US20040069427A1 - Multi-stage AP mechanical pulping with refiner blow line treatment - Google Patents

Multi-stage AP mechanical pulping with refiner blow line treatment Download PDF

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US20040069427A1
US20040069427A1 US10/677,545 US67754503A US2004069427A1 US 20040069427 A1 US20040069427 A1 US 20040069427A1 US 67754503 A US67754503 A US 67754503A US 2004069427 A1 US2004069427 A1 US 2004069427A1
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intermediate line
solution
alkaline peroxide
lignocellulosic material
pulping process
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Eric Xu
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Andritz Inc
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Andritz Inc
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Publication of US20040069427A1 publication Critical patent/US20040069427A1/en
Priority to US12/661,907 priority patent/US8216423B2/en
Abandoned legal-status Critical Current

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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/02—Pretreatment of the raw materials by chemical or physical means
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds
    • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/02—Pretreatment of the raw materials by chemical or physical means
    • D21B1/021—Pretreatment of the raw materials by chemical or physical means by chemical means
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
    • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
    • D21B1/14—Disintegrating in mills
    • D21B1/16—Disintegrating in mills in the presence of chemical agents
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/10—Bleaching ; Apparatus therefor
    • D21C9/16—Bleaching ; Apparatus therefor with per compounds

Definitions

  • the present invention relates to a process for the production of pulp from lignocellulosic material, such as wood chips or the like, by chemical-mechanical refining.
  • alkaline peroxide chemicals in a mechanical pulping system may be traced back as early as 1962. Since then, there have been a number of different process ideas developed to apply the chemicals before or during early stages of refiner pulping. In recent years, an extensive and systematic investigation has been reported on how different chemical treatments in refiner mechanical pulping affect pulp property development and the process consumption. For hardwoods, it was observed that alkaline peroxide pretreatment in general gives better optical properties, better bleachability and higher pulp yield at similar strength properties when compared to other conventional chemical pretreatment, such as alkaline sulfite and cold caustic soda processes. When compared to a peroxide post-bleaching process, applying alkaline peroxide before refining has a tendency to give a higher bulk at a given tensile strength for some hardwood species, such as North American aspen.
  • alkaline peroxide refiner mechanical pulping is a type of pulping process where hydrogen peroxide and alkali in various forms, together with various amounts of different peroxide stabilizers, are applied to the lignocellulosic materials before or during defiberization and fibrillation in a refiner.
  • two basic concepts were tried. One was to apply alkaline peroxide treatment on chips, to allow the bleaching reactions to complete or to approach completion before refining. The other basic concept was to apply all the alkaline peroxide at the refiner, either with no pretreatment or with stabilizers or other alkaline pretreatment prior to the alkaline peroxide application at the refiner.
  • the present invention is directed to the introduction of chemicals to lignocellulosic material immediately after refining in order to achieve, among other things, a comparable bleaching efficiency as when applying chemicals at locations upstream of and/or at the refiner.
  • the refiner may be a primary, secondary and/or tertiary refiner
  • the concept of applying chemicals such as alkaline peroxide pre-treatment to lignocellulosic material before refining is utilized with the concept of applying chemicals such as alkaline peroxide pre-treatment to lignocellulosic material before refining.
  • the refiner has a highly pressurized case, for achieving the known benefits of high pressure refining.
  • P-RC Preconditioning followed by Refiner Chemical treatment
  • APMP Refiner Chemical treatment
  • the preferred embodiment of the invention includes applying more than one-third of total alkaline peroxide (and/or other chemicals known in the art to bleach or otherwise process lignocellulosic material into pulp or precursors of pulp) at or near the blow valve in the post refiner intermediate line, in combination with chemical addition at the refiner and chemical impregnation of the chips upstream of the refiner, to yield a more energy efficient process and to allow a more efficient bleaching than the application of all the chemicals before discharge from the refiner.
  • a significant benefit of the invention is better chemical efficiency, by moving a greater number of chemical reactions downstream relative to conventional techniques, resulting from the relatively heavier or more intense addition of chemicals and/or chemical stabilizers at the post refiner blow line.
  • a further benefit of the invention is the reduction in the detrimental effects of the high temperature and/or other conditions prior to and during high pressure primary refining, which are known to influence pulp brightness and development.
  • Another benefit of the invention as implemented in a high-pressure system is the recovery of more and higher quality of steam and/or heat than in other types of P-RC APMP systems, where the primary refiner is either completely atmospheric or atmospheric at the inlet.
  • FIG. 1 is a block diagram depicting the general P-RC APMP process.
  • FIG. 1A is a block diagram depicting steps of transferring lignocellulosic material to a refiner having a casing at atmospheric pressure, with discharge at atmospheric pressure.
  • FIG. 1B is a block diagram depicting steps of transferring lignocellulosic material to a refiner having a pressurized casing with pressurized discharge.
  • FIG. 1C is a block diagram depicting steps of transferring primary pulp produced in the refiner with a casing at atmospheric pressure, to a high consistency tower via a transfer device.
  • FIG. 1D is a block diagram depicting steps of transferring primary pulp produced in the refiner with a casing at atmospheric pressure directly to a high consistency tower.
  • FIG. 1E is a block diagram depicting steps of transferring primary pulp produced in the refiner with a pressurized casing, to a high consistency tower via a transport device.
  • FIG. 1F is a block diagram consistent with an embodiment of the invention, depicting steps of transferring primary pulp produced in the refiner with a pressurized casing to a high consistency tower.
  • FIG. 2 is a table comparing P-RC with two prior art processes.
  • FIG. 3 is a graph of freeness as related to energy consumption for P-RC and two prior art processes.
  • FIG. 4 is a graph of density as related to energy consumption for P-RC and two prior art processes.
  • FIG. 5 is a graph of the tensile of tensile development for P-RC and two prior art processes.
  • FIG. 6 is a graph of burst development for P-RC and two prior art processes.
  • FIG. 7 is a graph of brightness development for P-RC and two prior art processes.
  • FIG. 8 is a graph of the light scattering coefficient of the pulp as a function of freeness for P-RC and two prior art processes.
  • FIG. 9 is a comparative table of atmospheric versus pressurized casing processing of aspen wood chips according to P-RC.
  • FIG. 10 is a comparative table of atmospheric versus pressurized casing processing of birch wood chips according to P-RC.
  • FIG. 11 is a block diagram consistent with an embodiment of the invention, depicting steps of transferring primary pulp produced in a refiner with a pressurized casing to a retention tower with a chemical addition in the intermediate line following the control valve.
  • FIG. 12 is a block diagram consistent with an embodiment of the invention, depicting steps of transferring primary pulp produced in the refiner with a pressurized casing to a retention tower with an alkaline peroxide chemical addition in the intermediate line prior to the inlet of the separator.
  • FIG. 13 is a block diagram consistent with an embodiment of the invention, depicting steps of transferring primary pulp produced in the refiner with a pressurized casing to a retention tower with an alkaline peroxide chemical addition in the intermediate line at the separator.
  • FIG. 14 is a block diagram consistent with an embodiment of the invention, depicting steps of transferring primary pulp produced in the refiner with a pressurized casing to a retention tower with an alkaline peroxide chemical addition in the intermediate line at the separator discharge.
  • FIG. 15 is a comparative table of refiner eye versus blow line chemical addition processing of birch and maple wood chips according to the invention.
  • FIG. 16 is a comparative table of refiner eye versus blow line chemical addition processing of spruce and red pine wood chips according to the invention.
  • FIG. 17 is a comparative table of refiner eye versus blow line chemical addition processing wood chips at higher pressure according to the invention.
  • FIG. 18 is a block diagram consistent with an embodiment of the invention, depicting steps of transferring pulp produced in a pressurized refiner via a intermediate line to a tower.
  • FIG. 1 presents a simplified process flow diagram of the P-RC alkaline peroxide mechanical pulping (APMP) process.
  • the P-RC process generally applies alkaline peroxide chemicals at chip pretreatment/chip impregnation step(s)/stage(s) 1 , 2 and as the material is fed to the primary refiner 3 .
  • the preconditioning step(s) as implemented in stages 1 and 2 of FIG. 1, preferably include one or two atmospheric compression devices, such as screw presses. Chip material is fed through an inlet, and passes through at least one compression region and at least one expansion region, and is discharged. A chemically active solution (pretreatment solution) is added to the material, typically while decompressing or decompressed at or near the discharge to facilitate penetration of the solution into the material.
  • pretreatment solution chemically active solution
  • the refining step 3 may include a primary refiner of conventional size, configuration, and operating conditions as known for chemi-mechanical pulping. Depending on such factors as whether chemicals are to be added and what types of chemicals if any are to be added the size, configuration, and operating of the refiner can be tailored so as to not expose the chemicals to excessive temperature or time-temperature combination.
  • the pressure can be within a range of about 15 psi to pressures greater than 45 psi. Any chemicals added at the refiner will be referred to as the refiner solution.
  • Steps implemented following the primary refining may have a level of chemical presence carried downstream from the refiner or other upstream processing.
  • the post refining chemical environment is modified by an addition or additions of a intermediate line solution or solutions to the intermediate line.
  • the intermediate line is located between the refiner and the retention tower.
  • alkaline peroxide solution is applied to pulp in the intermediate line, at the blow line 30 , after exposure to and discharge from the refiner.
  • the chemicals may be applied at a point or points along and about the blow line 30 .
  • the blow line 30 may extend between the blow valve and a separator of the intermediate line. As shown in FIG.
  • the chemicals may also be applied in the intermediate line immediately after the blow valve 40 , between the blow valve and the separator 42 immediately prior to separator 44 , at the separator 46 and/or immediately after the separator 48 .
  • the separator for instance a cyclone, may operate to separate steam/heat/liquid or combinations of those items from the pulp. Prior to entry into the separator the pulp may have a consistency of about 20% to about 60% and a temperature of about 80° C. to about 155° C.
  • Injection of the chemicals at a intermediate line location or locations may be made through simple orifices in the intermediate line and/or by the use of injectors, such as nozzles, associated with the line.
  • the nozzles can be associated with the intermediate line in various ways along and about the intermediate line to desirably control the chemical addition.
  • the control can be dependent, for example, on the effect that the additions have with regard to the bleaching process and/or conditioning process.
  • Chemical profiles within the pulp flow can thus be modified or maintained by, for example, injection sequencing, flow rate, composition, and/or duration. Other variables such as the depth of injector intrusion into the flow path, injector angle, injector orifice configuration, and other properties of the injector installation may be modified to achieve a desired result.
  • Chemical introduction may be modified by varying the introduction location based on the pressure used in refining. For instance, alkaline peroxide chemicals may be introduced immediately (from less than a few inches to a few feet) after the blow valve, especially in low pressure refining where the pressure is less than about 45 psi. The alkaline peroxide chemicals may also be introduced immediately before the cyclone (from less than a few inches to a few feet) after the blow valve, especially in high pressure refining where pressures higher than 45 psi are used. In other cases the alkaline peroxide chemicals may be introduced intermediate the cyclone and the blow valve, or even at the cyclone.
  • the refiner may be primary, secondary, and/or tertiary, with a pressurized casing or fully pressurized from preheater to refiner discharge.
  • the pressure in the refiner aids in expelling the pulp from the refiner during discharge.
  • the discharge can be modified or controlled by, e.g., the blow valve.
  • the pressure assisted discharge of the pulp into the intermediate line can result in the pulp having a residence time of a few seconds to minutes in portions of the intermediate line.
  • the pulp can achieve high velocities and experience significant turbulence as it flows through the intermediate line. These conditions enhance the mixing between the chemicals and the pulp.
  • the intensive turbulence and a high temperature gradient in the pulp stream may also assist in transferring the chemicals to individual pulp fibers as well into the fiber wall.
  • the pulp may be about 100° C. or higher, and the chemical liquor may be 40° C. or lower.
  • the intermediate line solution may preferably be in the range of about 10° C. to about 25° C. but can be up to 80° C.
  • the application of alkaline peroxide chemicals at the intermediate line reduces the exposure time of the alkaline peroxide chemicals to high temperature, especially when elevated temperature and/or pressure is present at refining. This post refining addition to the pulp flow through injection proximity, facilitates an easier stabilization and an increased efficacy of the peroxide.
  • the use of the invention in an intermediate line with a superatmopheric refiner system also can result in the enhanced or modified recovery of steam/heat/liquid from the pulp.
  • Such steam may be diverted away through a steam pipe 36 .
  • These features also allow for the production of high-freeness pulps with low shives content, since it is well known in the industry that the higher refining pressure tends to produce lower shives, or cleaner pulp.
  • a press may be included in addition to or in place of the cyclone 32 . The press could allow for an increase in steam/heat/liquid recovery from the pulp.
  • the optimizing process to influence peroxide efficiency and brightness development can be accomplished when the primary refining is fully pressurized.
  • this may be referred to as P-RC APTMP, which differs from other P-RC APMP configurations where the primary refiner is operated either under completely atmospheric pressure, or with atmospheric pressure at the inlet and low pressure at the casing.
  • FIGS. 1A through 1F present various examples of a P-RC 20 process of the type generally shown in FIG. 1.
  • FIGS. 1A and B show that after the material is pretreated at 1 and/or 2 , addition of the solution to the lignocellulosic material may more specifically occur at a cross conveyer 10 , downstream of the screw press and near refiner 3 , or at the refiner itself, e.g., the ribbon feeder 12 , the inlet eye of the refiner disc 14 , and/or at the inlet zone of the plates on the refiner disc 16 .
  • chemical addition “as the material is fed to the refiner”, encompasses the locations 10 , 12 , 14 , and 16 .
  • the refiner in a P-RC process may have an atmospheric casing 3 A or an overpressure casing 3 B, but the inlet to the refiner would normally be at atmospheric pressure.
  • the discharge from a pressurized casing 20 a of primary pulp may be through a blow valve or similar device, and discharge from an atmospheric casing 20 may be by gravity drop or the like.
  • the discharge from the refiner will, in any event, directly or indirectly go to a high consistency-bleaching tower 24 of any type known in the art (but subject to temperature control).
  • the pretreatment solutions, the refiner solutions (if present), and the intermediate line solutions act chemically on the lignocellulosic material. It may be advantageous, depending on the lignocellulosic material and the processing equipment, to modify the chemical exposure profile of the material to the chemical agents in order to optimize the process, and/or eliminate or reduce unwanted chemical effects or degradation. Such chemical profile modification may be accomplished by sequential chemical additions throughout the process, and can be combined with other variable conditions such as temperature, concentration, pressure, and duration to further enhance the desired effect.
  • Lignocellulosic material processed using the P-RC process can be discharged 4 from the primary refiner casing (either atmospheric discharge 20 or overpressure discharge 20 a ), as a primary pulp having a measurable freeness and could properly be called a pulp able to form a handsheet.
  • atmospheric discharge from the refiner could pass via a transfer device 22 such as a transfer screw, to the tower 24 , or more directly 28 via a chute or the like.
  • FIGS. 1E and F with a pressurized casing the refined pulp would typically be discharged through a blow valve and delivered either directly or indirectly to the tower.
  • the bleached pulp exiting the tower can be further processed in, e.g., a secondary refiner.
  • the high consistency retention tower 24 allows the chemical bleaching reactions carried over from upstream of the tower to continue.
  • the discharge from the blow valve may be delivered indirectly to a retention tower through a seperator and/or a press.
  • the addition of chemicals into the post refining intermediate line allows, for example, the use of a pressurized refiner and higher temperatures in refining.
  • Addition of chemicals to the intermediate line at, for example, the blow line provides for a fast, and more direct, distribution of chemicals such as peroxide to the chromophore sites for efficient bleaching. This efficiency is achieved because the targeted peroxide reactions are carried out at the reaction site of interest quickly without lengthy exposure to the more heterogeneous environment present in previous portions of the process.
  • the temperature at the inlet between the plates of a refiner pushes the chromophore removal and hemicellulose alkali reactions so fast that that pH is lowered prematurely.
  • the post refiner intermediate line as the location for chemical mixing according to an aspect of the present invention, distributes the chemicals fast enough, to compete favorably against and counter to a significant extent, the elevated temperature of the pulp.
  • elevated temperature can be, for example, from about 80° C. to about 155° C.
  • the pulp can be maintained in an interstage high consistency retention tower.
  • the pulp in the high consistency retention tower may have a consistency of about 20% to a consistency of about 40% consistency, with a preferable consistency of about 30%.
  • the temperature of the pulp in the high consistency retention tower may be from about 60° C. to about 95° C.
  • the pulp can be held in the retention tower from about 30 minutes to more than 2 hours depending on the chemical reaction needed for chemical treatment.
  • the maintenance conditions include but are not limited to temperature, pressure, pH, chemical concentration, solids concentration, and time, that allow for conditioning and/or bleaching of the pulp to continue and limit the degradation of the bleaching agent through reactions that are extraneous to the bleaching of the pulp.
  • Such extraneous reactions may be non-productive, inefficient, and/or harmful to the bleaching of the pulp.
  • Control of some and/or all of the conditions may or may not be needed depending on e.g., the type and condition of the lignocellulosic material used in the process, and the type, size and operating environment of the equipment itself.
  • conditions of temperature may be modified throughout the process by the addition of the chemicals, pressurized gas, and other heating or cooling methods.
  • Temperature modifying means may be employed during transfer of the primary pulp 22 by using a mixing screw with water added while the pulp is mixed and transferred to the tower.
  • the temperature of the primary pulp may also be thermally adjusted within the tower if the primary pulp is discharged directly to the tower 28 , by means known in the art.
  • the pulp may be thermally adjusted through addition of liquids or gases, and/or through use of heat transfer components such as tubing, tower jacketing, etc.
  • control should be understood as including both active and passive techniques. Thus, control could be implemented by a static hardware configuration or by continually measuring one or more process parameters and controlling one or more process variables.
  • the chemical conditions present anywhere in the inventive process may be modified by additives to prevent extraneous degradation. This modification may be made at, by way of example, the pretreatment step(s) 1 and/or 2 , the cross conveyer 10 , the ribbon feeder 12 , the inlet eye of the refiner disc 14 , the plates of the refiner disc 16 , the blow valve 20 a, the blow line 30 , the separator, 32 , and/or after the separator.
  • An example of stabilizers would be chelation agents.
  • a chelation agent refers to a compound that has an ability to form complexes, so called chelates, with metals occurring in the lignocellulosic material, and primary pulp.
  • Such metals may include monovalent metals sodium and potassium, earth-alkali divalent metals calcium, magnesium and barium, and heavy metals such as iron, copper and manganese.
  • the metal ions retained in the material as it is processed makes the bleaching by oxygen chemicals (such as hydrogen peroxide) less effective, and results in excess chemical consumption as well as other problems well known in the art.
  • oxygen chemicals such as hydrogen peroxide
  • chelants such as for example diethylene triamine pentaacetic acid (DTPA), ethylene diamine tetraacetic acid (EDTA) and nitriletriacetic acid (NTA) may be used.
  • DTPA diethylene triamine pentaacetic acid
  • EDTA ethylene diamine tetraacetic acid
  • NTA nitriletriacetic acid
  • silcates and sulfates as examples may also be used advantageously as stabilizers as well as serving other functions well known in the art.
  • Wood A blend of 50% aspen and 50% basswood was used in this study. The aspen woods had rotten centers, which made it more difficult to bleach than normally expected. The woods were all from Wisconsin USA, and debarked, chipped and screened before further processing.
  • Chips were pre-steamed first for 10 minutes, and then pressed using an Andritz 560GS Impressafiner at 4:1 compression ratio before impregnated with alkaline peroxide chemical liquor.
  • the chemical liquor was introduced at the discharge of the press, and allowed for 30 minutes retention time before refining.
  • Pulp Testing Tappi Standards were used for all pulp testing except for freeness, which follows Canadian Standard Freeness (CSF) test methods.
  • the second series used approximately two thirds of the total alkaline peroxide chemicals, (or 2.4% TA, 1.6% H 2 O 2 , 0.08% DTPA, 0.04% MgSO 4 and 2.4% Na 2 SiO 3 ), at the chip impregnation stage, and approximately one third of the total chemicals, (1.0% TA, 1.0% H 2 O 2 , 0.19% DTPA, 0.05% MgSO 4 , and 0.9% Na 2 SiO 3 ), at the eye of the primary refiner. It is labeled as “Chip+Refiner”, and represents the invention.
  • the chips were first pressed using the same chip press as the first two series, and then all the alkaline peroxide chemicals, (4.2% TA, 3.3% H 2 O 2 , 0.36% DTPA, 0.11% MgSO 4 , 4.3% Na 2 SiO 3 ), were applied at the eye of the primary refiner.
  • the pulp from the primary was allowed 15 minutes retention under cover in drums, (which gave a temperature about 80-90° C.), before the second stage refining. There was no interstage washing.
  • FIG. 2 summarizes some of the process conditions and results from each series.
  • the pulps are all from second stage refining.
  • a lower TA/H 2 O 2 ratio is in general preferred under higher temperature to prevent, or to reduce the possibility of alkali darkening reaction.
  • Table 1 the lowest TA/H 2 O 2 ratio, 1.27, was use for “Refiner” series, the second lowest, 1.31, for “Chip+Refiner” series, and the highest, 1.37, for “Chip” series.
  • FIG. 3 shows effects of the different chemical applications on pulp freeness development in relation to specific energy consumption (SEC), which includes energy consumed during chip pretreatment stage.
  • SEC specific energy consumption
  • the “Chip+Refiner” series used slightly less SEC than the “Chip” series, but both series used, on average, approximately 200 kwh/odmt less SEC than the refiner bleaching series, “Refiner”, even though the latter had more caustic chemicals applied than the first two series and has the same residual pH, 8.2, as “Chip+Refiner” series. It appears that adding the alkaline chemical under high temperature, at refiner eye, causes more alkali consumed on nonproductive, or side reactions that have little to do with pulp property development.
  • FIG. 7 shows brightness at different freeness from each series.
  • “Chip+Refiner” series had a similar brightness development as that of the “Refiner” series, even though the former used less amount of the bleaching chemicals, 2.6% H 2 O 2 /3.4% TA versus 3.3% H 2 O 2 /4.2% TA. Adding all of the chemicals at the impregnation stage, “Chip” series, showed also a less bleaching efficiency, 2 or more points lower, than that of “Chip+Refiner” series.
  • FIG. 8 shows that there was no difference in light scattering property development in all the series studied, suggest the pulp surface development mechanism also remain the same as long as the chemicals are added before refining.
  • Wood Aspen and birch chips from a commercial pulp mill in eastern Canada were used in this study.
  • Chip Impregnation A conventional pilot chip impregnation system was used in this study. In all the P-RC APMP runs studied, only DTPA was used in the first stage of chip impregnation. The chips were then impregnated with alkaline peroxide (AP) chemicals at second stage impregnation. The AP treated chips were then allowed for 30 to 45 minutes' retention (without steaming) before being refined.
  • AP alkaline peroxide
  • Atmospheric Refiner System Andritz 36′′ diameter (92 cm) double disc 401 system is typically used for conventional P-RC APMP process investigations. This system consists of an open metering belt, an incline twin-screw feeder, the refiner and an open belt discharge. The system is used for both primary and later stages of refining. When used for the primary, the pulp discharged were collected in drums and kept under cover to maintain a high temperature (typically 80 to 90° C.) for a certain period of time.
  • a high temperature typically 80 to 90° C.
  • Pressurized Refiner System An Andritz single disc 36′′ diameter (92 cm) pressurized system was modified for atmospheric inlet/pressurized casing configuration.
  • the original refiner system has all the standard features of a conventional TMP system.
  • a valve was placed on top of the vertical steaming tube and was kept open during refining.
  • the plug screw feeder (PSF) was run at 50 rpm (normal speed for TMP is 10 to 20 rpm) to ensure the chemical impregnated chips were not compressed.
  • the AP impregnated chips were placed in a chip bin, which discharged the chips into a blower.
  • the chips were then blown to a cyclone and discharged to a conveyor, which feeds the PSF.
  • the chips were then dropped into a vertical steam tube before being fed into the refiner.
  • the primary refiner was controlled to have zero pressure at the inlet and 140 kPa in the casing. From the casing, the primary pulp was blown to a cyclone and discharged and collected in drums, and then treated similarly as in the atmospheric refining runs.
  • Pulp Tests TAPPI standard was used for brightness tests. Peroxide residuals were measured using standard iodometric titration.
  • FIG. 9 presents the chemical conditions used for P-RC APMP pulping of aspen, and brightness results from atmospheric and casing pressurized runs with the primary refiner. Applying similar AP chemical strategies in both cases, and having similar amounts of total chemical consumption (5.2 to 5.4% total alkali, TA, and 3.7 to 3.9% H 2 O 2 ), both the atmospheric and the casing pressurized gave a similar brightness, achieving 84.2% ISO and 84.7% ISO respectively.
  • FIG. 10 presents conditions and results from P-RC APMP pulping of the birch. This particular birch chips was slightly more difficult to bleach than the aspen. Using similar AP chemical strategies, the atmospheric and the pressurizing casing again gave similar bleaching efficiency: 3.1-3.2% TA and 3.4-3.6% H 2 O 2 to reach 82.4 to 82.6% ISO brightness. In this case, the residual chemicals (0.1-0.2% TA, 0.5-0.6% H 2 O 2 and pH of 8) were within ideal H 2 O 2 bleaching conditions.
  • This example set shows, among other things, that when the chemical recipe and distributions are optimized, the alkali peroxide chemicals at refiner chemical treatment stage can be applied at the intermediate line in a pressurized refiner system to achieve similar bleaching efficiency as P-RC APMP with conventional atmospheric inlet pressure. Because the residence time is very short in a intermediate line, the same process may also be used in a high pressure refining system, for example a refining system operating at 4 bar or higher.
  • the wood chips were impregnated twice with AP chemicals (consisting of sodium hydroxide (NaOH), hydrogen peroxide (H 2 O 2 ), DTPA, Magnesium Sulfate (MgSO 4 ) and sodium silicate (Na 2 SiO 3 ), utilizing an Andritz 560GS Impressafiner System.
  • AP chemicals consisting of sodium hydroxide (NaOH), hydrogen peroxide (H 2 O 2 ), DTPA, Magnesium Sulfate (MgSO 4 ) and sodium silicate (Na 2 SiO 3 ), utilizing an Andritz 560GS Impressafiner System.
  • the RT-Pressafiner was used at the first stage impregnation (steamed at 1.4 bar for 20 seconds before being pressed).
  • An Andritz 36′′ diameter (91 cm) single disc 36-1CP refiner system was used for all pressurized and atmospheric inlet/casing pressurized runs, and an Andritz 36′′ diameter (91 cm) double disc 401 system was used for all atmospheric refining runs. Typically, except where stated otherwise, the 401 refiner was used for all secondary and tertiary refining.
  • the P-RC (Preconditioning, following by Refiner Chemical treatment, where AP chemicals are distributed between chip pretreatment and refining stages), process was used in all trial runs.
  • the pulp discharged from the blow line was covered under a plastic bag in drums to maintain a temperature of 85-95° C., depending specific refining energy used at the refiner, the chemical charges, and the nature of the raw materials.
  • CSF Canadian Standard Freeness
  • FIG. 15 shows the results obtained by applying AP chemicals at either the refiner eye or the intermediate line during the refiner chemical (RC) treatment stage.
  • Birch and maple woods were used in this example.
  • some chemical pretreatment, (preconditioning) was applied on the chips.
  • For birch the chips were treated with 0.3% DTPA at first stage impregnation, and then 0.2% MgSO 4 , 4.4% Silicate, 2.8% TA, and 2.8% H 2 O 2 at the second stage impregnation.
  • the chips were treated with 0.5% DTPA at first stage impregnation, and then 0.2% DTPA, 0.1% MgSO 4 , 2.0% Silicate, 1.6% TA and 2.6% H 2 O 2 at the second stage impregnation.
  • the preconditioned chips then received a similar amount of AP chemicals during refiner chemical (RC) treatment stage, but at different points: one at the refiner eye before refining, and another at the intermediate line immediately after refining.
  • RC refiner chemical
  • both series (A 1 and A 2 ) used a total of 5.2% H 2 O 2 and 4.6% total alkali (TA), and had a similar amount of H 2 O 2 residuals (1.0%-1.1%) and final pH (8.9-9.0).
  • the final pH's were relatively high, indicating that a higher brightness would be achieved if a longer retention time was used.
  • the series from AP addition at the refiner eye (A 1 ) had a similar brightness to samples where AP chemicals were added at the intermediate line, A 2 , for example, 84.8 versus 84.2% ISO.
  • FIG. 16 summarizes the results, and shows again that similar brightness was achieved by applying AP chemicals at either the refiner eye or the intermediate line.
  • the chips were first impregnated with 0.3% DTPA, 0.05% MgSO 4 , 0.7% Silicate, 0.2% TA and 0.5% H 2 O 2 , and then 0.1% DTPA, 0.08% MgSO 4 , 1.8% Silicate, 1.4% TA and 1.9% H 2 O 2 at second stage impregnation.
  • a softwood blend from spruce and pine was subjected to high pressure refining at the refiner chemical treatment stage as in FIG. 17.
  • a RT-Pressafiner was used at the first stage impregnation, and Andritz Model 560GS Impressafiner at the second stage.
  • FIG. 17 presents results, and shows that the series with the higher pressure, A 10 , was able to achieve similar bleaching efficiency and brightness (using 1.7% TA and 2.8% H 2 O 2 and reached 73.7-73.4% ISO).
  • the samples had similar light absorption coefficient (0.96-1.1 m 2 /kg).

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WO2013016311A1 (en) 2011-07-28 2013-01-31 Georgia-Pacific Consumer Products Lp High softness, high durability bath tissue incorporating high lignin eucalyptus fiber
WO2013016261A1 (en) 2011-07-28 2013-01-31 Georgia-Pacific Consumer Products Lp High softness, high durability bath tissue with temporary wet strength
WO2013074202A1 (en) 2011-11-17 2013-05-23 Buckman Laboratories International, Inc. Silicate free refiner bleaching
US8673113B2 (en) 2010-06-09 2014-03-18 The University Of British Columbia Process for reducing specific energy demand during refining of thermomechanical and chemi-thermomechanical pulp
WO2014052763A1 (en) * 2012-09-27 2014-04-03 Andritz Inc. Chemical treatment of lignocellulosic fiber bundle material, and methods and systems relating thereto
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CN100400743C (zh) * 2006-01-13 2008-07-09 东营中盛环保纸业科技有限公司 禾本科植物类快速冷浸机械制浆工艺
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US20100263815A1 (en) * 2001-07-19 2010-10-21 Eric Chao Xu Multi-stage AP mechanical pulping with refiner blow line treatment
US8048263B2 (en) * 2001-07-19 2011-11-01 Andritz Inc. Four stage alkaline peroxide mechanical pulpings
US8216423B2 (en) 2001-07-19 2012-07-10 Andritz Inc. Multi-stage AP mechanical pulping with refiner blow line treatment
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US9493911B2 (en) 2011-07-28 2016-11-15 Georgia-Pacific Consumer Products Lp High softness, high durability bath tissues with temporary wet strength
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US9267240B2 (en) 2011-07-28 2016-02-23 Georgia-Pacific Products LP High softness, high durability bath tissue incorporating high lignin eucalyptus fiber
US9309627B2 (en) 2011-07-28 2016-04-12 Georgia-Pacific Consumer Products Lp High softness, high durability bath tissues with temporary wet strength
US9476162B2 (en) 2011-07-28 2016-10-25 Georgia-Pacific Consumer Products Lp High softness, high durability batch tissue incorporating high lignin eucalyptus fiber
US9739015B2 (en) 2011-07-28 2017-08-22 Georgia-Pacific Consumer Products Lp High softness, high durability bath tissues with temporary wet strength
WO2013016311A1 (en) 2011-07-28 2013-01-31 Georgia-Pacific Consumer Products Lp High softness, high durability bath tissue incorporating high lignin eucalyptus fiber
WO2013074202A1 (en) 2011-11-17 2013-05-23 Buckman Laboratories International, Inc. Silicate free refiner bleaching
US9115468B2 (en) 2012-09-27 2015-08-25 Andritz Inc. Chemical treatment of lignocellulosic fiber bundle material, and methods and systems relating thereto
WO2014052763A1 (en) * 2012-09-27 2014-04-03 Andritz Inc. Chemical treatment of lignocellulosic fiber bundle material, and methods and systems relating thereto
WO2018049522A1 (en) * 2016-09-14 2018-03-22 Fpinnovations Method of transforming high consistency pulp fibers into pre-dispersed semi-dry and dry fibrous materials
EP3512996A4 (en) * 2016-09-14 2020-05-20 FPInnovations PROCESS FOR CONVERTING HIGH CONSISTENCY PULP FIBERS INTO SEMI-DRY AND DRIED PRE-DISPERSED FIBROUS MATERIALS
US11834785B2 (en) 2016-09-14 2023-12-05 Fpinnovations Method of transforming high consistency pulp fibers into pre-dispersed semi-dry and dry fibrous materials

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US8216423B2 (en) 2012-07-10
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