US 3820582 A
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United States Patent [191 Riinnholm I DEVICE FOR EVAPORATION OF LIQUIDS v  Inventor: Arvi Riinnholm, Pori, Finland  Assignee: 0y W. Rosenlew AB Metallindustrin, Pori, Finland  Filed: Dec. 2, 1971  Appl. No.: 204,079
 Foreign Application Priority Data Dec. 14.1970 Switzerland ..l6912/70  US. Cl. 159718, 202/174  Int. Cl B0ld l/26  Field of Search 159/18  References Cited UNITED STATES PATENTS 2,435.424 2/l948 Crews 159/18 3,303,l06 2/1967 Standiford,.lr. 159/18 3,487,873 l/l970 Bromley et al. 159/18 FOREIGN PATENTS OR APPLICATIONS 576,838 5/1924 France 159/18 June 28, 1974 1,161,852 l/l964 Germany l59/l8 Primary Examiner-Norman Yudkoff Attorney, Agent, or FirmFleit, Gipple & Jacobson [5 7 ABSTRACT A device for evaporation of liquids comprising evaporation units coupled in series. The evaporator units include a tube heat exchanger and a separating device coupled thereto. The heat exchangers are arranged aligned above each other whereby each heat exchanger forms a preseparator for the liquid to be evaporated in that heat exchanger and a subsequent separator for the steam evaporated in the preceding heat exchanger.
14 Claims, 7 Drawing Figures E I NIEB W $820582 SHEET 1 BF 7 12 COVER LIQUID 2 I DISTRIBUTOR-26 12-COVER 1 LIQUID 27a DISTRIBUTOR 12COVER 13b FILM \STEAM 14b CYCLONE 1a 40 12-COVER 42 LIQUID DISTRIBUTOR 48 STEAM CYCLON FEED PATENTEDJUHBWH Y 3.820.582
SHEET 8 OF 7 STEAM CYCLONE LIQUID DISTRIBUTOR- STEAM CYCLONE DEVICE FOR EVAPORATION F LIQUIDS The present invention relates to a'device for evaporation of liquids, consisting of a number of evaporator units connectedin series and of separation devices coupled to them.
Evaporation devices of this type are used, for exam-' I ple, in cellulose industry for evaporation of the waste vices into the desired sequence and in series.
Thisis why it is desirable that the space requirement of an industrial plant could be reduced with unreduced capacity or that the capacity could be increased and the space requirement nevertheless reduced; The purpose of the present invention is to present a device for solving this problem.
The device according to'the invention is mainly char acterized by the special features indicated in claim 1.
The invention will be described more closely below under reference to the attached drawings, which give schematic views of different embodiments of the inventron. a
FIG. 1 showsa vertical section of a three-stage liquid evaporation device for a cellulose plant.
FIG. 2 similarly shows another embodiment of the invention. I
FIG. 3 shows onv a larger scale a vertical section of a subsequent separator, included in FIGS. 1, 2 and 5, for liquid-containing steam as fitted with an afterseparating drop separator.
FIG. 4 shows a subsequent separator of FIG. 3 as fitted with'a different embodiment of an after-separating drop separator.
FIG. 5 shows another embodiment according to FIG.
FIG. 6 shows a vertical section of another embodiment in whichthe steam distributing section has been somewhat modified.
FIG. 7 shows a vertical section of another embodiment of the present invention.
' In FIG. 1 L 1, L-2, and L-3 illustrate vertical tube heat exchangers belonging to the different stages in a three-stage evaporator unit. The heat exchangers are bound together by a cylindrical jacket 1 which limits the tube groups and whose top end is fitted with an end cap 2 and bottom end with an end cap 3. Inside the jacket pairs of tube plates, 4-5, 6-7 and 8-9 have been arranged, towhich a number of tubes have been fastened so that they form separate heat exchangers L-l, L2 and L3 and that after the bottom tube plates 5, 7 and 9 of the heat exchangers pre-separating spaces E-l, E-2 and E-3 are formed. Among these the height of the pre-separating space E-2 between the tube plates 7 and 8 is at least equal to the length of the tubes 10 that are used in the heat exchangers in order that tubes that must be replaced or new tubes that must be installed can be installed into the heat exchangers L-2 and IJ-3 and inserted into the separating space E -2 through an opening 11 with a cover in its wall, whereas the tubes. are inserted into the heat exchanger L-l through the removable end cap 2 at the top end of the exchanger.
The tubes can also be replaced to the various heat exchangers through openings 12 in line with each other in the tube plates, fitted with covers, and through the end cap 2. In an evaporator set with several stages it is hereby, however, required that the height of every other separating space is equal to the length of the tubes.
The top sections of the heat exchangers are enclosed by steam distributor jackets 13a and 13b, of which the IS jacket 13b in the heat exchangers L-2 and L-3, to-
gether with section 14b of jacket 1, the top section of which is fitted with an opening and which is located inside the steam distributor jacket l3b, forms a subsequent separator cyclone for steam. The steam distributor jacket 13a in the heat exchanger L-l similarly, to-
gether with section 14a, forms a normal steam distributor into which the primary steam is fed through a pipe 31. To the steam distributor jacket 13b of each heat exchanger, L-2 and L3 a steam pipe 15a and 15b starting out from the separating space 5-1 and E-2 of the respective preceding stage is connected and a liquid pipe 16a and 16b, fitted with a throttle means 17, goes from the bottom edge of the steam distributor jacket to the separating space of the respective same stage.
The jacket section 14b in the'subsequent separator cyclones of the heat exchangers 11"2 and L-3 is below the inlet of the steam pipe fitted with a hole 18, shown more closely in FIGS. 3 and 4, for regulating the upper limit of the liquid level so that steam surges against the tube plate can in no case be produced but the liquid passes in such a case past the steam plane directly to the condensation side. Moreover, the subsequent separator cyclones are, according to FIG. 3 or 4 fitted with a drop separator l9, which may be of a known type, for example, a Mesh demister.
Each heat exchanger L-3, L-2, L-l is fitted with a separate interior heat exchanger 20, 21 and 22, which constitutes a part of the tube group of the said heat exchanger. These are connected by means of the pipes 23 and 24 through the separating spaces E-2 and E-l.
The feed liquid is pumped by means of a pump 25 through a pipe 25a and through the heat exchangers 20, 21 and 22 to the top end of the heat exchanger L-l into the space limited by the end cap 2.
Each evaporating tube 10 of each heat exchanger L-l, L-2, L-3 is at its top end fitted with some known liquid distributor device 26 which guides the liquid to each tube so as to form a film on its inner surface. The distributor device is dimensioned so that it corresponds to the pressure difference between the different stages. Underneath the tube plate at the bottom end of each heat exchanger unit L-l, L-Z, L-3 in the separating space E-l, E-2 and E-3 there is a conical plate system 27a arranged, in which the lower cone is fitted with holes along its lower sphere, against which the hot liquid-steam mixture streaming out of .the tubes 10 is tossed when the liquid is separated from the steam. The liquid runs to the heat exchanger tube system of the following stage by means of the liquid distributor devices 26 therein. In this way the liquid that is to be evaporated streams downwards while being evaporated through the heat exchanger stage L4 to the separating space [5-1 and further through L2 to E2 and from there through L3 to the separating space E3, from which the evaporated liquid is removed from the bottom ofthe end cap 3 by means ofa pipe 28 and a pump 29. The steam is removed from the separating stage E3 through a pipe 30 into a tube-surfacecondenser Pl.
The condensate of fresh steam is removed from the heat exchanger L-l through a pipe 32 and a pump 33. What is called secondary condensate is removed from the condensing side of the heat exchanger L-2 along a pipe 34 and it expands through a throttle means 35 to the condensing side of the heat exchanger L-3. The condensate from the unit L-3 is removed through the pipe 36 to an outlet pump 37 for secondary condensate. To the suction side of the pump has also been connected the condensate from the surface condenser Pl by means of a pipe 38. Hereby the surface condenser may be located as low down as the pressure difference between the heat exchanger L3 and the lower tube plate of the surface condenser P-l allows. v
The removal of air from the heat exchanger Ll takes place through a pipe 39 and through a throttle means in this pipe.
The removal of gas from the heat exchangers L-2 and L3 takes place through the pipes 40 and 41, respectively, and through throttle means in them, 42 and 43 respectively. into the steam pipe 30, which leads to the surface condenser P-l. The surface condenser P-l is fitted with a similar subsequent separating cyclone for steam and with a drop separator as described in connection with the heat exchangers L-2 and L-3. The liquid starting from the subsequent separating cyclone is conducted by means ofa pipe 44 into the pipe 28 and further to the pump 29 for removal of the liquid.
The evaporation set. which consists of the heat exchangers L-l, L-2, L-3 in this way connected together, stands on a foundation 45 consisting of a prolongation of its own jacket I. The evaporator set can be located outdoors and the surface condenser PI, for example, inside a building on a plane as indicated in FIG. 1. In FIG. I no. 46 describes a pipe for cooling water of the surface condenser P-1 and no. 47 a pipe for the removal of warm water.
A pipe 48 leads the gases into a vacuum device, which is in the drawing designated with 49. The vacuum device may consist of any known vacuum device, for example. a vacuum pump, the pipe for whose gasket and cooling water is marked with 50.
In FIG. 2 L-I, L-2, L-3, L-4 and L-S illustrate heat exchangers of the different stages in a five-stage evaporator unit. which heat exchangers are interconnected by means of a cylindrical jacket 1, whose top and bottom ends are fitted with end caps 2 and 3.
Into the jacket 1 pairs of tube plates 4-5, 6-7, 8-9, 39-40 and 4142 have been arranged to which a number of tubes have been fastened so that separate heat exchangers LI, L-2, L3. L-4 and L-S, are formed and that after the lower tube plates 5, 7, 9, 40 and 42 pro-separating spaces El, E2, E3, E4, and E-5 are formed. The heights of the separating spaces E-2 and E4 are hereby at least equal to the length of the tubes 10 used in the heat exchangers.
The top sections of the heat exchangers are enclosed by steam distributor jackets 13a and 13b. of which the jacket 13b in the heat exchangers L-2 to L-5, together with section 14b of jacket 1, the top section of which is fitted with an opening and which is located inside the steam distributor jacket 13b, forms a subsequent separator cyclone for steam. The steam distributor jacket 13a in the heat exchanger L-l similarly, together with section 14a, forms a normal steam distributor which is open upwards and into which the primary steam is fed through a pipe 3].
To the steam distributor jacket 13b of each heat exchanger L2, L-3, [f4 and L-5 a steam pipe 15a, 15b, 15c and 15d starting out from the separating space El E2, E3 and E4 of the respective preceding stage is connected, and in the corresponding way an outlet pipe 16a, 16b, 16c and 16d for separated liquid, fitted with a throttle means 17, goes out from the bottom edge of the steam distributor jacket.
Each tube 10 of each heat exchanger Lr-l to L-5 is at its top end fitted with liquid distributor device 26, as was described in connection with FIG. 1. Underneath the tube plate at the bottom end of the heat exchanger units L4 to L-S there is, arranged in the separating space E-l and ES, a conical separating plate system 27a, in which the lower cone is fitted with holes along its lower sphere. When the hot liquid-steam mixture coming from the tubes 10 is tossed against the separating plate system, the liquid is separated from the steam. Similarly, underneath the tube plate at the bottom end of the heat exchanger units L-2, L-3 and L-4 there is, arranged in the separating spaces E-2, E3 and E4, a conical separating plate system 2712, wherein the lower cone is closed along its outer sphere. The main difference in respect of the embodiment according to FIG. 1 lies therein that the stages L-3, L-4 and L-5 have no internal heat exchangers of the units and that the entire evaporating device is, in respect of the liquid, divided into pre-evaporation and after-evaporation stages.
The pre-evaporation stage consists of the heat exchangers L3, L4 and L-S and the after-evaporation stage of the heat exchangers L-I and L-2. The liquid that is to be evaporated is fed by means of a pump 25 into a pipe 250 and distributed by means of the pipes 25!), 25c and 25d to the separating spaces E2, E3 and E4 of the units L2, L3 and L-4 underneath the separating plate systems 2712 therein. Since the feed liquor has a high temperature, the steam that has been formed by means of its expansion in the separating space E2, E3 and E4 passes between the cones of the separating plate system 2712 into the upper space and is combined with the steam from the preceding stage and passes through the respective steam pipes 15b, 15c and 15d into the heat exchangers L3, L-4 and L-S, The liquid evaporated at the stages L-3, L4 and L-5 is collected to a pump 29 by means of pipes 51 and 52, which start from the space formed by the lower cone in the separating plate system 27b of the pre-separating stages E3 and E4, as well as through a pipe 28 from the bottom limited by the end cap 3. The pump 29 removes the pre-evaporated liquid, for example, into an intermediate solution tank, to a spirit distillery or directly to the after-evaporation. The pump 29 may consist of three separate pumps or of a multi-stage pump.
In other words, the liquid fed into a stage is only evaporated in this stage and only the steam separated from it is used in the following stage, whereby the liquid removed from each stage and collected receives the same final concentration as would have been achieved by feeding the entire feed liquid into stage L-3 and further downstream to L4 and L-S, but with a higher final temperature, without using internal after-heaters arranged in the units or possible outer heat exchangers. The liquid that has expanded after being fed in, streams to the heat exchangers L3, L-4 and LS through the liquid distributor device 26 at the top end of the tubes 10, which device guides the liquid into each pipe in order to form a film on its inner surface. The steam from the separating stage ES is removed through a pipe 30'into a tube-surface condenser P-l.
The liquid that is to be after-evaporated is fed either byv means of a pump 29 or a pump 53 through a pipe 54 and a pipe 24 which passes through the interior heat exchangers 20, '21 arranged in the heat exchangers L2 and Ll and through the separating space E-l that connects these into the space limited by the end cap 2 at the top end of the heat exchanger L-l. The interior heat exchangers 20 and 21 constitute a part of the tube group of the heat exchangers L2 and LI, in which the top ends of the evaporation tubes are fitted with a liquid distributor device 26.
The liquid that has been evaporated in the stage Ll through the punched separating plate system 27a in the separating space E-l passes downwards to the stage L-2 at the same time as the steam resulting from stage Ll is guided by means of a steam pipe a into the steam distributor jacket 13b of the stage L2. From the top side of theseparating system 27b in the separating space E2 the steam departs through a pipe 15b into the heat exchanger'L3 at the same time as the evaporated liquid is removed from the space formed by the lower cone in the same separating plate system 27b through a pipe 55 and by means ofa pump 56. The outlet pipe l6a. going out from the subsequent separator cyclone of the stage L2, for separated liquid is connected'to the separating space E2 at the bottom side of the separating plate system 27b.
The condensate of fresh steam from the heat exchanger L-l is removed through a pipe 32 and a pump 33. The secondary condensate is removed from the condensate side of the heat exchanger L2 along a pipe 34 and it expands through a throttle means 35 to the condensate side of the heat'exchanger L3.
Similarly the condensates of the units L3 and L4 are removed through pipes 34aand 34b and through the throttle means 35a and 35b in these pipes always to the condensate side of the following stage. The secondary condensate from stage LS departs through a pipe 36 to an outlet pump 37 for secondary condensate. The
condensate from the surface condenser P-l is also conducted to the suction side of this pump through a pipe 38.
The air removal from heat exchanger L-l takes place through a pipe 39 and through a heat exchanger in it.
The removal of gas from the heat exchangers L2, L-3,'
- without pre-heating directly into the top end of the heat exchanger Ll, whereby the interior heat exchangers and 21 in the heat exchanger stages L2 and Ll are omitted together with the collecting pipe 24. In the other respects the transmission of the liquid and the steam takes place in the way described in connection with FIG. 2. The embodiment can be further modified so that the feeding of the liquid to be after-evaporated is distributed without preheating to the stages Ll and L2 by arranging a feeding branch from the pipe 54 to the bottom side of the separating plate system arranged in the pre-separating space 5-1. At the same time the separating plate system 27a is substituted for by a plate system 27b, in which the liquid evaporated from the space formed by the lower cone in the stage Ll is connected by means of a pipe to the liquid that comes through a pipe 55 from the space formed by the lower cone in the'separating plate system 27b in the preseparating space E2. Hereby the same situation is reached as in the pre-evaporation stage, i.e., the liquid fed into a stage is evaporated only in this stage and only the steam separated from it is used in the following stage, whereby the liquid removed from each stage and collected receives the same final concentration, but a higher temperature, without interior preor afterheaters, than by means of feeding all the liquid into stage Ll. Since the evaporated liquid that is to be removed is consequently superheated, it is expanded in a separate expansion vessel between the pipe 55 and the pump 56. The steam separated in the vessel is conducted by means of a pipe into the steam pipe 15b leading into the stage L3, and the liquid is removed by means of the pump 56.
FIG. 5, which shows a modification of the embodiment according to FIG. 2 is different mainly in the respect that the pre-evaporation stage, which consists of the stages L3, L4 and LS, and the after-evaporation stage, which consists of the stages Ll and L2, consist of separate tower-shaped evaporation units each standing on a fundament of its own, 45b and 45a, and that the primary steam unit Ll of the after-evaporation stage is located lowest in the-set.
The secondary condensate is removed from the condensate side of the heat exchanger L2 through a pipe 57 and through a throttle device 58 in the pipe into an expansion vessel 59. The expansion steam is conducted from the expansion vessel through a pipe 600 to steam pipe 15b and through a pipe 60b to steam pipe 15c and the expanded liquid through a pipe 61 to pipe 34b.
In the FIGS. 1a and lb illustrate a cylindrical jacket which connects the different stages in each of the separate evaporation units, and 2a, 2b and 3a, 3b illustrate the end caps arranged in their top and bottom ends. The separating plate system in the separating space E2 after the stage L2 has been replaced by a removable section 62 that separates the stages L2 and L-l from each other. The liquid that is to be after-evaporated is fed by means of pump 29 or pump 53a along the pipe 54 and through a four way valve 63 along a pipe 65 to the upper end of the unit L-2 to the space limited by its end cap 2a or along a pipe 66 to the upper end of the unit L-1 to the space separated by the section 62. The liquid evaporated in the stage L2 departs from the separating space E2 from the bottom of the space 62 through a pipe 66a by means of a pipe passing by the pump 67 and through the four way valves 68 and 63 along a pipe 66 to the top end of the unit L-l or by means of the pump 67 through the four way valve 68 and a pipe 69. The evaporated liquid from stage Ll is removed from the bottom of the space 62 of the separating space El by means of a pipe 71 and a pump 72 through the valve 68 and the pipe 69 or through the four way valves 68 and 63 and the pipe 65 to the top end of the unit L-2. By means of the four way valves and the pipes combining them the units L-l and L2 can, if necessary, be exchanged with each other so that each of them comes to work alternatively as the strong liquid unit, whereby after exchange the more diluted liquid washes the unit that has worked as the strong liquid unit, and the evaporation takes place alternatively as upstream evaporation and alternatively as downstream evaporation. The outlet pipe l6a, coming from the subsequent separator cyclone of the stage [1-2, for separated liquid is connected to the separating space E-2.
In the other respects the embodiment according to FIG. 5 corresponds to the description given above.
FIG. 6 shows a modification of the embodiment according to FIG. 2 in respect of the steam distributor section in the stages L-3 and L-4.
The embodiment differs from what is shown in FIG. 2 mainly in the respect that the outer steam pipe 150, which in FIG. 2 connects the separating space E-3 of the stage L-3 with the stage L-4, and the separating plate system 27b in the separating space E3 have been substituted for by an annular pipe channel 76 limited between the jacket 1 and the inner steam distributor jacket 13b, which channel connects the pre-separating space E3 to the stage L4, and together with a prolongation 14b fitted with openings at the top end of the steam distributor jacket 13b, forms a subsequent steam separator cyclone, as well as a collecting cone 73 fastened to the hole plate 9 of the stage L-3 and a distributor pipe 74 which forms a prolongation of the collecting cone 73 and projects into the pre-separating space E-3 limited by the steam distributor jacket 13b and the tube plate 39 of the stage L-4. The bottom end'of the distributor pipe 74 is closed and the jacket is fitted with openings.
The upper tube plate 39 of the stage L4 is fastened to the prolongation 14b of the steam distributor jacket 13b. and the upper end of the steam distributor jacket 13b is fitted with steering blades 75 adjoining the cover 1 and steering the steam streaming as a rotating movement down in the annular pipe channel 76.
The liquid separated on the bottom of the subsequent separator cyclone is removed by means of a pipe 16c, which is fitted with a throttle means 17, into a distributor pipe 74. In respect ofthe other stages the above discription is applicable.
By means of an embodiment according to FIG. 6 uniform, towerlike construction limited by the jacket 1 is obtained.
FlG. 7 illustrates an embodiment in which the steam flow in each heat exchanger is arranged to take place in a direction opposite to the direction of the liquid flow. Corresponding parts have been provided with the same numerals as in the preceding embodiments.
The embodiment according to FIG. 7 differs from the embodiment according to FlG. 6 in that an annular tubular channel 76 is provided between the cylindrical jacket I and the internal steam distributor jacket 1311. This channel 76 connects the pre-separating space E-4 with the heat exchanger L3 and forms together with the upper extension 1412 of the jacket 13h a subsequent steam separating cyclon. The channel 76 forms together with a collecting cone 73 fastened to the tube plate 8 of the heat exchanger L,3, a distributor pipe 74 extending into the pre-separating space E-3, a central pipe 73a fastened to the tube plates 8 and 9 and a collecting cone 73b fastened to the tube plate 9, a liquid circulation system for guiding liquid to be evaporated from the collecting cone 73 through the central pipe 73a and the collecting cone 73b to the heating tubes 10 and further from said tubes through the space 73(' formed between the collecting cone 73 and the jacket 1 to the distributor pipe and further to the preseparating space E- 3. Liquid is fed into the system from the pipe 54 and the evaporated liquid is fed from the stage L-3 by means of the pipe 66/) to the stage L4 and further from the stage L-4 by means of the pipe 71!) to the stage L-S.
The lower tube plate 9 of the heat exchanger L-3 is fastened to the jacket 1 by means of guiding blades 75 which cause the steam to flow in a spiral upwards in the channel 76. The liquid separated in the subsequent separating cyclone formed by the channel 76 flows back directly to the collecting cone 73.
The invention is not restricted to the above embodiments, presented as examples, but it also relates to evaporation devices fitted with some known vertical tube heat exchanger that can be modified within the framework of the patent claims. The embodiments according to the present invention are particularly advantageous if tube heat exchangers fitted with double tubes, for example according to the Swedish Pat. No. 320,991, are used.
What 1 claim is:
1. A device for evaporating liquids comprising a plurality of evaporator units connected in series, each of said evaporator units having a heat exchanger section with vertical heat exchanger tubes having open ends arranged therein and a vapor-liquid separating section downstream of said heat exchanger section, at least two of said evaporator units being vertical and stacked on top of one another, the heat exchanger section in the first evaporator unit having a steam distributor section and means for admitting steam therein, each of the other heat exchanger sections having a vapor distributor section comprising a liquid separating cyclone for separating liquid from incoming vapor, and means for tangentially introducing separated vapor to each ofsaid vapor distributor sections from one of said vapor-liquid separating sections and for tangentially introducing said separated vapor into said vapor distributor section to separate liquid therefrom.
2. The device of claim 1 in which the evaporator units have a common jacket and in which the evaporator units form a continuous tower-like unit.
3. The device of claim 1 and further comprising means for transporting separated liquid from at least one of said vapor distributor sections to the vaporliquid separating section of the succeeding evaporator unit.
4. The device of claim 1 in which said liquid separating cyclone includes a drop separator for separating liquid from incoming vapor.
5. The device of claim 1 in which the vapor distributor section includes a jacket wall surrounding the vertical heat exchanger tubes and having at least one hole therein below the separated vapor inlet for regulating the separated liquid level.
6. The device of claim 1 in which the height of at least every other vapor-liquid separating section is at 9 least equal to the length of the vertical heat exchanger tubes used inthe evaporator units.
7. The device of claim 1 in which the openings in the vertical heat exchanger tubes in adjacent evaporator units are aligned and in which the heat exchanger sections have end plates which are adapted to be closed by means of a cover.
8. The device ofclaim l in which the means for trans porting the separated vapor to the vapor distributor section from the vapor-liquid separating section is arranged to transport the vapor in a direction opposite to the direction of liquid flow.
9. The device of claim 1 in which the means for transporting vapor to the vapor distributor section from the vapor-liquid separating section is arranged to transport the vapor in the same direction as the direction of liquid flow.
10. The device of claim 1 and further including means for simultaneously transporting feed liquid to at least two separate evaporator units arranged so that the feed liquid is evaporated only in the evaporator unit into which it is introduced and further comprising means for combining the separated liquid removed from each of the vapor-liquid separating sections of said evaporator units.
11. The device of claim 10 and further including means for transporting the separated vapor from said vapor-liquid separating sections to the succeeding evaporator unit.
12. The device of claim 1 in which at least one of said evaporator units includes a heat exchanger for preheating the feed liquid before it is introduced into said vertical heat exchange tubes.
13. The device of claim 1 in which said vaporliquid separating zones includes a separating plate having openings therein for separating and removing liquid.
14. The device of claim 1 in which said liquid separating cyclone includes steering blades for effecting said tangential movement of said separated vapor.