FI116575B - Paper Machine Method and Arrangement - Google Patents

Description

116575

PAPER MACHINE PROCEDURE AND DEVICE PAPERIKONEESEEN LIITTYVÄ MENETELMÄ JA JÄRJESTELY

The present invention relates to a method of a paper machine for reducing the spread of added additives in the process during a continuous process in the pulp preparation of a paper machine, whereby a flowable pulp of free fibers and process liquid and a texture of at most 10% is directed towards the paper machine. headbox.

The present invention also relates to an arrangement in the pulp preparation of a paper machine for limiting the spread of additives in the further process, the process comprising an inlet for a flowable pulp having a consistency of not more than 10% and containing a fiber material and process liquid, a circuit comprising an inlet tray for the paper machine, and means for supplying said additive material.

In this patent application, a paper machine is defined as a machine for making paper in a continuous web.

Pulp preparation in this patent application refers to a process in which: starting from a fibrous pulp, usually a cellulose material, with a more or less solid consistency during: blending, a pulp prepares to be fed to the · ·· inlet carriage, whereby the pulp contains a maximum of 10% fiber. ***, material, usually at least 1, preferably 2 ... 7% and usually 3 ... 5%, as well as process liquid, usually water. Typical . this pulp preparation includes a so-called. pulps where fiber- Ί! '. materials from a cellulose process during decomposition and stirring are dissolved and mixed with process water.

tl · »· t

Traditional papermaking comprises a process in which a mass of substantially containing fibrous material and process fluid is passed through an inlet slurry to the drainage of a wire. The tili process involves a number of other vessels and devices including vessels where the consistency is typically 3 ... 5%, with much excess water being directed back upstream into the process.

In the manufacture of specialty paper such as decor paper, colored paper or other paper grades where valuable and possibly process-sensitive additive material such as titanium dioxide (T1O2), pigments or similar often very expensive constituents are added to the process, there is the problem that the retention of these constituents in the process is law, so that the backwater is typically can contain up to 1% of such ingredients or more. In order to recover these constituents, a traditional process involves recovery by, for example, flotation in recovery devices, after which the clear water from the flotation is re-used in the pulp preparation.

In the manufacture of such special paper, it is common for the above-mentioned additives to be added to the process already in the pulp preparation, so that a sufficient mixing and contact time with the pulp itself must be achieved. In practice, this means that essentially the whole process is in practice colored through. Thus, in the case of a quality change, the process must ...: initially achieve balance, which results in a long swing-in ·, ·, * time, while already a color change requires extensive system washing 'and results in large material losses. Already in itself, colored paper, including pigmented white paper, is difficult to manufacture, and especially in decor paper, the setting of the correct m 1 * color is difficult. In addition to this, the fact that under these circumstances a rupture in itself will cause instability.

For example, as a decor paper is impregnated upon further processing, its optical properties will also change.

::: The refractive index of the fibers and the impregnating agent is approximately equal and therefore such factors as the concentration, distribution and optical properties of the pigment are critical for; the quality of the product. Therefore, it is usually necessary to make test laminates before the actual production begins, and this takes about half an hour, during which time the pulp is cycled on the machine.

In itself, the process can in part be made more efficient with such arrangements which include, among other things, from the applicant's international patent applications No. PCT / FI93 / 00214, PCT / FI94 / 00578, PCT / FI96 / 00052 and PCT / FI01 / 00365, but some problems remain, although according to said arrangement, suitable backwater can be selected for each specific use. For example, in a typical traditional process, for example, about 20 ... 30 kg of the additive titanium dioxide (TiC 2) per 100 kg of paper will pass through the fiber recovery (see also Table I below). In a traditional fiber extraction plant working with flotation technology, the chemicals cause agglomeration, which reduces the optical effect of the pigments. Thus, the titanium dioxide loses in optical power, and some is lost, for example, in the form of deposits in the system. Of course, there are the disadvantages that are inherently caused by separate plants for fiber recovery, investment costs, operating costs and costs due to contamination and cleaning of the systems, and the complication of the process chemistry that the recovery according to the state of the art entails.

The purpose of the present invention is thus to avoid the disadvantages of hitherto associated with the use of pigments and especially in connection with the change of paper quality.

The present invention is based on the surprising. the realization that by raising the pulp consistency at an early stage of the process, it is possible to break what in traditional paper production has been called the long cycle, ie. a circuit where, in known arrangements, backwater can run from the paper machine's wire pit countercurrent in the system up to the point where the pulp is supplied, for example to; \ a pulper. By breaking this cycle, expensive additives, such as titanium dioxide and other pigments, are prevented from flowing up in the process and then partly wasted and partially soiled down the entire process chain.

The features of the invention are set forth in the respective drawings, respectively, of the appended independent claims, while the non-independent claims indicate advantageous embodiments. Thus, the process according to the present invention is characterized in that prior to the application of said additive, preferably in a separate process step, the pulp consistency is increased to over 10% by removing the process liquid, leading it upstream in the process, while in the process direction. downstream provides compensatory process fluid which in itself may conveniently be additive-containing.

Correspondingly, the device according to the invention is characterized in that separating means are arranged in the process direction before the means for supplying the additive material but after said inlet, these separating means being arranged to separate from the liquid pulp process liquid so that the pulp consistency increases to over 10%, advantageously in some cases up to 50%. The device further comprises means for conducting the separated process fluid upstream of the ... process and means for downstream introducing process fluid from said circuit to compensate the separated process - ::: the liquid. This latter process liquid can itself be more or less additive-containing.

.1 · 1st The invention is further described below with reference to some advantageous embodiments and the accompanying drawings, in which

Figure 1 is a schematic drawing of an arrangement according to an embodiment of the invention;

Figure 2 generally indicates a paper machine arrangement according to a particularly advantageous embodiment.

According to Figure 1, a paper machine typically comprises an input 1 for fibrous material, i.e. cellulose which is usually delivered in the form of dry sheets or in so-called. integrated use directly from a cellulose plant in the form of fibrous process fluid. If the incoming material is in sheet form, the process starts with the pulp preparation comprising a so-called. pumps 2 where the sheets are atomized and the material is mixed with process water, for example from a tank 3 to so-called. maid or pulp. The pulp undergoes various processing steps 4a, 4b, 4c, 4d, 4e ... which are essentially irrelevant in this context, in order to eventually be propagated via a winding inlet 5 of the paper machine on a wire 6. The wire runs through a machinery 7 where Large parts are extracted as so-called. backwater, while the moist ethereal mass of the pulp is formed by pressing 9 and drying into paper.

In addition to water, the backwater also contains certain chemicals that do not remain in the paper. These chemicals come with the process water, which in some parts is used in the so-called. the short cycle for dilution at the process stage where the chemicals in question are needed or where in any event they do little harm. Backwater used for other purposes is purified in various processes and purification steps to use one of the chemicals and on the other to achieve a::: pure water that can be used on other hali in the process. Each, '·; however, in some men, the purification process is incomplete and. ·. also requires both energy, time and equipment.

'II! Especially for specialty paper such as, for example, decorative paper and other colored paper, the production volumes are relatively small. For this reason, production of such qualities is only profitable in ··: integrated paper mills, and where special-grade paper is usually run in paper mills that receive the fiber material. in substantially dry form, which leads to a need for I process liquid at the beginning of the process. In known processes *, this process fluid is usually taken in the form of said long cycle from the purified backwater. Also this purified process-'Λ; However, liquid contains in practice a greater or lesser proportion of pollutants, ie. mainly material belonging to another part of the process. For colored paper, some of these pollutants comprise, among other things, pigments such as titanium dioxide, which, in order to obtain a good admixture, are usually added already in the pulper 1, the system being in practice fully colored. This, in combination with these tend to be expensive components in themselves during the process of depositing themselves as deposits in the various parts of the system, for example, in the case of colored paper, leads to the fact that when changing e.g. tili another color must clean the entire system before the next quality can be run.

The system according to the invention differs markedly from the prior art described above. By momentarily increasing the consistency of the pulp by introducing separator means at at least one point in the process such that an extra separation 8, 8a of the process liquids is achieved, the long flows of valuable additives contaminated process liquid are interrupted in the system. In the past, separation has only been applied to prevent chemicals that interfere with the underlying processes from flowing downstream, while the idea that in a similar way would also prevent valuable additives from contaminating upstream is entirely new.

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: V: The principle behind the invention is derived from the following Table I, where; the material balance in different parts of the system is illustrated by, I. using the consistency of the pulp (%), volume ("X" = liter of liquid per * * * », **, kilogram of mass) and dry matter (kg) on one side for a typical process according to the prior art (T) and on the other, the side of a process according to an embodiment of the present invention (U), wherein A indicates the values of the mass> »'··· * during the initial stages of the process 1 ... 4a according to the prior art: Αχ indicates values for the pulp after separation 8 «*» according to the invention, B indicates the situation at the inlet carriage 5, C, ·, indicates the position after the paper has left the presses 9, D indicates

I I I

*; * * | "excess water", ie. water that must be cleansed before it can '>'! Ether is used, and E indicates the situation in the short cycle: 116575 7

Item Consistency Volume of dry matter% X kg

T U T U T U

A 4.0 25.0 100 A1 30 3.3 100 B 2.0 2.0 100.0 100 100 100 C 45 45 2.2 2.2 100 100 D 1.0 0.5 22.8 1, 1 22.8 0.6 E 2 100 200

Table I

From the above table I suggest that about 20 ... 30 kg of T1O2 per 100 kg of paper passes, among other things. a fiber recovery 10, while the volume of TiO 2 -containing excess water and its proportion of dry matter are radically reduced as the pulp texture is momentarily raised in accordance with the invention.

In practice, the separation of process fluid takes advantage with the help of such thickening technique as is known per se in, for example, cellulose production, bleaching and decolorization.

Such arrangements are usually capable of increasing the consistency of the fiber-containing pulp from an input value of 2 ... 10%, in the present case typically of the order of about 4 ... 6%, to a final value of up to 50% and possibly even

Hl I

higher.

According to an advantageous embodiment, the separation takes place in form '!!! of a pressing which advantageously occurs before a grinding 4c.

* 1 'The pressing at the thickening is then preferably carried out in a screw or belt press 8a of a type known per se, such that the dissolved -:> tt: dissolved mass after pressing receives a dry content of over, ·) ·, 10% , especially in the range of 20 ... 50%, preferably 25 ... 40%,! advantageously at least 30%.

116575 8

The process liquid separated by pressing 11 is directed back upstream in the process, preferably back to the pulper 2. The separated liquid 13 is preferably replaced in a disperser 12 by substantially the same amount of liquid from the paper machine circuit. Advantageously, this is done in a device according to the applicant's international patent application No. PCT / FI99 / 00143, or alternatively with a screw device or stirrer of another type. To obtain an optimal admixture, the disperser 12 is advantageously arranged in the process direction substantially immediately after the separation 8, 8a.

According to an advantageous embodiment of the invention, the main supply 14 of critical additives such as very expensive pigments and dyes in connection with the liquid supply to the disperser 12 (see Figure 2), which for the part of the additives, provides an effective mixing at an early stage. as possible after the concentration. Figure 2 indicates that additives can also be added 14a, 14b at later stages of the process. Since a supply of at least some additive advantageously takes place simultaneously with the supply 13 of, substituting liquid, it does not mean that the substitute • <* ·; ·; the liquid is removed from such a part of the process where the residual content of additives can be high and high.

• »· · ,,, · The above-mentioned arrangement where the consistency of the pulp is increased / y in practice leads to the removal of and returning such process fluid that functionally belongs in an earlier process step in a way that" prepares space "for an additive of such additive whose spreading upstream one wishes to prevent. This allows the latter material to be added, and thus e.g. the colored part of the process is restricted to being poured within the short cycle of the paper machine, while the long cycle, in the case of such a person as may be needed, is freely poured from valuable and / or polluting \ material.

9 116575

In the particularly advantageous embodiment of FIG. 2, the system is substantially self-purifying, whereby there is in practice good available on the backwater of various fractions, also available on relatively clean excess liquid to the extent needed in other parts of the system. Thus, for such needs, a fairly clear fraction can be chosen which further reduces the losses of valuable additive material. The small amount of excess water still available can be treated in fine filters to provide splash water, etc. , the filter cake being returned to the disperser.

In Figure 2, a particularly advantageous arrangement is indicated in which the amount of water withdrawn from the system is diverted to a point in the drainage where the concentration of material is as small as possible. According to this embodiment, this concentration can be reduced by providing a suction cup 15 at a point where a fiber web has already been formed, whereby the fiber web acts as a filter. This suction cup 15 is operated with a low vacuum, whereby a gentle filtration and a very pure backwater are obtained. This filtration reduces the amount of. material so that this backwater can normally be guided 16 to one; overflow 17 without any further recovery needed.

• · · * * «# i ·

Thus, by the arrangement according to the invention, it is possible to achieve an almost 100% retention of the valuable t (1) * additives while at the same time eliminating the need for special recovery devices, reducing the idle speed during the test. lamination and shortens the turn-in time after color change.

In the above, some advantageous embodiments of the invention have been described, for the expert it is clear that the invention can also be applied in many other ways within the scope of the following claims.

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Claims (10)

A method for preventing the spreading of an added additive in a continuous pulping process of a papermaking machine, wherein the fluid and pulp containing fibers and process fluid having a consistency of up to 10% are led towards the papermaking headbox (5), characterized in that consistency of more than 10% by removing (8, 8a) the process fluid and passing (11) it upstream, while (13) replacing the process fluid is added downstream. Method according to Claim 1, characterized in that the consistency of the pulp is raised so that the pulp corresponds to a dry content of 20 to 50%, suitably to 25 to 40%, preferably at least 30%, by suitable separation by pressing (8, 8a). from the pulp, the process fluid which is recycled (11) upstream in the process. 3. A method according to claim 1 or 2, characterized in that before the pulp is fed forward to the headbox (5), a process (t) liquid for the pulp is added to the pulp in a short cycle additive-containing process. in liquid form. Method according to one of Claims 1 to 3, characterized in that, in the dispersion (12) of the pulp of higher consistency, the additive (14) and (13) are suitably mentioned as a replacement process fluid. The process according to any one of claims 1 to 4, characterized in that the additive comprises pigment or other dyes. •> Arrangement for papermaking pulp preparation to prevent the additive from spreading upstream in the downstream process, the process comprising feeding (1,2) a pulp containing fluid material and 116575 14 process liquids with a consistency of up to 10%, comprising a papermaking wire (12) and means (14) for supplying said additive, characterized in that it has separating means (8, 8a) arranged in the process direction before the means (14) for supplying the additive but after said feeding (1, 2), separating means (8) , 8a) is arranged to separate the process fluid from the fluid so that the consistency of the pulp increases to more than 10%, means (11) for passing the separated process fluid upstream and means (13) for feeding downstream process fluid from said circuit to compensate the separated process fluid. Arrangement according to Claim 6, characterized in that said separating means (8, 8a) are suitably pressurized to raise the consistency of the fibrous mass from an input value of 2 to 10%, typically of the order of 4 to 6%, to a final value of 20 to 50%, suitably to 25 to 40%, preferably to at least 30%. * - «« Arrangement according to Claim 6 or 7, characterized in that the means (13) are arranged in accordance with the said arrangement; at or after the additive feed (14) to supply the process fluid from the short run of the papermaking machine. Arrangement according to one of Claims 6 to 8, characterized in that the dispersing means (12) are::: suitably arranged in connection with the supply (13) of said replacement process liquid to redisperse the pulp from which the excess liquid has been removed, said additive the feeding means (14) are preferably arranged in conjunction with these '··· ’dispersing means (12), suitably such that: · said dispersing means (12) are arranged in the process direction substantially immediately in the said separating means (8, 8a). after. 116575 15 Arrangement according to one of Claims 6 to 9, characterized in that a separate low vacuum suction box (15) is arranged on a portion of the wire (6) which has already formed a fibrous web, and means (16) are provided for this for conducting water from the suction box (15) in the system high upwards towards the overflow (17). t * »♦ ·>