FI79730B - APPARAT OCH FOERFARANDE FOER AVVATNING AV EN FIBERSUSPENSION PAO EN PAPPERSMASKIN. - Google Patents

Description

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Apparatus and method for removing water from a fiber suspension in a paper machine. - Apparat ochförfarande för avvattning av en fibersuspension pä en pappersmaskin.

The present invention relates to an apparatus and method for removing water from fiber suspensions in a paper machine.

In the known type of paper machine, the fiber suspension passes between the upper and lower forming wires and the water leaves the suspension upwards using a headbox lip and a curved inverted suction box which contacts the upper wire. The two wires trap the mass on the inlet membrane and the water flows upwards into the lip opening and then, due to the constant pressure of the two wires, the dewatering continues into the openings of the upturned suction box. (FR-A-235042)

The transfer suction box is located behind the inverted suction box on the downstream side and the vacuum applied to the suction box changes the direction of flow and dewatering takes place downwards while the mass is transferred to the downstream wire.

The radius of the cover is typically 5 m and the contact surface of its upper wire is open to vacuum. The openings in the cover are slots or drilled holes. The arrangement is such that an upward drainage of water along the entire length is formed.

A similar arrangement is shown in: Proceedings of the Technical Association of the Pulp and Paper Industry (TAPPI Press) page 16 and Figure 4, 2-5 March 1981, Conrad Hilton Hotel, Illinois, USA. The article "The Bel Bond Former Concept & Experience" presents a curved, inverted vacuum box equipped with a two-way, underlying forming run. A vacuum is applied to the entire length of the box to remove water upward from the web along the entire length of the box, although downward drainage is permitted through the second portion of the box.

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Removing water from the pulp using current arrangements requires applying a vacuum to the entire length of the cover or working surface, which in turn increases the power required to operate the top wire. It is an object of the present invention to provide a dewatering device which is more economical in capital and operating costs than the current arrangements and which allows the pulp to remain better on the lower wire and which further prolongs the service life of the suction box lid.

According to one aspect of the invention, there is provided an apparatus for removing water from a fiber suspension in a paper machine, the apparatus having a suction box having a functional surface or lid adapted to co-operate with the top wire to force this wire toward the forming wire. removed upwards and a second, closed part behind the first open area, which second area pushes the water downwards.

The first open area has a plurality of slits or slit-forming foils or a plurality of drilled holes. The open area in the first part of the cover may decrease in the direction of travel.

The closed part of the lid does not allow water to drain through the lid and for this reason the pressure of the two wires forces the drainage operation to change direction and take place downwards.

According to another aspect of the invention, there is provided a method of removing water from a fiber suspension in a paper machine, wherein the fiber suspension trapped between the top wire and wherein the water is directed downward as the fiber suspension travels in the direction of travel past the second, closed portion of the lid behind the first region.

The invention will now be explained in more detail in the form of an example with reference to the accompanying drawing, which schematically shows a dewatering device in a paper machine by hand.

The machine comprises an endless top wire 1 drawn around rollers 3. The dewatering device is in the form of a curved, inverted suction box, the suction housing 7 of which is placed inside the upper wire 1 and whose working surface or lid 9 cooperates with the upper wire 1. The cover 9 forces the upper wire 1 towards the forming wire 5. The fiber suspension is trapped between the upper wire 1 and the forming wire 5.

The wires 1, 5 move in the direction indicated by the arrows A. The forming wire 5 passes over the inlet foil 11, which foil forces the water upwards, the lip gap 13 immediately behind the inlet foil removes some of the water upwards. The first part of the lid 9 removes more water upwards, the first part having an open area and to which suction is applied from the suction box. The open area extends over the area indicated by reference numeral 15 and consists of a plurality of slits or drilled holes formed by the foils. The curvature of the open area can be a certain combination, with the radius decreasing in the direction of travel to progressively achieve a higher dewatering pressure.

The second part of the cover is generally shown at 17 and is closed. In this case, no dewatering takes place through the lid in this part, and therefore the pressure of the two wires forces the dewatering to change its direction and take place downwards.

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The downward dewatering thus begins before the transverse suction box 19 located behind the inverted suction box 7. The downstream water is scraped off the lower wire 5 at the front edge of the transfer box and through the open area of the transfer box lid 21.

The dewatering device according to the present invention has the following advantages:

The downward dewatering performed by the second part of the curved inverted suction box is performed by gravity and does not require any vacuum assistance (as is currently required). This results in adjustment of capital and operating costs as follows: the vacuum pump and its installation no longer require an overhead stainless steel compartment or its inlet and outlet devices, the cost of operating the energy required to maintain the vacuum

Since no vacuum is applied to the second part of the wire, the power required to operate the upper wire is reduced and when the last part of the suction box tends to become clogged due to the low water flow therein, the new closed lid is not clogged.

Bel Bond's permanence is improving. The water moving downwards passes through the formed sheet and the lower wire and has a lower consistency than the water currently leaving upwards.

Water coming down from the other part of the suction box lubricates the transfer box cover and increases the service life of the suction transfer box cover.

Claims (9)

An apparatus for dewatering a fiber suspension on a paper machine, comprising a suction housing (7) having an active surface or cover (9), which is arranged to cooperate with an overwire (1) to drive this wire against a forming wire (5), wherein the fiber suspension is trapped between the top wire and the forming wire, characterized in that the cover (9) has a first open area (15) by which water is removed uptight, and a second solid portion (17) downstream of the first open area which drives water downward. Apparatus according to claim 1, characterized in that the first open area (15) comprises a plurality of slots, or fins defining slots, or a plurality of drilled heels. Apparatus according to claim 1 or 2, characterized in that the open area in the first part of the cover (9) is reduced in area in the downstream direction. Apparatus according to any of the preceding claims, characterized in that the open area (15) has a composite curvature with a radius which decreases in the downstream direction. Apparatus according to any one of the preceding claims, characterized in that it comprises an inlet fin (11) located upstream of the cover (9) of the suction housing and arranged to be in contact with the forming wire (5), and a transfer suction lid (19). which is located downstream of the cover housing (9) and is arranged to be in contact with the forming wire (5). 6. Apparatus according to claim 6, characterized in that the introductory fin (1i) has a solid surface for conducting water consumed, and wherein the transfer suction blank (19) has an open area with applied vacuum to suck the fiber suspension against the β 79730 mold wire (5). . 7. A method of dewatering a fiber suspension on a paper machine, in which a fiber suspension which is trapped between an upper wire (1) and a lower forming wire (5) is passed past an active surface or cover (9) on a suction housing, with the upper wire ( 1) contacting the cover for the purpose of removing water from the fiber suspension, characterized in that the water is extracted in an upward direction as the fiber suspension moves past a first open area (15) of the cover (9) and the water is directed downwards as the fiber suspension moves past a second solid part (17) of the cover, which is located downstream of the first area (15). Method according to claim 7, characterized in that pressure is applied to the fiber suspension as it passes over the active surface (9) and the pressure increases in the downstream direction over the first open area of the active surface in proportion to the radius of the active surface. 9. A method according to claim 7 or 8, characterized in that water is driven upstream upstream of the cover (9) by contacting the lower forming wire (5) with a massive lead-in fin (11) and in which further water is extracted downstream of the cover (9) by passing the lower forming wire (5) over the cover (21) of a transverse suction.