FI86446C - FOERFARANDE OCH ANORDNINGSARRANGEMANG VID BEHANDLING AV VIRAVATTEN. - Google Patents

Description

5 86446

Method and equipment arrangement in wire water treatment Förfarande och anordningsarrangemang vid behandling av viravatten

The invention relates to a method and an arrangement of devices for treating wire water.

The fiber and mineral slurry 10 fed from the headbox onto the wire or between the wires is dewatered through the wire. In this case, some of the fibers, especially the short fibers, as well as the majority of the filler material have to be taken with the water from the wire part through the wire chute to the wire well. That portion of the wire well wire water that is not used to dilute the streams of vortex cleaners or other short circuit equipment exits the wire well as an overflow stream and most commonly through a circulating water tank to the fiber recovery plant.

In prior art solutions, the wire water is not divided into different densities in the wire well.

From the wire well, the wire water is led together with the fresh pulp, the so-called centrifugal cleaners. 20 The purifiers are usually connected to the so-called a cascade circuit in which the fraction rejected by the purification stage is fed to the feed of the later stage and the accepted fraction either out of the plant or to the feed of the earlier stage.

From the point of view of the cleaning result, it is necessary that when the fibrous slurry is fed to a later stage, the consistency of the feed is lower than that of the feed of the previous stage. The consistency of the first stage is determined by the consistency of the headbox fiber slurry and has little effect. To reduce the consistency, water, most commonly wire water, is taken to dilute each stage. It is advantageous if the consistency of the dilution water fed to the subsequent stages is low. This is because as the consistency of the dilution water approaches the desired feed consistency, more dilution water must be used. If a lot of dilution water has to be used, it follows that the load on the stage increases. When the proportion of 2 86446 feed fibers in the discarded fraction in each stage is constant, the fiber load in the later stage also increases, and in the approved fraction the fiber load returns to the previous stage, which still needs to be further diluted, etc..

5

When the consistency of the dilution water to subsequent stages can be reduced, the effects and multiplier effects result in a reduction in the amount of fiber discarded by the plant. Similarly, plant flow rates decrease. With the arrangement according to the invention, with the same equipment and lower pumping costs, the same cleaning result is achieved, 10 as in the process according to the prior art.

According to the invention, a new method and device are formed in which wire wire is divided into fractions according to consistency in a wire well. According to the invention, dilute fractions from the first vortex cleaning step are used for dilutions of the subsequent vortex cleaning steps 15. Ko. the stairs decrease and the amount of fiber discarded by the plant decreases. According to the invention, the wire water is divided into fractions according to the consistency in the wire well and said fractions are utilized as feeds for the purification stages. In this way, the load on the overflow of the wire well and thus on the fiber recovery can be reduced, whereby the fiber recovery equipment is also reduced.

20

According to the invention, it is economical if the fibrous and mineral material which has passed through the wire passes as far as possible along the route of the wire well, the first vortex cleaning stage and the headbox. Thus, an attempt is made to avoid that the fibrous and mineral material does not enter other streams through dilutions and wire well overflow. In the method according to the present invention, the wire water is led to a wire well in a wire chute on which a plate or lamella clarifier is built. With the aid of the clarifier, the fiber and filler can already be enriched in the gutter towards the lower part of the gutter, and at the same time clarified wire water and bubble-like air can be taken to the upper part of the gutter, from where the overflow towards the fiber recovery takes place. Thus, the fiber recovery load is reduced.

In the method of the present invention, a clarifier is placed in a wire well which divides the wire water into a thicker fraction for the first vortex cleaning stage and a dilute fraction for the subsequent vortex cleaning stages. Further, the overflow can be taken from the top of the wire well on the side of the dilute fraction.

5

The upward movement of the air accumulated on the lower surface of the clarifier lamella plate and the downward movement of the fibrous and filler material deposited on the upper surface of the plate can be promoted by introducing mechanical energy either through the lamella plate or via wire water. A vibrator at different frequencies or an ultrasonic vibrator can be used to import energy.

10

The method according to the invention is mainly characterized in that the process divides the wire water before the treatment plant into wire mesh fractions of different densities in a wire well using clarifiers and that the clarifier fractions cleaning the stairs.

The device arrangement according to the invention is mainly characterized in that there is at least one clarifier adapted to divide the wire water into wire water of different densities in terms of solids content, the device arrangement comprising channels from the wire well to the wire well where the wire solids of different solids content to the purification stages and such that the fraction with higher solids content is fed to the first and / or first vortex purification stages and the fractions with lower solids content are fed to subsequent stages after the first purification stage to dilute the feed of said stages.

The invention will now be described with reference to an embodiment of the accompanying drawing, to which, however, the invention is not intended to be exclusively limited.

4 86446

Figure 1 schematically shows the method and apparatus according to the invention.

Figure 2 shows the structure of the clarifier. The representation is a section I-I of Fig. 1, where the white arrow represents the direction of solid enrichment and the black arrow the direction of air and clarified wire water flow.

Figure 1 shows a wire water treatment apparatus 10. In the treatment of wire water, the water accumulated in the basins A of the wire section is introduced into a wire well 11 on the side of the paper machine, usually on the operating side, through a wire chute 12. The wire chute 12 is preferably a rectangular flow channel in cross section 10. The flow only partially fills the duct and the aim is to keep the flow so slow that the bubbly air contained in the wire water can escape into the air space above. From the wire chute 12, wire water is led to a wire well 11, which is preferably a cylindrical high tank. The aim is to bring the wire water downwards towards the suction connections of the pumps at such a low speed that air bubbles IS can escape upstream. In practice, however, typically 1.0 to 4% by volume of bubble-like air remains in the water.

That part of the wire water which is not used for short-cycle dilutions leaves as an overflow flow V, from the upper end of the wire well 11 to the circulation water tank 13 and further to the fiber tal-20 collection system.

As shown in the figure, the wire chute 12 comprises a first clarifier 14a, preferably a lamellar clarifier, and as shown in the figure, the wire well 11 after the wire chute comprises a second clarifier 14b, preferably a lamellar clarifier. Thus, the wire water from the wire W 25 can be divided into different consistencies in terms of solids. The higher the solids content, the thicker the wire water.

As shown in the figure, the wire water in the first lamellar clarifier 14a is divided towards the bottom 12a of the gutter 12 into a thickening fraction, which is further divided by means of the clarifier 14a of the wire well 11 into sub-fractions of different consistency in the wire well 11.

^ 8 6 4 4 6

In the treatment plant, the cleaning process consists of several cleaning stages Pj-PN. An input is introduced to each stage and each stage processes the input so that both the accepted flow or verse and the rejected flow or verse are output from the stage. The rejected stream comprises more unwanted contaminant particles than the accepted more fibrous mass flow. Preferably, the Pj-PN vortex cleaning stages are used as the cleaning stage, in which the cleaner consists of vortex cleaners ρι »ρπ ··· ρΝ · The vortex cleaner is a conventional cleaning unit into which a flow is introduced from the side and as an outer spiral downwards and 10 the approved flow passes from the top out of the center of the device. In the vortex cleaning principle, impurities are separated based on centrifugal force as the heavier particles separate from the approved mass flow and the thus discarded fraction is taken from the center of the device at the narrow end of the purification cyclone PI »PII-PN. The vortex cleaner Pj; Pjj ___ is thus preferably formed from a cleaning cone, i.e. a cleaning cyclone.

15

With respect to the flow of the lamellar clarifier 14b of the wire well from the discharge side to the height of the wire well from its central region, a fraction is taken to the vortex cleaning stage Pn. Correspondingly, relative to the flow of the lamellar clarifier 14b of the wire well, the fraction from the outlet of the clarifier is also taken to the third vortex cleaning stage pm- The fraction is taken from a higher level relative to the point of intake of the previous 20 verse, where the solids content of the fraction is lower. The fraction with the thickest solids content at the bottom of the wire well with respect to the flow of the lamellar clarifier 14b is taken to the first vortex cleaning stage Pj.

25

From the outlet side of the lamella clarifier 14b of the wire well, a fraction is taken from the central area of the wire well 11 to the third Pni-Volume vortex cleaning stage Pni-PN. Thus, fractions with the desired consistency are obtained from the wire well 11. Thus, the flow rates of the cleaning process can be reduced and thus the pumping power is saved.

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In each vortex cleaning stage Pj ... PN, the fed fraction is processed so that from the narrow end of the purification cyclones of the vortex cleaning stage the so-called a heavier abandoned impurity concentration is taken from the project end and an approved concentration is taken from the wider end of the cyclone in the center of the device. The fraction approved from the first vortex cleaning stage Pj S is conveyed to the headbox K of the paper machine along the channel 15. The approved fraction carried along the duct 15 can be treated by means of a screening device and a deaeration device in the duct 15. The feed to the first vortex cleaning stage Pj is introduced along the channel 16 and the flow is provided by the pump device Ej. The feed of the first purification stage Pj is taken from the bottom of the wire well 11, where the consistency of the feed substantially corresponds to the consistency of the mass of the headbox K, taking into account the effect of the Pj stage and subsequent treatments.

The abandoned flow of the first vortex cleaning stage Pj is led out of the cyclone at the bottom of the vortex cleaning cyclone Pj and flows along the channel 17 into the channel 18. The channels are most preferably pipes. The channel 18 is led from the front of the clarifier 14b of the wire well 11 from the front and acts as an input channel to the second vortex cleaning stage Pjj. Pump E2 in channel 18 provides flow. The approved fraction of the second vortex cleaning stage Pjj is conveyed along the channel 19 to the wire well 11, its lower part and it is connected to the mass flow C1 introduced into the wire well 11.

20

The discarded fraction of the second vortex cleaning stage Pjj is conveyed along the channel 20 to the channel 21. The channel 21 is led to the flow side of the clarifier 14b of the wire well 11 from the discharge side. The channel 21 is further connected to the third vortex cleaning stage Pm so that an input Ρ {ΙΙ is introduced to said stage via the channel 21. Thus, the abandoned flow Pjj of the second vortex cleaning stage 25 is connected from the wire well along the channel 21. imported wire well fraction of the desired consistency. The flow is generated by the pump: ·; ·· * 3 *

The approved fraction of the vortex cleaning stage Pm is conveyed along the channel 22 to the channel 18. The approved fraction of the vortex cleaning stage Pm is thus connected to the feed of the second vortex cleaning stage Pn flowed along the channel 18. From the vortex cleaning stage 7 86446

The wood is passed to an approved fraction either to other vortex cleaning stages PN or said flow is passed to a wreck or other further treatment.

Figure 2 shows a section I-I of Figure 1. Shown is a lamellar clarifier 14a. The clarifier 14a is formed of adjacent plates dj, d2, d3 ... arranged slightly obliquely to the vertical plane, along the surface of which the solid in the wire water travels towards the lower edge of the lamella. Correspondingly, the clarified wire water released from the impurities travels upwards in the space between the lamellae. The spaces between the lamellae difd2; d2yd3; d3jdA ... allow the flow to be clarified without interference. Figures 1 and 2 show the upward arrows of the 10 clarified flows and the downward arrows of the thicker flow.

Claims (11)

A method for treating wire water, comprising removing 5 fibrous wire water from a fibrous and mineral slurry fed to a wire (W) from a paper machine headbox (K) through a wire (W), and passing the wire water through a wire chute (12) to a wire well (11) and ) directs at least a part of the wire water to a treatment plant (P, ... PN), preferably to successive treatment stages (P, ... PN), whereby at least a part is introduced into the treatment stage (Ρ |, Ρ ||, ΡΠ | ...) from the feed of the treatment stage from the wire well (11) and wherein in each treatment stage (Pj, ΡΠ, ΡΙΠ ...) the purified material 10 is divided into an approved fraction and an rejected fraction, characterized in that the method distributes the wire water before the treatment plant (Pj, Pn ... PN) in a wire well (11) to different concentrations of wire water fractions using clarifiers (14a, 14b) and that the method derives the wire water fractions obtained by the clarifiers to the usprocess (Pj.Pn.Pin ···)> that the thicker fractions are led to the first or first IS purification stages (Pj.Pjj ...) and the lower solids fractions are led to the purification stages after the first purification stages (PN, PN-l> PN-2 · ··) · Method according to Claim 1, characterized in that lamellar clarifiers (14b) are used in the method in the wire well (11). 20 Method according to Claim 1 or 2, characterized in that a clarifier (14a) is used in the method in the wire gutter (12) before the wire well (11). Method according to one of the preceding claims, characterized in that vortex cleaning cyclones (Pj, Pjj ...) are used as the cleaning device, in which the cleaning takes place on the basis of centrifugal force, the impure and heavier fraction being transferred to the cleaning stage (PN.j) ). : as feed as scrap away from the cyclone connection and with the approved fraction transferred either · ’: · to the headbox (K) or to the feed of previous vortex cleaning stages. : 30 9 86446 A method according to any one of the preceding claims, characterized in that a fraction is derived from the wire well (11) in front of the clarifier (14b) as a feed to the purification stage of the treatment plant and a lower solids fraction is taken from the discharge side of said clarifier (14b) for input to the subsequent purification stage. A device arrangement for wire water treatment, the device arrangement comprising a wire chute (12) into which the part of the fibrous and mineral slurry fed to the wire (W) from the headbox passes through the wire (W) and that the device arrangement comprises 10 downstream wire chutes (12) wire well (12), characterized in that there is at least one clarifier (14a, 14b) adapted to divide the wire water into wire water of different densities in terms of solids content, the device arrangement comprising channels from the wire shaft (11) at the wire shaft (11) where different densities occur, wherein a wire water with different solids content can be led from the wire well to the treatment plant after the wire well (11) to its treatment stages 15 (Pi, Pn ... PN) and so that the fraction with higher solids content is led to the first and / or first vortex cleaning stages (Pi, Pji) and lower solids fractions are derived later in the stages after the first cleaning stage (PN, PN_2, PN_3 ...) as input for the stages. 20 7. Arrangement of equipment for the treatment of wire water, characterized in that the cleaning apparatus comprises vortex cleaning stages (Pj, Pu), in which each vortex cleaning stage (Ρι, Ρπ, Ρπ. {...) comprises a vortex cleaning cyclone into which the feed is fed and from which a centrifugal rejected a fraction, wherein the discarded fraction comprises 25 undesired impurity particles heavier than the rest of the material and is fed to the refining stage (PN) or scrap or other further treatment after the refining stage (PN.j) and the accepted fibrous fraction is fed either directly to the paper machine headbox (s) as input to previous cleaning stages (Ρ, 'Ρπ—) · 30 10 86446 Device arrangement according to one of the preceding claims, characterized in that the clarifier is a lamellar clarifier (14a, 14b). 8 86446 Clarifier according to one of the preceding claims, characterized in that the clarifier (14b) is located in a wire well (11). Device arrangement according to one of the preceding claims, characterized in that the clarifier (14a) is located in the wire chute (12). Apparatus arrangement according to one of the preceding claims, characterized in that there is a duct (19, 22) through which the approved fraction of the scrubber is fed from the scrubber to the feed of the scrubber preceding the scrubber and a passage (17,20) through which the discarded fraction is passed to the scrubber. as input to the post-cleaning stage. 15 11 86446