EP0483163B1 - Procede moins polluant de blanchiment de matieres lignocellulosiques - Google Patents

Procede moins polluant de blanchiment de matieres lignocellulosiques Download PDF

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EP0483163B1
EP0483163B1 EP90908787A EP90908787A EP0483163B1 EP 0483163 B1 EP0483163 B1 EP 0483163B1 EP 90908787 A EP90908787 A EP 90908787A EP 90908787 A EP90908787 A EP 90908787A EP 0483163 B1 EP0483163 B1 EP 0483163B1
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Prior art keywords
pulp
ozone
viscosity
delignification
consistency
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EP0483163A1 (fr
EP0483163A4 (en
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Bruce F. Griggs
Thomas P. Gandek
Michael A. Pikulin
Allen Rosen
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Union Camp Patent Holding Inc
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Union Camp Patent Holding Inc
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    • 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
    • D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
    • 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
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • 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
    • D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
    • D21C9/153—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications with ozone

Definitions

  • This invention relates to a novel, environmentally acceptable process for delignifying and bleaching lignocellulosic pulp which does not require the use of elemental chlorine and which produces a pulp of acceptable strength. Use of this process also reduces the amount of environmental pollutants.
  • Wood is comprised of two main components - a fibrous carbohydrate, i.e., cellulosic portion, and a non-fibrous component.
  • the polymeric chains forming the fibrous cellulose portion of the wood are aligned with one another and form strong associated bonds with adjacent chains.
  • the non-fibrous portion of the wood comprises a three-dimensional polymeric material formed primarily of phenylpropane units, known as lignin. Part of the lignin is between the cellulosic fibers, bonding them into a solid mass, although a substantial portion of the lignin is also distributed within the fibers themselves.
  • Pulp may be defined as wood fibers capable of being slurried or suspended and then deposited upon a screen to form a sheet, i.e., of paper.
  • the methods employed to accomplish the pulping step usually involve either physical or chemical treatment of the wood, or a combination of these two treatments, to alter the wood's chemical form and to impart desired properties to the resultant product.
  • pulping techniques There are thus two main types of pulping techniques, i.e., mechanical pulping and chemical pulping.
  • mechanical pulping the wood is physically separated into individual fibers.
  • chemical pulping the wood chips are digested with chemical solutions to solubilize a portion of the lignin and thus permit its removal.
  • the commonly utilized chemical pulping processes are broadly classified as: (1) the soda process, (2) the sulfite process, and (3) the Kraft process, with the latter process being most commonly used and being capable of a variety of well-known modifications as described below.
  • the soda process is well known in the art. It employs sodium hydroxide (NaOH) as the active reagent to break down the lignin and to assist in its removal.
  • NaOH sodium hydroxide
  • the sulfite process is also well known in the art (see, e.g., Handbook for Pulp & Paper Technologists - Chapter 6: Sulfite Pulping (TAPPI, U.S.A.).
  • Kraft Pulping involves digesting the wood chips in an aqueous solution of sodium hydroxide (NaOH) and sodium sulfide (Na2S). This process is highly effective in the pulping of even difficult woods such as southern softwoods, as well as the other more readily pulped species of wood such as northern hardwoods and softwoods.
  • the Kraft process likewise generally produces a relatively high-strength pulp since its use results in a diminished attack on the cellulose component of the wood.
  • the modified Kraft techniques can result in even less degradation in the polymeric structure of the cellulosic fibers during pulping and therefore the strength loss in the resultant paper product is diminished as compared to that occurring with the standard Kraft process.
  • One modified Kraft pulping process is known as "extended delignification", which is a broad term used in the art to encompass a variety of modified Kraft techniques, such as adding the pulping chemicals in a specific defined sequence, or at different locations within the digester apparatus, or at different time periods, or with a removal and reinjection of cooling liquors in a prescribed sequence, so as to more effectively remove a greater amount of lignin while reducing the severity of the pulping liquor's chemical attack on the cellulosic fibers.
  • Another modification of the Kraft process is the Kraft-AQ process, wherein a small amount of anthraquinone is added to the Kraft pulping liquor to accelerate delignification while limiting the attack upon the cellulosic fibers which comprise the wood.
  • the digested material Prior to bleaching the pulp, however, the digested material is conventionally transferred to a separate blow tank after the chemical treatments involved in the pulping process are completed. Within the blow tank, the pressure developed during the initial chemical treatment of the lignocellulosic material is relieved and the pulp material is separated into a fibrous mass. The resulting fibrous mass is then subjected to a series of washing steps to remove the combination of any residual chemicals and the soluble materials (such as the lignin) which were separated from the fibrous materials in the pulping process. Frequently, the pulp also undergoes one or more screening steps designed to separate out the larger portions of undefibered wood for special processing (recooking, mechanical grinding, etc.).
  • black liquor The residue obtained from the washing process, commonly referred to as black liquor, is collected, concentrated, and then incinerated in an environmentally safe manner in a recovery boiler.
  • the technique for the collection, concentration and burning of the black liquor is conventional and is well known in the art.
  • the delignification and bleaching processes are conducted on the washed fibrous mass in a series of steps, using selected combinations of chemical reactants.
  • various combinations of chemical treatments have been suggested.
  • individual treatment steps have been rearranged in an almost limitless number of combinations and permutations. Therefore, in order to simplify the explanation of the various bleaching processes and systems, the use of letter codes is conventionally employed in combination to describe the particular chemical reactants employed and the sequence of the steps of the process.
  • O m and Z m are modified processes according to the present invention and are described further in the Detailed Description of the Invention.
  • Oxygen is not as selective a delignification agent as elemental chlorine, and the K No. of the pulp, using conventional oxygen delignification methods, can be reduced only a limited amount until there is a disproportionate, i.e., unacceptable, attack on the cellulosic fibers. Also, after oxygen delignification, the remaining lignin has heretofore typically been removed by chlorine bleaching methods to obtain a fully-bleached pulp, but using much reduced amounts of chlorine. However, even at such reduced chlorine concentrations, the corrosive chlorides would soon reach unacceptable concentration levels in a closed cycle operation.
  • ozone may initially appear to be an ideal material for bleaching lignocellulosic materials
  • exceptional oxidative properties of ozone and its relative high cost have heretofore limited the development of satisfactory ozone bleaching processes for lignocellulosic materials, especially southern softwoods.
  • Ozone will readily react with lignin to effectively reduce the K No., but it will also, under most conditions, aggressively attack the carbohydrate which comprises the cellulosic fibers and substantially reduce the strength of the resulting pulp.
  • Ozone likewise, is extremely sensitive to process conditions such as pH with respect to its oxidative and chemical stability, and such changes can significantly alter the reactivity of ozone with respect to the lignocellulosic materials.
  • US-A- 4,196,043 to Singh discloses a multi-stage bleaching process which also attempts to eliminate the use of chlorine compounds, and includes examples specifically directed to hardwoods. It is well known to those skilled in the art that hardwoods are easier to bleach than most softwoods.
  • This process is characterized by from one to three ozone bleaching stages and a final treatment with alkaline hydrogen peroxide, each stage being separated by an alkaline extraction.
  • One such sequence may be described in the common shorthand nomenclature of the paper industry as ZEZEP.
  • the effluent from each treatment stage may be collected and recycled for use in bleaching operations, preferably at an earlier stage than that from which it was obtained.
  • This patent also provides a so-called countercurrent effluent flow.
  • the present invention provides novel combinations of pulping and bleaching steps which overcome the problems encountered in the prior art as discussed herein and which essentially eliminate the discharge of chlorinated organics and minimizes color and BOD releases to produce a high grade bleached pulp in a commercially feasible manner.
  • the present invention can work on virtually all wood species, including the difficult-to-bleach southern U.S. softwoods.
  • a first step involves delignification of wood chips into a lignocellulosic pulp, using any one of several chemical pulping processes, followed by a washing removal of most of the dissolved organics and cooking chemicals for recycle and recovery. Usually included is a screening of the pulp to remove bundles of fibers that have not been separated in pulping.
  • This delignification step is conducted so that, for a southern U.S. softwood, for example, pulp with a K No. in the range of about 20-24 (target of 21), a cupriethylenediamine (“CED”) viscosity in the range of about 21-28, and a GE brightness in the range of about 15-25 is typically obtained.
  • CED cupriethylenediamine
  • the extended delignification techniques discussed in (b) and (c) above may include, for example, the Kamyr MCC, the Beloit RDH and Sunds Cold Blow Cooking techniques described in the background portion of this specification.
  • the soda and sulfite processes mentioned above may be used.
  • a second step of the process includes an oxygen delignification treatment to further remove lignin without an accompanying significant loss in cellulosic fiber strength. This would include a washing removal of the dissolved organics and alkali for recycle and recovery. Pulp screening is also performed at times after oxygen delignification.
  • the K No. of the increased consistency pulp is decreased by at least about 45% (for O) to at least about 60% (for O m ) without significantly damaging the cellulose component of the pulp.
  • the ratio of K No. to viscosity of the pulp is typically decreased by at least 25%.
  • a K No. of about 7 to 10 and a viscosity of above about 13 is easily achieved.
  • a K No. of about 5 to 8 and a viscosity above about 13 is achieved after the oxygen delignification step.
  • a third step of the process include an acidic, gaseous ozone bleaching treatment (Z or Z m ) under defined process parameters to provide a highly selective removal and bleaching of lignin with minimal degradation of cellulose.
  • process parameters include chelating agents for metal ion control, pH control, pulp particle size control, pulp consistency, ozone concentration and gas/pulp contact control.
  • the chelating agent for example oxalic acid, diethylenetriamine pentaacetic acid (“DTPA”) or ethylene diaminetetraacetic acid (“EDTA”) may be added to the pulp to substantially bind with metal ions contained therein.
  • the pH of the pulp is preferably adjusted to a range of between about 1-4 prior to the third step.
  • the consistency of the pulp is increased to between about 35-45% by weight and the particle size of the fiber flocs are comminuted to a size of about 5 mm or less prior to the ozone delignification step. Included is a dissolved organic washing stage for recycle and recovery.
  • the pulp is preferably maintained at ambient temperature or at least at a pulp temperature of less than about 49°C (120°F).
  • the ozone may be provided by an ozone-containing gas which may comprise, for example, oxygen or air.
  • the ozone concentration is preferably between about 1 and 8 percent by volume, whereas for ozone/air mixtures, an ozone concentration of between about 1 and 4 percent by volume is acceptable.
  • the substantially delignified pulp is advanced in a manner which subjects substantially all of the pulp particles to the ozone in a uniform fashion.
  • pulps with K Nos. greater than about 10 after the second step are not suitable for this third step, because of the substantial amounts of ozone required to reduce the K No. to the desired level, which typically results in the properties of the pulp being adversely and deleteriously affected by excessive ozone degradation of the cellulose fibers of the pulp.
  • a lesser concentration of ozone is used, with only a minimal amount of cellulose degradation occurring.
  • the product from this ozonation step for either the starting southern U.S. softwood or hardwood described above is a pulp having a K No. of less than about 5 and generally in the range of about 3 to 4 (target of 3.5), a viscosity of above about 10, and a GE brightness of at least 50% (typically about 54% or higher for softwood and 63% or higher for hardwood).
  • An additional bleaching step may then be used to bring the pulp to a desired fully bleached state, i.e., one having GE brightness levels of about 70 to 95% using any number of possible, well recognized bleaching and extraction processes.
  • the effective embodiments are:
  • the extraction stage may comprise, in a further embodiment, combining the substantially delignified pulp with an effective amount of an alkaline material in an aqueous alkaline solution for a predetermined time and at a predetermined temperature correlated to the quantity of alkaline material to solubilize a substantial portion of any lignin which remains in the pulp. Thereafter, a portion of the aqueous alkaline solution may be extracted to remove substantially all of the solubilized lignin therefrom.
  • the substantially delignified pulp may be treated in the additional bleaching step to raise the GE brightness of the resultant pulp to at least about 70%.
  • Preferred brightening agents include chlorine dioxide or a peroxide.
  • the (E o )D, (E op )D or EDED embodiments will achieve the highest brightness levels.
  • the chlorine dioxide stage filtrate cannot, without treatment, be recycled for chemical recovery because of the presence of the inorganic chlorides. Since this is the only required sewered filtrate from the process, however, dramatic reductions in effluent volume, color, COD, BOD, and chlorinated organics are achieved. Color of less than 1 kg/tonne (2 pounds per ton), BOD5 of less than 1 kg/tonne (2 pounds per ton) and total organic chloride (TOCl) of less than 1 (2) and preferably less than 0.4 (0.8) can be achieved.
  • the present invention relates to novel methods for delignifying and bleaching pulp while minimizing the degree of attack upon the cellulosic portion of the wood, thus forming a product having acceptable strength properties for the manufacture of paper and various paper products.
  • delignification and bleaching process For convenience in understanding the improvement over the prior art offered with the use of the presently disclosed delignification and bleaching process, provided below are the definitions of several parameters involved in the various stages in any delignification/bleaching process.
  • Consistency is defined as the amount of pulp fiber in a slurry, expressed as a percentage of the total weight of the oven dry fiber and water. It is sometimes also referred to as pulp concentration. The consistency of a pulp will depend upon operation of and the type of dewatering equipment used. The following definitions are based on those found in Rydholm, Pulping Processes , Interscience Publishers, 1965, pages 862-863 and TAPPI Monograph No. 27, The Bleaching of Pulp , Rapson, Ed., The Technical Association of Pulp and Paper Industry, 1963, pages 186-187.
  • Low consistency includes ranges up to 6%, usually between 3 and 5%. It is a suspension that is pumpable by an ordinary centrifugal pump and is obtainable using deckers and filters without press rolls.
  • Medium consistency is between about 6 and 20%. Fifteen percent is a dividing point within the medium-consistency range. Below 15% the consistency can be obtained by filters. This is the consistency of the pulp mat leaving a vacuum drum filter in the brownstock washing system and the bleaching system. The consistency of a slurry from a washer, either a brownstock washer or a bleaching stage washer, is 9-15%. Above about 15%, press rolls are needed for dewatering. Rydholm states that the usual range for medium consistency is 10-18%, while Rapson states it is 9-15%. The slurry is pumpable by special machinery even though it is still a coherent liquid phase at higher temperatures and under some compression.
  • Pulping is used in its conventional sense to refer to a digestion of lignocellulosic material to form brownstock. Pulping would include, for example, Kraft, the Kraft-AQ process and forms of extended delignification.
  • modified Kraft process is used herein to include extended delignification and all other modified Kraft processes with the exception of the Kraft-AQ process, since this process has achieved a special status and acceptance in the art and is separately known by that name. Also, the oxygen delignification step following completion of pulping will not be considered as an extended delignification; rather, we have chosen to call it a first step of a delignification process for bleaching or brightening the pulp.
  • the degree of delignification is normally used in connection with the pulping process and the early bleaching stages. It tends to be less precise when only small amounts of lignin are present in the pulp, i.e., in the later bleaching stages.
  • the brightness factor is normally used in connection with the bleaching process because it tends to be more precise when the pulp is lightly colored and its reflectivity is high.
  • the normal permanganate test provides a permanganate or "K No.” which is the number of cubic centimeters of tenth normal potassium permanganate solution consumed by one gram of oven dried pulp under specified conditions. It is determined by TAPPI Standard Test T-214.
  • pulp brightness This parameter is usually a measure of reflectivity and its value is expressed as a percent of some scale.
  • a standard method is GE brightness which is expressed as a percentage of a maximum GE brightness as determined by TAPPI Standard Method TPD-103.
  • K No. viscosity and GE brightness
  • the pulp After the oxygen delignification step, and prior to brightening, the pulp has been partially delignified to a K No. of about 5 to 10, preferably between about 7 to 10 for U.S. softwoods and about 5 to 7 for U.S. hardwoods.
  • This partially delignified pulp has a viscosity of above about 10, generally more than 13 and preferably, at least 14 (for softwood pulp) or 15 (for hardwood pulp).
  • This partially delignified material thus has good strength and suitable viscosity so that it can withstand the effects of ozone.
  • the partially delignified pulp is subjected to ozone to further delignify the pulp, thus reducing the K No. of the pulp to about 3 to 4 for both softwoods and hardwoods while increasing the GE brightness of the pulp to at least about 50-70%.
  • a GE brightness of about 54% or higher is typically achieved, while for hardwood pulp, values of about 63% or more are attained.
  • the brightness of the pulp is further increased by an alkali extraction and an additional bleaching step using chlorine dioxide or peroxide.
  • Fig. 1 sets forth, in schematic form, the various stages utilized in pulping, delignifying and brightening a pulp according to the invention.
  • the invention comprises a multi-stage process including the steps of:
  • the first stage in the method of the present invention wherein procedures can be utilized which improve the amount of lignin removed from the lignocellulosic material while minimizing the amount of degradation of the cellulose, is in the pulping step.
  • the particular pulping process used in the method of the invention is, to a large extent, dependent on the type of lignocellulosic materials and, more particularly, the type of wood which is used as a starting material.
  • the pulping liquor used in chemical pulping techniques may be recovered and reused in a manner well-known in the art. This step is typically followed by washing to remove most of the dissolved organics and cooking chemicals for recycle and recovery, as well as a screening stage in which the pulp is passed through a screening apparatus to remove bundles of fibers that have not been separated in pulping.
  • the Kraft process is generally acceptable for use with all woods as compared to the other noted processes, as the final pulps obtained from the Kraft process have acceptable physical properties, although the brownstock pulp is also darker in color.
  • the results obtained with conventional Kraft processes may be enhanced by the use of extended delignification techniques or the Kraft-AQ process. Moreover, these techniques are preferred for obtaining the greatest degree of reduction in K No. of the pulp without deleteriously affecting the strength and viscosity properties of the pulp.
  • the amount of anthraquinone in the cooking liquor should be an amount of at least about 0.01% by weight, based on the oven dried weight of the wood to be pulped, with amounts of from about 0.02 to about 0.1% generally being preferred.
  • the inclusion of anthraquinone in the Kraft pulping process contributes significantly to the removal of the lignin without adversely affecting the desired strength characteristics of the remaining cellulose. Also, the additional cost for the anthraquinone is partially offset by the savings in cost of chemicals in the subsequent Z m , E and D or P steps.
  • the next step in the method of the present invention concerns the portion of the bleaching process which primarily involves removal of the residual lignin from the brownstock pulp being processed.
  • this stage comprises an oxygen delignification step.
  • the solid materials removed in this stage are oxygenated materials which can, like the black liquor, be collected, concentrated, and then incinerated in an environmentally safe manner in a conventional recovery boiler. At least a portion of the liquid phase is recycled as illustrated in Fig. 1.
  • the oxygen delignification step can be conducted in the manner which allows for the removal of increased percentages of the remaining lignin in the brownstock pulp without causing an unacceptable corresponding decrease in the viscosity of the pulp.
  • the process which has been identified is practiced by treating the brownstock pulp from the pulping process at low to medium consistency, as described below, with the required amount of alkali necessary for the oxygen delignification step so as to ensure uniform application of the alkali, and thereafter raising the consistency and delignifying at high consistencies.
  • high consistency delignification is preferred, low or medium consistency oxygen delignification techniques may be utilized in place of high consistency delignification.
  • the high consistency oxygen delignification step is preferably carried out in the presence of an aqueous alkaline solution at a pulp consistency of from about 25% to about 35%, and even more preferably, at about 27%.
  • This improved process allows for the removal of at least 60% of the residual lignin from the brownstock pulp, compared to the 45-50% removable with conventional oxygen delignification steps, without the heretofore expected undesirable decrease in the relative viscosity. Because of the unique process capabilities of this modified process, it clearly constitutes the preferred oxygen process for use in the method of this invention.
  • the treatment step of the modified oxygen process (O m ) comprises substantially uniformly combining wood pulp, preferably Kraft brownstock pulp, with an aqueous alkaline solution while maintaining the consistency of the pulp at less than about 10% and preferably less than about 5% by weight.
  • the aqueous alkaline solution is preferably present in an amount sufficient to provide from about 0.5% to about 4% active alkali by weight after thickening based upon the oven dry pulp weight of the brownstock pulp, and even more preferably about 2.5% active alkali by weight after thickening based upon the oven dry weight of the brownstock pulp.
  • This step uniformly distributes the aqueous alkaline solution throughout the low consistency brownstock and ensures that substantially all the brownstock fibers are exposed to a uniform application of alkaline solution.
  • the brownstock pulp treated in this manner is not substantially delignified in the treatment step, but it is more effectively delignified in the subsequent high consistency oxygen delignification step than brownstock that is treated with alkaline solutions at high consistency according to the methods conventionally employed.
  • the localized inhomogeneities in the distribution of alkali in conventional high consistency pulp are avoided, thus eliminating attendant non-uniform oxygen delignification.
  • This homogeneous distribution step thus preferably comprises uniformly combining the pulp with an aqueous alkaline solution for at least about 1 minute and preferably no more than about 15 minutes. It is believed that treatment times of less than about 1 minute will not generally provide sufficient time to attain substantially uniform distribution, whereas treatment times in excess of about 15 minutes are not expected to produce substantial further benefit.
  • the preferred alkaline treatment of pulp according to the present invention may be carried out over a wide range of temperature conditions.
  • the treatment step is carried out at a temperature of from about room temperature to about 65°C (150°F), with temperatures ranging from about 33°C (90°F to about 65°C (150°F) being even more preferred.
  • Atmospheric pressure or elevated pressure may be employed.
  • the treatment step is completed when the aqueous alkaline solution is substantially uniformly distributed throughout the low consistency pulp.
  • the amount of aqueous alkaline solution present in the treatment step can vary greatly according to the particular process parameters of the delignification reaction.
  • the amount of the alkaline solution effective for the purpose of the present invention will depend primarily upon the extent of delignification desired in the oxygen bleaching step and the strength of the particular solution being used.
  • the aqueous alkaline solutions preferably used comprise a sodium hydroxide solution having a concentration of from about 20 to about 120 g/l. This solution is mixed with the low consistency pulp, so that the overall mixture has a concentration of alkaline material of between about 6.5 and 13.5 g/l, and preferably around 9 g/l.
  • a uniform distribution of such alkaline material is obtained throughout the pulp.
  • an aqueous sodium hydroxide solution is added to the low consistency pulp in an amount sufficient to provide from about 15% to about 30% by weight of sodium hydroxide based on dry pulp weight.
  • alkaline sources having an equivalent sodium hydroxide content such as oxidized white liquor from the conventional Kraft recovery and regeneration cycle, may also be employed.
  • the consistency of the treated pulp is increased to greater than about 20%, preferably from about 25% to about 35%.
  • Several methods are available and well known in the art for increasing the consistency of the pulp, such as pressing the wood pulp to remove liquid therefrom.
  • oxygen delignification is conducted on the high consistency pulp.
  • Methods are available and well known in the art for dissolving gaseous oxygen into the liquid phase of high consistency pulp to affect delignification thereof. It is contemplated that any of these well known methods are adaptable for use according to the present invention. It is preferred, however, that oxygen delignification according to the present invention comprise introducing gaseous oxygen at about 551600 to 689500 N/m2 (80 to about 100 psig) into the liquid phase of the high consistency pulp while maintaining the temperature of the pulp between about 90°C and 130°C.
  • the average contact time between the high consistency pulp and the gaseous oxygen is preferably from about 20 minutes to about 60 minutes.
  • the present preferred process unexpectedly provides an increase of at least 20% in delignification compared to prior art delignification processes: i.e., from 50% to at least about 60% reduction of the K No. for the incoming pulp. Reductions of 70% and more can even be achieved with minimal cellulose degradation. The avoidance of deterioration of the cellulose component of the pulp is evident by the minimal change in viscosity of pulp which is treated in accordance with the present invention.
  • pulp K Nos. for the particular pulp range from about 10-26 depending upon the type of wood (e.g., for Kraft pulping, about 10-14, target 12.5 for hardwood and about 20-24, target 21, for softwood), while after oxygen delignification, the K No. is generally in the range of about 5-10.
  • a processing scheme for carrying out the method of the present invention is depicted in schematic form in Fig. 2.
  • the steps depicted therein represent a preferred operating system that tends to maximize certain benefits of the present invention.
  • Wood chips 2 are introduced into a digester 4 where they are cooked in a liquor such as a liquor of sodium hydroxide and sodium sulfide.
  • the cooking unit 4 produces a Kraft brownstock 8 and a black liquor 6 containing the reaction products of lignin solubilization.
  • the brownstock is treated in washing units comprising, preferably, blow tank 10 and washer 12 where residual liquor contained in the pulp is removed.
  • washing units comprising, preferably, blow tank 10 and washer 12 where residual liquor contained in the pulp is removed.
  • Many methods are available and well known in the art for washing brownstock, such as diffusion washing, rotary pressure washing, horizontal belt filtering, and dilution/extraction. These methods are all within the scope of the present invention.
  • screening of brownstock is often done either before or after the washing steps in order to
  • the washed brownstock is introduced into a treatment unit 14 where it is treated with an alkaline solution and maintained at a consistency of less than about 10% and preferably less than about 5%.
  • the process of the present invention preferably includes means for introducing make-up caustic 16 into the treatment stage to maintain the desired caustic application level.
  • the treated pulp 18 is forwarded to a thickening unit 20 where the consistency of the pulp is increased, by pressing for example, to at least about 20% by weight and preferably to about 25% to about 35%.
  • the liquid 22 removed from the thickening unit 20 is preferably returned to washing unit 12 for further use.
  • the high consistency "pressed" brownstock 24 produced in the thickening unit 20 is forwarded to the oxygen delignification reactor vessel 26 where it is contacted with gaseous oxygen 28.
  • the delignified brownstock 30 is preferably forwarded through blow tank 32 and then to a second washing unit 34 wherein the pulp is washed with water to remove any dissolved organics and to produce high quality, low color pulp 36. At least a portion of the effluent 38 from this washing step is preferably returned to washing unit 12 for use therein.
  • the effluent 13 from washing unit 12 may be recycled alone or optionally with all or a portion of effluent 38, to either the blow tank 10 or ultimately black liquor line 6.
  • the partially delignified pulp obtained after oxygen delignification may be screened to remove fiber bundles from the pulp that have not separated for further treatment such as mechanical grinding. From here, pulp 36 could be sent to subsequent bleaching stages to produce a fully bleached product.
  • Kraft pulping of the wood may be carried out, followed by the modified low-consistency alkali treatment/high consistency oxygen delignification procedure (O m ) described above.
  • O m oxygen delignification procedure
  • this combination results in a pulp with a K No. of about 8 to 10, preferably 9, and a viscosity of greater than about 13 to 14.
  • a conventional oxygen delignification step i.e., 0, high consistency alkaline treatment followed by high consistency oxygen delignification
  • Kraft AQ pulping it is also possible to use extended delignification processes, followed by a standard oxygen delignification step to achieve pulp with the desired properties.
  • extended delignification processes such as Kamyr MCC, Beloit RDH or the Sunds Cold Blow Cooking process, as described in the Background Art section of this specification, followed by conventional oxygen delignification.
  • pulping and oxygen delignification steps can be used in combination as long as they achieve the above K No. and viscosity values prior to the ozone step.
  • the ozone consumption may be reduced by using a number of alternate routes, such as standard kraft cooking followed by a modified oxygen delignification step (O m ), or modified kraft pulping with extended delignification (such as Kamyr MCC, Beloit RDH or Sunds Cold Blow) followed by a conventional oxygen delignification step (O), or by Kraft AQ cooking followed by a conventional oxygen delignification step (O) as discussed above.
  • alternate routes such as standard kraft cooking followed by a modified oxygen delignification step (O m ), or modified kraft pulping with extended delignification (such as Kamyr MCC, Beloit RDH or Sunds Cold Blow) followed by a conventional oxygen delignification step (O), or by Kraft AQ cooking followed by a conventional oxygen delignification step (O) as discussed above.
  • the advantages of using the modified high consistency oxygen delignification bleaching step (O m ) described above are clearly illustrated by comparison of the K Nos. and viscosities obtained using southern softwoods to related processes under otherwise substantially identical process conditions.
  • the resulting pulps obtained will typically have a K No. of about 12 to 14 and a viscosity of about 15. This K No. is too large to permit later delignification using the ozone stage of the present invention.
  • the use of conventional Kraft pulping with the modified high consistency oxygen bleaching surprisingly results in a pulp having a K No. of less than about 9, while the viscosity of the pulp is above about 12 to 14. This preferred pulp K No. permits utilization of the ozone delignification bleaching stage of the invention.
  • the next step in the method of this invention is ozone delignification and bleaching of the oxygen-delignified brownstock pulp.
  • This ozonation takes place in an ozone reactor which is described below in detail and illustrated in Figs. 2, 3 and 3A.
  • the pulp Prior to treatment of the pulp with the ozone, the pulp is conditioned so as to ensure the most effective selective delignification of the pulp and to minimize the chemical attack of the ozone on the cellulose.
  • the incoming pulp 36 is directed into a mixing chest 40, where it is diluted to a low consistency.
  • An acid 42 such as sulfuric acid, formic acid, acetic acid or the like, is added to the low consistency pulp to decrease the pH of the pulp in mixing chest 40 to the range of about 1 to 4 and preferably between 2 and 3.
  • the pH is adjusted as described above since it is known that the relative effectiveness of ozone bleaching of pulps is dependent upon the pH of the pulp mixture. Lower pH values do not appear to have any beneficial effect on the further processing of the pulp, whereas increasing the pH to above about 4 to 5 causes a decrease in viscosity and an increase in ozone consumption.
  • the acidified pulp is treated with chelating agent 44 to complex any metals or metal salts which may be present in the pulp.
  • This chelating step is used to render such metals non-reactive or harmless in the ozone reactor so that they will not cause breakdown of the ozone, thus decreasing the efficiency of the lignin removal and also reducing the viscosity of the cellulose.
  • Chelating agents are known per se and include, for example, polycarboxylate and polycarboxylate derivatives such as the di-, tri-, and tetra-carboxylates, amides, and the like.
  • Preferred chelating agents for this ozone treatment include DTPA, EDTA and oxalic acid. Amounts of these chelating agents ranging from about 0.1% to about 0.2% by weight of oven dry pulp are generally effective, although additional amounts may be needed when high metal ion concentrations are present.
  • the effectiveness of the ozone bleaching process is controlled by a number of inter-related process parameters, including the pH level and the amount of metal salts in the pulp as discussed above.
  • Another very important parameter is the consistency of the pulp during the ozone bleaching process.
  • the pulp which is to be bleached must contain sufficient water so that the water exists as a continuous phase through the individual fibers, that is, the fiber should be sufficiently saturated with water.
  • the water in the fiber allows the transfer of the ozone from the gaseous ozone atmosphere to both treat the outer surface of the fibers, and possibly more importantly, for the ozone to be transferred via the water phase to the less accessible interior portion of the individual fibers and thereby provide more complete removal of lignin from the fibers.
  • the consistency should not be so low that the ozone is diluted and tends to chemically break down rather than bleach the pulp.
  • the preferred range of consistency especially for southern U.S. softwood, has been found to be between about 28% and about 50%, with the optimum results being obtained at between about 38% and about 45%. Within the above ranges, preferred results are obtained as indicated by the relative amount of delignification, the relatively low amount of degradation of the cellulose, and the noticeable increase in the brightness of the treated pulps.
  • the reaction temperature at which the ozone bleaching is conducted is likewise an important controlling factor in the process of the present invention.
  • the ozone step can be effectively conducted at temperatures up to a certain critical temperature, at which the reaction commences to cause excessive degradation of the cellulose.
  • This critical temperature will vary significantly depending upon the particular type of wood employed to form the pulp and the history of the prior treatment of the pulp.
  • the maximum temperature of the pulp fiber at which the reaction should be conducted should not exceed the temperature at which excessive degradation of the cellulose occurs, which with southern U.S. softwood is a maximum of about 49-65°C (120°F - 150°F).
  • the ozone gas which is used in the bleaching process may be employed as a mixture of ozone with oxygen and/or an inert gas, or can be employed as a mixture of ozone with air.
  • the amount of ozone which can satisfactorily be incorporated into the treatment gases is limited by the stability of the ozone in the gas mixture.
  • Ozone gas mixtures which typically contain about 1-8% by weight of ozone in an ozone/oxygen mixture, or about 1-4% ozone in an ozone/air mixture, are suitable for use in this invention.
  • the higher concentration of ozone in the ozone gas mixture allows for the use of relatively smaller size reactors and shorter reaction time to treat equivalent amounts of pulp, thereby lessening the capital cost required for the equipment.
  • ozone gas mixtures containing lower amounts of ozone tend to be less expensive to produce and may reduce operating costs.
  • a further controlling factor is the relative weight of the ozone used to bleach a given weight of the pulp. This amount is determined, at least in part, by the amount of lignin which is to be removed during the ozone bleaching process, balanced against the relative amount of degradation of the cellulose which can be tolerated during ozone bleaching. In accordance with the preferred method of this invention, an amount of ozone is used which will react with about 50% to 70% of the lignin present in the pulp. The entire amount of lignin in the pulp is not removed in the ozone bleaching step as evidenced by the K No.
  • the amount of ozone added typically is about from 0.2% to about 1% to reach the lignin levels of a 3-4 K No. Higher amounts may be required if significant quantities of dissolved solids are present in the system.
  • the time of the reaction used for the ozone bleaching step is determined by the desired rate of completion of the ozone bleaching reaction as indicated by complete or substantially complete consumption of the ozone which is utilized. This time will vary depending upon the concentration of the ozone in the ozone gas mixture, with relatively more concentrated ozone mixtures reacting more quickly, and the relative amount of lignin which it is desired to remove. The time required is preferably less than two minutes, but the procedure may take substantially longer depending on other reaction parameters.
  • the pulp is bleached uniformly. This feature is obtained in part, by comminution of the pulp into discrete floc particles of a size which is of a sufficiently small diameter and of a sufficiently low bulk density so that the ozone gas mixture will completely penetrate a majority of the fiber flocs, i.e., which comprise agglomerations of fibers. During comminution it is not feasible to completely separate the pulp fibers into distinct fibers.
  • the floc particles resulting from comminution have a relatively compacted central core surrounded by a plurality of outwardly extending fibers.
  • the floc particle size is determined by measuring what was determined to be the smallest diameter of this relatively unfluffed central core.
  • Bleaching uniformity is to a large extent also dependent on certain of the other process parameters, but it has been found that if the floc particle size is limited to a maximum of 5mm, and preferably even less --for example, 3mm-- that uniform treatment of a substantial majority of these particles can readily be achieved, as evidenced by observation of an insignificant number of darker underbleached floc centers. Where the floc particle size was greater than about 5mm, bleaching was non-uniform, as evidenced by a majority of darker unbleached floc centers. Therefore it is important to achieve sufficient comminution so that a majority of the flocs measure below an average of about 5 mm for uniform ozone treatment thereof.
  • a still further important process parameter is that during the ozone bleaching process the particles to be bleached should be exposed to the ozone bleaching mixture by mixing so as to allow access of the ozone gas mixture to all surfaces of the flocs and equal access of the ozone gas mixture to all flocs.
  • the mixing of the pulp in the ozone gas mixture gives superior results with regard to uniformity as compared to the results obtained with a static bed of flocs wherein some of the flocs are isolated from the ozone gas relative to other flocs and thereby bleached less than other flocs.
  • the movement of the flocs so as to expose them to the ozone gas mixture causes uniform treatment of the flocs with respect to each other. This treatment results in the desired amount of lignin being removed uniformly from the pulp without excessive deterioration of the cellulose in the fibers which comprise the flocs.
  • the control of the ozone treatment in accordance with this invention by use of a controlled particle size and by turbulent movement during ozone treatment has been found to result in a final pulp typically having less than about a 5% variation in GE brightness, K No. and viscosity.
  • the present application designates such a non-uniform ozone treatment with the letter "Z".
  • the use of a modified ozone technique according to the present invention, as discussed above, in which the fibers are comminuted to a size of about 5 mm or less and are properly and uniformly contacted with the ozone gas stream, has been designated herein as "Z m ".
  • Pulp exiting the ozone reactor has a GE brightness of about at least 50 percent and generally around 50 to 70 percent, with hardwoods usually being above about 55 percent.
  • the pulp for hardwoods or softwoods also has a K No. of between about 3 and 4 (target of 3.5), which is entirely satisfactory for pulp at this stage of the process.
  • washed pulp 36 is directed to mixing chest 40 where it is treated with an acid 42 and a chelating agent 44.
  • the acidified, chelated low-consistency pulp 46 is introduced into thickening unit 48 for removing excess liquid 50 from the pulp, such as a twin roll press wherein the consistency of the pulp is raised to the desired level. At least a portion of this excess liquid 50 may be recycled to mixing chest 40, with a remaining portion being directed to blow tank 32.
  • the resulting high consistency pulp 52 is then passed through screw feeder 54 which acts as a gas seal for the ozone gas and thereafter through a comminuting unit 56, such as a fluffer, where the pulp is comminuted to pulp fiber flocs 60 of a pre-determined size which, as noted above, should measure about 5 mm or less in size.
  • the comminuted particles are then introduced into a dynamic ozone reaction chamber 58 which, as illustrated, is a conveyor 62 powered by motor 64.
  • Conveyor 62 is specifically designed for mixing and transporting the pulp particles 60 so as to allow the entire surface of the particles to become exposed to the ozone gas mixture 66 during movement of the pulp.
  • pulp fiber flocs 60 after treatment are allowed to fall into dilution tank 68.
  • Fig. 3 is a cross-sectional view through ozone reactor 58 illustrating the arrangement of the pulp particles 60 as they are carried through the reactor by conveyor 62.
  • Fig. 3A is a cross-sectional view of a preferred conveyor utilizing a paddle-like arrangement to move the comminuted particles through reaction chamber 58.
  • Fig. 2 shows the pulp being treated with ozone cocurrently with the ozone-gas mixture.
  • the portion of the pulp which has been bleached to the greatest extent may initially be contacted with the newly introduced ozone mixture containing the maximum amount of ozone by passing the ozone-containing gas in a direction counter-current to the flow of pulp 60.
  • the pulp entering the reactor has the highest lignin content and initially contacts the exiting, nearly exhausted ozone mixture, thereby providing the optimum chance to consume virtually all of the ozone. This is an efficient method for stripping ozone from the ozone/oxygen or ozone/air mixture.
  • the remaining spent ozone gas 70 can be recovered from dilution tank 68.
  • dilution water 72 which also serves as an ozone gas seal, is added to reduce the consistency of the pulp to a low level to facilitate movement of the bleached pulp 74 through the subsequent process steps.
  • the spent ozone gas 70 from dilution tank 68 is directed to a carrier gas pretreatment stage 76 where a carrier gas 78 of oxygen or air is added.
  • This mixture 80 is directed to ozone generator 82 where the appropriate amount of ozone is generated to obtain the desired concentration.
  • the proper ozone/air mixture 66 is then directed to ozone reactor 58 for delignification and bleaching of the pulp.
  • the substantially delignified pulp 74 is again thoroughly washed in washer 84 as shown in Fig. 2 and at least a portion of the water 86 which is recovered is recycled to washing unit 34 of the process, thereby producing major environmental benefits from the elimination of sewered liquid.
  • the bleached low consistency pulp 74 after ozonation will have a reduced amount of lignin, and therefore, a lower K No. and an acceptable viscosity.
  • the exact values for the K No. and the viscosity which are obtained are dependent upon the particular processing to which the pulp has been subjected.
  • a southern U.S. softwood pulp which is pulped with a conventional Kraft method, initially delignified by modified high consistency oxygen delignification (O m ), and subsequently further delignified with ozone, preferably by a modified uniform ozone treatment (Z m ), will typically have a K No. of about 3-4 and a viscosity of about 10.
  • softwood pulp which is subjected to Kraft AQ pulping and then to modified high consistency oxygen bleaching (O m ) and modified uniform ozone treatment (Z m ) will typically have a K No. of about 2 and a viscosity of greater than about 12.
  • the resulting pulp 74 will be noticeably brighter than the starting pulp.
  • southern softwood after the pulping process, has a GE brightness of about 15% to 25%; after the oxygen bleaching process, a GE brightness of about 25% to 45%; and after the ozone bleaching process, a GE brightness of about 50% to 70%.
  • the washed pulp 88 from the ozone stage is then combined with a sufficient amount of alkaline material 90 in extraction vessel 92 to effect extraction.
  • pulp 88 is subjected to an aqueous alkaline solution for a predetermined time and at a predetermined temperature correlated to the quantity of alkaline material to solubilize a substantial portion of any lignin which remains in the pulp, in vessel 92.
  • This extraction process also increases the brightness of the pulp, typically by about 2 GE brightness points.
  • the alkali treated pulp 94 is directed to washing unit 96, the aqueous alkaline solution is washed from the pulp so as to remove substantially all of the solubilized lignin from the pulp, thus forming a substantially lignin-free pulp.
  • This step is well known to those skilled in the art and no further comment is deemed necessary here.
  • the examples illustrate the preferred extraction parameters for this step of the process. At least a portion of the alkaline solution 98 which is recovered is recycled to washing unit 84. Again, major environmental benefits are achieved from the elimination of sewering of this solution.
  • the extraction step can be augmented by incorporating an oxygen treatment within the caustic extraction step (E o ).
  • E o an oxygen treatment within the caustic extraction step
  • the pulp is subjected to brightening bleaching, which is primarily intended to convert the chromophoric groups on the lignin remaining in the pulp into a colorless state.
  • the brightening bleaching of the ozone-bleached and extracted pulp can be performed using a variety of materials. As illustrated in Fig. 2, the washed pulp 100 is combined with the chosen bleaching agent 102 in bleaching vessel 104.
  • the preferred bleaching agent is chlorine dioxide or peroxide.
  • the pulp 106 is washed with water 114 in washing unit 108 and the effluent is either recycled 110 or sewered 112. When recycled, at least a portion of wash water stream 110 is directed to washing unit 96.
  • the resultant bleached pulp 116 may then be collected and used in a variety of applications.
  • chlorine dioxide D
  • Fig. 1 One of the principal materials which has heretofore been used, and which is generally highly effective, is chlorine dioxide (D) (see Fig. 1).
  • an appropriate amount of chlorine dioxide enables high-strength pulps having a GE brightness value greater than about 80% to be obtained. Since the pulps entering the chlorine dioxide stage are relatively low in lignin, the chlorine dioxide brightening bleaching can be carried out in the presence of only from about 0.25% to about 1% of chlorine dioxide based on the oven dry weight of the pulp.
  • the chlorine dioxide which is utilized in the brightening process should preferably be prepared by a process which is free from elemental chlorine.
  • chlorine dioxide which does contain a minor amount of elemental chlorine can be used without any substantial increase in the relative amount of undesirable pollutants because of the relatively low amount of lignin present in the ozone-bleached pulp.
  • the effluent from the final bleaching step of this invention when using chlorine dioxide is exceptionally low and can be discharged safely as shown in Fig. 2.
  • the stream can, however, be further purified by being treated with a membrane filtration process such as reverse osmosis.
  • a membrane filtration process such as reverse osmosis. This technique provides a clean filtrate that can be recycled back to previous bleaching stages for further use. This has the benefit of reducing fresh water usage.
  • the concentrated chloride streams that result from the membrane filtration are relatively low in volume.
  • the brightening bleaching may be conducted with hydrogen peroxide, as also shown in Fig. 1.
  • This technique provides a completely chlorine-free bleaching cycle (such as an O m Z m EP sequence), wherein no chlorinated materials are formed in the bleaching process and the liquid extraction product can be readily recycled without the necessity for cumbersome filtration techniques.
  • peroxides as the bleaching agent, however, the K No.
  • pulp of acceptable brightness i.e., a GE Brightness of greater than about 80%, since peroxide is not as effective at bleaching as is chlorine dioxide. Where a completely chlorine/chlorine dioxide-free process is desired, however, peroxide provides acceptable results.
  • Typical peroxide brightening agents and their use in this step are conventional, and one skilled in the art would know the appropriate concentration, types and use of such peroxide agents. Hydrogen peroxide is preferred.
  • the washed, further brightened pulp has a GE brightness of between about 70 and 95%, and preferably between about 80 and 95%. Also, the physical properties of this pulp are commensurate with those obtainable by pulp produced by conventional CEDED or OC/DED processes.
  • O m Z m ED instead of O m Z m ED, one may use the O m Z m EP process of the invention to obtain additional substantial advantages over the prior art in that no chlorinated compounds whatsoever are produced. This enables all of the effluent to be recycled without experiencing the problems of chloride build-up in the process wash water streams.
  • the process of the present invention achieves substantial advantages with respect to reductions in effluent volume, color, COD, BOD and chlorinated organics. Moreover, since the effluent used in the washing steps contains significantly reduced chloride levels compared to prior art processes which utilize chlorine, the washing unit vents will not be carrying chlorinated organic compounds or gases which require treatment prior to discharge.
  • Loblolly pine chips were lab batch cooked according to the conditions in Table I to produce a conventional kraft pulp.
  • the resulting pulp had a K No. of 22.6 and a viscosity of 27.1 cps.
  • the kraft pulp was then subjected to conventional oxygen treatment (Tables II and V) followed by bleaching to a final target brightness of 83 GEB using both a conventional OC/DED sequence (Table III) and an OZ m ED bleaching sequence (Tables IV and V).
  • the ozone bleaching stage was run at 35% consistency with an ozone application of 0.61%.
  • OZ m ED bleaching under these conditions produced a pulp having acceptable strength properties compared to an 83% GE target brightness OC/DED baseline pulp.
  • the OZ m ED pulp had marginal viscosity of 9.7 cps.
  • the strength properties were measured on an OZ m ED pulp where the final D-stage application was 2.5%.
  • Target brightness was reached only with an excessive chlorine dioxide charge.
  • the OZ m E pulps response to chlorine dioxide treatment shows that higher brightness can only be achieved by significantly increasing the ozone application, which then causes significant viscosity and strength loss of the pulp.
  • a kraft/AQ brownstock was prepared in a laboratory batch digester from loblolly pine chips as described in Table VIII.
  • the K No. of the resulting brownstock was 18.3 and the viscosity was 20.6 cps.
  • the Kraft/AQ pulping conditions produced a pulp having a significantly lower lignin content than in Example 1 as evidenced by the K No., without unacceptable deterioration of pulp strength as evidenced by the viscosity.
  • the Kraft/AQ brownstock was then subjected to further bleaching using the conventional OC/DED sequence and the OZ m ED sequence as shown in Tables II, III, IV and V to a target brightness of 83% GEB.
  • Use of the Kraft AQ pulping technology achieved the goal of producing a starting pulp with a low K No., having acceptable viscosity properties, for the ozone bleaching sequence.
  • the ozone bleaching stage was run at 35% consistency with an ozone application of 0.35% and 1.6% C102 was used in the final D stage to reach target brightness.
  • a pine Kraft brownstock having a K No. of about 24 was pressed to a consistency of about 30-36% by weight to produce a high consistency mat.
  • the mat of brownstock was sprayed with a 10% sodium hydroxide solution in an amount sufficient to produce approximately 2.5 weight percent sodium hydroxide based on pulp dry weight.
  • Dilution water was added in an amount sufficient to adjust the brownstock mat to about 27% consistency.
  • the high consistency brownstock mat was then subjected to oxygen delignification using the following conditions: 110°C, 30 minutes, 551600 N/m2 (80 psig) 02.
  • Pine Kraft brownstock of Example 3 was introduced into a treatment vessel along with a sufficient volume of 10% NaOH solution to effect a 30% NaOH addition based on oven-dried pulp. Sufficient dilution water was added to obtain a brownstock consistency of about 3% by weight in the treatment vessel.
  • the brownstock and the aqueous sodium hydroxide solution were uniformly mixed at room temperature by a ribbon mixer for about 15 minutes.
  • the treated brownstock was then pressed to a consistency of about 27% by weight. After pressing, the sodium hydroxide on the fiber equaled about 2.5% as in Example 3.
  • the treated brownstock was then delignified according to the oxygen delignification procedure described in Example 3. A comparison is shown in Table XI.
  • Pulp produced from pine in accordance with the O m process of Example 4 of the present invention is compared to that produced conventionally (0) (i.e., with no low consistency alkaline treatment step).
  • the average caustic dosage for high consistency oxygen delignification of brownstock pulp was found to be 22,5 kg (45 pounds) per oven dried tonne (ton) (1b/t) or 2.3%. At that level, the average reduction in K No. across the oxygen delignification reactor was 10 units.
  • an average K No. drop during delignification was found to be 13 units: a 30% improvement compared to the conventional process.
  • Delignification selectivity can also be expressed as the change in viscosity versus the change in K No. between brownstock and the corresponding treated pulps.
  • Oxygen delignification selectivity decreases rather rapidly when the change in K No. begins to exceed 10 K No. units. The decrease in selectivity is observed as a rapid increase in the change in viscosity for a given change in K No.
  • the corresponding change in viscosity is expected to be 12 to 13 cps.
  • the change in viscosity was found to be about 6 cps.
  • the change in viscosity per change in K No. appears to be constant up to a 16 to 17 K No. unit change for pulps obtained using the preferred treatment process of the invention. The results are shown in Table XII.
  • a southern pine pulp was produced in an operating 600 TPD fine paper mill using the modified oxygen delignification process (0 m ) having the conditions of Table II in combination with the uniform alkali treatment as described in Examples 4 and 5 and the conditions as shown in Table XIII below.
  • the O-stage pulp produced by this novel method had the properties needed to successfully complete the bleaching process using ozone, as described in the embodiment of this invention.
  • the oxygen stage pulp had a K No. of 7.9 (compared to a typical conventional O-stage K No. of about 12). Viscosity of the delignified pulp was 15 cps and was not significantly reduced by the high degree of delignification obtained by the use of the modified oxygen process.
  • This pulp could then be further bleached with ozone, utilizing any of the numerous process embodiments described herein to produce a pulp having acceptable final strength and optical properties.
  • the ozone bleaching stage was carried out in a pilot plant reactor as shown in Fig. 2. Conditions of operation of the pilot plant reactor are shown in Table XV.
  • the ozone bleached pulp generated in the pilot plant reactor was then treated in extraction and chlorine dioxide stages in the laboratory, as described in Table V above, to produce a final bleached pulp product at target brightness.
  • a final D stage charge of only 1.0 % C102 was used on the fiber.
  • a southern hardwood fiber from mixed hardwood comprising predominantly gum and oak, was bleached with ozone in the pilot plant described in Example 6 above.
  • a conventional oxygen stage pulp produced in the 600 TPD mill was treated with ozone in the pilot plant reactor.
  • the oxygen stage pulp had a K No. of 5.7 and a viscosity of 14.1.
  • the ozone reactor treatment conditions are shown in Table XIX.
  • the pilot plant Z m stage pulp was then final bleached by conventional E and D stages as shown in Table XX to a target brightness.
  • a D-stage C102 charge of only 0.35% was used on OD fiber.
  • Strength and brightness properties were acceptable compared to the baseline as shown in Tables XXI and XXII.
  • Delignification selectivity can also be expressed in terms of the change in viscosity versus the change in K No. between brownstock and the corresponding modified oxygen treated pulps.
  • the average change in viscosity was 4 cps for pulps produced by the conventional process.
  • the change in K No. for the same change in viscosity for pulps produced by the modified oxygen method was 7 units.
  • the OC/DED effluent is the C/D, E and D combined effluent and the OZ m ED effluent is the D stage effluent, each representing the several effluent properties.
  • Table XXVII the ozone bleaching sequence substantially reduces the environmental impact of the effluent from the bleaching process.
  • EPA method 110.2 was used. From this data, it can be seen that the present invention provides a discharge effluent having a color of no greater than about 1 kg/tonne (2 pounds per ton), a BOD5 value of no greater than about 1 kg/tonne (2 pounds per ton) and an amount of total organic chloride of no greater than about 1 (2) and preferably less than about 0.4 (0.8).
  • Southern pine kraft pulp was bleached using three modifications of the basic OZED sequence.
  • the pulp was bleached as in Tables IV and V with conventional oxygen, modified ozone, caustic extraction and chloride dioxide as produced in the R-3 sequence with a Cl02/Cl2 ratio of 6:1.
  • the modified oxygen process (O m ) was utilized and again the final stage used an R-3 type of chlorine dioxide.
  • the modified oxygen process (O m ) was used once again, and an R-8 chlorine dioxide solution was employed with 95:1 ratio in the final stage.
  • Table XXVIII demonstrates the positive environmental impact offered with the use of the modified oxygen process (O m ).
  • the R-8 bleach liquor also had a positive effect.
  • Southern loblolly pine pulps were prepared by the kraft and kraft/AQ pulping processes as described in Tables I and VIII above. These pulps were further subjected to conventional and modified oxygen delignification as described in Examples 4 and 5 to show the effect of combining these processes (for extending delignification with minimal impact on pulp strength) on the ozone bleaching sequence. As can readily be seen from Table XXIX, these processes produce an additive effect. Extremely low 0 m Z m E K Nos. can be reached with little impact on final viscosity. Conversely, the amount of ozone needed to reach a target 0 m Z m E K No. of about 3.5 for the previously described ozone bleaching process can be substantially reduced. In addition, the additive effect produces a southern pine pulp that can be fully bleached by an 0 m Z m EP process where a very low 0 m Z m E K No. is required for a functional peroxide stage.
  • Wood based dirt was refined and added to the OZ m ED starting brownstock at a level of 0.75% by weight to examine the ability of this sequence to remove dirt compared to CEDED and OC/DED bleaching. Dirt properties of the three sequences, measured as Effective Black Area, bark and shives, were equivalent.
  • Bleached pulps can be produced over a wide range of product brightnesses, utilizing appropriate combinations of ozone and chlorine dioxide charges to minimize environmental impacts and operating costs. As shown in Table XXX below, products having brightness from above 65% GEB can be produced by various combinations of ozone and chlorine dioxide while retaining reasonable strength properties.

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Claims (128)

  1. Procédé pour la préparation d'une pâte pratiquement uniformément blanchie et formée d'une matière de lignine-cellulose, comprenant la préparation d'une pâte de transition avec une teneur réduite en lignine par la décomposition chimique (4) de la matière de lignine-cellulose suivie d'une décomposition par de l'oxygène (26) de la pâte alors obtenue, lequel procédé se caractérise par les étapes suivantes:
    a) le pH de la pâte de transition est réglé (42) dans la plage d'environ 1 à 4.
    b) la consistance de la pâte de transition est réglée (48) à une grande valeur d'environ 20 à 50 p.c.
    c) la pâte de transition est broyée (56) en des particules discrètes dont la majorité a des dimensions de moins de 5 mm environ.
    d) la pâte de transition obtenue après les étapes a), b), c) est soumise à une extraction de lignine en mélangeant la pâte dans un mouvement tourbillonnaire avec une atmosphère de gaz comprenant de l'ozone dans une zone de réaction dynamique (58), et ce pendant un temps et une température suffisants pour la pénétration de l'ozone dans pratiquement toute la pâte de transition afin d'entrer en réaction avec celle-ci, lorsque ladite pâte est transportée (62) à travers presque toute la zone de réaction, ce qui permet d'obtenir une extraction continuée et pratiquement uniforme de la lignine d'une partie considérable de la pâte.
  2. Procédé selon la revendication 1 comprenant une décomposition chimique de la matière de lignine-cellulose par la trituration Kraft, la trituration Kraft AQ, ou une extraction de lignine prolongée.
  3. Procédé selon la revendication 1 ou 2, l'étape d'extraction oxygène-lignine comprenant la formation d'une pâte de petite à moyenne consistance; le traitement de la pâte ayant une petite à moyenne consistance avec une solution aqueuse d'une matière alcaline pendant un certain temps et à une certaine température dépendant de la quantité de matière alcaline afin de répartir également la matière alcaline dans la pâte de petite à moyenne consistance; l'augmentation de la consistance de la pâte jusqu'à une valeur de 20 p.c. à 50 p.c. et la soumission de la pâte de grande consistance qui en résulte à une extraction oxygène-lignine pour une grande consistance afin de réaliser la pâte de transition.
  4. Procédé selon la revendication 1, 2 ou 3, le degré de blancheur GE final de la pâte blanchie étant au moins 50 p.c., sa viscosité étant plus grande que 10 cps environ, la quantité de lignine étant indiquée par un n° K de la pâte de transition d'environ 10 ou moins, et la viscosité de la pâte de transition étant plus grande que 13 cps environ.
  5. Procédé selon la revendication 1, 2, 3 ou 4, la matière de ligno-cellulose étant du "softwood" et le degré de blancheur GE final de la pâte blanchie étant au moins 50 p.c., sa viscosité étant plus grande que 10 cps environ, la quantité de lignine étant indiquée par un n° K de la pâte de transition et comprise entre environ 7 et 10, et la viscosité de la pâte de transition étant plus grande que 13 cps environ.
  6. Procédé selon la revendication 1, 2, 3, 4 ou 5, la matière de lignine-cellulose étant du "hardwood" et le degré de blancheur GE final de la pâte blanchie étant au moins 55 p.c., sa viscosité étant plus grande que 10 cps environ, la quantité de lignine étant indiquée par un n° K de la pâte de transition et comprise entre environ 5 et 8, et la viscosité de la pâte de transition étant plus grande que 13 cps environ.
  7. Procédé selon la revendication 4, 5 ou 6, la quantité de lignine se trouvant dans la pâte après l'extraction de lignine par de l'ozone étant indiquée par un n° K d'une pâte blanchie d'environ 3 à 4.
  8. Procédé selon la revendication 1, comprenant ensuite le blanchiment de la pâte après l'extraction ozone-lignine avec un agent augmentant le degré de blancheur afin d'augmenter le degré de blancheur GE de la pâte blanchie.
  9. Procédé selon la revendication 8, comprenant ensuite la combinaison de la pâte blanchie avec une quantité effective d'une matière alcaline dans une solution alcaline aqueuse à une certaine température, laquelle est liée à la quantité de matière alcaline, pour dissoudre une partie considérable de toute lignine restée dans la pâte blanchie, après quoi on fait une extraction d'une partie de la solution alcaline aqueuse pour éliminer de la pâte pratiquement toute la lignine déjà dissoute et pour former une pâte extraite avant de blanchir celle-ci avec un agent augmentant le degré de blancheur.
  10. Procédé selon la revendication 8, l'agent augmentant le degré de blancheur étant du dioxyde de chlore ou un peroxyde.
  11. Procédé selon la revendication 1, la matière de lignine-cellulose étant décomposée chimiquement pour la formation d'une pâte avec un premier n° K et une première valeur de viscosité, après quoi la pâte est soumise à une extraction de lignine avec de l'oxygène pour former une pâte partiellement libérée de lignine avec un deuxième n° K, plus petit que ledit premier n° K et suffisant pour continuer à extraire avec de l'ozone la pâte obtenue partiellement par l'extraction de lignine, avec maintien de la viscosité à un tel niveau que les composants de cellulose de cette pâte partiellement libérée de lignine ne sont pas corrodés chimiquement d'une manière significative par l'extraction oxygène-lignine; et
       la pâte partiellement libérée de lignine étant encore libérée de lignine par l'ozone pour obtenir une pâte en grande partie libre de lignine et avec un troisième n° K considérablement réduit en dessous du deuxième n° K de ladite pâte partiellement libérée de lignine et un degré de blancheur GE considérablement plus élevé que celui de la pâte partiellement libérée de lignine avec maintien de la viscosité et sans corrosion chimique agressive des composants de cellulose de la pâte pour éviter en grande partie une réduction de la consistance de la pâte.
  12. Procédé selon la revendication 11, la pâte partiellement libérée de lignine comprenant une quantité de lignine qui permet que la pâte après l'extraction de lignine avec de l'ozone obtienne un certain degré de blancheur GE et qu'elle ait également une viscosité qui soit suffisamment grande pour compenser la chute de viscosité lors de l'extraction ozone-lignine, par quoi la pâte pratiquement libre de lignine peut obtenir la consistance désirée.
  13. Procédé selon la revendication 11, comprenant ensuite la combinaison d'une pâte pratiquement libre de lignine et une quantité effective d'une matière alcaline dans une solution alcaline aqueuse à une certaine température dépendant de la quantité totale de matière alcaline, pour dissoudre une partie considérable de la lignine possiblement restée dans la pâte pratiquement libre de lignine, et d'extraire ensuite une partie de la solution alcaline aqueuse pour éliminer de la pâte pratiquement toute la lignine déjà dissoute et pour réaliser une pâte pratiquement libre de lignine.
  14. Procédé selon la revendication 13, comprenant ensuite le blanchiment de la pâte pratiquement libre de lignine jusqu'à un degré de blancheur qui est considérablement plus grand que celui de la pâte pratiquement libre de lignine.
  15. Procédé selon la revendication 11, la viscosité de ladite pâte pratiquement libre de lignine étant maintenue à une valeur plus élevée que 13 cps environ.
  16. Procédé selon la revendication 15, ladite pâte pratiquement libre de lignine étant maintenue à une diminution de viscosité d'environ 30 p.c. ou moins de la première valeur mentionnée.
  17. Procédé selon la revendication 11, la matière de lignine-cellulose étant un "hardwood".
  18. Procédé selon la revendication 17, ledit premier n° K étant compris entre environ 10 et 14.
  19. Procédé selon la revendication 17, ladite première valeur de viscosité étant comprise entre 21 et 28 cps.
  20. Procédé selon la revendication 17, ledit deuxième n° K étant compris entre environ 5 et 8.
  21. Procédé selon la revendication 20, ledit troisième n° K étant plus petit que 5 environ.
  22. Procédé selon la revendication 11, ladite matière de lignine-cellulose étant un "softwood".
  23. Procédé selon la revendication 22, ledit premier n° K étant compris entre 20 et 24.
  24. Procédé selon la revendication 22, ledit deuxième n° K étant compris entre environ 7 et 10.
  25. Procédé selon la revendication 11, le traitement d'extraction oxygène-lignine étant appliqué à une pâte ayant une consistance moyenne.
  26. Procédé selon la revendication 11,-l'étape d'extraction partielle de lignine comprenant ensuite:
       le traitement de ladite pâte avec une quantité de matière alcaline dans une solution alcaline aqueuse pendant un certain temps et à une certaine température dépendant de la quantité de matière alcaline pour obtenir une répartition pratiquement uniforme de la matière alcaline dans la pâte;
       l'augmentation de la consistance après l'achèvement de l'étape de traitement; et
       la soumission de la pâte ayant une consistance augmentée et comprenant de la matière alcaline à un traitement d'extraction oxygène-lignine pour une grande consistance afin de réaliser une pâte partiellement libre de lignine.
  27. Procédé selon la revendication 11, la viscosité de ladite pâte pratiquement libre de lignine étant maintenue à une valeur plus élevée que 10 cps.
  28. Procédé selon la revendication 27, ladite pâte pratiquement libre de lignine étant maintenue à une diminution de viscosité d'environ 30 p.c. ou moins de la viscosité de ladite pâte pratiquement libre de lignine.
  29. Procédé selon la revendication 11, l'étape d'extraction ultérieure de lignine comprenant en outre:
       l'augmentation de la consistance de ladite pâte partiellement libre de lignine;
       le broyage de la pâte ayant une consistance augmentée à une dimension de particules prédéterminée; et
       la mise en contact régulière de la pâte contenant des particules réduites avec ladite quantité effective d'ozone, lorsque la pâte avance au cours du procédé.
  30. Procédé selon la revendication 29, la dimension des particules de la pâte ayant une consistance augmentée étant réduite d'une telle manière qu'un contact uniforme avec l'ozone est facilité sans provoquer une détérioration importante des composants de cellulose dans la pâte.
  31. Procédé selon la revendication 30, la pâte étant broyée à environ 5 mm et parcourant le procédé d'une telle manière qu'on évite un traitement inégal de la pâte par l'ozone.
  32. Procédé selon la revendication 31, la pâte broyée coulant dans le même sens que l'ozone.
  33. Procédé selon la revendication 31, la pâte broyée coulant à contre-courant de l'ozone.
  34. Procédé selon la revendication 14, la pâte pratiquement libre de lignine étant blanchie avec du dioxyde de chlore.
  35. Procédé selon la revendication 14, la pâte pratiquement libre de lignine étant blanchie avec un peroxyde.
  36. Procédé selon la revendication 34 ou 35, le blanchiment augmentant le degré de blancheur GE de ladite pâte pratiquement libre de lignine à au moins 70 p.c. environ.
  37. Procédé selon la revendication 34 ou 35, le traitement de blanchiment augmentant le degré de blancheur GE de la pâte pratiquement libre de lignine à au moins 80 p.c. environ.
  38. Procédé selon la revendication 34 ou 35, le traitement de blanchiment augmentant le degré de blancheur GE de ladite pâte pratiquement libre de lignine à au moins 90 p.c. environ.
  39. Procédé selon la revendication 1, la pâte obtenue par une extraction oxygène-lignine ayant un n° K d'environ 10 ou moins et une viscosité plus élevée qu'environ 13 cps après l'extraction oxygène-lignine, et la pâte obtenue par l'extraction ozone-lignine ayant un n° K d'environ 5 ou moins et une viscosité plus élevée qu'environ 10 et un degré de blancheur GE d'au moins 50 p.c. environ après l'extraction ozone-lignine.
  40. Procédé selon la revendication 39, la matière de lignine-cellulose étant un "softwood" et étant soumise à une extraction partielle de lignine, jusqu'à ce que la pâte ait un n° K d'environ 7 à 10 et une viscosité plus élevée que 13 environ, avant l'extraction de lignine avec de l'ozone.
  41. Procédé selon la revendication 40, la pâte de "softwood" ayant un n° K d'environ 3 à 4, une viscosité plus élevée qu'environ 10 et un degré de blancheur GE d'au moins 50 p.c. environ après l'extraction ultérieure de lignine avec de l'ozone.
  42. Procédé selon la revendication 39, la matière de lignine-cellulose étant un "hardwood" et étant libérée partiellement de lignine jusqu'à une pâte avec un n° K d'environ 5 à 8 et une viscosité plus élevée que 13 environ, avant l'extraction ultérieure de lignine avec de l'ozone.
  43. Procédé selon la revendication 42, la pâte de "hardwood" ayant un n° K d'environ 3 à 4, une viscosité plus élevée qu'environ 10 et un degré de blancheur GE d'au moins 55 p.c. environ après l'extraction ultérieure de lignine avec de l'ozone.
  44. Procédé selon la revendication 39, comprenant ensuite:
       la combinaison d'une pâte pratiquement libérée de lignine avec une quantité effective d'une matière alcaline dans une solution alcaline aqueuse pendant un certain temps et à une certaine température dépendant de la quantité totale de matière alcaline, pour dissoudre une partie considérable de la lignine restée dans la pâte, et d'extraire ensuite une partie de la solution alcaline aqueuse pour éliminer ainsi de la pâte pratiquement toute la lignine déjà dissoute et pour réaliser une pâte pratiquement libre de lignine.
  45. Procédé selon la revendication 44, ladite étape d'extraction augmentant le degré de blancheur de la pâte d'environ 2 p.c.
  46. Procédé selon la revendication 44, comprenant ensuite le blanchiment de la pâte pratiquement libre de lignine avec du dioxyde de chlore ou un peroxyde pour augmenter le degré de blancheur GE à au moins 70 p.c.
  47. Procédé selon la revendication 46, le degré de blancheur GE étant augmenté à au moins 80 p.c. environ.
  48. Procédé selon la revendication 46, le degré de blancheur GE étant augmenté à au moins 90 p.c. environ.
  49. Procédé selon la revendication 44, la matière de lignine-cellulose étant libérée partiellement de lignine par un traitement d'extraction oxygène-lignine.
  50. Procédé selon la revendication 49, le traitement d'extraction oxygène-lignine étant effectué sur une pâte de moyenne consistance.
  51. Procédé selon la revendication 44, la matière de lignine-cellulose étant libérée partiellement de lignine par:
       la formation d'une pâte ayant une consistance relativement petite de moins de 10 p.c. en poids;
       le traitement de la pâte ayant une petite consistance avec une quantité de matière alcaline dans une solution alcaline aqueuse pendant un certain temps et à une certaine température dépendant de la quantité de matière alcaline jusqu'à obtenir une répartition pratiquement complète et en grande partie égale de la matière alcaline dans la pâte;
       l'augmentation de la consistance de la pâte jusqu'à au moins 20 p.c. en poids après l'achèvement de l'étape du traitement; et
       la soumission de la pâte ayant une consistance augmentée et comprenant de la matière alcaline à un traitement d'extraction oxygène-lignine pour une consistance augmentée afin d'obtenir une pâte partiellement libre de lignine avec un n° K d'environ 9 ou moins et une viscosité d'environ 13 ou plus.
  52. Procédé selon la revendication 1, l'étape d'extraction oxygène-lignine comprenant:
       la réduction de la consistance de la pâte à une consistance de moins de 10 p.c. en poids;
       le traitement de la pâte ayant une consistance réduite avec une quantité de matière alcaline dans une solution alcaline aqueuse pendant un certain temps et à une certaine température dépendant de la quantité de matière alcaline afin de réaliser ainsi une répartition pratiquement uniforme de la matière alcaline dans la pâte;
       l'augmentation de la consistance de la pâte jusqu'à au moins environ 20 p.c. en poids après l'achèvement de l'étape de traitement; et
       la soumission de la pâte ayant une consistance augmentée et comprenant de la matière alcaline à un traitement d'extraction oxygène-lignine pour une consistance augmentée afin de réaliser ainsi une pâte partiellement libérée de lignine et avec un n° K d'environ 9 ou moins et une viscosité de plus de 13 cps environ;
       la fourniture par l'étape d'extraction oxygène-lignine d'une pâte considérablement libérée de lignine ayant un n° K d'environ 5 ou moins, une viscosité de plus d'environ 10 et un degré de blancheur GE d'au moins 50 p.c. environ;
       le procédé comprenant ensuite:
       la combinaison de la pâte libérée de lignine par de l'ozone avec une quantité effective d'une matière alcaline dans une solution alcaline aqueuse pendant un certain temps et à une certaine température dépendant de la quantité totale de matière alcaline, pour dissoudre une partie considérable de la lignine éventuellement restée dans la pâte;
       l'extraction d'une partie de la solution aqueuse pour éliminer ainsi de la pâte pratiquement toute la lignine déjà dissoute et pour réaliser une pâte pratiquement libre de lignine; et
       le blanchiment de la pâte pratiquement libre de lignine pour augmenter le degré de blancheur GE à au moins 70 p.c. environ.
  53. Procédé selon la revendication 52, le degré de blancheur GE étant augmenté à au moins 80 p.c.
  54. Procédé selon la revendication 52, le degré de blancheur GE étant augmenté à au moins 90 p.c. environ.
  55. Procédé selon la revendication 52, la matière de lignine-cellulose étant un "softwood" et étant libérée partiellement de lignine jusqu'à un n° K d'environ 8 à 9 et à une viscosité plus élevée qu'environ 14, avant l'extraction ultérieure de lignine avec de l'ozone.
  56. Procédé selon la revendication 55, le "softwood" ayant un n° K entre environ 3 et 4, une viscosité d'environ 10 et un degré de blancheur GE d'au moins 54 p.c. environ après l'extraction ultérieure avec de l'ozone.
  57. Procédé selon la revendication 52, la matière de lignine-cellulose étant un "hardwood" et étant libérée partiellement de lignine jusqu'à un n° K d'environ 6 à 7 et à une viscosité plus élevée qu'environ 15, avant que l'extraction ultérieure de lignine avec de l'ozone ait lieu.
  58. Procédé selon la revendication 57, la pâte de "hardwood" ayant un n° K entre environ 3 et 4, une viscosité plus élevée qu'environ 10 et un degré de blancheur GE d'au moins 63 p.c. environ, après ladite étape d'extraction de lignine avec de l'ozone.
  59. Procédé selon la revendication 52, la matière de lignine-cellulose partiellement libérée de lignine étant obtenue par une trituration Kraft, une trituration Kraft AQ ou une étape d'extraction de lignine prolongée d'une matière de lignine-cellulose.
  60. Procédé selon la revendication 52, comprenant la diminution du n° K de la pâte ayant une consistance d'environ 60 p.c. pendant l'étape d'extraction oxygène-lignine sans détériorer considérablement les composants de cellulose de la pâte.
  61. Procédé selon la revendication 52, la pâte étant soumise à une étape d'extraction oxygène-lignine lorsqu'elle a une grande consistance sans changer dans une large mesure la viscosité de la pâte.
  62. Procédé selon la revendication 52, comprenant la diminution du n° K d'environ 25 p.c.par rapport à la viscosité de la pâte pendant l'étape d'extraction oxygène-lignine.
  63. Procédé selon la revendication 52, la consistance de la pâte, laquelle a été traitée avec la solution alcaline aqueuse avant l'étape d'extraction oxygène-lignine, est comprise entre environ 1 et 4,5 p.c. en poids.
  64. Procédé selon la revendication 52, la consistance de la pâte étant augmentée à environ 25 à 35 p.c. en poids, l'exécution de l'étape d'extraction oxygène-lignine.
  65. Procédé selon la revendication 52, la quantité de matière alcaline répartie dans la pâte ayant une petite consistance avant l'extraction oxygène-lignine est comprise entre environ 15 et 30 p.c. en poids par rapport au poids sec de la pâte.
  66. Procédé selon la revendication 65, la solution alcaline aqueuse ayant une concentration de matière alcaline comprise entre environ 20 et 120 g/l, de sorte que la concentration de la matière alcaline dans la pâte ayant une petite consistance est comprise entre 6,5 et 13 g/l.
  67. Procédé selon la revendication 52, l'étape de traitement alcaline étant effectuée pendant un temps compris entre 1 et 15 min. environ et à une température comprise entre 90 et 150°F environ.
  68. Procédé selon la revendication 52, la pâte formée à l'origine étant une pâte "brownstock", et lors de l'étape pour l'augmentation de la consistance de la pâte, au moins une partie du liquide obtenu de la solution alcaline étant ensuite reconduite à l'étape de traitement alcaline.
  69. Procédé selon la revendication 1:
    la pâte étant formée à l'origine comme une pâte "brownstock" avec un n° K compris entre environ 10 et 24 par une trituration Kraft, une trituration Kraft AQ ou une extraction de lignine prolongée de la matière de lignine-cellulose;
       l'étape d'extraction oxygène-lignine comprenant:
       la diminution de la consistance de ladite pâte à environ 1 à 4,5 p.c. en poids;
       le traitement de la pâte ayant une consistance réduite avec une quantité de matière alcaline dans une solution alcaline aqueuse ayant une concentration de la matière alcaline comprise entre environ 20 et 120 g/l pendant un temps compris entre environ 1 et 15 minutes et une température comprise entre environ 90 et 150°F, de telle sorte que la concentration de la matière alcaline dans la pâte ayant une consistance réduite est comprise entre environ 6,5 et 13 g/l pendant cette étape de traitement, pour achever ainsi une répartition pratiquement uniforme de la matière alcaline dans la pâte;
       l'augmentation de la consistance de la pâte traitée avec un alcalin à environ 25 à 35 p.c. en poids;
       la soumission de la pâte ayant une consistance augmentée à une extraction oxygène-lignine pour une grande consistance sans changer dans une large mesure la viscosité de la pâte et afin de réaliser ainsi une pâte partiellement libre de lignine et avec un n° K d'environ 10 ou moins et une viscosité plus élevée qu'environ 13, le rapport entre le n°de K et la viscosité de ladite pâte étant diminué d'au moins 25 p.c. pendant l'extraction oxygène-lignine;
       l'étape d'extraction oxygène-lignine fournissant une pâte en grande partie libre de lignine et avec un n° K d'environ 5 ou moins, une viscosité plus élevée qu'environ 10 et un degré de blancheur GE d'au moins 50 p.c. environ;
       le procédé comprenant ensuite:
       la combinaison de la pâte en grande partie libre de lignine avec une quantité effective d'une matière alcaline dans une solution alcaline aqueuse pendant un certain temps et à une certaine température dépendant de la quantité de matière alcaline, pour dissoudre une partie considérable de la lignine restée dans la pâte;
       l'extraction d'une partie de la solution aqueuse pour éliminer ainsi de la pâte pratiquement toute la lignine déjà dissoute et pour réaliser une pâte pratiquement libre de lignine; et
       le blanchiment de la pâte pratiquement libre de lignine pour augmenter le degré de blancheur GE à au moins 70 p.c. environ.
  70. Procédé selon la revendication 69, le degré de blancheur GE étant augmenté à au moins 80 p.c. environ.
  71. Procédé selon la revendication 69, le degré de blancheur GE étant augmenté à au moins 90 p.c. environ
  72. Procédé selon la revendication 69, comprenant la diminution du n° K de la pâte ayant une consistance augmentée d'environ 60 p.c. pendant l'étape d'extraction oxygène-lignine sans détériorer dans une large mesure les composants de cellulose de la pâte.
  73. Procédé selon la revendication 69, la pâte pratiquement libre de lignine étant blanchie avec du dioxyde de chlore ou un peroxyde.
  74. Procédé selon la revendication 73, le peroxyde étant un peroxyde d'hydrogène.
  75. Procédé selon la revendication 69, comprenant ensuite l'addition à la pâte d'un agent chélateur avant l'étape d'extraction oxygène-lignine, afin de rendre les ions métalliques pratiquement non réactifs par rapport à l'ozone.
  76. Procédé selon la revendication 75, l'agent chélateur étant du ADTP, de l'AEDT ou de l'acide oxalique.
  77. Procédé selon la revendication 69, comprenant ensuite le réglage du pH de la pâte jusque dans une plage de 1 à 4 en ajoutant à la pâte une quantité suffisante de matière acide, avant l'étape d'extraction ozone-lignine.
  78. Procédé selon la revendication 69, comprenant ensuite l'augmentation de la consistance à une valeur comprise entre environ 25 et 50 p.c. en poids, avant l'étape d'extraction ozone-lignine.
  79. Procédé selon la revendication 78, la consistance de la pâte étant augmentée à une valeur comprise entre environ 35 et 45 p.c. en poids, avant l'étape d'extraction ozone-lignine.
  80. Procédé selon la revendication 69, comprenant le broyage de la pâte à un diamètre plus petite qu'environ 5 mm après l'étape d'extraction oxygène-lignine et avant l'étape d'extraction ozone-lignine.
  81. Procédé selon la revendication 69, comprenant ensuite la maintenance de la pâte à une température de moins d'environ 120°F pendant l'étape d'extraction ozone-lignine.
  82. Procédé selon la revendication 69, l'ozone étant fourni par un mélange comprenant de l'ozone et de l'oxygène.
  83. Procédé selon la revendication 82, la concentration d'ozone dans le mélange étant comprise entre environ 1 et 8 p.c. en volume.
  84. Procédé selon la revendication 69, l'ozone étant fourni par un mélange d'ozone et d'air.
  85. Procédé selon la revendication 84, la concentration d'ozone étant comprise entre environ 1 et 4 p.c. en volume.
  86. Procédé selon la revendication 69, comprenant le transport de la pâte partiellement libre de lignine pendant l'étape d'extraction ozone-lignine, de telle sorte que pratiquement toute la pâte est exposée à l'ozone.
  87. Procédé selon la revendication 86, l'ozone étant ajouté à contre-courant de la pâte avançante.
  88. Procédé selon la revendication 86, l'ozone étant ajouté dans le même sens que la pâte avançante.
  89. Procédé selon la revendication 1:
       la pâte libérée de lignine par l'ozone ayant un n° K d'environ 10 ou moins et une viscosité plus élevée qu'environ 13 cps;
       l'étape d'extraction ozone-lignine comprenant:
       l'addition à la pâte d'un agent chélateur pour rendre les ions métalliques de la pâte pratiquement non réactifs par rapport à l'ozone;
       le réglage du pH de ladite pâte jusque dans une plage d'environ 1 à 4, en ajoutant une quantité suffisante de matière acide;
       l'augmentation de la consistance de ladite pâte jusqu'à une valeur comprise entre environ 25 et 50 p.c.;
       le broyage de la pâte ayant une consistance augmentée à un diamètre de moins d'environ 5 mm; et
       l'extraction de lignine de ladite pâte ayant une consistance augmentée avec une quantité effective d'ozone pendant un temps suffisamment long en transportant la pâte broyée d'une telle manière que pratiquement toute la pâte est exposée à l'ozone, afin d'obtenir une pâte qui comprend considérablement moins de lignine et qui a un n° K d'environ 5 ou moins, une viscosité plus élevée qu'environ 10 et un degré de blancheur d'au moins 50 p.c. environ;
       lequel procédé comprend ensuite:
       la combinaison de la pâte en grande partie libre de lignine avec une quantité effective d'une matière alcaline dans une solution alcaline aqueuse pendant un certain temps et à une certaine température dépendant de la quantité de matière alcaline, pour dissoudre une partie considérable de la lignine éventuellement restée dans la pâte;
       l'extraction d'une partie de la solution alcaline aqueuse pour éliminer ainsi de la pâte pratiquement toute la lignine déjà dissoute et pour réaliser une pâte pratiquement libre de lignine; et
       le blanchiment de la pâte pratiquement libre de lignine avec du dioxyde de chlore pour augmenter son degré de blancheur GE à au moins 70 p.c. environ.
  90. Procédé selon la revendication 89, le degré de blancheur GE étant augmenté à au moins 80 p.c. environ.
  91. Procédé selon la revendication 89, le degré de blancheur GE étant augmenté à au moins 90 p.c. environ.
  92. Procédé selon la revendication 89, l'étape de trituration comprenant une trituration Kraft et l'étape d'extraction oxygène-lignine diminuant le n° K de la pâte d'environ 60 p.c. au moins sans détériorer considérablement les composants de cellulose de la pâte et sans réellement changer la viscosité de la pâte.
  93. Procédé selon la revendication 92, l'étape de trituration comprenant une trituration Kraft AQ.
  94. Procédé selon la revendication 93, l'étape d'extraction oxygène-lignine diminuant le n° K de la pâte d'environ 60 p.c. au moins sans détériorer dans une large mesure les composants de cellulose de la pâte et sans changer dans une large mesure la viscosité de la pâte.
  95. Procédé selon la revendication 89, l'étape de trituration comprenant la combinaison d'une trituration Kraft et une extraction de lignine prolongée, et l'étape d'extraction oxygène-lignine diminuant le n° K de la pâte d'environ 60 p.c. au moins sans détériorer dans une large mesure les composants de cellulose de la pâte et sans changer considérablement la viscosité de la pâte.
  96. Procédé selon la revendication 89, la pâte étant transportée pendant l'extraction ozone-lignine d'une telle manière que la pâte est maintenue à une température de moins d'environ 120°F.
  97. Procédé selon la revendication 89, l'agent chélateur et un acide sont ajoutés à la pâte dans une chambre de mélange.
  98. Procédé selon la revendication 97, au moins une partie du liquide enlevé de la pâte lors de l'étape pour l'augmentation de la consistance étant reconduite à la chambre de mélange.
  99. Procédé selon la revendication 97, la pâte étant transportée dans le même sens que l'ozone.
  100. Procédé selon la revendication 97, la pâte étant transportée à contre-courant de l'ozone.
  101. Procédé selon la revendication 1:
       la pâte libérée de lignine par de l'oxygène ayant un n° K d'environ 10 ou moins, et une viscosité plus élevée qu'environ 13 cps;
       l'étape d'extraction ozone-lignine comprenant:
       l'addition à la pâte d'un agent chélateur pour rendre les ions métalliques de la pâte pratiquement non réactifs par rapport à l'ozone;
       le réglage du pH de ladite pâte jusque dans une plage d'environ 1 à 4, en ajoutant une quantité suffisante de matière acide;
       l'augmentation de la consistance de la pâte jusqu'à une valeur comprise entre environ 25 et 50 p.c.;
       le broyage de la pâte ayant une consistance augmentée à un diamètre de moins d'environ 5 mm; et
       l'extraction de lignine de la pâte ayant une consistance augmentée au moyen d'une quantité effective d'ozone pendant un temps suffisamment long, afin de réaliser une pâte en grande partie libérée de lignine et avec un n° K d'environ 5 ou moins, une viscosité plus élevée qu'environ 10 et un degré de blancheur GE d'au moins 50 p.c. environ;
       lequel procédé comprend ensuite:
       la combinaison de la pâte dans une large mesure libérée de lignine avec une quantité effective d'une matière alcaline dans une solution alcaline aqueuse pendant un certain temps et à une certaine température dépendant de la quantité de matière alcaline, pour dissoudre une partie considérable de la lignine restée dans la pâte;
       l'extraction d'une partie de la solution alcaline aqueuse pour éliminer ainsi de la pâte pratiquement toute la lignine déjà dissoute et pour réaliser une pâte pratiquement libre de lignine;
       le blanchiment de la pâte pratiquement libre de lignine avec un peroxyde pour augmenter son degré de blancheur GE à au moins 70 p.c. environ.
  102. Procédé selon la revendication 101, le degré de blancheur GE étant augmenté à au moins 80 p.c. environ.
  103. Procédé selon la revendication 101, le degré de blancheur GE étant augmenté à au moins 90 p.c. environ.
  104. Procédé selon la revendication 101, l'étape de trituration comprenant une trituration Kraft et l'étape d'extraction oxygène-lignine diminuant le n° K de la pâte d'au moins 60 p.c. sans détériorer considérablement les composants de cellulose de la pâte et sans considérablement changer sa viscosité.
  105. Procédé selon la revendication 101, l'étape de trituration comprenant une trituration Kraft AQ.
  106. Procédé selon la revendication 105, l'étape d'extraction oxygène-lignine diminuant le n° K de la pâte d'au moins 60 p.c. sans détériorer considérablement les composants de cellulose de la pâte et sans changer considérablement la viscosité de la pâte.
  107. Procédé selon la revendication 101, l'étape de trituration comprenant la combinaison d'une trituration Kraft AQ et une extraction de lignine prolongée, et l'étape d'extraction oxygène-lignine diminuant le n° K de la pâte d'au moins 60 p.c. sans détériorer dans une large mesure les composants de cellulose de la pâte et sans changer dans une large mesure la viscosité de la pâte.
  108. Procédé selon la revendication 89 ou 101, l'étape d'extraction ozone-lignine diminuant le n° K de la pâte d'au moins 50 p.c.
  109. Procédé selon la revendication 89 ou 101, l'étape de blanchiment augmentant le degré de blancheur GE de la pâte d'au moins 50 p.c.
  110. Procédé selon la revendication 109, le degré de blancheur GE de la pâte étant augmenté d'au moins 83 p.c.
  111. Procédé selon la revendication 1:
       la pâte étant lavée entre l'étape de décomposition chimique et l'étape d'extraction oxygène-lignine, la pâte ayant un n° K d'environ 10 ou moins et un viscosité plus élevée qu'environ 13 cps après l'étape d'extraction oxygène-lignine;
       le procédé comprenant ensuite:
       le lavage de la pâte libérée de lignine par de l'oxygène;
       la continuation de l'étape d'extraction ozone-lignine pour obtenir une pâte considérablement libérée de lignine et avec un n° K d'environ 5 ou moins, une viscosité plus élevée qu'environ 10 et un degré de blancheur GE d'environ 50 p.c. au moins;
       le lavage de la pâte dans une large mesure libérée de lignine;
       la combinaison de la pâte dans une large mesure libérée de lignine avec une quantité effective d'une matière alcaline dans une solution alcaline aqueuse pendant un certain temps et à une certaine température dépendant de la quantité de matière alcaline, pour dissoudre une partie considérable de la lignine éventuellement restée dans la pâte;
       l'extraction d'une partie de la solution alcaline aqueuse pour éliminer ainsi de la pâte pratiquement toute la lignine déjà dissoute et pour former une pâte réellement libre de lignine;
       le lavage de la pâte réellement libre de lignine;
       le blanchiment de la pâte réellement libre de lignine avec du dioxyde de chlore ou un peroxyde pour augmenter son degré de blancheur GE à au moins 70 p.c. environ; et
       le lavage de la pâte blanchie.
  112. Procédé selon la revendication 111, le degré de blancheur GE étant augmenté à au moins 80 p.c. environ.
  113. Procédé selon la revendication 111, le degré de blancheur GE étant augmenté à au moins 90 p.c. environ.
  114. Procédé selon la revendication 111, le traitement de lavage pour le blanchiment de la pâte comprenant: le lavage de la pâte avec de l'eau fraîche et l'enlèvement de la pâte de la lavure qui s'écoule.
  115. Procédé selon la revendication 111, du dioxyde de chlore étant utilisé lors de l'étape de blanchiment et la lavure d'écoulement provenant de la pâte étant évacuée.
  116. Procédé selon la revendication 111, du dioxyde de chlore étant utilisé lors du traitement de blanchiment et la lavure s'écoulant de la pâte blanchie étant traitée par une osmose inversée pour former un filtrat traité, au moins une partie du filtrat formé étant conduit au traitement de lavage de la pâte pratiquement libre de lignine.
  117. Procédé selon la revendication 111, un peroxyde étant utilisé lors du traitement de blanchiment et au moins une partie de la pâte blanchie étant reconduite à l'étape de lavage de la pâte pratiquement libre de lignine.
  118. Procédé selon la revendication 116 ou 117, le traitement de lavage de la pâte pratiquement libre de lignine comprenant: le lavage de la pâte avec de la lavure provenant de la pâte pratiquement libre de lignine et l'enlèvement de la pâte de la lavure résultante et le retour d'au moins une partie de ladite lavure au traitement de lavage de la pâte pratiquement libre de lignine.
  119. Procédé selon la revendication 118, le traitement de lavage de la pâte pratiquement libre de lignine comprenant: le lavage de ladite pâte avec la lavure provenant de la pâte en grande partie libérée de lignine, l'enlèvement de la pâte de la lavure résultante, et l'addition d'au moins une partie de cette lavure au traitement de lavage de la pâte partiellement libérée de lignine.
  120. Procédé selon la revendication 119, le traitement de lavage de la pâte partiellement libérée de lignine comprenant: le lavage de ladite pâte avec de la lavure provenant de la pâte en grande partie libérée de lignine, l'enlèvement de la pâte de la lavure résultante, et l'addition d'au moins une partie de ladite lavure au traitement de lavage de la pâte.
  121. Procédé selon la revendication 120, le traitement de lavage de la pâte comprenant: le lavage de ladite pâte avec de la lavure provenant de la pâte partiellement libérée de lignine, l'enlèvement de la pâte de la lavure résultante, et l'accumulation et la concentration de ladite lavure pour combustion dans un chauffe-eau de récupération.
  122. Procédé selon la revendication 111 ou 121, du dioxyde de chlore avec une teneur minimale en chlore étant utilisé pour la traitement de blanchiment.
  123. Procédé selon la revendication 111 ou 121, la quantité d'eau nécessaire pour les traitements de lavage étant réduite considérablement par rapport aux procédés connus de CEDED ou OC/DED.
  124. Procédé selon la revendication 115, le liquide d'écoulement ayant une couleur qui n'est pas plus forte qu'environ 2 livres par tonne, un BOD5 qui n'est pas plus grand qu'environ 2 livres par tonne et une quantité totale de chlorures organiques qui n'est pas plus grande que 2 environ.
  125. Procédé selon la revendication 75, l'agent chélateur étant un polycarboxylate ou un dérivé de polycarboxylate.
  126. Procédé selon la revendication 75, l'agent chélateur étant utilisé en une quantité de 0,1 à 0,2 p.c. en poids par rapport au poids sec à l'étuve de la pâte.
  127. Procédé selon la revendication 75, la pâte étant acidifiée jusqu'à un pH compris entre environ 1 et 4 avant le traitement avec l'agent chélateur.
  128. Procédé selon la revendication 75, le degré de blancheur de la pâte étant augmenté avec un peroxyde après le traitement de blanchiment avec de l'ozone.
EP90908787A 1990-05-17 1990-05-17 Procede moins polluant de blanchiment de matieres lignocellulosiques Expired - Lifetime EP0483163B1 (fr)

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Families Citing this family (29)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5472572A (en) * 1990-10-26 1995-12-05 Union Camp Patent Holding, Inc. Reactor for bleaching high consistency pulp with ozone
US5441603A (en) * 1990-05-17 1995-08-15 Union Camp Patent Holding, Inc. Method for chelation of pulp prior to ozone delignification
US5328564A (en) * 1990-09-17 1994-07-12 Kamyr, Inc. Modified digestion of paper pulp followed by ozone bleaching
WO1992012289A1 (fr) * 1991-01-03 1992-07-23 Union Camp Patent Holding, Inc. Procede de decoloration de pulpe lignocellulosique sans utilisation de chlore
SE468355B (sv) * 1991-04-30 1992-12-21 Eka Nobel Ab Blekning av kemisk massa genom behandling med komplexbildare och ozon
EP0515303B2 (fr) † 1991-05-24 2001-07-04 Union Camp Patent Holding, Inc. Procédé de blanchiment avec ozone
US5364503A (en) * 1992-02-20 1994-11-15 Macmillan Bloedel Limited Nitric oxide treatment for ozone bleaching
CA2089516A1 (fr) * 1992-02-21 1993-08-22 Kaj Henricson Procede de mise en pate et de blanchiment sans chlore
SE469387B (sv) * 1992-05-11 1993-06-28 Kamyr Ab Saett vid blekning av massa utan anvaendning av klorkemikalier
CA2144433A1 (fr) * 1992-10-01 1994-04-14 Thomas P. Gandek Blanchiment ameliore pour pate lignocellulosique possedant une forte consistance
US5403441A (en) * 1992-11-13 1995-04-04 Union Camp Patent Holding, Inc. Method for controlling an ozone bleaching process
SE501613C2 (sv) * 1993-08-03 1995-03-27 Kvaerner Pulping Tech Sätt vid integrering av blekning och återvinning vid framställning av massa
BR9407409A (pt) * 1993-09-02 1996-11-12 Union Camp Patent Holding Processo para tratar polpa lignocelulósica antes da etapa de alvejamento e deslignificar a mesma na etapa de deslignificação por oxigênio
BR9407457A (pt) * 1993-09-03 1996-11-12 Union Camp Patent Holding Processo para a preparação de uma polpa alvejada possuindo um certo brilho e uma certa resistência como indicado por uma certa viscosidade
US5810973A (en) * 1993-09-21 1998-09-22 Beloit Technologies, Inc. Apparatus for producing small particles from high consistency wood pulp
SE502172C2 (sv) * 1993-12-15 1995-09-04 Mo Och Domsjoe Ab Förfarande för framställning av blekt cellulosamassa med en klorfri bleksekvens i närvaro av karbonat
ATE176285T1 (de) * 1994-06-27 1999-02-15 Champion Int Corp Verbessertes verfahren zum wiedergewinnen von filtraten von blechgeräte
US5672247A (en) * 1995-03-03 1997-09-30 Union Camp Patent Holding, Inc. Control scheme for rapid pulp delignification and bleaching
US5736004A (en) * 1995-03-03 1998-04-07 Union Camp Patent Holding, Inc. Control scheme for rapid pulp delignification and bleaching
US5944952A (en) * 1995-07-26 1999-08-31 Beloit Technologies, Inc. Method for bleaching high consistency pulp with a gaseous bleaching reagent
CN1050642C (zh) * 1996-06-25 2000-03-22 华南理工大学 高浓纸浆过氧化氢漂白方法
US6077396A (en) * 1997-05-16 2000-06-20 Lariviere; Christopher J. Apparatus for fluffing and contacting high consistancy wood pulp with a gaseous bleaching reagent
ID23571A (id) * 1997-08-25 2000-05-04 Praxair Technology Inc Metoda penerapan ozon dalam pemutihan ecf
FR2910027B1 (fr) * 2006-12-13 2009-11-06 Itt Mfg Enterprises Inc Procede de blanchiment des pates papeteries chimiques par traitement final a l'ozone a haute temperature
FI119062B (fi) * 2006-12-28 2008-07-15 Upm Kymmene Corp Menetelmä mekaanisen massan valmistamiseksi
JP4973284B2 (ja) * 2007-03-30 2012-07-11 栗田工業株式会社 パルプ洗浄剤、パルプ製造方法、及びパルプ洗浄方法
US8497097B2 (en) * 2010-08-11 2013-07-30 Georgia Tech Research Corporation Chlorine dioxide treatment of biomass feedstock
CN104313933A (zh) * 2014-09-23 2015-01-28 华南理工大学 一种硫酸盐蔗渣浆绿色漂白方法
CN115584653B (zh) * 2022-12-12 2023-03-10 河南禾力能源有限公司 一种利用糠醛渣提取α-纤维素的方法

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1090510A (fr) * 1976-06-02 1980-12-02 Arthur W. Kempf Delignification et blanchiment par l'ozone d'une pate lignocellulosique liquide
JPS5390402A (en) * 1977-01-12 1978-08-09 Kogyo Gijutsuin Pulp bleaching method
FI67413C (fi) * 1977-04-27 1985-03-11 Myrens Verksted As Foerfarande foer behandling av finfoerdelad fiberhaltig eller cellulosahaltig massa samt anordning foer utfoerande av foerfarandet
US4216054A (en) * 1977-09-26 1980-08-05 Weyerhaeuser Company Low-consistency ozone delignification
NO142091C (no) * 1977-10-17 1980-06-25 Myrens Verksted As Fremgangsmaate ved ozonbehandling av raffinoermekanisk og termomekanisk masse.
JPS5679797A (en) * 1979-11-30 1981-06-30 Weyerhaeuser Co Bleaching of cellulose fiber
US4619733A (en) * 1983-11-30 1986-10-28 Kooi Boon Lam Pollution free pulping process using recycled wash effluent from multiple bleach stages to remove black liquor and recovering sodium hydroxide from the black liquor
US4806203A (en) * 1985-02-14 1989-02-21 Elton Edward F Method for alkaline delignification of lignocellulosic fibrous material at a consistency which is raised during reaction
CA2015296C (fr) * 1989-05-31 2001-08-07 Karnail Atwal Derives de pyranyl cyanoguanidine
CA2053035C (fr) * 1990-10-12 1997-09-30 Repap Enterprises Inc. Pates de bois sans chlore, et procede de fabrication

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NO920217D0 (no) 1992-01-16
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CN1043798C (zh) 1999-06-23
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EP0483163A1 (fr) 1992-05-06
PT98487A (pt) 1993-01-29
BR9007533A (pt) 1992-04-28
DE69019350T2 (de) 1996-02-15
JPH05500243A (ja) 1993-01-21
ATE122421T1 (de) 1995-05-15
SE9200107L (en) 1992-03-13
CA2063591C (fr) 1998-02-03
JP2825346B2 (ja) 1998-11-18
RU2102547C1 (ru) 1998-01-20
PT98487B (pt) 1998-06-30
AU638017B2 (en) 1993-06-17
EP0483163A4 (en) 1992-08-05
WO1991018145A1 (fr) 1991-11-28
KR920703922A (ko) 1992-12-18
NO920217L (no) 1992-03-05
CA2063591A1 (fr) 1991-11-18
SE9200107D0 (sv) 1992-01-15
AU5676890A (en) 1991-12-10
DE69019350D1 (de) 1995-06-14
ES2073027T3 (es) 1995-08-01

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