Classifications

• • 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
  • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
  • D21B1/00—Fibrous raw materials or their mechanical treatment
  • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
  • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
  • D21B1/14—Disintegrating in mills
  • D21B1/16—Disintegrating in mills in the presence of chemical agents
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C1/00—Pretreatment of the finely-divided materials before digesting
  • D21C1/06—Pretreatment of the finely-divided materials before digesting with alkaline reacting compounds
• • 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
  • D21C1/02—Pretreatment of the finely-divided materials before digesting with water or steam

Definitions

• the present invention relates to a method of producing chemi-mechanical pulp from a wood raw material comprising wood chips, according to the preamble of Claim 1.
• the wood chips comprising the wood raw material are brought into contact with an alkaline impregnation solution in conditions where the solution penetrates into the wood chips to impregnate the wood chips, and the wood chips which are impregnated with the impregnation solution are refined to produce a mechanical pulp.
• the present invention also relates to chemi-mechanical pulp according to Claim 14.
• Chemi-mechanical pulp is produced by refining wood chips which have been prepared with chemicals, typically with an alkaline liquid, to a desired drainability.
• the chemical treatment facilitates the refining and improves the properties of the mechanical pulp.
• the wood chips are prepared with alkaline solutions to facilitate the defibring.
• Alkaline impregnation solutions swell the fibre walls and thus narrow the capillaries. This decreases the longitudinal penetration. However, at the same time, alkaline solutions also dissolve the components of the fibre, which accelerates the penetration.
• the alkali dose and the size of the wood chip have an effect on the diffusion.
• the alkali dose must be increased when the thickness of the wood chip is increased.
• the alkali dosage is raised, the alkali gradient between the wood chip and the surrounding solution increases as well (liquid/wood-ratio the same), and thus the diffusion speed increases.
• the dosage of the alkali which is dosed for the impregnation is the most important factor affecting the yield of the chemi-mechanical pulp (CTMP).
• CTMP chemi-mechanical pulp
• the fibre loss mainly results from the breaking down of the acetic acid, and the dissolving of the lignin and the dissolving of acidic polysaccharides, all of which are caused by the alkali.
• the influence of the alkali dosage is greater for hardwood than for softwood, and for aspen it is especially large.
• the alkali dose for instance the amount of NaOH
• the yield from aspen wood decreases linearly from approximately 95 % to 89 % in a conventional process.
• the effect of the alkali on the scattering qualities of the chemi-mechanical pulp is especially problematic.
• the qualities of the scattering fall with increasing alkali dosage and, when level of refining is the same, the scattering is always smaller when the alkali dosage is larger. Also, bleaching decreases the scattering further.
• To make high-class printing paper it is prerequisite that the scattering and the brightness properties of the pulp are good. It is possible to produce hardwood CTMP pulps to a high brightness, even up to an ISO brightness of 88 %.
• the purpose of the present invention is to eliminate at least some of the disadvantages associated with the known technology, and to provide a novel solution for producing chemi-mechanical pulp.
• the present invention is based on the principle that when producing chemi-mechanical pulp, the impregnation of the chips is carried out at overpressure.
• the method according to the present invention is carried out by arranging in series equipment comprising the following: the chip deaeration unit, the chip impregnation unit and the chip refining unit, in which case the impregnation unit comprises a closed vessel within which the impregnation treatment can be carried out at overpressure.
• the method according to the present invention is mainly characterized by what is stated in the characterization part of Claim 1.
• Pressurized impregnation makes it possible to improve the quality of chemi-mechanical refiner pulp for different end-use applications.
• the method according the present invention comprises three stages, which are
• the raw material thus obtained is impregnated with an alkaline solution at overpressure in order that the alkali is efficiently absorbed into the wood chips, and
• the treated wood chips are refined to a predetermined drainability.
• chemi-mechanical pulp production means in general a process which comprises both a chemical and a mechanical def ⁇ bring stage, as described above.
• the CMP and the CTMP processes are chemi-mechanical processes.
• the wood raw material is refined at normal atmospheric pressure, whereas in the CTMP process a pressure refiner mechanical pulp is produced.
• a higher dosage of chemicals is used in the CMP, its yield is generally smaller than that of the CTMP process (less than 90 %).
• the chemical treatment of the wood is traditionally carried out with sodium sulphite (sulphonation treatment), in which case hardwood can be treated with sodium hydroxide, too.
• a typical chemical dosage in the CTMP process is approximately 0-4 % of sodium sulphite and 1-7 % of sodium hydroxide, and the temperature is approximately 60-120 0 C.
• the chemical dosage is 10-15 % of sodium sulphite and/or 4-8 % of sodium hydroxide (calculated from dry wood), and the temperature is 130-160 °C and, correspondingly, 50-100 0 C.
• the chips can be impregnated with an alkaline peroxide solution, too (APMP process).
• the dosage of peroxide is generally 0.1-10 % (of the dry pulp weight), typically approximately 0.5-5 %.
• the amount of the alkali feed, such as sodium hydroxide, is about the same, i.e. approximately 1-10 weight %.
• the present invention relates especially to the CTMP process, in which the chips coming from the impregnation are defibred using the pressure refiner mechanical pulp method.
• the initial material in the process according to the present invention is chips comprising soft- or hardwood material.
• hardwood chips are used in the production, the chips of which are prepared from birch (generally, a wood species of the Betula genus) or a wood species of the Populus genus or a mixture of them.
• suitable wood species of the Betula genus are B. pendula and B. pubescens, and of the wood species of the Populus genus especially the following: P. tremula, P. tremuloides, P balsamea, P. balsamifera, P. trichocarpa, P. heterophylla, P. deltoides and P. grandidentata.
• Aspen the European aspen, P. tremula; Quaking aspen, P. tremuloides
• aspen species crossbred from different stock aspens hybrid aspens (for instance P. tremula x tremuloides, P. tremula x tremula, P. deltoides x trichocarpa, P. trichocarpa x deltoides, P. deltoides x nigra, P. maximowiczii x trichocarpa) and other species generated by gene technology, along with poplars, are considered to be particularly preferable.
• chemi-mechanical pulp comprising up to 100 % softwood fibres is produced.
• chemi- mechanical pulp which consists of a mixture of hard- and softwood fibres, and which pulp comprises at least 5 % softwood fibres, for instance it may comprise 50-99 % hardwood fibres and 1-50 % softwood fibres. It is possible to increase the bulk, the strength properties and the stiffness of the pulp, by using softwood fibres, especially by using spruce fibres.
• the size of the wood chips of the wood raw material is generally approximately 20-50 mm x 1-10 mm, typically approximately 35-40 mm x 3-5 mm.
• the aim is to remove at least 70 %, especially approximately 80-100 % of the air contained in the chips.
• the air is typically present in gaseous form.
• this deaeration can be carried out by steaming the chips in an evaporator 1.
• the chips of the initial material are fed in by the screw conveyor 2 into the steaming silo 1, into which steam is fed either from one feed nozzle or, as the figure shows, from several nozzles 3a-3c, in order to distribute the steam evenly into the chips in the silo.
• the purpose of the steaming is to remove the air from the wood chips. At the same time, steam remains in the wood chips.
• the steaming can be carried out for instance in a continuous evaporator 1, shown in the figure, in which the wood chips move through the steaming silo 1, where they are brought into contact with the saturated or almost saturated steam for a period of approximately 0.5- 20 minutes, especially approximately 1-10 minutes.
• the steaming can be carried out at overpressure but generally steaming at normal atmospheric pressure is fully adequate.
• an elevated temperature is used, for instance approximately 50-100 °C, especially approximately 80-100 °C, depending on how saturated the steam used is.
• the deaeration can be carried out at low pressure/in a vacuum or the steaming can be made more effective with vacuum treatment.
• the treated chips are removed from the steaming silo through the outlet nozzle 4, after which the chips are most suitably compressed in the plug screw 5. After this stage, typically at least 95 %, preferably at least 98 %, of the air has been removed, and at the same time, part of the steam has also been removed.
• steaming of the chips is used in the production of both sulphate pulp and chemi-mechanical refiner pulp.
• a combination of the steaming of wood chips and pressurized impregnation could be used in the production of chemi-mechanical pulp.
• the wood chips are conducted to the impregnation treatment stage 6.
• the steamed wood chips are brought, essentially still at the temperature of the steaming stage, to the impregnation stage which is carried out in the absorber 6.
• the temperature of the impregnation solution used in the impregnation stage is kept lower than the temperature of the steam in the steaming stage.
• the impregnation stage is carried out in a closed vessel, i.e. a pressure vessel, which is arranged downstream from the steamer.
• the absorber illustrated in the figure basically comprises an elongated absorber, the longitudinal axis of which is essentially arranged vertically, and which has an upper and a lower part, in which case the wood chips coming from the deaeration unit can be fed into the upper part of the absorber and removed via the lower part of the absorber.
• the absorber 6 there is an upper separator 7. Through its input nozzle 7a the chips are fed into the absorber and in the separator, liquid is separated from the wood chips. This liquid is recirculated into the reject flow of the steaming silo 1.
• the steamed wood chips are fed into the impregnation stage together with the impregnation chemicals, in which case the impregnation chemicals are fed in from separate input nozzles 10a- 10c to the pipeline 11 which connects the outlet nozzle 4 of the steamer 1 and the input nozzle 7a of the absorber 6.
• the impregnation chemicals are fed in from separate input nozzles 10a- 10c to the pipeline 11 which connects the outlet nozzle 4 of the steamer 1 and the input nozzle 7a of the absorber 6.
• most suitably pumps 20, 21 or similar devices are arranged in the pipeline.
• an impregnation solution which comprises an aqueous solution of an alkaline material, which solution optionally comprises sulphonation chemicals.
• an aqueous solution of either an alkali metal hydroxide, such as NaOH or KOH, or an alkaline earth metal hydroxide, such as magnesium hydroxide, Mg(OH) 2 , or calcium hydroxide, or mixtures thereof, are used.
• this solution comprises for instance also sulphite compounds, such as sodium sulphite.
• the dosage of alkali hydroxide is typically approximately 2-12 kg/Adt (air dried tonne of pulp), preferably, however, at maximum approximately 6 kg/Adt, more preferably at maximum approximately 4 kg/Adt.
• Alkaline earth metal hydroxides are used in (molarly) corresponding dosages.
• the pH value of the solution is approximately 9-11.
• the consumption of the sulphite compound is approximately 1-20 kg/Adt, for hardwood most suitably at maximum 3 kg/Adt.
• aqueous solutions of compounds of alkaline materials can be used for impregnation, such as cooking liquor obtained from pulp cooking, for instance white or green liquor.
• the temperature of the impregnation stage is approximately 30-95 °C, preferably approximately 40-90 °C, and which can be achieved at least in part by the heat brought in with the chips. Generally, the temperature of the impregnation stage is lower than the temperature of the deaeration stage.
• the pressure of the impregnation stage is approximately 1.5-15 bar, preferably approximately 2-10 bar absolute pressure. As a result, an overpressure of at least approximately 0.5 bar is used in the impregnation.
• the ratio between wood and liquid (p/p) is generally approximately 1 :20...1 :4, especially approximately 1:15...1:6.
• the dosage of the impregnation chemicals can be adjusted, depending on the chips to be treated and, if necessary, it can be increased.
• the duration of the impregnation treatment is approximately 1-240 minutes, preferably approximately 5-120 minutes, especially approximately 10-60 minutes.
• the wood chips are impregnated with alkali to the maximum degree possible.
• at least 85 %, preferably at least 90 %, more preferably at least 95 % of the volume of the pores of the wood chips should be filled with the impregnation solution.
• the impregnation can be carried out in one or in several stages, in which case at least one impregnation stage is carried out at overpressure.
• the hot chips are first impregnated at overpressure under the conditions mentioned above, after which the impregnation process is still continued in an open container or vessel at the same or at a different temperature.
• Approximately 10-80 % of the temporal duration of the impregnation treatment can be carried out under pressurized conditions. In the application described below, the duration times of the pressurized and the unpressurized treatments were equally long, the total duration time being 40 minutes.
• the wood chips coming from the impregnation stage are removed through the outlet nozzle 6a.
• the reference number 6b refers to the discharger of the absorber. With this discharger the residual fraction that has collected at the bottom of the device can be removed. After that, the chips are fed to a refining stage 12 of conventional chemi- mechanical pulp, which can be carried out for instance in refiners equipped with grooved refining blades.
• the wood raw material is refined to a predefined drainability, which is 50- 500 ml CSF, more preferably approximately 90-150 ml CSF.
• the basic drawing 1 shows in practice how the chip flow generated from the impregnation stage can be further processed before the refining. Accordingly, the excess impregnation solution is first removed in the screw press 13, after which the reaction of the chemicals can be continued in the reaction silo 14, before the chips are transported with the screw conveyors 15a and 15b to the refining.
• the reaction time in the reaction silo 14, if such a silo is used, is typically approximately 0.1-10 hours.
• the screw press 13 it is possible to separate impurities and fibre material which are unfit for refining, and they are removed through the screen 16 into the reject channel.
• the liquid phase 17 generated from the screw press can be recirculated into the pipeline 10, possibly in combination with the fresh water feed.
• the reference numerals 22 and 23 refer to the pumps arranged for the feeding of the liquid phase.
• the impregnation solution is most suitably recirculated in the process and its alkali concentration can be adjusted (increased) with fresh alkali feed.
• the two essential factors in the present invention are that a good deaeration is achieved before the impregnation solution and the chips are put together, and that the impregnation is pressurized. These two factors together allow an efficient penetration of the impregnation solution into the wood chips.
• the retention time and the temperature in the pressure vessel are chosen in such as way that it is possible to adjust the diffusion time and the reaction time. There must be enough time for the diffusion to take place, the speed of the reaction must not be too high.
• the chemi-mechanical pulp described above has extraordinarily good properties.
• the light scattering qualities of the pulp are improved, and has been achieved without increasing the shives percentage. Consequently, at the same freeness level, the light scattering qualities of the pulp according to the present invention are at least 5 %, even 10 %, better compared to the high alkali reference.
• the sliver percentages of the pulps according to the present invention are lower than the sliver percentage of the TMP reference and, unexpectedly, even lower than the sliver percentage of the high alkali reference.
• the bulk is improved, too, by as much as 5 %.
• CTMP pulp prepared from aspen may be higher than 45 m 2 /kg and the sliver percentage lower than 0.3 %.
• birch it is possible to generate a pulp exhibiting scattering qualities which are higher than 45 m 2 /kg and a sliver percentage lower than 1.5 %.
• the pulp according to the present invention can be used for the production of paper and cardboard products.
• the pulp is generally bleached, using for instance hydrogen peroxide under alkaline conditions, to a brightness of approximately 75-88 %.
• a slushable initial material is achieved, one which, however, comprises a significant amount (at least 30 weight %) of chemi-mechanical pulp.
• softwood pulp is used as chemical pulp and, in that case, its percentage is 1-50 % of the dry weight of the fibres of the raw material.
• chemi-mechanical aspen pulp it is also possible to use only chemi-mechanical aspen pulp.
• the paper pulp is first slushed to a suitable consistency in a way which is known per se (typically to a solids percentage of approximately 0.1-1 %), after which it is spread onto the wire, where it is webbed to form the paper or cardboard web. It is possible to add a filler such as calcium carbonate, generally approximately 1-50 weight % of the weight of the fibres, into the fibre slush.
• the paper web can be surface sized and/or equipped with a coating layer and, if desired, calendered. Coating pastes can be used for single coating, for precoating and for surface coating. Triple coatings are possible, too.
• a coating according to the present invention contains 10-100 parts by weight of at least one pigment or a mixture of pigments, 0.1-30 parts by weight of at least one binder, and 1-10 parts by weight of other additives known per se.
• CTMP pulp of aspen was prepared in the laboratory under the following conditions:
• Aspen wood chips which had been steamed at 100 0 C for a period of 2-5 minutes, were impregnated with different amounts of sodium hydroxide at a pressure of 5 bar (a), at 80 °C for a period of 20 minutes in a closed container. After that, the impregnation was continued for another 20 minutes in an open reaction silo at 80 0 C.
• Table 1 shows what happens when the aspen chips treated in this way were refined to a drainability level of 150 ml CSF.
• the present invention it is possible to decrease the alkali hydroxide dosage, in which case the scattering clearly increases without increasing the sliver percentage. Compared with the case in which a conventional amount of alkali was used, the scattering increases by more than 10 %. Unexpectedly, the sliver percentage was even lower than in the 1.2 % alkali reference.
• Table 2 shows the bulk of the pulps described above.
• the fibre loss was determined from the impregnation solution before the refining. Refining increases the amount of dissolved material and, correspondingly, it increases the fibre loss, the larger the alkali dose the greater the loss.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Paper (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=35510621

Family Applications (1)

Country Status (12)

Cited By (9)

Families Citing this family (6)

Citations (9)

Family Cites Families (4)

• 2005
  • 2005-12-02 FI FI20051251A patent/FI126694B/fi active IP Right Grant
• 2006
  • 2006-11-30 UY UY29982A patent/UY29982A1/es active IP Right Grant
  • 2006-12-01 BR BRPI0619143-6A patent/BRPI0619143B1/pt active IP Right Grant
  • 2006-12-01 SE SE0801296A patent/SE534004C2/sv unknown
  • 2006-12-01 CA CA2631767A patent/CA2631767C/en active Active
  • 2006-12-01 AR ARP060105313A patent/AR058265A1/es active IP Right Grant
  • 2006-12-01 WO PCT/FI2006/000399 patent/WO2007063171A1/en active Application Filing
  • 2006-12-01 CN CNA2006800451546A patent/CN101341288A/zh active Pending
  • 2006-12-01 CN CN201510047854.XA patent/CN104674583A/zh active Pending
  • 2006-12-01 AU AU2006319052A patent/AU2006319052B2/en not_active Ceased
  • 2006-12-01 RU RU2008125038/12A patent/RU2401350C2/ru active
  • 2006-12-01 JP JP2008542785A patent/JP4823317B2/ja not_active Expired - Fee Related
• 2008
  • 2008-06-02 ZA ZA200804758A patent/ZA200804758B/xx unknown

Patent Citations (9)

Also Published As

Similar Documents

Legal Events