WO2002029346A1

WO2002029346A1 - Method and device for preventing fall of drops

Info

Publication number: WO2002029346A1
Application number: PCT/FI2001/000861
Authority: WO
Inventors: Raimo Rajala; Eino HÄRKÖNEN; Jouni Paltakari; Olli Asp
Original assignee: Process Team Finland Oy
Priority date: 2000-10-04
Filing date: 2001-10-04
Publication date: 2002-04-11
Also published as: FI20002188A0; FI109039B; AU2001293898A1

Abstract

A method and a device (20) for preventing liquid drops (21) condensed especially on different parts of a paper machine (10) from falling onto the paper web. According to invention, a space containing humid air or mist consisting of splashes, preferably a space below a part located above the paper web, is provided with a body (22), such as a suction box 22, having a slot (25) at its lower edge. The liquid drops (21b) flowing along the surface of the suction box are allowed to flow down to the slot, from where the drops are sucked by negative pressure or using a porous, spongy material (32) into the suction box 22. The suction box may also have a trough (23) on its upper surface for removal of the liquid condensed or gathered on the upper surface of the suction box.

Description

METHOD AND DEVICE FOR PREVENTING THE FALL OF DROPS

SUBJECT OF THE INVENTION

The present invention relates to a method for preventing the fall of liquid drops, according to which method a space containing humid air or a mist consisting of splashes is provided with a body having at least one orifice for removing the spray or mist.

STATE OF THE ART

Water or other liquid contained in humid air or in a mist of splashes is apt to condense or gather as drops on various surfaces. This is what happens e.g. in paper or cardboard manufacturing processes, in which large quantities of water and other liquids as well as steam are used. In paper or cardboard manufacturing machines, this phenomenon is harmful because the humidity is condensed on the frame, beams and other parts of the machine as drops which then fall down onto the paper or cardboard web below. The liquid, such as water, of the drop, as well as any impurities that may be present in the liquid, produce on the paper or cardboard web clearly visible marks that cannot be tolerated in the manufacture of high-quality paper or cardboard.

According to a prior-art method, in paper or cardboard machines, hot steam is blown through a steam kiln towards the paper or cardboard web supported by the wire. To prevent the steam from spreading into the environment and wetting the components of the paper or cardboard machine and the supporting structures of the machine hall, a suction box is connected to the steam kiln to collect the steam blown towards the paper or cardboard web. However, in spite of the suction box, the propagation of the steam into the surroundings can not be prevented. Some steam is always admitted into the machine hall, where it tends to condense as liquid drops on different parts and supporting structures of the paper or cardboard machines.

OBJECT OF THE INVENTION The object of the present invention is to achieve a method for preventing liquid drops condensed or gathered on various surfaces in humid air or in a mist consisting of splashes from falling e.g. onto a paper web.

FEATURES CHARACTERISTIC OF THE METHOD OF THE INVENTION The method of the invention is characterized in that in the space containing humid air or mist consisting of splashes the moisture is allowed to condense or gather as drops on the surface of the aforesaid body, the liquid drop is allowed to flow down along the surface of said body to a slot or orifice provided in the lower edge of the body, and that the liquid drop having flowed to the slot or orifice in the lower edge of the body is passed into the interior of the body or into another corresponding space.

EMBODIMENTS OF THE METHOD OF THE INVENTION

A preferred embodiment of the method of the invention is characterized in that the liquid drops condensed on the surface of the body and having flowed to the slot or orifice in the lower edge of the body are sucked into the interior of the body or into another corresponding space by using a negative pressure.

When the liquid drop has been sucked into the interior of the body, such as a suction box, via the slot or orifice, the drop is again broken up into a mist, which is passed from the suction box into a liquid separator by means of a suction device generating a negative pressure.

A second preferred embodiment of the method of the invention is characterized in that the liquid drops condensed on the surface of the body and having flowed to the slot or orifice in the lower edge of the body are sucked into a porous, spongy material provided inside the body.

A third preferred embodiment of the method of the invention is characterized in that the liquid drops condensed on the surface of the body and sucked through the slot or orifice in the lower edge of the body into the porous, spongy material are removed from the porous, spongy material by compressing this material against the interior wall of the body, preferably using a bellows which can be filled with compressed air.

A fourth preferred embodiment of the method of the invention is characterized in that the body in the space containing humid air or mist consisting of splashes is cooled to induce condensation of moisture on the surface of the body, and that the liquid drops condensed on the surface of the body are allowed to flow to the slot or orifice in the lower edge of the body, from where the liquid drops are sucked into the interior of the body by negative pressure or by means of a porous, spongy material.

DEVICE OF THE INVENTION

The invention also relates to a device for preventing the fall of liquid drops, said device comprising a body to be placed in a space containing humid air or mist consisting of splashes, said body being provided with at least one orifice for the removal of splashes or mist.

FEATURES CHARACTERISTIC OF THE DEVICE OF THE INVENTION The device of the invention is characterized in that the body placed in a space containing humid air or mist consisting of splashes comprises at least one upright, inclined or curved surface, on which the liquid drops are condensed or gathered and along which the liquid drops can flow downwards, and that - the body comprises at least one slot or orifice in the lower edge of the upright, inclined or curved surface for passing the liquid drop having flowed downwards along the surface into the interior of the body or into another corresponding space.

EMBODIMENTS OF THE DEVICE OF THE INVENTION A preferred embodiment of the device of the invention is characterized in that the device comprises a body, such as a suction box, connected to a suction device generating a negative pressure and having a slot at its lower edge.

A second preferred embodiment of the device of the invention is characterized in that - the edges of the slot of the suction box form the lowest extremity of the suction box, and that the edges of the slot are sharp and/or curved so as to convey all the drops flowing along the surface of the suction box into the vacuum slot.

With a curved shape of the edge part it is possible to take advantage of the phenomenon accelerating the velocity of flow on a curved surface. The velocity of the air flow entering through the slot of the suction box is increased in the region of the curved edge part, and the increased velocity of flow boosts the suction drawing the drops into the slot of the suction box.

A third preferred embodiment of the device of the invention is characterized in that the suction box comprises one or more parts having the shape of a downward tapering triangle with a slot at its lower edge.

A fourth preferred embodiment of the device of the invention is characterized in that the device comprises a body with an interior space filled with a porous, spongy material, part of said material being placed in the area of the slot or orifice in the lower edge of the body so that liquid drops flowing down the surface of the body will be absorbed into the this porous, spongy material.

A fifth preferred embodiment of the device of the invention is characterized in that the device comprises a body with an interior space filled with a porous, spongy material and a bellows by means of which the porous, spongy material can be compressed between the bellows and the interior wall surface of the body to remove the water from the porous, spongy material.

A sixth preferred embodiment of the device of the invention is characterized in that the body, such as a suction box, has a mainly circular cross-sectional form.

A seventh preferred embodiment of the device of the invention is characterized in that the device comprises a body, such as a suction box, having a slot or orifice at its lower edge and a cooling means, such as a flow channel for a cooling liquid, in at least one wall.

An eighth preferred embodiment of the device of the invention is characterized in that the upper surface of the suction box is provided with at least one trough or basin connected to an outlet channel or orifice for removal of liquid condensed or gathered on the upper surface of the suction box.

EXAMPLES OF EMBODIMENTS

In the following, the invention will be described by the aid of examples with reference to the attached drawings, wherein

LIST OF DRAWINGS

Fig. 1 presents a side view of a device according to the invention for preventing the fall of drops, with the suction box partially sectioned.

Fig. 2 the device of Fig. 1 as seen from another lateral direction and partially sectioned.

Fig. 3 presents the suction box of the device in Fig. 1 as seen from below.

Fig. 4 presents a cross-section of a detail of the suction box of the device in Fig. 1 ,

Fig. 5 corresponds to Fig. 1 and presents a second embodiment of the device in lateral view and partially sectioned. Fig. 6 presents a cross-section of a third embodiment of the suction box of the device in Fig. 1. Fig. 7 corresponds to Fig. 6 and presents a cross-section of a fourth embodiment of the suction box. Fig. 8 corresponds to Fig. 6 and presents a cross-section of a fifth embodiment of the suction box. Fig. 9 corresponds to Fig. 6 and presents a cross-section of a sixth embodiment of the suction box. Fig. 10 illustrates the emptying of the suction box.

DESCRIPTION OF THE DRAWINGS Fig. 1 presents a part of a paper machine 10, in which the humidity of the air near the paper web 11 is so high that the water contained in the air tends to condense on the surfaces of different parts of the paper machine 10. As an example, Fig. 1 shows above the paper web 11 a beam 12 on whose surface drops 21a are condensed. Without a device 20 according to the invention, the drops would fall directly onto the paper web 11.

In Fig. 1 , the device 20 of the invention is placed in the paper machine 10 in a position below the beam 12 and above the paper web 11 to prevent the drops 21 condensing on the surface of the beam 12 from falling onto the paper web 11. The device of Fig. 1 comprises a suction box 22 whose upper surface forms a trough 23. The drops 21a condensed on the surface of the beam 12 fall into the trough 23, from where the water is conducted out of the paper machine 10.

As the air in the paper machine 10 in the vicinity of the paper web 11 is very humid, drops 21b will also condense on the inclined side surfaces 24a and 24b of the suction box 12. To prevent these water drops 21 b condensing on the side surfaces 24a and 24b of the suction box 22 from falling down onto the paper web 11 of the paper machine 10, their removal is implemented using a suction device generating a negative pressure. The water drops 21 b are allowed to flow down along the side surfaces 24a and 24b of the suction box 22 towards the slot 25 in the lower edge of the suction box 22. When the drops 21b reach the slot 25, the negative pressure sucks the drops 21b into the space inside the suction box 22. In the suction box 22, due to the negative pressure, the drops 21b are converted into mist, which is sucked by the suction device into a water separator placed outside the suction box 22.

As shown in Fig. 2, the suction box 22 of the device 20 is placed between the beam 2 of the paper machine 10 and the paper web 11. The trough 23 on the upper surface of the suction box 22 gathers all water drops 21a condensed on the surface of the beam 12 and falling down from it. From the trough 23, the water is conducted out of the paper machine 10. The water drops 21b condensing on the surface of the suction box 22 flow into the slot 25 in the lower edge of the suction box and are then sucked by a negative pressure into the space inside the suction box 22 and further out of the paper machine 10 into a water separator.

Fig. 3 shows the suction box 22 as seen from below. It can be seen from the figure that the water drops 21b condensed on the side surfaces 24a and 24b of the suction box flow towards the slot 25 in the lower edge of the suction box 22. Through the slot, the drops 21b are sucked by negative pressure into the suction box 22.

Fig. 4 presents a cross-section of the structure of the lower edge of the suction box 22. The lower edges of the side surfaces 24a and 24b are so sharpened and rounded that the water drops 21 b condensed on the side surfaces 24a and 24b and flowing downwards along them advance exactly towards the sharp and curved edges of the slot 25. From the edge, the drops 21b are sucked by negative pressure into the suction box 22.

Fig. 5 presents a suction box 22 comprising several triangular chambers 26 with inclined side walls 24. Each triangular chamber 26 has at its lower edge a slot 25 through which the drops flowing along the side walls 24 are sucked into the suction box 22. The entire upper surface 23 of the suction box 22 forms a trough or basin, which collects the drops from above the suction box and from which the water is conducted out of the paper machine. A suction box structure 22 like this is preferable when there is plenty of humid mist or splash water above the paper web 11. In this case, the lower surface 24 of the suction box 22 will also gather, besides the condensed water, splash water drops present in the air.

Fig. 6 presents a cross-section of an embodiment of the suction box 22 in which the inclined side surfaces 24a and 24b are cooled. As a result of the cooling, the moisture in the vicinity of the suction box 22 is more effectively condensed on the inclined side surfaces 24a and 24b, so that a larger proportion of the moisture in the air can be removed by means of the suction box 22. Cooling is implemented by providing the suction box 22 with partitions 30a and 30b on the inner side of the inclined side surfaces 24a and 24b, which partitions together with the inclined side surfaces 24a and 24b form cooling liquid spaces 31a and 31 b. These spaces 31 a and 31 b are flow channels e.g. for a cold cooling liquid. Fig. 7 presents a suction box 22 with mainly upright side walls 24a and 24b cooled by means of circulating water channels 31a and 31 b. Correspondingly, Fig. 8 presents an embodiment of the suction box 22 in which the cooled side walls 24a and 24b are partly upright, partly inclined. From the examples presented, it is clear that the shape of the suction box 22 may vary considerably provided only that it allows a downward flow of liquid drops 21a along the walls.

Fig. 9 presents an embodiment in which the suction box 22 is of a circular cross-section with an orifice in its lower edge. The liquid drops 21b flow downwards along the curved side walls 24a and 24b of the circular suction box 22 towards the orifice 25 in the lower part of the suction box 22. In this embodiment, the suction box 22 is filled with a porous, spongy material 32 so that part 32b of this material protrudes somewhat out of the orifice 25 in the lower part of the suction box 22. When liquid drops 21b flowing down the side walls 24a and 24b meet the porous material 32b protruding from the orifice 25, they are absorbed into it. The volume of the porous material 32 is large enough to enable the material to absorb a considerable amount of water. In practice, it is possible to implement the suction box 22 so that the water in the porous material 32 inside it only needs to be drained during a maintenance stoppage of the paper machine.

The removal of the water from the porous material 32 in the suction box 22 presented in Fig. 9 is effected by means of a bellows 33 made of an elastic material, such as rubber hose, placed beside the porous material 32. When the suction box 22 is being used for gathering water, the bellows 33 lies flat between an interior wall of the suction box 22 and the porous, spongy body of absorbing material 32. In the situation presented in Fig. 9, the air space 33 inside the bellows 33 is mainly empty.

Fig. 10 illustrates the draining of the water absorbed by the porous, spongy absorbing material 32 in the suction box 22 of Fig. 9. The draining is effected by supplying compressed air into the bellows 33 made of rubber hose, thus filling it. As a result, the porous, spongy absorbing material 32 is squeezed between the bellows 33 and the opposite interior wall of the suction box 22 and the water 21c in the absorbing material 32 is removed. After the draining of the water, the compressed air is let out from the bellows 33, whereupon it collapses again into the position shown in Fig. 9 and the suction box 22 is again ready for use for moisture removal as described above.

ADDITIONAL REMARKS It is obvious to the person skilled in the art that different embodiments of the invention may vary within the scope of the claims presented below.

LIST OF REFERENCE NUMBERS

10 paper machine

11 paper web 12 beam

20 device

21 drop

22 suction box

23 trough 24 side surface

25 slot

26 triangular space

30 partition

31 water space 32 sponge

33 bellows

24 air space

Claims

1. Method for preventing the fall of liquid drops (21), according to which method a space containing humid air or mist consisting of splashes is provided with a body (22) having at least one orifice (25) for removing the spray or mist, characterized in that in the space containing humid air or mist consisting of splashes the moisture is allowed to condense or gather as drops on the surface (24) of the aforesaid body (22), the liquid drop (21) is allowed to flow down along the surface (24) of said body (22) to a slot (25) or orifice provided in the lower edge of the body, and that - the liquid drop (21 ) having flowed to the slot (25) or orifice in the lower edge of the body is passed into the interior of the body (22) or into another corresponding space.

2. Method as defined in claim 1 , characterized in that the liquid drops (21 b) condensed on the surface (24a, 24b) of the body (22) and having flowed to the slot (25) or orifice in the lower edge of the body are sucked into the interior of the body or into another corresponding space by negative pressure.

3. Method as defined in claim 1, characterized in that the liquid drops (21 b) condensed on the surface (24a, 24b) of the body (22) and having flowed to the slot (25) or orifice in the lower edge of the body are sucked into a porous, spongy material (32) provided inside the body.

4. Method as defined in claim 3, characterized in that the liquid drops (21c) condensed on the surface (24a, 24b) of the body and sucked through the slot (25) or orifice in the lower edge of the body into the porous, spongy material (32) are removed from the porous, spongy material by compressing this material against an interior wall of the body preferably using a bellows (33) that can be filled with compressed air.

5. Method as defined in any one of claims 1-4, characterized in that - the body (22) in the space containing humid air or mist consisting of splashes is cooled to induce condensation of moisture on the surface (24a, 24b) of the body, and that the liquid drops (21 b) condensed on the surface (24a, 24b) of the body are allowed to flow to the slot (25) or orifice in the lower edge of the body, from where the liquid drops are sucked into the interior of the body by applying a negative pressure or using a porous, spongy material (32).

6. Device (20) for preventing the fall of liquid drops (21), said device (20) comprising a body (22) to be placed in a space containing humid air or mist consisting of splashes, said body being provided with at least one orifice (25) for the removal of splashes or mist, characterized in that - the body (22) placed in the space containing humid air or mist consisting of splashes comprises at least one upright, inclined or curved surface (24a, 24b), on which the liquid drops (21b) are condensed or gathered and along which the liquid drops can flow downwards, and that the body (22) comprises at least one slot (25) or orifice in the lower edge of the upright, inclined or curved surface (24a, 24b) for passing the liquid drop (21b) having flowed downwards along the surface into the interior of the body or into another corresponding space.

7. Device (20) as defined in claim 6, characterized in that the device (20) comprises a body (22), such as a suction box, connected to a suction device generating a negative pressure and having a slot (25) at its lower edge.

8. Device (20) as defined in claim 6 or 7, characterized in that the edges of the slot (25) of the suction box (22) form the lowest extremity of the suction box, and that the edges of the slot (25) are sharp and/or curved so as to convey all the drops (21 ) flowing along the surface (24) of the suction box into the vacuum slot.

9. Device (20) as defined in claim 6, 7 or 8, characterized in that the suction box (22) comprises one or more parts (26) having the shape of a downward tapering triangle with a slot (25) at its lower edge.

10. Device (20) as defined in claim 6, characterized in that the device (20) comprises a body (22) having porous, spongy material (32) inside it, part (32b) of said material being placed in the area of the slot (25) or orifice in the lower edge of the body so that liquid drops (21b) flowing down the surface (24a, 24b) of the body are absorbed into the this porous, spongy material.

11. Device (20) as defined in claim 10, characterized in that the device (20) comprises a body having porous, spongy material (32) inside it and a bellows (33) made of elastic material, by means of which the porous, spongy material can be compressed between the bellows and the interior wall of the body to remove the water (21c) from the porous, spongy material.

12. Device (20) as defined in any one of claims 6-11, characterized in that the body (22), such as a suction box, has a mainly circular cross-sectional form.

13. Device (20) as defined in any one of claims 6-12, characterized in that the device (20) comprises a body (22), such as a suction box, having a slot (25) or orifice at its lower edge and a cooling means (31a, 31b), such as a flow channel for cooling liquid, in at least one wall.

14. Device (20) as defined in any one of claims 6-13, characterized in that the upper surface of the suction box (22) is provided with at least one trough (23) or basin connected to an outlet channel or orifice for removal of liquid condensed or gathered on the upper surface of the suction box.