FI63976B - FOERFARANDE FOER KONTINUERLIG BEHANDLING AV FIBERMASSA - Google Patents

Description

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Sweden-Sverige (SE) 7507 ^ * 9-2 (Tl) Aktiebolaget Karlstads Mekaniska Werkstad, 20, Verkstadsgatan, S-652 21 Karlstad, Sweden-Sverige (SE) (72) Lars Erik Karl Axel Tell, Karlstad, Per Hjalmar Malmström , Skived,

The present invention relates to a method for the continuous processing of fibrous pulp, comprising passing a liquid-permeable strainer element through a web of endless webs. , a washing zone, a treatment zone and a compression zone in that order, that the fibrous suspension of cellulosic material is fed to the web forming zone and is made to dry on the fiber web as a as a gas phase and that the fibrous web is subjected to compression in the compression zone.

The invention also relates to an apparatus for carrying out the method, comprising a rotating drum provided with a jacket made of a liquid-permeable wing element, an internal drainage pipe and operating and speed control devices, a hood enclosing the drum between the drum equipped with a fiber-pension inlet pipe, a washing zone connected via perforations in the dome to one or more washing liquid chambers located outside the dome, a treatment zone connected via perforations in the dome to one or more chambers outside the dome, a compression zone, 63976, the rotatable press roll forms a compression gap with the drum jacket, characterized by a sealing zone between the washing zone and the treatment zone, comprising a compression gap between the press member and the drum, and that the drum and the radial distance between the dome in the treatment zone exceeds the smallest radial distance between the drum and the pressing member in the sealing zone.

Different types of processing of cellulosic fibrous pulp require, for example, washing and bleaching in the pulping process. The bleaching of the pulp requires treatment in several stages and takes place in such a way that the reaction medium is fed to the pulp in each stage. Swedish Patent Publication 357,779 provides a detailed explanation for processing at different stages and comparisons between the results obtained in high and low concentration bleaching.

The exchange of a pulp liquid for another liquid is known from Swedish patent 350,290, which describes the device required for this purpose. However, there are drawbacks to the use of the apparatus described in this patent for handling pulp. The treatment must be carried out at a relatively low concentration of the pulp, not exceeding 12%. The liquid is exchanged between two perforated conveyor belts on both sides of a closed fibrous cake. The treatment liquid is passed to the fibrous cake and mixed with the liquid therein, after which the liquid mixture is removed from the fibrous cake. The treatment involves diluting the liquid in the fibrous cake, which is partially removed when diluted.

It is an object of the present invention to provide a method and apparatus by which a treatment medium in a liquid or gas stage can be introduced into its fiber and impregnated in a high concentration (18-50%) in a fast and simple manner, eliminating or at least substantially reducing the disadvantages of the prior art.

A problem to be solved by the present invention is how the treatment medium in the liquid or gas stage can be rapidly introduced into the pulp to be treated at high concentration (18-50%) and then evenly distribute the medium into the pulp so that it comes into contact with private fibers. .

The invention solves the above-mentioned problem as set out in the following claims.

3,63976

The invention achieves several advantages, especially when applied to granular wire technology for bleaching fibrous pulp. Impregnation of the pulp with the reactants used in high concentration bleaching processes causes the reaction to proceed more rapidly than at low concentration. Swedish Patent 357,779 shows in Table 1 the bleaching of pulp at a concentration of 30% (maximum concentration) compared to a bleaching process of the same pulp grade at a concentration of 3-12% (low concentration). The comparison shows that the total reaction time at low concentration was 600 minutes and at high concentration 63 minutes. The reported consumption of chemicals at high concentrations is only about 56% of the consumption of chemicals at low concentrations. The reduction in the reaction time of the high-concentration mixture in bleaching to almost one-tenth of that of the low-concentration bleaching means that the volume of pulp that must be fitted to the bleach during the process is considerably reduced. The volume of equipment and processing vessels required for bleaching can be substantially reduced.

Most processing steps in the bleaching process require that the pulp be maintained at a relatively high temperature of 70-100 ° C. At high pulp concentrations, less energy is required for heating compared to energy consumption compared to bleaching at normal low pulp concentrations.

The invention can also be applied to the heating or cooling of pulp at higher concentrations by way of example, which means lower energy consumption.

The device according to the invention will be explained below with reference to the figures of the accompanying drawings.

Fig. 1 schematically shows a cross-section of a device according to the invention.

Fig. 2 shows schematically the course of the displacement of the washing liquid and the subsequent course of impregnation.

Fig. 3 schematically shows an alternative embodiment in cross section of the top of the device.

The device according to Figure 1 comprises a rotatable drum 11 with a jacket 13 made of a liquid-permeable strainer element. The drum 11 is mounted by shaft pins 15 on the machine frame (not shown) and equipped with drive and speed control devices 17. A hood 19 is arranged outside the drum 11. space between it and the sheath 13 of the drum 4 in such a way that the radial distance decreases from the sheath 13 to the dome 19 from the beginning of the space 21 to the part at its end as seen in the direction of rotation of the drum 11. At the beginning of the space 21, the hood 19 has adjustable inlet devices 23 for the fiber suspension, which are adapted to distribute the suspension flow evenly over the entire width of the jacket 13. The first part of the space 21, seen in the direction of rotation of the drum, acts as a web forming zone 25 in the space 21. In said direction of rotation there is then a washing zone 27, a sealing zone 29, a treatment zone 31 and a compression zone 33. Along the washing zone 27 and the processing zone 31 Outside the figure 19, at the washing zone 27, a washing liquid chamber 35 is placed for supplying the washing liquid through the holes in the figure 19. A second chamber 37 is located outside the dome 19 at the treatment zone 31 to conduct the treatment fluid through the holes in the dome 19. The washing liquid chamber 35 is provided with one or more inlet pipes 34 provided with servo-controlled control valves 41. Between the washing zone 27 and the treatment zone 31 there is a rotatable pressure roller 47 without a liquid-permeable jacket and forming a seal with the jacket 11 31 is followed by a press roll 49 without a liquid permeable jacket. The compression rollers 47 and 49 are mounted on shaft pins 51 and 53, respectively, on the same body of the machine as the drum 11 and form compression slots 55 and 57 with the casing 13 of the drum 11, respectively, which are substantially unchanged during operation. The shaft pins 53 of the compression roller 49 are provided with pressure measuring means 59 / for example strain gauges 59 adapted to transmit signals corresponding to the line pressure of the compression gap 57. After the compression gap 57, there is an discharge and discharge device 61 formed by a jacket 63 / surrounding a combined tear and exit screw 65. The jacket 63 is provided with a scraper 67 terminating against the housing 13 of the drum 11 and a sealing device 69 terminating against the compression roller 49. the steam supply pipe 71 with its valves 73 is connected to the jacket 63. The outlet device 61 is provided with a connecting flange (not shown in the drawings) fitted to the outlet end of the device for a sealing connection for the next processing device. To control the flow of the web formation and the washing and the flow of the treatment, there is a control system comprising a control device 75 connected by lines 77, 79, 81, 83 to a pressure measuring device 59, a drum speed control device 17, a washing liquid chamber 35 control valve 41 and a chamber 37 control valve 45, respectively. The components of the control system 5 63976 may be electrical, hydraulic, pneumatic or mechanical devices of known quality. An outlet pipe 85 is provided for discharging the liquid entering the drum 11.

The device according to Figure 1 operates as follows:

In a unit of time, a constant volume of fiber suspension 87 is introduced under pressure into the web soldering zone 25 of the space 21 through the inlet devices 23, at the same time as the drum 11 is made to rotate at a substantially constant speed. Due to the pressure difference between the space 21 and the interior of the drum 11, the suspension liquid 89 flows through the jacket 13 of the drum 11 and a fibrous web 91 is formed on the surface of the jacket 13. As it passes on the surface of the sheath 13 through the web forming zone 25, the fibrous web grows thicker and thicker until it fills the space between the sheath 13 and the dome 19. Thereafter, the fibrous web 91 is subjected to continuous compression as it passes into the sealing zone 29 due to the convergence of the space 21 in the direction of rotation of the drum, whereby the suspension liquid 89 is compressed through the jacket 13. As the fibrous web passes through the wash zone 27, a constant volume of wash liquid is pressed per unit time into the fibrous web 91 under pressure through the perforations in Figure 19. The wash liquid 93 displaces the remaining suspension liquid 89 in the fibrous web 91. -A '(see Fig. 2). The displaced suspension liquid 89 flows through the jacket 13. As it passes between the washing zone 27 and the sealing zone 29, therefore, only the layer 13 of the fibrous web 91 closest to the jacket, i.e. below the line Λ-A ", contains the suspension liquid, while the fibrous web otherwise contains only the washing liquid 93. to a concentration of 30-70%, an additional step to a thickness less than the thickness of the portion of the fibrous web 91 which at the beginning of the sealing zone 29 contains only washing liquid 93. Since the casing of the press roll 47 is closed, dewatering in the press gap 55 takes place only through the drum 11 jacket 13. the suspension liquid 89 remaining in the fibrous web 91 and then a part of the washing liquid 93 is squeezed out through the jacket 13 of the drum 11. Thus only a certain amount of washing liquid 93 is squeezed out through the jacket 13 and mixes with the suspension liquid inside the drum 11.

After the fibrous web has passed through the compression gap 55 in the sealing zone 29, it is allowed to expand freely in the treatment zone 6 63976 at the same time as a constant volume of impregnating liquid 95 per unit time is pressed through the perforations in Fig. 19 into the fibrous web 91. again tends to fill the cavities created by the swelling, the impregnation fluid penetrates the fibrous web very quickly and efficiently. In the last part of the impregnation zone 31 with respect to the direction of rotation of the drum 11, the impregnation liquid 95 causes the washing liquid remaining in the fibrous web, largely after the compression gap 55, to be displaced. The boundary layer between the impregnating liquid and the washing liquid is formed in the fibrous web along the line B-B '(see Fig. 2). The displaced washing liquid flows through the jacket 13. The displacement process, which occurs in the same way as the described displacement process of the washing liquid and the suspension liquid, reaches its peak in the compression gap 57, where the washing liquid is squeezed out and part of the impregnating liquid penetrates through the fibrous web into the drum 11. Due to the high compression in the compression gap 55 of the fibrous web, the fibrous web 91 acts as a seal in the sealing zone 29 between the washing zone 27 and the treatment zone 31 and prevents the flow of treatment liquid from the treatment zone 31 to the washing zone 27.

In order for the displacement to be desired, i.e. the displacement of the washing liquid on the line A-A'and the displacement of the impregnating liquid on the line BB '(Fig. 2), the following variables are comparable in the control system, namely the line pressure of the compression gap 57, the drum 11 speed and the washing liquid flow 93 volumes. The extent of the compression gap 57 as well as the flow of the fiber suspension are kept essentially unchanged by devices known per se not shown in the figures. During operation, the pressure measuring device 59 sends continuous signals indicating the actual values of the line pressure to the control device 75, where they are compared with the set target value. If there is a difference between these values, the control device 75 sends correction signals to the speed control devices 17 of the drum 11 in such a way that when the line pressure decreases, the speed of the drum 11 decreases. The control device 75 simultaneously sends signals, depending on the actual value of the drum speed, to the servo-controlled control valves 41 and 45 to correct the flow of the washing liquid 93 to the washing liquid chamber 35 and the flow of the impregnating liquid 95, respectively.

As the fibrous web 91 passes through the compression gap 57 of the compression zone 33, it is separated by a scraper 67 from the jacket 13 of the drum 11 and passed to a release and discharge device 61. Here the fibrous web is allowed to expand freely and tends to fill the cavities.

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A gaseous medium, preferably water vapor, is introduced into the discharge and discharge device 61 under pressure via a supply pipe 71.

The above-mentioned cavities are filled with a gaseous medium which prevents the absorption of air into the fibrous web. The fibrous web is torn and transported under pressure from the device with a tear and feed screw 65 to the next stage of the manufacturing process.

The device according to Fig. 3 is similar and otherwise works in the same way as the device according to Figs. 1 and 2, except that the sealing zone is formed by a step 97 arranged in the dome 19, which gradually reduces the radial distance between the hood 19 and the drum 11 in the compression gap 99. after that said radial distance increases immediately, so that the fibrous web to be processed in the device is here essentially free to expand.

The following claims state that the treatment medium may be a treatment medium useful for the production of cellulosic fibrous pulp. In this case, in addition to the usual bleaching agents such as chlorine, chlorine dioxide, hydrogen peroxide, oxygen gas, etc., reactants and catalysts such as sodium hydroxide, ammonia, magnesium carbonate, alkali metal borates and the like, as well as combinations of the above, can also be used.

Claims (6)

63976 8 A method of continuously treating a pulp, the method comprising continuously feeding a fibrous suspension (87) of cellulosic material in a suspension liquid (89) to a wider end of a first tapered portion (25) of a treatment channel (21) formed by an endless web of liquid-permeable screen element (13) between the dome (19), the fed fiber suspension (87) is caused to flow on the movable fibrous web (91) by a sieve element (13) to such a thickness that at the end of the first part (25) the fibrous web completely fills the cross-section of the duct (21); under pressure, the formed fibrous web (91) is passed through a second, continuously converging channel portion (27), wherein in this second portion (27) a treatment fluid (93) is fed to the fibrous web (91) to displace the suspension liquid (89) remaining in the fibrous web, followed by the fibrous web (91) compresses 30 and 70% v between the strainer element (13) and a rotating press roll (47) having a radius of then the fibrous web (91) is passed through a third portion (31) of the treatment passage (21), and in this third portion the fibrous web (91) is allowed to swell to the point of strong compression at the compression point (55) while liquid or gaseous pressurized impregnation fluid (95) fed to the fibrous web (91). Method according to Claim 1, characterized in that the impregnating liquid (95) has bleaching properties. A method according to claim 1, characterized in that the impregnation liquid (95) consists essentially of water vapor. 1 2 II Apparatus for the continuous treatment of pulp for carrying out the method according to claim 1, the apparatus comprising a rotating drum (11) provided with a jacket (13) as a liquid-permeable wing element 2, an internal outlet pipe (85) 9 63976 and drive and speed control devices ( 17), and a hood (19) enclosing the drum (11) arranged to define a circumferential treatment channel (21) between itself and the jacket (13) of the drum (11), the channel having a first channel portion tapering in the direction of rotation of the drum (11) (25) having an inlet end and means (23) for feeding a fiber suspension (87) of cellulosic material from the suspension liquid (89) to the inlet end to form a fibrous web (91) on the drum jacket (13) by draining the suspension fluid (89) through the jacket (13) ), wherein the radial height of the second end of the first channel part (25) is such that the fibrous web (91) completely fills the cross-section of the channel there. and in which the channel has a second, continuously converging channel portion (27) and means (35, 39, 41) for supplying the treatment liquid (93) to the fibrous web (91) to displace the suspension liquid still in the fibrous web into the drum (11), the second channel portion (27) · * Conforms to a rotating roll (47) having a larger radius than the minimum radial height of the second channel part (27), which roll with the sheath (13) of the drum (11) forms a pressing point (55) capable of pressing the fibrous web (91) to a dry content of about 30 -70%, characterized in that the treatment channel (21) has a third channel part (31) after the press roll (47), provided with means (37, 43, 45) for supplying a liquid or gaseous impregnating liquid (95) to the fibrous web (91) under pressure. ) that the radial height of the third channel part (31) is greater than the width of the gap of the nip (55), whereby the fiber web (91) expands from the nip (55) due to the rotation of the roller (47) and the drum (11) Steen (95) penetrating inside it. Device according to claim 4, characterized by means (39, 41, 59, 75, 81) for quantitatively controlling the supply of treatment liquid (93) to the second channel part (27). Device according to claim 4 or 5, characterized by means (43, 45, 59, 75 and 83) for quantitatively controlling the supply of the impregnating liquid (95) to the third channel part (31). 10 63976 Device according to claim 5 or 6, characterized in that the means for carrying out the quantitative adjustment comprise pressure measuring means (59) arranged to detect line pressure at a second pressing point (57) formed by a pressing roller (49) and a drum arranged after the third channel part (31). (11), and control means (75) arranged to control the speed of the drum (11) depending on said line pressure. it 11 63976