JP2004232184A - Feeder and method for comminuted cellulose fibrous material using high pressure screw and centrifugal pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a feeder for comminuted cellulose fibrous material simplifying the apparatus, capable of dramatically reducing required numbers of the apparatus elements. <P>SOLUTION: The system for producing chemical cellulose pulp from comminuted fibrous cellulose material, comprising:a steaming vessel in which comminuted fibrous cellulose material is steamed to remove the air therefrom; a superatmospheric pressure vertical treatment vessel having an inlet for a slurry of comminuted cellulose fibrous material at a top portion thereof and an outlet at a bottom portion thereof; and a plurality of high pressure slurry pumps located below said top portion of said treatment vessel for pressurizing a slurry of material from the steaming vessel and transferring it to the treatment vessel inlet, the plurality of high pressure slurry pumps includes a first screw pump and at least one second pump. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an apparatus and a method for feeding a comminuted cellulosic fiber material to a treatment tank such as a continuous digester. According to the present invention, the apparatus is simplified and the number of required device elements is dramatically reduced as compared with the existing technology.

  U.S. Pat. Nos. 5,476,572, 5,622,598, 5,635,025 and 5,766,418 describe the processing of comminuted cellulosic fibrous materials which has been performed for over 40 years. It brought the first real breakthrough in tank feeding technology. These patents show several embodiments for feeding the comminuted cellulosic fiber material to the digester using, inter alia, a slurry pump, and these are Andritz Inc., located in Glenfalls, NY, USA. And sold comprehensively by Andritz Inc. under the Lo-Level trademark.

  As described in these patents, using such a pump to transfer the slurry to a high-pressure transfer device requires the required equipment complexity and physical size. Is dramatically reduced, making operation and maintenance easier. Conventional feeders use high-pressure conveyors, such as the High-Pressure Feeder sold by Andritz, Inc., which, without such a pump, was used in the 1940s and years. It was sold in the 1950s and is essentially the same as the equipment built.

  The present invention relates to an apparatus and a method which further dramatically improve the apparatus and the method disclosed in the above-mentioned patent specification. Indeed, the present invention eliminates the need for a transport device such as a high pressure feeder by using a high pressure pump device to transport the comminuted cellulosic fiber material directly to the digester.

  The reaction of the pulping agent with the comminuted cellulosic fibrous material to produce a chemical pulp requires a temperature of 140-180C. Commercial chemical pulping is carried out in pressure-resistant vessels under a pressure of at least 1034 kPaG (about 10 bar or about 150 psig), since the water-soluble agents used to process the comminuted cellulosic fiber material boil at the above temperatures. This is usually done. Particularly when performing a continuous pulping process, in order to maintain the above pressure, it is necessary to provide a special device to prevent a pressure drop when the comminuted cellulose fiber material is introduced into the pressure tank. In the prior art, this pressure drop prevention has been performed by a device known in the art as a "high pressure feeder". This high pressure feeder is a specially designed device that includes a pocket rotor that acts as a means for transferring the slurry of the comminuted cellulosic fibrous material from low pressure to high pressure and also acts as a valve to prevent pressure drop. is there. This complex and expensive apparatus has long been recognized as an essential element for introducing a slurry of comminuted cellulosic fibrous material into a pressurized vessel, usually at elevated temperatures, especially a continuous digester.

  The present invention provides an alternative to a high pressure feeder that has been recognized as essential to continuous digesters for over 40 years and greatly simplifies pulp mill construction. The apparatus of the present invention includes at least first and second high pressure slurry pumps connected in series, which replace conventional pressure feeders. The first high-pressure slurry pump is a conventional single-blade screw pump, and the second or subsequent high-pressure slurry pump is a centrifugal pump.

According to one aspect, an apparatus for producing chemical cellulose pulp from comminuted cellulose fiber material such as wood chips comprises the following elements:
A steam treatment tank for removing air by steaming the comminuted cellulose fiber material;
A pressurized vertical processing tank having an inlet at its top for a slurry of the comminuted cellulosic fibrous material, and an outlet at the bottom thereof; and Including pressurized conveying means for conveying to the inlet of the pressure vertical processing tank,
The pressurized conveying means includes one or more high-pressure slurry pumps located below the top of the pressurized vertical processing tank.

  The one or more pumps preferably include first and second high pressure slurry pumps connected in series, each pump having a pressure rating and having an inlet and an outlet. The inlet of the first pump is operatively connected to the steam treatment tank, the outlet of the first pump is operatively connected to the inlet of the second pump, and the second pump is connected to the first pump. Has a higher pressure rating. The first high-pressure slurry pump may be a single-blade screw pump. The second high pressure slurry pump is a helical screw centrifugal pump, double piston solids pump, or other similar conventional pump, which pumps a slurry containing a relatively high solids concentration (by one or more steps) to a gauge pressure. To at least about 517 kPa (5 bar). Pressurization and transport of the slurry can also be performed by one or more conventional eductors driven by pressurized fluid supply by a conventional centrifugal pump.

  The unit of measurement that indicates the relative amount of solids in a slurry containing solids and liquids is usually the "liquid-to-solid ratio". As used herein, this ratio is the ratio of the volume of liquid transported to the volume of comminuted cellulosic material transported. Typical conventional centrifugal liquid pumps are limited to pumping liquids having a solids content of at most 3%. This 3% solids content corresponds to a liquid to solids ratio of about 33. In the slurry pump of the present invention, the ratio of liquid to solids in the pumped slurry is typically 2-10, preferably 3-7, and most preferably 3-6. In other words, the slurry pump of the present invention can convey a slurry having a higher solids content than is handled by conventional pumps.

  A liquid return line from the top of the processing vessel is provided, the liquid return line containing liquid separated from the slurry at the top of the processing vessel (preferably a continuous digester). The return line is operatively connected directly or indirectly to one inlet or outlet of the slurry pump. Preferably, the liquid return line is connected to a pressure reducing means for reducing the pressure of the liquid in the liquid return line before the liquid is conveyed to the inlet or outlet of the slurry pump. The pressure reducing means may take various forms, for example a flash tank and / or a pressure control valve in the return line, or effectively reduce the pressure of the liquid in the line without adversely affecting the liquid. Other conventional structures can be employed. If a flash tank is used, the liquid outlet from the flash tank is connected to the inlet to the first slurry pump, and the steam generated by the flash tank is used in a steam treatment tank.

  Further, by using an eductor using the pressurized liquid in the return line as the pressurized liquid source, the pressure may be reduced or the pressure can be prevented. The eductor is used to convey the slurry to the digester instead of or with one or more slurry pumps or other equipment.

  A conventional chute as well as other optional elements are preferably connected between the steam treatment tank and the at least one slurry pump, wherein the steam treatment tank is located above the chute and the chute is connected to the at least one slurry pump. It is arranged above. The at least one slurry pump is located at least about 9.2 meters (30 feet) below the top of the digester, and more typically is usually located about 15.3 meters (50 feet) below.

  When the high-pressure transfer device is removed, it retains one function of the high-pressure transfer device, that is, the function of preventing pressure leakage when an abnormal condition occurs, and prevents the liquid from flowing back from the digester to the supply device. It is desirable to employ another mechanism for this.

  The pressure leak prevention means of the present invention is separated from at least one slurry pump, although under certain circumstances the inlet to the slurry pump or the outlet from the slurry pump is constructed to prevent pressure leaks Is preferred. The pressure leak prevention means has an automatic isolation valve in the slurry conduit for transporting the slurry from the pump to the top of the processing tank, and in the return line from the processing tank, respectively. The isolation valve is operated in response to a pressure sensed by a pressure sensor provided in connection with the slurry conduit for supplying slurry to the top of the processing vessel. The pressure leak prevention means may be a check valve in the slurry conduit, and / or various other valves, tanks, sensors, controllers, or equivalent fluid, mechanical, electronics, which perform a pressure leak prevention function. Elements can be included.

  The apparatus of the present invention provides for the flow of fluid to an inlet to a second slurry pump, the flow of fluid to any pump or conveying means, such as a liquid line containing a liquid at a lower pressure than the inlet at the second slurry pump. And means for increasing the flow of liquid to the conduit between the liquid line and the inlet and to the liquid pump in the conduit. The liquid line may be a return line from the treatment tank, and the conduit is connected directly to the return line. The liquid return line can be connected to a vapor flash tank as described above, and the conduit can be connected to a flash tank liquid outlet.

According to another aspect, there is provided a method for supplying a comminuted cellulosic fiber material to the top of a processing vessel, the method comprising the following steps:
(A) removing the air by steaming the comminuted cellulose fiber material;
(B) slurrying the comminuted cellulosic fibrous material with a cooking liquor to produce a slurry of the liquid and the comminuted cellulosic fibrous material; 30 feet), preferably at least 50 feet (15.3 meters) below, pressurize at a pressure of at least about 517 kPa (5 bar) at a gauge pressure and compress the pressurized comminuted cellulosic fiber material to the top of the treatment vessel. And pressurizing comprises applying the slurry to the slurry using one or more high-pressure slurry pumps.

The method may further include the following steps.
(D) returning the liquid separated from the slurry at the top of the processing tank to at least one pump; and (e) sensing the pressure of the slurry while being transported to the top of the processing tank, and setting the sensed pressure to a preset value. Closing the flow of the slurry to the top of the processing tank and the return of the liquid from the top of the processing tank when the value falls below the set value.

The method may also include the following steps.
(F) flashing the liquid returned in performing step (d) to produce steam and using this steam in performing step (a).

  In another aspect, the concept of transporting a slurry of chips can be traced back to the point where the chips are introduced into the factory, ie, a wood repository. Conventional pulp mills accept milled cellulose fiber material in various forms, usually hardwood and softwood, but also handle the other cellulosic fiber materials described above. These morphologies include sawdust, chips, logs, long cut timbers (ie, “trees”), and complete trees (ie, “entire trees”). Depending on the "wood feed" cellulose source, the wood is converted to chip form so that it can be handled and processed in the pulping process. For example, a device known as a "chipper" is for converting long trees or logs into chips stored in open chip piles or chip silos. The receipt, handling and storage of the chips takes place in one area of the pulp mill called the "woodyard." From the woodyard, the chips are transported to a pulp mill suitable for starting the pulping process.

  In a conventional woodyard, chips are stored in silos and discharged from the silos to a conveyor, typically by a rotary or vibratory silo discharge device. This conveyor is usually a belt type conveyor that receives chips and transports them to a pulping tank. Because the wood yard is typically at some distance from the pulping tank, the conveyor is typically long, some up to 1.5 miles (2.4 km). Additionally, described in U.S. Patent Nos. 5,476,572, 5,622,598, 5,635,025 and 5,766,416, and sold by Andritz, Inc. Processing equipment without the Lo-Level (R) feeder requires that the conveyor be raised, typically to a height of at least 30.5 meters (100 feet), to feed chips to the inlet of the first pulping tank. is there. These conveyors and the structures that support them are very expensive and have a significant impact on the cost of the digester feeder.

In another embodiment, the concept of transporting the slurry of chips goes back to the woodyard. A preferred embodiment of the present invention comprises a method of conveying the comminuted cellulosic fiber material to a pulping process, the method comprising the following steps:
(A) introducing an untreated chip into the first tank;
(B) introducing a slurried liquid into the first tank to produce a slurry of the comminuted cellulose fiber material and the liquid;
(C) discharging the slurry from the first tank to the inlet of at least one pressurized conveying device, and (d) pressing the slurry in the pressurized slurry forming device and conveying the slurry to the processing tank. Become.

  The first tank is typically a storage silo or storage tank for chips. Preferably, the storage tank has a one-dimensional tapered discharge without agitation or vibration means, such as the DIAMONDBACK® storage tank described in US Pat. No. 5,500,083. Stirring or vibration means may be used. The reservoir may have more than one outlet for feeding to more than one transport device. This tank is operated, for example, under a pressure of 10.3 to 517 kPa (0.1 to 5 bar). When the vessel is operated under pressure, some form of pressure isolation device is placed at the entrance of the vessel to prevent pressure leaks. The device may be a star-type isolator, such as a low pressure feeder or an airlock feeder sold by Andritz, Inc., or a screw having a sealing capability as described in US Pat. No. 5,766,416. It may be a mold feeder.

The slurried liquid can be from any liquid source present in the pulp mill, including fresh water, vapor condensate, kraft white liquor, kraft black liquor, kraft green liquor, sulphite liquor, and any other pulping-related Contains liquid. The liquid may be a heated liquid, for example, hot water or steam having a temperature of 50C to 100C. When the above-mentioned tank is a pressurized tank, a liquid temperature exceeding 100 ° C. is used. Although not required, the liquid can include at least some active pulping agent, such as sodium hydroxide (NaOH), sodium sulfide (Na ₂ S), polysulfide, anthraquinone, or any of these. Or surfactants, enzymes, chelates, or combinations thereof.

  The pressurizing and conveying device in step (c) and step (d) is preferably a slurry pump or a plurality of slurry pumps, but other pressurizing and conveying devices such as a piston type solid pump and a high pressure eductor may be used. it can. Preferably, one or more pressurized slurry pumps are used to convey the slurry. These may be two or more slurry pumps or a combination of a slurry pump, a piston type pump and an eductor. The transport device may include one or more storage or surge tanks with the transport means. Preferably, the one or more transporting means includes at least one means capable of degassing to remove unwanted air and other gases from the slurry. Also, during transport, the chips may be subjected to some kind of treatment, examples of which include deaeration and impregnation with a liquid, preferably a liquid containing the pulping agent described above. The slurry may also be exposed to at least one pressure change or pressure change during transport, for example, changing the pressure of the slurry from a first pressure to a higher second pressure, and then optionally lowering the second pressure. It can be changed to a third pressure. Varying the pressure of the slurry of chips and liquid improves the impregnation of the chips with the liquid, as described in U.S. Pat. Nos. 4,057,461 and 4,743,338. This pressure fluctuation is achieved by changing the outlet pressure of a series of conveying means arranged in series or by a controlled pressure drop of the slurry during pumping.

  In another embodiment, the comminuted cellulosic fibrous material need not be in contact with the liquid in the vessel described above, but contains liquid initially introduced by an eductor located at or below the vessel outlet. can do. The liquid is preferably pressurized to form a pressurized slurry of the comminuted cellulosic fibrous material and the liquid.

  The treatment tank in step (d) may typically be the steam treatment tank described above, and is preferably a DIAMONDBACK (registered trademark) steam treatment tank. This tank may be a storage or surge tank where the comminuted cellulosic fiber material is stored before processing. Since the transport process requires an excess of liquid that is not needed during processing or storage, some form of dewatering device may be placed between the transport means and the processing tank. One preferred dewatering device is a top separator sold by Andritz, Inc. The top separator is a standard or "inverted" type top separator. This device may be an external, external stand-alone type unit, or may be provided directly on the processing tank. An in-line drainer sold by Andritz, Inc. can be used as the dewatering device. The liquid removed from the slurry by the dewatering device is returned to the first tank or the transport means and used as a slurry liquid. This liquid can also be used where needed in a pulp mill. This liquid can be heated or cooled as desired. For example, the liquid may be heated by indirect heat exchange with a heated liquid stream, such as a waste liquid stream having a temperature of 50 ° C. or more. This liquid is also typically pressurized by using one or more conventional centrifugal pumps.

  In one preferred embodiment, the treatment tank in step (d) is a steam treatment tank that supplies one or more transport means as described above. The apparatus is preferably used with a feeder without a conventional high pressure feeder, but the apparatus may be used with a feeder with a high pressure feeder.

  The method and apparatus for feeding chips from a remote location, e.g., a woodyard, to the pulping process is not limited to the chemical pulping process, but any pulping process in which the comminuted cellulosic fiber material is transported from one location to another. Can also be used. The pulping process to which the present invention applies is all chemical pulping processes, all mechanical pulping processes, and all chemical-mechanical pulping or thermo-mechanical pulping processes, whether batch or continuous. It can also be applied to

  Although the apparatus shown in FIGS. 1 to 3 is a continuous digester apparatus, the apparatus of the present invention comprises a cellulose fiber material in one or more batch digesters or an impregnation tank connected to the continuous digester. It can be understood that it can be used to provide The continuous digester shown and used in the present invention is preferably a KAMMY® continuous digester, which may include kraft pulping (eg, sulphate pulping), sulphite pulping, soda pulp. Or similar processes. Specific digestion methods and equipment used include MCC®, EMCC®, and Lo-Solids® type processes and digesters sold by Andritz Incorporated. Retention agents of strength or yield, such as anthraquinone, polysulfide, or equivalents or derivatives thereof, can be used in the digestion process using the present invention.

  FIG. 1 shows a typical prior art apparatus 10 for feeding a slurry of comminuted cellulosic fiber material, such as soft wood chips, to the top of a continuous digester 11. The digester 11 is usually equipped with a liquid removal screen 12 at the inlet of the digester 13 to remove excess liquid from the slurry and return it to the feeder 10. The digester 11 also includes at least one liquid removal screen 14 for removing waste cooking liquor during or after the pulping process. The digester 11 typically comprises one or more additional liquid removal screens (not shown), which may be of the MCC®, EMCC® type digester digester. It can be linked to a circulation system or a cooking liquor circulation system such as a Lo-Solids (registered trademark) digester circulation system having a liquid removal conduit and a diluent addition conduit. Cooking liquors such as kraft white liquor, black liquor, green liquor are added to these circulations. The digester 11 also has an outlet 15 for discharging the manufactured chemical pulp, and the discharged chemical pulp is sent to further processing such as washing, bleaching and the like.

  In the conventional supply device 10 shown in FIG. 1, a comminuted cellulose fiber material 20 is introduced into a chip storage tank 21. Typically, the milled cellulosic fiber material 20 is soft wood or hard wood, but may be milled in any form, such as sawdust, grass, straw, bagasse, kenaf, agricultural waste, or any combination thereof. Cellulose fiber materials can also be used. The term "chip" is used in the following description to indicate a comminuted cellulosic fibrous material, but it is understood that the term is not limited to wood chips and includes any form of the comminuted cellulosic fiber material described above. It should be.

  The chip storage tank 21 is a conventional storage tank with a vibratory discharge device, or a vibratory discharge device described in US Pat. No. 5,500,083 and sold by Andritz, Inc. DIAMONDBACK® steam treatment tank without equipment, but with an outlet with one-dimensional taper and side relief. Storage tank 21 may be provided with an air barrier at the entrance, with means for observing and controlling the chip level in the storage tank, and with a vent having a mechanism suitable for controlling the pressure in the storage tank. it can. The steam, whether freshly added steam or steam obtained by evaporation of the waste liquid (e.g. flash steam), is typically added to the storage tank 21 via one or more conduits 22.

  Usually, chips are sent from the storage tank 21 to a metering device 23, for example a chip meter sold by Andritz Inc., but other forms of device such as a screw-type metering device can be used as the metering device. The chips are sent from the metering device 23 to a pressure isolation device 24, such as a low pressure feeder sold by Andritz Incorporated. The pressure isolation device 24 isolates the pressurized horizontal processing tank 25 from the essential atmospheric pressure present on the device 24.

  Vessel 25 is used to treat the comminuted cellulosic fibrous material with pressurized steam, for example, steam at about 69-138 kPaG (10-20 psig). The tank 25 includes a screw type conveyor, for example, a steam processing tank sold by Andritz Incorporated. Clean or flash steam is added to vessel 25 via one or more conduits 28.

  After treatment in tank 25, the comminuted cellulosic fiber material is transferred to a high-pressure transfer device 27, such as a high-pressure feeder sold by Andritz Incorporated. Typically, the steamed comminuted cellulosic fiber material is conveyed to a conveyor 27 by a conduit or chute 26, for example, a chip chute sold by Andritz Incorporated. A heated cooking liquor, such as a mixture of used kraft black liquor and white liquor, is added to the chute 26 via conduit 29 to produce a slurry of the comminuted cellulosic fiber material and the liquid in the chute 26. .

  1 uses the DIAMONDBACK® steam treatment tank disclosed in U.S. Pat. No. 5,500,083 that can perform improved steam treatment under atmospheric pressure. The pressure treatment tank 25 and the pressure isolation device 24 can be omitted.

  The conventional high-pressure feeder 27 includes a low-pressure inlet connected to the chute 26, a low-pressure outlet connected to the conduit 30, a high-pressure inlet connected to the conduit 33, and a high-pressure outlet connected to the conduit 34. It has a pocket rotor driven by an electric motor and a reduction gear (not shown). The heated slurry of chips is supplied from the chute 26 to the rotor pocket via a low pressure inlet. The chips are held in the rotor by the screen at the outlet 30 of the feeder 27, but the liquid in the slurry passes through the rotor and is removed via the conduit 30 and the pump 31. As the rotor rotates, the chips held in the rotor are exposed to high pressure liquid sent by pump 32 via conduit 33. This high pressure liquid slurries chips from the feeder and transports via conduit 34 to the top of digester 11. Upon reaching the inlet of the digester 11, a portion of the excess liquid used to slurry the chips in the conduit 34 is removed from the slurry by the screen 12. Excess liquid removed by screen 12 is returned to the inlet of pump 32 via conduit 35. The liquid in conduit 35 (to which fresh cooking liquor may be added) is pressurized by a pump 32 and passed through conduit 33 and used to slurry chips from feeder 27. The chips held by the screen 12 descend in the digester 11 for further processing.

  The liquid removed from high pressure feeder 27 via conduit 30 and pump 31 is recirculated to chute 26 on high pressure feeder 27 via conduit 36, sand separator 37, conduit 38, in-line drainer 39, and conduit 29. You. The sand separator 37 is a cyclone-type separator for removing sand and debris from the liquid. In-line drainer 39 is a static screening device that removes excess liquid from conduit 38 and stores it in level tank 40 through conduit 39 '. The liquid stored in tank 40 is returned to the top of the digester via conduit 41, pump 42 (ie, make-up liquid pump) and conduit 43. Fresh cooking liquor may be added to conduit 41 or 43.

  FIG. 2 shows another conventional apparatus 110 for feeding chips to a digester. This apparatus uses the process and equipment described in U.S. Pat. No. 5,476,572, U.S. Pat. No. 5,622,598, and U.S. Pat. No. 5,635,025. The equipment and processes described in these U.S. patents are comprehensively sold by Andritz, Inc. under the Lo-Level trademark. 2, the same elements as shown in FIG. 1 are identified by the same reference numerals. Elements that are similar or perform similar functions as shown in FIG. 1 are numbered “1” before the reference numbers shown in FIG.

  As in the apparatus of FIG. 1, the chips 20 are introduced into a steam treatment tank 121, where the chips 20 are exposed to the introduced steam via a conduit 22. Chips are discharged from the steam treatment tank 121 to a metering device 123 and then to a conduit 126 (preferably a chip tube sold by Andritz, Inc.). The cooking liquor is usually introduced into conduit (tube) 126 via conduit 55, similar to conduit 29 of FIG.

  The steam treatment tank 121 is preferably a DIAMONDBACK (registered trademark) steam treatment tank described in U.S. Pat. No. 5,500,083. The pressurized steam processing tank 25 is not required. Instead of discharging the chip and liquid slurry directly to feeder 27, a high pressure slurry pump 51 in conduit 50 is connected via conduit 52, as disclosed in U.S. Pat. No. 5,476,572. It is used to transport chips to the high-pressure feeder 27. Pump 51 is preferably a Hydrostal pump supplied by Wemco or a similar pump supplied by Lawrence company. The chips that have passed through the pump 51 are conveyed to the digester 11 by the high-pressure feeder 27 in the same manner as shown in FIG.

  In addition to using pump 51 to pass slurry to high pressure feeder 27, the apparatus of FIG. 2 does not require pump 31 of FIG. Pump 51 supplies power for liquid to be sent to liquid level tank 53 via high pressure feeder 27, conduit 30, sand separator 37, in-line drainer 39 and conduit 129.

  The function of level tank 53 is disclosed in pending U.S. patent application Ser. No. 08 / 428,302, filed Apr. 25, 1995. The tank 53 ensures that sufficient liquid is supplied to the inlet of the pump 51 via the conduit 54. The tank 53 can also supply liquid to a conduit (tube) 126 via the conduit 55. This liquid tank 53 allows the operator to vary the liquid level in the supply device so that it can be increased to the metering device 123 and even to the storage device 121 if desired. The selection of these features is described in U.S. Pat. No. 5,635,025, issued Dec. 5, 1994, U.S. Patent Application Serial No. 08 / 354,005.

FIG. 3 shows a preferred embodiment of the supply device 210 of the present invention, which is a further simplification of the conventional supply device shown in FIGS.
In the preferred embodiment shown in FIG. 3, the high-pressure carrier 27 of FIGS. 1 and 2 has been eliminated. Instead of conveying the chips to the high pressure feeder 27 by gravity drop onto the chute 26 of FIG. 1 or by the pump 51 of FIG. 2, at least one, preferably two high pressure slurry pumps 251, 251 ' Used to convey the slurry to the inlet of the slurry. Elements in FIG. 3 that are essentially identical to elements shown in FIGS. 1 and 2 are identified by the same reference numerals. Elements similar to or performing similar functions as shown in FIGS. 1 and 2 are numbered “2” before the reference numbers shown in FIGS. 1 and 2.

  Similar to the operating procedure in FIG. 1 or FIG. 2, according to the embodiment in FIG. The chips are preferably introduced by a sealed horizontal conveyor disclosed in pending US patent application Ser. No. 08 / 713,431, filed Sep. 13, 1996. Also, the steam treatment tank 221 is a DIAMONDBACK® steam treatment tank to which steam is added via one or more conduits 22, preferably as described in US Pat. No. 5,500,083. . Steam treatment tank 221 typically includes conventional chip-level monitoring and control devices and pressure relief devices (not shown). The processing tank 221 discharges the chips subjected to the steam treatment to the measuring device 223. As the measuring device 223, as described above, a pocket rotor type device such as a chip meter and a screw type device are exemplified.

  In one embodiment of the invention, metering device 223 discharges chips directly into conduit or chute 226. However, in an alternative embodiment, a pressure isolator, such as a pocket rotor isolator, indicated by a dashed line at 224, for example, a conventional low pressure feeder, is disposed between the metering device 223 and the chute 226. Can be. Without the pressure isolator 224, the pressure in the chute 226 is essentially atmospheric pressure, but with the pressure isolator 224, the pressure in the chute 226 is 6.9-345 kPaG (1-50 psig). ), Preferably from 35 to 175 kPaG (5 to 25 psig), and most preferably from 69 to 138 kPaG (10 to 20 psig). As described above, cooking liquor is added to chute 226 (see arrow 226 'in FIG. 3) and a slurry of chips and liquid is produced in chute 226 having a detectable level (not shown). The slurry in the chute 226 is discharged from the rounded outlet 250 to the inlet of the pump 251. The introduction of the slurry to the inlet of the pump 251 is accomplished by a conduit 254 from the liquid tank 253, as described in U.S. Pat. No. 5,622,598, assigned to U.S. patent application Ser. No. 08 / 428,302. It is usually facilitated by the liquid passing through.

  The pump 251 is preferably a single-blade high pressure screw slurry pump, such as a Hydrostol Pump (registered trademark) from Wemco Pump, Salt Lake City, Utah, USA. The pressure at the inlet to the pump 251 can vary from atmospheric to 345 kPaG (50 psig), depending on whether a pressure isolator 224 is used.

  In the preferred embodiment shown in FIG. 3, the slurry is discharged from the outlet of pump 251 to the inlet of pump 251 '. Pump 251 'is preferably a high-pressure centrifugal slurry pump having the same or a higher pressure rating than first pump 251. If two pumps are used, the pressure obtained at the outlet of the pump 251 'is typically between 150 and 400 psig, i.e., a gauge pressure of 105-281 meters (345-920 feet) of water depth. Preferably, the depth is 140 to 210 meters (460 to 690 feet) at a gauge pressure of 200 to 300 psig (200 to 300 psig). If necessary, the liquid in the slurry in conduit 252 can be increased by liquid sent from tank 253 via conduit 56 and liquid pump 57. Pumps 251 and 251 'are preferably located at least 9.2 meters (30 feet) below the top of the processing vessel, such as a digester, and at least 15.3 meters (50 feet) below the top of the processing vessel. You can also.

  The embodiment shown in FIG. 3 includes two pumps, but only one pump may be a screw pump, or alternatively, three or more pumps may be used in series or in parallel. In these cases, the discharge pressure from one or the last pump is preferably the same as the discharge pressure from the pump 251 '.

  The pressurized and typically heated slurry is discharged from pump 251 'to conduit 234. Conduit 234 passes the slurry to the inlet of continuous digester 11. Excess liquid in the slurry is typically removed by screen 12. Excess liquid is returned to the supply device 210 via conduit 235, but is preferably returned to the liquid tank 253 and sent via conduit 254 into conduit 250 for use in slurrying. The liquid in conduit 235 can be passed through sand separator 237 if desired. The sand separator 237 can be designed for pressurized or non-pressurized operation, depending on the desired mode of operation.

  The prior art apparatus uses a high pressure feeder (reference numeral 27 in FIGS. 1 and 2) and uses the pressure of the liquid returned via conduit 35 as an important part of the slurry from the high pressure feeder 27 to the digester 11. Although used, in contrast, it is not necessary for the operation of the present invention to return the pressurized recirculation conduit 235 to the pumps 251, 251 '. The energy generated by the pressure of the stream in line 235 may be used anywhere in the pulp mill. However, in a preferred embodiment, the pressure created in conduit 235 is used to minimize the energy requirements of pump 251 and pump 251 'as much as possible.

The pressure in the return line 235 is typically about 1.03-2.76 MPaG (150-400 psig), but how this pressure is used depends on the mode of operation of the feeder 210. If the tank 226 is operated in a non-pressurized, ie, essentially atmospheric pressure mode, the pressurized liquid returned to the conduit 235 must be returned to essentially atmospheric pressure before being introduced into the conduit 250. One means for doing this is to use a pressure control valve 58 and a pressure indicator 59 in conduit 235. The opening and closing of the valve 58 is controlled such that a preset reduced pressure is present in the line 235 downstream of the valve 58. In addition, the liquid tank 253 can be designed such that it acts as a “flash tank,” where the hot pressurized liquid in the conduit 235 evaporates rapidly, producing a vapor source in the tank 253. This steam can be used in vessel 221 via conduit 60, among other places. However, in a preferred embodiment, the pressurized liquid in conduit 235 is used, for example, to increase the flow rate from pump 251 'via conduit 61 and pump 62, for example. The pressure in conduit 235 can also be used to increase the flow in conduit 252 between pump 251 and pump 251 ′ via conduit 63, but with pump 64. It may not be used (in some cases a check valve is used instead of or in conjunction with each of the pumps 62, 64). By reusing a portion of the available pressure in line 235, a portion of the energy demand of pump 251 and pump 251 'can be reduced.
Also, the heat of the liquid in line 235 is used to exchange heat with one or more other liquids in the pulp mill that need to be heated.

  Pressurization of pumps 251 and 251 'and transport by these pumps may be performed by conventional eductors, for example, those manufactured by Fox Valve Development Corporation. Alternatively, pumps 251 and 251 'may be used in conjunction with an eductor to increase the pressure at the inlet or outlet of the pump. The eductor can also be used as a means for introducing a liquid into the chip. For example, an eductor is located at or below the outlet of vessel 226, where liquid is first introduced to the chip. The eductor includes a venturi-type orifice in one or more of the conduits 250, 252, 234, into which pressurized liquid vapor is introduced. The pressurized liquid may be obtained from any liquid source, but is preferably obtained from conduit 235 upstream of valve 58. An example of an eductor is shown at 70 in FIG.

  The pump 251 ′ need not be a centrifugal pump, but may be any slurry conveying device that can directly act to pressurize the slurry of chips and liquid and convey it from the outlet of the tank 226 to the inlet of the digester 11. Other forms may be used. For example, solid pumps commonly used in mining can be used, such as double piston solid pumps such as the KOS solid pump sold by Putzmeister, and other similar conventional pumping equipment.

  One of the functions of the conventional high pressure feeder 27 of FIGS. 1 and 2 is to reduce pressure leaks in equipment and transport conduits, such as conduits 34 and 35 in FIG. 1, in the event that any of the supply elements malfunctions or fails. It acts as a shut-off valve to prevent it. In the supply device 210 of the present invention, another means is provided to prevent pressure leakage due to malfunction or failure. For example, FIG. 3 shows a one-way (check) valve 65 in conduit 234 to prevent pressurized flow from flowing back to pump 251 or pump 251 '. In addition, conventional automatic (eg, solenoid operated) isolation valves 66 and 67 are disposed in conduits 234 and 235, respectively, to isolate pressurized conduits 234 and 235 from other portions of supply 210. In one preferred mode of operation, a conventional pressure switch 68 is located in conduit 234 downstream of pump 251 '. Switch 68 is used to monitor the pressure in line 234, and a conventional controller 69 automatically closes valves 66 and 67 when the pressure deviates from a preset value so that the digester can be closed. 11 is automatically isolated from the supply device 210. These valves are automatically closed when the flow direction sensor senses backflow in conduit 234.

  The above-described pressure leak prevention device 65-69 is preferable, but any other device capable of appropriately preventing the serious pressure drop in the digester 11, such as a valve, a sensor, an indicator, an alarm, etc. May be used as the pressure leakage prevention means.

  The feeder 210 is preferably used with a continuous digester 11, but the feeder 210 may comprise another vertically pressurized (usually at least about 1034 kPa or 10 bar gauge) processing vessel having a top inlet, for example, It may be used with an impregnation tank or a batch digester.

  As described above, the present invention has been described in relation to the most practicable and preferable embodiments, but the present invention is not limited to the disclosed embodiments, and the present invention is not limited to various modifications derived from the appended claims. And equivalent technologies.

FIG. 1 shows a typical prior art apparatus for feeding a slurry of comminuted cellulosic fiber material to a continuous digester. FIG. 2 shows another conventional apparatus for feeding a slurry of comminuted cellulosic fiber material to a continuous digester. FIG. 3 shows an apparatus according to an embodiment of the present invention for supplying a slurry of the comminuted cellulosic fiber material to a continuous digester.

Explanation of reference numerals

11 Continuous digester 12, 14 Liquid removal screen 221 Steam treatment tank 223 Measuring device 224 Pressure isolating device 226 Chutes 251, 251 'High-pressure slurry pump

Claims (16)

An apparatus for producing chemical cellulose pulp from comminuted cellulose fiber material,
A steam treatment tank for removing air by steaming the comminuted cellulose fiber material;
A pressurized vertical treatment vessel having an inlet at its top for a slurry of the comminuted cellulosic fibrous material, and having an exit at its bottom; and Including a plurality of high-pressure slurry pumps for pressurizing the slurry of the cellulosic material and transporting the slurry to the inlet of the pressurized vertical processing tank,
An apparatus for producing a chemical cellulose pulp, wherein the plurality of high-pressure slurry pumps include a first screw pump and at least a second pump.   The first screw pump and the second pump are connected in series, an inlet to the first screw pump has an inlet operatively connected to the steam treatment tank, and an outlet of the first screw pump is the The apparatus of claim 1 operatively connected to an inlet of a second pump.   The apparatus of claim 1, wherein the second pump is a high pressure centrifugal slurry pump capable of pumping a slurry having a liquid to solids ratio of 2-10.   The apparatus of claim 1, further comprising a liquid return line from the top of the pressurized vertical processing vessel, wherein the liquid return line is operatively connected to one inlet or outlet of the slurry pump.   5. The apparatus of claim 4, wherein the liquid return line is connected to a pressure reducing device located in the liquid return line and upstream of one of the inlets or outlets of the slurry pump.   The apparatus of claim 5, wherein the pressure reducing device includes a flash tank, and liquid from the flash tank is directed to an inlet to the first screw pump.   The apparatus of claim 5, wherein the pressure reducing device includes a pressure control valve in the liquid return line.   The apparatus according to claim 1, further comprising an eductor operatively connected to one inlet or outlet of the slurry pump. The first screw pump and the second pump are connected in series, and an inlet to the first screw pump has an inlet operatively connected to the steam processing tank,
An outlet of the first screw pump is operatively connected to an inlet of the second pump, the second pump is a high pressure centrifugal pump, and the second pump has a higher pressure rating than the first pump. The apparatus of claim 1, wherein the pressurized vertical processing vessel comprises a continuous digester.   The apparatus of claim 1, wherein the first screw pump is located at least 30 feet below the top of the steam treatment tank.   The apparatus of claim 1, wherein the first screw pump is located at least 30 feet below the top of the steam treatment tank.   The apparatus of claim 1, wherein the first screw pump is located at least 30 feet below the plurality of high pressure slurry pumps. (A) removing the air by steaming the comminuted cellulose fiber material;
(B) slurrying the comminuted cellulosic fibrous material with a cooking liquor to produce a slurry of the liquid and the comminuted cellulosic fibrous material; and (c) subjecting the slurry to a pressure of at least about 517 kPa below the top of the treatment vessel at a gauge pressure of 5 bar) and transporting the pressurized comminuted cellulosic fibrous material to the top of the treatment vessel, wherein the pressurizing step is performed on the slurry using one or more high pressure slurry pumps. Supplying the comminuted cellulose fiber material to the top of the treatment tank. (D) returning the liquid separated from the slurry at the top of the processing tank to at least one pump; and (e) sensing the pressure of the slurry while being transported to the top of the processing tank, and setting the sensed pressure to a preset value. 14. The method of claim 13, further comprising the step of closing the flow of slurry to the top of the processing tank and the return of liquid from the top of the processing tank when the value falls below the set value. 15. The method of claim 14, further comprising: (f) flashing the liquid returned in performing step (d) to produce steam and using the steam in performing step (a). . (A) introducing an untreated chip into the first tank;
(B) introducing a slurried liquid into the first tank to produce a slurry of the comminuted cellulose fiber material and the liquid;
(C) discharging the slurry from the first tank to the inlet of at least one pressurized transfer device; and (d) pressing the slurry in the pressurized slurry forming device and transferring the slurry to the processing tank. A method of conveying a comminuted cellulosic fiber material to a pulping process.

Images