CA2205394A1 - Thin-film treatment device - Google Patents
Thin-film treatment deviceInfo
- Publication number
- CA2205394A1 CA2205394A1 CA 2205394 CA2205394A CA2205394A1 CA 2205394 A1 CA2205394 A1 CA 2205394A1 CA 2205394 CA2205394 CA 2205394 CA 2205394 A CA2205394 A CA 2205394A CA 2205394 A1 CA2205394 A1 CA 2205394A1
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- CA
- Canada
- Prior art keywords
- rotor
- thin
- treatment apparatus
- film treatment
- cellulose
- 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.)
- Abandoned
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Abstract
The invention relates to a thin-film treatment device with a cylindrical treatment vessel and a rotor fitted centrally therein and having agitators which are movable and are inclined at an angle .alpha. to the rotor axis, in which the rotor has a cylindrical jacket in which rotor blades are fitted to rotate, where the angle of inclination .alpha. can be adjusted via a mechanism fitted inside the rotor.
Description
CA 0220~394 1997-0~-14 ~ ~3~
-THIN-FILM TREATMENT APPARATUS
The present invention is concerned with a thin-film treatment apparatus comprising a cylindrical treatment container and a rotor provided centrically in the treatment container, said rotor having stirring elements which are adjustable and show an inclination angle relative to the axis of the rotor. In particular, the present invention is concerned with a thin-film treatment apparatus for the production of a homogeneous, mouldable, highly viscous solution of cellulose in a tertiary amine-oxide from a suspension of cellulose in a solution of the tertiary amine-oxide in a non-solvent for cellulose, particularly water.
From US-A - 2,179,181 it is known that tertiary amine-oxides are capable of dissolving cellulose and that from these solutions cellulose moulded bodies may be produced by precipitation in an aqueous medium.
In US-A - 4,246,221, a process for the production of mouldable cellulose solutions using as starting material, among other substances, a mixture of cellulose in aqueous N-methylmorpholine-N-oxide (NMMO) is known. The known process is carried out discontinuously, comprising the following 4 steps for obt~ining the spinnable solution:
1. Treating a mixture of pulp in an aqueous solution of NMMO in a mixing vessel by subjecting the mixture to reduced pressure and elevated temperature, a solution being formed;
-THIN-FILM TREATMENT APPARATUS
The present invention is concerned with a thin-film treatment apparatus comprising a cylindrical treatment container and a rotor provided centrically in the treatment container, said rotor having stirring elements which are adjustable and show an inclination angle relative to the axis of the rotor. In particular, the present invention is concerned with a thin-film treatment apparatus for the production of a homogeneous, mouldable, highly viscous solution of cellulose in a tertiary amine-oxide from a suspension of cellulose in a solution of the tertiary amine-oxide in a non-solvent for cellulose, particularly water.
From US-A - 2,179,181 it is known that tertiary amine-oxides are capable of dissolving cellulose and that from these solutions cellulose moulded bodies may be produced by precipitation in an aqueous medium.
In US-A - 4,246,221, a process for the production of mouldable cellulose solutions using as starting material, among other substances, a mixture of cellulose in aqueous N-methylmorpholine-N-oxide (NMMO) is known. The known process is carried out discontinuously, comprising the following 4 steps for obt~ining the spinnable solution:
1. Treating a mixture of pulp in an aqueous solution of NMMO in a mixing vessel by subjecting the mixture to reduced pressure and elevated temperature, a solution being formed;
2. intermediately storing said solution in a tank, 3. intermediately filtering said solution and 4. treating said solution in an extruder to obtain the spinnable solution.
According to this process, cellulose may be dissolved only discontinuously, which moreover is very time-consuming. The dissolution rate is less than 7 g of cellulose per minute.
-CA 0220~394 1997-0~-14 Formerly, the low dissolution rate was not unusual to those skilled in the art, due to the polymer nature of cellulose.
Even during the years following the publication of US-A -4,246,221, those skilled in the art believed that cellulose may be dissolved only in a multi-step process in aqueous amine-oxide solutions. It was supposed that the NMMO process requires in principle two steps to dissolve the cellulose from a suspension. The first step was seen in treating the suspension in a mixing device at reduced pressure while subjecting it to heat to remove water, swell the cellulose and adjust substantially the water concentration which allows the cellulose to dissolve. The second step consisted in processing the swollen cellulose in a double screw extruder having shearing elements, wherein the swollen cellulose finally was transformed into a spinnable solution (D.
Loubinoux and S. Chaunis; "An Experimental Approach to Spinning New Cellulose Fibers with N-Methylmorpholine-Oxide as solvent", Lenzinger Berichte, volume 59, pages 105-107, August 1985). The use of a double screw extruder having shearing elements was proposed to provide the high shearing forces thought to be necessary for the production of spinnable cellulose solutions.
on the other hand, EP-A - 0 356 419 published in 1990 describes a technique whereby it was possible to overcome the multi-step extruder technique and to transform a suspension of cellulose in an aqueous solution of an amine-oxide into a mouldable solution continuously and even in one single step.
According to this technique, first the suspension is spread like a layer on a heating surface while being intensively mixed and treated by transporting it, while intensively mi ~; ng it, across the heating surface, the layer heating up.
Simultaneously, the layer is subjected during the treatment to a reduced pressure in such a way that water evaporates and those concentration conditions are adjusted which according to the phase diagram for the ternary substance mixture cellulose/amine-oxide/water allow for the cellulose to dissolve. Surprisingly, the cellulose dissolves already CA 0220~394 l997-0~-l4 during that stage, i.e. while the layer is transported across the heating surface, so that it is not necessary to use an extruder and the solution may be produced continuously and in one single step.
Moreover, the thin-film technique allows for a significantly faster dissolution of the cellulose than it is possible by means of the two-step extruder technique. This was completely unexpected, since in a thin-film treatment apparatus evidently there do not occur such high shearing forces as are exerted by the shearing elements of a double screw extruder and were considered indispensable to produce a solution.
The thin-film treatment process described above conveniently is carried out in an apparatus as described in EP-A - 0 356 419. This apparatus is called a thin-film treatment apparatus. An embodiment of a thin-film treatment apparatus is for instance a so-called Filmtruder, as manufactured by the company Buss AG (Switzerland). A thin-film treatment apparatus is also described in DE-OS 2 011 493. Moreover, thin-film treatment apparatus are manufactured by the company Focchi, Italy, under the type name SV.
WO 94/ 06530 published in 199 4 uses the thin-film technique known from EP-A - o 356 419 to obtain a mouldable solution from a mixture of cellulose in an aqueous solution of a tertiary amine-oxide. The process is carried out in a Filmtruder, analogously to an embodiment described in EP-A -0 356 419. The process of WO 94/06530 has as its object to save energy and proposes for this purpose to rotate the rotor more slowly.
As mentioned above, the process of WO 94/06530 iS also carried out in a Filmtruder or a thin-film treatment apparatus. In Wo 94/06530 however, this apparatus is referred to as a thin-film evaporator. For the clarity of the present speci~ication and a better understanding of the thin-film technique employed for the production of cellulose solutions CA 0220~394 1997-0~-14 it is pointed out that thin-film treatment apparatus and Filmtruders should not be referred to as thin-film evaporators, since those skilled in the art subsume under thin-film evaporator different apparatus wherein the process according to the invention cannot be carried out. Although thin-film evaporators look similar to those apparatus used in EP-A - 0 356 419 and in WO 94/06530 for the production of the cellulose solution, there are significant operational differences in the design of thin-film evaporators on the one hand and Filmtruders or thin-film treatment apparatus on the other hand. These differences are also pointed out by the manufacturing companies (see e.g. Howard L. Freese and Hans D. Aeppli, "Lowa-Filmtruder Type HS", Fiber Producers Buyers Guide, 2nd edition, page 116, April 1974).
Thin-film evaporators are only appropriate to evaporate volatile components of a liquid able to flow down the heating surface of the thin-film evaporator under the influence of gravity ("Ull m~nns Encyklopadie der technischen Chemie", 4th edition, volume 2, page 657, 1972, Verlag Chemie GmbH, Weinheim/BergstraBe, Germany). Flowing under gravity however requires viscosity not to be too high, the upper limit whereat flowing under gravity is still possible being considered to be 15 Pa.s ("Ull m~nns Encyklopadie der technischen Chemie", 1972, 4th edition, volume 2, page 657).
Mouldable cellulose solutions however may show viscosities of up to 15000 Pa.s. Thus it is evident that such a thin-film evaporator cannot be used to produce highly viscous cellulose solutions.
EP-A - 0 356 419 describes a thin-film treatment apparatus having adjustable rotor blades, so that the inclination angle, i.e. the angle relative to the axis of the rotor formed by the rotor blades, may be adjusted.
Vertical driers comprising a rotor having blades which are rotatable in hinges are also known. Such vertical driers are used for the production of solid matter and crystals from CA 0220~394 1997-0~-14 solutions. The blades swing to and fro while shattering the crystal paste or detaching incrustations from the heating wall (Fritz Widmer: Zum Einsatz von Dunnschichtapparaten bei hochviskosen Medien und bei der Erzeugung von Trockenprodukten; Sonderdruck 95 (1971), pages 772-780, from "Chemikerzeitung").
All the thin-film treatment apparatus of the state of the art have the common drawback that processing a raw material wherein time-dependent processes occur cannot be controlled with satisfactory precision. It would be desirable for instance to control the residence time of the raw material to be processed in dependence of these time-dependent products, for instance to discharge a product produced in the thin-film treatment apparatus during the treatment as rapidly as possible, for example when decomposition processes occur in the product which have a negative effect on the quality of the final product. Moreover it may be advantageous to carry out certain processes such as the dissolution of a solid in a solvent at a certain level of the thin-film treatment appratus, whereat e.g. the exact temperature for dissolving may be adjusted.
It is the object of the present invention to provide a thin-film treatment apparatus wherein the residence time of the raw material to be treated may be controlled and adjusted to the specific requirements of each individual case.
The thin-film treatment apparatus according to the invention comprising a cylindrical treatment container and a rotor provided centrically in the treatment container, said rotor having stirring elements which are adjustable and show an inclination angle relative to the axis of the rotor is characterized in that the rotor has a cylindrical jacket wherein rotor blades are provided rotatably, the inclination angle being adjustable by means of a mechanism provided in the interior of the rotor. Thus the rotor blades are adjusted not from the outside but from the inside. An adjustment CA 0220~394 1997-0~-14 mechanism in the interior of the rotor allows an adjustment of the inclination angle without having to remove the rotor from the thin-film treatment apparatus. Therefore it is very easy to adjust the inclination angle of the rotor blades relative to the axis of the rotor by means of the exhaust vapour pipe of the thin-film treatment apparatus and thus to control the transport rate of the raw material to be treated across the heating surface.
The mechanism whereby the inclination angle may be adjusted comprises substantially at least one support plate provided within the rotor in a right angle relative to the axis of the rotor, and at least one positioning element rigidly connected to a rotor blade, the rotor blade being moved by an axial movement of the support plate.
A preferred embodiment of the thin-film treatment apparatus according to the invention is characterized in that the at least one support plate is moved by rotation of a shaft arranged centrically in the cylindrical rotor and passing through the center of the at least one support plate, said shaft having a screw thread at its outside which indents into a counterscrew provided in the interior of a cylindrical tube, whereto the at least one support plate is attached.
A further preferred embodiment of the thin-film treatment apparatus according to the invention is characterized in that at least two support plates are provided which may be moved independently from each other in the direction of the axis of the rotor.
In this embodiment of the thin-film treatment apparatus according to the invention it is possible to provide at least two zones having different transport rates of the material to be treated.
It has proven advantageous for the rotor to comprise 20 to 50 rotor blades per square meter of surface of the rotor jacket.
-CA 0220~394 1997-0~-14 It has been shown that the thin-film treatment apparatus according to the invention is highly appropriate to transform suspensions of cellulose into mouldable solutions. Thus the invention is further concerned with the use of the thin-film treatment apparatus according to the invention for producing a mouldable cellulose solution from a suspension of cellulose in a solution of a tertiary amine-oxide in a non-solvent ~or cellulose, particularly water. A suspension processed advantageously by means of the thin-film treatment apparatus according to the invention contains: from 50 to 72~ by mass of NMMO, from 19 to 40% by mass of water and from 7 to 14% by mass of cellulose.
By means of the attached drawing, the invention will be explained in more detail. In Figure 1, the drawing shows a partial longitudinal section of a known Filmtruder (see e.g.
Erich Heimgartner, "Devolatilisation of Plastics", in Ingenieurwissen, pages 69-97, Dusseldorf 1980, VDI-Verlag GmbH).
1 indicates the internal wall of a preferably vertical rotational body, which in the exemplary embodiment illustrated is designed as a cylindrical container 2 almost over its entire length. For the major part, the internal wall 1 is surrounded by a heating jacket 3 having connection means 4 and 5 for the heating medium, connection means 4 serving to supply the heating medium and connection means 5 serving to withdraw it.
In container 2, a rotor having rotor blades 8 joined thereto driven by motor 6 is provided centrically. The rotor blades 8 show an inclination angle a relative to the axis 9 of rotor 7.
Above the rotor blades 8, a distribution ring 10 is attached to rotor 7, which ring spreads the cellulose suspension introduced through intake 11 in layers on the internal wall CA 0220~394 1997-0~-14 1. Thus distribution ring 10 is provided at the level of the intake 11.
At its lower end, container 2 is frustoconically tapered having an outlet 12 for the homogeneous cellulose solution.
Rotor blades 8 have a radial clearance 13 to the internal wall 1 of container 2 over the total extension of container 2, which clearance is 20 mm at most and may be constant or may vary over the length of container 2.
At the upper portion of container 2, namely above the level of distribution ring 10, an opening 14 is provided for evacuating container 2 and for drawing off water vapour.
The mode of operation of the device is as follows:
Cellulose suspension - optionally in a pre-temperated state -is fed continuously through intake 11 into container 2 being under a reduced pressure, is seized there by distribution ring 10, is spread on the internal wall and is transported by rotor blades 8 along the indirectly heated internal wall 1 serving as heating surface, to outlet 12 at the lower end of container 2. Heat carrier media such as water, oil or vapour are suited for indirect heating.
The cellulose suspension is heated during its transportation along the indirectly heated internal wall 1, and simultaneously water evaporates due to the reduced pressure, so that the tertiary amine-oxide becomes concentrated and the state wherein the cellulose may be dissolved is reached. Due to constant circulation and mixing of the cellulose suspension within the thin film, the cellulose dissolves in a very short period of time.
Due to the inclination angle a of rotor blades 8 relative to the axis of the rotor, the suspension is transported downwards.
CA 0220~394 1997-0~-14 When gliding over the suspension, each rotor blade 8 of a vertical row of rotor blades transports it a little bit downwards, whereafter it is seized by a rotor blade of the following row of rotor blades, spread and transported still more downwards. This transport naturally requires an overlapping of the areas over which each of the rotor blades glides.
Water vapour should be drawn off in counterflow relative to the transport direction of the suspension. For a rapid drawing-off of water vapour, a sufficiently large exhaust vapour space should be provided, which is the case when the ratio of length to diamenter of the cylindrical portion of container 2 amounts to between 4 and 8.
By means of the Figures 2, 3, 4, 5 and 6, an embodiment of the rotor of a thin-film treatment apparatus according to the invention will be explained in more detail.
Figure 2 shows a horizontal section through a cylindrical, pipe-shaped rotor having a jacket which is shown in Figure 2 as a ring having reference number 7a. The rotor comprises fourteen rotor blades 8 at the section level. Each of the rotor blades 8 is provided rotatably in sockets 14 incorporated into jacket 7a of the rotor. Each rotor blade 8 is moved by means of a positioning element 15a.
Figure 3 shows a section of Figure 2 on an enlarged scale.
Figure 3 shows a rotor blade 8 provided rotatably in socket or shell 14. Rotor blade 8 protrudes into the interior of the rotor by means of its bar-shaped prolongation 8a and is connected with positioning element 15a by means of a safety element 8b.
From Figure 4 illustrating a portion of an embodiment of the rotor according to the invention it can be seen that the positioning element 15a is connected to an intermediate element 15c by means of a link 15b, which intermediate CA 0220~394 1997-0~-14 element 15c again is connected to a base 15e mounted rigidly to a support plate 16 by means of a link 15d. Support plate 16 comprises in its center a pipe-shaped shell 17 having an inner screw thread indenting into the counterscrew of a hollow shaft 18. By rotating hollow shaft 18, support plate 16 can be moved upwards and downwards. This movement is transmitted to positioning element 15a rotating the rotor blade 8 by means of base 15e and intermediate element 15c.
Thus the inclination angle a is changed.
Figure 4 shows only one single support plate 16 which can be moved by means of hollow shaft 17. It is evident that several support plates 16 lying one above the other may be provided.
These support plates are moved simultaneously, changing the inclination angle of their respective rotor blades 8 to the same extent.
In the embodiment shown in Figure 4, the rotor according to the invention also comprises also a full shaft 19 partly conducted in hollow shaft 18 and able to move support plates 16a by rotating. Figure 4 shows two support plates 16a provided one above the other. Usually however several support plates 16a will be provided. This embodiment enables the movement of support plates 16a independently of support plate 16 and thus the separate changing of the inclination angles.
It is obvlous to those skilled in the art that in the way described several hollow shafts may be provided to have a still greater flexibility in adjusting the inclination angles of the rotor blades.
Full shaft 19 is provided rotatably in a conventional manner in the bottom of the rotor according to the invention.
The mechanical connection means of the rotor shown in Figure 4 to primary shaft 27 of the thin-film treatment apparatus is referred to by reference number 24.
~ =
CA 0220~394 1997-0~-14 Mechanism 43 for rotating hollow shaft 18 and full shaft 19 shown in Figure 4 may be operated through openings 42 provided in connection means 24. This mechanism 43 is shown in detail in Figure S.
Figure 5 shows hollow shaft 18 fitted into the upper portion 7b of the rotor jacket by means of a circular spacer 2Oa. On spacer 20a, a ring 21a having a positive and force transmitting connection to hollow shaft 18 is provided. The positive and force transmitting connection is indicated by reference number 22a. By rotating ring 21a, hollow shaft 18 may be rotated. After rotation, the position of hollow shaft 18 is fixed by means of nut 23a.
Rotation of full shaft 19 is achieved analogously: Full shaft 19 is fitted into the upper portion of hollow shaft 18 by means of a circular spacer 2Ob. On spacer 2Ob, a ring 2lb having a positive and force transmitting connection to full shaft 19 is provided. The positive and force transmitting connection is indicated by reference number 22b. By rotating ring 21b, full shaft 19 may be rotated. After rotation, the position of full shaft 19 is fixed by means of nut 23b.
Figure 6 shows the bearing of the primary shaft 27 of the thin-film treatment apparatus. This primary shaft 27 is connected to the motor (not shown) by means of coupling flange 25, which motor is again connected at its pinion end to a counter-coupling flange (not shown). Reference number 26 indicates also a coupling having little elasticity to be able to level out possible inclinations between the motor and primary shaft 27.
The bearing of primary shaft 27 is provided by means of bearing 32 arranged in bearing case 31. Moreover, bearing 32 is provided on a shaft-protecting shell 29. Reference number 28 refers to a bearing lid 28.
CA 0220~394 l997-0~-l4 Since the thin-film treatment apparatus may be operated also under reduced pressure, a floating ring seal 44 sealing against ambient pressure is provided. This floating ring seal 44 is provided within a pipe-shaped sealing case 34 and base flange 35 upon centering flange 36. Since floating ring seal 44 is operated with a sealing liquid (not shown) provided in the interior of sealing case 34, sealing rings 30, 33 are provided, so that on the one hand no sealing liquid may leak to the outside and on the other no dust from outside may penetrate into bearing 3 2 .
Reference number 37 indicates a counterflange provided at the upper portion 39 of the thin-film treatment apparatus, which counterflange is connected to base flange 35 of sealing case 34 and centering flange 36 by means of screws 38.
Reference numbers 40 and 41 indicate the coupling to the rotor or the drive type fastening at the rotor.
Reference number 24 denotes the connection means of the rotor having a positive and force transmitting connection to primary shaft 27. This connection means 24 has lateral openings 42 whereby the adjustment mechanism may be operated.
Opening 42 may be reached by means of opening 14 provided for the evacuation and discharge of exhaust vapours.
According to this process, cellulose may be dissolved only discontinuously, which moreover is very time-consuming. The dissolution rate is less than 7 g of cellulose per minute.
-CA 0220~394 1997-0~-14 Formerly, the low dissolution rate was not unusual to those skilled in the art, due to the polymer nature of cellulose.
Even during the years following the publication of US-A -4,246,221, those skilled in the art believed that cellulose may be dissolved only in a multi-step process in aqueous amine-oxide solutions. It was supposed that the NMMO process requires in principle two steps to dissolve the cellulose from a suspension. The first step was seen in treating the suspension in a mixing device at reduced pressure while subjecting it to heat to remove water, swell the cellulose and adjust substantially the water concentration which allows the cellulose to dissolve. The second step consisted in processing the swollen cellulose in a double screw extruder having shearing elements, wherein the swollen cellulose finally was transformed into a spinnable solution (D.
Loubinoux and S. Chaunis; "An Experimental Approach to Spinning New Cellulose Fibers with N-Methylmorpholine-Oxide as solvent", Lenzinger Berichte, volume 59, pages 105-107, August 1985). The use of a double screw extruder having shearing elements was proposed to provide the high shearing forces thought to be necessary for the production of spinnable cellulose solutions.
on the other hand, EP-A - 0 356 419 published in 1990 describes a technique whereby it was possible to overcome the multi-step extruder technique and to transform a suspension of cellulose in an aqueous solution of an amine-oxide into a mouldable solution continuously and even in one single step.
According to this technique, first the suspension is spread like a layer on a heating surface while being intensively mixed and treated by transporting it, while intensively mi ~; ng it, across the heating surface, the layer heating up.
Simultaneously, the layer is subjected during the treatment to a reduced pressure in such a way that water evaporates and those concentration conditions are adjusted which according to the phase diagram for the ternary substance mixture cellulose/amine-oxide/water allow for the cellulose to dissolve. Surprisingly, the cellulose dissolves already CA 0220~394 l997-0~-l4 during that stage, i.e. while the layer is transported across the heating surface, so that it is not necessary to use an extruder and the solution may be produced continuously and in one single step.
Moreover, the thin-film technique allows for a significantly faster dissolution of the cellulose than it is possible by means of the two-step extruder technique. This was completely unexpected, since in a thin-film treatment apparatus evidently there do not occur such high shearing forces as are exerted by the shearing elements of a double screw extruder and were considered indispensable to produce a solution.
The thin-film treatment process described above conveniently is carried out in an apparatus as described in EP-A - 0 356 419. This apparatus is called a thin-film treatment apparatus. An embodiment of a thin-film treatment apparatus is for instance a so-called Filmtruder, as manufactured by the company Buss AG (Switzerland). A thin-film treatment apparatus is also described in DE-OS 2 011 493. Moreover, thin-film treatment apparatus are manufactured by the company Focchi, Italy, under the type name SV.
WO 94/ 06530 published in 199 4 uses the thin-film technique known from EP-A - o 356 419 to obtain a mouldable solution from a mixture of cellulose in an aqueous solution of a tertiary amine-oxide. The process is carried out in a Filmtruder, analogously to an embodiment described in EP-A -0 356 419. The process of WO 94/06530 has as its object to save energy and proposes for this purpose to rotate the rotor more slowly.
As mentioned above, the process of WO 94/06530 iS also carried out in a Filmtruder or a thin-film treatment apparatus. In Wo 94/06530 however, this apparatus is referred to as a thin-film evaporator. For the clarity of the present speci~ication and a better understanding of the thin-film technique employed for the production of cellulose solutions CA 0220~394 1997-0~-14 it is pointed out that thin-film treatment apparatus and Filmtruders should not be referred to as thin-film evaporators, since those skilled in the art subsume under thin-film evaporator different apparatus wherein the process according to the invention cannot be carried out. Although thin-film evaporators look similar to those apparatus used in EP-A - 0 356 419 and in WO 94/06530 for the production of the cellulose solution, there are significant operational differences in the design of thin-film evaporators on the one hand and Filmtruders or thin-film treatment apparatus on the other hand. These differences are also pointed out by the manufacturing companies (see e.g. Howard L. Freese and Hans D. Aeppli, "Lowa-Filmtruder Type HS", Fiber Producers Buyers Guide, 2nd edition, page 116, April 1974).
Thin-film evaporators are only appropriate to evaporate volatile components of a liquid able to flow down the heating surface of the thin-film evaporator under the influence of gravity ("Ull m~nns Encyklopadie der technischen Chemie", 4th edition, volume 2, page 657, 1972, Verlag Chemie GmbH, Weinheim/BergstraBe, Germany). Flowing under gravity however requires viscosity not to be too high, the upper limit whereat flowing under gravity is still possible being considered to be 15 Pa.s ("Ull m~nns Encyklopadie der technischen Chemie", 1972, 4th edition, volume 2, page 657).
Mouldable cellulose solutions however may show viscosities of up to 15000 Pa.s. Thus it is evident that such a thin-film evaporator cannot be used to produce highly viscous cellulose solutions.
EP-A - 0 356 419 describes a thin-film treatment apparatus having adjustable rotor blades, so that the inclination angle, i.e. the angle relative to the axis of the rotor formed by the rotor blades, may be adjusted.
Vertical driers comprising a rotor having blades which are rotatable in hinges are also known. Such vertical driers are used for the production of solid matter and crystals from CA 0220~394 1997-0~-14 solutions. The blades swing to and fro while shattering the crystal paste or detaching incrustations from the heating wall (Fritz Widmer: Zum Einsatz von Dunnschichtapparaten bei hochviskosen Medien und bei der Erzeugung von Trockenprodukten; Sonderdruck 95 (1971), pages 772-780, from "Chemikerzeitung").
All the thin-film treatment apparatus of the state of the art have the common drawback that processing a raw material wherein time-dependent processes occur cannot be controlled with satisfactory precision. It would be desirable for instance to control the residence time of the raw material to be processed in dependence of these time-dependent products, for instance to discharge a product produced in the thin-film treatment apparatus during the treatment as rapidly as possible, for example when decomposition processes occur in the product which have a negative effect on the quality of the final product. Moreover it may be advantageous to carry out certain processes such as the dissolution of a solid in a solvent at a certain level of the thin-film treatment appratus, whereat e.g. the exact temperature for dissolving may be adjusted.
It is the object of the present invention to provide a thin-film treatment apparatus wherein the residence time of the raw material to be treated may be controlled and adjusted to the specific requirements of each individual case.
The thin-film treatment apparatus according to the invention comprising a cylindrical treatment container and a rotor provided centrically in the treatment container, said rotor having stirring elements which are adjustable and show an inclination angle relative to the axis of the rotor is characterized in that the rotor has a cylindrical jacket wherein rotor blades are provided rotatably, the inclination angle being adjustable by means of a mechanism provided in the interior of the rotor. Thus the rotor blades are adjusted not from the outside but from the inside. An adjustment CA 0220~394 1997-0~-14 mechanism in the interior of the rotor allows an adjustment of the inclination angle without having to remove the rotor from the thin-film treatment apparatus. Therefore it is very easy to adjust the inclination angle of the rotor blades relative to the axis of the rotor by means of the exhaust vapour pipe of the thin-film treatment apparatus and thus to control the transport rate of the raw material to be treated across the heating surface.
The mechanism whereby the inclination angle may be adjusted comprises substantially at least one support plate provided within the rotor in a right angle relative to the axis of the rotor, and at least one positioning element rigidly connected to a rotor blade, the rotor blade being moved by an axial movement of the support plate.
A preferred embodiment of the thin-film treatment apparatus according to the invention is characterized in that the at least one support plate is moved by rotation of a shaft arranged centrically in the cylindrical rotor and passing through the center of the at least one support plate, said shaft having a screw thread at its outside which indents into a counterscrew provided in the interior of a cylindrical tube, whereto the at least one support plate is attached.
A further preferred embodiment of the thin-film treatment apparatus according to the invention is characterized in that at least two support plates are provided which may be moved independently from each other in the direction of the axis of the rotor.
In this embodiment of the thin-film treatment apparatus according to the invention it is possible to provide at least two zones having different transport rates of the material to be treated.
It has proven advantageous for the rotor to comprise 20 to 50 rotor blades per square meter of surface of the rotor jacket.
-CA 0220~394 1997-0~-14 It has been shown that the thin-film treatment apparatus according to the invention is highly appropriate to transform suspensions of cellulose into mouldable solutions. Thus the invention is further concerned with the use of the thin-film treatment apparatus according to the invention for producing a mouldable cellulose solution from a suspension of cellulose in a solution of a tertiary amine-oxide in a non-solvent ~or cellulose, particularly water. A suspension processed advantageously by means of the thin-film treatment apparatus according to the invention contains: from 50 to 72~ by mass of NMMO, from 19 to 40% by mass of water and from 7 to 14% by mass of cellulose.
By means of the attached drawing, the invention will be explained in more detail. In Figure 1, the drawing shows a partial longitudinal section of a known Filmtruder (see e.g.
Erich Heimgartner, "Devolatilisation of Plastics", in Ingenieurwissen, pages 69-97, Dusseldorf 1980, VDI-Verlag GmbH).
1 indicates the internal wall of a preferably vertical rotational body, which in the exemplary embodiment illustrated is designed as a cylindrical container 2 almost over its entire length. For the major part, the internal wall 1 is surrounded by a heating jacket 3 having connection means 4 and 5 for the heating medium, connection means 4 serving to supply the heating medium and connection means 5 serving to withdraw it.
In container 2, a rotor having rotor blades 8 joined thereto driven by motor 6 is provided centrically. The rotor blades 8 show an inclination angle a relative to the axis 9 of rotor 7.
Above the rotor blades 8, a distribution ring 10 is attached to rotor 7, which ring spreads the cellulose suspension introduced through intake 11 in layers on the internal wall CA 0220~394 1997-0~-14 1. Thus distribution ring 10 is provided at the level of the intake 11.
At its lower end, container 2 is frustoconically tapered having an outlet 12 for the homogeneous cellulose solution.
Rotor blades 8 have a radial clearance 13 to the internal wall 1 of container 2 over the total extension of container 2, which clearance is 20 mm at most and may be constant or may vary over the length of container 2.
At the upper portion of container 2, namely above the level of distribution ring 10, an opening 14 is provided for evacuating container 2 and for drawing off water vapour.
The mode of operation of the device is as follows:
Cellulose suspension - optionally in a pre-temperated state -is fed continuously through intake 11 into container 2 being under a reduced pressure, is seized there by distribution ring 10, is spread on the internal wall and is transported by rotor blades 8 along the indirectly heated internal wall 1 serving as heating surface, to outlet 12 at the lower end of container 2. Heat carrier media such as water, oil or vapour are suited for indirect heating.
The cellulose suspension is heated during its transportation along the indirectly heated internal wall 1, and simultaneously water evaporates due to the reduced pressure, so that the tertiary amine-oxide becomes concentrated and the state wherein the cellulose may be dissolved is reached. Due to constant circulation and mixing of the cellulose suspension within the thin film, the cellulose dissolves in a very short period of time.
Due to the inclination angle a of rotor blades 8 relative to the axis of the rotor, the suspension is transported downwards.
CA 0220~394 1997-0~-14 When gliding over the suspension, each rotor blade 8 of a vertical row of rotor blades transports it a little bit downwards, whereafter it is seized by a rotor blade of the following row of rotor blades, spread and transported still more downwards. This transport naturally requires an overlapping of the areas over which each of the rotor blades glides.
Water vapour should be drawn off in counterflow relative to the transport direction of the suspension. For a rapid drawing-off of water vapour, a sufficiently large exhaust vapour space should be provided, which is the case when the ratio of length to diamenter of the cylindrical portion of container 2 amounts to between 4 and 8.
By means of the Figures 2, 3, 4, 5 and 6, an embodiment of the rotor of a thin-film treatment apparatus according to the invention will be explained in more detail.
Figure 2 shows a horizontal section through a cylindrical, pipe-shaped rotor having a jacket which is shown in Figure 2 as a ring having reference number 7a. The rotor comprises fourteen rotor blades 8 at the section level. Each of the rotor blades 8 is provided rotatably in sockets 14 incorporated into jacket 7a of the rotor. Each rotor blade 8 is moved by means of a positioning element 15a.
Figure 3 shows a section of Figure 2 on an enlarged scale.
Figure 3 shows a rotor blade 8 provided rotatably in socket or shell 14. Rotor blade 8 protrudes into the interior of the rotor by means of its bar-shaped prolongation 8a and is connected with positioning element 15a by means of a safety element 8b.
From Figure 4 illustrating a portion of an embodiment of the rotor according to the invention it can be seen that the positioning element 15a is connected to an intermediate element 15c by means of a link 15b, which intermediate CA 0220~394 1997-0~-14 element 15c again is connected to a base 15e mounted rigidly to a support plate 16 by means of a link 15d. Support plate 16 comprises in its center a pipe-shaped shell 17 having an inner screw thread indenting into the counterscrew of a hollow shaft 18. By rotating hollow shaft 18, support plate 16 can be moved upwards and downwards. This movement is transmitted to positioning element 15a rotating the rotor blade 8 by means of base 15e and intermediate element 15c.
Thus the inclination angle a is changed.
Figure 4 shows only one single support plate 16 which can be moved by means of hollow shaft 17. It is evident that several support plates 16 lying one above the other may be provided.
These support plates are moved simultaneously, changing the inclination angle of their respective rotor blades 8 to the same extent.
In the embodiment shown in Figure 4, the rotor according to the invention also comprises also a full shaft 19 partly conducted in hollow shaft 18 and able to move support plates 16a by rotating. Figure 4 shows two support plates 16a provided one above the other. Usually however several support plates 16a will be provided. This embodiment enables the movement of support plates 16a independently of support plate 16 and thus the separate changing of the inclination angles.
It is obvlous to those skilled in the art that in the way described several hollow shafts may be provided to have a still greater flexibility in adjusting the inclination angles of the rotor blades.
Full shaft 19 is provided rotatably in a conventional manner in the bottom of the rotor according to the invention.
The mechanical connection means of the rotor shown in Figure 4 to primary shaft 27 of the thin-film treatment apparatus is referred to by reference number 24.
~ =
CA 0220~394 1997-0~-14 Mechanism 43 for rotating hollow shaft 18 and full shaft 19 shown in Figure 4 may be operated through openings 42 provided in connection means 24. This mechanism 43 is shown in detail in Figure S.
Figure 5 shows hollow shaft 18 fitted into the upper portion 7b of the rotor jacket by means of a circular spacer 2Oa. On spacer 20a, a ring 21a having a positive and force transmitting connection to hollow shaft 18 is provided. The positive and force transmitting connection is indicated by reference number 22a. By rotating ring 21a, hollow shaft 18 may be rotated. After rotation, the position of hollow shaft 18 is fixed by means of nut 23a.
Rotation of full shaft 19 is achieved analogously: Full shaft 19 is fitted into the upper portion of hollow shaft 18 by means of a circular spacer 2Ob. On spacer 2Ob, a ring 2lb having a positive and force transmitting connection to full shaft 19 is provided. The positive and force transmitting connection is indicated by reference number 22b. By rotating ring 21b, full shaft 19 may be rotated. After rotation, the position of full shaft 19 is fixed by means of nut 23b.
Figure 6 shows the bearing of the primary shaft 27 of the thin-film treatment apparatus. This primary shaft 27 is connected to the motor (not shown) by means of coupling flange 25, which motor is again connected at its pinion end to a counter-coupling flange (not shown). Reference number 26 indicates also a coupling having little elasticity to be able to level out possible inclinations between the motor and primary shaft 27.
The bearing of primary shaft 27 is provided by means of bearing 32 arranged in bearing case 31. Moreover, bearing 32 is provided on a shaft-protecting shell 29. Reference number 28 refers to a bearing lid 28.
CA 0220~394 l997-0~-l4 Since the thin-film treatment apparatus may be operated also under reduced pressure, a floating ring seal 44 sealing against ambient pressure is provided. This floating ring seal 44 is provided within a pipe-shaped sealing case 34 and base flange 35 upon centering flange 36. Since floating ring seal 44 is operated with a sealing liquid (not shown) provided in the interior of sealing case 34, sealing rings 30, 33 are provided, so that on the one hand no sealing liquid may leak to the outside and on the other no dust from outside may penetrate into bearing 3 2 .
Reference number 37 indicates a counterflange provided at the upper portion 39 of the thin-film treatment apparatus, which counterflange is connected to base flange 35 of sealing case 34 and centering flange 36 by means of screws 38.
Reference numbers 40 and 41 indicate the coupling to the rotor or the drive type fastening at the rotor.
Reference number 24 denotes the connection means of the rotor having a positive and force transmitting connection to primary shaft 27. This connection means 24 has lateral openings 42 whereby the adjustment mechanism may be operated.
Opening 42 may be reached by means of opening 14 provided for the evacuation and discharge of exhaust vapours.
Claims (6)
1. A thin-film treatment apparatus comprising a cylindrical treatment container and a rotor provided centrically in said treatment container, said rotor having stirring elements which are adjustable and show an inclination angle a relative to the axis of said rotor, characterized in that said rotor (7) has a cylindrical jacket (7a) wherein rotor blades (8) are provided rotatably, said inclination angle a being adjustable by means of a mechanism provided in the interior of said rotor (7).
2. A thin-film treatment apparatus according to Claim 1, characterized in that the mechanism whereby said inclination angle a may be adjusted comprises at least one support plate (16) provided within said rotor (7) in a right angle relative to the axis of said rotor (7), and at least one positioning element (15d; 15a) rigidly connected to a rotor blade (8), said rotor blade (8) being moved by an axial movement of said support plate (16; 16a).
3. A thin-film treatment apparatus according to Claim 2, characterized in that said at least one support plate (16; 16a) is moved by rotation of a shaft (18; 19) arranged centrically in said cylindrical rotor (7) and passing through the center of the at least one support plate (16; 16a), said shaft (18; 19) having a screw thread at its outside which indents into a counterscrew provided in the interior of a cylindrical tube (17; 17a) whereto said at least one support plate (16; 16a) is attached.
4. A thin-film treatment apparatus according to Claim 3, characterized in that at least two support plates (16;
16a) are provided which may be moved independently from each other in the direction of the axis of said rotor (7).
16a) are provided which may be moved independently from each other in the direction of the axis of said rotor (7).
5. A thin-film treatment apparatus according to one of the Claims 1 to 4, characterized in that said rotor (7) comprises 20 to 50 rotor blades per square meter of surface of said jacket (7a).
6. Use of a thin-film treatment apparatus according to one of the Claims 1 to 5 for producing a mouldable cellulose solution from a suspension of cellulose in a solution of a tertiary amine-oxide in a non-solvent for cellulose.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ATATA1605/95 | 1995-09-27 | ||
| AT0160595A AT402902B (en) | 1995-09-27 | 1995-09-27 | THIN-LAYER TREATMENT APPARATUS |
| PCT/AT1996/000172 WO1997011973A1 (en) | 1995-09-27 | 1996-09-24 | Thin-film treatment device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2205394A1 true CA2205394A1 (en) | 1997-04-03 |
Family
ID=29401985
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2205394 Abandoned CA2205394A1 (en) | 1995-09-27 | 1996-09-24 | Thin-film treatment device |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2205394A1 (en) |
-
1996
- 1996-09-24 CA CA 2205394 patent/CA2205394A1/en not_active Abandoned
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