FI104643B - Process arrangement for the short circulation in a paper or cardboard machine - Google Patents

Abstract

A process arrangement comprises cleaning devices 130, 150, 160, 170, water collection devices 101, 102, 115, 120, deaeration devices 140, 180, pumps 31, 41, 121, 141, 142, a head box 90 and a wire part 100, and pipelines with control devices connecting the devices. Pulp MT is fed from a machine tank 40 to a dilution water tank 140 on the head box, from which the pulp diluted to head box consistency is fed by a feed pump 141 on the head box directly to a distributing boom on the head box 90. The water that is collected from the wire part 100 and an overflow F142 from the dilution water tank 140 on the head box is led to a filtrate water tank 120, from which a dilution water flow F130 is fed by a first filtrate water pump 121 to a water strainer 130, the accept F130 from which is fed to the dilution water tank 140 on the head box. <IMAGE>

Description

1,046.43

Paper or board machine short cycle process arrangement Processarrangemang för den card circularen i en pappers-eller board mask r-5

The invention relates to a short cycle process arrangement for a paper or board machine as defined in the preamble of claim 1.

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The pulp feeding of a paper machine is generally as follows. Massak components are stored at the factory in separate storage tanks. From the storage tanks, the pulps are fed to the metering tanks and then to a common mixing tank where the pulp components are mixed. From the mixing tank the pulp is fed to the machine-15 tank and there is an overflow from the machine tank back to the mixing tank. Generally, the pulp from the machine tank at a consistency of about 3% is fed to a short-circuited wire well. In a wire well, the thick mass is diluted to a headbox consistency, which is generally about 1%.

20 Fibers and fillers, which serve as the raw material, are introduced into the wire by water through a headbox. The filtrate, which has passed through the wire and is rich in fiber and fillers, is returned to the wire through the headbox by diluting the thick pulp from the machine container. The flow loop thus formed is called a short loop. Short rotation, together with the associated headbox, is generally considered to be the most sensitive part of the papermaking process. Even small changes in consistency, flow, or other parameters immediately affect the quality of the paper being produced or cause web breaks in the paper machine.

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With the thick mass or otherwise, impurities that may have to be removed before the headbox may be circulated for a short time. This is done by short-cycle cleaning devices such as vortex cleaners, sorters and machine screens.

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The object of the invention is to provide a short rotation suitable for a paper or board machine without the need for a machine screen.

The main features of the short cycle process arrangement · 5 of a paper or board machine according to the invention are set forth in claim 1.

The short cycle process arrangement according to the invention can be applied to both paper and board machines. The board machine can run several parallel short-cycle process arrangements of the invention simultaneously.

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In the solution according to the invention, the conventional wire well has been removed. All water collected from the wire section and press section is directed to the filtrate water tank. Because no wire well is needed, the solution becomes cheaper than current solutions. Current moniker jets have a wire well on each floor, extending from the ground floor to the height of each of the 15 water collection plates. The location of the traditional wire well is tied to the position of the water collection plate of the wire section, but the filtrate water tank can be placed more freely. In the solution according to the invention, an effective deaeration with e.g. a cyclone is added to the water flow from the water collection plate to the filtrate water tank.

Effective venting improves end product quality and machine runnability.

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In the solution according to the invention, all m 3 <water used for short circulation and sorting is cleaned with a screen and passed to a headbox dilution water tank. The dilution water tank, which is closest to the conventional wire well, is spherical, vacuum-proof, and is provided with a venting fan. The mixing of pulp and water in the dilution water tank takes place through tubes similar to those of a conventional wire well, with ideal velocity-acceleration ratios. In addition, the dilution water tank is designed to prevent impurities. The overflow of the dilution water tank is led back to the filtrate water tank. The pulp is pumped from the machine tank through the stern dilution water tank to the stern feed pump. The size of the stern dilution water tank 30 is smaller than the corresponding wire well. With multilayer machines, all tanks are of the same height. The height of the dilution water tank is determined by the desired vacuum and the suction height required for the aft pump. The dilution water tank can be installed without any after-casting. With this arrangement, the length of the polished stern feed tube can always be minimized and its shape optimized. The placement of a traditional wire well is tied to the water collection plate of the wire section. In the solution according to the invention 5, the headbox dilution water tank can be located according to the ideal position of the stern feed pump. Efficient venting with a blower can be added to the dilution water tank. In the solution according to the invention, the water does not get dirty in circulation because only the overflow back to the filtrate water tank is open. All consistency adjustments are constant pressure because the suction heights of the pumps are constant. This will minimize pressure fluctuations and achieve accurate consistency control.

In the solution according to the invention, the incoming pulps are cleaned with suitable slit separators in a suitable sorting consistency. There are 3-4 sorting steps according to need.

Acceptances of 1-2 sorting stairs can always be advanced to the main line. Sorting takes place under conditions that are better for sorting, i.e., using higher rejection ratios than those used in machine screening and subsequent sorting.

The pulps may be sorted in suitable consistency for sorting using suitable sorters. The pulp is pure and the screeners smaller than the machine screen and its reject screeners combined. No need to worry about pulsation, no need to polish the sorters, no need to increase the structural pressures of the 2 0 sorters.

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The mass sorters are controlled as follows:

Acceptance is controlled by pulp dosing, i.e. flow control (vir-25 metering, flow control valve).

The reflux is normally controlled by flow control relative to the accept flow

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:; (flow measurement, flow control valve).

, - Dilution water is fed to the bottom of the sorted and in multi-stage sorting, it is always fed to each stage. Intermediate dilutions are made as flow-controlled-30 (flow measurement, flow control valve).

The feed consistency of the first stage pulp is adjusted.

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The water strainer has flow controls but no consistency control.

The feed pressures are not regulated.

In the solution of the invention, the mixing tank and the machine tank are closed like a 5 stern dilution water tank. Only the overflow of the mixing tank leaving the system is open. All the pulp used and all the filtrate water used are thus sorted. The mass does not get dirty in the cycle because there are no open points. There is no "spinning" problem here once all the pumped material has been cleaned. The "spinning" phenomenon refers to the forming of wire in machine sieves. On the acceptor side of the machine screen drum ίο grows wire-like formations, which at times leave the machine, causing breakage or holes, etc. The mixing and machine tank installation can be done without any casting.

In the solution of the invention, the excess water is used for other consistency adjustments and the rest is cleaned with a filter, as is the case today.

If the solution according to the invention requires sand removal from the pulp, it can be done before or during sorting.

2 The economic and equipment benefits of the invention can be summarized as follows:

Because of the small size and free space of the stern dilution water tank, it becomes inexpensive and can be placed in an ideal location for the stern flow shape.

Because of the high volume flow rates of the short circulation, the devices therein are also large: and when sorting at a high consistency, the devices can be reduced.

Because the water and pulp circuits are closed, impurities are prevented from entering machine 3 0, resulting in better quality and fewer breaks.

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For sorting, tighter slotted drums can be used than can be used in machine sieves.

You can better control the spinning problem.

The arrangement as a whole is also cheaper than the traditional arrangement.

In the following, some preferred embodiments of the invention will be described with reference to the figures in the accompanying drawings, in which details, however, are not intended to be limited.

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Figure 1 schematically illustrates a conventional prior art papermaking process for a papermaking machine.

Figure 2 schematically illustrates a process arrangement for a short-cycle paper machine according to the invention.

Figure 3 schematically shows a modification of the paper machine short cycle process arrangement shown in Figure 2.

Figure 4 shows a headbox dilution water tank suitable for the process arrangement of the invention.

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Figure 1 schematically illustrates a conventional prior art papermaking process for a papermaking machine. Partial Mj is supplied from the storage tank 10 by a first pump 11 to a dosing tank 20. In its part, a dilution-water flow F10 is introduced into the inlet side of the first pump 11. In addition, the partial mass is diluted at the bottom of the mass atom 10 by the dilution water flow F9 introduced therein. Dosage from the feed tank 20 at the partial mass Mj is supplied by a second pump 21 via a control valve 22 to a process line 23 leading from the mixing tank 30 to a third pump 31 to a machine tank 40. From the machine tank 40 the pulp is fed through the second control valve 42. The machine tank 104643 6 slurry 40 further has an overflow 43 back to the mixing tank 30. The mixing tank 30 and the machine tank 40 form a mass equalizer and are diluted therein to the final dispensing consistency. In addition, they ensure uniform dispensing of the machine mass. · 5

Dispensing of the partial masses Mj into the mixing tank 30 takes place in such a way that the constant height of the mixing tank 30 is constantly maintained. Based on the surface changes measured by the mixer tank level-height sensor, the level control calculates the total mass required for metering, which data is fed into the metering metering section of the partial mass. In addition, a predetermined mass fraction value and a fraction mass consistency value are fed to the dosing control block.

From the mixing tank 30, the pulp is fed at a constant rate by a third pump 31 to the machine tank 40. In this pumping step, the consistency of the pulp is also adjusted to the desired consistency of the machine tank. This is done by a dilution water flow F30 fed to the suction side of the third pump 31. The dilution water flow F30 dilutes the mass at about 3.2% consistency in the mixing tank 30 to a final dosing consistency of about 3%.

The basis weight control is effected such that the basis weight regulator controls the control valve 42 after the fourth pump 41. This control valve 42 controls the flow rate of the short-circuited pulp, which in turn affects the basis weight of the paper web from the papermaking machine. Increasing the flow rate increases the basis weight and decreasing the flow decreases the basis weight.

25th In a short rotation, the headbox 90 feeds through the lip opening a pulp suspension to the wire jet section 100. The section 100 has water collection means for conducting a flow of water exiting the wire through f50 into a well 50. %. In the wire well, 50 fresh pulp is diluted to a headbox consistency of the order of 1%. The suction side of the fifth pump 51 • <104643 7 is connected to the mixing zone 50a of the wire well 50. From the pressure side of the fifth pump 51, a mass flow rate F60 diluted to the headbox consistency is directed through the vortex cleaners 60 to the venting tank 70.

The venting container 70 has a vacuum air above the free surface of the pulp.

5 The height of the pulp surface is determined by the overflow 71 of the venting tank 70 over which the deflated mass flow F70 flows. This mass flow F70 is led to the mixing area 50a of the wire well 50. Further, a return stream from the vortex purifiers and a fresh mass flow MT are introduced into said mixing zone 50a. A mass flow F7J is led from the bottom of the venting vessel 70 to the suction side of the sixth pump 71. This sixth pump 71 feeds the inlet mass flow through Fin machine screen 80 to the manifold 90 manifolds. The bypass flow Fout of the headbox 90 manifold is returned to the lower portion of the venting container 70. The machine screen 80 reject Fgl is led to reject processing.

The water flow Fsi collected from the suction strips of the wire section 100. is supplied to a circulating water tank 110, 15 to which is also fed an overflow F52 of the wire well 50 and the recovered water Fp from the press section. From the circulating water tank 110, water is fed by a seventh pump 111 as a flow Fnj for fiber recovery and an eighth pump 112 as a flow Fjj for consistency adjustments.

Figure 2 is a schematic diagram of a short circuit process arrangement of a papermaking machine according to the invention. In this process arrangement, three pulp screeners 150, 160, 170 are used, preferably tight slot separators for pulp purification. In this process arrangement, the conventional wire well 50 shown in Figure 1 is replaced by a filtrate water tank 120 to which the water collected from the wire section 100 and the press section Fp 25 is directed. The mass MT is fed here from the machine reservoir 40 to the headbox dilution water tank 140, from which the mass diluted to the headbox consistency is fed directly by the headbox feed pump 141 to the headbox 90. Thus, the machine screen 80 shown in FIG.

The mass M of the particle masses is fed to the first pulp screen 150, whose accept F150 is fed to the suction side of the pump 104643831 between the mixing tank 30 and the machine tank 40. The pump 31 feeding the machine container 40 supplies pulp to the top of the machine container 40 and the machine container 40 has an overflow F40 back to the mixing container 30. The overflow F31 is discharged from the mixing container 30 into the process. The pump 41 following the machine tank 40 is used to deliver pulp MT to the lower portion of the dilution water tank 140 of the headbox. From the lower part of the headbox dilution water tank 140, the mass diluted to headbox water pump is fed to the headbox feed pump 141 to the headbox 90 manifold, from where the mass is fed through headbox 90 and the headbox 90 lip ίο where the water is dehumidified by a fan. Water from the cyclone 180 air is led to filtrate water tank 120. The web forming section 100, under vacuum, strips 102 to collect the dewatered water into the equalization tank 115, from where it is discharged to the filtrate water tank 120.

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Water from the leachate water tank 120 is fed by a first leachate water pump 121 to a leachate water separator 130 whose accept F130 is led to the top of the headbox dilution water vessel 140, where the water is deaerated under reduced pressure. Water from the filtrate water tank 120 is also fed by a second filtration water pump 122 to the recovery of fiber 20 F120 and the consistency adjustments F121.

From the headbox dilution water tank 140, a water flow F141 is led to the suction side of the pump 31 between the mixing tank 30 and the machine tank 40, and to the suction side 142 of the pump 142 feeding the second screen. Further, on the inlet side of the pump 31 between the mixing tank 30 and the machine reservoir 40, the acceptor F150 of the first pulp sorter and the F160 of the second pulp separator are provided. further providing a reject F151 of a first pulp screen 150, an accept F170 of a third pulp screen 170 and a reject F131 of a filtrate water screen 130. The reject F161 of the second pulp sorter 160 is led to the third pulp sorter 170. The reject F171 of the third pulp sorter 170 is taken out of the process for processing rejects.

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Filters 150, 160, 170 are further fed with a pump (not shown) of fiber. from the clear filtrate after recovery, the dilution water flow FL, which dilutes the pulp to be fed to the separators 150, 160, 170. This dilution water flow FL is fed to the reject space of the mass sorters 150, 160, 170, which is located below the point of entry of the mass to be physically fed to the mass sorter 5 and the point of acceptance of acceptance from the mass sorter.

In the short circuit shown in Fig. 2, the water from the wire section 100 and the press section and the overflow from the headbox dilution water tank 140 to the filtrate water tank 120 are collected. The water from the filtrate water tank 120 is pumped 121 through a water separator 130 to the top of the 41 masses of MT machine tank 40 are pumped into the mixing section at the bottom of the headbox dilution water tank 140, 141 masses are pumped from the bottom of the headbox dilution water tank 140 into the headbox 90 manifolds.

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Figure 3 shows a modification of the embodiment of Figure 2. In contrast to the embodiment of FIG.

Figure 4 is an enlarged view of the headbox dilution water tank 140 shown in Figures 2 and 3. The dilution water tank 140 consists of a cylinder 140a, a hemispherical 25-shaped base 140b, and a hemispherical lid 140c. Attached to the ball cap 140c is a cylindrical vacuum tube 140d extending from the ball cap 140c to a distance within the cylinder 140a. The spherical cap 140c has a valve 140e at the vacuum tube 140d through which air can be vented from the vacuum tube 140d. Further, the dilution water tank 140 has an annular overflow tray 140f. Water is supplied to the dilution water tank 140 from the first inlet pipe 140g, which extends to the vacuum pipe 140d. The ballast base 140b is connected to a dilute mass outlet tube · 104643 10 1401, from which the mass entering the headbox is taken. The pulp outlet tube 1401, in turn, is provided with a pulp feed tube 140k into which the pulp to be pumped from the machine tank is fed. These form a traditional structure used in wire wells for ideal mixing conditions. From the other 5 outlet pipes 140h of the dilution water tank 140, diluent water can be supplied to the suction side of the pump feeding the machine tank and to the suction side of the pump which supplies the second screen. The difference between the surface heights h of the liquid in the vacuum tube 140d and the liquid in the dilution water tank 140 outside it is determined by the vacuum pressure drawn into the vacuum tube 140d.

In the solution according to the invention, the construction principle of the dilution water tank shown in Figure 4 is also used in the mixing and machine tank. The ratio of diameters to height of the mixing and machine container is preferably about 1. In order to achieve good mixing, a mixer 33, 43 is further fitted to the lower part of the mixing and machine container to enhance the mixing of the pulp.

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The control principles of the apparatus according to the invention shown in Figures 2-3 will now be described.

Partial masses are fed from their metering tanks, based on flow / consistency controls, to the suction side of the first 20 pulp screeners 150 (not shown). A predetermined proportion of the total feed stream of the first pulp screen is fed to each partial mass. Partial masses are usually dosed at the same consistency.

Particle mass pulp M is fed to the first pulp screen 150 150 at a sufficiently high consistency to maintain a desired constant pulp consistency of from about 2.5% to about 3.5%, and preferably about 3%, in machine container 40. Dilution: In the water tank 140, the pulp is diluted to a headbox consistency of between 0.2 and 1.5% depending on the paper machine. The acceptance flow rate F150 of the first pulp screen 150 is adjusted based on the surface height of the mixing tank 30, the objective 30 being to maintain a constant surface height in the mixing tank 30. The consistency of the acceptance stream F150 of the first pulp screen 150 After the first mass screen. The consistency of 150 feed pulp M is sufficiently high that the consistency of feed pulp 40 to the machine reservoir 40 can be adjusted and kept constant by the dilution water flow Fj4i »F123.

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The acceptance flow F160, F170 of the second 160 and the third 170 bulk sorters are controlled by pressure, i.e. a predetermined constant pressure is maintained in the acceptance line. The pressure level of the acceptor line of the second 160 and the third mass selector 170 is not normally changed, but if, for one reason or another, the rejection of the acceptor line does not provide sufficient reject, the pressure level of the acceptor line is corrected.

The first flow sorter 150 has an acceptance flow F150 of about 3.5%, a second bulk screen 160 has an acceptance flow F160 of about 3%, and a third bulk screen 170 has an acceptance flow F170 of about 0.8-1.5% where the container 40 is 3%. The consistency of the pulp fed to the second pulp screen 160 is generally slightly lower than that of the acceptance stream F150 of the first pulp screen 150 due to the diluting pulp / water cycles entering the second pulp screen 160. The consistency of the pulp fed to the third pulp screen 170 is maintained lower than that of the pulp to the second pulp screen 160 by introducing a dilution water flow into said feed.

The reject flow rates F151, F161, F171 of the bulk sorters 150, 160, 170 are, in principle, controlled by the mass flow rate of the mass to be fed to the mass screen. In practice, however, the rejection flow F15j, Fjgj, Fj71 is controlled directly on the basis of the acceptance stream F150, F160, F17q obtained directly from the pulp sorter. Third pulp sorter. The 170 rejection flows F171 are controlled by a periodic valve. The valve is normally, normally at its set point, and will occasionally open completely or alternatively the valve may be fully closed and at times fully open.

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The consistency of the pulp fed to the machine tank 40 is adjusted in a conventional manner by measuring the pulp consistency at the pressure side of the pump 31 feeding the machine container 40 and adjusting the dilution water flow to the suction side of said pump 31 F14I, F123 · 5

The mass flow MT, which is fed to the headbox dilution water tank 140, is conventionally controlled by the basis weight valve 42 or by adjusting the rotational speed of the pump 41 after the machine tank 40.

The claims which follow, within the scope of which the inventive idea is defined, may vary from the foregoing by way of example only.

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Claims (14)

A process arrangement for the short circulation in a paper or cardboard machine, which comprises purification devices (130, 150, 160, 170), water collecting devices (101, 102, 115, 120), venting devices (140, 180), pumps (31, 41, 121, 141, 142), an inlet carriage (90) and a wire portion (100), and the connecting pipes with control devices, characterized in that mass (MT) is measured from a machine container (40) to a dilution water tank (140) at the inlet carriage; 130), whose acceptance (F130) is measured in the dilution water container (140) at the inlet carriage, that mass is measured from the dilution water container (140) at the inlet carriage with a feeder pump (141) at the inlet carriage for a distribution tank m at the inlet carriage (90). Process arrangement according to claim 1, characterized in that also an overflow (F142) from the dilution water container (140) at the inlet carriage is led to the filtrate water tank (120). 20 Process arrangement according to claim 1 or 2, characterized in that the wire water collected without vacuum from the wire part (100) is led into a cyclone (180), in which air is removed from the water by a fan, after which the water is led into the filtrate water tank (120). . 25 Process arrangement according to any one of claims 1-3, characterized in that the wire water collected by means of vacuum from the wire part (100) is led to an equalizing water container (115), from which the water is passed to the filtrate water tank (120). 30 104643 17 Process arrangement according to any of claims 1-4, characterized in that, the water (Fp) collected from a press section is led to the filtrate water tank (120). Process arrangement according to any one of claims 1-5, characterized in that sub-masses are measured from the dosing container for sub-masses to a first screen (150), whose acceptance (F150) is measured at the suction side of a pump (31) supplying the machine container (40) reject (F151) to the suction side of a pump (142) which feeds a second screen (160). ίο Process arrangement according to any of claims 1-6, characterized in that the acceptance (F160) from the second screen (160) is measured at the suction side of the pump (31) which feeds the machine container (40) and the reject (F161) from the second screen ( 160) measure into a third screen (170). ice Process arrangement according to any of claims 1-7, characterized in that the acceptance (F170) from the third screen (170) is measured to the suction side of the pump (142) which feeds the second screen (160) and the reject (Fm) to the reject processing. Process arrangement according to any of claims 1-8, characterized in that the reject (F131) from the water screen (130) is led to the suction side of the pump (142) which feeds the second mass sieve (160). Process arrangement according to any of claims 1-9, characterized in that the dilution water (FL) is additionally measured in the first (150), the second (160) and the third (170) mass dilution water (FL). »· · Process arrangement according to any of claims 1-10, characterized in that • water is measured from the filtrate water container (120) with a second filtrate water pump (122) for fiber recovery (F120) and consistency control (F121). 30 104643 18 Process arrangement according to any of claims 1-11, characterized in that a mass flow (F141) is measured from the dilution water container (140) at the inlet carriage to the suction side of the pump (31) which feeds the machine container (40) and to the suction side of the pump (142). feeds the second screen (160). 5 Processing arrangement according to any of claims 1-11, characterized in that from the tile consistency regulating the water flow (F121), feedings are also supplied to the suction side (F123) of the pump (31) which feeds the machine container (40) and to the suction side ( F122) of the pump (142) which feeds the second bulkhead (160). 10 Dilution water container (140) at an inlet carriage for use in a process arrangement according to any of the preceding claims 1-13 comprising a substantially vertical cylindrical center part (140a), the lower part of which is connected to a bottom part (140b) and the upper part of which is a lid portion (140c), characterized in that the bottom portion (140b) and the lid portion (140c) are substantially semi-spherical and the dilution water container (140) further comprises: a substantially cylindrical, vertically cylindrical underpressure tube ( 140d), whose center shaft coincides with the middle part of the middle part (140a) and which vacuum pipe (140d) extends below the joint between the cover part (140c) and the middle part (140a) and an inlet pipe (140g) for exhaust dilution water in the lower portion of the vacuum tube (140d), and an annular overflow funnel (140f) in the upper portion of the middle portion 25 (140a). »« «