DE29703627U1 - Device for sealing a steam blow box - Google Patents

Description

Voith Sulzer Papiermaschinen GmbH *File: PA 10278 D-89509 Heidenheim "DBK-Sealing" Device for sealing a steam blower box Description

The invention relates to a steam blower box according to the preamble of claim 1 and claim 8.

Steam blow boxes are known in many different forms from patent documents and other publications in the technical literature.

The invention is based on the not yet published patent application 195 34 573.8.

Such a steam blower box is used to increase the temperature of the material web using steam applied to it in order to increase the dewatering performance of the press section. The steam blower box offers the possibility of influencing the moisture cross-section of the material web by applying steam differently in each section. Another application of the steam blower box is, for example, in the drying section of a paper machine. The application of steam - which can also vary across the width of the fibrous web - also influences the moisture cross-section.

In order to use such a steam blower box effectively, the fibrous web faces the steam blower openings of the blower box directly. In other words: The surface of the fibrous web is not covered by a drying screen or felt, for example. Since the fibrous web is very sensitive to mechanical contact, a contactless seal must be made between the steam blower box and the moving material web. This has the disadvantage that steam can escape between the steam blower box and the fibrous web. These steam clouds represent a loss of condensation heat energy on the fibrous web and thus reduce the drying performance. But even without condensation of the

Steam clouds can impair drying performance, e.g. by increasing the relative humidity in the drying section to such an extent that drying performance is also reduced.

The invention is therefore based on the object of creating a device with which the escape of leakage steam can be prevented better than before.

This problem is solved by the characterizing part of claim 1.

There is an excess pressure between the fibrous web and the steam blower box compared to the atmospheric pressure. As a result, the steam wants to escape through the sealing gap. The translatory movement of the fibrous web entrains a boundary air layer. This boundary air layer must be removed from the fibrous web so that the steam in the blower box can act directly and undisturbed on the web. The inventor has recognized that by simultaneously applying a steam and a parallel air flow using a double slot nozzle, a barrier front can be built up between the steam masses of the steam blower box and the ambient air, whereby the two partial flows essentially do not mix. The application of this invention to the steam blower box is as follows: The steam flow is closer to the interior of the steam blower box than the air flow. When the two sandwich-like flows hit the fibrous web, they split up into individual flows again. The steam flow is diverted towards the steam-filled room and the air flow is diverted towards the ambient air. The air flow can then flow out via a separate channel or, depending on the flow conditions, be extracted to assist. This arrangement achieves a good separation of the different air masses.

A separation of steam and air can be achieved by a suitable choice of the flow speeds of the air and steam flow and/or by a suitable alignment of these two parallel slot nozzles to the fiber web.

A further problem exists in the section of the fibrous web following the steam-exposed zone.

After a fibrous web has left the area of influence of the steam blower box, it still gives off some steam. This means that not only the steam blower box can cause steam clouds, but also the fibrous web itself. Even if these steam masses are generally smaller than the possible leakage losses at the steam blower box, they still represent a problem in the drying section and in the press section.

The invention is therefore based on the object of creating a device that captures the vapor clouds of the evaporating web as far as possible.

This problem is solved by the characterizing part of claim 8.

In order to capture these quantities of steam so that they do not wander around the paper machine in an uncontrolled and, above all, disruptive manner, the inventor has found another solution. An ejector nozzle in the outlet area of the fibrous web from the steam blower box sucks a shielded area of the fibrous web. Steam is applied to this ejector nozzle. Operating the ejector nozzle with steam has the advantage that the steam vapors and the steam from the ejector nozzle can be directed into the interior of the steam blower box without significantly "contaminating" the steam inside the steam box. Only a small amount of ambient air is sucked into the evaporation chamber using this method. The ejector nozzle is set in such a way (through flow speed and inclination towards the fibrous web) that the cooling limit temperature is not undercut.

The solution described in the characterizing part of claim 8 is also applicable independently of that in the characterizing part of claim 1, e.g. in combination with the subject matter of German patent application 195 34 573.8.

The invention is explained in more detail with reference to the drawings. The following is shown in detail:

It shows

Figure 1 is a side view of a section of a paper machine in the press section area;

Figure 2 shows a section of Figure 1 as a partial section; Figure 3 shows the section A-A from Figure 2.

Figure 1 shows an example of the installation of the steam blower box 50 according to the invention in the press section. The fibrous web 1 is sucked from the former onto the outside of a felt 2 of the press section using the suction roller 18.

The fibrous web 1 passes through a press nip formed by the roller 30 and an opposite roller. Viewed in the web travel direction 2 6, the web now passes through the area of the steam blower box 50, after which the web passes through another press nip between the rollers 30 and 32. After another press nip between the roller 32 and a counter roller, the web is removed from the roller 32 and fed to other units.

Structural details of the steam blower box according to the invention can be clearly seen in Figure 2. The location of use of this steam blower box is in the press section. The fibrous web 1 lies on the outside of the dewatering belt 2 and partially wraps around the roller 30. The boundary air layer 14 is at least partially deflected here by a deflector 9 and passed on through the outer wall 3 of the steam blower box. The slot-shaped steam nozzle 7 is supplied via a steam supply 11. The slot-shaped nozzle 8 is supplied via an air supply 12. These two flows split when they impact the fibrous web 1.

The air flow is directed against the web travel direction 26, possibly with the aid of guide elements 10, to the discharge line 13.

In order to support this discharge 13, it can be vacuumed. Inside the steam blower box 50 there is a wall 5 provided with openings 4. Between this wall 5 and the fibrous web 1 there is the so-called blowing chamber β. Here the fibrous web is heated up.

At the end - seen in the direction of web travel 26 - of this blowing chamber there is a discharge line 19. The steam is again discharged from the steam blowing box 50 via this discharge line 19. A cover 15 encloses part of the area following the steam blowing box 50. In this application example, the cover 15 preferably extends very close to the gusset between the rollers 30 and 32. The so-called evaporation chamber 17 extends between the cover 15 and the fibrous web 1. The slot-shaped ejector nozzle 16, which is supplied with steam, sucks this evaporation chamber 17. The steam masses from the ejector nozzle 16 and the evaporation chamber 17 flow via the discharge line 19 back to the fresh steam preparation (not shown here).

The front seal of the steam blower box 50 according to the invention is shown in Figure 3. Here, too, the double nozzle 7, 8 is used again. The steam nozzle 7 is supplied via the steam supply 11. The air nozzle 8 is supplied via the air supply. The deflected air flow is directed into the discharge line 13 with the possible assistance of guide elements 10. The outer wall 3 has a defined distance in the direction of the roller axis. This ensures that if the fibrous web 1 and/or dewatering belt 2 runs away, no damage occurs to the web 1.

For example, the arrangement of the openings 4 in the wall 5 is also shown here. However, this arrangement can also be done in a completely different grid in order to increase the heating of the fiber web 1.

Claims (11)

Voith Sulzer Papiermaschinen GmbH ** "Äk*te:**PA* 10278 D-89509 Heidenheim "DBK-Seal" Device for sealing a steam blower box Protection claims 1. Steam blow box (50) in a paper machine for applying steam to a running fibrous web (1) {paper or cardboard web) with the following features: the steam blower box (50) extends transversely to the web running direction (26) essentially over the entire width of the fibrous web (1); the fibrous web (1) is blown with steam through openings (4) in the wall (5) of the steam blower box (50) facing the fibrous web (1); the blowing chamber (6) is sealed contactlessly in the direction of the fibrous web (1); characterized in that the blowing chamber (6) is at least partially sealed by a slotted double nozzle (7,8). 2. Steam blow box (50) according to claim 1, characterized in that the blow chamber (6) is sealed transversely to the web running direction (26) with a slotted double nozzle (7, 8). 3. Steam blow box (50) according to one of claims 1 or 2, characterized in that the blow chamber (6) is sealed at least on one side along the web travel direction (26) with a slotted double nozzle (7, 8). 4. Steam blower box (50) according to one of claims 1 to 3, characterized in that the steam blower box (50) is associated with a roller (30) which is supported by a dewatering belt (2) and the fibrous web (1) resting on it. 5. Steam blower box (50) according to one of claims 1 to 4, characterized in that the steam blower box (50) is associated with a substantially flat dewatering belt (2) and the fibrous web (1) resting on it. 6. Steam blower box (50) according to one of claims 1 to 5, characterized in that the double nozzle (7, 8) is assigned a discharge line (13) in the direction of the ambient air. 7. Steam blower box (50) according to claim 2, characterized in that a deflector (9) is attached to the outside of the steam blower box (50) at the inlet point of the fibrous web (1) into the steam blower box (50). 8. Steam blower box (50) in a paper machine for applying steam to a running fibrous web (1) (paper or cardboard web), in particular according to claim 1 with the following features: the steam blower box (50) extends transversely to the web running direction (26) essentially over the entire width of the fibrous web (1); the fibrous web (1) is blown with steam through openings (4) in the wall (5) of the steam blower box (50) facing the fibrous web (1); the blowing chamber (6) is sealed contactlessly in the direction of the fibrous web (1); characterized in that the blowing chamber (6) - viewed in the web travel direction (26) - is sealed at the end of the blowing chamber (6), transverse to the web travel direction (26), by a slot ejector nozzle. 9. Steam blower box (50) according to claim 8, characterized in that the steam blower box (50) is associated with a roller (30) which is partially wrapped by a dewatering belt (2) and the fibrous web (1) resting on it. 10. Steam blower box (50) according to one of claims 8 or 9, characterized in that the steam blower box (50) is associated with a substantially flat dewatering belt (2) and the fibrous web (1) resting on it. 11. Steam blower box (50) according to one of claims 8 to 9, characterized in that the slot ejector nozzle has a cover (15) which delimits the evaporation chamber (17).