THIN-LAYER TREATMENT DEVICE

Abstract

A thin-film treatment apparatus for treating viscous material includes a process housing oriented at an incline of at most 20° with a heatable and/or coolable housing casing, which surrounds a housing interior forming a material treatment space, an inlet nozzle arranged in an inlet zone of the process housing to introduce the material to be treated into the material treatment space, an outlet nozzle arranged in an outlet zone of the process housing to discharge the treated material from the material treatment space, and a drivable rotor shaft arranged in the material treatment space and extending coaxially for producing a material film on the inner surface of the housing casing and for conveying the material in the direction of an outlet zone.

The rotor shaft includes at least one lift element arranged on the rotor shaft body, for producing a lifting force in the direction of the rotating rotor shaft body.

Claims

1. A thin-film treatment apparatus for treating viscous material comprising: a process housing oriented at an incline to the horizontal of at most 20° with a heatable and/or coolable housing casing, which surrounds a rotationally symmetrical housing interior extending in the axial direction and forming a material treatment space; an inlet nozzle arranged in an inlet zone of the process housing in order to introduce the material to be treated into the material treatment space; an outlet nozzle arranged in an outlet zone of the process housing in order to discharge the treated material from the material treatment space; and a drivable rotor shaft arranged in the material treatment space and extending coaxially for producing a material film on the inner surface of the housing casing and for conveying the material in a direction from the inlet zone via a process zone to an outlet zone; wherein the rotor shaft comprises a central rotor shaft body and, arranged on the circumference thereof, sweeper elements, of which the radially outermost end is distanced from the inner surface of the housing casing; and the rotor shaft comprises at least one lift element arranged on the rotor shaft body, which lift element is designed in such a way as to produce a lifting force in the direction of the rotor shaft body during the rotation of the rotor shaft.

2. The thin-film treatment apparatus according to claim 1, characterised in that the lift element has a planar incident-flow portion with a leading end in the rotation direction, which end is arranged at a greater distance from the inner surface of the housing casing than a region of the incident-flow portion trailing behind the leading end, whereby a gap that narrows in a direction opposite the rotation direction is formed between the incident-flow portion and the inner surface of the housing, in particular a continuously narrowing gap.

3. The thin-film treatment apparatus according to claim 2, characterised in that the incident-flow portion covers an angular range β.sub.1 of at least 10° of the circumference of the rotor shaft body.

4. The thin-film treatment apparatus according to claim 1, characterised in that at least a part of the lift elements is formed in each case by a sweeper element.

5. The thin-film treatment apparatus according to claim 1, characterised in that the lift element comprises an at least approximately pitched-roof-shaped web plate, the ridge of which runs at least approximately parallel to the axis direction of the rotor shaft.

6. The thin-film treatment apparatus according to claim 1, characterised in that the lift element, in particular the web plate, has at least one helically running conveying fin on its radial outer side.

7. The thin-film treatment apparatus according to claim 1, characterised in that at least a part of the lift elements is arranged in a region which lies centrally between the rotary bearings on which the rotor shaft is supported, preferably in the process zone.

8. Use of a thin-film treatment apparatus according to claim 1 for the treatment of a material having a viscosity of 100 Pa.Math.s or more at least temporarily during the treatment.

9. A method for producing a solution of cellulose with a solvent from a suspension of cellulose in the solvent and a volatile non-solvent, comprising: the introduction of the suspension into an inlet of a thin-film treatment apparatus; application and distribution of the suspension in a film-like form on a housing casing, temperature-controlled using a heat exchanger, by sweeper elements rotating about a common axis in a process housing of the thin-film treatment apparatus; evaporation of volatile non-solvent so that the cellulose is dissolved; and output of the solution of cellulose from the thin-film treatment apparatus through an outlet; at least a part of the sweeper elements cause the cellulose to be advanced in the direction of the outlet so that the discharge at the outlet is between 300 kg/h and 600 kg/h, preferably between 350 kg/h and 550 kg/h, and particularly preferably between 380 kg/h and 480 kg/h cellulose solution per m.sup.2 of the temperature-controlled surface of the housing casing.

10. The method according to claim 9, characterised in that the specific area ratio of the sweeper elements lies below 10 m.sup.2s/m.sup.3, wherein the specific area ratio of the sweeper elements is given by the formula $A_R=\frac{A_M}{A_B*v_u}$ with A.sub.R . . . specific area ratio of the sweeper elements in m.sup.2s/m.sup.3, A.sub.M . . . casing inner surface in a process zone in the thin-film treatment apparatus in m.sup.2, A.sub.B . . . sweeper element loading area in m.sup.2, V.sub.u . . . circumferential speed of the sweeper element tip in m/s.

11. The method according to claim 9, further including at least one of: a) the specific loading in an inlet zone is 80 kg/h/dm.sup.3-380 kg/h/dm.sup.3, and b) the specific loading in a process zone is 65 kg/h/dm.sup.3-260 kg/h/dm.sup.3, and c) the specific loading in an outlet zone is 2 kg/h/dm.sup.3-125 kg/h/dm.sup.3, and d) the specific loading in a post-processing zone is 0 kg/h/dm.sup.3-500 kg/h/dm.sup.3.

12. The method according to claim 9, characterised in that the treatment time from introduction of the suspension to output of the cellulose solution or to dissolution of the cellulose is at least 60 s.

13. The method according to claim 9, further including at least one of that the engaging-tip power lies in the range of 1.1 kg/sm.sup.2-5.5 kg/sm.sup.2, and that the surface of the housing casing temperature-controlled using a heat exchanger is 0.5 m.sup.2 to 150 m.sup.2.

14. The method according to claim 9, further including at least one of that the radially outermost end of the sweeper elements is moved at a speed of from 1.5 m/s to 12.5 m/s by the rotation of the sweeper elements, and that sweeper elements are moved at a frequency of from 1500 to 4000 per min in succession over a portion of the housing casing temperature-controlled using a heat exchanger, and that sweeper elements arranged directly in succession follow on from one another with a spacing of from 100 mm to 300 mm between the radially outermost ends of the sweeper elements.

15. The method according to claim 9, further including at least one of that the suspension is applied with a film thickness of from 1 mm to 50 mm, and that a sweeper element is in contact with the suspension or solution on average over an area of from 0.8 dm.sup.2 to 2 dm.sup.2, and that the suspension has a film thickness according to formula s=(ln(m.sub.s/60))/x, wherein s is the film thickness in mm, m.sub.s is the conveyed flow of the suspension, and x is a constant of from 0.45 to 7, preferably of 0.5866.

Description

[0120] In the figures:

[0121] FIG. 1 shows a schematic depiction of a thin-film treatment apparatus according to the invention in a side view;

[0122] FIG. 2 shows the thin-film treatment apparatus shown in FIG. 1 in a view from above;

[0123] FIG. 3 shows a further thin-film treatment apparatus from above;

[0124] FIG. 4 shows the process housing of the thin-film treatment apparatus shown in FIG. 3 in cross-section through the plane A-A of FIG. 3;

[0125] FIG. 5 shows a part of a rotor shaft for the apparatus according to the invention in a perspective view;

[0126] FIG. 6 shows a perspective view of a part of a further rotor shaft of a thin-film treatment apparatus according to the invention in the region corresponding to the inlet zone;

[0127] FIG. 7 shows the rotor shaft shown in FIG. 6 and arranged in a process housing in cross-section;

[0128] FIG. 8 shows a side view of the outlet zone of a further embodiment of the thin-film treatment apparatus according to the invention with a vertically extending discharge system;

[0129] FIG. 9 shows the outlet zone of the embodiment shown in FIG. 8 in a plan view from above;

[0130] FIG. 10 shows the embodiment shown in FIG. 8 in a plan view from the front; and

[0131] FIG. 11 shows a side view of the outlet zone of a further embodiment of the thin-film treatment apparatus according to the invention with a horizontally extending discharge system.

[0132] The thin-film treatment apparatus 10 shown in FIG. 1 has a process housing 12 with a housing casing 14 which encloses a circular cylindrical housing interior 16 extending in the axial direction. This housing interior forms the material treatment space 160.

[0133] In a proximal end region of the process housing 12 there is arranged an inlet nozzle 20 for introducing the material that is to be treated into the material treatment space 160, whereas an outlet nozzle 24 for discharging the material from the material treatment space 160 is arranged in a distal end region of the process housing 12. The proximal end region thus corresponds to the inlet zone 18 of the process housing, whereas the distal end region corresponds to the outlet zone 22. A process zone 25 lies between the inlet zone and the outlet zone.

[0134] The process housing 12 is supported via appropriate support bearings in the proximal and in the distal end region, specifically via a fixed bearing 26 in the proximal end region and a floating bearing 28 in the distal end region.

[0135] The inlet nozzle 20 is arranged tangentially to the housing casing 14 in the shown embodiment and leads in the lower half into the material treatment space 160, as can be seen in particular from FIG. 3.

[0136] The outlet nozzle 24 is configured in the shown embodiment in the form of an opening which leads at the lowermost point of the housing casing 14 into a discharge system 30 arranged immediately therebelow, in this specific case into a twin discharge screw 300 with conveying direction running at a right angle to the axis direction of the process housing 12.

[0137] The housing casing 14 is double-walled in the shown embodiment, has a housing casing inner wall and a housing casing outer wall with an intermediate gap, in which there is arranged a conducting spiral for conducting a heat exchange medium, typically steam or hot water. In the specific case shown two heat transfer circuits are provided: a first heat transfer circuit with a first heat transfer medium inlet 32 in the inlet zone or in the inlet-side region of the process zone 25 and a first heat transfer medium outlet 34 in the outlet-side region of the process zone 25, and a second heat transfer circuit with a second heat transfer medium inlet 36 in a distal region of the outlet zone 22 and a second heat transfer medium outlet 38 in the proximal region thereof. The two heat transfer circuits have conducting spirals separate from one another and are thus temperature-controllable independently of one another. To this end a separate heating element and cooling element (not shown) for controlling the temperature of the heat transfer medium are assigned to each heat transfer circuit, the heat transfer medium is introduced from there via a heat transfer pump via the heat transfer medium inlet 32 or 36 into the corresponding conducting spiral. For instance it is conceivable that steam is used as heat transfer medium in the first heat transfer circuit associated with the process zone 25 and that hot water is used as heat transfer medium in the second heat transfer circuit associated with the outlet zone 22.

[0138] In addition, an upwardly running vapour nozzle 40 is arranged in the housing casing 14, via which vapour nozzle the low-boiling constituents may be removed from the material treatment space 160.

[0139] The apparatus additionally has a rotor 42, which comprises a drivable rotor shaft 44, arranged in the housing interior 16 and extending coaxially, for generating a material film on the inner surface 46 of the housing casing, as shown for example in FIG. 4.

[0140] The rotor 42 for this purpose has a drive 48, which preferably is speed-variable. In the specific case shown a spur gear motor 480 is provided, which acts on a driveshaft portion of the rotor shaft 44 in order to set the rotor shaft in rotation. The driveshaft portion is sealed here with respect to the material treatment space 160 by way of a mechanical seal.

[0141] The material film is produced on the inner surface 15 of the housing casing and the material is conveyed in the direction of the outlet nozzle via sweeper elements 43, which are divided into distribution elements 431 and into conveying elements 432 depending on their primary function, as also described further below.

[0142] A rotor shaft for an apparatus according to the invention is shown in FIG. 5. This has a rotor shaft body 50, which comprises a spindle 52 and six axially running fastening strips 54 welded onto the spindle and distributed over the circumference thereof. Lift elements 56 are flange-mounted onto these fastening strips 54, which lift elements in the specific case shown are provided in the form of pitched-roof-shaped web plates 560, the ridge 58 of which runs at least approximately parallel to the axis direction of the rotor shaft 44.

[0143] Due to the angled form, the web plate 560 is thus divided into a first and second web plate surface 60a, and 60b, which lie in planes running obliquely relative to one another. The leading first web plate surface 60a in the rotation direction forms the incident-flow portion 62 of the lift element 56. The leading end 64 of the incident-flow portion 62 in the rotation direction is arranged at a greater distance from the inner surface 15 of the housing casing than a region 66 of the incident-flow portion 62 trailing behind the leading end. A gap 68 that continuously narrows in a direction counter to the rotation direction is thus formed between the incident-flow portion 62 and the inner surface 15 of the housing casing. As the rotor shaft rotates, the highly viscous material that is to be processed is now pressed into the gap 68, whereby the flow force of the rotor shaft 44 acting on the incident-flow portion 62 imparts a hydrodynamic lift component perpendicularly to the incident-flow direction and thus counteracts a deflection of the rotor shaft 44.

[0144] In the case shown specifically in FIG. 7 the first web plate surface 60a or the incident-flow portion 62 encloses an angle α with the tangent or the tangential plane of the inner surface 15 of the housing casing and covers an angular range β.sub.1 of the circumference of the rotor shaft body 50. The trailing web plate surface covers an angular range β.sub.2. On the whole, the lift element thus covers an angle β.

[0145] Helically running conveying fins 70 are arranged on the radial outer side of the web plates 560 and are oriented in an angled manner in relation to the axis direction of the rotor shaft 44.

[0146] The gable 58 of the web plate 560 forms an axially running shearing edge 72, which is set back in relation to the radial outer edge of the conveying fin 70 and thus, in comparison thereto, is arranged at a greater distance from the inner surface 15 of the housing casing.

[0147] On the one hand a hydrodynamic lift component in the direction of the central rotor shaft body 50 is thus imparted to the rotor shaft 44 by the web plates 560 arranged on the rotor shaft 44. On the other hand the material is distributed over the inner surface 15 of the housing casing by the axially running shearing edge 72, wherein the material is additionally imparted a conveying component in the direction of the outlet nozzle by the conveying fins 70. Consequently, the web plates 560 functioning as lift elements 56 also constitute sweeper elements for distributing and conveying the material and thus constitute conveying-and-distribution elements.

[0148] As can be seen from FIG. 5, the rotor geometry or the sweeper elements 43 arranged on the rotor shaft body are configured differently depending on the zone. Thus, only pitched-roof-shaped web plates 560 are arranged in the inlet zone corresponding to the proximal end region. Specifically, six web plates are distributed over the circumference of the rotor shaft 44, wherein each two web plates arranged successively in the circumferential direction are connected to one another by connection plates 74 in such a way that a protective casing 76 is formed on the whole.

[0149] Due to the formation of a protective casing 76, the material to be treated and the gaseous material components escaping during the treatment are guided in the inlet zone 18 in parallel flow, whereby the risk of a possible “material entrainment” by the escaping components is minimised.

[0150] Web plates 560 are also arranged in the process zone 25 adjacent to the inlet zone 18, however the web plates are arranged on the rotor shaft body 50 offset from one another helically in the longitudinal portion of the rotor shaft 44 corresponding to the process zone, whereby an optimal distribution of the lift or the lift force generated by the individual lift elements over the entire process zone 25 can be obtained.

[0151] In order to attain a sufficiently high conveying effect, further sweeper elements 43 with increased conveying effect are also provided in addition to the web plates 560 functioning as lift element and conveying-and-distribution element. Specifically, sweeper elements 43 which comprise teeth 78, the shearing edge of which have an angle of attack in relation to the axis direction of greater than 5° and thus constitute a conveying element 432, but not a lift element, are also arranged in the process zone 25. Specifically, sweeper blades 80 each having a plurality of teeth 78 and having said angle of attack are provided. Furthermore, sweeper elements 43 with teeth 79 of which the shearing edge runs parallel to the axis direction and thus are neutral in respect of conveyance are provided; these sweeper elements thus constitute purely distribution elements 431. Distribution elements 431 and conveying elements 432 are arranged in alternation in the process zone 25 in the shown embodiment, wherein, as mentioned, a web plate 560 is fixed to one of the six fastening strips 54 or in one of the six rows of blades.

[0152] A configuration of the rotor shaft 44 that is particularly preferred for the inlet zone 18 is also shown in FIGS. 6 and 7. Accordingly, a coaxial sleeve 77 is provided, which has web plates 560 protruding radially from it and functions as a protective casing 76. A radially set-back channel 82 is formed on the outer side of the sleeve 77 between each two web plates 560 arranged in succession in the circumferential direction. In accordance with this embodiment the vapours created during the processing of the material may be guided through the channels 82. Once they have reached the end of the protective casing 76, the vapours pass through the interior 84 surrounded by the protective casing 76 or the sleeve 77 to a vapour space separated from the material treatment space 160, generally via a labyrinth seal, where the vapours may be removed via a vapour nozzle 40.

[0153] Alternatively to the discharge system shown in FIGS. 1 to 4 in the form of a twin discharge screw with conveying direction running horizontally and at right angles to the orientation of the process housing, the thin-film treatment apparatus according to the invention can alternatively comprise a discharge system 30 with vertical conveying direction, as is shown in FIGS. 8 to 10.

[0154] According to this alternative embodiment, the discharge system 30 comprises a funnel 86 with a discharge shaft 88 arranged therein and extending coaxially. The funnel has an approximately conical funnel portion 90, which tapers in the conveying direction, and adjoined thereto a cylindrical funnel portion 92. In its inlet-side (wide) region, the tapering funnel portion 90 has a funnel opening 94, by means of which the funnel 86 is connected to the housing interior 16 of the process housing 12. On the outlet side, the funnel 86 or the cylindrical funnel portion 92 is connected to a discharge pump 96, by means of which the material to be discharged can be removed or fed to further devices, such as a filter and/or a spinning nozzle.

[0155] The discharge shaft 88 has a first discharge shaft portion 98, on which there are arranged conveying elements 432′, by means of which the material to be discharged is conveyed in direction of the cylindrical funnel portion 92. This cylindrical funnel portion 92 serves as a bearing bush for a second discharge shaft portion 99 arranged therein with a single discharge screw 100 formed thereon for conveying the material towards the discharge pump 96.

[0156] As can be seen in particular from FIGS. 9 and 10, the rotor shaft 44 is mounted distally in a rotary bearing, which is arranged on the distal end face of the process housing 12. The funnel 86 is arranged in an offset manner based on the axial direction of the rotor shaft 44 or the process housing 12, in such a way that sufficient space is provided for the discharge shaft 88 extending upwardly next to the distal rotary bearing 102, which discharge shaft is connected at its upper end to a discharge shaft drive 104. Due to the offset arrangement of the funnel or in order to ensure in this arrangement an optimal opening cross-section of the funnel opening, the funnel 86 deviates in its upper inlet-side region from the conical form, as is shown in particular in FIGS. 8 and 9.

[0157] In its distal end region, two circumferential reamers 106 are arranged on the rotor shaft body 50, by means of which reamers the material is conveyed into the funnel opening 94 present on the underside of the process housing 12. Specifically, the reamers 106 each have a reamer bar 112, which is secured by means of a reamer arm 114 to the shaft 52 of the rotor shaft body 50 and by means of which the material to be discharged is shifted towards the funnel opening 94.

[0158] A plate-like cleaning element 110 is also arranged on the rotor shaft body 50 directly adjacently to the distal end face 108 of the process housing 12, which cleaning element prevents material from depositing on the inner face of the distal end face 108 and which furthermore also protects the distal rotary bearing 102 from being soiled by the material.

[0159] As shown in FIGS. 8 and 9, three outlet zone portions 22a, 22b, 22c are present in the outlet zone 22 of the shown embodiment. In the first outlet zone portion 22a, sweeper elements 43 are arranged on the corresponding longitudinal portion of the rotor shaft body 50 and comprise teeth, the shearing edges of which are angled by approximately 45° in relation to the axis direction and which thus act as conveying elements 432. Distribution elements 432, specifically sweeper elements with teeth of which the shearing edge runs parallel to the axis direction of the process housing 12 or the rotor shaft 44, are arranged in alternation with the conveying elements 432 in the first outlet zone portion 22a. Alternatively, it is also conceivable that only conveying elements 432 are present, whereby an increased conveying effect is produced in the first outlet zone portion 22a.

[0160] In the second outlet zone portion 22b adjoining the first outlet zone portion 22a in the conveying direction, the conveying elements 432 alternate in the circumferential direction with web plates 560, as have been described in conjunction with FIG. 5 and which function as lift element and as conveying-and-distribution element.

[0161] In the third outlet zone portion 22c adjoined thereto in the conveying direction, which third outlet zone leads into the funnel 86, there are in turn arranged merely the above-described reamers 106 on the rotor shaft body. In contrast to the distribution elements 431, which are neutral to the conveying process, present in the first outlet zone portion, further elements are thus provided in the second outlet zone portion additionally to the conveying elements 432 and impart a conveying component on the material, whereby an admissible conveyance to the third outlet zone portion 22c or the reamers 106 is then ensured even if the material has a very high viscosity. Whereas the conveying fins discussed in conjunction with FIG. 5 enclose in the process zone only a relatively small angle of, for example, 5° with the axis, this angle is larger for the conveying fins of the web plates 560 arranged in the outlet zone and can be, in particular 45°, whereby a stronger conveying effect as compared to the process zone is obtained.

[0162] The embodiment shown in FIGS. 8 to 10 has the advantage that the rotational speed of the rotor shaft 44 present in the process housing can be decoupled from that of the discharge shaft 88.

[0163] Alternatively to the embodiment shown in FIGS. 8 to 10, the discharge system is oriented horizontally in the embodiment shown in FIG. 11. Specifically, the discharge system 30 has a funnel 86′ flange-mounted on the process housing, and the rotor shaft 44 protrudes into said funnel. The funnel 86′ has a conically tapering funnel portion 90′, which is connected at its wide, proximal end by means of a flange connection to the process housing 12, and the axis of which coincides with the axis of the process housing; in the funnel portion 90′, the diameter of the rotor shaft 44 tapers accordingly. This conical funnel portion 90′ is adjoined in the conveying direction by a cylindrical funnel portion 92′, which serves as a bearing bush for the single discharge screw 100′ arranged therein.

[0164] As described in conjunction with the embodiment shown in FIGS. 8 to 10, the outlet zone of the embodiment shown in FIG. 11 also has a first outlet zone portion 22a′ and a second outlet zone portion 22b′ adjoining the first outlet zone portion. In this embodiment too, web plates 560 are formed in the second outlet zone portion 22b′ instead of the distribution elements 431, neutral to the conveying process, present in the first outlet zone portion 22a′ and said web plates function both as lift elements and as conveying-and-distribution elements. Also in the region of the rotor shaft 44 protruding into the funnel 86′—as in the second outlet zone portion 22b′—web plates 560 are also arranged on the rotor shaft body 50 together with the conveying elements 432. Specifically, the web plates 560 are arranged here helically offset in relation to one another.

[0165] A thin-film treatment apparatus with an inner diameter of the housing interior of 280 mm, and a circumference of 0.88 m, was used in an experiment for producing a solution of cellulose in NMMNO/water. The horizontal rotor shaft was equipped with different sweeper elements, which were arranged in a maximum of 8 horizontal rows around the rotor shaft, wherein in the process zone each second row of sweeper elements was inclined by an angle of α=20°; the rest of the rotor blades were not inclined. The spacing between the outer ends of the sweeper elements from one another was between 108 and 216 mm. The sweeper elements had an area of intervention in the horizontally moved suspension of at most 1.9 dm.sup.2, arranged facing the heated casing inner surface and distanced from the casing inner surface of the process housing between 2.75 and 3.5 mm. The horizontally supported rotor was operated at a maximum speed of 650 min.sup.−1, and therefore the circumferential speed of the tips of the sweeper elements was at most 9.3 m/s and the maximum frequency of succession of the sweeper elements was 2600 per minute. Further parameters are specified in Table 1.

[0166] In order to produce the cellulose solution, the used cellulose of the eucalyptus pulp type was suspended in desalinated water. Following complete suspension of the cellulose fibres in the water, the excess water was separated by filtration and the obtained pulp cake was pressed to a solids concentration of approximately 50% cellulose. Following the dewatering, the pulp cake was guided to the defibration via a needle roll and shredder. The resultant, finely defibred moist cellulose was introduced continuously into an aqueous tertiary amine oxide solution (NMMNO) in order to produce the suspension. Ring layer mixers and/or turbulent mixers are apparatuses suitable for this purpose.

[0167] The suspension of water, cellulose and NMMNO with different composition (see Table 1, rows b, c, d) was introduced into the thin-film treatment apparatus in a further stage of the process in order to produce the cellulose solution. It has proven to be advantageous if the introduced suspension has a mass-based water content of from 19% to 26%, cellulose content of from 5.7% to 11.9%, and NMMNO content of 65%-75%. A good distribution of the suspension in the feed zone may be achieved with such suspensions. It was found that the conversion from the starting composition (index in the formula=before) into the target composition (index in the formulas=after) advantageously follows a certain ratio. This ratio has proven to be suitable when the formula

[00001]$\frac{c_{H2O,\mathrm{before}}}{C_{H2O,\mathrm{after}}}=\frac{41.1+1.91c_{\mathrm{Cell},\mathrm{before}}}{47.9-1.43c_{\mathrm{Cell},\mathrm{after}}}$

is satisfied, wherein the difference to 100% in each case is formed by the NMMNO concentrations. All concentrations (c.sub.H2O, c.sub.Cell) are specified in mass %. Astonishingly, the best results were provided when the ratio of

[00002]$\frac{c_{H2O,\mathrm{before}}}{C_{H2O,\mathrm{after}}}$

was in the range of from 1.8 to 2.5 and the ratio

[00003]$\frac{c_{\mathrm{Cell},\mathrm{before}}}{c_{\mathrm{Cell},\mathrm{after}}}$

was 0.8-0.95.

[0168] By passing the suspension through the different treatment zones, its composition changes to the target composition. If the target composition is achieved, it does not change further during the course of the present method. This target composition preferably satisfies the formula c(Cell)≤35.9−1.736*c(H.sub.2O), and/or the formula c(Cell)≥32.4−2.17*c(H.sub.2O), wherein the c(Cell) is the content in mass % of the cellulose and c(H.sub.2O) is the content in mass % of the water in the cellulose solution. The starting composition is achieved by mixing the individual components, whereas the target composition is achieved as the present method is carried out. Since the composition forms differently in the individual zones as a result of the physical conditions present, it is advantageous if the parameters and ranges described in the method according to the invention are observed. According to experience the target composition that is sought follows the equation c(H2O)=(33.5−c(Cell)/1.91. The target composition may vary from the target composition that is sought, but should preferably lie in the ranges of the above-specified formulas for the target composition. The target composition is determined at the end of the outlet zone. During the treatment the target composition may be reached at different rates. It is thus advantageous for the present method if this target composition is reached at the end of the process zone. However, it is also quite conceivable that the target composition will be achieved already after a third of the total treatment time. The total treatment time is the period of time that is required by the suspension/solution to pass from the start of the inlet zone to the end of the outlet zone. Once the target composition has been reached, the composition of the cellulose solution does not change further.

[0169] In this horizontally configured thin-film evaporator the cellulose solution could be produced continuously in a particle-free manner by intense mixing and kneading action. Treatment times (t) of 150 seconds led to the complete dissolution of the cellulose.

[0170] The geometric conditions of the inner surface of the housing casing based on the area of the rotor blade tip (as above) and on the circumferential speed of the rotor blade tip (i.e. at the greatest distance from the axis) provided an effective characteristic value for assessing an economically expedient and simultaneously efficient dissolution of the introduced suspension. An economical method with, at the same time, very good solution quality may be performed with the following values of this parameter. This parameter is defined here as a specific area ratio of the rotor blades (table, row ae):

Spec. area ratio of the rotor blades (table,row ae)=heat exchange area of the inner wall of the housing casing (table,row h)/(rotor blade tip loading area (table,row ad)*blade tip speed (table,row l)

[0171] It has been found that for a good quality, i.e. score <2 of the ready-to-spin solution (table, row x), the spec. area ratio of the rotor blades is preferably less than 10, particularly preferably less than 8, and very particularly preferably less than 5 m.sup.2s/m.sup.3. These parameter ranges are thus particularly preferred.

[0172] For reliable process management, yet further stabilisers were added to the suspension in order to stabilise the solvent and prevent the cellulose degradation. The continuously produced suspension was converted under application of temperature (u, v, w) and negative pressure (j), and under horizontal shear into a highly viscoelastic solution, wherein excess water was removed at reduced pressure (j) between 45 and 90 mbar. The heating of the device was performed by means of saturated steam at a pressure of 1-2 bar, wherein the steam temperature was between 100° C. and 121° C.

[0173] The thickness of the layer spread over the interior was between 2.75 and 3.5 mm (i). Water evaporated by temperature and negative pressure was removed in counter flow to the suspension flow at a temperature of 80-85° C., wherein the steam flow (s) was up to 61.5 kg/h. The shear rate (o) was between 5000 and 21000 s.sup.−1, wherein the rotor at the speed € consumed an electrical power (f) of −0-37 kW.

[0174] At the outlet the finished cellulose solution was discharged (k) using a discharge screw. The discharge screw was used for the transfer from the negative pressure prevailing in the interior to the ambient pressure. Per hour, up to 484 kg of homogeneous cellulose solution could be obtained with a temperature (w) of approximately 100° C. The treatment time (t) of the suspension in the horizontal device was −0-360 seconds.

[0175] The highly viscous cellulose solution thus obtained was subjected to the additional process steps of devolatilisation and filtration prior to the spinning. As a result of the microscopic examination of the solution, it was determined that only in Examples 5 and 6 were undissolved cellulose particles present in the solution. To this end the scoring of the ready-to-spin solution (x) followed the following system: The scoring was done under a microscope with scores from 1 to 3. Score 1 means that undissolved particles are no longer present. Score 2 means that a few undissolved particles are present, and score 3 means that a lot of undissolved particles are present. Following filtration all cellulose solutions are suitable for spinning.

[0176] The cellulose solution was spun into filaments as described in WO 2013/030399 A and comprises extrusion of the solution through one or more extrusion openings under pressure and solidification of the shaped cellulose bodies in a collection bath, wherein the solution is guided through an air gap between the extrusion openings and the collection bath.

Characteristic Values:

Reynolds Number Rotor (y):

[0177] [00004]${\mathrm{Re}}_{\mathrm{rot}}=\frac{\rho .v.d_{\mathrm{rot}}}{\eta }$

Re.sub.rot=Reynolds number of the rotor [−]
ρ=mean density of the suspension [kg/m.sup.3]
v=circumferential speed of the rotor blade tips [m/s]
d.sub.rot=diameter of the rotor [m]
η=dynamic viscosity of the ready-to-spin solution [Pas]

Reynolds Number Film (z):

[0178] [00005]${\mathrm{Re}}_{\mathrm{film}}=\frac{\stackrel{.}{m}}{D_i.\pi .\eta }$

Re.sub.film=Reynolds number of the thin-layer film [−]
{dot over (m)}=mass flow of the fed suspension [kg/s]
D.sub.i=diameter of the heated cylinder [m]

Newton Number (aa):

[0179] [00006]$\mathrm{Ne}=\frac{P}{\rho .n^3.d_{\mathrm{rot}}^4.l}$

Ne=Newton number [−]
n=speed of the rotor [1/s]
l=length of the rotor [m]
P=power consumption of the rotor

Euler's Number (ab):

[0180]
Eu=1.372.Math.Re.sub.rot.sup.−0.15.Math.Re.sub.film.sup.0.379.Math.i.sup.−0.445

Eu=Euler's number
i=number of rotor blades

Pressure Calculation in the Reactor

[0181]
p=122.Math.e.sup.−0.05c(Cell)

p=absolute pressure in the reactor in mbar.
c(Cell)=cellulose concentration in the suspension in mass %
Spec. Area Ratio of the Rotor Blades (Sweeper Elements):

[00007]$A_R=\frac{A_M}{A_B*v_u}$

A.sub.R . . . specific area ratio of the rotor blades in m.sup.2s/m.sup.3
A.sub.M . . . casing inner surface of the process zone in m.sup.2
A.sub.B . . . rotor blade tip loading area in m.sup.2
V.sub.u . . . blade tip circumferential speed in m/s

TABLE-US-00002 TABLE 1 Example number Unit Letter 1 2 3 4 5 6 7 8 9 10 11 12 Suspension [kg/h] a 100 100 100 100 300 300 300 300 500 500 500 500 feed rate Conc. NMMNO [mass %] b 75.3 69.7 64.7 58 75.3 69.7 64.7 58 75.3 69.7 64.7 58 Conc. H2O [mass %] c 19 21.3 23.4 26.1 19 21.3 23.4 26.1 19 21.3 23.4 26.1 Conc. Cell [mass %] d 5.7 9 11.9 15.9 5.7 9 11.9 15.9 5.7 9 11.9 15.9 Rotational speed [1/min] e 118 177 236 236 355 414 473 473 532 532 591 650 Power [kW] f 7.4 9.25 11.1 18.5 14.8 14.8 18.5 22.2 14.8 14.8 22.2 33.3 consumption Inner diameter [mm] 9 280 280 280 280 280 280 280 280 280 280 280 280 of the housing interior Heat exchange [m.sup.2] h 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 0.55 area of the inner wall Film thickness of [mm] i 2.75 2.75 2.75 2.75 2.75 2.75 2.75 2.75 3.5 3.5 3.5 3.5 the suspension Pressure [mbar] j 90 75 60 45 90 75 60 45 90 75 60 45 during the reaction Solution [kg/h] k 95 90 85 80 289 280 271 259 484 469 456 439 discharge Blade tip [m/s] I 1.70 2.55 3.40 3.40 5.10 5.95 6.79 6.79 7.60 7.60 8.45 9.29 speed Blade tip [mm] m 108 108 108 108 216 216 216 216 214 214 214 214 spacing Blade [1/min] n 945 1418 1891 1891 1418 1655 1891 1891 2127 2127 2364 2600 succession frequency Shear rate [1/s] o 4941 7412 9883 9883 14824 17295 19766 19766 17376 17376 19307 21237 in the process zone Feed amount [kg/h] P 1.61 1.61 1.61 1.61 7.89 7.89 7.89 7.89 13.16 13.16 13.16 13.16 suspension/ sweeper element Heat exchange [dm.sup.2/ q 0.880 0.880 0.880 0.880 1.435 1.435 1.435 1.435 1.435 1.435 1.435 1.435 area/sweeper blade] element kg/h per m.sup.2 [kg/hm.sup.2] r 4987 4987 4987 4987 23939 23939 23939 23939 39898 39898 39898 39898 cross- sectional area Steam flow [kg/h] s 5.3 10.2 14.7 20.5 10.7 20.5 29.3 41 16 30.7 44 61.5 Treatment [s] t 225 427 650 912 53 100 153 279 188 231 275 325 time Temp. inlet [° C.] u 80 80 80 80 80 80 80 80 80 80 80 80 zone Temp. process [° C.] v 100 103 103 110 100 103 103 110 100 103 103 110 zone Temp. outlet [° C.] w 95 99 100 105 98 101 101 106 99 102 102 107 zone Score of the [−] x 1 1 1 1 2 2 1 2 1-2 2 2-3 2 ready-to-spin solution Reynolds [−] y 0.11 0.10 0.07 0.04 0.34 0.24 0.15 0.07 0.50 0.31 0.18 0.10 number of the rotor Reynolds [−] z 6.32 E−06 3.95 E−06 2.11 E−06 1.05 E−06 1.89 E−05 1.18 E−05 6.32 E−06 3.16 E−06 3.16 E−05 1.97 E−05 1.05 E−05 5.26 E−06 number of the film Newton number [−] aa 229 85 43 72 17 11 9 11 5 5 6 6 Euler's number [−] from 2.60 E−03 2.75 E−03 2.28 E−03 1.94 E−03 4.18 E−03 4.56 E−03 3.87 E−03 3.30 E−03 5.94 E−03 5.34 E−03 4.55 E−03 3.83 E−03 Discharge at the [kg/h/ ac 173.6 164.7 156.4 145.8 530.5 512.5 496.4 474.9 887.5 860.5 836.1 804.0 outlet per m.sup.2 m.sup.2] of heat exchange area Rotor blade tip [m.sup.2] to 0.02005 0.02005 0.02005 0.02005 0.01253 0.01253 0.01253 0.01253 0.01253 0.01253 0.01253 0.01253 loading area Spec. area ratio [m.sup.2s/m.sup.3] ae 16.0129 10.6752 8.00646 8.00646 8.54023 7.32019 6.40517 6.40517 5.72477 5.72477 5.15229 4.68390 of the rotor blades Engaging-tip kg/sm.sup.2 af 1.31 1.24 1.18 1.10 6.41 6.20 6.00 5.74 10.73 10.40 10.11 9.72 power

LIST OF REFERENCE SIGNS

[0182] 10 thin-film treatment apparatus [0183] 12 process housing [0184] 14 housing casing [0185] 15 inner surface of the housing casing [0186] 16; 160 housing interior; material treatment space [0187] 18 inlet zone [0188] 20 inlet nozzle [0189] 22 outlet zone [0190] 24 outlet nozzle [0191] 25 process zone [0192] 26 fixed bearing [0193] 28 floating bearing [0194] 30; 300 discharge system; twin discharge screw [0195] 32 first heat transfer medium inlet [0196] 34 first heat transfer medium outlet [0197] 36 second heat transfer medium inlet [0198] 38 second heat transfer medium outlet [0199] 40 vapour nozzle [0200] 42 rotor [0201] 43 sweeper elements [0202] 431, 432 distribution elements, conveying elements [0203] 44 rotor shaft [0204] 48; 480 drive; spur gear motor [0205] 50 rotor shaft body [0206] 52 spindle [0207] 54 fastening strips [0208] 56; 560 lift element; web plate [0209] 58 ridge of the web plate [0210] 60a, b first and second web plate surface [0211] 62 incident-flow portion [0212] 64 leading end of the incident-flow portion [0213] 66 trailing region of the incident-flow portion [0214] 68 gap [0215] 70 conveying fin [0216] 72 axially extending shearing edge of the web plate [0217] 74 connection plates [0218] 76 protective casing [0219] 77 sleeve [0220] 78 teeth with angle of attack [0221] 79 teeth without angle of attack [0222] 80 sweeper blade [0223] 82 channel [0224] 84 interior of the protective casing [0225] 86, 86′ funnel [0226] 88 discharge shaft [0227] 90, 90′ tapering funnel portion [0228] 92 cylindrical funnel portion [0229] 94 funnel opening [0230] 96 discharge pump [0231] 98 first discharge shaft portion [0232] 99 second discharge shaft portion [0233] 100 single discharge screw [0234] 102 distal rotary bearing [0235] 104 discharge shaft drive [0236] 106 reamer [0237] 108 distal end face of the process housing [0238] 110 cleaning element [0239] 112 reamer bar [0240] 114 reamer arm

PREFERRED EMBODIMENTS

[0241] The invention is preferably defined as follows:

[0242] 1. A thin-film treatment apparatus for treating viscous material comprising

a process housing (12) oriented at an incline to the horizontal of at most 20° with a heatable and/or coolable housing casing (14), which surrounds a rotationally symmetrical housing interior (16) extending in the axial direction and forming a material treatment space (160),
an inlet nozzle (20) arranged in an inlet zone (18) of the process housing (12) in order to introduce the material to be treated into the material treatment space (160),
an outlet nozzle (24) arranged in an outlet zone (22) of the process housing (12) in order to discharge the treated material from the material treatment space (160), and
a drivable rotor shaft (44) arranged in the material treatment space (160) and extending coaxially for producing a material film on the inner surface (15) of the housing casing and for conveying the material in a direction from the inlet zone (18) via a process zone (25) to an outlet zone (22), wherein the rotor shaft (44) comprises a central rotor shaft body (50) and, arranged on the circumference thereof, sweeper elements (43), of which the radially outermost end is distanced from the inner surface (15) of the housing casing,
characterised in that the rotor shaft (44) comprises at least one lift element (56) arranged on the rotor shaft body (50), which lift element is designed in such a way as to produce a lifting force in the direction of the rotor shaft body (50) during the rotation of the rotor shaft (44).

[0243] 2. The thin-film treatment apparatus according to 1, characterised in that the lift element (56) comprises a planar incident-flow portion (62) with a leading end (64) in the rotation direction, which end is arranged at a greater distance from the inner surface (15) of the housing casing than a region (66) of the incident-flow portion (62) trailing behind the leading end, whereby a gap (68) that narrows in a direction opposite the rotation direction is formed between the incident-flow portion (62) and the inner surface (15) of the housing, in particular a continuously narrowing gap.

[0244] 3. The thin-film treatment apparatus according to 2, characterised in that the incident-flow portion (62) covers an angular range β.sub.1 of at least 10° of the circumference of the rotor shaft body (50).

[0245] 4. The thin-film treatment apparatus according to 1 to 3, characterised in that at least a part of the lift elements (56) is formed in each case by a sweeper element (43).

[0246] 5. The thin-film treatment apparatus according to 1 to 4, characterised in that the lift element (56) comprises an at least approximately pitched-roof-shaped web plate (560), the ridge (58) of which runs at least approximately parallel to the axis direction of the rotor shaft (44).

[0247] 6. The thin-film treatment apparatus according to 1 to 5, characterised in that the lift element (56), in particular the web plate (560), has at least one helically running conveying fin (70) on its radial outer side.

[0248] 7. The thin-film treatment apparatus according to 1 to 6, characterised in that at least a part of the lift elements (56) is arranged in a region which lies centrally between the rotary bearings on which the rotor shaft (44) is supported, preferably in the process zone (25).

[0249] 8. The thin-film treatment apparatus according to 1 to 7, characterised in that at least a part of the lift elements (56) are arranged in the process zone (25) on the rotor shaft body (50) helically offset in relation to one another.

[0250] 9. The thin-film treatment apparatus according to 1 to 8, characterised in that a concentric protective casing (76) arranged between the inner surface (15) of the housing casing and the rotor shaft body (50) and surrounding the rotor shaft body at least approximately completely is formed in the inlet zone (18).

[0251] 10. The thin-film treatment apparatus according to 9, characterised in that the protective casing (76) is formed at least in part by a plurality of lift elements (56) distributed in the circumferential direction, in particular web plates (560).

[0252] 11. The thin-film treatment apparatus according to 10, characterised in that a radially set-back channel (82) is formed between each two lift elements (56), in particular web plates (560), arranged in succession in the circumferential direction.

[0253] 12. The thin-film treatment apparatus according to 1 to 11, characterised in that the process zone (25) has a distribution zone and a conveying zone arranged downstream in the conveying direction, wherein the ratio of the number of conveying elements (432) to the number of distribution elements (431) is higher in the conveying zone than in the distribution zone.

[0254] 13. The thin-film treatment apparatus according to 1 to 12, characterised in that the outlet nozzle (24) leads into a discharge system (30) in the form of a single discharge screw or a twin discharge screw (300), preferably with axis direction transverse to the axis direction of the process housing (12).

[0255] 14. The thin-film treatment apparatus according to 1 to 13, characterised in that it additionally comprises a cleaning apparatus which is configured in such a way that it can be introduced into the process housing (12) and is movable to and fro in the axis direction when the end cover is opened.

[0256] 15. The thin-film treatment apparatus according to 1 to 14, characterised in that it is designed for thermal fractionation of a substance mixture, and in particular is provided in the form of a thin-film evaporator, a thin-film dryer or a thin-film reactor, preferably in the form of a thin-film evaporator.

[0257] 16. Use of a thin-film treatment apparatus according to 1 to 15 for the treatment of a material having a viscosity of 100 Pas or more at least temporarily during the treatment.

[0258] 17. A method for producing a solution of cellulose with a solvent from a suspension of cellulose in the solvent and a volatile non-solvent, comprising the introduction of the suspension into an inlet of a thin-film treatment apparatus, application and distribution of the suspension in a film-like form on a housing casing, temperature-controlled using a heat exchanger, by sweeper elements rotating about a common axis in a process housing of the thin-film treatment apparatus, evaporation of volatile non-solvent so that the cellulose is dissolved, and output of the solution of cellulose from the thin-film treatment apparatus through an outlet.

[0259] 18. The method according to 17, characterised in that at least a part of the sweeper elements cause the cellulose to be advanced in the direction of the outlet so that the discharge at the outlet is between 300 and 600 kg/h, preferably between 350 and 550 kg/h, and particularly preferably between 380 and 480 kg/h cellulose solution per m.sup.2 of the temperature-controlled surface of the housing casing.

[0260] 19. The method according to 17 or 18, characterised in that the temperature of the introduced suspension in the process zone is between 100 and 125° C., preferably between 100 and 110° C., and particularly preferably between 100 and 105° C.

[0261] 20. The method according to 17 to 19, characterised in that the absolute pressure in the process zone is at least in the range of +/−10%, preferably +/−5%, of the formula p=122*e{circumflex over ( )}−0.05c(Cell)), wherein p is the absolute pressure in mbar and c(Cell) is the cellulose concentration in the suspension in mass %.

[0262] 21. The method according to 17 to 20, characterised in that the specific area ratio of the rotor blades (table, ae) lies below 10 m.sup.2s/m.sup.3, particularly preferably below 8 m.sup.2s/m.sup.3, and very particularly preferably below 5 m.sup.2s/m.sup.3.

[0263] 22. The method according to 17 to 21, characterised in that the rotor blade tip loading area (table, ad) lies in a range of from 0.02 m.sup.2 to 6 m.sup.2, preferably in a range of 2 m.sup.2-6 m.sup.2 and particularly preferably in a range of 4 m.sup.2-6 m.sup.2.

[0264] 23. The method according to 17 to 22,

a) characterised in that the specific loading in the inlet zone is 80 kg/h/dm.sup.3-380 kg/h/dm.sup.3, preferably 120 kg/h/dm.sup.3-370 kg/h/dm.sup.3, and particularly preferably 150 kg/h/dm.sup.3-350 kg/h/dm.sup.3;
b) characterised in that the specific loading in the process zone is 65 kg/h/dm.sup.3-260 kg/h/dm.sup.3, preferably 70 kg/h/dm.sup.3-200 kg/h/dm.sup.3, and particularly preferably 80 kg/h/dm.sup.3-150 kg/h/dm.sup.3;
c) characterised in that the specific loading in the outlet zone is 2 kg/h/dm.sup.3-125 kg/h/dm.sup.3, preferably 5 kg/h/dm.sup.3-100 kg/h/dm.sup.3, and particularly preferably 10 kg/h/dm.sup.3-50 kg/h/dm.sup.3;
d) characterised in that the specific loading in the post-processing zone is 0 kg/h/dm.sup.3-500 kg/h/dm.sup.3, particularly preferably 0 kg/h/dm.sup.3-250 kg/h/dm.sup.3.

[0265] 24. The method according to 17-23, characterised in that the total treatment time of the cellulose solution is at least 60 s, preferably greater than 100 s, and particularly preferably from 100 to 1000 s.

[0266] 25. The method according to 17 to 24, characterised in that the ratio of starting composition to target composition follows formula

[00008]$\frac{c_{H2O,\mathrm{before}}}{C_{H2O,\mathrm{after}}}=\frac{41.1+1.91c_{\mathrm{Cell},\mathrm{before}}}{47.9-1.43c_{\mathrm{Cell},\mathrm{after}}},$

wherein c(Cell) is the concentration of the cellulose in the solution and c(H2O) is the concentration of water in the solution, specified in each case in mass %.
26. The method according to 17 to 25,
a) characterised in that the ratio of

[00009]$\frac{c_{H2O,\mathrm{before}}}{C_{H2O,\mathrm{after}}}$

lies in the range of from 1.8 to 2.5, particularly preferably in the range of 2.1-2.4;
b) characterised in that the ratio of

[00010]$\frac{c_{\mathrm{Cell},\mathrm{before}}}{c_{\mathrm{Cell},\mathrm{after}}}$

lies in the range of from 0.8 to 0.95, particularly preferably in the range of 0.8-0.88.
27. The method according to 17 to 26, characterised in that the tip efficiency lies in the range of from 1.1 kg/sm.sup.2-5.5 kg/sm.sup.2, preferably between 1.1 kg/sm.sup.2-2.8 kg/sm.sup.2, and particularly preferably between 1.1 kg/sm.sup.2 and 1.4 kg/sm.sup.2.

[0267] 28. The method according to 17 to 27, characterised in that the target composition is achieved preferably after at least ⅓ of the total treatment time, preferably after ⅔ of the total treatment time, particularly preferably at the end of the process zone.

[0268] 29. The method according to 17 to 28, characterised in that the length of the housing casing, temperature-controlled using a heat exchanger, from the inlet to the outlet is 0.5 m or more, preferably 1 m to 20 m.

[0269] 30. The method according to 17 to 29, characterised in that the surface of the housing casing, temperature-controlled using a heat exchanger, is 0.5 m.sup.2 to 150 m.sup.2, preferably 60 m.sup.2 to 125 m.sup.2.

[0270] 31. The method according to 17 to 30, characterised in that the radially outermost end of the sweeper elements is moved at a speed of from 1.5 m/s to 12.5 m/s by the rotation of the sweeper elements.

[0271] 32. The method according to 17 to 31, characterised in that sweeper elements are moved at a frequency of from 1500 to 4000 per min in succession over a portion of the housing casing temperature-controlled using a heat exchanger.

[0272] 33. The method according to 17 to 32, characterised in that directly successive sweeper elements follow on from one another with a spacing of from 100 mm to 300 mm between the radially outermost ends of the sweeper elements.

[0273] 34. The method according to 17 to 33, characterised in that 1.5 kg/h to 20 kg/h suspension are introduced at the inlet per sweeper element.

[0274] 35. The method according to 17 to 34, characterised in that the suspension is applied with a film thickness of from 1 mm to 50 mm, preferably 2.0 mm to 15 mm.

[0275] 36. The method according to 17 to 35, characterised in that a sweeper element is in contact with the suspension or solution on average over an area of from 0.8 dm.sup.2 to 2 dm.sup.2.

[0276] 37. The method according to 17 to 36, characterised in that the suspension has a film thickness according to the formula s=(ln(m.sub.s/60))/x, wherein s is the film thickness in mm, m.sub.s is the conveyed flow of the suspension, and x is a constant from 0.45 to 7, preferably of 0.5866.

[0277] 38. The method according to 17 to 37, characterised in that 300 kg to 100000 kg, preferably 10000 kg to 50000 kg suspension are introduced per hour.

[0278] 39. The method according to 17 to 38, characterised in that the common axis of the rotating sweeper elements is inclined by at most 20° to the horizontal.

[0279] 40. The method according to 17 to 39 with a thin-film treatment apparatus according to any one of points 1 to 15.