DE1621681A1 - Plant and process for bleaching cellulose material - Google Patents

Description

DH. IiVG. ERNST "" - - ■ »» τ

8 MfNCEENSS-, £ j> ^

VA

A 12ο 67 ■ ', ■ 11 »April 1967

AKTiEBOLAGET ΚΑΜΏΙ * Karlstad / Sweden

Plant and process for bleaching geluline material »

The invention relates to an installation - for bleaching * of cellulose material with a vertical cylindrical; container, which is provided with a device for the continuous axial throughfeed of pulp and also with a sieve device which is arranged inside the container and is provided with a set ₅ is formed by konzentfisclißn '..- hollow sieve bodies, which are arranged at the same height and each have cylindrical sieve surfaces and an inner cavity for sieving and discharging part of the liquid content of the pulp, which

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Sparlas ·· Sdirarabere Bankhau · Mnrdc, fin * i Ca., M £ n * en, No. 254 «BonUlflU» H. Aulhäuwr, Mündi «; No 53597 Poilithedi. Münthan I5386I-, ^ Js

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Container also. Movable spray tubes for the supply and the distribution of liquid in the pulp. sits », the container with the sieve device and the spray pipes may be substantially different from that in the USAr patent -3. o78.7o3 described type. be.

Task of. Invention is the sieve and. Spray devices

several of the different

To make processes suitable for bleaching the pulp. porridge are required to thereby increase the number of components to decrease the bleaching plant.

According to the invention; this goal is essentially d.a4 ^urca . ^he ~, rei.cht,: _ 4ass-. the sieve bodies are divided into lobe zones with separate outlets, are u.ndy-daÄ the spray pipes ,, the. with lines for the supply of different fluids, which have their openings in different heights. By this arrangement, - by welcne. two different. Liquids in. dem-Be.il · äl · ter ^ granted- and furthermore two separate, dissected clauses; and, if this can be carried out, is that. _; Container :: for- _: a double exchange of liquids., Ger,., In which the liquid which is supplied to displace at least part of the original liquid content of the pulp is in turn at least partially; by a second supplied 'liquid y

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and is collected separately, i.e. without mixing with the first displaced liquid. That way you can the reaction products that "result from a bleaching reaction, for example arise in the container, -possibly together with not spent treatment chemicals, by a washing liquid be displaced, for example more or less pure Water, and the: ■ -. Washing liquid can "immediately" on it to be displaced by a liquid, which is used to carry out contains chemical bleaching agents required in a subsequent bleaching process.

The invention is further directed to a method for bleaching pulp slurry _% which can be carried out in the above besenrie enclosed plant and consists in that alkali is supplied through spray pipes, the openings of which are located at a medium height, while washing liquid is supplied through spray pipes , the openings of which are located at a lower as well as a higher height, so that an alkali treatment stage is carried out at the height of the sieve body in a container, which is also used to carry out a preceding calibration stage, e.g. with chlorine or chlorodioxide.

The invention in conjunction with the drawings forming beilie f is described in detail and Swer tilt: _t

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Fig. 1 is a vertical section view of the upper part a bleaching tower according to the invention and

2 shows, in a schematic representation, a part of the same on an enlarged scale, as well as the various liquid flows in this when carrying out the aforementioned alkali treatment stage.

The bleaching tower shown in Fig. 1 forms part of a plant for bleaching pulp, which consists of a number of towers connected in series, through which the pulp is continuously conveyed and in which a series of, different treatment stages is carried out, which are used to bleach the Pulp are required. The tower shown can therefore be preceded and / or followed by a tower or several towers of essentially similar design.

With the help of a pump, pulp is made continuously fed to the lower end of the tower, not shown, and distributed in this over the cross-sectional area of the tower (e.g., with the aid of a distribution device of the type shown in U.S. Patent 2,764.oll, so that the pulp, as indicated by arrows 11 in Fig. 1, extending axially through the tower at all locations with essentially the same Speed moved up. On its upper linden tree

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the cylindrical jacket 13 of the tower has an enlarged Part 15 with an outlet 17, in which the top layer of the cellulose pulp column rising slowly in the tower a discharge device is deflected, which consist of shovel blades 19 which are attached to arms 21, which extend radially from a shaft 23 which is concentric to the tower jacket and is driven by a motor 22.

The sieve device arranged in the tower is composed of sieve bodies 25, 27, 28, which are connected to one another and to the tower jacket 13 are concentric. The screen body 25 has an inner screen surface and an outer screen surface in the form of a perforated one or slotted cylindrical plate 29 or 31 and an inner cavity, the same applies to the screen body ' 27, while the middle screen body 28 has a single cylindrical screen plate. The strainer bodies are in the same Arranged height and have the same axial extent and are also mutually connected and by horizontal and mounted radially directed support arms 33, the cross sections of which are preferably with reference to the axial flow of the pulp are streamlined. These arms extend outwardly through the jacket 13 and at the outer end of each of the same a hydraulic actuator 35 is attached. The set of sieve bodies described is in the tower somewhat displaceable in the axial direction, so that it

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-Sam rising pulp a short distance after accompanied above, and through the actuators 35, the screen bodies become periodic and comparatively rapidly returned downwards so that a relative movement takes place between their sieve surfaces and the pulp.

According to the invention, the screen bodies 25, 27, 28 are in Ilöhenzonen divided with separate outlets. For example, the interior of the screen body 28 is surrounded by horizontal partitions 37, 39 divided into three cavities 41, 43, 45, each with a separate channel 47, 49 and 51 in the support arms 33 are connected. These channels are in turn outside of the tower jacket with three separate outer outlet lines 53, 55 and 57 are connected. The inner screen body 25 and 27 is divided in a similar way and their cavities 59, 6o, 63 and 6o, 62, 64, which are in the same Are height and have the same axial extent as the cavities 41, 43 and 45, are also with the channels 47, 49, 51 and connected to the outlet lines 53, 55, 57. The pulp slurry through the sieve body to the various Liquid fractions screened off from high altitude zones are therefore kept separate from each other and are removed from the tower carried out for itself.

For changing all or part of the pulp from the pulp through the sieve body is sieved liquid

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a device is provided for the supply of the replacement liquid and its distribution within the pulp pulp. According to the invention, this device is divided into two separate systems and two dissimilar liquids can be distributed in the tower at different heights. One system has a fixed supply line 65 with a control valve 67, a tank 69 attached to the shaft 23, distribution pipes 71 and vertical spray pipes 75, 77, 79 with outlet openings 81, 83, 85. With the aid of adjustable slides 86, the amount of liquid supplied to the tank 69 is distributed in correct proportions to three compartments 88 located outside the tank 69 and therefore to the three outlet openings mentioned. The other liquid supply system comprises a fixed supply line 87 with a control valve 89, a circumferential tank 91, three distribution compartments 93, distribution pipes 95 and vertical spray pipes 99, lol, Io3, which have upper outlet openings Io5, Ia7, Io9 and lower outlet openings 111, 113, 115 are provided. The outlet ports are elongated in the vertical direction so that when the shaft 23 is driven to rotate, each outlet port distributes liquid over a cylindrical surface. The openings 81, 83, 85 have the same vertical extension and are arranged at the same height. The same applies to the openings belonging to group Io5, Io7, Io9 and group 111, 113, 115.

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division system, moves in a path which is the same radius as the path of the spray lance 99 belonging to the other liquid distribution system, however the outlet port 81 of the former is related to the openings Io5 and 111 of the last-mentioned spray tube axially offset. Thus, liquid of the type supplied through conduit 65 becomes over a cylindrical surface distributed, which has the same radius as, but a different position in the height direction than the cylindrical surfaces has over which liquid from the line 87 is distributed. The same applies to the relative position of the opening 83, Io7, 113 and for the relative position of the outlet openings 85, Io9, 115. Hence the whole liquid distribution device distributes two liquids over different height zones and in each zone the liquid is directed to outlet openings distributed, which move between the screen bodies 25, 27, 28 or only on one side of the same. Furthermore, the Arrangement of the outlet openings in the height area of the screen body to ensure that the displacement liquid flow through the Pulp directed transversely to the axial flow of the pulp is, i.e. essentially horizontal and radial. The three heights of the outlet openings can be approximately correspond to three heights of the dividing walls of the sieve body, however, a certain opposite offset in the axial direction

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often preferred in all directions. For example, can the openings 81, 83, 85 opposite the lower part of the central cavities 43, 61, 62 of the sieve body or even partially be arranged lower than this.

The system described is suitable, among other things, for carrying out a cellulose bleaching process in two stages, namely in a first stage, which consists in the treatment of the pulp with chlorine or chlorine dioxide and in lower part of the tower is carried out, and in a second stage involved in the treatment of the pulp with alkali, which is carried out in the upper end of the tower and in the height of the sieve body. In this Trap, a solution of, for example, sodium hydroxide is fed via line 65 and into the pulp distributed through the outlet ports 81, 83, 85, which are located in the middle level, during washing water is fed via the line 87, and is distributed in the pulp through the remaining outlet openings, from dsnen some are located in a lower position and some in a higher position than the level at which the alkali solution is distributed will. -

For the pulp, the-to the height of the lowest part of the Screen body has risen, the chlorine bleaching is completed.

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-lose and the resulting soluble reaction products must be removed. They are therefore displaced by washing water that comes from the bottom row of outlet openings 111, 113> 115 is distributed, and a corresponding amount Displaced liquid from the lowermost zone of the screen body and via line 5 7 to the drain. The alkali solution, which is distributed in the middle height through the spray tube outlets 81, 83, 85, in turn displaces the washing water and causes this to exit through the central zone of the screen bodies as far as the discharge line 55. Eventually ousted the washing water flowing through the upper spray tube outlets Io5, Io7, Io9 is supplied, the alkali solution from the top Zone of the screen body out and on to the discharge line 53, so that the tower through the outlet 17 leaves Pulp is washed sufficiently pure, so that it can be carried out with new chemical bleaches can be mixed in a subsequent bleaching stage in another tower.

As shown in Fig. 2, because of the axially upward movement of the pulp and the radially inwardly directed liquid flow conical interfaces between the pulp broad parts, the different liquids included, formed. Since these interfaces are not sharp, but rather mixed layers arise

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the quantities and flow rates of the through the Spray pipes supplied liquids are adjusted so that a certain over-displacement takes place, in which Washing liquid in the lowest as well as in the middle Cavity of the screen body can enter. However, all or almost all of the alkali solution will pass through the central zone the sieve body is screened off. It can be useful to branch off a line 117 from the line 55, through which Alkali is diverted to keep a portion in circulation in such a way that it coincides with that supplied by line 65 newly added alkali is mixed, so that the recycled Alkali is fed to the spray pipes, which have their outlets in the middle height. The rest of the screened off alkali is via line 119 either a preceding alkali treatment stage the bleaching plant or an evaporation plant for the recovery of the alkali or optionally fed to a cooker as an admixture to the cooking liquor used in this.

The embodiment described above only constitutes an example included within the scope of the invention in different relationship can be modified. For example, dividing it by three can be based on hydration can also be applied in such a way that separate supply lines are provided and connected to the upper and lower

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Outlet ports are connected as shown in Fig. 2, in which the line 121 is not connected to the line 87, but rather connected to the discharge line 53, for example can be so that the washing water flowing in the latter and containing only traces of alkali is recycled and in the first washing stage at the level of the lowest Zone of the screen body is used.

Another modification can be the limitation of the number of zones of the sieve bodies and the liquid distribution system exist. In this MIe the top washing stage in Fig. 2 is omitted and the sieve body in the upper part of the Tower is only used to remove the reaction products resulting from the bleaching stage carried out in the main part of the tower, as well as to impregnate the pulp with chemical substances that are required for the subsequent bleaching stage, which takes place in another tower. This step may be an alkali treatment, but preferably any other treatment which is a longer one Requires reaction time, and therefore cannot be carried out in the upper end of the tower according to FIG. 1.

-. - ■ ORIGINAL BATHROOM 1098 23/1375

Claims (1)

Patent claims: 1. Plant for bleaching cellulose material with a standing cylindrical container, which is provided with a device through which pulp slurry is constantly axially can be challenged through it, as well as with a Sieve device arranged inside the container is and by a set of concentric häien sieve bodies is formed, which are located at the same height and each of which has cylindrical screen surfaces and has an inner cavity for sieving and discharging part of the liquid content of the pulp, which .Behält also with movable spray tubes for the Supply and distribution of liquid in the pulp is equipped, characterized in that the screen body is divided into height zones with separate discharge outlets are and that those with lines for the supply of various Spray tubes connected to liquids are located with their openings at different heights. 2 »Plant according to claim 1, characterized in that the 109823/137 5 The sieve body is cleared by horizontal partitions are divided. 3. Plant according to claim 1 or 2, characterized in that those cavities of the screen body, which are in the same height zone are connected to a common discharge outlet. 4. Plant according to claim I ^ 2 or 3, characterized in that that the discharge outlets from different hollow zones of the screen body through parallel channels within radial channels Arms are formed, which carry the strainer body. 5. Plant according to claim 1, characterized in that the connected to various liquid supply lines Spray tubes have their openings arranged so that they the liquid over equiaxed cylindrical surfaces distribute that have the same radius and are at different heights. 6. Plant according to claim 5, characterized in that lUo openings of the spray pipes over Ilöhzonen of essentially- 1098 23/137 5 - BAD original the same position as the height zones of the sieve bodies are distributed, so that the direction of the liquid, flow through the pulp mainly essentially is horizontal and radial. 7. Anlape according to claim 1, 5 or 6, characterized in that that the spray pipes, which distribute liquid of one kind, all of their openings are located at high altitudes have, which are different from the heights of the openings of the spray tubes, which liquid from of a different kind. 8. Plant according to claim 5, 6 or 7, characterized in that that the spray pipes intended for the distribution of washing water have their openings distributed over height zones that are above and below the elevation zone in which other spray tubes for distributing chemical bleaches have their openings. 9. Plant according to the preceding claims, characterized in that that from one of the discharge outlets of the screen body a line (117) is branched off, which with the spray 109823/1375 BADORiGlNAL pipes is connected and is used for the supply of screened liquid to the spray tubes, the openings of which are at the same height as the zone of the screen bodies connected to the aforementioned discharge outlet, or, based on the movement of the pulp, upstream this zone. lo.Process for bleaching pulp in a plant according to claims 1-9, characterized in that alkali spray pipes are fed, which openings in have an intermediate height, while washing water is supplied to spray pipes, the openings in a deeper one as well have at a higher altitude than the intermediate level mentioned, so that an alkali treatment stage in the Height of the screen body is carried out in the same container that is used for carrying out a previous bleaching stage, e.g. by means of chlorine or chlorine dioxide, is used, 11. The method according to claim Io, characterized in that Liquid that is screened off and discharged at the zone of the screen body, which is approximately at the level of the Openings of the alkali supply spray tubes located to these BAD ORIGIiSJAL 10982371375 Spray pipes partially mixed with newly added alkali is returned. 12. The method according to claim 11, characterized in that at the mentioned zone of the sieve body screened and discharged alkaline liquid which does not belong to the Spray tubes is returned to an evaporation plant for the recovery of the alkali or to a cooker for mixing with the cooking liquor used in this is forwarded. 1098 2 3/1375