WO1996022420A1 - Device for applying steam - Google Patents

Abstract

A device for applying steam to a paper web has a steam box (48) with numerous zone chambers arrayed in succession over the width of the web. The steam box (48) is movable and so the distance between it and the web run can be adjusted. From each zone chamber a steam feed line (4) extends in the longitudinal direction through the interior of the steam box and from there outward up to a support plate (28). There the clearance between adjacent steam lines is substantially greater than within the steam box. For each zone chamber there is a steam control valve (35) situated laterally off the paper machine and connected to the support plate (28) by a flexible line (29).

Description

 Device for applying steam

description

The invention relates to a device for applying steam to a running material web, e.g. onto a paper web to be dewatered and running through the press section of a papermaking machine. Such a device primarily includes a steam blower box. Reference is made to the published patent application DE 41 25 062 AI.

Such a steam blow box is mainly used in papermaking. It is used to increase the temperature of the material web with the help of the steam applied to the material web in order to increase the dewatering performance of the press section. The steam blower box offers the possibility of influencing the moisture cross profile of the material web by sectionally different steam application.

In the known construction, the steam emerging from the sectional chambers (or "zone chambers") is regulated by valves which are arranged inside the steam blow box. Each correction zone is equipped with a separate, generally pneumatically controlled valve.

Failure of a control valve means that the corresponding zone can no longer be corrected at first, which leads to an impairment of the paper quality. Replacing a defective valve requires an expensive shutdown. Until a stable operating state is reached again, a long period of time is sometimes necessary, in which reject paper is temporarily produced (removal, installation and warm-up time). The invention has for its object to provide a device of the type described above, which meets as many of the following requirements as possible:

1. It should be possible to choose the width of the zone chambers as small as possible and accordingly the number of zone chambers as large as possible (given a predetermined length of the steam blow box).

2. The control valves should be able to be repaired or replaced in a simple manner without the machine having to be temporarily stopped for this purpose.

3. The distance between the steam blower box and the passing web (which is usually supported there by a roller) should be adjustable. In normal operating conditions, the distance should be relatively small, but relatively large when starting up or for maintenance purposes.

The object is achieved by the features of claim 1.

While in the prior art the predetermined size of the control valves determines the smallest possible width of the zone chambers, according to the invention the zone chambers can be dimensioned as small as desired, because the control valves are basically arranged outside the steam blower box, to the side next to the machine.

This also gives the additional advantage that the control valves are also accessible during the operation of the machine, so that one or the other control valve can be repaired or replaced if necessary, without the need for expensive machine downtime. In the construction according to the invention, it is probably necessary to connect each zone chamber to one of the control valves by means of its own ("sectional") steam line. To make matters worse, because of the required displaceability of the steam blow box, a section of each sectional steam line must be designed to be movable. Each sectional steam line thus comprises a part attached to the steam box (with an inflow end located outside the steam box) and a movable part which is connected (directly or indirectly) to the relevant control valve on the one hand and which can be coupled to the mentioned inflow end by means of a line connection on the other hand. In this connection, an essential partial idea of the invention is that the clear distance between adjacent inflow ends (of the line parts attached to the steam blower box) is substantially greater than the clear distance provided within the steam blower box between adjacent sectional steam lines. In other words: the parts of the sectional steam line attached to the steam blower box are fanned out against the direction of flow outside of the steam blower box. This is the only way to provide an unusually large number of sectional steam lines (and thus a large number of relatively narrow zone chambers) with relatively small cross-sectional dimensions of the steam blower box and yet have enough space available at the inflow ends for the line connections of the movable line parts to be coupled.

In a preferred embodiment of the invention, the following is provided:

The steam is led from a main steam line to a steam distributor which is arranged outside the paper machine, preferably next to the paper machine, for example on the drive side or in the basement, for example, at a location that is easily accessible while the machine is in operation. The individual control elements (control valves) are arranged on this steam distributor. Each individual zone chamber of the steam blower box is connected to the corresponding control valve via a separate sectional steam line. The parts of the sectional steam lines attached to the steam blower box end (counter to the flow direction) outside the steam blast box on a plate, for example a carrier plate, which is rigidly connected to the steam blower box. Flexible lines between the carrier plate and the control valves serve to absorb the pivoting movement and to compensate for any thermal longitudinal expansion of the steam blower box. The valve actuators are controlled by an electric motor.

The invention is described below using a preferred exemplary embodiment in conjunction with the following drawings:

Fig. 1 overall view;

Fig. 2 cross section through a steam blow box;

Fig. 3 zone chamber with perforated sheet insert;

Fig. 4/5 Connection of the flexible lines with the

Lines of the steam blower box, Fig. 4: detached,

Fig. 5: closed

Fig. 6 Installation example in a press section;

Fig. 7/8 of Fig. 2 and 3 different embodiment.

The steam blower box 48 consists of a self-supporting stainless steel construction; it extends on the jacket of a roller guiding the paper web P transversely to the web running direction through the paper machine, from the driver side FS to the drive side TS (FIG. 8). In Fig. 1 only the drive end of the steam blow box is shown. In the lower support frame 1, 1 ¹ webs 43 are welded, the bores 10 and 11 exhibit. The lower support frame 1, 1 'and an upper support frame 2 are connected to one another via side walls 8 and 9. This design ensures optimal transverse stability. The support frames 1, 1 'and 2 as well as the side walls 8 and 9 delimit a central chamber 15. Through this extends a tube bundle, consisting of a plurality of steam lines 4, each of which opens into a zone chamber 3, in order to thereby pass the paper web P to be charged with "steam I".

A steam channel 13 opens into the lower chamber 12. According to FIG. 1, the preheating steam (“steam II”) flowing in here passes through the bores 10 and 14 into the chamber 15, which includes the tube bundle 4. Via the holes 16, this steam II finally reaches the chamber 33 of the support frame 2. In a different exemplary embodiment, the inflowing steam II is first passed through the chamber 12 from the drive side to the driver side and reaches the chamber 15 via holes in the connecting zone 45 (FIG 7 and 8). This steam II, the temperature of which is higher than the steam I within the sectional steam lines 4, ensures that, even when the valves are closed, the sectional steam lines 4 and the individual zone chambers 3 are not cooled. This means that achieved that little or no condensate forms in the steam lines and in the zone chambers. Furthermore, a strict separation between steam I and steam II is ensured.

The individual zone chambers 3 are arranged on the lower support frame 1, 1 '. They are fixed on the side plates 19 and 17. A separate steam line 4 opens into the zone chambers. Each zone chamber contains a perforated plate insert 20 with perforated plates 34, the free cross-sectional area of which increases towards the steam outlet. These perforated plates 34 cause the steam I within the individual zones are evenly distributed over the zone width. The individual perforated sheet inserts 20 can be pulled out for maintenance purposes (FIG. 3).

The individual zone chambers 3 are delimited by a common steam outlet plate 22 (according to FIG. 1). This is screwed to the sheet metal parts 19 and 1, or fixed via guide strips 44, so that it can be easily removed for cleaning purposes. It has several rows of blowing openings 32 arranged one behind the other in the longitudinal direction. The direction of the steam outlet can be inclined perpendicular to the paper running direction or according to FIG. 2, so that the steam I flows against the incoming web. Wherever steam condensation could occur, drain openings 11, 18 are provided with the associated drainage channels 24, 25, 26, 27.

The drive-side end of the steam blow box 48 rests on a frame 51 according to FIG. 1 by means of a carrier plate 28, which can be an extension of, for example, the lower support frame 1, 1 '(FIG. 2). The steam lines 4 are opposite to the steam flow direction extended beyond the drive end of the steam box; their inflow ends are, for example, firmly connected to the carrier plate 28. A control element, designated overall by R, is arranged laterally outside the paper machine and comprises, for each zone chamber 3, a control valve 35 driven by a stepping motor M. The connection from the control valves 35 to the carrier plate 28 is carried out by lines 29, which are at least partially designed as flexible lines. The outflow ends 29 'of a number of the flexible lines are fastened to a so-called supply plate 30. This supply plate is connected to the carrier plate 28 by means of snow tension element 31. If the steam blower box is removed, a quick uncoupling is possible via this tendon tension element (see FIGS. 4 and 5). The control valves 35 are designed so that several can be combined side by side on a steam distribution channel 36. Steam is supplied to each steam distribution channel 36 from a main steam line H.

Advantages of the described construction of the control element R:

1. The arrangement outside the steam blower box allows a very large number of zone chambers 3 and convenient maintenance of the valves 35 while the machine is running.

2. There is no need to limit the temperature of the steam as the control valves do not contain any wear parts such as Membranes, have (no steam cooling).

3. Finest dosing of the steam quantities due to the stepper motor drive is possible.

4. A problem-free and inexpensive switch from manual to automatic control is possible.

5. No compressed air supply is necessary (the I / P converter is no longer required).

6. A direct readability of the valve position is possible.

Using a known method, it can be ensured that the amount of steam emerging from the valve is almost independent of the downstream resistors, i.e. Despite different lengths of steam line in the individual zones, it is ensured that approximately the same amount of steam emerges from each zone with the same valve position.

From the cross sections Fig. 2 and 7 it can be seen that in the interior of the steam blow box 48 and 48 ', the sectional steam lines 4 are almost close to each other one above the other (clear distance a). The same steam lines, however, are fanned out outside the steam load box, so that relatively large clear distances b are present in their inflowing ends 4 ', with (as an example) b being 10 to 50 times of a can be (Fig. 4). As a result, the number of zone chambers 3 can be made very large (their width B very small); at the same time, all the couplings 29 ′ which connect the flexible lines 29 to the inflow ends 4 ′ can be arranged on the carrier plate 28 in one and the same plane.

In extreme cases, the width of the individual zone chamber can be reduced to a dimension that is only slightly larger than the outer diameter of the individual steam line 4.

FIG. 6 schematically shows a press section in which a pre-press nip is formed between two press rolls 45 and 46, through which the paper web to be dewatered runs together with 2 felts. Behind the pre-press nip, the lower felt runs to a felt guide roller 49, while the paper web together with the upper felt on the press roller 46 (mostly a suction press roller) runs upwards into a press nip which is formed between the rollers 46 and 47. The press roll 47 is feltless, i.e. this comes into direct contact with the paper web. One or two scrapers 50 are therefore provided for the constant cleaning of this roller. In the very narrow space between the rollers 49, 46 and 47 on the one hand and the scrapers 50 on the other hand, the steam blow box 48 already described above is arranged. It is shown in the normal operating position; however, it is slidable horizontally to temporarily move it to a position away from roller 46.

Claims

claims Apparatus for applying steam ("Steam I") to a running web of material (P), e.g. on a drainage and through the press section of a Paper-making machine running paper web, with the following features: a) an elongated steam blow box (48) extends across the entire web width transversely to the web running direction; b) the steam blower box (48) has a plurality of zone chambers (3) lined up along the web width; c) each zone chamber (3) is connected to a steam source via its own sectional steam line (4,29) with a control valve (35) provided therein (H) connected; characterized by the following additional features: d) the steam blower box (48) is mounted so that the distance between the Steam box and the web path is adjustable; e) each of the control valves (35) is arranged laterally at a distance from the steam blow box, for example laterally outside the paper machine, and by means of a movable part (29) of the sectional steam line with the inflow end (4 ') of a part (4) of the steam blow box sectional steam pipe connected; f) the areas of the sectional steam lines (4) located within the steam blow box (48) are arranged such that the clear distance (a) between adjacent lines (4), seen in cross section through the steam blow box (FIG. 2 or 7), only one Fraction of the clear distance (b), which is provided between adjacent and outside the steam blow box inflow ends (4 ', Figure 4 or 5). 2. Device according to claim 1, characterized in that for preheating or heating the steam blow box (48) steam ("steam II") regardless of the material web (P) acting steam ("steam I"), the steam blower box can be fed. 3. Device according to one of claims 1 or 2, characterized in that on at least one of the two ends of the steam blow box (48) a support plate (28) is provided which extends into the area outside the longitudinal extent of the steam blow box (for example in the area laterally extends outside the paper machine), and that each of the inflow ends (4 ') of the am Steam blower box attached part (4) of the sectional steam line is attached to the support plate (28). 4. The device according to claim 3, characterized in that at least one group of flexible lines (29) by means of a supply plate (30) to the carrier plate (28) can be coupled. 5. Device according to one of the preceding claims, characterized in that each of the control valves (35) can be controlled by means of a stepping motor (M). 6. Device according to one of the preceding claims, characterized in that the width (B) of the individual zone chamber (3) is approximately equal to the diameter (D) of the steam line (4) opening into it. 7. Device according to one of the preceding claims, characterized in that a cavity (33) is provided in the upper region of the steam blower box cross-section, in which a carrier can be inserted transversely to the web running direction, for the purpose of removing the steam blower box from the paper machine (Fig. 2). 8. Use of a device according to one of the preceding claims in a press section comprising at least three press rolls (45-47), said press section having the following features: a) the paper web runs with a felt over the middle press roll (eg suction press roll 46) into a press nip, formed by the suction press roll and a feltless press roll (so-called central roll 47); b) the steam blower box (48) vaporizes the paper web as it runs over the suction press roll (46) and is displaceable relative to it, so that the distance from the suction press roll can be adjusted; c) a scraper (50) is provided on a peripheral part of the felt-free press roll that is free of the web. 9. Use of a device according to claim 8, characterized in that two scrapers (50) are provided in succession on the feltless press roll (47). 10. Use of a device according to claim 8 or 9, characterized in that the paper web runs through a pre-press nip in front of said press nip together with the felt and a second felt, and that the second felt runs from the pre-press nip to a guide roller (49).