FI92421B - Method for Air Drying of Substances, Nozzle Blower for an Air Dryer and Cellulose Dryer - Google Patents

Method for Air Drying of Substances, Nozzle Blower for an Air Dryer and Cellulose Dryer Download PDF

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Publication number
FI92421B
FI92421B FI921193A FI921193A FI92421B FI 92421 B FI92421 B FI 92421B FI 921193 A FI921193 A FI 921193A FI 921193 A FI921193 A FI 921193A FI 92421 B FI92421 B FI 92421B
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Finland
Prior art keywords
nozzle
web
air
blowing
cellulose
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FI921193A
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Finnish (fi)
Swedish (sv)
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FI921193A (en
FI921193A0 (en
Inventor
Pertti Heikkilae
Ilkka Jokioinen
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Valmet Paper Machinery Inc
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Classifications

    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21FPAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00Dryer section of machines for making continuous webs of paper
    • D21F5/18Drying webs by hot air
    • D21F5/185Supporting webs in hot air dryers
    • D21F5/187Supporting webs in hot air dryers by air jets
    • D21F5/188Blowing devices
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26DRYING
    • F26BDRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B13/00Machines and apparatus for drying fabrics, fibres, yarns, or other materials in long lengths, with progressive movement
    • F26B13/10Arrangements for feeding, heating or supporting materials; Controlling movement, tension or position of materials
    • F26B13/101Supporting materials without tension, e.g. on or between foraminous belts
    • F26B13/104Supporting 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

Description

92421

Method for air drying of material trays, air dryer nozzle-blast box and pulp dryer Förfarande för lufttorkning av ämnesbanor, munstycke-bläsningsläda för en lufttork och cellulosatork 5

The invention relates to a method for air drying webs of webs, in particular webs of relatively high basis weight, such as pulp webs, in which the web to be dried is subjected to air blows substantially perpendicular thereto below it and substantially web-level blows to transfer heat and contact with the web. stabilizing through a dryer, and wherein the airflow velocity along the plane of the web to be dried and air-supported in the nozzle carrier surface is initially maintained substantially constant, after which the airflow rate is reduced in the edge regions of said carrier surface using ramp and / or stepped airflow-decreasing nozzles.

The invention further relates to a nozzle-blow box for an air dryer, through which air blows are applied to the material web to be dried, which provides both heat transfer from the drying air to the web and its contact with air support and its flow stabilization, and which nozzle-blower box comprises a housing part a nozzle bearing surface with a groove in the center transverse to the direction of travel of the track, a substantially V-shaped groove • opening towards the track and having a series of nozzle holes in opposite walls so that 25 sets of nozzle holes can be aligned with each other; wherein the nozzle bearing surface has planar nozzle bearing portions in the same plane on both sides of its V-groove.

The invention further relates to a pulp dryer in which nozzle-blowing boxes according to the invention are applied, through which air-blowing is applied to the pulp web to be dried, which provides both heat transfer from the drying air to the pulp web and air contact and stabilization of its flow, and which nozzle-blowing boxes comprise a housing part with a nozzle bearing surface facing the pulp web, having in the center a substantially V-shaped groove transverse to the direction of flow of the pulp web 2 92421, opening towards the web and having a series of nozzle holes in its opposite walls so that air blowing, and wherein the nozzle bearing surface has planar nozzle bearing portions in the same plane on both sides of its 5 V groove.

Blow boxes are commonly used in the pulp dryers of the paper and pulp industry, the nozzle-bearing surface of which consists of a flat plate with blown-10 holes pierced. Such nozzles are placed on either or both sides of the dryer and air-supported track. The nozzle bearing surface generally has a plurality of rows of holes in a row when viewed in the direction of travel of the track. The blowing air passes in the space between the track and the nozzle-bearing surface and the blowing air is collected through the suction slots between the nozzle boxes.

15

In the previously known direct blow nozzle boxes of paper, board or pulp web air dryers, in which the air blow is directed perpendicular to the material web to be dried, there is a known problem with the lateral flow of used air between the web to be dried and the nozzle support surface. Above and thereafter, the term "lateral flow" refers to air currents parallel to the bearing surface and the plane of the track, which are further parallel to or opposite to the path of the track. Since air must leave the treatment gap, lateral flow cannot be avoided. Em. the lateral flow impairs the heat transfer of the known blow nozzle boxes and the disturbing effect increases as the exhaust air flow rate increases. In addition, the pressure drop caused by the blow box increases with increasing speed in the lateral flow. On the other hand, from the point of view of the runnability of the track to be dried, it is advantageous to take advantage of the lateral flow in the blow box by shaping the blow surface and its nozzle geometry so that a vacuum zone stabilizing the track passage is created on the blow box bearing surface.

30

With regard to the state of the art most closely related to the present invention, reference is made to Fläkt AB's SE patent 8,106,152 (corresponding U.S. patent 4,505,053) and K. Krieger's international! 92421 3 to WO 88/08950 (corresponding U.S. Patent 5,016,363). The object of the present invention is to further develop nozzle-blow boxes known from these patents, avoiding the drawbacks which appear in them, which will be described in more detail later.

5

Em. The blow boxes according to the SE patent have triangular openings punched into their planar nozzle support surface, so-called "fish eyes", the leading edge of which, i.e. the base of the triangle, has a sharp edge. There is no substantial inconvenience from the sharp edge as long as the amount of air coming out of the nozzle is sufficient. Sometimes the amount of air 10 received by the nozzle may be considerably reduced from the design value, e.g. when the drying air filters are clogged, whereby the path begins to contact the nozzle surface. Em. sharp edges have been found to plan, for example, from the surface of the pulp web away from the material, in which case both the quality of the final product suffers and debris remains inside the dryer. The debris, in turn, interferes with the headform of the pulp web. We speak of the formation of a "cigar", since the material detached from the surface of the pulp web 15 by planing forms a roll resembling the structure of a cigar.

The present invention relates in particular to nozzle-blow boxes for use in pulp dryers, in which the path passes above the nozzle and carrying surface of the boxes. The function of the air blows is both to transfer heat from the blown air to the track and to support the track 20 without contact. From the point of view of the runnability of the track, it is advantageous to blow part of the air parallel to the plane of the nozzle, whereby the track is stabilized 3-6 mm from the bearing surface. In this case, however, the speed of the exhaust air in the space between the track and the nozzle becomes high in the known nozzle-blow boxes. This results in deterioration of heat transfer and additional pressure drop. The detrimental effect of the high speed of the exhaust air 25 can be reduced by making the nozzles sufficiently narrow, but then the number of nozzles becomes so large that the manufacturing cost of the dryer substantially increases.

The object of the present invention is to provide a new method and a nozzle-30 blow box structure with which the above-mentioned drawbacks can be avoided and the heat transfer from the drying air to the drying and air-supported track can be improved. Said improvement in heat transfer can be most advantageously utilized in the form of a reduction in the size of the dryer 4 92421. This can, for example, decisively reduce the construction costs of a pulp dryer as well as the data center costs.

The object of the present invention is to reduce the heat transfer effect of the lateral flow 5 while at the same time the flow stabilizes the course of the track.

In order to achieve the above and later objects, the method of the invention is mainly characterized in that said reduction of the air flow rate substantially improves the heat transfer to the web compared to the flat bearing surface 10. perpendicular to said blows, the action time of the latter blows on the lower surface of the track being extended by increasing the flow cross-section between the track and the bearing surface in the edge areas of the track and the bearing surface. 15

The nozzle-blow box according to the invention, in turn, is mainly characterized in that said nozzle-bearing surface portions are extended by stepped and / or ramp-like support surface portions further away from the supported material track. and that the nozzle-bearing surface has a nozzle perforation through which blows substantially perpendicular to the plane of the material web to be supported can be directed from the nozzle-blow box.

The pulp dryer according to the invention is mainly characterized in that said nozzle-bearing surface portions are extended by stepped and / or ramp-like supporting surface portions further from the supported pulp web, in the region of which there is a nozzle perforation through which the nozzle-blow box can in addition be blown substantially perpendicular to the plane of the pulp web to be supported, the pulp dryer comprising a plurality of nozzle-blow boxes spaced horizontally apart

II

92421 5 from each other, through which the air supporting, drying and stabilizing the pulp web is mainly removed from the treatment intervals, that there are several nozzle-blowing boxes successively in the same horizontal plane in the direction of travel and that there are several rows of nozzle-blowing boxes on top of each other so that the drying pulp air-supported inside the pulp dryer hood in horizontal reciprocating and overlapping runs, between the runs of which the web is turned in opposite directions by turning rollers.

The effect of the lateral flow on the heat transfer is minimized by the invention by lowering the edge portions of the nozzle lower than the planar central part, whereby the side flow rate decreases. In addition, the side flows are most preferably directed so that they do not directly impinge on the direct jet air jets on the planar surface or the lowered edge portions.

The drop of the edge areas of the nozzle-bearing surface parts according to the invention is based on the idea that the high exhaust air flow rate between the track and the nozzle-bearing surface degrades the heat transfer coefficient. The lower the space between the track and the nozzle-bearing surface, the higher the exhaust air velocity. The exhaust air velocity increases in both directions from the nozzle centerline toward the edges as more air enters. By lowering the nozzle bearing surface edge areas in accordance with the present invention, the flow rate in this area is lower.

The nozzle-blow box according to the invention is a combination of an overpressure / vacuum nozzle, in which the magnitude of the lateral flow generating the vacuum is suitably selected in relation to the amount of air in the direct blow.

The bearing hole hole field according to the invention is characterized in that at the very small nozzle path distances at which the nozzles of the present invention operate, the heat transfer coefficient is not substantially distance dependent, provided that the exhaust air does not significantly interfere with air jets blowing from the nozzle holes. On the other hand, it is known that when there are many rows of nozzle holes in a row, the air coming from them has to travel towards the edges in the space between the nozzle and the track, and the higher this flow rate, the more it interferes with the air jets blown through the holes and degrades the heat transfer coefficient.

In a preferred embodiment of the nozzle-blow box according to the invention, air jets from the walls of the V-groove in the middle of the nozzle surface 5 are applied crosswise to a stepless rounding point between the planar roof surface on each side of the V-groove walls. As the air jets sideways at the rounding points, they turn parallel to the planar portions of the bearing surface due to the Coanda effect. According to the Bernoulli principle, a vacuum zone is created between the track and the bearing surfaces, which stabilizes the track bearing surface 10 at a certain distance, which is usually of the order of 3-6 mm. Also with a horizontal portion of the bearing surface, the invention rotates to avoid direct collisions between direct blowing jets and side-jet air jets.

According to the invention, the edge areas 15 of the nozzle-carrying surface of the nozzle-blowing box are reduced so that the lateral flow rate decreases as the flow cross-sectional area increases and the heat transfer effect of blowing jets coming through the reduced blown holes of the reduced inclined and / or straight nozzle-carrying part is improved.

The nozzle-blow box according to the invention is suitable for use in web drying 20 as well as in single / double-sided drying, on light webs (<200 g / m 2) both below and above the web. On heavy e.g. pulp webs, the nozzle-blow boxes according to the invention are best suited as lower nozzles together with direct blow boxes acting as upper nozzles or alone in single-sided drying as lower nozzle boxes.

As a further advantage, the geometry of the blow carrier surface of the nozzle-blow boxes according to the invention achieves a smooth and sharp-edged blow surface when the lateral flow air is introduced from the central V-groove under the guidance of rounded surfaces.

30 According to the measurements made according to the invention, the heat transfer to the track can be improved by about 5-10%, this improvement can be immediately utilized to reduce the size of the dryer, which substantially reduces the investment costs of the dryer and the data center, and also indirectly reduces production downtime and increases dryer operation. The above advantages are particularly important in large and complex pulp dryers.

When a nozzle-blown box according to the invention uses a V-shaped groove in the middle of the bearing surface through which the blows parallel to the bearing surface are cross-aligned, a rigid mechanical structure is provided in addition to the preferred blowing-heat transfer technique, in which the V-groove effectively stiffens the nozzle-bearing surface

A minor disadvantage of the blow surface of the blow box according to the invention is its somewhat more difficult manufacturability than its uniform planar surface. However, the disadvantage can be solved by developing manufacturing technology.

The invention will now be described in detail with reference to some preferred application examples of the invention shown in the figures of the accompanying drawing and the test results relating thereto.

Figure 1 schematically shows a vertical section of a pulp dryer applying the method of the invention and the nozzle-blow box assembly 20 in the machine direction.

Figure 2 shows an axonometric view of the modular structure of a pulp dryer applying the method of the invention and the nozzle-blow box system.

Fig. 3 schematically shows a machine direction vertical section of a nozzle-blow box system according to the invention and a direct blow-box box system above it.

Figure 4 shows axonometrically the nozzle-blow box according to the invention and the principle of its blows.

30

Figure 5 shows axonometrically the structure of the overhead direct blow box.

924 21 8

Figure 6 shows a more detailed implementation of the bearing surface of the nozzle-blow box according to the invention and its blow nozzles and the most important dimensioning parameters.

Figures 7A, 7B, 7C, 7D and 7E show different variations of the different implementations and dimensions of the bevels and steps of the nozzle-bearing surface of the nozzle-blow box according to the invention and to be compared.

Fig. 8A shows the nozzle-blow box of Figs. 4 or 5 as seen from the nozzle bearing surface side.

10

Figure 8B shows, on a larger scale, a preferred nozzle V-groove geometry and dimensioning in a schematic machine direction vertical section.

Fig. 9 shows the measured relative heat transfer coefficients 15 of the various Figs. 7A-7E as a function of the track distance at the first air blowing speed.

Fig. 10 shows the same measurement results at the second higher air blowing speed, corresponding to Fig. 9.

Figure 1 schematically shows a machine direction vertical longitudinal section of a pulp dryer applying the method of the invention and the nozzle-blow box system. The dryer comprises a closed hood 12, inside which there is a nozzle-blow box system 30 according to the invention and opposite it a direct blow box system 40, through the treatment intervals 25 of which the drying path W is passed in a non-contact air-supported manner. The pulp web Win 25 or the like to be introduced to the dryer is passed through the wet press 10 and the web tension control roller 11 through the inlet 12a inside the hood 12, where the web W to be dried runs back and forth in horizontal drawings under the guidance of the guide rollers 13. The dried web W is removed through the outlet opening 12b in the lower part of the hood 12 and is passed via the guide roller 15 via the traction roll 15 (Wout). In Figure 1, reference numeral 16 and dotted line 30 show the path of the track end conveyor belt or rope.

92421 9

According to Figure 1, the circulation of drying air inside the hood 12 is schematically shown by arrows Aj-A2. Arrows Aj and their associated air ducts 17 represent the import of replacement air from heat recovery, and arrows A2 and their associated air ducts 18 represent the export of exhaust air to heat recovery.

5

Fig. 2 shows the modular structure of the pulp dryer according to Fig. 1, which applies the method according to the invention and the nozzle-blow box system to its basic principle, e.g. The drying-blowing module comprises fan towers 21 and fans with impellers 22. The module structure comprises heating coils 24 through which the ground of the blowing silicon 10 is led to the upper and lower nozzle treatment intervals, i.e. the track gap 25. The module structure further includes air filters 26. The treatment side of the fan module in connection with the service hatches 27 of the fan motors and the service doors 29 of the fan modules. Figure 2 shows the circulation of the drying air shown by arrows, as well as the nozzle-blow boxes 30,40 according to the invention and their path spacings 25.

15

With regard to Figures 1 and 2, it should be emphasized that they have been described above as only some areas of application of the method and nozzle blow box assembly 30, 40 according to the invention and that the method and nozzle blow box assembly 30,40 according to the invention can be applied in many environments and non-pulp dryers, e.g. 20 cardboard and paper web dryers, although pulp dryers are the most advantageous and main area of application of the invention, where the various advantages of the invention are best utilized.

Figure 3 schematically shows a nozzle-blow box system 30 according to the invention and an opposite direct blow-box box system 40. The nozzle-blow boxes 30 are hereinafter abbreviated as a sub-box, since they are most preferably placed horizontally below the running track W. There are free spaces 30a between the lower boxes 30 and free spaces 40a between the direct blow boxes 40, respectively. Through the spaces 30a and 40a, the blowing air is further led through the heating coils 24 shown in Fig. 2 30, conveyed by the fan 22 back to the blowing boxes. According to Figure 3, the web W to be dried, typically a pulp web, runs horizontally through the web gap 25. The track spacing 10 92421 25 is delimited from below by lower boxes 30 which are evenly spaced in the same horizontal plane and from above by straight blow boxes 40 which are evenly spaced horizontally. Blowing boxes 30 generally weighing webs W (wet pulp web weight can be up to ~ 2000 g / m2) are supported by blowing B2 and B3. Through the nozzle holes 42 in the horizontal lower walls of the direct blow boxes 40 vaa-5, blows Bj perpendicular to the plane of the web W are applied, with which the web W is dried above.

Figures 4, 6 and 8A and 8B show the more detailed structure of the lower boxes 30. In the middle of the bearing surface 31 of the lower boxes, there is thus a transverse groove 32 in the transverse direction of the track W, which 10 opens towards the track W. The opening angles of the V-shaped groove 32 are denoted by a. Said angle α is generally in the range α = 50 ° ... 90 °, preferably α = 60 ° ... 80 °. The sloping walls of the V-groove 32, which are preferably planar, pivot into the horizontal plane portion 34 of the bearing surface with a radius of curvature R at an angle b through the rounding portions 31b. As can be immediately seen from Figure 6, the connection between angles a and b is 15 a + 2b = 180 °. The sloping planar surfaces of the V-groove 32 each have rows of blow holes 33. These blow holes 33 are so arranged and oriented that the air jets B3 from them side bypass the rounding portions 31b between the planar surfaces, thereby reversing the air jets B3 to the plane portions 34 of the bearing surface 31. The blow holes 33 are on the opposite sides of the V-groove 32 in such a stepwise manner (Fig. 8), 20 that the blows B3 intersect in mutually opposite directions. Thus, some of the blows B3 are parallel to the path and its plane of the track W, while others of the blows are parallel to the plane of the track W and opposite to the path. According to the Bemoull principle, the blows B3 induce a vacuum zone between the track W and the bearing surface 31, which stabilizes the track W at a certain distance H from the bearing surface 31. Said distance H is generally of the order of H = 3-6 mm, whereby the air drying of the track W is generally at its most efficient.

On both edge areas of the bearing surface 31, lowered edge portions 35 are arranged along the length Lj parallel to its track, the height of which relative to the track W is less than the height of the central plane portions 34 of the bearing surface 31. According to Figure 6, said edge portions 35

II

92421 11 are inclined planar beveled portions, the distance of which at the edges of the nozzle box 30 with respect to the planar portions 34 is denoted by h2.

In the nozzle-blowing box according to the invention in the processing space 25 of the track W below the track W5, the air velocity is first substantially state in connection with the planar bearing parts 31, then the handling speed 25 is reduced stepwise or evenly to the edges and spaces 30a of the box 30. makes the heat transfer considerably more efficient, as will be seen later from the research results of Figures 9 and 10. The efficiency of the heat transfer 10 is largely due to the fact that with the reduced bearing portions 35; 35b; 35d; 35e the air flow velocity in the direction of the plane W is considerably reduced, which primarily enhances the heat transfer of the direct blows 1¼.

The lower box 30 and the direct blow box 40 of Figures 4 and 5 are aligned and opposed in the pulp dryer so that the surfaces 41 and 31 are substantially parallel to each other and generally horizontal to each other. The edges of the surfaces 41 of the direct blow boxes 40 may have rounding portions 43a and the edge portions of the carrying surface 31 of the lower boxes 30 may have corresponding rounding portions 31a.

Opposite surfaces 31 and 41 of both the lower box 30 and the direct blow box 40 are provided with nozzle perforations 42; 36. The preferred distribution of the perforation 36 of the blow box 30 is shown in Fig. 8. Through said perforations 36; 42, perpendicular blows Bj; B2 are applied against the track W, which promote the drying of the track W. As the air flow rate in the bearing surface portions 35 decreases due to the increase of the flow cross-section, the straight wood-25 halls B2 have a longer exposure time to the lower surface of the track W.

Fig. 8B schematically shows a preferred geometry and dimensioning example of the V-groove 32 described above. The geometry shown in Figure 8B is symmetrical with respect to the transverse vertical median plane K-K. The starting point for the design of the V-groove 32 is that the air jets F1 and F2 blown from opposite sides are made to sideways the rounding portions 31b associated with the edges of the groove 32 so that they turn parallel to the bearing surface 34 due to the Coanda effect 92421 12. Specifically, the distance between the groove 33 and the bearing surface 34 must be rounded so that air leaves to follow the bearing surface 34.

Figures 7A-7E show some alternative implementations of the carrying surface 5 of the blow box 30. The nozzle box 30A of Fig. 7A comprises a bearing surface 31 having planar portions 34 on both sides of the V-groove 32 and then planar inclined beveled portions 35.

Fig. 7B shows a particularly preferred blow box 30B having planar portions 34b on both sides of the V-groove 10 32 and then step portions 37 perpendicular to both the first planar portions 34b of the bearing surface and the subsequent planar plane portions 35b after the step portion 37. The initial portions 34b of the bearing surface 31 are parallel to each other and in the same horizontal plane. Correspondingly, the edge portions of the bearing surface 31 are parallel to each other and in the same horizontal plane. Fig. 7B 15 also shows a preferred dimensioning example of the nozzle box 30B. According to Fig. 7B, the height h2 = 10 mm of the step part 37. In general, the height of the step section can vary between h2 = 7 ... 15 mm.

Fig. 7C shows a nozzle box 30C with a completely planar bearing surface 31c for reference. This nozzle box 30C is not actually in accordance with the present invention and is shown here only for comparison, the results of which will become apparent from Figures 9 and 10, which will be described in more detail later.

Fig. 7D shows a blow box 30D according to the invention with relatively long planar bearing portions 34d and relatively short and steep, inclined edge portions 35d. Figure 7D also shows a preferred dimensioning example.

Fig. 7E shows an alternative modification of the blow box of Fig. 7B having relatively long planar bearing portions 34e and step portions 30 37 followed by relatively short bearing surfaces 35e. Fig. 7E also shows a structural example of said blow box 30E.

92421 13

Fig. 8A shows the mutual arrangement and staggering of the nozzle holes 33 of the V-groove 32 so that the opposite blows B3 are blown crosswise. The perforation 36 of the nozzle-bearing surface 31 is arranged in four successive rows so that the blows 1¼ and B3 do not coincide and interfere with each other. The mutual spacing of the nozzle holes 33 is generally in the range of 20 to 50 mm and the mutual spacing of the nozzle slots 36 in the transverse and machine directions, respectively, is generally in the range of 40 to 100 mm.

As for the dimensioning of the blow boxes shown in Figs. 6 and 7, the following can be stated with reference to the markings of Fig. 6. The angle α of the central V-groove 32 10 of the bearing surface is generally in the range a = 50 ° ... 90 °, the angle b of the Coanda surfaces 31b being in the range b = 45 ° ... 65 °. The height hj of the V-groove 32 is generally in the range hj = (2-5) x Φ, where Φ is the diameter of the nozzle holes 33 in the walls of the V-groove 32. The diameter Φ of the nozzle holes 33 is selected in proportion to the diameter of the direct blowing nozzles 36 of the bearing surface so that the air volume of the carrier blows B3 blown through the nozzle holes 33 is about 15 to 60%, preferably 35 to 45% of the total air volume of blows B2 and B3.

The length Lj of the sloping or stepped edge portions 35, 35b, 35d, 35e of the bearing surface 31 is selected to be (0.1-0.3) x L, preferably (0.2-0.25) x L, where L is the size of the blow box. 30 total machine direction length. Said length L is usually in the range L * 300 ... 500 mm. The height difference h2 20 of the oblique portions 35,35d or of the step portions 35b and 35e is selected from the range h2 = 7 ... 15 mm, preferably h2 «10 mm.

Figures 9 and 10 show graphically the test results of the nozzles of Figures 7A-7E. In Figs. 9 and 10, the vertical axis has a relative heat transfer coefficient aR and the horizontal axis the distance of the track W from the bearing surface 31, specifically from its planar portion 34. In Figs. 7A to 7E, the mark corresponds to curves A-E in Figs.

The nozzle described above was made in the versions of Figures 7A-7E, the heat transfer of which was examined in a static test apparatus by blowing hot air against a flat metal surface. The efficiency of heat transfer was obtained by measuring the heating rate of the plate 30 by means of temperature measuring sensors embedded in it. Figures 9 and 10 show the measured relative heat transfer coefficients aR as a function of the distance H 14,92421 between the track and the bearing surface 31 of the nozzle box at two different blowing speeds. According to the results, a drop ht of the edge portions 35; 35b; 35d; 35e gives an increase of the order of 5-10% in the heat transfer coefficient compared to a flat bearing surface (Fig. 7C, bearing surface 31c) when the distance H corresponds to the normal floating distance W (3-6 mm). . At greater distances H-5 la, the drop of the edge portions 35, on the other hand, no longer achieves a corresponding benefit. The increase was greatest for those nozzles with the most calculated lower edge portions 35; 35b of the bearing surface 31 (Figures 7A and 7B). The measurement results of Fig. 9 are obtained with the speed of blows 1¾ and B3 wpuh = 26 m / s and the results of Fig. 10 are obtained with the speed of blowing wpuh = 34 m / s with a blowing air temperature Tpuh of 10 Tpuh = 150 ° C, respectively. As can be seen from Figures 9 and 10, there are substantially large differences in the relative heat transfer coefficient aR precisely at the optimal fluidization distances of the track W H = 3-6 mm.

The simulation and measurement method used in the measurements of Figures 9 and 10 is described in more detail in P. Heikkilä 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 preferred embodiment of the invention is a blow nozzle box 30A according to Figure 7A, based on the current understanding and available measurement results. According to the measurement results of Figs. 9 and 10, the sharply staggered (37) bearing surface 34b, 35b of Fig. 7B is the best in terms of heat transfer, but the nozzle-blown box 30A with uniformly descending ramp-shaped bearing surface portions 35 of Fig. 7A is more advantageous because is smaller because the geometry of the blow surface does not include sharp angles. Thus, the nozzle-blow box 30A according to Fig. 7A (also dimensioned) according to the present assessment is the best embodiment of the invention in the case where e.g. the distance of the pulp web W from the horizontal part 34 of the bearing surface 31 is -5 mm.

30 92421 15

The following claims set forth within the scope of the inventive idea, the various details of the invention may vary and differ from those set forth above by way of example only.

5 «

Claims (16)

1. A method for air drying of webs, especially high-weight webs, such as cellulose webs, in which method air blasts (B2) are directed towards the web (W) from below which are perpendicular to them and air blasts (B3) having substantially the same direction as the web plane (W), with which blows (B2, B3) one transfers heat into the web (W) and performs a contact-free air support thereof and stabilizes its passage through the dryer, by which method one bends the air flow velocity in the direction of the plane of the airborne web (W) in connection with the nozzle surface (31) is substantially constant, after which the air flow rate is reduced at the edge regions (35; 35b; 35d; 35e) of said support surface (31) by using edge regions (35, 35b, 35e) of the nozzle support surface (31) which ramp-shaped and / or step-shaped in the air flow direction, characterized in that with said reduction a v the air flow rate substantially improves the heat transfer to the web (W) compared to a smooth carrier surface (FIG. 7C; 31c) and from the locking space (32) in the middle of the carrier surface, said blisters (B3) are blown crosswise in a manner known per se in the direction of the web (W) race which is opposite in relation thereto, from the nozzle openings (36). ) of the support surface, perpendicular blows 0¾) towards the web, whereby the action of the latter blows against the lower surface of the web (W) is extended by increasing the flow cross-section between the web and the support surface of the edge regions (35; 35b, 35d, 35e). and the carrier surface (31).
2. A method according to claim 1, characterized in that the method utilizes a plurality of nozzle blowers (30) to be placed below the web (W), the upper side of which forms a support surface (31) supporting the web (W). .
Method according to Claim 1 or 2, characterized in that on said step-shaped and / or ramp-shaped edge areas (35; 35b, 35d, 35e) of the nozzle support surface (31), the heat transfer from the drying air to the web (W) is optimized and controlled. the hover height (H) of the web (W) to be dried and supported relative to the nozzle support surface (31). 92421 22
Method according to any of claims 1-3, characterized in that the air blasts (B3) to be directed in a horizontal direction crosswise from the lock (32) in the middle of the nozzle surface (31) are directed substantially from their nozzle openings (33) to the curved guide surfaces (31b) in the bending surface of the nozzle surface (31), by which said blades (B2, F1, F2) are pivoted by relying on the Coanda effect at a given angle (b) in the direction of the planar initial members (34) of the carrier surface (31) and in the direction of the plane of the web (W) running adjacent thereto.
Method according to any one of claims 1-5, characterized in that the blowing air quantity of the stabilizing air blowers (B3) which stabilize and are to be directed along the support surface (31) in the direction of the plane of the web (W) is 30 ... 60 %, most preferably about 35 ... 45% of the total blowing air quantity of the nozzle blowing vane (30). 15
Method according to any one of claims 1-5, characterized in that said crosswise blisters (B3) to be directed in the direction of the carrier surface and the plane of the web (W) to be dried and supported are retarded on the edge area by the support surface of the nozzle leather. (30) with a length Lj in the direction of the race on the track (W), which is chosen Lj = (0.1-0.3) x L, most preferably Lj = (0.2-025) x L, where L is the the total length of the support surface (31) of the blower, which in turn is selected from the area L = 300 ... 500 mm.
Process according to any of claims 1-6, characterized in that the blowing air quantities of the nozzle blowing carriage (30) are removed from the drying and carrying distance (25) via the spaces (30a) between said nozzle blowing carcasses (30).
Method according to any of claims 1-7, characterized in that upper straight blowing carriages (30) are used opposite said blowing carriages (30) which are below the web (W) to be dried and supported, from which directional blows 30 ( Bj) which is substantially perpendicular to the plane of the web (W), the web (W) being dried on the bed sides (Figures 1, 2 and 3). 92421 23
9. Nozzle blower (30) for an air dryer, through which air blasts (B2, B3) are directed to the blanket web (W) to be dried, thereby providing bed heat transfer from the drying air to the web (W) and a contact in air support thereof. and a stabilization of its race, and which nozzle blowing carriage (30) comprises a cover portion, wherein there is a nozzle support surface (31) which meets the web (W), in the middle of which a carrier surface is a substantially V-shaped spar (32) is transverse in relation to the running direction of the web (W), which bar opens to the web (W) and in whose opposite walls there are series of nozzle heels (33) in such a way that crosswise and opposite directed support and stabilizing air blasts can be directed. from said nozzle health series (33), and in which nozzle support surface (31) are planar nozzle support surfaces (34) which are mutually in the same pane on both sides of its V-lock (32), characterized characterized in that the extension of said nozzle support surfaces (34) consists of step-shaped and / or ramp-shaped support surfaces (35; 35b, 35d, 35e) which are further away from said web (W) to be supported, on which the speed of said supporting and stabilizing air streams is reduced in proportion to that traveling in connection with the planar nozzle surfaces (34), and that there is a nozzle perforation (36) in the nozzle surface (31) through which nozzle blades ( moreover, substantially perpendicular blasts (B2) may be directed relative to the plane of the blank web (W) to be supported.
A nozzle blower according to claim 9, characterized in that there are curved Coanda guide surfaces (31b) extending to both planar walls of said V-latch (32), which control surfaces continue steplessly as planar parts (34) of the support surface (31). ), and that the nozzle heels (33) in the walls of said V-lock (32) are so arranged that the main direction of the air jets (B3) to flow out therefrom is substantially tangential to the curved Coanda guide surface (31b) opposite it.
The nozzle blower according to Claim 9 or 10, characterized in that the mutual angle (a) of the plane walls of said V-bar is within the range a = 50 ° -90 °, and that the depth h, of said V -sphere hj = (2-5) x Φ, where Φ is the diameter of the nozzle heel of walls of said V-bar (32).
Nozzle blower according to any of claims 9-11, characterized in that said step-shaped and / or ramp-shaped submerged edge portions (35; 35b, 35d; 35e) of the nozzle support surface (31) of the nozzle blower are of the length thereof. L1 which is in the direction of the path of the blank (W), selected in such a way that L1 = (0.1-0.3) x L, most preferably L1 (0.2-0.25) x L, where L = the total length in the direction of the web race (W) of the nozzle blowing carriage (30), which length is selected in the range 10 L = 300 ... 500 mm, and that the maximum height difference (h2) between the edge area (35) of said support surface and said slab (34) of the nozzle surface (31) is selected within the range h2 = 7 ... 15 mm, most preferably h9 «10 mm.
Nozzle blower according to any of claims 9-12, characterized in that the nozzle heels (33) of said V-lock (32) are substantially evenly distributed in the walls opposite the V-lock, which distribution is selected in the area. 20 ... 50 mm and that the perforation (36) of said support surfaces (31) is stepped relative to the above mentioned nozzle heel (33) and in the running direction of the web (W) in 3-5 transverse rows of bed in the direction of the web (W). and in the transverse direction substantially evenly distributed, which distribution is selected within the range of 40..100 mm.
A cellulose dryer for applying nozzle blowing trays (30) according to any one of claims 9-13, through which air blasts (B9, B3) are directed to the cellulose web (W) to be dried, with which blasts provide heat transfer from the drying air to the the cellulose web (W) and a contactless air support thereof and a stabilization thereof, and which nozzle blowing lugs (30) comprise a sleeve portion, wherein there is a nozzle support (31) which meets the cellulose web (W), in the middle of which the carrier surface is provided. substantially V-shaped latch (32) which is transverse in relation to the running direction of the cellulose web (W), which latches open to the web (W) and in whose opposite walls are series of nozzle heels (33) in such a way that they cross each other and opposite directed support and stabilizing air blasts can be directed from said nozzle health series (33), and in which nozzle support surface (31) is planar -shaped nozzle supports (34) which are mutually in the same tab on both sides of its V-latch (32), characterized in that the extension of said nozzle supports (34) consists of step-shaped and / or ramp-shaped surfaces (35; 35b, 5d). , 35e) which is further away from the cellulose web (W) to be supported, in whose area the velocity of said supporting and stabilizing air flows is reduced relative to that of the planar nozzle bearing surfaces (34), that there is a nozzle perforation (34). 36) in the nozzle carrier surface (31), through which one can direct from substantially the nozzle blower (30) substantially perpendicular blows (B2) relative to the plane of the cellulose web (W) to be supported, that the cellulose tray comprises multiple nozzle blows (30). , which are at a horizontal distance (30a) from each other, through whose intervals (30a) the air carrying, drying and stabilizing the cellulose web (W) is substantially removed. It is assumed from the treatment spaces (24) that there are several of said nozzle blowing trays (30) one after the other in the running direction of the web (W) in the same horizontal direction and that there are several rows of said nozzle blowing trays (30) after each other in such a way that the cellulose web (W 2 -Wout) to be dried runs through the dryer carried by air inside the hood (13) of the cellulose dryer in the form of straight-ahead reciprocating and interconnected races between which the blank web (W) pivots in the opposite direction with break rollers (13). 20
Cellulose dryer according to claim 14, characterized in that opposite said nozzle blowing trays (30) are direct blowing trays (40) above the cellulose web (W), whereby via the nozzle openings or slots of the plane surface (41) which are opposite the cellulose web ( towards said cellulose web (W), and that between said direct-blowing trays (40) there are intermediate spaces (40a) through which the Upper Blowing Air (Bj) is transmitted.
Cellulose dryer according to claim 15, characterized in that the lower nozzle blowing voids (30) of the cellulose web (W) and direct blowing nozzles 30 (40) against them are in the running direction of the cellulose web (W) mutually equal and evenly distributed (3). ).
FI921193A 1992-03-19 1992-03-19 Method for Air Drying of Substances, Nozzle Blower for an Air Dryer and Cellulose Dryer FI92421B (en)

Priority Applications (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 of Substances, Nozzle Blower for an Air Dryer and Cellulose Dryer

Applications Claiming Priority (10)

Application Number Priority Date Filing Date Title
FI921193A FI92421B (en) 1992-03-19 1992-03-19 Method for Air Drying of Substances, Nozzle Blower for an Air Dryer and Cellulose Dryer
ES93103768T ES2159510T3 (en) 1992-03-19 1993-03-09 Air-drying procedure, free of contact, of a band of material, as well as a blower box by towels and a paper pasta dryer where such procedure is used.
AT93103768T AT203071T (en) 1992-03-19 1993-03-09 Method for air drying free-moving materials and air dryers for carrying out the method
DE1993630413 DE69330413T2 (en) 1992-03-19 1993-03-09 Method for air drying free material webs and air dryer for carrying out the method
EP19930103768 EP0561256B1 (en) 1992-03-19 1993-03-09 Method for contact-free air-drying of a material web and air dryer that makes use of the method
BR9301228A BR9301228A (en) 1992-03-19 1993-03-18 Air drying process of material floors, blow box with nozzles and pulp dryer
CA 2092004 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
KR1019930004138A KR0172974B1 (en) 1992-03-19 1993-03-18 Method for non-contacting air drying of web material and nozzle blow box and pulp dryer by means of said method
CN 93104033 CN1031656C (en) 1992-03-19 1993-03-19 Method in contact-free air-drying of a material web as well as a nozzle-blow-box and as pulp dryer that make use of the method
JP08388893A JP3305802B2 (en) 1992-03-19 1993-03-19 Non-contact air drying method for web material, nozzle blowing box and pulp dryer by the method

Publications (3)

Publication Number Publication Date
FI921193A0 FI921193A0 (en) 1992-03-19
FI921193A FI921193A (en) 1993-09-20
FI92421B true FI92421B (en) 1994-07-29

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FI921193A FI92421B (en) 1992-03-19 1992-03-19 Method for Air Drying of Substances, Nozzle Blower for an Air Dryer and Cellulose Dryer

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EP (1) EP0561256B1 (en)
JP (1) JP3305802B2 (en)
KR (1) KR0172974B1 (en)
CN (1) CN1031656C (en)
AT (1) AT203071T (en)
BR (1) BR9301228A (en)
CA (1) CA2092004C (en)
DE (1) DE69330413T2 (en)
ES (1) ES2159510T3 (en)
FI (1) FI92421B (en)

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CA2092004C (en) 1998-05-19
JPH06248593A (en) 1994-09-06
DE69330413T2 (en) 2002-06-20
JP3305802B2 (en) 2002-07-24
EP0561256B1 (en) 2001-07-11
KR930019930A (en) 1993-10-19
FI921193A (en) 1993-09-20
EP0561256A1 (en) 1993-09-22
CA2092004A1 (en) 1993-09-20
CN1031656C (en) 1996-04-24
BR9301228A (en) 1993-09-21
DE69330413D1 (en) 2001-08-16
ES2159510T3 (en) 2001-10-16
FI921193D0 (en)
FI921193A0 (en) 1992-03-19
KR0172974B1 (en) 1999-03-30
CN1081485A (en) 1994-02-02
AT203071T (en) 2001-07-15

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