WO2003023135A1

WO2003023135A1 - Deaeration arrangement in connection with a paper machine or equivalent

Info

Publication number: WO2003023135A1
Application number: PCT/FI2002/000705
Authority: WO
Inventors: Matti Hietaniemi
Original assignee: Metso Paper, Inc.
Priority date: 2001-09-07
Filing date: 2002-09-02
Publication date: 2003-03-20
Also published as: FI20011780A; FI20011780A0; FI111467B

Abstract

The invention relates to a deaeration arrangement in connection with a paper machine or equivalent. The apparatus arrangement comprises a deaeration tank (10) which has a vacuum and between which deaeration tank (10) and a wire pit (12) there is a line (15) through which the stock/wire water from the wire pit is passed to the deaeration tank (10). In the apparatus arrangement, the stock/wire water from which air has been removed is passed from the deaeration tank (10) further to a headbox (11) of the paper machine or equivalent.

Description

Deaeration arrangement in connection with a paper machine or equivalent

The invention relates to a deaeration arrangement in connection with the short circulation of a paper machine or equivalent.

If it is desired to build the short circulation such that it comprises a deaeration tank for wire water, a large pump with a small delivery height would be needed for feeding wire water into the deaeration tank. However, the availability of such pumps is poor and, thus, a greater delivery height must be chosen for the pump.

The large feed pump between the deaeration tank and the wire pit could be removed from the process if the feed flow of the deaeration tank could be adjusted by another means. This can be arranged in accordance with the invention such that a small circulation flow is pumped from the deaeration tank to the preceding process. Control of the circulation flow can be connected, for example, with the surface regulation of the wire pit. In that connection, it would also be possible to place the deaeration tank at a lower level than at present and to save in building costs. In the arrangement, it would not even be necessary to give up the overflow that provides stability.

In the deaeration arrangement in accordance with the invention in connection with a paper machine or equivalent, the deaeration arrangement comprises a circulation line from the deaeration tank and, in the circulation line, a circulation pump, by means of which pump part of the stock/wire water passed to the deaeration tank is circulated back. The deaeration arrangement according to the invention is characterized by the disclosure in the claims. The arrangement in accordance with the invention can be used in removal of air from wire water and when air is removed from the stock that has already been diluted to headbox consistency.

In this invention, by the wire pit is meant a chest into which wire water discharged from the paper machine or equivalent is passed.

In the following, the invention will be described with reference to some advantageous embodiments^' of the invention shown in the figures of the appended drawings, but the invention is not meant to be exclusively limited to these embodiments.

By the paper machine or equivalent is meant paper, board and tissue machines.

Figure 1 A shows a deaeration arrangement situated in the short circulation of a paper machine in accordance with prior art.

Figure IB shows a first advantageous embodiment of the invention, in which a circulation line is connected from a deaeration tank to the main stock supply line between a wire pit and the deaeration tank.

Figure 1C shows an embodiment of the invention in which a circulation line is connected from an overflow of a deaeration tank to the main line between a wire pit and the deaeration tank, and in which apparatus arrangement the wire pit is additionally provided with an overflow.

Figure ID shows an embodiment of the invention in which a circulation line comprises a circulation water chest and in which, with respect to the flow of the circulation line, the line portion after the circulation water chest is connected directly to a wire pit, advantageously close to the inlet of wire water. Figure IE shows an embodiment of the invention in which a hydrocyclone of a cleaning step of a hydrocyclone installation is arranged in the main stock supply line between a wire pit and a deaeration tank, in which connection the accept line from the hydrocyclone is connected to the deaeration tank, and in which apparatus arrangement a circulation line arranged to lead from an overflow of the air cleaning tank and comprising a circulation pump is connected to said accept line.

In the prior art arrangement in Fig. 1 A, a line is arranged to lead from a wire pit to a hydrocyclone installation, which in Fig. 1 A is designated by the letter F and, as illustrated in the figures, the accept from a step Fi of the hydrocyclone installation is passed to a deaeration tank 10. From an overflow of the deaeration tank there is a return flow back to the wire pit and the stock which has been treated is passed further after deaeration from the deaeration tank 10 to a feed pump P₀ of a headbox 11 and further along a line Y to the headbox 11. A vacuum pump V sucks a vacuum into a tank space Di of the deaeration tank 10. The upper level Ti of the stock in the deaeration tank 10 is at a height of 10-18 metres above the surface level T₂ of wire water. As shown in the figure, wire water is passed from a wire section (not shown in the figure) along a line 13a to the upper part of a wire pit 12. Thick stock is passed into the wire pit through a line 13b and a combined flow is passed by means of a feed pump Pi to the hydrocyclone installation F and further from its step Fi to the deaeration tank 10.

A problem in the prior art arrangements has been the great delivery height required from the stock feed pump Pi and its regulation. The availability of such pumps is poor and they are expensive to procure and use.

Figs. IB- IE show some advantageous embodiments of the invention. Typically, all embodiments comprise a wire pit 12 and a main flow line 15 for stock/wire water between the wire pit 12 and a deaeration tank 10. In the embodiments illustrated, the deaeration tank 10 is provided with a vacuum by means of a device V, which is advantageously a vacuum pump. The vacuum pump V is situated in a pipe line M, which pipe line M opens into a stock space Di inside the deaeration tank 10. From the space Di there is a return line Y for the stock/wire water from which air has been removed further to a headbox 11 through a headbox feed pump

Po.

In accordance with the invention, as shown in Fig. IB, a return flow arrangement is provided from the deaeration tank 10 to the supply line 15 of the stock deaeration tank 10. Said circulation flow is produced by means of a pump 17, which is in a circulation line 16. By adjusting said circulation flow in the line 16, the flow of the stock/wire water caused to flow along the main line 15 to the deaeration tank 10 is adjusted. The line 15 is situated between the wire pit 12 and the deaeration tank 10. In the arrangement in accordance with the invention, a separate stock feed pump is not needed in the line 15 leading to the deaeration tank 10, but, instead, the feed is made possible by the pump 17 provided in the circulation line 16. The circulation line 16 is connected at its upper end to the deaeration tank 10 and, in the embodiment, opens into its stock tank space Di. At its other end, the line 16 is connected to the main line 15 for stock/wire water.

In the arrangement shown in Fig. IB, the circulation pump 17 is regulated according to the level T₂ of the surface in the wire pit 12, which level is measured by a detector device 18. The wire pit 12 itself does not need any overflow, but the surface of the wire pit 12 is adjusted by regulating the pump 17 situated in the circulation line 16. Regulation is received from the surface level T₂ of the wire water of the wire pit 12 measured by the detector device 18. The detector device is designated by the reference numeral 18 and a signal line between the detector device and the pump 17 is designated by the reference numeral 19. The deaeration tank 10 itself does not comprise any overflow in the embodiment of Fig. IB, but the stock/wire water from the deaeration tank is passed to the headbox 11 of the paper machine along the line Y. If air is removed only from wire water in the deaeration tank, thick stock 13c is introduced into the wire water for dilution advantageously prior to the headbox feed pump P₀. The thick stock is diluted to headbox consistency in that connection. The headbox feed pump P₀ is situated in the stock/wire water outlet line Y. The space inside the deaeration tank 10 is provided with a vacuum, for example, by the vacuum pump V, which is situated in the pipe line M opening into the space inside the tank 10.

Fig. 1C shows an embodiment that corresponds to that of Fig. IB except that in the arrangement of the figure the wire pit 12 comprises an overflow 20 and the deaeration tank 10 also comprises an overflow 21. The overflow 21 is formed in connection with the stock space Dj, the tank 10 including a partition wall S over which the stock flows further to a circulation line 16. The space inside the vacuum tank 10 is provided with a vacuum by means of the pump V which is situated in the pipe line M opening into the space inside the tank 10.

In connection with the overflow 21 of the deaeration tank 10 there is a detector device 18, by means of which a circulation pump 17 situated in the circulation line 16 is regulated depending on the flow quantity of the overflow 21. The detector 18 thus observes the quantity of the flow passing through the overflow

21. The reference numeral 19 designates a signal line between the detector device

18 and the pump 17. In the embodiment, the difference of height between the surface levels T_\ and T of the wire water in the wire pit and the stock in the deaeration tank 10 is 5-10 metres. The circulation line 16 is connected at one end thereof to the overflow 21 of the deaeration tank 10 and, at the other end thereof, said circulation line 16 is connected to the stock line 15 between the wire pit 12 and the deaeration tank 10, which line 15 is the main line for the stock/wire water to the deaeration tank 10.

Fig. ID shows an embodiment that corresponds to that of Fig. IB except that the arrangement in the embodiment comprises a circulation water chest 22, so that a circulation water line 23 is formed by an overflow line 23aι arranged to lead from an overflow 21 of the deaeration tank 10 to the circulation water chest 22 and by a return line 23 a₂ arranged to lead from the circulation water chest 22 to a wire water inlet Ji of the wire pit 12. The flow from the wire pit 12 to the line 15 and further to the deaeration tank 10 is adjusted by operating a pump 17 situated in the return line 23a₂. Regulation of the pump 17 in the circulation line 23aj, 23a₂ takes place by means of a detector device 18 observing the level T₂ of the surface of the wire water in the wire pit 12. There is a signal line 19 from the detector device 18 to the pump 17. In the embodiment of the figure, the difference of height between the surface T₂ of the wire water in the wire pit and the level

of the surface of the stock in the deaeration tank is 5-10 metres. In the embodiment of this figure, too, a vacuum is sucked into the space Di inside the tank 10 by means of the vacuum pump P through the pipe line M. The overflow 21 comprises a partition wall S. From the tank space Di inside the tank 10, into which the stack is passed, there is the return line Y, advantageously via water dilution, to the headbox 11.

Fig. IE shows an embodiment of the invention in which the deaeration tank 10 comprises an overflow 21 and a circulation line 16 comprises a circulation pump 17 which receives its regulation based on the observation of a detector device 18 situated in the overflow 21. The circulation line 16 is arranged to lead from the overflow 21 of the deaeration tank 10 to a line 15a₂, i.e. to an accept line 15a₂ arranged to lead from a cleaning step F] of a hydrocyclone installation F to the deaeration tank 10. The accept line 15a₂ is between a hydrocyclone 100 of the first step Fi of the hydrocyclone installation and the deaeration tank 10. Thus, in this embodiment, in the line 15 between the wire pit 12 and the deaeration tank 10 there is the hydrocyclone installation F, its first hydrocyclone step Fi. From the wire pit 12 there is the line 15a] to the step Fi of the hydrocyclone installation F and further to the hydrocyclone 100 of the step Fi. From the hydrocyclone 100 there is the accept line 15a₂ further to the deaeration tank 10. There is a pump P_to in the line between the wire pit 12 and the hydrocyclone installation F. The difference of height between the surface level T₂ of the wire water in the wire pit 12 and the surface level T| of the stock in the deaeration tank is 10-18 metres. Wire water from the wire section is passed to the wire pit 13 and thick stock is passed to the lower part of the wire pit 12, in which connection a combined flow Li is passed, pumped by the pump P₁₀, along the line 15aι to the first step F] of the hydrocyclone installation F. For the sake of illustration, the figure shows only one hydrocyclone 100 of the hydrocyclone step Fi of the hydrocyclone installation by way of example. The wire water to the wire pit 12 is passed through a line 13a and thick stock is passed through a line 13b. In the embodiment of this figure, too, a vacuum is sucked into the space Dj inside the tank 10 by means of the vacuum pump V situated in the pipe line M, which pipeline opens into the deaeration tank 10. The overflow 21 comprises a partition wall S. From the space Di there is a return line Y for the stock from which air has been removed. The stock is passed through the headbox feed pump P₀ and advantageously through water dilution along the line Y further to the headbox 11.

In the apparatus arrangements of Figs. IB-IE in accordance with the invention, the stock/wire water passed from the deaeration tank 10 along the circulation line 16, 23 is thus used for regulating the feed flow of the deaeration tank 10.

In the apparatus arrangements of Fig. IB, Fig. 1C, Fig. ID in accordance with the invention, pressure is not increased by a pump or any other process device between the wire pit 12 and the deaeration tank 10 subsequent to this in the process.

Claims

1. A deaeration arrangement in connection with a paper machine or equivalent, the apparatus arrangement comprising a deaeration tank (10) which has a vacuum and between which deaeration tank (10) and a wire pit (12) there is a line (15) through which the stock/wire water from the wire pit is passed to the deaeration tank (10), in which apparatus arrangement the stock/wire water from which air has been removed is passed from the deaeration tank (10) further to a headbox (11) of the paper machine or equivalent, characterized in that the deaeration arrangement comprises a circulation line (16; 23) from the deaeration tank (10) and, in the circulation line, a circulation pump (17), by means of which part of the stock/wire water passed to the deaeration tank (10) is circulated back to the line (15) leading to the deaeration tank (10) of the stock/wire water or to the wire pit (12). (FIG. IB, FIG. 1C, FIG. ID, FIG. IE)

2. A deaeration arrangement as claimed in claim 1, characterized in that the circulation line (16) is connected at one end thereof directly to a tank space (Di) of the deaeration tank (10) and at the other end thereof to the line (15) between the wire pit (12) and the deaeration tank (10). (FIG. IB)

3. A deaeration arrangement as claimed in the preceding claim, characterized in that there is a detector device (18) and a signal line (19), the detector device (18) being disposed in connection with the wire pit (12) to observe the liquid level (T₂) prevailing in the wire pit (12), in which connection the circulation pump (17) is regulated based on said liquid level (T₂), the detector device (18) being connected through the signal line (19) to regulate the circulation pump (17). (FIG. IB)

4. A deaeration arrangement as claimed in claim 1, characterized in that the circulation line (15) is connected at one end thereof to an overflow (21) of the deaeration tank (10) and at the other end thereof to the line (15) between the wire pit (12) and the deaeration tank (10), and that the circulation pump (17) receives regulation from a detector device (18) which is situated in connection with the overflow (21) of the deaeration tank (10) and which observes the flow to the overflow (21), and that a signal line (19) from the detector device (18) is connected to the circulation pump (17) to regulate it. (FIG. 1C)

5. A deaeration arrangement as claimed in the preceding claim, characterized in that the wire pit (12) comprises an overflow (20). (FIG. 1C)

6. A deaeration arrangement as claimed in claim 1, characterized in that the deaeration arrangement comprises a circulation line (23) and in it a circulation water chest (22), a circulation pump (17) being in a line (23a₂) situated after the circulation water chest, and that the circulation line (23a₂) is connected at one end thereof to the circulation water chest (22) and at the other end thereof to the wire pit (12), advantageously to its wire water inlet (Jj), and that the circulation pump (17) receives its regulation from a detector device (18) which observes the level (T₂) of the wire water in the wire pit (12), and that there is a line (23aι) to the circulation water chest (22) from an overflow (21) of the deaeration tank (10). (FIG. ID)

7. A deaeration arrangement as claimed in claim 1, characterized in that the main line (15) of the stock/wire water to the deaeration tank (10) comprises a line portion (15aι) from the wire pit (12) to a hydrocyclone (100) of a hydrocyclone step (Fi) of a hydrocyclone installation (F), and that said line (15aι) comprises a pump (Pio), and that from the hydrocyclone (100) of the hydrocyclone step (FI) there is an accept line (15a₂) to the deaeration tank (10), and that from an overflow (21) of the deaeration tank (10) there is a circulation line (16) which comprises a circulation pump (17), which circulation line (16) is connected to said accept line (15aι), and that the circulation pump (17) receives its regulation from a detector device (18) which is disposed in the overflow (21) of the deaeration tank (10), a signal line (19) being connected to the circulation pump (17) and, on the other hand, to the detector device (18), the circulation pump (17) receiving its regulation from the detector device (18) which is disposed in the overflow (21) and which measures the flow quantity through the overflow (21). (FIG. IE)

8. A deaeration arrangement as claimed in claim 1, characterized in that pressure is not increased by a pump or any other process device between the wire pit (12) and the deaeration tank (10) subsequent to this in the process.

9. A deaeration arrangement as claimed in claim 1, characterized in that the feed flow of the deaeration tank is adjusted by means of the stock/wire water passed from the deaeration tank (10) along the circulation line (16, 23) .