FI73753C - FOERFARANDE FOER BEHANDLING AV FIBERMASSA MED KEMIKALIELOESNING. - Google Patents

Description

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The present invention relates to the continuous treatment of fibrous pulp with a chemical solution so as to form a web on the wire on which the chemical solution is forced.

The process usually involves several consecutive 1-solution treatments. They are best performed so that the next solution always overrides the previous one.

The invention is particularly suitable for use in the bleaching of cellulosic pulps.

10 The cellulose bleaching process consists of several successive steps in which a specific chemical is mixed into each pulp. In the continuous processes currently in use, the bleaching reaction of each step is allowed to take place in the reaction tower, after which the pulp is diluted and washed before the next bleaching step.

The disadvantages of the bleaching process described above are well known: - The process requires a lot of equipment, because each stage requires its own chemical mixer, pulp pump, tower and scrubber. This makes the investment cost high.

- The process requires a lot of energy, which also raises the operating costs considerably.

- The process requires a lot of water, which makes the handling of waste solutions problematic.

25 - The process is rather slow.

The above-mentioned disadvantages can in principle be eliminated by applying so-called displacement bleaching. In displacement bleaching, the chemical solution is passed across the pulp web, with the next treatment solution always displacing the previous one from the web. Such a process has the advantage of a particularly short reaction time. Displacement bleaching is in principle suitable for wire.

Patent publication FI 44325 describes a method for carrying out the above-mentioned displacement bleaching with a wire.

35 In it, the pulp web is fed to a wire, above which o'n a series of nozzles for successively spraying different solutions onto the surface of the pulp. Underneath the wire there is a corresponding series of discharge plates in which the solutions which have crossed the path are collected.

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Public patent application FI 479/73 also describes a similar wire displacement bleaching in which the solutions are introduced into the web from above it.

However, syr-5 etch bleaching based on the use of a flat wire as described above is very difficult to implement in practice, and it is known that such plants have never been built. There have been insurmountable problems, especially in the import of chemical solutions into the pulp web and their accurate dosing.

The object of the present invention is to provide a displacement bleaching method based on the use of a wire, in which chemical solutions can be metered and introduced into the pulp web in a controlled manner.

The pulp web to be treated in accordance with the present invention is formed between two wires. A series of chemical solution supply boxes (one or more) are placed in succession against the surface of the second wire. Solution removal housings are similarly positioned against the surface of the second wire.

Most preferably, the web runs substantially horizontally, but if desired, the pair of wires can also run in other planes and can be folded as desired.

The solutions to be dispensed can be brought into the track either from above or below, but preferably from below. The edges of the feed box can be effectively sealed against the wire. In this case, when the solutions are fed from the top, precise dosing is achieved and an overpressure can be used, which prevents possible gassing of the chemicals before feeding them to the track. When the solutions are dispensed from below, there is no disadvantage of possible gasification because the gases flow in the same direction as the liquid.

The method can be carried out with one pair of wires. However, if necessary, several successive pairs of wire can also be used, so that the drawing and cleaning of the wire can be easily arranged in practice. In this case, the joint is preferably arranged so that the end of the second wire extends further in the direction of the track than the other end, the corresponding end of the second wire of the next pair of wires being correspondingly longer.

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Some embodiments of the invention will be described with reference to the accompanying drawings. Figure 1 shows diagrammatically a side view of an apparatus according to the invention and used in a bleaching process. Figure 2 5 shows one way of arranging the junction of successively arranged pairs of wires.

The schematic apparatus shown in Fig. 1 has two superimposed endless flat wires, a lower wire 1 and an upper wire 2, between which the pulp web to be treated is taken. The direction of travel of the track is marked in the figure with arrows. The track entering the equipment is formed, for example, with a double wire (not shown in the drawings).

Below the lower wire 1, sealed to its surface, are successive feed boxes 3, to which the required solution is fed separately. Correspondingly, above the upstream 2, there are outlet housings 4 sealed to its surface, in each of which a solution which has traveled across the track is collected and passed on for further removal or, as desired, for re-use. An outlet box ‘20 corresponding to a particular feed box is located at a suitable distance forward in the direction of travel of the track. In this way, the filtrates are collected accurately separately.

Figure 1 shows a five-stage bleaching process CEDED (C = chlorine, E = alkali, D = chlorine dioxide), in which the pulp 25 is finally treated with sulfur dioxide. The flows of feed solutions and filtrates are shown in detail in the figure.

The solutions are introduced into the supply boxes by pumps. The dosing of chemicals with feed pumps can be adjusted according to the residual chemical concentrations of the filtrates. This achieves the most optimal dosing possible.

In practice, it may be advantageous to make the apparatus from several successive pairs of wires. Figure 2 shows a connection method. In it, the upper wire 2 'of the first pair of wires extends 35 in the direction of travel further than the lower wire 1'. Correspondingly, the lower wire 1 '' of the second pair of wires starts before the upper wire 2 ''. The uninterrupted passage of the track through the joint is ensured.

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Figure 2 also schematically shows the removal and escorting devices 5 and 6 acting on the lower and upper surface of the track, as well as the washing device 7 and the tensioning roller 8 of the first wire.

The apparatus shown in Figure 1 has the same number of both supply boxes and discharge boxes. However, this is not necessary, and other types of arrangements may always be appropriate according to practical needs. The length and distance of the housings from each other in the direction of the track can also be varied as required. Quite 10 different arrangements can be constructed, because the flow rate of the solutions can be controlled independently of each other by changing the supply or suction pressures. The effect of hydrostatic pressure is also made different when the track is deviated from the horizontal.

Claims (5)

73753 A method for treating a pulp with a chemical solution, comprising forming a web of fibrous pulp on a down wire (1) and feeding a chemical solution to the web, characterized in that an upper wire (2) is pressed against the top surface of the web formed of pulp down (1); through and removing the solution that has crossed the track through the wire on the opposite side of the track. 2. For the purposes of paragraph 1, a reference number 20 is shown in Figure 1 (1). Method according to Claim 1, characterized in that the solution is fed through the lower wire (1). 3 · Förfarande enligt krav 1 eller 2, k ä n n e t e c k-n e t av, att losningen mätäs account banana i efter varandra belägna purlkter sä, att en senare lösning undantränger den fcreg & ende. -25 4. Measurement of the use of fiber in the form of chemical substances, in which case the use of fibrous mass in bananas (1), in addition to the use of fibers in the banana, for the manufacture of chemical substances in bananas, 30 per cent of the banana passage, the same as in the case of overnight stays (2), the trick of which is derived from the underside (1); -an Oxl-dade banan. A method according to claim 1 or 2, characterized in that the solution is fed to the track from successive points so that the latter solution displaces the former from its path. 4. An apparatus for treating a pulp with a chemical solution, the apparatus comprising a lower wire (1) on which the pulp is formed into a web, a solution feeding device for feeding a kamikaze solution to the web, and a solution removal device for removing a cross-web solution, further comprising ), which is pressed against the upper surface of the web formed of fiber pulp on the lower wire (1). Apparatus according to claim 4, characterized in that the lower wire (1) is connected to a solution supply device (3) for feeding solution through it to the web and that the upper wire (2) is connected to a solution discharge device (4) for removing solution through it from the web. Apparatus according to Claim 4, characterized in that an end and discharge device (5/6) acting on the track is connected to the end 30 of the lower wire d ') or upstream (2'). Apparatus according to one of the preceding claims 4 to 6, characterized in that the end of the second wire (2 ') extends further in the direction of the path than the end of the second wire (1 *). Apparatus according to one of the preceding claims 4 to 7, characterized in that the beginning of the second wire (2'M) is arranged to start in the direction of the track later than the beginning of the second wire (! ''). _ _ ____ - - TTT ..... e 73753 Apparatus according to one of the preceding claims 4 to 8, characterized in that a solution feeding device or a solution removal device consisting of a plurality of successive supply housings (3) or discharge housings (4) is connected to the lower wire (1) or the upper wire (2). ). Apparatus according to Claim 9, characterized in that there are as many feed boxes (3) as outlet rollers (4). 10 1. Förfarande för behandling av en fiberraassn med en kemikalielösning, i vilket förfarande av fibennasoan bil-das en banana pa en undervira (1) och mätäs kemikalielösning account banana, kännetecknat av, att not den övre ytan av den av fibermassan pä underviran ( 1) picture of banana 15 trickes en övervira (2), natas kemikalielösning account banana igencm n ^ gondera viran och o.vlägsnas den tvärsover banan passerade losningen Yesom den ρέ. banans hunt sida be-lägna post. 5 · Anläggning enligt krav 4, k änneteo n. Nad 35 av, att till underviran (1) har unslutits cn lesnmgsnatar-anordning (3) för att yesom den Mata lösning account banan ooh att account everviran (2) har anslutits lösningsutmatrmgsanord- r.ingen (4) för att Yesom den avl & Genn lösning banan.