion is improved.

The nozzle blow-out box of the present invention is suitable for use in web drying in which a low basis weight web (200 g / sq.m or less) is dried on one side or both sides of the web.
It is also suitable for use in web drying where both the lower and upper portions of the web are dried. For heavy webs (less than 200 g / sq.m), such as pulp webs, the nozzle blow-out box of the present invention may be a lower nozzle used with a direct blow-off box acting as an upper nozzle, or a lower nozzle that is only single-sided dried Most suitable for boxes.

Another advantage achieved by the shape of the outlet support surface of the nozzle outlet box of the present invention is that the cross flow of air is guided by the rounded surface of the central V-shaped groove and out of the V-shaped groove. The edge of the support surface portion has a smooth outlet surface when it flows out.

According to the present invention, the heat transfer to the web is improved by 5% to 10%, as shown by the measurements. This improvement can reduce the size of the dryer, reduce the cost of the dryer, the cost of installing the machine room, and, indirectly, reduce the number of production interruptions and improve the uptime of the dryer. The advantages mentioned above are particularly important when the pulp dryer is large and complex.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal section in the machine direction of a pulp dryer using a method according to the invention and a set of nozzle blowing boxes.

FIG. 2 is an axial view showing a module structure of a pulp dryer using a method and a nozzle blowing box according to the present invention.

FIG. 3 is a schematic longitudinal sectional view in the machine direction of a set of nozzle blow-out boxes according to the present invention and a set of direct blow-type boxes on the upper side thereof.

FIG. 4 is an axial side view for explaining a nozzle blowing box and a principle of the blowing according to the present invention.

FIG. 5 is an axial side view of the structure of an upper direct blow box, that is, a direct blow box.

FIG. 6 is an explanatory view of an embodiment showing the support surface of the nozzle blow-out box according to the present invention and details of the blow-out nozzle of the support surface together with the most important dimensional parameters.

FIGS. 7A and 7B are an example showing various examples in which the shape and dimensions of the nozzle support surface of the nozzle blowing box according to the present invention are different, and an explanatory view of a basic nozzle blowing box.

FIG. 8A is a view of the nozzle blowing box shown in FIG. 4 or FIG. 5 as viewed from the nozzle supporting surface side, and FIG. 8B is a view showing a shape and dimensions of a V-shaped groove of the nozzle; FIG. 4 is an enlarged schematic longitudinal sectional view in the machine direction of a V-shaped groove showing an example.

FIG. 9 is a graph showing the relationship between the relative heat transfer coefficient and the web distance for the nozzles shown in FIGS. 7A to 7E at a first air blowing speed.

10 is a graph showing the case the equivalent of Figure 9 in the first air faster than blowoff speed second air blowout speed.

[Explanation of symbols]

10 Wet press 11 Roll 12 Sealed hood 13 Guide roll 13 14 Roll 15 Drive roll 16 Web thread belt 17 Air duct 18 Air duct 18 21 Blower tower 22 Impeller 24 Heat radiator 25 Web gap 26 Air filter 27 Inspection gate for blower motor 28 Maintenance bridge 29 Inspection door for blower module 30 Nozzle outlet box 30a Free space 31b Curved portion 31 Support surface 32 Cross groove 33 Outlet 34 Horizontal surface of support surface 35 Side area 35b Flat surface 35d Inclined side area 35e Support surface 36 Nozzle hole 37 Step 40 Direct blowing box 40a Free space 40a 41 surface 42 Nozzle hole 43 Edge W W Web B ₁ Direct blowing B ₂ Direct blowing B ₃ jet flow

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Showa 48-4465 (JP, U) Japanese Patent Publication No. 38-13343 (JP, B1) US Patent 5016363 (US, A) West German Patent Application Publication 1143474 (DE) , B1) (58) Fields surveyed (Int. Cl. ⁷ , DB name) D21F 5/18

Claims (16)

(57) [Claims] 1. A shall apply in dry燥方method of the web material of relatively high basis weight, such as pulp webs, the heat is transmitted to the web, weather
The first jet from the nozzle support surface located below the nozzle
To support the web in a non-contact air
Stabilizing the running of the web, and the first jet
A jet, the second jet being substantially parallel to the plane of the web.
And the direction of travel of the web and the direction opposite to the direction of travel.
Web running in the center of the nozzle support surface.
It is blown out from the groove located across the row direction,
The nozzle support surface is a flat portion provided on both sides of the groove.
In the same plane parallel to the plane of the web
In the method for drying a web material with an air dryer, the first jet includes a third jet, and the third jet includes:
The nozzle hole is vertically applied to the web from the nozzle hole, and the nozzle hole is
A surface portion and a side area portion of the nozzle support surface;
A portion on the side of the plane portion opposite to the groove, and
Step and / or stepwise over the flat part
Lower to a lower height, the web in the side area
The cross-sectional basin between the nozzle support surface is increased,
Air flow parallel to the plane of the web in the region,
Air velocity parallel to the plane of the web in the area of the plane
Dry燥方method of web material, characterized in that lowering in comparison with. 2. A dry燥方method of web material according to claim 1, a plurality of the nozzle supporting surface, the nozzle support
The surface is connected to a plurality of nozzle
Web material characterized by being formed by the head surface of
Of dry燥方method. 3. A dry <br/>燥方method of web material according to claim 1 or 2, by the side band portions of the nozzle support surfaces to be stepless and / or stepwise lowered, web drying air the transfer of heat to the optimum to, and dry the web material, characterized by adjusting the travel height of the web in the air to be dried Rutotomoni is supported lifting regarding <br/> to the nozzle supporting surface <br/> Drying method. 4. A dry燥方method of web material according to claim 2, the second jet the parallel performed from the groove
And connecting the walls of the groove to the flat surface of the nozzle support surfaces
Or nearly tangential to the nozzle hole with respect to the curved guide surface that
Carried al, by the guide surface by Coanda effect, by changing the direction of the second jets is parallel to the planar portion
And a plane of a web running near the second jet.
Dry燥方method of web material, characterized in that parallel to. 5. A dry燥方method of web material according to any one of claims 2 to 4, wherein the parallel that are to be carried out in parallel and the web plane to cross the direction opposite with the nozzle supporting surface blowout air quantity of the second jet, dry燥方method of web material which is a 30% to 60% of the blow-out air quantity of the entire nozzle blowout box. 6. A dry燥方method of web material according to any one of claims 2 to 5, the second jet the parallel is
The running direction of the web in the side area portion of the nozzle support surface and
Slow down over the length distance L ₁ running parallel, wherein L ₁ = select the range (0.1 to 0.3) × L, where L is a total length of Nozzle supporting lifting surface L = 300 to 5
Dry燥方method of web material, characterized in that pick a range of 300 mm. 7. A dry燥方method of web material according to any one of claims 2 to 6, space is provided between the box balloon nozzles blowing air nozzle blowout box - through the scan, the a web nozzle Between the support surface
Dry燥方method of web material, characterized in that removal outside the drying support Gyatsupu formed. 8. A dry燥方method of web material according to any one of claims 2 to 7, provided top directly balloon box on the opposite side of the nozzle blowout box located under the web to be dried which is air supported performs substantially perpendicular to the fourth jets web plane towards the outside of the upper direct blowout box, dry燥方method of web material, characterized by drying the web from both sides. 9.Included in air dryer for drying web material
A nozzle blow-out box to be
The delivery box is located below the web and the nozzle
Apply the first jet to the web material from the delivery box,
With the first jet, heat is transferred to the web and
In addition, non-contact air support of the web and stabilization of the running of the web
Done, the nozzle blowing box faces the web
No A box portion provided with a chirping support surface,
The chirping support surface includes a V-shaped groove and a flat portion, a) The V-shaped groove runs the web at the center of the support surface.
Direction, the groove is open to the web
A series of nozzle holes are provided on the opposite wall
In order to support and stabilize the outside of the nozzle hole,
The second jet contained in the first jet is blown out, and the second
The two jets are substantially parallel to the plane of the web,
Intersects with the running direction of the b) the flat portions are provided on both sides of the V-shaped groove,
The plane part is located in the same plane parallel to the plane of the web
 In the nozzle blowing box,The nozzle support surface further includes a side area portion and a nozzle hole.
See c) The side area is provided on the side of the flat surface opposite to the groove.
The side portions can be steplessly and / or stepwise
The side area is lowered to a height lower than
Placed further away from the d) the nozzle holes are provided in the plane portion and the side region portion;
From the nozzle hole, substantially perpendicular to the plane of the web,
An additional third jet included in the first jet is applied.
And Air parallel to the plane of the web in the region of said lateral zone
Of the web in the area of the plane portion
Air flow velocity is lower than Characterized by
Nozzle blowing box. 10. A nozzle blowout box according to claim 9, extensions of both planar walls of said V-shaped groove is constituted by the Coanda guide surface curved, the Coanda
The guide surface connects the flat wall to the flat portion of the nozzle support surface.
And, the nozzle holes provided in both planar walls of said V-shaped groove is the main way of the second jets ejected from the nozzle hole
A nozzle blowing box , wherein the direction is substantially tangential to a curved Coanda guide surface facing the nozzle hole . 11. The V-shaped groove according to claim 9, wherein an angle a between both plane walls of the V-shaped groove is a = 50 ° to 90 °. depth h ₁ is a h ₁ = (2 to 5) x Φ,
Here, Φ is the diameter of the nozzle hole in the wall of the V-shaped groove, wherein the nozzle blowing box is characterized in that: 12. The nozzle blow-out box according to claim 9, wherein the length L ₁ in the running direction of the web material is stepless and / or stepless on the nozzle support surface of the nozzle blow-out box. Typically
Side area portion is low, L ₁ = (0.1 to 0.
3) × L, where L is the total length of the nozzle blowing box in the web running direction , and L = 3
00 to select a range of 500 mm, further select the height of the side region portions of the nozzle support surfaces to the range of the maximum value h ₂ of h ₂ = 7 to 15mm difference when compared to the flat portion of the nozzle supporting surface
Nozzle blowout box, characterized in department that. 13. The nozzle blow-out box according to claim 9, wherein the nozzle holes of the V-shaped groove are substantially formed on opposite flat walls of the V-shaped groove.
Are provided in a zigzag pattern at regular intervals alternately in the range of 20 to 50 mm .
Said additional third jet substantially perpendicular to the plane
Is the nozzle hole on the nozzle supporting surface leaving said are staggered with respect to the nozzle hole of the V-shaped groove forms a sequence of 3 乃 Itaru five columns intersecting the running direction of the web, yet the web Provided at substantially constant intervals in both the running direction and the cross direction, where the constant spacing is 4
A nozzle blowing box having a diameter in a range of 0 to 100 mm. 14.ContractAny one of claims 9 to 13
Nozzle blowing boxInclude multipleFor pulp dryer
AndThe nozzle blowing box is oriented in the direction of travel of the pulp web.
They are arranged one by one on the same horizontal plane, and
Are arranged with a gap between each other, Air for supporting, drying and stabilizing the pulp web is
Through the gap, the nozzle of the nozzle blowing box
A processing gear formed between a support surface and the pulp web.
Mainly missed from the tip, A plurality of rows of the nozzle blowing boxes are vertically set.
The pulp web to be dried
Turn forward in the horizontal direction between
The running direction of the pulp web is turned by the reversing roller.
Reversed between forward running Pulp characterized by that
Laiya. 15. The pulp dryer according to claim 14, wherein the pulp dryer includes a direct blow box provided above a web material opposite the nozzle blow box , wherein the direct blow box includes a web.
To apply a fourth jet substantially perpendicular to the web
Provided on the plane of the direct blowing box facing
A pulp dryer, comprising an intermediate space through which the air of the fourth jet passes is provided between the direct blow-out boxes. 16. The pulp dryer according to claim 15, wherein the nozzle blowing box located below the web and the direct blowing box located on the opposite side have the same length in the running direction of the web,
A pulp dryer characterized in that the pulp dryers are arranged so as to face each other at uniform intervals.