EP1531197A1 - Steam box - Google Patents

Abstract

The housing wall (4) facing the paper (2) features steam exit openings (5), arranged into at least two separate groups. A vapor-free zone is provided between two adjacent groups of steam openings and the air carried along by the length of paper is removed through this zone. Each group has the shape of an arrow. The steam blowing chamber (3) is supplied with steam via a steam valve (6).

Description

The invention relates to a steam blower box for applying steam a passing material web, in particular paper, with a transversely to the Web running direction extending, the material web facing housing wall, in which a plurality of steam outlet openings is formed.

In papermaking or finishing, the running web becomes frequent steamed. The goals of this steaming are different, In all cases, however, one endeavors, the steam applied as possible to condense precisely on or in certain areas of the web and so on Transfer heat and / or moisture to the web. different Condensation quantities across the web allow a targeted influence certain properties (e.g., gloss, smoothness, etc.) and hence profiling the railway or eliminate unwanted differences in these properties across the track.

A maximum efficiency of the evaporation is only at ideal Reached conditions, i. if no additional heat transfer resistance between the steam and the railway is present. However, this ideal condition is barely given. Although this is not the case with a moving web to heat exchangers or boilers of the heat transfer resistance due to the resulting condensate film because of this constantly out of the way the vaporization area is conveyed out. But the steam room on A moving web is normally not only filled with steam. By train As a result of friction, an air film is constantly conveyed into the evaporation zone. This air enters with the steam in energy exchange. A part of the steam condenses in the air instead of the train and therefore can no longer contribute to desirable warming and moisture accumulation of the web. moreover The heated and water-enriched air is supersaturated on cooling and excrete water droplets. The resulting swathing worsens the indoor climate and causes dripping on machine parts. The main drawback of air presence is therefore deterioration the efficiency of the evaporation. Because the air film parts of the web against shields direct steam contact, generally occurs only part of the Path within the vaporization area in direct heat exchange with the steam.

To overcome this disadvantage, so-called "high-speed steam blow boxes" have already been used. proposed. This will be the steam jets deployed in such a high speed that at the impact points on the web the air is displaced from the railway surface, and a direct contact steam is created by rail. This must be the impact of the steam jet depending on the web speed a corresponding back pressure produce. At high web speeds and reasonably large outlet openings you reach the required back pressure with the outflowing Steam, however, only with amounts of steam that the absorption capacity of the web in the Usually exceed. With a relatively low steam requirement (for example when steaming of paper webs for smoothness increase on calenders) must therefore with much too large excess of steam can be worked to the desired condition to get close. It is also often forced to surplus To suck vapor, on the one hand high suction power is required and On the other hand, there is the danger that you can by unintentional suction of Steam shares deteriorated the efficiency of the vapor deposition.

From DE 37 01 406 C2 special sealing zones are known, with which the direction of the steam jets has a blocking effect on both sides of the vapor deposition area should be achieved. The injector action of the Steam jets extracted air is deliberately accepted and for the sealing effect used. A separation of air and steam does not do that.

DE 44 01 220 C 1 describes a steam blower box, in which by a Sectionally different vapor deposition the moisture profile of the web can be influenced. The sectioned zone chambers used for this are each with a separate steam line and a control valve with connected to the steam distributor. The common steam outlet plate points several rows of blowing openings. These rows of blow holes are arranged in the steam outlet plate obliquely to the direction of the web. The steam outlet is directed against the material direction. With this Steam box, it is possible, the web across the direction of travel Steam in blocks.

The object of the present invention is to propose a steam blower box, in which the steaming area is essentially kept free of air becomes.

This object is achieved in a steam blower box of the type mentioned According to the invention solved in that the steam outlet openings to at least two separate groups are summarized, and that at least a vapor-free section is provided between two adjacent groups is, through which dissipates the entrained air from the web becomes.

By blockwise staggered arrangement of the steam outlet openings in the For example, formed as a profile perforated sheet housing wall is the entrained air Passing the vaporization areas. Similar to the effect of a tire tread when wet, the air is moved marginally to the side, so that the Steam in the steaming area directly and therefore with higher efficiency or can condense in the web. The vapor-free section between the adjacent steam outlet opening groups acts like a channel, passing the air past the vaporization areas.

According to a preferred embodiment of the invention, this is in the web running direction front (upstream) and / or rear (downstream), through adjacent steam outlet openings formed end of a group diagonally to the web running direction. Due to the oblique orientation of the steam outlet openings the angle of impact of the air on the evaporation area decreases. The change of direction required for the deflection of the air is low, and the air is easy, even and effective to distract.

According to the invention, in this case the front and / or rear side of the group is at least partially at an angle α in the range of 30 to 60 °, preferably 45 °, inclined to the web running direction. The airflow then hits in this Angle α on the emerging from the steam outlet openings steam flow. The back pressure of the air decreases in proportion to tanα, since the pent-up Air can flow freely sideways to the web direction. This will be especially true then achieved when the inclination of the front edge of the evaporation zone so large is that the rear end of the front vaporization limit in the direction of the web of a steaming area still clearly behind the front End of the rear bedampfungsgrenze of the adjacent Bedampfungsbereiches lies.

The desired influence on the flow conditions in the evaporation zone is particularly easy to implement, if according to the invention each Group essentially the shape of an arrow or a parallelogram having. In the latter case, then two of the four can be arranged side by side Steam outlet openings formed sides of a group parallel to Web running direction, so that no deflection takes place in this area.

In a preferred embodiment, adjacent groups are in the web running direction arranged offset to each other, so that the air flow in several Stages is deflected. This creates cross-web evaporation areas at one point and vapor-free areas. Continue in the direction of the train At the back, the previously vapor-free areas are steamed.

To ensure a simultaneous and even deflection across the entire width of the To ensure Dampfblaskastens, this is preferably every other Group arranged in the web running direction at the same height.

In a further development of the invention, a group is arranged so that they over a portion of their length in the web running direction directly to an adjacent group borders. As a result, the width of the steam blow box can be reduced.

As in the first embodiment, separate channels are formed, so that the air is redirected controlled in a certain direction. Turbulences are largely avoided.

It is also advantageous within a group at least one area without Form steam outlet openings.

In development of this inventive concept it is provided that the edges the respective groups through continuous rows of steam outlet openings be formed to prevent entry of air and associated turbulence to avoid.

The number of total provided steam outlet depends in particular of the amount of steam to be applied and the web speed from, with the distribution within the respective groups evenly or unevenly can be.

Finally, the steam blower can transversely to the web running direction in a plurality be separated separately controllable zones, the cross-sectional control the Allowing different amounts of steam allow. Each zone can do this have at least one group with steam outlet openings, so that the Coating areas coincide with the transverse to the web zones arranged.

At the limits of the control zones it can be due to the lateral air currents and associated displacement of the steam jets or increased condensation from steam at the boundary to the air to strips of reduced vapor deposition come. This is inventively remedied by the Zone dividing walls are not arranged exactly in the direction of the web, but also be inclined to the web direction, preferably in the same sense and extent as the boundaries of the vaporization areas. This creates coverages These evaporation areas, which compensates for the described effect can be.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawing. Here are all described and / or illustrated features alone or in any combination the subject matter of the invention, regardless of their summary in the Claims or their dependency.

Fig. 1

einen Schnitt durch einen erfindungsgemäßen Dampfblaskasten;

Fig. 2

eine Teilansicht (X) eines Profillochbleches des Dampfblaskastens gemäß Fig. 1;

Fig. 3

eine Teilansicht (X) eines Profillochbleches gemäß einer zweiten Ausführungsform der Erfindung;

Fig. 4

eine Teilansicht (X) eines Profillochbleches gemäß einer dritten Ausführungsform der Erfindung;

Fig. 5

eine Teilansicht (X) eines Profillochbleches gemäß einer vierten Ausführungsform der Erfindung.

Show it:

Fig. 1

a section through a steam blower box according to the invention;

Fig. 2

a partial view (X) of a profile hole plate of the steam blower box of FIG. 1;

Fig. 3

a partial view (X) of a profiled hole plate according to a second embodiment of the invention;

Fig. 4

a partial view (X) of a profiled hole plate according to a third embodiment of the invention;

Fig. 5

a partial view (X) of a profile hole plate according to a fourth embodiment of the invention.

A steam blower box 1 is, for example, for vapor deposition of a material web, in particular a paper web 2, on a calender (not shown) used in which the web for improving the gloss and smoothness properties or passes through several nips. The web 2 is in this case in the direction of Arrow Y passed the steam blower box 1 and supplied with steam.

The steam blower box 1 has a steam blast chamber 3 with one of the paper webs 2 facing housing wall 4, in which a plurality of steam outlet openings 5 is formed. The steam chamber 3 is about a Steam valve 6 is supplied with steam and passes it through the steam outlet openings 5 on the paper web 2 from, on which it condenses and their temperature and moisture increased before treatment in the nip of the calender. In that regard, the steam blower box 1 does not differ from conventional Steam blow boxes as they are described, for example, in DE 37 01 406 C2.

The fundamental difference of the steam box 1 to the state of Technology is in the design of the paper web 2 facing housing wall 4th

The housing wall 4, 4 ', 4 ", 4"' shown in partial plan view in FIGS. 2 to 5 is designed as a profiled perforated sheet with the steam outlet openings 5. The steam outlet openings 5 are combined to form a plurality of (four exemplified) groups 5a to 5d. In FIGS. 2, 3 and 5, the groups 5a to 5d are each in the form of a parallelogram. Here are the front in the web direction, formed by steam outlet openings 5 sides 7 _{1 of} the groups 5a to 5d as well as the rear sides 7 ₂ each inclined at an angle α relative to the web running direction, while the adjoining lateral sides 7 ₃ , 7 _{4 of} the groups 5a to 5d are arranged parallel to the web running direction. In contrast, in the embodiment shown in Fig. 4, the groups 5a to 5d are formed in the shape of an arrow or wedge.

The groups 5a to 5d are offset from one another and form between vapor-free sections 8a to 8c.

In the individual groups 5a to 5d, the steam outlet openings 5 can be arranged evenly distributed. Alternatively, areas 9, 10 may be provided without steam outlet openings 5 (cf., FIG. 3), wherein the areas 9, 10 should be surrounded on all sides by at least one row of steam outlet openings 5. At the front and rear sides 7 ₁ , 7 _{2 of} the groups 5 a to 5 d preferably several rows of steam outlet openings 5 should be provided in succession in order to apply the required amount of steam can.

As a result of the staggered arrangement of the groups 5a to 5d, channels 11 or 11a and 11b are formed between the groups, by means of which the air entrained by the material web 2 is deflected in a targeted manner and past the vapor deposition regions (groups 5a to 5d). In FIGS. 3 to 5, the arrows show the course of the air entrained between the perforated plate 4 and the material web 2. Due to the oblique arrangement of the front sides 7 _{1 of} the groups 5a to 5d, the deflection is supported. So that the channel cross-section remains largely constant and no constrictions lead to turbulence of the air, the rear sides 7 _{2 of} the groups 5 a to 5 d are inclined at a corresponding angle.

In the embodiment shown in Fig. 2, the groups 5a to 5d are transverse to the web running direction offset from one another in such a way that between adjacent Groups 5a to 5d each have a vapor-free section 8a to 8c is formed. The front steam outlet openings 5 are here in one Angle of approximately 45 ° obliquely arranged to the web running direction.

In the second embodiment shown in Fig. 3, the deflection takes place gradually. Here, the groups 5a to 5d are offset in the web running direction arranged to each other, so that stepped vapor-free sections 8a, 8b be formed, through which the air is discharged. The neighboring ones Groups 5b and 5c adjoin each other in regions, so that between this air can not pass through. In this embodiment, the front Steam outlet openings 5 at an angle of approximately 30 ° obliquely to the web running direction arranged.

In the embodiment shown in Fig. 4, the groups 5a to 5d are designed in the form of arrows. When the entrained air of the paper web meets the arrowheads 13, it is divided into two air streams and on the two sides of the arrow 14 ₁ and 14 _second past. The arrow sides 14 ₁ and 14 ₂ are opposite to each arranged at an angle of approximately 45 ° obliquely to the web running direction. The arrow sides of the rearward arrows (groups 5a and 5c) may also be steeper, eg at an angle of 60 °, than the arrowheads of the forward arrows (groups 5b and 5d).

In the embodiment shown in Fig. 5, the groups 5a to 5d in the same Manner formed as simple parallelograms as in the embodiment according to FIG. 2. In contrast to FIG. 2, however, the groups are in FIG Web running direction arranged offset. This allows the air to drain even easier become.

Now meets the entrained by the paper web air to the vapor stream in the evaporation zone (Steam outlet 5), so the pent-up air deflected laterally, introduced into the channels 11 and between the Bedampfungszonen passed through, essentially without disturbing the evaporation. The exact shape of the air ducts can be changed by changing the shape and arrangement of groups 5a to 5d are varied. In the drawing, the groups are 5a to 5d formed as equal-sized parallelograms or as arrows. It is for the groups but also other forms such as wedges conceivable with those suitable Channels can be formed.

The steam blower box 1 can have several separately controllable transversely to the web direction Zones 12a to have 12 d, wherein each of the zones at least one group 5a to 5d of steam outlet openings. This can be as needed Moisture and / or temperature profile across the direction of travel on the paper web be applied.

Due to the special arrangement of the steam outlet openings 5 in the invention Profile perforated plate 4 is the mitbeförderte with the web 2 air film simply and effectively diverted past the sputtering areas. Thereby the vaporization areas of air are kept almost free and the discharged Steam can condense directly on or in the material web. Consequently ensures high heat and moisture transfer to the web. The efficiency of the steam blow box is increased accordingly.

LIST OF REFERENCE NUMBERS

1

steam blow

2

web

3

steam blow

4

Housing wall (perforated plate)

5

Steam outlet opening

5 a-d

Group of steam outlet 5

6

steam valve

7 ₁ -7 ₄

Page of Group 5 a-d

8 a-c

vapor-free section

9, 10

Area without steam outlet

11 a, b

channel

12 a-d

control area

13

arrowhead

14 ₁ , 14 ₂

arrow side

Claims (14)

Steam blow box for applying steam to a passing material web (2) with a housing wall (4), which extends transversely to the running direction and faces the material web (2), in which a plurality of steam outlet openings (5) are formed,
characterized in that the steam outlet openings (5) are combined to form at least two separate groups (5a to 5d),
and
that at least between two adjacent groups, a vapor-free section (8a to 8c) is provided, through which the air entrained by the material web (2) is removed. Steam blower box according to Claim 1, characterized in that the side (7 ₁ ) of a group (5a to 5d) formed at the front in the web running direction and formed by juxtaposed vapor outlet openings (5) runs obliquely to the web running direction. Steam blower box according to claim 1 or 2, characterized in that the rear side (7 ₂ ) of a group (5a to 5d) extends obliquely to the web running direction. Steam blower box according to one of the preceding claims, characterized in that the front and / or rear side (7 ₁ , 7 ₂ ) of a group (5a to 5d) at least partially at an angle α of 30 to 60 °, preferably 45 °, relative to the Web running direction is inclined. Steam blower box according to one of the preceding claims, characterized in that the steam outlet openings of each group (5a to 5d) together form substantially the shape of an arrow. Steam blower box according to one of claims 1 to 4, characterized in that the steam outlet openings of each group (5a to 5d) together form substantially the shape of a parallelogram. Steam blower box according to claim 6, characterized in that the lateral sides (7 ₃ , 7 ₄ ) of a group (5a to 5d) extend parallel to the web running direction. Steam blower box according to one of the preceding claims, characterized in that adjacent groups (5a, 5b; 5c, 5d) are arranged offset from one another in the web running direction. Steam blower box according to claim 8, characterized in that , transverse to the web running direction, every other group (5a, 5c, 5b, 5d) is at the same height in the web running direction. Steam blower box according to one of the preceding claims, characterized in that a group (5b, 5c) over a part of its length in the web running direction directly adjacent to an adjacent group (5c, 5b). Steam blower box according to one of the preceding claims, characterized in that within a group (5a to 5d) at least one region (9, 10) without steam outlet openings (5) is provided. Steam blower box according to claim 11, characterized in that the region (9, 10) without steam outlet openings (5) is surrounded on all sides by at least one row of steam outlet openings (5). Steam blower box according to one of the preceding claims, characterized in that the steam blower box (1) is divided transversely to the web running direction into a plurality of separately controllable zones (12a to 12d), each zone (12a to 12d) comprising at least one group (5a to 5d) having steam outlet openings. Steam blower box according to claim 13, characterized in that between the zones (12a to 12d) zone dividing walls are arranged and that the zone dividing walls are arranged obliquely to the web running direction.

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