EP2276884A1 - Dispositif et procédé pour le séchage de matières fibreuses - Google Patents

Dispositif et procédé pour le séchage de matières fibreuses

Info

Publication number
EP2276884A1
EP2276884A1 EP09719270A EP09719270A EP2276884A1 EP 2276884 A1 EP2276884 A1 EP 2276884A1 EP 09719270 A EP09719270 A EP 09719270A EP 09719270 A EP09719270 A EP 09719270A EP 2276884 A1 EP2276884 A1 EP 2276884A1
Authority
EP
European Patent Office
Prior art keywords
pulp
root
drying
pulp mixture
mixture
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP09719270A
Other languages
German (de)
English (en)
Inventor
Stephan Kleemann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pacon Ltd & Co KG
Original Assignee
Pacon Ltd & Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Pacon Ltd & Co KG filed Critical Pacon Ltd & Co KG
Publication of EP2276884A1 publication Critical patent/EP2276884A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00—Dryer section of machines for making continuous webs of paper
    • D21F5/14—Drying webs by applying vacuum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B5/00—Drying solid materials or objects by processes not involving the application of heat
    • F26B5/04—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum
    • F26B5/06—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum the process involving freezing

Definitions

  • the present invention relates to a method and an apparatus for drying fibrous materials, in particular for the paper industry. Furthermore, the invention relates to the use of the pulp produced by the process for the production of paper and paper-like products.
  • Dewatering of the material to be dried is typically done by filtration or pressing. Subsequently, the material to be dried is thermally dried over a period of time until reaching the desired degree of drying.
  • the object of the present invention is to find an alternative or a supplement to the drying processes for pulps known in the prior art, in particular for thermal drying processes.
  • the above object is achieved by a process for drying polysaccharide-containing products, in particular selected from cellulose, hemicellulose, starch, amylose and amylopectin, glucans, galactomannans, glucomannans and fructans, as well as carboxyalkyl, hydroxyethyl and hydroxypropyl derivatives, the process being characterized that the drying process is applied at low temperatures by the method of freeze-drying (lyophilization) under vacuum.
  • the pulp mixture according to the invention for the production of paper or paper-like products is characterized in that it can be obtained by a process in which the pulps or pulp mixtures are mechanically dehydrated before freeze-drying.
  • This mechanical dewatering is characterized in that the pulp is preferably dewatered to a dry content of between 35% and 80%.
  • Paper-like products in the context of the invention are cardboards, hygiene articles, filters, printing substrates, coating systems, fibrous boards, tissue, toilet paper, kitchen paper, nonwovens and nonwovens, inter alia for the medical sector, such as e.g. Wound dressings, patches, diapers, incontinence articles, combinations thereof, and the like.
  • the step of freeze drying is characterized in that the pulp or the pulp mixture is cooled in a preferably first step to a temperature below the freezing point of the pulp or pulp mixture and in a preferably second step, the ambient pressure of the pulps or the Fiber mixture for the removal of water from the pulp or the pulp mixture reduced.
  • the evaporation of the contained energy is supplied so that the present under these conditions freezing point of this water is not exceeded.
  • Freezing refers to those points in a phase diagram that lie at the boundary between the aggregate states “solid” and "liquid”.
  • the solids content of the pulps or the pulp mixture before cooling to a predetermined temperature below the freezing point by a thermal drying at a temperature above the evaporation temperature at normal pressure to a value between 45% -root and 99 % -root, preferably to a value of between 55% -root and 90% -root, more preferably to a value of between 60% -root and 85% -root and in particular to a value of more than 80% -ro which is increased.
  • the mechanical dewatering of the pulp or of the pulp mixture takes place in such a way that the dry content of the pulp or of the pulp mixture is between 40% and 75%, preferably between 45% and 75%. otro, more preferably between 50% -root and 70% -root and in particular more than 50% -root.
  • the pulp mixture is characterized in that it comprises at least one
  • Polysaccharide and polysaccharide derivative in particular cellulose, hemicellulose,
  • Starch amylose and amylopectin, glucans, galactomannans, glucomannans and fructans, as well as carboxyalkyl, hydroxyethyl and hydroxypropyl derivatives, wood-containing pulps, woodfree pulps, waste paper, bleached pulps, unbleached pulps, combinations thereof, and the like.
  • the fibers or pulp mixtures are taken up in a liquid phase prior to dehydration or drying, in particular for homogenization and / or uniform mixing, in which case it is preferably an aqueous solution.
  • at least one chemical additive is added to the pulp mixture. This chemical additive is preferably selected from a group comprising fixatives, retention aids, dispersants, wet strength agents, sizing agents, optical brightening agents, dyes, pigments, fillers, absorbents, superabsorbents, all especially for use in the paper industry, combinations thereof, and the like ,
  • the process according to the invention for drying fibrous materials and pulp mixtures is characterized in that pulps or pulp mixtures are dried at low temperatures by the freeze-drying process (lyophilization) under vacuum, the process being characterized in that the pulps or pulp mixtures are mechanical in one step dehydrated to a dry content of between 35% and 80%, and dried in a second step by freeze-drying.
  • the method according to the invention is characterized in that in a preferably first step, the fibers or the pulp mixture is cooled to a temperature below the freezing point of the pulps or the pulp mixture and in a preferably second step, the ambient pressure of the pulps or the Pulp mixture for removing water from the pulp or the pulp mixture is reduced.
  • the solids content of the fibers or pulp mixture is reduced to a temperature below freezing by thermal drying at a temperature above the vaporization temperature at normal pressure to between 45% and 99%.
  • -rotro preferably to a value between 55% -root and 90% -root, more preferably to a value between 60% -rootroot and 85% -rootro and in particular to a value above 80% -totrope.
  • the method is characterized in that the pulp mixture comprises at least one pulp constituent selected from a group consisting of polysaccharide and polysaccharide derivative, in particular cellulose, hemicellulose, starch, amylose and amylopectin, glucans, galactomannans, glucomannans and Fructans, as well as carboxyalkyl, hydroxyethyl and hydroxypropyl derivatives, wood-containing pulps, woodfree pulps, waste paper, bleached pulps, unbleached pulps, combinations thereof, and the like.
  • polysaccharide and polysaccharide derivative in particular cellulose, hemicellulose, starch, amylose and amylopectin, glucans, galactomannans, glucomannans and Fructans, as well as carboxyalkyl, hydroxyethyl and hydroxypropyl derivatives, wood-containing pulps, woodfree pulps, waste paper, bleached pulps, unbleached pulps,
  • the process is characterized in that the fibers or the pulp mixture, in particular for homogenization and / or uniform mixing, are taken up in a liquid phase prior to dewatering, this preferably being an aqueous solution.
  • the method is characterized in that at least one chemical additive is added to the pulp or the pulp mixture.
  • This chemical additive is preferably selected from a group comprising fixatives, retention aids, dispersants, wet strength agents, sizing agents, optical brightening agents, dyes, pigments, fillers, absorbents, superabsorbents, all especially for use in the paper industry, combinations thereof, and the like ,
  • the pulp mixture according to the invention is used for the production of paper, board, hygiene articles, filters, printing substrates, coating systems, fiber-containing plates, tissue, toilet paper, kitchen paper, medical tile, for example wound dressings, patches, diapers, incontinence articles, Combinations thereof and the like used.
  • Freeze-drying is also called cold-drying in the prior art. Water-containing objects, such as moist biomaterials and other porous materials, are frozen, ie cooled below freezing point. The freezing point refers to those points in a phase diagram (FIG. 2) which lie at the boundary between the states of matter "solid" and "liquid”. Subsequently, the frozen objects come into a vacuum chamber.
  • the pulp produced according to the invention is characterized in that it forms a higher strength in the x, y, and z direction, in particular when pressed under pressure, than conventionally produced pulp. This is also likely to be related to the higher reactivity and increased ability to form hydrogen bonds.
  • paper or paper-like products produced from the pulp according to the invention are distinguished, in comparison to products made from untreated, normal pulp, in particular by a comparatively higher volume and also by higher softness, softness and absorbency. The increased absorbency is advantageous, for example, in the treatment of the pulp with subsequent resin solutions, as in the process of decorative paper processing and laminate production.
  • Fig. 1 is a schematic representation of the freeze-drying.
  • 11 denotes the aqueous solution or the hydrous product which is to be freeze-dried.
  • the pre-dried product 12 is formed therefrom, which is now in step 19 is introduced into the drying chamber 13 of the freeze-drying apparatus.
  • the adhering residual water is sublimated via the line 16 into the cooled condenser 14.
  • Fig. 2 shows an example of the 3-phase pressure-temperature diagram for water.
  • 20b denotes the X-axis with the temperature rising from left to right (Kelvin).
  • 20a denotes the y-axis with the pressure rising from bottom to top (bar).
  • the region 23 comprises the solid phase
  • the region 25 the liquid phase
  • 24 comprises the supercritical state region.
  • the triple point, in which solid, liquid and gaseous are present at the same time, is designated by the point 27.
  • the liquid 25 changes into the gaseous state 28 by evaporation.
  • the liquid 25 is converted into the gaseous state 28 by supercritical drying and by-passing the critical point 22.
  • the path 29 indicated by an arrow the liquid passes into the gaseous state 28 by prior conversion into the solid state (freezing) 23 and by the subsequent freeze-drying 29.
  • Freeze-drying is a technical process for removing water.
  • an aqueous crystalline solution is cooled below freezing until it completely freezes to ice.
  • crystals of different sizes may form. Large crystals can lead to a very porous material and thus to short drying times.
  • cryoprotectants there is a risk of overheating.
  • cryoprotectants it is important, above all, that the temperature during the glass transition is not too high, since otherwise the system collapses.
  • the Kollapstemperatur is about 3 0 C above the maximum freeze-saturated concentration.
  • the cryoprotectants stabilize the starting product by increasing the viscosity or prefentional exclution.
  • the latter means that the protein is kept in the native form by the addition of certain substances such as polyols or carbohydrates. Now the air pressure over the ice is reduced (vacuum), whereby the ice is sublimated and thus removed from the frozen solution.
  • the product temperature must be below the elektischer point / glass transition point.
  • freeze-drying heat is applied during this primary drying phase to compensate for the sublimation cold. Lyoprotectors can stabilize during this primary drying phase.
  • Trehalose can be used as a cryoprotectant as well as a lyoprotector and in subsequent secondary drying the temperature in the apparatus is increased to remove any remaining water porous cake with a large surface.
  • Industrial freeze dryers preferably consist of two chambers.
  • the one chamber contains an optionally heatable and coolable footprint on which the product is placed or the aqueous solution is filled in so-called vials (glass vials).
  • the heating or cooling power (of about -50 0 C to +40 0 C) is ensured by a silicone oil circuit via compressors, heat carrier pump and heat exchangers.
  • the second chamber is the so-called condenser, which receives the moisture diffusing from the product.
  • cooling coils which are usually filled with silicone oil. Temperatures from D60 0 C to D80 0 C are reached via a circuit with compressors and evaporators. He is thus the coldest point of the plant.
  • Both chambers can be separated from each other by a flap (intermediate valve). During drying, however, they are connected to each other. A vacuum pump is also connected to the condenser. Using appropriate measuring instruments, the respective degree of the drying process can be precisely determined. Since the refrigeration / heat cycle for the shelves and the refrigerant circuit of the condenser CFC or HFC-containing refrigerant, some systems are now cooled with liquid nitrogen.
  • a pulp mixture consisting of 30% of a pulp 2 ground at 150 kWh / t + 70% Aracruz eucalyptus + 20% PCC (on-top dosage).
  • the used long fiber pulp "pulp 1" from a Swedish company is a fiber optimized for high static (tensile oriented) strength
  • the manufacturer describes the fibers as relatively short, thin-walled and with a low resistance to grinding.
  • the fibrous material used was material which also formed the basis for the previous test series.
  • the preparation of the pulp mixture corresponded exactly to the procedure for the mixtures of 2 pulp components with filler addition.
  • the samples for freeze-drying and for thermal drying were dewatered through a filter over a filter.
  • the filtrate from the filler-containing sample was collected and put over the filter cake again to minimize filler losses.
  • the respective amount of pulp was 200 g / otro, which is about 15 individual filter cake per Test point and drying method corresponds.
  • the filter cake was dried for 24 hours at 105 0 C in a drying oven for thermal drying and then resuspended. Subsequently, the freeze-drying was carried out.
  • the freeze-dried samples were then resuspended. Both samples were evaluated after a further 48 hours to exclude the effects of swelling.
  • As a comparative sample served a sample from the same grinding series was not dried and had the same Nachquellzeit.
  • Resuspending the fibers showed significant differences between the drying processes.
  • the thermally dried material was much stronger or harder and more energy had to be expended for disassembly into single fibers.
  • the freeze-dried samples were very easy to suspend and the filter cake disintegrated even with mere addition of water and gentle stirring in single fibers.
  • the pulp dried by the process according to the invention can be redispersed in water with almost no energy expenditure.
  • the usual service time of the dried pulp is thereby significantly reduced and the energy required for massively reduced.
  • the values for the dewatering time of the dried pulp according to the invention differ significantly.
  • FIG. 9 illustrates the low WRV of dried fibrous materials according to the invention, both for long fiber materials and for fiber mixtures, in comparison to dissolved plate material used as a reference and a sample of this reference, which, however, has been thermally dried.
  • FIG. 3 shows the development of strength with variation of the drying method and use of the long fiber pulp pulp 1 which was ground at 150 kWh / t.
  • the tear index used to describe this value shows an increase for both dried fabrics.
  • the tenacity of the thermally dried sample decreases compared to the non-dried reference sample, whereas it slightly increases in the freeze-dried sample.
  • Fig. 3 shows the strength development of a pulp 1, ground at 150 KWh / t, with variation of the drying process.
  • the tear index in mNm / g and 32 denoted, also rising from bottom to top, the tearing length in km.
  • 33a stands for the normally predried
  • FIG. 6 shows the strength of a pulp mixture (30/70 mixture) below
  • Fig. 6 shows the strength development of one of a mixture of 30% of the pulp 2 milled with 150 kWh / t and 70% eucalyptus 150 kWh / t with variation of the drying process.
  • 61 rising from bottom to top
  • the tear index in mNm / g and 63 denoted, also rising from bottom to top
  • the tearing length in km denotes 61, rising from bottom to top
  • 64a stands for the normally predried pulp (reference sample)
  • 64b for the pulp 64a additionally dried at 105 ° C.
  • 64c for pulp 64a, which was additionally freeze-dried.
  • 65 indicates the respective tear index values of samples 64a, 64b and 64c.
  • 66 denotes the respective break length values of the samples 64a, 64b and 64c.
  • FIGS. 10 and 11 The influence of the drying process on the initial wet strength (IWWS) is shown in FIGS. 10 and 11.
  • FIG. 10 shows that the IWWS of the pulp 1 long fiber pulp ground at 150 kWh / t drops slightly due to the drying according to the invention. Thermal drying of the pulp, however, results in a much greater drop in IWWS.
  • 10 shows a comparison of the initial wet strength (IWWS) of the pulp 1 ground at 150 KWh / t with variation of the drying process.
  • IWWS initial wet strength
  • 101 increasing from bottom to top, designates the initial wet strength in Nm / g.
  • 102 increasing from left to right, indicates the dry content of the samples in percent.
  • 103 stands for the normally pre-dried pulp (reference sample), 105 for the additional pulp 103 dried at 105 ° C., and 104 for pulp 103, which was additionally freeze-dried.
  • FIG 11 illustrates these measurements for the use of the pulp mixture.
  • the IWWS of the 30/70 mixture is slightly above the reference sample after drying according to the invention. This behavior differs from the previous ones Observations. However, the thermal drying leads to a significant drop in the IWWS values compared to the reference sample.
  • FIG. 11 shows a comparison of the initial wet strength (IWWS) of one
  • the volume of the inventive dried pulp in g / cm 3 remains in contrast to thermally dried pulp compared to the non-dried pulp.
  • FIG. 4 shows the influence of the drying process on the volume when using long-fiber pulp, FIG. 7 when using the pulp mixture.
  • the specific volume of the thermally dried sample is much higher when using the long fiber than the undried one. In the drying according to the invention, it is slightly above that of the reference sample.
  • Fig. 4 shows the volume of the pulp 1, ground at 150 KWh / t, with variation of the drying process.
  • the volume in cm flg. 43a stands for the normal predried pulp (comparative sample)
  • 43b for the additionally dried at 105 0 C pulp 43a
  • 43c for pulp 43a, which was additionally freeze-dried.
  • 44 denotes the respective volume values of the samples 43a, 43b and 43c.
  • Fig. 7 shows the volume of one of a mixture of 30% of a pulp 2 milled with 150 kWh / t and 70% eucalyptus 150 kWh / t with variation of
  • 73c for pulp 73a which was additionally freeze-dried.
  • 74 denotes the respective volume values of the samples 73a, 73b and 73c. Comparing the specific volume of the examined pulps of the mixture, exactly the same tendencies are visible as with the pure long fiber pulp. The thermal drying leads to a significant increase, whereas the drying according to the invention results in only a very slight increase in the specific volume.
  • the porosity in ml / min of the dried pulp according to the invention differs significantly from the thermally dried pulp and remains in a similar order of magnitude as the non-thermally dried comparative pulp (FIGS. 4, 7).
  • the porosity of the laboratory sheet formed increases sharply, whereas the drying according to the invention leads to a slightly denser sheet structure compared to the reference sample.
  • the surface roughness also increases significantly in the thermal drying, but only slightly in the drying according to the invention.
  • Fig. 5 shows a comparison of roughness and porosity according to Bendtsen for pulp 1 150 KWh / t with variation of the drying process.
  • 51 increasing from bottom to top, designates the porosity in ml / min.
  • 52a stands for the normally predried pulp (reference sample)
  • 52b for the additional pulp 52a dried at 105 ° C.
  • 52c for pulp 52a, which was additionally freeze-dried.
  • 53 indicates the respective Bendtsen porosity values in ml / min Samples 52a, 52b and 52c.
  • 54 denotes the respective roughness values in ml / min of the tops of the samples 52a, 52b and 52c.
  • Fig. 8 shows a comparison of the roughness and the porosity according to Bendtsen for a mixture of 30% of the pulp 2 ground with 150 kWh / t and 70% eucalyptus 150 kWh / t with variation of the drying process ,.
  • 81 increasing from bottom to top, denotes the porosity in ml / min.
  • 83a represents the normal pre-dried pulp (comparative sample), 83b for additionally dried at 105 0 C pulp 83a, and 83c for pulp 83a was further freeze-dried.
  • 86 indicates the respective Bendtsen porosity values in ml / min of Samples 83a, 83b and 83c.
  • 84 indicates the respective roughness values in ml / min of the tops of the samples 83a, 83b and 83c.
  • 85 indicates the respective roughness values in ml / min of the lower surfaces (screen sides) of the samples 83a, 83b and 83c.
  • Higher values in ml / min when passing on the paper surface mean a higher roughness or, when passing through the paper, a higher porosity.
  • a freeze dryer shown schematically in Fig. 1, has an evacuable drying chamber in which are cool and heated floors. It is thus possible to freeze active ingredients, to cool them, to heat them and to reintroduce the sublimation energy consumed in the course of the drying process (change of state of the water solid - gaseous).
  • the drying chamber is connected via an intermediate valve with the condenser, condenses on the surface of the escaping from the active ingredient water vapor.
  • the condenser usually consists of cooling coils and is cooled with refrigerant from a chiller to low temperatures.
  • a vacuum pump By means of a vacuum pump, the chamber pressure is regulated. After completion of the drying process, the drying chamber is returned to normal pressure via ventilation valves. Freeze dryers can be sterilized by means of steam or gas (H 2 O 2 ).
  • Freeze-drying essentially takes place in 3 main steps, freezing, main drying and post-drying.
  • the process of freeze-drying can be subdivided into 3 steps, which are shown schematically in FIG. 1:
  • the material to be dried is completely frozen so that the water in the material becomes ice.
  • the drying chamber is evacuated by means of a two-stage vacuum pump until it is below the triple point of water.

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  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Molecular Biology (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Paper (AREA)

Abstract

L'invention concerne un mélange de matières fibreuses pour la fabrication de papier ou de produits similaires à du papier, pouvant être obtenu par un procédé comportant les étapes consistant à déshydrater mécaniquement le mélange de matières fibreuses jusqu'à une teneur en matières sèches comprise entre 35 % étuvé et à 80 % étuvé et à lyophiliser le mélange de matières fibreuses.
EP09719270A 2008-03-14 2009-03-16 Dispositif et procédé pour le séchage de matières fibreuses Withdrawn EP2276884A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102008014412 2008-03-14
PCT/EP2009/053102 WO2009112593A1 (fr) 2008-03-14 2009-03-16 Dispositif et procédé pour le séchage de matières fibreuses

Publications (1)

Publication Number Publication Date
EP2276884A1 true EP2276884A1 (fr) 2011-01-26

Family

ID=40804350

Family Applications (1)

Application Number Title Priority Date Filing Date
EP09719270A Withdrawn EP2276884A1 (fr) 2008-03-14 2009-03-16 Dispositif et procédé pour le séchage de matières fibreuses

Country Status (2)

Country Link
EP (1) EP2276884A1 (fr)
WO (1) WO2009112593A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109440202B (zh) * 2018-10-18 2023-09-08 青岛即发集团股份有限公司 一种湿法纺丝真空冷冻干燥方法及干燥设备

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4474949A (en) * 1983-05-06 1984-10-02 Personal Products Company Freeze dried microfibrilar cellulose
FI982540A (fi) * 1998-11-24 2000-05-25 Valmet Corp Laitteisto ja menetelmä sellun kuivaamiseksi

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
None *
See also references of WO2009112593A1 *

Also Published As

Publication number Publication date
WO2009112593A1 (fr) 2009-09-17

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