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    • 专利摘要:
    METHOD AND APPARATUS TO PRODUCE PULP USING PREHYDROLYSIS AND KRAFT COOKING. The present invention relates to a pulp cooking system which includes: a cellulosic material feeding system, a pre-hydrolysis reactor reservoir and a Kraft cooking reactor reservoir. The feed material system includes a vaporization chip compartment (10) and a high pressure transfer device (12). The pre-hydrolysis reactor reservoir keeps the feed material in mildly acidic conditions and allows the hydrolyzate to be extracted through sieves (60) below a hydrolysis zone (56) in the reservoir. The washing zone (66) is below the sieves and allows the washing liquid to flow through the feed material in a transverse cross-flow direction. The washing liquid and the hydrolyzate removed from the feed material are extracted from the washing zone through the sieves (60). The feed material is kept in a mildly acidic condition through the pre-hydrolysis reactor reservoir until the material enters the Kraft cooking reservoir where the feed material is treated with alkaline cooking liquors.
    公开号:BR112013021316B1
    申请号:R112013021316-7
    申请日:2012-02-13
    公开日:2020-10-27
    发明作者:Aaron T. Leavitt；Jussi Pakarinen；Brian F. Greenwood
    申请人:Andritz Inc.；
    IPC主号:
    专利说明:

    CROSSED RELATED ORDER
    [0001] This order claims the benefit of the US order. No. 13 / 363,680 filed on February 1, 2012 and the provisional US application. No. 61 / 445,253 filed on February 22, 2011, both of which are incorporated herein by reference. BACKGROUND OF THE INVENTION
    [0002] This invention relates in general to the dissolution of pulp through cooking and particularly with pre-hydrolysis and Kraft cooking of wood chips.
    [0003] The hydrolysis of crushed cellulosic fiber feed material, such as wood chips, prior to Kraft cooking is described in US Patents. 3,380,883 and 4,436,586, and in Blom et al, "Development of the Alva Prehydrolysis Process, Part Two: Mill Scale Application," pp. 409-416 TAPPI Proceedings, 1981 Pulping Conference. Prehydrolysis is typically used to dissolve the pulp for use in forming artificial silk or plastic.
    [0004] Pseudolignins formed during the hydrolysis of wood can coat wood chips and reactor surfaces and other equipment exposed to hydrolyzed cellulosic fiber feed material. Pseudolignins are formed through the condensation and polymerization of reactive by-products from the hydrolysis of the cellulosic fiber feed material. These reactive components include dissolved hemicellulose and other wood compounds. Lignin fragments that dissolve in hydrolysis can also coat wood chips and the surfaces of the prehydrolysis reactor and other equipment. Pseudolignins and lignin fragments tend to settle on the surfaces of chips and equipment to the maximum degree when in an acidic environment; as typically occurs in prehydrolysis. The complex organic molecules dissolved in the pseudolignins and dissolved lignins can coat the chips and the pores of the block in the chips. The pores must be opened to allow an alkali to penetrate during the Kraft stage of the process. The shapes of pseudolignins and lignins dissolved in the equipment can block the flow passages for the cellulosic feed material, interfere with the rotation of the moving parts and otherwise interfere with the equipment's operation. SUMMARY OF THE INVENTION
    [0005] Methods and systems for dissolving pulp cooking have been devised, which reduce the formation of pseudolignins and lignin fragments on wood chips and equipment and intensify the control of the flow of feed material through pre -hydrolysis and Kraft cooking reactors.
    [0006] The pulp cooking system includes a pre-hydrolysis reservoir and a transfer system that has multiple extraction points to remove products from hydrolysis when products are formed in the reservoir and transfer system. Current washing liquids, such as water, can be added at various locations in the reservoir and transfer system. For example, a central tube, which extends vertically into the pre-hydrolysis reservoir, discharges water or a washing liquid into the downward flow of cellulosic feed material through the reservoir. Extraction sieves arranged at one or more elevations over the pre-hydrolysis reservoir extract the pseudolignins when they are formed in the reservoir. In the transfer system, extraction points can be provided using an aligned drain. The washing liquid is added via dilution nozzles arranged at one or more locations in the material flow through the transfer system.
    [0007] The chip feeding device for the pulp cooking system can be a chip compartment having converging sides, such as the Diamondback® chip compartment sold by the Andritz Group, and steam injection to heat the feed material. A chip pump system, such as the TurboFeed® system sold by the Andritz Group, provides a stable and accurate volume of feed material to the prehydrolysis reactor.
    [0008] Reducing the pH of cellulosic feed material, for example wood chips, which moves through the feed and chip transfer devices can accelerate the onset of the hydrolysis reaction. One approach to reducing the pH is to add hydrolysate extracted from the lower parts of the prehydrolysis reactor to the feed material in one or more of the chip feed system, transfer system and the upper regions of the reactor. The hydrolyzate at the bottom of the prehydrolysis reactor has a relatively low pH and can be used to lower the pH of the feed material in the upstream parts of the reservoir and feed and transfer devices.
    [0009] The washing water and the filtered liquid tend to have different pH levels than the feed material. The washing water and the filtered liquid can be added to the feed and chip transfer systems to adjust the pH and adjust the liquid liquor ratio to relative way of the feed material in the feed and transport devices and in the upper regions of the pre reactor. -hydrolysis. Heat can be recovered from the hydrolyzate extracted in the prehydrolysis reactor to heat the wash water and the filtrate to be added to the prehydrolysis reservoir.
    [00010] The pH level of the feed material in the prehydrolysis reactor can be manipulated, for example, reduced, by adding washing water, low pH hydrolyzate and filtered at one or more elevations of the reactor. The low pH hydrolyzate can be extracted from the lowest elevations in the reactor and circulated back into the reactor at a higher region of the reactor. Circulation circuits within the reservoir and a central tube discharge having one or more elevations at which the fluid is discharged can be used to controllably add low pH liquid to the reactor.
    [00011] The wash zone (s) at the bottom of the reservoir may have the wash liquid flow in countercurrent or concurrent directions to the downward flow of the feed material in the pre reactor reservoir. -hydrolysis. If the injection of the washing liquid has a neutral pH, mild alkaline or a pH that is less acidic than the pH in the hydrolysis zone, the washing liquid will tend to reduce the acidity of the feed material in the lower region of the pre reactor. -hydrolysis. The wash liquid can have an alkaline pH, especially if the wash water is mixed with brown raw material filtrate or sodium hydroxide and used in a counter current or a displacement wash zone at a lower elevation of the pre-reactor. hydrolysis.
    [00012] The washing liquid can also be fortified with a bisulfite compound or other additive. The fortified washing liquid can be used in a counterflow or displacement washing zone at a lower elevation of the prehydrolysis reactor. The addition of a bisulfite compound or other additive to the washing liquid can reduce the tendency of dissolved lignin or pseudolignin in the washing area of the pre-hydrolysis reactor and transfer devices to precipitate on the surfaces of the chips and equipment.
    [00013] The pH of the chip feed material that is discharged from the bottom of the pre-hydrolysis reactor can be controlled, for example, reduced or increased, by adding washing water / pH-adjusted filtrate through a nozzle at the bottom of the reservoir. The amount of pseudolignin formation and lignin deposits can be reduced by controlling the pH of the feed material, such as by maintaining acidity levels at a uniform level when the feed material flows through the feed and transport devices of chips, the pre-hydrolysis reactor and the transport ducts from the pre-hydrolysis reactor to a Kraft digester. The desired pH level for the feed material can be predetermined based on the type of feed material, pressure and temperature in the prehydrolysis reactor and other conditions. A person of practical skill in chemistry and in the operation of Kraft pulping systems will understand how to determine the desired pH level of the chip feed material.
    [00014] The transfer liquid can also be fortified with the bisulfite compound or other additives before being added to the feed material at or near the discharge from the pre-hydrolysis reactor reservoir. The bisulfite compound or other additives can be selected to reduce the tendency of dissolved lignin or pseudolignin to precipitate on the surfaces of the chips and transfer devices.
    [00015] When the feed material enters the Kraft digester, such as through an inverted upper separator, in an operating mode, the feed material remains acidic without the high pH regions until the feed material chips enter the digester reservoir. The white liquid substance (such as sodium hydroxide and sodium sulfide solution) can be added to the feed material in the upper separator or sprayed in the upper part of the digester tank. In another mode of operation, white liquor can be added to the transfer circulation and the chips raised to a high pH during transfer between the reservoirs.
    [00016] A method has been devised to produce pulp using a feed system, a pre-hydrolysis reactor reservoir and a Kraft cooking reservoir including: vaporizing fibrous cellulosic organic feed material in a feed system; adding to the feed material the wash filtrate extracted from the pre-hydrolysis reactor reservoir before the feed material enters the pre-hydrolysis reactor reservoir; pressurize the feed material from the chip feed system on a high pressure transfer device before the feed material enters the pre-hydrolysis reservoir; transferring the pressurized feed material to an upper inlet in the pre-hydrolysis reactor reservoir; subjecting the feed material to a hydrolysis reaction in a hydrolysis zone in the pre-hydrolysis reactor reservoir, where the hydrolyzate is a by-product generated by the hydrolysis reaction; extract the hydrolyzate with the extracted wash filtrate through a sieve in the pre-hydrolysis reactor reservoir, where the sieve is adjacent to a lower part of the hydrolysis zone; adding a washing liquid to a lower region of a washing zone in the pre-hydrolysis reactor reservoir; when the feed material flows down past the sieve and through the washing zone, washing the feed material with the washing liquid flows up through the wash zone to the sieve; unload the washed feed material from the pre-hydrolysis reactor reservoir and transport the washed feed material to an upper inlet to the Kraft cooking reservoir; change the pH of the washed feed material to alkaline once the feed material is in the Kraft cooking vessel, and Kraft cooking of the washed food material in the Kraft cooking vessel to produce the pulp.
    [00017] A method has been devised for the production of pulp using a feed system, a pre-hydrolysis reactor reservoir and Kraft cooking reservoir, the method comprising: vaporizing the cellulosic fibrous organic feed material into a feed system material; adding the wash filtrate extracted from the pre-hydrolysis reactor reservoir to the feed material before the feed material enters the pre-hydrolysis reactor reservoir; pressurize the feed material from the chip feed system on a high pressure transfer device before the feed material enters the prehydrolysis reservoir and transfer the pressurized feed material to an inlet above the reactor reservoir. prehydrolysis; subjecting the feed material to a hydrolysis reaction in a hydrolysis zone in the pre-hydrolysis reactor reservoir, where the hydrolyzate is generated by the hydrolysis reaction; extracting the hydrolyzate through a sieve in the pre-hydrolysis reactor reservoir, where the sieve is adjacent to a lower part of the hydrolysis zone; adding a washing liquid to a washing zone in the pre-hydrolysis reactor reservoir; when the feed material flows down past the sieve and through the washing zone, washing the feed material with the washing liquid flows up through the wash zone to the sieve; unload the washed feed material from the pre-hydrolysis reactor reservoir and transport the washed feed material to an upper inlet to the Kraft cooking reservoir; and changing the pH of the washed feed material to alkaline once the feed material is in the Kraft cooking vessel, and the Kraft cooking of the washed food material in the Kraft cooking vessel for pulp production. The method steps can be performed contentiously and simultaneously when the feed material flows through the feed system, the pre-hydrolysis reactor reservoir and the Kraft cooking reservoir.
    [00018] The pulp can be discharged from the Kraft cooking tank into a blowing tank and from the blowing tank to a brown raw material washer. The step of pressurizing the feed material includes pumping the feed material through at least one centrifugal pump, which comprises the high pressure transfer device.
    [00019] The step of adding the washing liquid may include injecting the washing liquid from a central coaxial tube to the pre-hydrolysis reactor reservoir and having a discharge port in the lower region of the washing zone.
    [00020] The hydrolysis reaction can be an auto-hydrolysis reaction and a temperature in the feed material is between 150 degrees and 160 degrees Celsius or between 140 degrees and 175 degrees Celsius. The pH of the pressurized feed material in the hydrolysis zone can be maintained at a pH between 3 and 5 or 4. The washing liquid can enter the wash zone at a temperature of at least 10 degrees Celsius below a hydrolysis temperature. in the hydrolysis zone and the washing liquid can include a bisulfite compound.
    [00021] The wash filtrate or liquor extracted from a first elevation of the pre-hydrolysis reactor reservoir can be reintroduced into the pre-hydrolysis reactor reservoir at a second elevation that is above the first elevation. Alkaline white liquor is added to the feed material when the feed material is in an upper region of the Kraft cooking vessel.
    [00022] A method has been devised for pulping a crushed cellulosic fibrous organic feed material into a feed system, a pre-hydrolysis reactor reservoir and Kraft cooking reservoir, the method comprising: vaporization and addition of the filtrate from washing in the feed material when the feed material flows continuously through the material feed system; the pressurization of the feed material flowing from the chip feed system in a high pressure transfer device; the movement of the pressurized feed material into the pre-hydrolysis reactor reservoir; subjecting the feed material to a hydrolysis reaction in a hydrolysis zone in the pre-hydrolysis reactor reservoir; the extraction of the hydrolyzate formed in the hydrolysis zone and the wash filtrate through a sieve close to a lower region of the hydrolysis zone in the pre-hydrolysis reactor reservoir, the addition of a washing liquid to a wash zone in the reservoir the pre-hydrolysis reactor, where the wash zone is below the hydrolysis zone in the pre-hydrolysis reactor; moving the feed material continuously down through the hydrolysis zone and the wash zone of the pre-hydrolysis reactor reservoir; moving the washing liquid continuously upwards through the washing zone to the sieve; the discharge of the feed material from a lower outlet of the pre-hydrolysis reactor reservoir, with the lower outlet close to a lower part of the washing zone; moving the unloaded feed material into the Kraft cooking tank; and adjusting the pH of the feed material discharged to alkaline, while the feed material is in the Kraft cooking vessel, and the Kraft cooking of the feeding material in the Kraft cooking vessel to produce the pulp.
    [00023] A system was designed to produce pulp from cellulosic fibrous organic feed material: a material feed system having an inlet to receive the feed material, a steam inlet to receive steam to be injected into the feed material. feeding in the feeding system, a filtrate inlet and an outlet for the feeding material; a high pressure transfer device including an inlet in fluid communication with the outlet of the material feeding system; a pre-hydrolysis reactor reservoir having a high-pressure inlet in fluid communication with a high-pressure outlet of the high-pressure transfer device, in which the pre-hydrolysis reactor includes an interior maintained at a temperature and pressure to promote hydrolysis of the feed material in the reactor; an extraction sieve at the bottom of the prehydrolysis reactor, including a filter screen adjacent to the interior of the prehydrolysis and a filtrate outlet on one side of the filter screen opposite to the interior, where the filtrate outlet is coupled to the filtrate inlet of the material feeding system in such a way that the filtrate from the pre-hydrolysis reactor flows into the filtrate inlet, and a Kraft cooking vessel having a high pressure inlet coupled with a high discharge outlet pressure of the pre-hydrolysis reactor feed material in such a way that the feed material flows from the pre-hydrolysis reactor reservoir to the inlet of the Kraft cooking vessel, where the interior of the Kraft cooking vessel holds the feed material in an alkaline environment, and the Kraft cooking vessel has a high pressure discharge outlet from which the feed material is discharged as pulp. BRIEF DESCRIPTION OF THE DRAWINGS
    [00024] FIGURE 1 is a process flow diagram of a Kraft cooking system for dissolving the pulp.
    [00025] FIGURE 2 is an enlarged view of the pre-hydrolysis reactor reservoir shown in FIGURE 1. DETAILED DESCRIPTION OF THE INVENTION
    [00026] FIGURE 1 is a process flow diagram of a pulp dissolution system using pre-hydrolysis and Kraft cooking. The system includes a vaporization chip compartment 10, a high pressure conveying device 12, a pressurized pre-hydrolysis reactor reservoir 14, a pressurized Kraft cooking reactor reservoir 16 and a blowing tank 18. Cellulosic feed can flow continuously through the system. The amount of feed material flowing through the system depends on the size of the system, and this amount can be in excess of 500 to 3500 tons per day. The system can be used to dissolve the pulp for the production, for example, of artificial silk, plastics and biofuels, such as ethanol.
    [00027] The cellulosic feed material 20 is fed by a chip feeder 22 to an upper inlet of the chip compartment 10. The cellulosic feed material can be wood chips, biomass, crushed lignocellulosic material or other organic fibrous material. The chip feeder 22 can be a helical conveyor or tube that provides an air block to seal the inner chamber of the chip compartment 10 from the atmosphere. The chip feeder may include a measuring screw to regulate the amount of feed material that continuously enters the top entry of the chip compartment.
    [00028] The chip compartment 10 can be a vertical reservoir with a lower discharge 24. A hole 26 in the upper part of the chip compartment 10 allows steam to escape from the chip compartment into a steam or vapor recovery system 28 The addition of steam 32 in the chip compartment takes into account the pre-vaporization of the chips in the chip compartment. Pre-vaporization is believed to initiate hydrolysis and release organic acids from the feed material. These organic acids tend to be slightly acidic and thus help to establish a slightly acidic environment for the feed material.
    [00029] The chip compartment 10 may include an upper chamber 30 having a circular or elliptical cross section and a diameter, for example, of about 10 to 15 feet (3 to 5 meters). The height of the upper chamber can be half to two thirds of the total height of the chip compartment. Low pressure steam 32, for example, from 68.947 kPa to 137.895 kPaW at 20 psig, can be added to a lower region of the upper chamber of the chip compartment. The steam heats the feed material in the chip compartment to a temperature, for example, around 100 degrees Celsius.
    [00030] The lower chamber 34 of the chip compartment has a continuous upper region with the lower part of the upper chamber 30. The geometry, for example, cross-sectional geometry, of the lower chamber 34 can have an open upper part in substantially cross-section circular and an open lower part in substantially rectangular cross-section 24. The lower chamber may have opposite side walls that are not vertical and gradually conical planar walls. Between the opposite planar side walls, there are curved opposite side walls in connection with the planar side walls. The planar side walls can each be generally triangular in plan view. These planar side walls can be arranged vertically in a diamond shape. The Diamondback® chip compartment sold by Andritz Group is an example of the chip compartment described here.
    [00031] The retention period of the feed material in the chip compartment 10 can be relatively short, such as 15 or 25 minutes or longer. The feed material moves from the discharge from the bottom 24 of the chip compartment to a generally horizontal helical conveyor 36, such as a two-propeller conveyor, which includes a helical propeller in a cylindrical support. The helical conveyor 36 can be oriented at a slight inclination such as not more than ten degrees. The inclined helical conveyor is at an upper elevation at the bottom discharge 24 and at a lower elevation at the end of the helical conveyor that connects to a vertical chip tube 38.
    [00032] The chip tube is at least partially filled with liquid, such as hot water 50 and the liquid extracted from the inverted upper separator 42 of the prehydrolysis reservoir 14. The liquid is temporarily stored in a tank 40 and flows through from the conduit line 41 to the chip tube 38 under the hydraulic pressure created in the tank 40.
    [00033] The chip tube 38 can be filled with feed material, hot water and other liquids. The hydraulic pressure at the bottom of the chip tube ensures that the feed material is introduced into the inlet of the high pressure transport device 12. Hot water and other liquids can have a neutral or slightly acidic pH. The addition of hot water and other liquids to the feed material in the chip tube can reduce the total pH of the mixture and thus reduce the tendency to have a strongly acidic pH in the upper region of the pre-hydrolysis reactor reservoir 14.
    [00034] The high pressure in the conveying device 12 provides the force to move the feed material up to the upper separator 42 at the top of the prehydrolysis reactor 14 and to increase the feed material pressure to substantially above atmospheric pressure . The conveying device 12 can be one or more centrifugal pumps arranged in series, such as the TurboFeed® sold by the Andritz Group. The transport device can also be a portable lock rotor. The feed material and liquid move from the high pressure transport device 12 through line 44 to the inverted upper separator 42 in an upper region of the pre-hydrolysis reactor reservoir 12.
    [00035] In the chip compartment and elsewhere in the feed system, the pH of the feed material can be controlled by extracting liquid acid liquor from the feed material through an in-line drain, as in mounting the discharge into the feed compartment shavings and the shavings tube. In addition, the pH can be kept mildly acidic by adding the neutral washing liquid (or washing liquid with a bisulfite compound) through the dilution nozzles arranged in a lower area of the chip compartment and in the lower part of the shavings.
    [00036] The retention period of the feed material in the reservoir of the pre-hydrolysis reactor can be more than one hour, such as 100 minutes. The pre-hydrolysis reactor reservoir 14 is shown more clearly in FIGURE 2. The reservoir 14 can be a pressurized vapor phase reactor reservoir having a vertical or inclined orientation, and a height or length in excess of 20 meters. Alternatively, reservoir 14 can be a hydraulic reservoir having a heating circulation flow to heat the feed material to a desired prehydrolysis temperature.
    [00037] The inverted upper separator 42 is mounted on the upper region 45 of the interior of the reservoir 14. The upper region 45 can be a vapor phase region. When the feed material flows to the bottom of the upper separator 42, a helical conveyor 46 moves the material through the upper part of the separator. The feed material is discharged from the upper part of the upper separator 42, and falls through the vapor phase to an upper surface 48 of the liquid column and chips in the reservoir 14.
    [00038] The liquor (liquid) can be extracted in the upper separator of the feed material through a sieve around the helical conveyor 46 and into a line 47 that transports the extracted liquor through a heat exchanger 48 (Fig. 1) to tank 40 by the high pressure transport device. The ratio of liquor to chips (liquor to the feed material) tends to be higher for transport than in the pre-hydrolysis reactor reservoir 14. Consequently, a part of the liquid extracted from the inverted upper separator 42 can be added to the feed material in the chip tube 36.
    [00039] Medium pressure steam 54, for example, having from 1,241 MPa to 1,378 MPa (180 to 200 psig) and a neutral pH level, can be added when the feed material enters the prehydrolysis reservoir 14, such as while the feed material is in the upper separator or when the feed material falls through the steam phase region 44. Medium pressure steam or compressed air 54 (or both and an inert gas) is added at the top of the reservoir prehydrolysis 14 to create a pressure and temperature environment in the reservoir to promote hydrolysis. The pre-hydrolysis reactor reservoir 14 can be controlled based on both the pressure and the temperature of the reservoir. Pressure control can be through the use of a controlled flow of steam or air 54. The temperature of the steam can be approximately 170 degrees Celsius to raise the temperature of the feed material in reservoir 14 above the self-hydrolysis temperature that can be above 140 degrees Celsius, such as 150 or 165 degrees Celsius.
    [00040] After reaching the surface of the chip and liquor column 48 in the prehydrolysis reservoir, the feed material gradually flows down through the prehydrolysis reactor reservoir 14. As the feed material moves into down through the reservoir, new feed material and liquor liquid are continuously added to surface 48 from the upper separator. The column of chips and liquor in the reservoir is maintained at a pressure and temperature to promote hydrolysis. The temperature and pressure in the reservoir can be monitored using sensors.
    [00041] Hydrolysis occurs in a hydrolysis zone 56 of the pre-hydrolysis reactor reservoir 14, where the temperature is maintained at or above the normal hydrolysis temperature. By controlling the temperature of the feed material in the zone of 56, for example, between 140 and 175 degrees Celsius, self-hydrolysis will occur due to the organic acids released from the feed material. As an alternative to self-hydrolysis, the hydrolysis temperature in the hydrolysis zone can be below 150 degrees Celsius, such as between 150 to 120 degrees Celsius, if mild acids are added to the feed material in the prehydrolysis. Mild acids can be the acid concentration between 0.2 percent and 0.5 percent H2SO4 or equivalent.
    [00042] The feed material and the liquor flow simultaneously down through the hydrolysis zone 56. The double down arrows in Figure 2 shown in container 14 illustrate the simultaneous flow.
    [00043] Hydrolyzate 58, for example, pseudolignins, lignin fragments and hemicellulose, is a product of hydrolysis. The hydrolyzate is formed in the hydrolysis zone 56 and extracted through sieves 60 just below the hydrolysis zone. The sieve extracts the hydrolyzate, the liquor and the washing liquid in the reservoir at the elevation of the sieves 60. The sieves 60 extract the hydrolyzate before the compounds in the hydrolyzate, with a tendency to condense and precipitate, cover the pores of the and accumulate on the internal surfaces of the reservoir 14 and other equipment.
    [00044] The hydrolyzate can be recovered by extracting the heat from the hydrolyzate to provide thermal energy for the hot water used for washing the feed material in the prehydrolysis reactor, and for other processing. For example, the hydrolyzate can be used to form biofuels such as ethanol, or it can be processed to produce chemicals such as furfuraldehyde.
    [00045] The extracted liquor, including the hydrolyzate, can be pumped 62 through line 64 to a central tube 65 coaxially mounted inside the reservoir 14. The central tube 65 discharges the extracted liquor at a higher elevation of the hydrolysis zone to control the pH level in zone 56, such as a pH of 4 or 3.5, or between pH 3 and 4, and promote a uniformly smooth acidic pH level throughout zone 56. The extracted liquor can be added in the hydrolysis zone 56 at various elevations throughout the zone, in particular for the upper regions of the zone. The hydrolysis zone can vary in height and can be from half to two thirds of the height of the reservoir 14.
    [00046] A wash zone 66 in the pre-hydrolysis reactor reservoir 14 is below the sieves 60 and extends below the discharge assembly 68. The wash zone can be one third lower or less than the height of the reservoir 14 Hot water 50 or another pH neutral washing liquid is added to the bottom of the washing zone 66 via nozzles 70 mounted on the reservoir wall 14 or via a lower outlet 67 of the central tube 65. The central tube can have an internal vertical passage for the washing liquid and another passage for the extracted liquor.
    [00047] The hot water 50 can be heated by a heat exchanger 48 with the heat recovered by a part of the extracted hydrolyzate 58 which is not recirculated back to the pre-hydrolysis reservoir 14. The temperature of the hot water is below hydrolysis temperature in the hydrolysis zone, such as a temperature between 110 to 160 degrees Celsius. Hot water can flow upwards through the washing zone 66 in a direction countercurrent to the downward flow of the feed material. Countercurrent flows increase thermal efficiency in the wash zone and reduce water and steam consumption in the wash zone. When the hot water flows upwards through the washing zone, the hydrolyzate is dragged with the water and is extracted from the reservoir 14 with the water through the sieves 60.
    [00048] Hot water can be fortified with a bisulfite compound or other additives before being added as a washing liquid to the pre-hydrolysis reactor reservoir. The bisulfite compound or other additive must reduce the tendency of dissolved lignin or pseudolignin that flows with the feed material in the wash zone to precipitate on the surfaces of the chips and the pre-hydrolysis reactor reservoir.
    [00049] The temperature of the feed material in the washing zone 66 may be below the hydrolysis temperature, which corresponds to the temperature in the hydrolysis zone. The temperature of the feed material in the wash zone can be 10 to 40 degrees Celsius below the hydrolysis temperature. Reducing the temperature of the feed material in the washing zone and the extraction of acids from the feed material in the sieves 60 can suppress and interrupt the hydrolysis. The interruption of hydrolysis in the wash zone must also prevent the formation of hydrolyzate when the feed material flows through the wash zone.
    [00050] When the feed material reaches the bottom of the pre-hydrolysis reactor reservoir 14, the material enters the discharge assembly 68 where the dilution liquor 72 extracted from the Kraft cooking reservoir, for example, a reservoir pressurized continuous digester, is added to increase the ratio of liquor to feed material and thus assist in transporting the feed material through line 74 to an inverted upper separator 76 in the upper region of the cooking vessel 16. The dilution liquor can be fortified with a bisulfite compound or other additives before being added to the feed material at or near the pre-hydrolysis reactor reservoir discharge. The bisulfite compound or other additive must reduce the tendency of dissolved lignin or pseudolignin that flows with the feed material to precipitate on the surfaces of the chips and transfer devices.
    [00051] The retention period of the feed material in the cooking vessel 16 can be around two hours. The feed material is in an alkaline condition, such as at or near a pH of 13, for example, from 12 to 14, and maintained at a higher temperature than in the prehydrolysis reservoir such as at a temperature of 170 degrees Celsius. In addition, and, for example, the feed material in the cooking vessel can be kept in a range of 140 degrees and 175 degrees Celsius, or 150 degrees and 160 degrees Celsius, depending on the holding time in the vessel, the alkali concentration in the cooking vessel, and the desired lignin content of the final pulp product from the cooking vessel 16.
    [00052] In an operating mode, the feed material is in a slightly acidic condition when it moves from the pre-hydrolysis reactor reservoir 14 to the cooking reservoir 16. The acidic condition of the feed material is maintained when the feed material enters the inverted upper separator 76. The feeding material becomes alkaline by adding alkaline white liquor 78 through line 80 in the upper separator or in the upper region of the cooking vessel. The addition of white liquor can be controlled to avoid having substantial amounts of white liquor extracted through separator 76 and flowing through line 72 for the discharge assembly of the pre-hydrolysis reactor reservoir 14. Excessive amounts of white liquor being added prematurely to the feed material can cause the feed material to become alkaline before entering the cooking tank 16. In another mode of operation, the transfer circulation becomes alkaline by adding white liquor and the pH is high when the chips are transported from the pre-hydrolysis reactor reservoir 14 to the cooking reservoir 16.
    [00053] The temperature in the cooking vessel 16 is high and controlled by the addition of medium pressure steam 54, and possibly air or an inert gas. The cooking vessel may be a steam or hydraulic phase vessel operated at a pressure in equilibrium with the pressure in the pre-hydrolysis reactor vessel 14. The pressure at the bottom of the pre-hydrolysis reactor vessel is a combination of average steam pressure and the hydraulic pressure of the chip column and liquid in the reservoir 14. This combined pressure is greater than the pressure in the upper part of the cooking reservoir, which can be in the pressure of steam in medium pressure 54. The differential of pressure between the bottom of the pre-hydrolysis reactor tank and the top of the cooking tank moves the feed material between line 74. In addition, and where a digester cooking tank is used, a heating circulation can be used to heat the feed material to the desired cooking temperature.
    [00054] The cooking vessel 16 can have multiple zones of concurrent and countercurrent flow. An upper cooking zone 82 may have a concurrent flow of feed material and liquor. A liquid black liquor portion is extracted through sieves 84 at the bottom of the upper cooking zone. The extracted black liquor flows through line 86 to supply thermal energy to an annealing boiler 88. The clean low pressure steam generated in the rewarm boiler flows through line 90 to supply thermal energy to the chip compartment 10. The condensate 91 from the annealing boiler can be used as hot water 50. Black liquor flows from the annealing boiler to a black liquor filter 89. The filtered liquor flows into the weak black liquor tanks for further processing in the black liquor evaporation system . Waste from the black liquor filter, which contains fibers and fragments of uncooked raw material, flows into the blowing tank. Other heat recovery systems that recover the heat from the hot black liquor, such as scintillation tanks and heat exchangers, can be used with or as a replacement for the annealing boiler 88.
    [00055] In an intermediate cooking zone 92, the feed material continues to move downward and a countercurrent flow of black liquor flows upward through zone 92, as indicated by the opposite arrows. The additional liquor is extracted through sieves 94. The black liquor extracted from sieves 94 is combined with the black liquor extracted from a lower sieve 96 which flows through line 98. White liquor 78 and washing liquor 108 (line 111) can be added to the combined black liquor flow through line 100. The combined flows of black liquor and white liquor are circulated back to the cooking vessel through a central tube 102 that adds the combined fluid to or below the sieves 94.
    [00056] The rate at which the combined flow is added through the central tube 102 and the rates at which the liquor is extracted through sieves 84 and 92 are adjusted in such a way that the liquor flows upwards through the intermediate cooking zone and down through a lower cooking zone 104. The lower cooking zone may be one third, half or more of the vertical length of the digester tank 16.
    [00057] The washing zone 106 at the bottom of the cooking vessel washes the feed material to extract the black liquor. The washing liquor 108 flows through a washing line 110 to the lower region of the washing zone and through a central tube 112 to the washing zone. When the washing liquor flows upwards through the washing zone, the black liquor and other chemicals in the feed material are entrained, flow upwards and are extracted through the 96 sieve.
    [00058] A lower discharge assembly 114 discharges the washed feed material from the cooking vessel via line 116 to the blowing tank 18. The pressure of the feeding material is released in the blowing tank. From the discharge 118 of the blowing tank, the feed material, which is now the dissolved pulp, is pumped for further processing such as a brown raw material washer 120.
    [00059] The process described here for the production of dissolved pulp using pre-hydrolysis and Kraft cooking maintains a slightly acidic pH for pre-hydrolysis, extracts the hydrolyzate immediately after its generation, and guarantees the rapid transition to alkaline conditions in the cooking tank.
    [00060] Although the invention has been described in connection with what is presently considered to be the most practical and preferred modality, it should be understood that the invention should not be limited to the disclosed modality, but on the contrary, it is intended to cover the various modifications and equivalent provisions included within the spirit and scope of the appended claims.
    权利要求:
    Claims (16)
    [0001]
    1. Method for pulping a crushed cellulosic fibrous organic feed material (20) in a feed system (22, 10), a pre-hydrolysis reactor reservoir (14) and a Kraft cooking reservoir (16), the method characterized by the fact that it comprises the steps of: (a) vaporizing and adding washing filtrate to the feed material (20) when the feed material (20) flows continuously through the material feed system ( 22, 10); (b) pressurizing the feed material (20) flowing from the material feed system (22, 10) in a high pressure transfer device (12); (c) moving the pressurized feed material (20) into the pre-hydrolysis reactor reservoir (14); (d) subjecting the feed material (20) to a hydrolysis reaction in a hydrolysis zone (56) in the pre-hydrolysis reactor reservoir (14), in which an acidic pH level is maintained throughout the hydrolysis (56), and wherein the feed material (20) and liquor flow simultaneously down through the hydrolysis zone (56); (e) extract hydrolyzate (58) formed in the hydrolysis zone (56) and in the wash filtrate through a sieve (60) located in a first elevation of the pre-hydrolysis reactor reservoir (14) close to a lower region of the hydrolysis zone (56) in the pre-hydrolysis reactor reservoir (14); (f) reintroducing part of the hydrolyzate (58) extracted into the pre-hydrolysis reactor reservoir (14) at a second elevation which is above the first elevation, in order to lower the pH of the feed material (20) in the upstream parts of the pre-hydrolysis reactor reservoir (14), and promoting a uniformly mild acid pH level along the hydrolysis zone (56); (g) adding a washing liquid to a washing zone in the pre-hydrolysis reactor reservoir (14), where the washing zone is below the hydrolysis zone in the pre-hydrolysis reactor (14); (h) moving the feed material (20) continuously down through the hydrolysis zone (56) and the wash zone of the pre-hydrolysis reactor reservoir (14); and moving the washing liquid continuously upwards through the washing zone to the sieve (60); (i) discharge the feed material (20) from the pre-hydrolysis reactor (14); (k) moving the unloaded feed material (20) into the Kraft cooking vessel (16); (l) adjust the pH of the feed material (20) discharged to alkaline, while the feed material (20) is in the Kraft cooking vessel (16), and (m) cooking the feeding material (20) in the cooking vessel Kraft cooking (16) to produce the pulp.
    [0002]
    2. Method, according to claim 1, characterized by the fact that: the washing filtrate added to the feed material (20) in the material feed system (22, 10) in step (a) is extracted from the reservoir of the prehydrolysis reactor (14); in step (c), pressurized feed material is moved to an upper inlet of the pre-hydrolysis reactor reservoir (14); in step (i), the washed feed material is discharged from a lower outlet of the pre-hydrolysis reactor reservoir (14), where the lower outlet is close to a lower part of the wash zone, in step ( k), the unloaded feed material is transported to an upper inlet of the Kraft cooking vessel (16).
    [0003]
    3. Method, according to claim 1 or 2, characterized by the fact that the steps of the method are performed contentiously and simultaneously as the feeding material (20) flows through the feeding system (22, 10), from the reservoir of the pre-hydrolysis reactor (14) and the Kraft cooking tank (16).
    [0004]
    Method according to any one of claims 1 to 3, characterized by the fact that it still comprises the discharge of the pulp from the Kraft cooking vessel (16) into a blowing tank (18), and the discharge of the pulp from the heating tank blow (18) in a brown raw material washer.
    [0005]
    Method according to any one of claims 1 to 4, characterized in that the step of pressurizing the feed material includes pumping the feed material through at least one centrifugal pump, comprising the transfer device high pressure (12).
    [0006]
    Method according to any one of claims 1 to 5, characterized in that the step of adding the washing liquid includes injecting the washing liquid from a central coaxial tube into the pre-hydrolysis reactor reservoir ( 14) and have a discharge port in the lower region of the washing area.
    [0007]
    Method according to any one of claims 1 to 6, characterized in that the hydrolysis reaction is a self-hydrolysis reaction and a temperature in the feed material is between 150 degrees and 160 degrees Celsius or between 140 degrees and 175 degrees Celsius.
    [0008]
    Method according to any one of claims 1 to 7, characterized in that the pH of the pressurized feed material in the hydrolysis zone (56) is maintained at a pH in the range of 3 to 4, preferably at a pH from 3.5 to 4, more preferably at a pH of 4.
    [0009]
    Method according to any one of claims 1 to 8, characterized in that the washing liquid enters the washing zone at a temperature of at least 10 degrees Celsius below the hydrolysis temperature in the hydrolysis zone (56) .
    [0010]
    Method according to any one of claims 1 to 9, characterized in that the washing liquid includes a bisulfite compound.
    [0011]
    11. Method according to any one of claims 1 to 10, characterized in that the alkaline white liquor is added to the feed material when the feed material is in an upper region of the Kraft cooking vessel (16), or when the feed material is on a transfer line between the pre-hydrolysis reactor reservoir and the Kraft cooking reservoir.
    [0012]
    12. System for the production of pulp from cellulosic fibrous organic feed material, characterized by the fact that: a material feeding system (22, 10) having an inlet to receive the feed material, a steam inlet for receiving the steam to be injected into the feed material in the feed system (22, 10), a filtrate inlet and an outlet for the feed material; a high pressure transfer device (12) including an inlet in fluid communication with the outlet of the material feeding system (22, 10); a pre-hydrolysis reactor reservoir (14) having a high-pressure inlet in fluid communication with a high-pressure outlet of the high-pressure transfer device (12), in which the pre-hydrolysis reactor (14) includes an interior maintained at a temperature and pressure to promote hydrolysis of the feed material in the reactor, where the feed material (20) and liquor flow simultaneously down through the hydrolysis zone (56); an extraction sieve at the bottom of the pre-hydrolysis reactor (14), including a filter screen (60) adjacent to the interior of the pre-hydrolysis (14) and a filtrate outlet on one side of the filter screen (60 ) opposite the interior, where the filtrate outlet is coupled to the filtrate inlet of the material feeding system (22, 10) in such a way that the filtrate from the pre-hydrolysis reactor (14) flows into the filtrate inlet, wherein the filter screen (60) is located in a first elevation of the pre-hydrolysis reactor reservoir (14); a line (64) to reintroduce a portion of the liquor, including extra hydrolyzate (58) [gone through the filter screen (60) into the pre-hydrolysis reactor reservoir (14) at a second elevation which is above the first elevation; and a Kraft cooking vessel (16) having a high pressure inlet coupled to a high pressure discharge outlet of the pre-hydrolysis reactor feed material (14) such that the feed material flows from the reactor reservoir from prehydrolysis (14) to the entrance of the Kraft cooking vessel (16), where the interior of the Kraft cooking vessel (16) keeps the feed material in an alkaline environment, and the Kraft cooking vessel (16) it has a high pressure discharge outlet from which the feed material is discharged as slurry.
    [0013]
    13. System according to claim 12, characterized by the fact that the extraction sieve is in the vicinity of a hydrolysis zone (56) inside the pre-hydrolysis reactor reservoir (14) and a wash zone below the hydrolysis zone (56) and inside the pre-hydrolysis reactor reservoir (14).
    [0014]
    14. System, according to claim 12 or 13, characterized by the fact that it still comprises a blowing tank (18) coupled to the high pressure discharge outlet of the Kraft cooking reservoir (16), in which the pulp from the Kraft cooking vessel (16) flows to the blowing tank (18) where the pulp is depressurized.
    [0015]
    15. System according to any one of claims 12 to 14, characterized by the fact that the high pressure transfer device (12) includes centrifugal pumps.
    [0016]
    16. System according to any one of claims 12 to 15, characterized by the fact that it still comprises a central coaxial tube inside the pre-hydrolysis reactor reservoir (14), in which the washing liquid is discharged into from the inside of a lower outlet of the central tube and the lower outlet is close to a lower part of the pre-hydrolysis reactor reservoir (14).
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    同族专利:
    公开号 | 公开日
    EP2678470B1|2020-01-01|
    CA2827976A1|2012-08-30|
    RU2591672C2|2016-07-20|
    ES2769424T3|2020-06-25|
    CN103380247A|2013-10-30|
    CN103380247B|2016-08-10|
    CA2827976C|2019-12-31|
    CL2013002398A1|2013-12-27|
    WO2012115812A1|2012-08-30|
    US9371612B2|2016-06-21|
    US20120211183A1|2012-08-23|
    BR112013021316A2|2016-10-25|
    PT2678470T|2020-02-06|
    RU2013143021A|2015-03-27|
    EP2678470A1|2014-01-01|
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    法律状态:
    2018-04-03| B06F| Objections, documents and/or translations needed after an examination request according art. 34 industrial property law|
    2019-07-16| B06T| Formal requirements before examination|
    2020-06-30| B09A| Decision: intention to grant|
    2020-10-27| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 13/02/2012, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    US201161445253P| true| 2011-02-22|2011-02-22|
    US61/445,253|2011-02-22|
    US13/363,680|2012-02-01|
    US13/363,680|US9371612B2|2011-02-22|2012-02-01|Method and apparatus to produce pulp using pre-hydrolysis and Kraft cooking|
    PCT/US2012/024848|WO2012115812A1|2011-02-22|2012-02-13|Method and apparatus to produce pulp using pre- hydrolysis and kraft cooking|
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