Classifications

• • 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
  • D21C11/00—Regeneration of pulp liquors or effluent waste waters
  • D21C11/0007—Recovery of by-products, i.e. compounds other than those necessary for pulping, for multiple uses or not otherwise provided for
• • 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
  • D21C3/00—Pulping cellulose-containing materials
  • D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
• • 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
  • D21C3/00—Pulping cellulose-containing materials
  • D21C3/22—Other features of pulping processes
  • D21C3/222—Use of compounds accelerating the pulping processes
• • 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
  • D21C9/1084—Bleaching ; Apparatus therefor with reducing compounds

Definitions

• the invention relates to compositions, methods, and apparatuses for improving the efficiency of chemical pulping.
• Chemical pulping with (kraft process) and without (alkaline or soda process) sodium sulfide can be enhanced by certain additives such as 9,10-anthraquinone (AQ) or sodium polysulfide.
• AQ 9,10-anthraquinone
• sodium polysulfide Such additives provide energy and chemical savings during the pulping process and chemical savings in subsequent bleaching stages. This is achieved, in particular, by delivering lower kappa numbers and higher yields that allow pulping at lower temperatures/shorter times and bleaching with lesser chemicals.
• the existing additives have serious shortcomings that warrant further development in this area.
• polysulfide is not quite efficient and applied in large quantities; AQ is currently restricted if not completely eliminated due to environmental and health regulations.
• a novel additive that can substitute in part or in full for AQ in chemical (soda and kraft) pulping.
• At least one embodiment of the invention is directed towards a process for digesting pulp.
• the method comprising the addition of a composition to pulp undergoing a delignification process, the composition comprising a small dosage of borohydride (BH)(sodium borohydride preferred) relative to the oven dried mass of the pulp.
• the composition may be added to white liquor and fed to the digester with the liquor before the temperature ramping begins.
• the BH may be in the form of an alkaline solution in water.
• the amount of BH relative to oven dried pulp may be less than 0.1% on the active base.
• the BH solution that is the product added to the mill liquor may be sufficiently alkaline so it is stabile under normal conditions and does not release hydrogen.
• the dosage of BH may be in an amount insufficient to be effective in bleaching the pulp.
• At least one embodiment of the invention is directed towards a method for digesting wood chips.
• the method comprises the addition of a composition to a lignin bearing substrate in a pulping process and then applying to the substrate a subsequent bleaching step.
• the composition comprises a small dosage of BH relative to the oven dried mass of substrate.
• the BH is dosed at a point in the pulping process where there has been no black liquor in contact with the substrate, and where no more than at least 0.001% - 10% or more or less of
• the dose is in an amount high enough to selectively reduce at least 0.001% - 10% or more or less of the lignin alpha-carbonyl groups in substrate thereby making them more susceptible to subsequent easy quinone methide beta-O-4 bond splitting during pulping process, but not as high as it would substantially deactivate at least 0.001% - 10% or more or less of the chromphores in the lignin by itself.
• the bleaching step involves adding a dosage of bleach no greater than an amount insufficient to cause the resulting paper stock to have been substantially whitened in the absence of AQ but for the presence of the low dose BH, and wherein the resulting paper stock is whitened.
• At least one embodiment of the invention may improve soda or kraft pulping.
• the method may comprise the step of adding a composition to pulp liquor comprising sodium borohydride in alkali prior to pulping; the method provides fresh white liquor savings, decreased kappa number, increased brightness, lower rejects and higher yield of pulp.
• the composition may comprise 10- 40% alkali and 5-25% borohydride.
• the method may further comprise adding a surfactant to the pulp.
• the method may further comprise adding a polysulfide to the pulp.
• the small dosage may be characterized as causing the BH to selectively attack functional groups in lignin in substructures critically important for accelerated further delignification in the pulping process and passivizing hemicelluloses towards chemical degradation in the same process.
• the method may exclude using BH in a dosage sufficient to bleach the pulp.
• FIG. 1. is a raw data graph of white liquor / total liquor ratio; a 3-day trial through 9-day period.
• FIG. 2. is a graph of % alkali savings in a trial with 1.5 lb/t product (0.07% as product, 0.008% as actives) through one day.
• a ⁇ 2 means 9,10-anthraquinone.
• BH means borohydride, it includes but is not limited to BH ions appended to any anion such as but not limited to alkali metals and alkali earth metals, it may be in the form of a solid and/orsolution.
• Bulk Delignification Stage means the phase of kraft cooking in which the major portion of the delignification occurs as a first order reaction and with a selectivity that is high compared to the initial delignification, it is further described in the textbook Handbook of Pulp&Paper Terminology, by G.A. Smook, Angus Wilde, Vancouver, BC, (1990), generally and in particular pp. 75-85.
• Delignification '1' ' means one or more processes of removing lignin from wood at any point in a papermaking process.
• “Bleaching” means one or more processes of removing color from pulp or paper by the removal and/or chemical alteration of chromophore groups from pulp or paper, bleaching may include but is not limited to the removal or alteration of at least some of the lignin originally present in the pulp or paper, bleaching may involve but is not limited to the addition of strong oxidizing and/or reducing agents such as chlorine dioxide.
• Whitening 9' means the process of removing most color in paper or pulp, representative methods of measuring whiteness include but are not limited to ASTM E313 and the description in Measurement and Control of the Optical properties of Paper, by Technidyne Corporation, New Albany, Indiana, (1996), generally and in particular pp. 16-18.
• Standard Dose or “Low Dose” means in an amount of less than 0.25% actives relative to the oven dried mass of a pulp material, it includes but is not limited to a dosage of as low as (or lower than) 0.05-0.5% product (which may be 0.005-0.06% actives in a typical 10- 12% alkaline solution) relative to oven dried pulp.
• Passivate means to render a first material substantially, more, and/or essentially passive or non-reactive in relation to a second material prior to contact between the two materials, where but for the passivation the first and second materials would be reactive when in contact.
• Consisting Essentially of means that the methods and compositions may include additional steps, components, ingredients or the like, but only if the additional steps, components and/or ingredients do not materially alter the basic and novel characteristics of the claimed methods and compositions.
• Paper Stock means a substrate that has completed the pulping process and is or will be ready to be fed into a paper machine, it is described in more detail in Handbook for Pulp and Paper Technologists, 3rd Edition, by Gary A. Smook, Angus Wilde Publications Inc., (2002) in general and in particular pp. 190-204.
• Paper Product means the end product of a papermaking process. It includes but is not limited to writing and/or graphic paper, printer paper, paper tissue, cardboard, paperboard, and packaging paper.
• Papermaking process means any portion of a method of making paper products from wood pulp comprising forming an aqueous cellulosic papermaking furnish, draining the furnish to form a sheet and drying the sheet.
• the steps of forming the papermaking furnish, draining and drying may be carried out in any conventional manner generally known to those skilled in the art.
• the papermaking process may also include a pulping stage, i.e. making pulp from a lignocellulosic raw material and bleaching stage, i.e. chemical treatment of the pulp for brightness improvement, papermaking is further described in the reference Handbook for Pulp and Paper Technologists, 3rd Edition, by Gary A. Smook, Angus Wilde Publications Inc., (2002) and The Nalco Water Handbook (3rd Edition), by Daniel Flynn, McGraw Hill (2009) in general and in particular pp. 32.1-32.44.
• Substrate means a mass containing paper/cellulose fibers going through or having gone through any point in a papermaking process, substrates includes wood, wood chips, pulp, paper stock, wet web, paper mat, slurry, paper sheet, and paper products.
• surfactant is a broad term which includes anionic, nonionic, cationic, and zwitterionic surfactants. Enabling descriptions of surfactants are stated in Kirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, volume 8, pages 900-912, and in
• Water Soluble means materials that are soluble in water to at least 3%, by weight, at 25 degrees C.
• a composition comprising a small quantity of reductive product is added to a substrate of a pulping process to save fresh white liquor, decrease kappa number and increase brightness and yield of pulp.
• the composition may be added before the alkaline pulping process, including kraft pulping process. The addition may result in substantial chemicals savings.
• the composition may comprise a borohydride composition.
• the borohydride composition may contain borohydride in a stabilized form (i.e. that is in a form that allows less than 10% activity loss after no less than 3 months under normal conditions).
• the borohydride composition may contain sodium borohydride.
• a representative example of the borohydride composition is the commercially available product Borol sold by Dow.
• the composition may be fed into a substrate via white liquor at the very early stage of the pulping process.
• the effect is achieved through early lignin activation and hemicellulose stabilization at the stage of temperature ramping.
• Borohydride (BH) is a strong reductive agent that reacts with carbonyl groups in lignin and hemicelluloses before the bulk stage of pulping providing additional avenues for lignin depolymerization at the latter stages of pulping. It appears that contrary to how it performs at high dosages, at low dosages BH selectively attacks functional groups in pulp, thus activating e lignin and passivizing
• BH has been known to be effective in the pulp and paper industry, its actual use has been limited to mechanical pulp bleaching, where it role normally was just to reduce the negative effect of oxidation of another component of the bleaching composition, air- sensitive sodium hydrosulfite.
• BH has also been added as a bleaching agent to pulp and as an activator in oxygen delignification (an oxidative process). All these applications, however, require relatively large doses of BH to achieve any measurable bleaching effect. Because BH's thermodynamic stoichiometry is different at low dosages (in pulping, activation of selected groups towards following reactions) than it is at these higher dosages (direct change in the color of the materials trough lignin removal and reduction of maximum, possible chromophore groups as a sole agent, regardless of any following processes) it preferentially reacts with different materials at low dosages than it is known to react in these prior art references.
• the invention may be accomplished using a solution instead of a solid.
• Prior art applications used solids because they are more stable and less hazardous.
• BH is stabilized in alkaline solution and then can be safely used in the industry.
• BH is highly reactive, it may react with dissolved reducible components of the liquor instead of the pulp at high temperatures.
• Low temperature, low dosages and minimum dissolved wood components in the initial solution focus the BH on the pulp material instead.
• the invention utilizes a methodology opposite that of US Patent 3,617,431.
• the method excludes using the material in black liquor and at high temperatures at the feeding stage (over 60° F).
• a soda or kraft pulping process is improved by feeding a composition comprising BH in alkali (including but not limited to Borol, Venpure or any other commercial or ad hoc liquid containing 10-25% (or higher or lower) NaBH4 in 20- 40% (or higher or lower) NaOH as a potential range for the compositions) into white liquor prior to pulping that eventually provides decreased kappa number, increased brightness, lower rejects and higher yield of pulp, also saving process chemicals (white liquor) as compared to the conventional technology. Feeding the composition in a liquid form provides convenience in delivery, safety, and, most important, fast homogenization in white liquor thus ensuring even and efficient delivery to wood chips and fast if not immediate reaction that is required for the efficiency of the process.
• alkali including but not limited to Borol, Venpure or any other commercial or ad hoc liquid containing 10-25% (or higher or lower) NaBH4 in 20- 40% (or higher or lower) NaOH as a potential range for the compositions
• white liquor also saving process chemicals
• the composition is applied in a way that minimizes interaction of the chemical with water-soluble organic components of the liquor targeting directly solid wood chips (e.g. before the temperature increase, in white but not black liquor). This includes but is not limited to feeding the composition into white liquor immediately delivered to the digester. Minimum exposure of the reagent to black liquor is recommended.
• the composition is a strongly alkaline solution containing sodium borohydride, which is a stable, safe and convenient form of BH for transportation, storage and dosing to the target process.
• the composition may contain from approximately 10 to approximately 40% alkali (including but not limited to sodium hydroxide or potassium hydroxide preferred) and from approximately 5 to approximately 25% borohydride (including but not limited to sodium borohydride).
• the composition is applied in a dosage of as low as, equal to, or lower than 0.05-0.5% product (0.005-0.06% BH actives in a 10-12% alkaline solution) relative to oven dried pulp.
• the method includes also adding one or more surfactants to the pulp.
• the surfactant(s) may be mixed into (be within) the composition and/or may be fed separately to the pulp. The latter method is preferred due to the salting effect of relatively concentrated alkali in the liquid BH formulation.
• the surfactant may be ionic, non- ionic, polyvalent, amphoteric, cationic, anionic, and any combination thereof. It was found in a separate stability test (keeping a solution of the two components at elevated temperature and measuring residual active BH by the means of acidification and comparing the volume of evolved hydrogen with the one in a control sample) that both components are compatible.
• the BH is combined with a polysulfide (including but not limited to sodium polysulfide).
• the polysulfide may be mixed into the composition and/or fed separately. It was found in a separate stability test (keeping a solution of the two components at elevated temperature and measuring residual active BH by the means of acidification and comparing the volume of evolved hydrogen with the one in a control sample) that both components are compatible.
• the invention operates by applying a strong reductive chemical or combination of chemicals in white liquor at an early stage of the pulping process. This affects the alkaline pulping process, including a kraft pulping process through lignin activation and carbohydrate stabilization; as a result, less white liquor chemicals are required.
• hemicelluloses providing additional avenues for lignin depolymerization at further stages of the pulping process and reducing carbohydrate degradation thus increasing yield and reducing amount of alkali required to neutralize degradation products.
• the invention leads in a number of unexpected results. It provides safety and efficiency that was never achieved before because the mechanism for the operation of BH in pulp was not properly understood in the prior art. It was a common misconception in regards to the mechanism and application of BH that resulted in all the studies limited by high doses of borohydride (>0.5% actives to oven dried pulp). For example, in US Patent 3,042,575 in its Example 3, it shows that for solid BH, there is no difference between the use of 0% BH and 0.2% and only when up to and in excess of 0.4% is any effect measured. However, by using a BH solution as proposed in the Invention even much smaller dosages are effective.
• the small dosages of BH impart a pronounced positive effect on the actual pulping process at doses that, unexpectedly, differ from those suggested in the prior art based on the laboratory experiments, by the order of magnitude. This makes the difference that allows commercial application of the technology.
• the proposed technology assures safety and convenience of the operation.
• low dose of BH results in low boron presence in the system that eliminates potential regulatory and recovery issues (boron content as element in 17.3% pulp after the oxygen delignification (Eo) stage in a trial with the additive pulp after a mill trial at 1.7 lb/t o.d. as described below was found at 457 ppb ).
• At least one embodiment of the invention imparts a benefit that becomes apparent after cooking. Typically, most of the lignin is removed during cooking and the residual lignin is removed/altered by one or more bleaching steps.
• the low dose BH so selectively modifies the lignin that a dosage of bleaching agent that would otherwise be too low to effectively whiten the pulp does indeed whiten the pulp when the pulp has been treated by low dose BH.
• the low dose BH selectively reduces a few alpha- carbonyl groups in native lignin that makes them susceptible to subsequent easy quinone methide beta-O-4 bond splitting. But for this selective reduction such structures would remain intact and deter lignin depolymerization. But for this selective reaction with low dose BH, the carbonyl groups would have become more chemically stabile would have contributed significantly to the presence of residual lignin in pulp.
• Hardwood chips (sorted, from a mill in Wisconsin), conditioned in a constant temperature and humidity (CTH) room for >4 days, consistency 92%.
• Liquor/wood 8: 1 ratio, with 16% alkali and 33% sulfidity charge.
• Cooking protocol Rotating 250 ml stainless steel digesters, 85°C for 20 min., then ramping to 170°C in 50 min. and keeping the samples at 170°C for additional 20 min (variations in the protocol are indicated in the Tables). After cooking, the digesters were cooled with running water, the pulp disintegrated in a blender and washed. The pulp samples were equilibrated in the CTH room and kappa numbers measured according to TAPPI test method T 236. Handsheets were made, and brightness measured on air-dried sheets using a Technodyne instrument.

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• 2014
  • 2014-10-30 BR BR102014027199-6A patent/BR102014027199B1/pt active IP Right Grant
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• 2015
  • 2015-07-10 RU RU2017103170A patent/RU2698735C2/ru active
  • 2015-07-10 EP EP15822791.8A patent/EP3169843A4/de active Pending
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