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
  • D21C5/00—Other processes for obtaining cellulose, e.g. cooking cotton linters ; Processes characterised by the choice of cellulose-containing starting materials
  • D21C5/005—Treatment of cellulose-containing material with microorganisms or enzymes
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
  • D21B1/00—Fibrous raw materials or their mechanical treatment
  • D21B1/02—Pretreatment of the raw materials by chemical or physical means
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
  • D21B1/00—Fibrous raw materials or their mechanical treatment
  • D21B1/02—Pretreatment of the raw materials by chemical or physical means
  • D21B1/021—Pretreatment of the raw materials by chemical or physical means by chemical means
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C1/00—Pretreatment of the finely-divided materials before digesting
  • D21C1/10—Physical methods for facilitating impregnation
• • 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
  • D21C1/00—Pretreatment of the finely-divided materials before digesting
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/08—Mechanical or thermomechanical pulp

Definitions

• RMP refiner mechanical pulping
• TMP thermo-mechanical pulping
• CMP chemical treatment with thermo-mechanical pulping
• CMP chemi-mechanical pulping
• kraft or sulfate process for pulping wood.
• cellulose polymers are the predominate molecule.
• Cellulose is desired for retention in the pulp for paper production.
• the second most abundant polymer in the native wood is lignin.
• Lignin the least desirable component in the pulp, is a complex macromolecule of aromatic units with several different types of interunit linkages.
• lignin physically protects cellulose polysaccharides in complexes known as lignocellulosics that must be disrupted for there to be accessibility to the polysaccharides,(e.g., by enzymes) or to separate lignin from the matrix of the wood fibers.
• Mechanical pulping accounts for about 25% of the wood pulp production in the world today. This volume is expected to increase in the future as raw materials become more difficult to obtain. Mechanical pulping, with its high yield, is viewed as a way to extend these resources. However, mechanical pulping is electrical energy-intensive and yields paper with lower strength than chemical pulps. Kraft pulp is often added to mechanical pulp to impart strength, but it is much more expensive than mechanical pulp. These disadvantages limit the use of mechanical pulp in many grades of paper.
• HPD Horse Power Days
• thermo-mechanical processes e.g., TMP and CTMP
• high temperatures are used to separate the fibers during refining. These processes generally require the refining to be carried out in one or more steps.
• the first step is usually a pressurized step with refining being performed at temperatures above 100°C and immediately below or at the softening temperature of lignin. During this step, the pulp is typically mechanically processed using the RMP method.
• the pressure and temperature is usually modulated to achieve the desired state of freeness between the fibers.
• a steam pressure of 301b or less is applied to the chips for 2-5 minutes prior to refining.
• This pressure is critical to separate the cell wall fibers in such a way that the resulting paper has much longer fibers (increased tear index) than the straight RMP process. If one exceeds the pressure above 30 lbs during presteaming, then the lignin will be melted and deposited on the surface of fibers and the fiber flexibility will be lost resulting in poor quality fibers that resemble the fibers produced during medium density fiber board production. Therefore, it is critical to maintain the right gauge pressure during refining.
• the drawback of the TMP process is that it takes significantly higher amounts of energy compared to the RMP process.
• the energy requirement during the TMP process is in the range of 140-220 HPD (about 2500-4000 kWh)/ton of wood.
• the steam pressure also results in the darkening of pulp.
• more bleach chemicals are needed to obtain paper of a desired brightness.
• Fibrillation is necessary to increase the flexibility of the fibers and to bring about the fine material characteristics of quality processed pulp. It has been suggested that a decrease in energy consumption from an established level in various TMP and CTMP processes has been associated with the deterioration of certain pulp properties, including a reduction in the long fiber content of the pulp, a lower tear strength and tensile strength, and a higher shive content. As a result, high energy consumption in TMP and CTMP processes has been generally necessary in current pulping practices.
• Biopulping techniques have been developed to supplement traditional pulping methods and have been shown to reduce energy requirements and improve paper properties.
• Biopulping is defined as the treatment of wood chips with a "natural" wood decay fungus prior to mechanical pulping.
• wood chips are steamed, cooled, inoculated with a fungus, and incubated for two weeks under forced aeration to remove metabolic heat generated by the fungus.
• the process saves a substantial amount of electrical energy (about 30%), improves paper quality, reduces the environmental impact of pulping, and enhances economic competitiveness.
• the economics of the process is highly dependent on the treatment time and processing costs such as those associated with ventilation of the pile for two weeks to remove metabolic heat generated by the fungus.
• lignin-degrading fungi such as Ceriporiopsis subvermispora, Hyphodontia setulos, Phlebia subserialis, Phlebia brevispora, Phlebia tremellosa and Phanerochaete chrysosporium.
• lignin-degrading fungi such as Ceriporiopsis subvermispora, Hyphodontia setulos, Phlebia subserialis, Phlebia brevispora, Phlebia tremellosa and Phanerochaete chrysosporium.
• biopulping techniques secrete enzymes inside the wood cell walls which are responsible for breakdown or modification of lignin.
• fiber loading Another promising technology used in the pulp and paper industry for improving paper brightness, opacity, and bonding strength, as well as reducing energy consumption during drying, is a technique termed "fiber loading.”
• fiber loading calcium carbonate is deposited as a filler within, on the surface of, and outside the fibers.
• the process consists of at least two steps. First, calcium hydroxide is mixed into a pulp fiber slurry. Next, the pulp and calcium hydroxide mixture is reacted using a high consistency pressurized reactor (refiner or disk disperser) under carbon dioxide pressure to precipitate calcium carbonate. Calcium carbonate formed is termed fiber-loaded precipitated calcium carbonate (FLPCC).
• FLPCC fiber-loaded precipitated calcium carbonate
• most applications of fiber loading have focused on fiber loading chemical pulps.
• Pitch is a mixture of hydrophobic resinous materials and constitutes about 2-8% of the total wood weight depending upon the species and the time of the year. It causes a number of problems in wood processing, including at least deposits on tile and metal surfaces, plugging of drains, discoloration of felt, tears and other defects in paper and downtime for cleaning.
• Traditional methods of controlling pitch include natural seasoning of wood before pulping and/or adsorption and dispersion of the pitch particles with chemicals.
• pitch reduction methods can also include adding fine talc, dispersants and other kinds of chemicals.
• Biotechnological methods of reducing blue staining include the use of CARTAPIPTM (Agra Sol Inc., Raleigh, North Carolina, U.S.A.), which, as discussed, is also used in reducing, pitch. It has been shown that treatment with CARTAPIPTM also controls unwanted colored blue stain microorganisms that lead to increased costs in the purchase of bleach chemicals. However, as with pitch reduction methods, efforts to reduce blue staining have not been completely successful.
• Described is a method of pulping wood including the step of treating, pretreating or exposing a source of pulp to microwave radiation to reduce substantially the power requirements, chemical requirements, or process time to convert the source of pulp to pulp.
• a method of producing pulp for use in making paper products includes steps of treating wood logs with or exposing logs to microwave radiation, chipping the logs and pulping the wood chips with a mechanical pulping process. Suitable mechanical pulping processes include RMP, TMP and CTMP.
• the method can include fiber loading the pulp.
• Chips obtained from micro waved logs could also be treated with microorganisms and enzymes to save energy, improve paper strength, reduce pitch content, and increase chemical penetration to benefit the pulp and paper and lumber processing industries.
• the method can be used with hard- or softwood species as pulp sources.
• Suitable hardwood species include aspen, eucalyptus and oak.
• Suitable softwood species include spruce and pine.
• the invention also encompasses a paper produced according to the methods described.
• the paper demonstrates improved strength characteristics over methods not including a microwave step.
• the paper demonstrates at least a 10% increase in measurements of tensile index, tear and burst.
• Another facet of the invention is a method of producing wood pulp that includes steps of treating the wood source, e.g., logs, with microwave radiation, chipping the logs to provide wood chips, inoculating the wood chips with a fungus and mechanically processing the inoculated wood chips to provide pulp.
• Suitable fungal species include the "white rot" species commonly used in biopulping. Included among the suitable species are Ceriporiopsis subvermispora, Hyphodontia setulos, Phlebia subserialis, Phlebia brevispora, Phlebia tremellosa or Phanerochaete chrysosporium.
• An additional species which can be used in a method of the invention is a white or colorless species of Ophistoma piliferum, which can be used to reduce pitch and/or blue staining.
• the invention is also directed to a method of producing pulp that includes the steps of microwaving wood, chipping the wood, applying enzymes to the wood chips and mechanically processing the enzyme-treated wood chips to provide pulp. Suitable enzymes include lignin-degrading enzymes, xylanases, pectinases, lipases and cellulases.
• the invention provides for energy savings during wood pulping and includes a method of reducing energy input requirements.
• the method includes steps of treating wood with microwave radiation, chipping the wood and mechanically pulping the wood chips, wherein the energy input requirement is reduced at least about 8% over a method not including the step of treating logs with microwave radiation. Suitably, the energy requirement is reduced at least about 8% to about 15%.
• a method of reducing pitch is described wherein a pulp source is treated with microwave radiation prior to subsequent process steps.
• FIG. 1 is a photograph of a waveguide and chamber for a 60-kW industrial microwave oven that can be used in the methods of the invention.
• FIG. 2 is a graph showing radial temperature as a function of microwave power level for 20- and 50-kW treated logs.
• FIG. 3 is a photograph showing steam jet issuing from end of a log after microwave treatment at 50 kW for 5 minutes.
• FIG. 4 is a photograph showing extensive radial checking after microwave treatment at 50 kW for 5 minutes.
• FIG. 5 is a scanning electron micrograph of a tangential fracture surface after microwave treatment at 50 kW for 5 minutes.
• FIG. 6 is a scanning electron micrograph of a tangential fracture surface after microwave treatment at 50 kW for 5 minutes.
• FIG. 7 is a graph showing freeness as function of refiner energy consumption for several microwave pretreatments.
• FIG. 8 is a graph showing refiner energy savings as a function of microwave power level for several microwave pretreatments.
• FIG. 9 is a graph showing tensile index as a function of microwave power level for micro wave-pretreated black spruce TMP.
• FIG. 10 is a graph showing estimated annual pulp cost savings for 800 ton/day for a mill based on substitution of micro wave-pretreated TMP for kraft pulp.
• mechanical processing and “mechanically processing” refer to processing methods in which mechanical, electrical or thermal energy is used to break down intact wood into constituent fibers to produce wood pulp with a desired level of freeeness. Suitable methods include TMP, RMP and CTMP. TMP is a preferred method.
• biopulping refers to a method used in the production of pulp that includes the use of a biological system to perform, or to assist in performing, the pulping of wood.
• biopulping is carried out by inoculating steamed wood chips with a species of fungi known to degrade or modify lignin.
• Preferred fungal species include the so-called "white rot" fungi.
• white rot species are species of Ceriporiopsis subvermispora, Hyphodontia setulos, Phlebia subserialis, Phlebia brevispora, Phlebia tremellosa or Phanerochaete chrysosporium.
• the terms "reduced energy input requirements," “improved strength properties,” and “enhanced permeability” are relative terms that indicate a reduction, improvement or enhancement, respectively, over a pulping method that does not include a microwave treatment (including modifications of a method to accommodate a microwave step), but otherwise including the same steps as the described methods.
• the method of the invention reduces the energy input requirement at least about 8%>. Most suitably, the method of the invention reduces the energy input requirement at least about 8% to about 15%. Paper produced according to the method of the invention suitably demonstrates at least about a 10% increase in strength properties.
• the permeability of wood to chemicals also is enhanced by exposure of the wood to microwave radiation according to one aspect of a method of this invention.
• microwave pre-treatment can be realized in many aspects of paper manufacturing.
• Microwave pretreatment of wood can reduce electrical power requirements, improve paper quality, reduce pitch and reject contents, improve paper machine operation and save energy during drying of pulp, etc.
• the technology also has potential for improving existing biopulping processes, by preventing blue staining of wood, enhancing the penetration of enzymes and other large molecules into wood, improving fiber loading processes, and improving chemical penetration during lumber processing.
• Microdry, Inc. (Crestwood, KY) is a manufacturer of custom industrial microwave ovens suitable for use in the present invention Individual logs can be manually placed in the microwave chamber until appropriate treatment time and frequency is determined. Treatment parameters are dependent upon a number of factors, including type of wood, diameter of the log and moisture content. After optimization of treatment parameters, however, a continuous belt transport system capable of accommodating logs can be used. Microwaving can be done prior to or after debarking.
• Chipping of logs is within those of skill in the art and be can be accomplished with any known suitable techniques.
• One suitable technique is to use a Sprout- Waldron Model D2202 single rotating 300 mm diameter disk refiner. After chipping, a mechanical pulping process is carried out. Mechanical pulping processes include RMP, TMP and CTMP. In thermomechanical pulping, high power refiners are used to mechanically reduce wood chips to fiber. To aid in this process, elevated temperatures are used to soften the wood. Several refining "passes" are generally required to obtain a target freeness. The first pass is usually defibration at temperatures above 100°C and immediately below or at the glass transition temperature of lignin (T g ⁇ 124°C).
• chips are typically fiberized under pressure using an aggressive plate pattern to produce a high freeness pulp.
• This pulp is then further reduced in multiple passes through an atmospheric refiner until the desired pulp freeness is obtained.
• microwave treatments alter the structure of wood such that fiberization occurs more easily during mechanical pulping, thereby reducing refiner energy requirements and improving the pulp.
• the method can include fiber loading the pulp.
• Fiber loading is described in U.S. Patent Number 5,223,090, issued June 29, 1993, and is incorporated herein by reference.
• Further methods of the invention include producing pulp by treating logs with microwave radiation, chipping the logs to provide wood chips, inoculating the wood chips with a fungus and mechanically processing the inoculated wood chips.
• Microwave treatment, chipping and mechanical processing is carried out as described above.
• suitable species for inoculation of the wood chips are Ceriporiopsis subvermispora, Hyphodontia setulos, Phlebia subserialis, Phlebia brevispora, Phlebia tremellosa or Phanerochaete chrysosporium.
• microwaved logs When microwaved logs are debarked, chipped and inoculated with biopulping fungus, the treatment time is substantially reduced as compared to conventional biopulping without the use of microwave pretreatment.
• the enhanced porosity of the microwaved chips provides faster colonization of these chips by the fungus.
• microwaved logs or chips from these logs can be inoculated with CARTAPIPTM or other fungal species to remove blue stain microorganisms or pitch. As described above, the enhanced porosity facilitates colonization, thereby reducing treatment and incubation times.
• a method of the invention for reducing pitch and/or blue staining can be carried out using a colorless species of Ophistoma piliferum, which can be used to reduce pitch and/or blue staining.
• One species of Ophistoma piliferum is sold under the trade mark CARTAPIPTM by Agra Sol Inc. of Raleigh, North Carolina, U.S.A..
• this fungus is suitably applied to wood chips subsequent to microwaving as described.
• U.S. Patent No. 5,607,855, issued March 4, 1997 describes a suitable method of reducing pitch with fungi and is incorporated herein by reference.
• microwaving of logs can be used to reduce or remove resinous material. Not to be bound by theory, it is believed that some of the components of this resinous material that are sticky, such as triglycerides, are converted into a less sticky material after microwaving.
• the invention is also directed to a method of producing pulp that includes the steps of microwaving wood, chipping the wood ' and applying enzymes to the wood chips.
• Suitable enzymes include lignin-degrading enzymes, xylanases, pectinases, Upases and cellulases.
• the invention provides for energy savings during wood pulping and includes a method of reducing energy input requirements.
• the method includes steps of treating wood with microwave radiation, chipping the wood and mechanically pulping the wood chips, wherein the energy input requirement is reduced at least about 8% over a method not including the step of treating logs with microwave radiation.
• the energy requirement is reduced at least about 8% to about 15%.
• the inventors have discovered that higher energy savings correlate with higher power levels used during the microwave pretreatment step. Energy savings are also observed during debarking and chipping compared to logs that were not microwaved.
• Microdry, Inc. (Crestwood, KY) is a manufacturer of custom industrial microwave ovens suitable for use in the present invention.
• a high capacity microwave oven was used for initial tests (FIG. 1).
• This oven is connected to a variable-power (up to 60 kW) 915- MHz frequency generator.
• Individual logs can be manually placed in the microwave chamber until appropriate treatment time and frequency is determined. Treatment parameters are dependent upon a number of factors, including type of wood, diameter of the log and moisture content. After optimization of treatment parameters, however, a continuous belt transport system capable of accommodating logs can be used.
• Microwaved logs or chips obtained from these logs demonstrate increased porosity as has been observed in treated logs.
• FIG. 2 it has been determined that higher power levels result in higher log temperatures, with steeper temperature gradients from bark to pith.
• results obtained using spruce logs microwaved for 5 min at 50 kW Within a couple of minutes, splitting became intense and steam jets shot out the ends of the logs (FIG. 3) In just 5 minutes, the logs had lost about 25% of their weight or nearly all of their moisture.
• a visual examination of the ends of the logs revealed extensive radial checking (FIG. 4).
• Several fracture surfaces from logs treated at 5 min 50 kW were sampled to identify possible morphological changes in the fiber structure.
• a scanning electron microscope was used to obtain images of both tangential and radial surfaces (FIGS. 5 and 6).
• an additional advantage of the invention is a reduction in amounts of bleaching chemicals required during bleaching. This, in turn, increases the opacity of the resulting paper and reduces the effluent treatment costs associated with paper production.
• Microwave Treatments Logs were subject to three microwaving conditions. Logs were microwaved at 50 kW for 5 minutes (50/5), 20 kW for 6 minutes (20/6), and 20 kW for 8 minutes (20/8).
• Chip fiberization, pulp refining and handsheet production Microwaved wood chips were fiberized in a Sprout- Waldron Model D2202 single rotating 300 mm diameter disk refiner. Energy consumption was measured using an Ohio Semitronic Model WH 30- 11195 integrating Wattmeter attached to the power supply side of the 44.8 kW electric motor. Feed rate through the refiner was between 10 kW and 15 kW. Energy reported in WH/kg. Refiner plate settings were 0.025 inch, 0.014 inch, 0.010 inch, and 0.008 inch. Pulp was collected at each pass as hot water slurry. Between the passes the pulp slurry was dewatered to approximately 25% solids in a porous bag by vacuum.
• Dilution water at 85 degrees Celsius was then added each time as the pulp was fed into the refiner. Samples of the pulp were taken and tested for the Canadian Standard Freeness (CSF). Samples refined to 100 CSF. Handsheets were prepared and tested using TAPPI standard testing methods.
• Microwave Treatments Logs were subject to three microwaving conditions. Logs were microwaved at 50 kW for 5 minutes (50/5), 20 kW for 6 minutes (20/6), and 20 kW for 8 minutes (20/8).
• Chip fiberization, pulp refining and handsheet production Microwaved wood chips were fiberized in a Sprout- Waldron Model D2202 single rotating 300 mm diameter disk refiner. Energy consumption was measured using an Ohio Semitronic Model WH 30- 11195 integrating Wattmeter attached to the power supply side of the 44.8 kW electric motor. Feed rate through the refiner was between 10 kW and 15 kW. Energy reported in WH/kg. Refiner plate settings were 0.025 inch, 0.014 inch, 0.010 inch, and 0.008 inch. Pulp was collected at each pass as hot water slurry. Between the passes the pulp slurry was dewatered to approximately 25% solids in a porous bag by vacuum.
• Logs are microwaved as described in Example 1. Logs are then chipped and sprayed with compositions containing a mixture of Upases, xylanases, pectinases, cellulases and lignin-degrading enzymes. Upon mechanical processing to provide pulp, a decrease in energy input requirements and an increase in paper strength and desirable optical characteristics are noted.

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  • 2002-11-12 CA CA002466505A patent/CA2466505A1/en not_active Abandoned
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