FI112390B - A system and method for collecting dilution water from a paper / board machine connection to a paper / board machine headbox - Google Patents

Description

112390 Waste system and method for collecting dilution water from a paper / board machine connection to a paper / board machine headbox To collect the dilution water from the paper / board machine to direct it to the Z-board headbox.

Water is an essential raw material for paper making. Paper and board grades are made in a paper machine by dewatering the water / wood fiber blend from a pulp mill and by continuously moving webs in various parts of the paper machine, such as wire, press and dryer sections. During dewatering, water-permeable tissues become contaminated with materials coming from the paper web and various process waters. To work well, fabrics and paper machine elements such as rollers, scrapers, forming strips, suction boxes, etc., must be continuously washed with a water jet and the washing water removed. The • i · V · 20 washing water of the fabrics gets dirty, but the washing water can still be used as circulation water for the paper machine.

'. · .; In addition, water is also used elsewhere in the papermaking machine for washing, sealing, lubrication, removal of interfering substances and transfer of thermal energy. In current paper mills * ·; . · A large amount of fresh water is needed for cooling and for the above washing needs in the wire section: and in the press section and for dilution in the pulp mill. After the wire and the compression 25, these waters are discharged mainly into fibrous circulation water. Excess circulating water goes to waste water. The net amount of fresh water required for paper machine wash jets is i i · * * 2 about 10 m / t of paper product produced. As a result, the paper mill •> generates a large amount of warm waste water, which must be purified, for example, biologically and, if necessary, further cooled before cleaning. Paper machine wash jets are collected through various * * «• # '·; · * 30 troughs and troughs and led to a circulating water system. In addition to fresh water, paper machine circulation water is used as jet water for wire and cleaning parts. Circulating water is • generally cleaned with filters fitted with a 150 μηι: η sieve, which however allows fine particles and dissolved material to pass through. These impurities 2 112390 cause clogging of jet nozzles and other structures and contamination of equipment with interfering substances in the paper machine water system, resulting in negative effects on paper quality and production. As a result, the most demanding washing of paper machine fabrics and parts involves the use of chemically purified fresh water. Fresh-5 water is cold, so it needs to be substantially heated from about 7 ° C to about 50 ° C to reach the operating temperature required for paper making. In addition, humic substances and color must be removed in accordance with the chemically defined quality standards, which will increase the processing costs. Due to the constant supply of fresh fresh water to the process, the costs of fresh water and wastewater will increase by 10. In addition, the waste water discharged from the plants adversely affects the environment.

Finnish Patent Application No. 941619 discloses a process system in which the filtrate separated from the recirculating water fiber is used as a diluting fraction which is led to a mass flow of an average concentration at various widths of the papermaking machine.

Finnish Patent Application No. 971126 (filed March 18, 1997, unpublished) discloses a dilution water system in which a tap water stream drawn from a wire well is conducted. water purification equipment for separating fibers, fillers and additives from tap water and / or. ', * 20 and thereby provide an enhanced dilution water flow which is fed to the headbox dilution profiling system for dilution water. In this dilution system; *. explicitly applies the separation method, which separates solids from the dilution water. *; . with water purification equipment.

i «· V. 25 Finnish Patent Application No. 962176 (filed May 23, 1996, non-public) discloses a processor for the selective collection of jet waters, where the waters are selectively collected, v. • »*, * *, washing waters, and water removed from the papermaking web being manufactured, are recovered, at least some of the collected water is recycled and recycled

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30 recycling potential in the papermaking process. New combinations of separation technologies, such as flotation, membrane technology, ultrafiltration, nanofiltration or reverse osmosis, and evaporation, are used for water purification.

Finnish Patent Application No. 962177 (filed May 23, 1996, unpublished) discloses one solution for reducing paper mill fresh water consumption, which replaces some of the fresh water brought to the paper mill with locally purified water, such as water that is purified or purified. Combinations of separation techniques are used for purification. The solids concentrate recovered from the purification steps is, where applicable, utilized by tracking it to flow upstream of the feedstock for reuse at the paper mill.

European Patent Application No. 0 733 735 discloses a wet end of a papermaking machine in which water recovered from the wire section is recycled to a dilution headbox.

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In many prior art solutions, high-pressure wire washer and wire guide roller washings are generally directed to the nose type and further to the wreckage system, whereby the need for storing wreckage water and solids precipitation from the wreckage is increased. 100 g / m of water can be removed from the wire, which means for example! 20 at 25 m / s 2.5 1 / s / m / wire. In addition, water from the wire guide rollers is estimated to be about 2-3 l / s / m. Most solutions use a variety of complex and expensive water purification equipment for interfering substances such as solids and dissolved chemical compounds. elimination. In addition, the selective recovery of wreck waters requires the tracking of complex ice systems for the recycling of each aqueous fraction. When dilution assay-: *. '. Untreated tap water is introduced into the mesh, and the consistency of the dilution headbox mass: "'; varies, resulting in retention changes and system oscillations. In addition, in many, * L (cases, recyclable wastewater must be deaerated using separate equipment.

f · • », 30 Nowadays the so-called. dilution headboxes in which the dilution water is led to the mass flow from the headbox mass distribution supports. The dilution water is introduced into the mass flow 4 112390 at desired points through the headbox width through the valves, whereby the valves allow the dilution water flow to be adjusted. The dilution water provides a desirably controlled basis weight of the web over the web width. For dilution headbox design, reference is made to Applicant FI Patent Application No. 901593.

It is an object of the present invention to provide a method for better utilization of pure tap water fractions, particularly at the wet end of a paper machine, to achieve as closed a water circulation as possible, and a system for collecting dilution water from a paper / board machine.

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In order to minimize dilution water as the solids water, which is advantageous in the basis weight control of the web, the application discloses a structure in which the dilution water is collected at preferred locations on the paper machine / board machine. Preferred locations are those water collection points where the water solids content is as low as possible. In the system of the present invention, the headbox dilution water circulation is formed as a separate circulation circuit where the dilution water is collected from these collection points where it is the cleanest and as low in solids as possible.

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The above-mentioned drawbacks of the prior art can be overcome and the above-defined objects 20 are achieved by the process of the invention for the utilization of pure tap water fractions and a system for collecting dilution water from a paper / board machine characterized by: defined in the character portion of the claims.

A major advantage of the present invention is that at the same time the water from the scrubbers is routed to a dilution headbox instead of a rejection system, without separate purification or selection operations. In addition, the amount of waste water discharging to the environment can be significantly reduced. By not using extra water heating, cooling, and purification measures, there is clear economic savings. In the following, the invention 30 will be further explained by preferred embodiments, which are not to be construed as limiting the invention.

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Photo List:

Figure IA. Prior Art Dilution Cycle 5 Figure IB. The headbox

Figure 2. Dilution cycle system according to the invention

Figure 3. Water intakes of the method according to the invention 10

Figure 4. Effect of dilution water on profiling ability

Figure IA shows a prior art solution for water recovery. As shown in the figure, from the former F forming wire Eh retention, the tap water is led back through channel 29 to a container structure S, which also introduces fresh mass m. ,,, to the water distribution manifold J2.

* 9 * * 9. * 20 Figure IB shows in principle headbox 1. Headbox 1 is a so-called headbox. a dilution headbox and comprises a mass distribution support Ji, followed by a bellows 110, a bellows chamber 111, a bellows chamber turbulence generator 113 and a turbulence generator.

after the generator 113, the lip cone 114 from which the pulp suspension is derived from the former F

• «» between the forming wires Hi and H2. The diluent is preferably diluted with water: v. The circulating water system 150 according to the invention is thus connected to the headbox 1 so that the collecting channel 50b of the ice system 150, after the collecting vessel 60, is connected to a dilution water manifold J2. Dilution Water Distributor J2 Water can be distributed through branch channels! i), ···, Di, D2 ... further through the bellows 110 to the various tube rows at desired points in the headbox, to adjust the basis weight of the paper / board web to the desired weight. Valves Vi, V2 ...

30 regulate this dilution water flow.

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Figure 2 shows a paper machine / board machine 100. The paper machine / board machine 100 comprises a headbox 1, followed by former F, formerly press section P and press section P drying section K. As shown, the former F is a dieformer comprising forming wires H1 and H2 with from headbox 10 is led.

The pulp web W is heavily dewatered and the pulp web W is further conveyed through separate dewatering elements such as suction boxes 11a1a, 11a2 ... and suction rolls 12ai and forward with the forming wire H1 so that the pulp web W passes over the forming fabric Ht and .. and with the help of and through the suction roll 12ai water W is removed from the pulp web. The web W is further conveyed to the press section P by the pick-up roll 13. The web W is conveyed between the transfer blankets H3 and H4 to the first press Pi and then between the transfer blankets H5 and H6 to the second press Pi and forward. The web W is picked up on the dryer section K by means of a pick-up roll 14 and transferred in a first drying cylinder group Rf of the dryer section K by looping with the wire H7 through the drying cylinders 15ai, 15a2 ... 15 and rolls, preferably swivel rolls 16ai, 16a2 ... further to the second drying cylinder group of the drying section K. In the group, the web W is conveyed forward in a loop-like manner, kneeling with the wire. In this way, the web is conveyed by a drying section from one drying group to another by drying cylinders, and preferably also by wrapping. through holding units or the like.

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According to the invention, the headbox 1 is so-called. Dilution. Dilution water,; · with a concentration different from that of the pulp suspension J2, 1 1 ·, ·:. as desired via valves V1 and / or V2 and / or V3 ... to different widths of the headbox.

This allows you to adjust the paper / board web produced by the paper machine / board machine; 25 basis weight per web width.

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.v, In the embodiment shown in Fig. 2, water is removed from the pulp web from former F

* f, ···, through the suction boxes llai, lla2 ... and the suction roll 12ai, and the water is recycled, so that water from said dewatering elements is passed through channels 30ai, 30a2 and 30a3

30 to the manifold 50, and further to the manifold, preferably to the container 60 and further to the headbox 1 of the papermaking machine, distributing its diluent to log J2. Formerist F

7 112390 discharges solids containing tap water to the normal headbox mass rotation 200 and further to headbox mass manifold Ji. Solid water is passed through a channel 29 to a container S, to which a fresh mass m is also conveyed. From the container S is a channel 18 to a head box 1 pulp jet J 1. Thus, the dilution fluid circulation system 150 and the 5 mass circulation system 200 are separate units. Rotations 150 and 200 are essentially different systems. Thus, those portions of the paper machine / board machine dewatering structures where the low water solids content is low, such that said low water solids content fractions are transferred directly from the different paper machine / board machine collection points to the The dilution water recirculation system 150 is thus separate from the head box mass distribution log Ji mass recirculation system 200.

As shown in Fig. 2, water is further removed from the web in the press section P from the press nip N2 of the press Pn 15, and this water is led along the channel 30as to the collecting duct 50. Similarly, the transfer felt H0 conducted through the press nip N2 is dehydrated the condensation water from the dryer section K inside its drying cylinder 15a2 is utilized and fed through the conduit 30a7 to the collecting duct 50 and further to the dilution water manifold J2 of the paper machine headbox 10; * 20. Correspondingly, the inside of the dryer section hood 80 is removed '; condensate water and is channeled through channel 3Oas to manifold channel 50 and further. * for dilution water manifold J2. Pumping devices P10 and P20 in channels 50 and 50b provide a flow of water to tank 60 and from tank 60 to the diluent dispensing support J2.

Thus, as shown in Fig. 3, the water 2 of the wire washing and cleaning equipment with a solids content of about 0.1% and the water of the wire guide rolls 3, whose solids content does not change under process conditions, are directed to the dilution box 1. , such as for example retention, as well as water removed by suction boxes 4 and water 5 removed by suction rolls, which is generally about 3% of the headbox flow rate, which corresponds to about 6 '30 1 / s / m with the headbox flow 200 200 / s / m. The solids content of these waters is invariably less than 0.1% Further, the waters of the felt washing and cleaning apparatus 6, the water removed from the press nip 7 of the press section 8, the condensate water 8 discharged from the drying unit and the condensate water 9 removed from the hood. with a solids content of 0.1%, about 13-14 l / s / m, and if the dilution requirement is 10% (20 l / s / m), no more than 6-7 5 1 / s / m of supplied tap water is required. Since the dilution water contains water which contains dissolved chemical compounds and additionally only water containing the fines removed under high vacuum, the retention effect of the dilution headbox 1 is not nearly as great as in the prior art solution. The solids content of pure water is not influenced by the basis weight retention or other factor that affects normal tap water consistency. 10 Cleaner dilution water also speeds up the dilution headbox in adjusting the basis weight. The water to be recovered has a solids content of <5 g / l.

In the solution according to the invention, the water from the process is diluted for use at a solids content of 5 g / l or less. These so-called clean waters include: 15 press waters, felts and roller wash waters, leveling box waters, and wire-wash waters. Generally speaking, airless pure water can always be recycled as dilution water. There is no need for separate dry cleaners and cleaning equipment, air removal and strainers. The aim is therefore to recycle dilution water which: 'The interfering solids content is as low as possible. This is reduced; f 20 the need for dilution water treatment. However, e.g.

,; in case of disturbances, fresh water in the dilution water system. Cleaner dilution water I, 'accelerates dilution headbox 1 control over basis weight and reduces the need for dilution * * ·, further reduces valve contamination, etc. This is also illustrated in the graph of Figure 4, which shows the required dilution water at 25% (%) ratio using pure water fi. · ". (graph), retention 80% Ϊ2 (graph), retention 60% f3 (graph), and retention 40% f4 • · », ·, (graph). Here, 80% retention means that 80% of the solid continues on the wire and * * t> i »!! I passes through the wire. Correspondingly, a retention of 60% means that 60% of the solid continues through the wire and 40% passes through a wire and, accordingly, a retention of 40% '30 means that 40% of the solid continues through the wire and 60% goes through the wire. That is, the direct fi, f2, f3 and f4 shown in Fig. 4 show cases where the solids content of the dilution water 9112390 increases from fi to f4. Thus, for example, in the case of f4, the water used in the dilution has the highest solids content. This clearly shows that the more diluted water is, the more diluted the water required. By solid is meant a solid material such as fibers and fillers.

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Claims (9)

10, 112390 A system for collecting diluent water from a paper machine / board machine, characterized in that the system provides diluent water to the headbox (1) from a paper machine / board machine (100) having a solids water content of less than or equal to 5 g / l. 1) in connection with the headbox mass flow at the desired points at the headbox width through the valves (Vj and / or V2 and / or Vg ...), whereby the valves (Vj and / or V2 and / or V3 ···) control the dilution water flow and hence the paper and / or a board outlet having a drainage channel (30aq, 30a2-..) through which the drainage water is further collected and transported by the collecting channel (50). through the hopper (60) and further to the diluent of the paper machine / board machine headbox and that the dilution water system (150) forms a separate conduit system (150) separate from the pulp and / or fibrous water recirculation system (200) associated with the pulp distributor (Jj). A system according to the preceding claim, characterized in that: V: 20 dilution water is collected through separate channels (30a ^, 30a2 * ..) from the wire section of the paper machine / board machine. A system according to the preceding claim, characterized in that: the dilution water is collected from the wire section of the paper machine / board machine and that the water is collected from the forming wire (H2) and / or the suction box (IIa ^ llag ...) and / or the suction roll. System according to claim 1, characterized in that the dilution water: is collected from the press section (P). 30 π 112390 A system according to the preceding claim, characterized in that the dilution water is collected from the connection of the press nip (N 2) of the press (Pi) and / or of the transfer felt (H2) carried through the press nip (N 2) of the press (Pi). System according to claim 1, characterized in that the dilution water is collected from the drying section (K). System according to the preceding claim, characterized in that the dilution water is collected from the condensation water inside the drying cylinder (16a ^, 16a2 · ..) of the drying section (K). A system according to any one of the preceding claims, characterized in that the dilution water is formed from condensed water discharged inside the hood of the drying section (K). 15 9. A method for recovering waste water from a paperboard board machine, characterized in that the water from the wire scrubbers and / or the water from the return rollers and / or the water from the suction rolls and / or the water removed by the suction roller is controlled by the through the collecting tank (60) and further to the dilution headbox (1) v. · 20 for recycling to the dilution headstock (1) for dilution water and that the water thus collected has a solids content of less than or equal to 5 g / l. • · • t> t · * I {· »• · 1 f • · I» '«* *» »» * I • »» I 12 112390