WO2011154598A1

WO2011154598A1 - Suction device of a press felt

Info

Publication number: WO2011154598A1
Application number: PCT/FI2011/050524
Authority: WO
Inventors: Aki Valtonen
Original assignee: Metso Paper, Inc.
Priority date: 2010-06-08
Filing date: 2011-06-06
Publication date: 2011-12-15
Also published as: FI20105652A; FI122422B; CN102933766A; EP2580391A1; EP2580391B1; FI20105652A0

Abstract

The invention concerns a press felt suction device. The suction device comprises a tubular body (1) extending in a transversal direction across the felt web (3) and is equipped with a suction slot arrangement (2) extending over the length of the body and being in contact with the felt, and the inside of the body is connected with an exhaust suction apparatus. The exhaust suction is directed to the inside of the tubular body (1) partitioned (4, 7) over the length of the tubular body. The suction device has means (6, 8) for deflecting the direction of the suction flow in the vicinity of the point of action of the exhaust suction, and at least one water draining connection (5) is located in the tubular body below the action point of the exhaust suction.

Description

SUCTION DEVICE OF A PRESS FELT

The present invention is directed to a so called felt suction device that is used for removing water from a press felt of a pulp dryer machine, paper machine and cardboard ma- chine, and for cleaning the felt. A felt suction device is usually a tubular construction located in a suitable place in the felt circulation, in transversal direction across the felt. The inside of the hollow tube construction is connected to a vacuum system, which keeps the inside of the tube under a vacuum. Through a slot construction, the vacuum effects on the felt that travels over the felt suction device, said slot construction extending over the total length of the suction device. Slot constructions equipped with different wear strip arrangements and adjusting devices are known. A significant amount of air and water travels through the felt to the suction device, taking along impurities gathered in the felt.

Air and water are removed from the outlet flow coming from the suction device before leading it to the vacuum producing device that is a part of the suction device. It is known in the art to use for example a liquid ring pump or a fan as a device for producing the vacuum. For removing air and water from the outlet flow, it is known to use different extracting devices like cyclone separators included in the suction equipment, used for air flows with water content. Because they are space-taking, they are located outside the paper ma- chine, usually on the drive side, between the felt suction device and the vacuum device.

An object of the present invention is to simplify the construction of the felt suction equipment to be less space-taking. With a simplified construction, it can operate without needing any devices to be located between the felt suction device and the vacuum device, in addition to the necessary pipe fittings. The basic object of the invention can be achieved with a felt suction device comprising, as known, a tubular body extending in transversal direction of the felt web and being equipped with a suction slot arrangement extending over the length of the body in contact with the felt, having the inside connected with a exhaust suction apparatus. Characteristically of the invention, the suction flow is deflected in the vicinity of the point of action of the exhaust suction, and below the point of action of the exhaust suction there is at least one water drainage connection located in the tubular body.

Other characteristic features of the invention are stated in the enclosed dependent claims. The invention will be described in more detail with reference to the enclosed drawings, wherein Figure 1 shows a side view of a felt suction device in accordance with the present invention,

Figure 2 shows a cross-sectional view of the felt suction device of Figure 1 , Figure 3 shows a longitudinal section of an alternative felt suction device in accordance with the invention, and

Figure 4 shows a cross-sectional view of the felt suction device of Figure 3.

The felt suction device of Figure 1 comprises a basic body 1, which is in a usual way, a hollow tubular or corresponding construction. The inside of the tube is in connection with a vacuum producing device in a way described in further detail later. A suction slot con- struction 2 is located onto the upper surface of the tube extending over the total length thereof, a press felt 3 travelling over it and being exposed to vacuum maintained in the tube 1. Suction slot arrangements are known having many different implementations and being equipped with different wear strip solutions. In a conventional felt suction device, the inside of the tubular body is in connection with the vacuum producing device through an exhaust tube, having an outlet located at the end of the tube body.

Departing from that, as shown in Figure 1, the tube body has two exhaust connections 4 located at a distance from each other over the length of the tubular body, and in addition, a drainage connection 5. The outlet of the drainage connection 5 is located in the tubular bodyl below the exhaust connections 4. A target of this construction is to cause the flow that is sucked from the felt 3 and containing water and air, to separate in the tubular body, so that only water is removed from the drainage connection 5 and mainly air is removed from the exhaust connections 4. For reaching this target, the locating of the exhaust connections 4 is essential, in other words, their distribution over the length of the felt suction tube 1 so that the volume flow coming through the suction slot 2 and growing towards the exhaust connections 4 is limited so that the flow rate in the suction tube will be limited to an area, where water is separated from the air during the time, when the flow travels inside the suction tube. A target value has been discovered to be a flow rate of abt. 2 - 4 m/s or less. Another factor having effect on the flow rate prevailing inside the suction tube is naturally the inner diameter of the suction tube. It has been discovered that the felt suction tube implemented with usual operation values in a pulp drying machine having a machine width of 10 m, can be dimensioned to have a diameter of 500 mm, in the case that, in addition to a water draining connection, there are two air exhaust connections connected to the vacuum producing device, evenly distributed over the length of the felt suction tube and located having the outlet above the draining connection. With three air exhaust connections 4 correspondingly arranged and connected to the vacuum producing device, the tubular body 1 of the felt suction device can be implemented with a diameter of about 400 mm.

It is well-founded to locate the outlets of the air exhaust connections 4 connected to the vacuum producing device to the upper part of the tubular body 1, clearly on a different level than the outlet of the draining connection 5 meant for water draining. At the points of the air exhaust connections 4 the tubular body 1 can have deflection plates 6 for facilitating the separating of the air and water. However, the deflection plates must not have an increasing influence on the general flow rate prevailing in the tube.

The air removed through the exhaust connections 4 from the tubular body 1 can be led outside the paper machine with a discharge pipe located beside the tubular body 1 , in the felt circulation. Some water separation from the air flow can still be effected in this discharge pipe, and the separated water can be drained for example through a connection located in the lower part of the pipe, or by leading the pipe so that the possibly separated water flows back to the suction device.

Figure 3 shows an alternative felt suction device as a longitudinal section, and Figure 4 shows the same in a cross-section. Figure 3 shows a tubular body 1 of the felt suction device. The upper part of the body 1 has a suction slot construction 2, over which the felt travels. On the bottom of the body there is a water draining connection 5 for removing water from the felt suction device. For air removal there is an air exhaust pipe 8 located inside the felt suction device, extending over the total length thereof. At the end of the pipe 8 extending outside the felt suction device there is an air exhaust connection 4 that is connected to the vacuum producing device. The portion of the air exhaust pipe 8 that is inside the felt suction device 1 is provided with holes 7 for leading the air to the air ex- haust pipe. The holes can have different shapes like round, elongated or slot-like. Preferably there are holes evenly over the total length of the felt suction device. Also a slot extending over the length of the pipe 8 can be used as air removal path from the inner part of the felt suction device body to the pipe 8. Separation of water from the air is efficient, when the holes or the slot are located in the lower surface of the pipe.

Also the construction according to Figure 3, or variations thereof, have a draining connection 5 in the lower part of the tubular body 1, through which the water separated from the water-air flow sucked through the suction slot arrangement 2 to the tubular body is drained.

Claims

Claims:

1. A suction device of a press felt, said suction device comprising a tubular body (1) extending in a transversal direction across a felt web (3) and being equipped with a suction slot arrangement (2) extending over the total length of the body, in contact with the felt, the inside thereof being connected with an exhaust suction apparatus so that the exhaust suction is directed to the inside of the tubular body (1) partitioned (4, 7) over the length of the tubular body, characterized in that the suction device further comprises means (6, 8) for deflecting the direction of the suction flow in the vicinity of the point of action of the exhaust suction, and that below the point of action of the exhaust suction there is at least one water draining connection (5) located in the tubular body.

2. A press felt suction device according to Claim 1, characterized in that the directing of the exhaust suction to the inside of the tubular body (1) is implemented substantially as a flow slot (7) extending over the length of the tubular body.

3. A press felt suction device according to Claim 1, characterized in that directing of the exhaust suction to the inside of the tubular body (1) is implemented as at least one row of openings extending over the length of the tubular body.

4. A press felt suction device according to any of the preceding claims from 1 to 3, characterized in that the directing of the exhaust suction to the inside of the tubular body (1) is implemented as an air exhaust pipe (8) substantially extending over the total length of the tubular body, whereby the point of action (7) of the exhaust suction is located on the lower surface of the air exhaust pipe.

5. A press felt suction device according to Claim 1, characterized in that the directing of the exhaust suction to the inside of the tubular body is implemented as two or more pipe connections (4) leading to the inside of the tubular body, located over the length of the tubular body at a distance from each other.

6. A press felt suction device according to Claim 5, characterized in that the pipe connections (4) are located over the length of the tubular body (1) having an even distance from each other.

7. A press felt suction device according to Claim 5, characterized in that the inside of the tubular body (1) is equipped with flow deflection plates (6) on the outlet area of the pipe connections (4).

8. A press felt suction device according to any of the preceding claims, characterized in that the exhaust suction is directed on the inside of the tubular body (1) to limit the local maximum flow rate in the internal space of the tubular body to a value of about 2 to 4 m/s.