DE1517186A1 - System for the continuous opening and washing of wood chips - Google Patents

Description

Improved Machinery Inc., Nashua, New Hampshire, V.St.A.

System for continuous digestion and washing

of wood chips

The invention applies to continuous digestion of fibrous materials, for example wood shavings, and concerns in particular a new type of system for Washing of the fibers after chemical treatment.

The opening up of wood chips and other fibrous materials or the like and their subsequent washing has long been carried out through a series of treatments that can be briefly summarized in the following stages: A chemical treatment of the chips carried out in the usual way under pressure and for a fairly long time, then discharging the treated chips as a pulp

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and finally washing the pulp on washing devices with cylindrical drums. In any case, a larger number of washing processes had to be carried out, like this that several drum washers had to be used, usually three or four drum washers are used, countercurrent washing with filtered liquid as in the U.S. patent No. 2 7 ^ 5 712 is shown and described.

According to the invention, a new type of system has now been created in which a drum washer or several drum washers of such a series can be omitted without the degree of washing of the pulp being significantly changed, with a continuous opening and washing first in a single boiler, usually under pressure , followed by a treatment in a series of cylindrical washers. This treatment takes place by means of an upflow boiler which has a washing water inlet at its upper end and which has devices that regulate the liquid level inside the boiler, so that above the treatment zone for the wood chips in the boiler there is a countercurrent washing zone with an overflow zone is available. The boiler itself is that shown and described in U.S. Patent No. f 2,878,116

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Execution with a mechanical device that holds the fixed Components, namely the wood chips, moved upwards in the boiler, regardless of the one in the boiler existing liquid flow to maintain a compact mass of solids spread over the entire Working height of the boiler extends, and the one lifting force directly only on the one located at the lower end of the boiler Solid particles exerts. The one achieved with the plant Ability to move a columnar mass of chips upward in the kettle only by a pressure that is only comes into play on the lower surface of this column, is of the greatest importance for the work of the new system. In no other way can the chips be fed into a large-diameter digestion vessel relatively simple devices are precisely regulated, with the working height of the boiler completely unhindered for the required chip feed and for the required uniform circulation of the treatment fluids remain.

The outflow of the washing liquid through the The washing zone through is particularly important because of the highly effective washing action taking place in the countercurrent. That Rinse off the wood chips in the overlying drainage zone is also important because it effectively removes a large proportion of the contaminated wash water

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as will be described in detail later. The inherent stability of such a Aufstromanlage is maintained by using a washing liquid, whose temperature is equal to the temperature of the treatment liquid located at the upper end of the treatment zone is in order to produce a constant density ratio in this way and undesirable mixing avoid. If several filter cylinders have to be used for washing, at least the first filter cylinder is used be replaced by the above-mentioned boiler with the ash device located therein, with as washing liquid the filtrate from the next washing device is used in the series.

The invention is described below close to the drawing, the single figure of which is a schematic Representation in side view of a system according to the invention preferred embodiment shows.

The pressure vessel 22 shown here is generally similar to that in U.S. Patent No. 2,878 II6 from March 17, 1959 shown pressure vessel, but according to the invention has a washing liquid inlet, a located below the inlet and the boiler discharge opening Flüsägkeitsabscheider and a device, which the liquid level on a below the discharge level and a level above the separation level

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regulates, so that there are three zones within the boiler, namely a digestion or cooking zone, a countercurrent diffusion washing zone above it and a top drainage zone,

The plant includes a cylindrical upright high pressure vessel 22 of generally uniform cross-sectional area which does not decrease in size at least in its upward direction. The boiler 22 has a bottom opening l3 connected to a pump 6 and has a discharge device connected to the pulp storage container at its upper end. It is important that the boiler, although it generally has a uniform cross-sectional area, nevertheless has a cross-sectional area that gradually increases upwards, for example an increase of 9 * 5 mm of the diameter for every 30 cm of height being sufficient. The feed device comprises a perforated, helically curved plate device 20 which rotates and moves up and down over a limited extent with respect to the height of the kettle within the kettle 22 near the lower end of the kettle by means of a shaft 30 which extends to the bottom of the kettle perpendicular and axially interspersed. The perforated, helically curved blade device consists of a single helically curved plate 20 which has so many perforations that the treatment liquid

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can flow through freely, but the perforations are so tight that wood chips and fiber material are prevented from passing through. The step formed by the screw-linear curved plate is closed in 5i i'Iaoaen plate, which extends vertically 2IW perforation of the upper step edge and the lower step edge. The peripheral edge of the plate 20 is close to the inner walls of the Kettle 22, so that the passage of wood chips into the bottom section of the kettle 22 is prevented.

The pressurized mixture of chips and liquid is fed to the upper surface of this plate kO via a pipe 24, the inner wall of which is arranged concentrically and at a distance from the shaft 30. The tube 24 is attached to the lower surface of the plate 20 and protrudes downwards from the plate 20, so that in this way a central opening is created between the upper radial edges and the lower radial edges of this plate 20. The lower end of the shaft 30 protrudes into a hydraulic cylinder (not shown) which is located below the boiler bottom. This lower end of the shaft .30 forms a piston in this cylinder. The cylinder is connected to a source of pressurized fluid so that the shaft with the plate 20 can be lifted to move the plate 20 up and down. The boiler pressure against

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the area present at the upper end of the shaft 30 is so large that when the cylinder pressure is released, aie Plate 20 is lowered very quickly. The pressure vessel 22 under these conditions forms an accumulator or energy storage device which quickly supplies the necessary pressure « The volume of liquid displaced by the shaft 30 changes moving up and down so that the whole Liquid volume in the vessel 22 over a limited extent s moved up and down.

The upper discharge device has a scraper rake 26, which is near the top of the kettle and scraping cooked wood chips from the top and in this way the upper end of the chip mass located within the kettle and also the upper end the chip discharge zone. The scraper rake 26 pushes the chips through the housing 28 and promotes the Chips to a perpendicular chamber 31 · In the bottom zone of this Chamber is an upward-facing, winged one Stirring device 4θ rotatably supported by a drive device 4-2 is driven. The area 44 of the The bottom chamber corresponds in its profile to the path of movement of the lower edge of the rotating wing in order to access it Way to delimit the lower end of the ground zone. In the bottom surface 44 of the bottom chamber is located below the Movement path of the stirring device provided with wings 4o

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at least one opening 46. As the stirrer rotates, each edge brushes the inlet to this opening 46 so that clogging is prevented . In the opening 46 there is a gate valve 48 with which the opening 46 can be closed. If desired, a device for diluting the pulp can be provided in the bottom zone in which the stirring device operates.

The cooked and partially washed wood chips are discharged from the gate valve 48 for storage "at outside air pressure by means of a cyclone separator 50 which is mounted on a pulp storage tank 52 with discharge device. Cyclone separators are known in the art. The cyclone separator has a tangentially directed inlet into a cylindrical container which slows the speed of the pulp coming out of gate valve 48 and separates the pulp from the entrained steam. The pulp then falls into a pulp container which has a suitable dilution device and discharge device, such as that shown in U.S. Patent No. 1,745 2γ4 is shown and described.

From the pulp storage container 52 , the pulp is fed to a series of washing devices by means of a pump 53 of the first washing device. The series consists

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in the system shown consists of two washing devices 54 and 56, however, a larger number of lashing devices can be used depending on the degree of washing required Flocks. Such washing devices and their interconnections can be found in U.S. Patent No. 2 745 274 shown and described, in which a countercurrent washing takes place ^, in which the filtrate from the subsequent washing device is used as washing liquid for the preceding washing device.

According to the embodiment shown, in addition to the feed opening 18, a liquid feed opening 19 can also be present below the lifting plate 20 through which the liquid is supplied. It is essential, however, that a liquid separator 60 is below at a distance near the bottom from the top of the boiler the discharge opening 28 of the boiler is arranged to Remove liquid from the kettle and remove the top of the digestion or cooking zone and the bottom of the to limit the underwater wasoh zone above it. Such a liquid separator 60 can be provided with a valve 61 which is regulated in the manner described below. One the liquid level The sensing filler device 62 senses the liquid level above the liquid tank 60 and below

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the discharge opening 28 and regulates this level. In the middle between the liquid separator 60 and the discharge opening 28 are for the washing liquid several inlet openings ß4 available, which are in a horizontal Level around the boiler are distributed in the circumferential direction and which are preferably close to the upper end the underwater washing zone and the 'lower end of the drainage zone, which are determined by the scanning device 62 for the liquid level is limited or determined. If desired, the washing liquid can be distributed Shower pipe or spray pipe 65 can be provided above the scraper rake 26.

In this way, three zones are created within the boiler 22; One below the liquid separator 60 existing digestion or cooking zone, and also one above the liquid / ^ keitsabscheiders 60 intermediate underwater washing zone, and also an uppermost discharge zone. A conveyor, for example a pump 66 delivers a sufficient amount of pressurized wash liquid to the ports 64 or to the shower 65 'and a heat exchanger 68 heats this liquid as required. With this new system, the treated wood chips, when they are moved past the liquid separator 60, a countercurrent flow of heated wash liquid

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subjected in the underwater washing zone, which is between the liquid separator βθ and the liquid level of the vessel 22 sensed by the sensor 62 is located. After moving beyond this mirror the treated chips are removed from the washing liquid freed and at the same time they are released by a washing liquid stream washed from the shower 65 even further. The liquid level can be adjusted, for example of the oil separator valve regulated in accordance with the discharged Spiegeländferungen of the device 62 will. However, other regulating devices for the liquid level can also be used.

Should the washing of the treated chips inside the pressure vessel be continued washing take place in a cylindrical drum washer or in several cylindrical drum washers, then countercurrent washing in the entire system is advantageous used. If two washing devices are used, as shown in the drawing, then these can Wasoh-i devices and their interconnections from that Kind as described in U.S. Patent No. 2 7 ^ 5 712 is shown and described. However, since the system according to the invention is / is connected upstream of such a series of washing devices the washer fluid nozzle washing liquid supplied or letting in the vessel 33

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from de: ;; V'iitv-jt of the next filter 5 ^ removed, the countercurrent flow of the washing liquid flowing through the filter row 54, d'o being continued by the counter-flow which flows over the washing zone present within the ileal 12.

For a successful work of an outflow- ■: iUi'scblLi, ss'c -.;: -. Sels of the kind described with a counteri ^ ti'oniwas'jiiaov · .- ':? Above a cooking zone, however, it is essential that the density of the liquid introduced into the upper zone is lower than the density of the liquid located below this zone, so that the zones are kept stable. In the other case, the liquid located in the upper zone sinks down by heat convection and mixes with the liquid located below, whereby the efficiency of the washing is reduced. According to the invention, this difference in the density of the liquids can be obtained by regulating two factors, namely the concentration and the temperature. Since the washing liquid flow in the system takes place via the washing devices 5 ^ and 56 and then via the washing zone of the boiler 22 in countercurrent, the concentration of the organic solids dissolved in the liquid is greatest immediately below the liquid separator 60 and at the inlets 64 and 65 smallest, so that way the

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desired reduction in density is achieved over the entire washing zone. In addition, the temperature the washing liquid leaving the washing device 5 ^ increased by means of the heat exchanger 68 to approximately the temperature of the cooking liquor, whereby the density of the Washing liquid is also reduced. The washing liquid is when flowing through the heat exchanger 68 in a simple manner by using the hot liquor heated from the valve 61, so that the supply of steam to this point is not necessary. By the combined effects of concentration and temperature the density of the washing liquid is decreased below the density of the cooking liquid even if the temperature the washing liquid is slightly lower. So there is only very little mixing, so that the underwater washing zone works very efficiently.

The invention thus creates a novel, countercurrent working pulp separation and washing system. Various changes within the range can be made without departing from the scope of the invention.

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Claims

Claims (3)

- 14 - J 403 Patent claims: "1, system for continuous opening and washing wood chips, with a generally upright, tall conversion kettle into which the Wood shavings and a digesting liquid nearby of the lower inlet end of the kettle are introduced essentially continuously, one near the Wood chip lifting device attached to the inlet end of this boiler, a wood chip discharge device near the top of this boiler, a device to remove treatment liquid from the boiler and a liquid drainage device in the boiler, which is a considerable distance under the wood chip discharge device is characterized by an underwater washing zone in the boiler (22) in the upper end part thereof BATH ORIGINAL 909S06 / 0756. between Meue documents (Art 7 § 1 _A b _S. 2 No. 1 sat * τ _riBB * .. 1517188 ■ between the upper liquid level ia Vis:., jo! "ind the liquid ^{discharge device ?; (1} SO) and eir-e Uasoh- k
liquid inlet device (64 oa & r 65) i ¹ '; - fl ^ ael .: a considerable distance above the liquid ¹ · -βits "ablassvorrich tung is and (6 ^) above represents ^from: ra & \ ^r ··· or direction is arranged (23), while (6 x '-ί) above. oiler is arranged under this, so that Wasehfliacsir ^ eifc can be passed through the Unterwasserwabolirione afow & L - ^. 2. Plant according to claim I ₁ gekenraeiclinefc by a row of horizontally arranged washing devices provided with permeable cylindrical drums in which the washing liquid is sucked in through the cylinder wall through a device that collects the filtrate from each washing device, by a device, which supplies at least part of the filtrate from the first washing device to the washing liquid inlet present in the vessel (22), and through a device which supplies at least part of the filtrate from each subsequent filter to the preceding filter or returns it to this filter. 3. Plant according to claim 2, characterized by a device which removes the filtrate from the first washing 909806/0756 8AD ORIGINAL contraption - 16 - J 403 device heated to a temperature equal to the temperature the liquid in the boiler at a location close to the liquid separator (60). 909806/0756 ^{ßAD or} 'G'nal.