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WO1996001140A1 - Evaporator operating according to the falling film principle - Google Patents

Evaporator operating according to the falling film principle Download PDF

Info

Publication number
WO1996001140A1
WO1996001140A1 PCT/FI1994/000309 FI9400309W WO9601140A1 WO 1996001140 A1 WO1996001140 A1 WO 1996001140A1 FI 9400309 W FI9400309 W FI 9400309W WO 9601140 A1 WO9601140 A1 WO 9601140A1
Authority
WO
WIPO (PCT)
Prior art keywords
evaporating
vapour
tubes
tube system
chamber
Prior art date
Application number
PCT/FI1994/000309
Other languages
French (fr)
Inventor
Matti Knuutila
Kalevi Nurminen
Jukka Vaistomaa
Anssi MÄKELÄ
Original Assignee
Kvaerner Pulping Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to FI931496A priority Critical patent/FI93427B/en
Priority claimed from FI931496A external-priority patent/FI93427B/en
Priority to CA002120297A priority patent/CA2120297C/en
Application filed by Kvaerner Pulping Oy filed Critical Kvaerner Pulping Oy
Priority to PCT/FI1994/000309 priority patent/WO1996001140A1/en
Priority to SK1653-96A priority patent/SK281918B6/en
Priority to BR9408600A priority patent/BR9408600A/en
Priority to AT0907394A priority patent/AT407119B/en
Priority to RU97101456A priority patent/RU2122456C1/en
Priority to ZA945084A priority patent/ZA945084B/en
Priority to FR9408976A priority patent/FR2722866B1/en
Publication of WO1996001140A1 publication Critical patent/WO1996001140A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D1/00—Evaporating
    • B01D1/06—Evaporators with vertical tubes
    • B01D1/065—Evaporators with vertical tubes by film evaporating
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/10—Concentrating spent liquor by evaporation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D3/00—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium flows in a continuous film, or trickles freely, over the conduits
    • F28D3/02—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium flows in a continuous film, or trickles freely, over the conduits with tubular conduits

Definitions

  • the invention relates to an evaporator operat ⁇ ing on falling film principle, comprising a shell and a system of evaporating tubes therein, the system comprising vertical evaporating tubes, elements for feeding an agent to be evaporated on the evaporating tubes in such a way that it flows down along the eva ⁇ porating tubes and forms a film on the outer surface thereof, and heating vapour inlet and outlet channels connected to the inner portion of the evaporating tubes.
  • Evaporators operating on falling film principle have been used generally for a long time already for the concentration of liquids.
  • a liquid is allowed to flow as a film generally along the inner surface of heating tubes and the outer sur ⁇ face of the tubes is heated by vapour, due to which the heat of the vapour causes water to evaporate from the liquid to be concentrated and to flow as vapour into a collecting chamber and further as vapour out of the collecting chamber.
  • the con ⁇ centrated liquid flows along the tubes downwards into a collecting chamber and out of there through a sepa- rate channel.
  • the vapour used for heating is at least partly condensed into water and discharged as a con ⁇ densate through a separate channel.
  • the remaining vapour again is exhausted separately through a parti ⁇ cular outlet channel for vapour.
  • the equipment is typically implemented in such a way that tubes forming a heat ⁇ ing surface are fastened at their ends between so- called tube plates.
  • the tube plates have holes for the tube ends and form partition walls between a feed chamber for a liquid to be concentrated, a vapour chamber and a collecting chamber for concentrated li ⁇ quid, respectively.
  • Such a solution is known from the Finnish Patent 71 067, for example.
  • the casing must, be made of a thick material and the whole structure of the evaporator must be very solid, which means higher manufacturing costs.
  • dirt collected on the inner surface of the tubes may come loose as pieces and block the tube so that the tubes cannot be cleaned successfully in a typical way with a wash liquid any more, the result of which is that the evaporating capacity of the equipment decreases.
  • manufacture of tube plates according to the known solutions demands great precision and the manufacturing costs therefor are high.
  • the object of the present invention is to pro ⁇ vide an evaporator by means of which the above draw- backs are avoided and which is simple to manufacture and also to clean, if necessary.
  • the evaporator ac ⁇ cording to the invention is characterized in that the evaporating tube system is formed of a plurality of parallel evaporating elements.
  • An essential idea of the invention is that evaporating elements are formed of evaporating tubes preferably in such a way that the upper ends of the evaporating tubes and the lower ends, respectively, are interconnected preferably by means of tubular collecting chambers.
  • the invention is further charac ⁇ terized in that a plurality of evaporating elements formed of parallel evaporating tubes preferably on the same level are installed in parallel in the same evaporator.
  • a preferred embodiment of the invention is further characterized in that the collecting cham ⁇ bers of the separate evaporating elements are inter ⁇ connected in such a way that the collecting chambers at the upper end of the tubes, on the one hand, and the collecting chambers at the lower end of the tubes, on the other hand, are interconnected prefer ⁇ ably by means of a tubular connecting chamber or pos ⁇ sibly a connecting chamber of some other shape.
  • An ⁇ other essential idea of the invention is that a li ⁇ quid to be concentrated is fed through a distributing basin at the upper end of the evaporating tubes on the outer surface thereof and vapour is fed through the collecting chambers inside the evaporating tubes preferably from the upper end downwards, and corre ⁇ spondingly, the condensate generated is discharged from the collecting chambers at the other end as well as the remaining vapour as vapour, both preferably through separate channels or through a common chan ⁇ nel. Vapour may be fed also from below, in which case the condensate is collected from below and the re- maining vapour from above.
  • An advantage of an evaporator according to the invention is that it is easy and simple to manufac ⁇ ture, because it is formed of a plurality of parallel evaporating elements manufactured in the same way. Since the elements can be supported only at one end, no thermal strains to be compensated for arise, even though the heating surface tubes and the shell were made of different materials. Further, the tube system of the evaporator according to the invention is not easily blocked, because only vapour and condensation water pass through the evaporating tubes. In addi ⁇ tion, the structure according to the invention can be made relatively light, because only those evaporating elements which contain vapour have a high pressure.
  • the wall thickness of the evaporating tubes of these elements can be selected in a desired manner without the thickness of the remaining part of the evapora ⁇ tor, e.g. of the shell, being affected thereby. More ⁇ over, the heating surfaces of the evaporator accord- ing to the invention are easy to clean, if needed, because possible dirt from liquor or some other li ⁇ quid, fastened to the heating surfaces, is situated on the outer surface of the evaporating tubes and the evaporator may thus be cleaned in a generally known manner by dissolving or for instance by means of a pressure washer or some other similar device without the tube system having to be rinsed inside.
  • Figure 2 shows the evaporator according to the invention in cross-section with respect to the evap- orating elements
  • Figures 3a and 3b show schematically a side and edge view of an evaporating element according to the invention
  • Figure 4 shows schematically a perspective sec- tion view of an embodiment of the evaporator accord ⁇ ing to the invention.
  • FIGs 1 and 2 illustrate schematically an evaporator according to the invention in section par ⁇ allel with evaporating elements, on the one hand, and in cross-section with respect to the evaporating ele ⁇ ments, on the other hand.
  • the evaporator comprises a shell 1 containing a system 2 of evaporating tubes formed of evaporating elements similar to those to be shown schematically in Figure 3 later.
  • a liquid to be concentrated, in this case black liquor, is fed through a connection 3 into the shell 1, to the bot ⁇ tom thereof.
  • Liquor is discharged from the bottom of the evaporator through an outlet connection 4 and part of it is pumped by means of a schematically shown pump 5 through a circulating tube 6 into a dis ⁇ tributing basin 7 above the evaporating tube system 2, from which basin it flows substantially evenly on collecting chambers 8 of the evaporating elements and from there further along the surface of separate evaporating tubes 9 downwards.
  • the use of the inven ⁇ tion is in no way restricted to black liquor, but it can also be used for the evaporation of other li ⁇ quids.
  • the concentrated black liquor flows along the surface of collecting chambers 10 of the lower end and falls subsequently into the liquor in the lower part of the shell 1 and mixes therewith.
  • vapour is led through the evaporating tubes 9 and it is fed in through an inlet channel 11 in the upper part of the evaporating tube system 2. From there the vapour enters firstly a connecting chamber 12, which is connected to the upper collecting chambers 8 of the evaporating elements, so that the vapour is dis ⁇ tributed through these evenly to all evaporating tubes 9.
  • the remaining part of the vapour and condensate are collected, after having passed through the evaporating tubes 9, in the col ⁇ lecting chambers 10 of the lower end of the evaporat ⁇ ing elements, these collecting chambers being con- nected to a lower connecting chamber 13.
  • FIGs 3a and 3b show schematically an evapo ⁇ rating element 2a of an evaporator according to the invention in side and edge view, respectively.
  • the evaporating element 2a comprises an upper collecting chamber 8, evaporating tubes 9 and a lower collecting chamber 10.
  • a single evaporating element 2a is, as shown in Figure 3b, preferably a flat planar evapo ⁇ rating element formed of parallel evaporating tubes at a distance from each other, with each tube 9 con ⁇ nected to the collecting chambers 8 and 10, respec ⁇ tively, so that there is a connection between the collecting chambers 8 and 10 through each evaporating tube.
  • the evaporating tubes 9 can be fastened to the collecting chambers 8 and 10 e.g.
  • the collecting chambers 8 and 10 are preferably tubular, which makes it possible to provide easily a structure as pressure resistant as possible. Since the evaporating elements 2a resist high pressure, high vapour temperatures, and consequently, high pressures can be used for the evaporation without the whole evaporator having to resist high pressure. Then the structure of the whole evaporator can be made relatively light, and to that part, the manufacturing costs lower than those of the known solutions. Correspondingly, no expensive accu ⁇ rately machined tube plates are required for the man ⁇ ufacture of the evaporating element 2a, but this ele ⁇ ment can be assembled easily of tubular parts.
  • the evaporator according to the invention is simple to construct and its evaporating elements 2a are easy to manufacture, while the number of evapo ⁇ rating elements 2a and the number of evaporating tubes in one element may be selected as per needed. Since vapour passes inside the evaporating tubes 9, these are not blocked under the influence of the so ⁇ lution to be concentrated, such as liquor. Further ⁇ more, the outer surfaces of the evaporating tubes 9 are easy to clean in a generally known manner by dis- solving or for example by means of a pressure washer or some other similar device, if necessary, because between the tubes there are in practice such slits that enable an access to all surfaces in this way.
  • Figure 4 shows schematically one embodiment of the evaporator according to the invention in perspec ⁇ tive section.
  • This figure is an illustrative presen ⁇ tation of how the evaporating tube system 2 is formed by positioning evaporating elements 2a in parallel so as to form a structure of square cross-section, for instance.
  • the evaporating tube system 2 is suspended in place with respect to the shell 1 of the evapora ⁇ tor by using the collecting chambers 8 at the upper end of the elements 2a to support the tube system on holders 20 fastened to the shell 1.
  • the length of the collecting chambers 8 is dimen ⁇ sioned so that both ends thereof extend outside the outermost evaporating tubes 9 of the evaporating ele ⁇ ments 2a and thus on the holders 20.
  • the upper, connecting chamber 12 is supported by one of the holders 20.
  • the lower con ⁇ necting chamber 13 is mounted at one end of the lower collecting chambers 10, while it was mounted in the middle part of the collecting chambers 10, below them, in the embodiment of Figure 1.
  • the location of the connecting chamber 13 may thus be selected in a desired manner, which is not of essential importance to the operation of the evaporator.
  • Identical refer ⁇ ence numerals are used in Figure 4 for identical parts in the previous figures, and as to those parts, they are not explained in more detail.
  • the invention has been set forth only by way of ex ⁇ amples and it is in no way restricted thereto.
  • the evaporating elements may be assembled in various man- ners according to the pressure to be used and dimen- sioned for each need separately. Except for being tubular, the collecting chambers 8 and 10 may also have another shape.
  • the connecting chambers 12 and 13 may be connected in various manners to the collecting chambers 8 and 10, respectively, either to the ends thereof or to the middle, depending on the situation. Further, the vapour may be fed and exhausted, except in the previously described manner to the upper end of the evaporating tube system through the connecting chamber 12 and from the lower end of the evaporating tube system through the connecting chamber 13, also in the opposite direction.
  • the vapour is fed into the connecting chamber 13 at the lower end of the tubes and it flows from below upwards through the tubes 9 into the upper collecting chamber and from there further into the upper connecting chamber 12, from where it is exhausted.
  • the vapour may be fed to the lower end of the elements and exhausted from the upper end thereof.
  • the simplest way of dis ⁇ charging the condensate is to discharge it from the lower end of the evaporating elements.
  • Liquor or some other liquid to be evaporated may be fed, as shown in the Figures 1 and 2, to the bottom of the evaporator, or alternatively, directly into the distributing ba ⁇ sin 7.
  • the liquor or other liquid to be evaporated may be discharged from the bottom of the shell 1 of the evaporator and circulated either in the manner shown in the figures or by taking the liquid to be circulated separately from the upper part of the li ⁇ quid layer in the bottom of the shell 1, for in ⁇ stance.
  • the evaporating elements may be supported, except by suspending from the upper part, also to stand on their lower part, in which case holders cor- responding to the holders 20, for example, are ar ⁇ ranged to be supported by the chamber and the ele ⁇ ments are positioned on such holders in order to stand on their collecting chambers, for instance.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Abstract

An evaporator operating on falling film principle, comprising a shell (1) and a system (2) of evaporating tubes therein, whereby a liquid to be concentrated is fed on the outer surface of the evaporating tube system (2) and vapour is led to flow inside the tubes of the evaporating tube system (2). In the invention, the evaporating tube system (2) is formed of evaporating elements, each evaporating element being formed of evaporating tubes (9) substantially on the same level. The upper ends of the tubes are connected to a common collecting chamber (8) and the lower end, respectively, to a common collecting chamber (10) in such a manner that there is a connection between both collecting chambers (8, 10) through each tube (9) between them, due to which the collecting chambers (8) of the upper end of the evaporating elements are interconnected through the upper connecting chamber (12), and respectively, the collecting chambers (10) of the lower end are interconnected through the connecting chamber (13) of the lower end.

Description

Evaporator operating according to the falling ilm principie
The invention relates to an evaporator operat¬ ing on falling film principle, comprising a shell and a system of evaporating tubes therein, the system comprising vertical evaporating tubes, elements for feeding an agent to be evaporated on the evaporating tubes in such a way that it flows down along the eva¬ porating tubes and forms a film on the outer surface thereof, and heating vapour inlet and outlet channels connected to the inner portion of the evaporating tubes.
Evaporators operating on falling film principle have been used generally for a long time already for the concentration of liquids. In these evaporators, a liquid is allowed to flow as a film generally along the inner surface of heating tubes and the outer sur¬ face of the tubes is heated by vapour, due to which the heat of the vapour causes water to evaporate from the liquid to be concentrated and to flow as vapour into a collecting chamber and further as vapour out of the collecting chamber. Correspondingly, the con¬ centrated liquid flows along the tubes downwards into a collecting chamber and out of there through a sepa- rate channel. The vapour used for heating is at least partly condensed into water and discharged as a con¬ densate through a separate channel. The remaining vapour again is exhausted separately through a parti¬ cular outlet channel for vapour. In known solutions, the equipment is typically implemented in such a way that tubes forming a heat¬ ing surface are fastened at their ends between so- called tube plates. The tube plates have holes for the tube ends and form partition walls between a feed chamber for a liquid to be concentrated, a vapour chamber and a collecting chamber for concentrated li¬ quid, respectively. Such a solution is known from the Finnish Patent 71 067, for example.
From the Finnish Patent 76 699 again is known a solution, in which the evaporating tubes are formed of two tubes within each other in such a manner that the upper end of the outer tube is closed and vapour is caused to pass along the surface between the tubes and to return through the inner tube. On the other hand, the liquid to be concentrated is fed outside the tubes. Also in this solution, a pressure resis¬ tant tube plate is required for the tubes, and be¬ cause of the tubes being within each other, dimen¬ sioning and installation shall be very accurate. When high dry contents are strived for, a pro¬ blem with the known solutions is that hot vapour must be utilized for providing a sufficient temperature, due to which the outer casing of the evaporator is exposed to a high vapour pressure. Because of this, the casing must, be made of a thick material and the whole structure of the evaporator must be very solid, which means higher manufacturing costs. Further, in a solution in which liquor is caused to pass through the tubes, dirt collected on the inner surface of the tubes may come loose as pieces and block the tube so that the tubes cannot be cleaned successfully in a typical way with a wash liquid any more, the result of which is that the evaporating capacity of the equipment decreases. Moreover, the manufacture of tube plates according to the known solutions demands great precision and the manufacturing costs therefor are high.
The object of the present invention is to pro¬ vide an evaporator by means of which the above draw- backs are avoided and which is simple to manufacture and also to clean, if necessary. The evaporator ac¬ cording to the invention is characterized in that the evaporating tube system is formed of a plurality of parallel evaporating elements. An essential idea of the invention is that evaporating elements are formed of evaporating tubes preferably in such a way that the upper ends of the evaporating tubes and the lower ends, respectively, are interconnected preferably by means of tubular collecting chambers. The invention is further charac¬ terized in that a plurality of evaporating elements formed of parallel evaporating tubes preferably on the same level are installed in parallel in the same evaporator. A preferred embodiment of the invention is further characterized in that the collecting cham¬ bers of the separate evaporating elements are inter¬ connected in such a way that the collecting chambers at the upper end of the tubes, on the one hand, and the collecting chambers at the lower end of the tubes, on the other hand, are interconnected prefer¬ ably by means of a tubular connecting chamber or pos¬ sibly a connecting chamber of some other shape. An¬ other essential idea of the invention is that a li¬ quid to be concentrated is fed through a distributing basin at the upper end of the evaporating tubes on the outer surface thereof and vapour is fed through the collecting chambers inside the evaporating tubes preferably from the upper end downwards, and corre¬ spondingly, the condensate generated is discharged from the collecting chambers at the other end as well as the remaining vapour as vapour, both preferably through separate channels or through a common chan¬ nel. Vapour may be fed also from below, in which case the condensate is collected from below and the re- maining vapour from above. An advantage of an evaporator according to the invention is that it is easy and simple to manufac¬ ture, because it is formed of a plurality of parallel evaporating elements manufactured in the same way. Since the elements can be supported only at one end, no thermal strains to be compensated for arise, even though the heating surface tubes and the shell were made of different materials. Further, the tube system of the evaporator according to the invention is not easily blocked, because only vapour and condensation water pass through the evaporating tubes. In addi¬ tion, the structure according to the invention can be made relatively light, because only those evaporating elements which contain vapour have a high pressure. The wall thickness of the evaporating tubes of these elements can be selected in a desired manner without the thickness of the remaining part of the evapora¬ tor, e.g. of the shell, being affected thereby. More¬ over, the heating surfaces of the evaporator accord- ing to the invention are easy to clean, if needed, because possible dirt from liquor or some other li¬ quid, fastened to the heating surfaces, is situated on the outer surface of the evaporating tubes and the evaporator may thus be cleaned in a generally known manner by dissolving or for instance by means of a pressure washer or some other similar device without the tube system having to be rinsed inside.
The invention will be described in more detail in the attached drawings, in which Figure 1 shows schematically an evaporator ac¬ cording to the invention, in section parallel with evaporating elements,
Figure 2 shows the evaporator according to the invention in cross-section with respect to the evap- orating elements, Figures 3a and 3b show schematically a side and edge view of an evaporating element according to the invention and
Figure 4 shows schematically a perspective sec- tion view of an embodiment of the evaporator accord¬ ing to the invention.
Figures 1 and 2 illustrate schematically an evaporator according to the invention in section par¬ allel with evaporating elements, on the one hand, and in cross-section with respect to the evaporating ele¬ ments, on the other hand. The evaporator comprises a shell 1 containing a system 2 of evaporating tubes formed of evaporating elements similar to those to be shown schematically in Figure 3 later. A liquid to be concentrated, in this case black liquor, is fed through a connection 3 into the shell 1, to the bot¬ tom thereof. Liquor is discharged from the bottom of the evaporator through an outlet connection 4 and part of it is pumped by means of a schematically shown pump 5 through a circulating tube 6 into a dis¬ tributing basin 7 above the evaporating tube system 2, from which basin it flows substantially evenly on collecting chambers 8 of the evaporating elements and from there further along the surface of separate evaporating tubes 9 downwards. The use of the inven¬ tion is in no way restricted to black liquor, but it can also be used for the evaporation of other li¬ quids. At the lower end of the evaporating tubes 9, the concentrated black liquor flows along the surface of collecting chambers 10 of the lower end and falls subsequently into the liquor in the lower part of the shell 1 and mixes therewith. To provide evaporation, vapour is led through the evaporating tubes 9 and it is fed in through an inlet channel 11 in the upper part of the evaporating tube system 2. From there the vapour enters firstly a connecting chamber 12, which is connected to the upper collecting chambers 8 of the evaporating elements, so that the vapour is dis¬ tributed through these evenly to all evaporating tubes 9. Correspondingly, the remaining part of the vapour and condensate are collected, after having passed through the evaporating tubes 9, in the col¬ lecting chambers 10 of the lower end of the evaporat¬ ing elements, these collecting chambers being con- nected to a lower connecting chamber 13. From the lower part of the lower connecting chamber 13 starts an outlet channel 14 for condensate, through which channel the condensate is discharged, and respective¬ ly, from the upper part of the connecting chamber 13 starts an outlet channel 15 for vapour, through which channel the remaining heating vapour is exhausted. The water discharged from the black liquor under the influence of heating is exhausted as vapour through an outlet connection 16 at the upper end of the shell 1, and respectively, the concentrated liquor is dis¬ charged through a schematically shown distributing channel 17. Inside the evaporator, in front of the outlet connection 16, there is further a mist separa¬ tor 18 formed of lamellar sheets shown in Figure 4 in such a way that water or liquor drops possibly con¬ tained in the exhaust vapour hit the lamellas and flow down along these. The mist separator is mounted to be enclosed by a closed housing 19 on each side so that all exhaust vapour has to flow through the mist separator 18. Other known mits separator structures may be used as well in this evaporator.
Figures 3a and 3b show schematically an evapo¬ rating element 2a of an evaporator according to the invention in side and edge view, respectively. The evaporating element 2a comprises an upper collecting chamber 8, evaporating tubes 9 and a lower collecting chamber 10. A single evaporating element 2a is, as shown in Figure 3b, preferably a flat planar evapo¬ rating element formed of parallel evaporating tubes at a distance from each other, with each tube 9 con¬ nected to the collecting chambers 8 and 10, respec¬ tively, so that there is a connection between the collecting chambers 8 and 10 through each evaporating tube. The evaporating tubes 9 can be fastened to the collecting chambers 8 and 10 e.g. by welding or by some other suitable fastening method. The collecting chambers 8 and 10 are preferably tubular, which makes it possible to provide easily a structure as pressure resistant as possible. Since the evaporating elements 2a resist high pressure, high vapour temperatures, and consequently, high pressures can be used for the evaporation without the whole evaporator having to resist high pressure. Then the structure of the whole evaporator can be made relatively light, and to that part, the manufacturing costs lower than those of the known solutions. Correspondingly, no expensive accu¬ rately machined tube plates are required for the man¬ ufacture of the evaporating element 2a, but this ele¬ ment can be assembled easily of tubular parts. The evaporator according to the invention is simple to construct and its evaporating elements 2a are easy to manufacture, while the number of evapo¬ rating elements 2a and the number of evaporating tubes in one element may be selected as per needed. Since vapour passes inside the evaporating tubes 9, these are not blocked under the influence of the so¬ lution to be concentrated, such as liquor. Further¬ more, the outer surfaces of the evaporating tubes 9 are easy to clean in a generally known manner by dis- solving or for example by means of a pressure washer or some other similar device, if necessary, because between the tubes there are in practice such slits that enable an access to all surfaces in this way.
Figure 4 shows schematically one embodiment of the evaporator according to the invention in perspec¬ tive section. This figure is an illustrative presen¬ tation of how the evaporating tube system 2 is formed by positioning evaporating elements 2a in parallel so as to form a structure of square cross-section, for instance. The evaporating tube system 2 is suspended in place with respect to the shell 1 of the evapora¬ tor by using the collecting chambers 8 at the upper end of the elements 2a to support the tube system on holders 20 fastened to the shell 1. For this purpose, the length of the collecting chambers 8 is dimen¬ sioned so that both ends thereof extend outside the outermost evaporating tubes 9 of the evaporating ele¬ ments 2a and thus on the holders 20. Correspondingly, the upper, connecting chamber 12 is supported by one of the holders 20. In this embodiment, the lower con¬ necting chamber 13 is mounted at one end of the lower collecting chambers 10, while it was mounted in the middle part of the collecting chambers 10, below them, in the embodiment of Figure 1. The location of the connecting chamber 13 may thus be selected in a desired manner, which is not of essential importance to the operation of the evaporator. Identical refer¬ ence numerals are used in Figure 4 for identical parts in the previous figures, and as to those parts, they are not explained in more detail.
In the above specification and the drawings, the invention has been set forth only by way of ex¬ amples and it is in no way restricted thereto. The evaporating elements may be assembled in various man- ners according to the pressure to be used and dimen- sioned for each need separately. Except for being tubular, the collecting chambers 8 and 10 may also have another shape. The connecting chambers 12 and 13 may be connected in various manners to the collecting chambers 8 and 10, respectively, either to the ends thereof or to the middle, depending on the situation. Further, the vapour may be fed and exhausted, except in the previously described manner to the upper end of the evaporating tube system through the connecting chamber 12 and from the lower end of the evaporating tube system through the connecting chamber 13, also in the opposite direction. Then the vapour is fed into the connecting chamber 13 at the lower end of the tubes and it flows from below upwards through the tubes 9 into the upper collecting chamber and from there further into the upper connecting chamber 12, from where it is exhausted. Also in an embodiment, in which a separate inlet and outlet channel lead from each element outside the evaporator, the vapour may be fed to the lower end of the elements and exhausted from the upper end thereof. The simplest way of dis¬ charging the condensate is to discharge it from the lower end of the evaporating elements. Liquor or some other liquid to be evaporated may be fed, as shown in the Figures 1 and 2, to the bottom of the evaporator, or alternatively, directly into the distributing ba¬ sin 7. The liquor or other liquid to be evaporated may be discharged from the bottom of the shell 1 of the evaporator and circulated either in the manner shown in the figures or by taking the liquid to be circulated separately from the upper part of the li¬ quid layer in the bottom of the shell 1, for in¬ stance. The evaporating elements may be supported, except by suspending from the upper part, also to stand on their lower part, in which case holders cor- responding to the holders 20, for example, are ar¬ ranged to be supported by the chamber and the ele¬ ments are positioned on such holders in order to stand on their collecting chambers, for instance.

Claims

Claims:
1. Evaporator operating on falling film prin¬ ciple, comprising a shell (1) and a system (2) of evaporating tubes therein, the system comprising ver¬ tical evaporating tubes (9 ) , elements (7) for feeding an agent to be evaporated on the evaporating tubes (9) in such a way that it flows down along the eva¬ porating tubes (9 ) and forms a film on the outer sur- face thereof, and heating vapour inlet and outlet channels (11, 14, 15) connected to the inner portion of the evaporating tubes (9), c h a r a c t e r ¬ i z e in that the evaporating tube system (2) is formed of a plurality of parallel evaporating ele- ments (2a).
2. Evaporator according to claim 1, c h a r ¬ a c t e r i z e d in that each evaporating element (2a) comprises a plurality of parallel evaporating tubes (9 ) at a distance from each other and the evap- orating tubes (9) of each evaporating element (2a) are interconnected at their upper and lower ends, re¬ spectively, by collecting chambers (8, 10) and that the inlet and outlet channels (11, 14, 15) for heat¬ ing vapour are connected to the collecting chambers (8, 10).
3. Evaporator according to claim 2, c h a r¬ a c t e r i z e d in that there is a connecting chamber (12, 13) at each end of the evaporating tube system (2) and that the collecting chamber (8, 10) of each evaporating element (2a) is connected to the connecting chamber (12, 13) at the same end and that the inlet and outlet channels (11, 14, 15) for heat¬ ing vapour are connected to the connecting chambers (12, 13).
4. Evaporator according to claim 3, c h a r- a c t e r i z e d in that the vapour inlet channel (11) is connected to the connecting chamber (12) at the upper end of the evaporating tube system (2) for feeding vapour through the evaporating tubes (9) from above downwards and that the outlet channel (14) for condensate is connected to the lower part of the con¬ necting chamber (13) at the lower end of the evapo¬ rating tube system (2) for discharging condensate generated from the vapour, and the outlet channel (15) for vapour is connected to the upper part, re¬ spectively, for exhausting incondensed vapour.
5. Evaporator according to claim 3, c h a r¬ a c t e r i z e d in that the vapour inlet channel (11) is connected to the connecting chamber (13) at the lower end of the evaporating tube system (2) for feeding vapour through the evaporating tubes (9) from below upwards and that the outlet channel (14) for condensate is connected to the lower part of the con¬ necting chamber (13) at the lower end of the evapo- rating tube system (2) for discharging condensate generated from the vapour and that the vapour outlet channel (15) for exhausting incondensed vapour is connected to the connecting chamber (12) at the upper end of the evaporating tube system (2) .
6. Evaporator according to any of the foregoing claims, c h a r a c t e r i z e d in that the evap¬ orating tube system (2) formed of evaporating ele¬ ments (2a) is mounted to be suspended from its upper end and to be supported by holders (20) fastened to the shell (1).
7. Evaporator according to claim 5, c h a r¬ a c t e r i z e d in that the collecting chambers (8) at the upper end of the evaporating elements (2a) are provided with such a length that their ends ex- tend on the holders (20) transverse to the shell (1) in such a manner that the evaporating tube system (2) is suspended to be supported by the collecting cham¬ bers (8).
PCT/FI1994/000309 1993-04-01 1994-07-05 Evaporator operating according to the falling film principle WO1996001140A1 (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
FI931496A FI93427B (en) 1993-04-01 1993-04-01 Falling membrane evaporator
CA002120297A CA2120297C (en) 1993-04-01 1994-03-30 Evaporator operating on falling film principle
PCT/FI1994/000309 WO1996001140A1 (en) 1993-04-01 1994-07-05 Evaporator operating according to the falling film principle
SK1653-96A SK281918B6 (en) 1993-04-01 1994-07-05 DEPARATOR WORKING BASED ON THE PRINCIPLE OF THE FALLING FILM
BR9408600A BR9408600A (en) 1994-07-05 1994-07-05 Evaporator operating according to the falling film principle
AT0907394A AT407119B (en) 1994-07-05 1994-07-05 PRINCIPLE OF A FALLING FILM WORKING EVAPORATOR
RU97101456A RU2122456C1 (en) 1994-07-05 1994-07-05 Evaporator functioning in agreement with concept of falling film
ZA945084A ZA945084B (en) 1993-04-01 1994-07-13 Evaporator operating according to the falling film principle
FR9408976A FR2722866B1 (en) 1993-04-01 1994-07-20 OPERATING EVAPORATOR ACCORDING TO THE PRINCIPLE OF THE RUNOFF FILM

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI931496A FI93427B (en) 1993-04-01 1993-04-01 Falling membrane evaporator
PCT/FI1994/000309 WO1996001140A1 (en) 1993-04-01 1994-07-05 Evaporator operating according to the falling film principle

Publications (1)

Publication Number Publication Date
WO1996001140A1 true WO1996001140A1 (en) 1996-01-18

Family

ID=26159475

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1994/000309 WO1996001140A1 (en) 1993-04-01 1994-07-05 Evaporator operating according to the falling film principle

Country Status (1)

Country Link
WO (1) WO1996001140A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105074086A (en) * 2013-03-14 2015-11-18 威立雅水处理技术公司 System and process for recovering heat from weak black liquor in a wood pulping process
WO2018143886A1 (en) * 2017-02-03 2018-08-09 Valmet Ab Heat transfer tube and method for manufacturing a heat transfer tube

Citations (4)

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Publication number Priority date Publication date Assignee Title
FR2593718A1 (en) * 1986-01-31 1987-08-07 Kestner App Evaporateurs Falling film evaporator
EP0251667A1 (en) * 1986-06-25 1988-01-07 A. Ahlstrom Corporation Tube-type evaporator
US4810327A (en) * 1984-04-24 1989-03-07 Ahlstromforetagen Svenska Ab Falling film evaporator of the vertical-tube type
US4917771A (en) * 1987-02-26 1990-04-17 Oy Santasalo-Sohlberg Oy Distilling apparatus

Patent Citations (4)

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Publication number Priority date Publication date Assignee Title
US4810327A (en) * 1984-04-24 1989-03-07 Ahlstromforetagen Svenska Ab Falling film evaporator of the vertical-tube type
FR2593718A1 (en) * 1986-01-31 1987-08-07 Kestner App Evaporateurs Falling film evaporator
EP0251667A1 (en) * 1986-06-25 1988-01-07 A. Ahlstrom Corporation Tube-type evaporator
US4917771A (en) * 1987-02-26 1990-04-17 Oy Santasalo-Sohlberg Oy Distilling apparatus

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105074086A (en) * 2013-03-14 2015-11-18 威立雅水处理技术公司 System and process for recovering heat from weak black liquor in a wood pulping process
WO2018143886A1 (en) * 2017-02-03 2018-08-09 Valmet Ab Heat transfer tube and method for manufacturing a heat transfer tube
WO2018143880A1 (en) * 2017-02-03 2018-08-09 Valmet Ab Heat transfer tube and method for manufacturing a heat transfer tube
WO2018143885A1 (en) * 2017-02-03 2018-08-09 Valmet Ab Heat transfer tube and method for manufacturing a heat transfer tube
US10926189B2 (en) 2017-02-03 2021-02-23 Valmet Ab Heat transfer tube and method for manufacturing a heat transfer tube
US10933342B2 (en) 2017-02-03 2021-03-02 Valmet Ab Heat transfer tube and method for manufacturing a heat transfer tube
US10981080B2 (en) 2017-02-03 2021-04-20 Valmet Ab Heat transfer tube and method for manufacturing a heat transfer tube

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