FI110795B - Venting arrangements for feeding pulp to the inlet box of a paper machine or equivalent - Google Patents

Description

110795

Ventilation system for feeding pulp to a paper machine or similar headbox Avluftningsarrangemang för matning av pulse account inloppslädan av en pappersmaskin eller motsvarade 5

The invention relates to a deaeration system for feeding pulp to a headbox of a paper machine or the like.

10

Separation of pulp and water mixed with water from the fiber suspension is carried out in deaerators, which are subjected to a vacuum corresponding to the pulp temperature. Ilmaπί ty ilma ilmaista on ilmaΕ ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma ilma on ilma on ilma on ilma ilma ilma on on on on on on on on on on kone on on kone kone on on on on on on on on on kone kone kone kone kone kone kone kone kone kone kone kone kone on on on on kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone koneΕί kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone kone koska kone kone koska koska kone kone kone kone kone kone kone kone koska koska koska koska koska koska koska koska kone koska koska koska koska koska ί koska koska koska koska koska koska koska koska koska koska koska koska koska koska koska koska koska koska koska--------------------------mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas mas

The investment costs for deaeration are high because, due to high vacuum, heavy tanks have to be placed high, often even on the roof of a building. The steel structures are high and can be located up to 15 m above the machine platform. In this case, the pipe strokes 20 are long, extending from the basement to the deaerators.

In addition, high vacuum will evaporate a large amount of water, which is why the vacuum system of the deaerator is usually equipped with a condenser to reduce pump capacity. Increasingly, the consumption of raw water at new mills is limited, for which reason the cooling water has to be recycled and cooled in separate cooling stumps.

. ,, · In current systems, the vacuum is high at 90 kPa and the air separation from the fiber suspension is almost complete. When the vacuum is dropped to 40 kPa, 30 - the vent can be placed about five meters lower than previously 2 110795 - produces a vacuum instead of a vacuum pump with a fan because the vacuum level is lower to implement a vacuum system without a condenser.

5 Typical features of the proposed rigid system are: - The vent is run at a relatively low vacuum (30 - 60 kPa), whereby the canister can be placed lower but still a considerable amount of air can be removed from the fiber suspension.

- The vacuum in the venting tank is produced by a blower.

10 - The surface of the wire well is lowered below the machine level, whereby the height of the deaeration tank can be further lowered.

The deaeration tank is implemented in a so-called. on a multi-latency basis, where it acts as an equalizer for pulp consistency variations.

- The machine screen is placed in front of the deaeration tank, in the pulp inlet to the deaeration tank. The headbox pressure rises in the second power as the paper machine speed increases. If the screen is after the pump, a machine screen of 10 bar would be required at speeds above 2000 m / min, which means that the screen is advantageous | list before the deaeration tank.

The deaeration system according to the invention is characterized by what is; * · *: As claimed.

The invention will now be described with reference to an advantageous embodiment of the invention, not depicted in FIG. 1 of the accompanying drawing, but not intended to be limited thereto.

Fig. 1 is a simplified flow diagram of an air exhaust system according to the invention.

Figure 2 shows another preferred air venting system according to the invention. embodiment.

3,110,795

Figure 1 is a schematic representation of an air exhaust system according to the invention for feeding pulp to a headbox of a papermaking machine. In Figure 1, the headbox is shown under reference numeral 10. The mass is led from the wire pit 11 through the channels a1, a2 to the deaeration duct 11. The pump P2 in duct aj directs the pulp from the wire 12 first to the vortex purifier 16 and thence through a the deaerated pulp is further passed through conduit a3 to headbox 10 in its manifold J by a feed pump Pj. The prior art stiffener 10 has a deaeration tank 11 arranged up to a height of 15 m from the surface level of the pulp. In this case, high steel structures have been required to support the container below the height j above the plane T. In the waste system according to the invention, there is provided a deaeration duct 11 in relation to the plane T so that the duct is located at a height h of about 3 m to 10 m from the plane D. The height h is lowered from the plane T to the surface level of the pulp in the deaeration vessel. Further, when the wire well 12 is disposed below the machine plane T, the height of the venting container 11 can be further lowered. Preferably, the height difference H between the deaeration tank and the wire well is in the range of 4 m to 8 m, whereby the height difference is calculated from the surface level of the pulp inside the wire well to the surface of the * 11, 20 pulp. The vacuum level inside the deaeration tank 11 is in the range of 30 kPa to -60 kPa.

As illustrated in Figure 1, a negative pressure is applied to the container 11 by the fan 13 via the fan a4, whereby the negative pressure in the container encounters a mass in a vacuum state and then through the a4 to the fan 13 and further away from the apparatus connection. The figure shows in dashed reference * * »'...' number 14 a droplet separator which may be located between the venting vessel 11 and the fan 13. The deaeration tank 11 has a channel as from the overflow of the deaeration tank and v: back to the wire well 12. The new pulp is led to the wire well 12 via the channel bi: ...: 30. The tap water is led in a return circuit through channel b2 to the wire well 12 in the paper well. from the wire section of a machine or similar 17.

»«>> · 110795

The machine screen 15 is disposed between the vortex cleaning plant 16 and the deaeration tank 11 in a channel a2. Thus, the machine screen 15 will be located before the air separator air separation tank 11 as viewed in the direction of flow of the pulp to be treated Li.

5

Figure 2 illustrates an embodiment of the invention where the channel 12 is provided with a channel P2 comprising a pump P2 and directly to a venting vessel I1 and further to a venting vessel 11 with a channel a2 to a vortex cleaning plant 16 a3 comprises a pump P] at the inlet side of the machine screen 15 with respect to the mass flow direction Li. A fresh mass is led into channel a2 to the suction side of pump P3. Further, the venting vessel 11 may have a channel a2 'for tap water between pump Pi and a vortex cleaning plant 16 to channel a3. The venting vessel 11 is provided with a vacuum within the range of 30 kPa to 60 kPa corresponding to the fan 13 in the embodiment of Fig. 1. As the water separator, the duct a4 has only a droplet separator 14. The venting vessel 11 is thus located 3 m h from plane T above it. Preferably, the wire well 12 is further below the machine plane T and the height difference H between the deaeration tank 11 and the wire well 12 is in the range 20 m to 8 m, the height difference calculated between the mass in the deaeration tank or the surface levels. From the deaeration tank 11, * · is an overflow channel a5 back to the wire well 12. The fresh mass is fed to the duct, but only a2 to the suction side of pump P3.

Claims (7)

A venting arrangement for feeding pulp to the inlet carriage (10) of a papermaking machine or the like, which venting arrangement comprises a venting container (11) leading to a duct (ai, a2) from a wire well (12) either. a direct or via a vortex cleaning plant (16) and in which venting arrangement a duct (a <i) leads to the venting container (11) from a device (13) which produces vacuum for generating vacuum pressure inside the venting tank (11) and in which arrangement a conduit (a3) is arranged for conduction of the mass to the inlet carriage (10), characterized in that the negative pressure in the venting container (11) is within the range of 30 kPa-60 kPa. Venting arrangement according to claim 1, characterized in that the venting container is arranged at a height of 3m-10m from the machine plane (T), the height (h) being measured from the surface level of the mass in the venting tank (T) to the machine plane. . . Ventilation arrangement according to claim 1 or 2, characterized in that • ·. "The device which produces the vacuum in the vent tank (11) is a fan (13) and that between the vent tank (11) and the fan (13) there is no condenser, but only a drip separator. (14) as water separators • · · • · · · · years. 4. A venting arrangement according to claim 1, 2 or 3, characterized in that a machine screen (15) is arranged between the wire well (12) and the venting container (11), advantageously in the channel (a2) between the vortex cleaning plant ( 16) and: ·. the vent container (11). • · Venting arrangement according to any of the preceding claims, characterized in that the wire well (12) is arranged below the machine plane (T) and that the height (H) difference (H) between the surface of the pulp or the water of the wire in the wire well (12) and the surface 8 of the pulp or wire water in the vent container (11) is within the range of 4m-8m. Ventilation arrangement according to claim 1, characterized in that from the wire well (12) a channel (ai) leads to the swirl cleaning plant (16) and from the swirl cleaning plant (16) likes a channel to the venting tank (11) for the pulp from which flute is removed by means of of the negative pressure created in the venting vessel and that from the venting vessel (11) likes a channel (as) for overflow back to the wire well (12) and that wire water is led to the wire well (12) from the wire part through a channel (b2) and that fresh mass is conducted through a channel (bi) to the viral well (12). The venting arrangement according to claim 1, characterized in that from the wire well (12) a duct (ai) leads directly to the venting vessel (11), in which air is removed from the venting water by means of vacuum and that the venting vessel (11) likes a duct (a2) to the vortex cleaning plant (16), from which the pulp is passed as acceptance further pumped by a pump (Pi) to a machine screen (15) and. . further to the inlet carriage (10) of the paper machine, and that fresh pulp is measured to a • I In duct (a2) between the vent container (11) and the swirl cleaning plant (16) • · * .. *. 20 to the suction side of a pump (P3). • • • • • • • • • • * * ♦ ♦ · · · · · · · · · t