JPH0549802A - Can effective in horizontal vaporizing device by plate heat exchanger of irregular surface type - Google Patents

Abstract

PURPOSE: To evaporate a salt water in the desalting method or evaporate other kinds of liq. such as a black liquor from the paper and pulp treatment by the use of multiple effect evaporators. CONSTITUTION: Each multiple-effect evaporator includes sets 20, 21 of rugged surface type plate heat exchanging evaporator element, which are long in the horizontal direction. A heating fluid flowing in the horizontal direction, for example, steam is introduced into an internal passage of an evaporation element of each multiple-effect evaporator, and a circulating liq. head is provided so that a heating fluid is made to flow downward from the liq. head in the form of a thin liq. film to be evaporated on the external surface of sets of the plates on the rugged surface. The evaporated vapor is pulled out of a liq.-drop separator 48 and is used as a heating fluid to a multiple-effect evaporator at the next stage. A non-evaporated circulating liq. and the liq. separated by a liq.-drop separating operation are re-circulated into the liq. head attached to each multiple-effect evaporator. A clean condensate 61 (distilled water, for example) is extracted from the multiple-effect evaporator at the final stage.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an evaporation device, a method of evaporating an evaporable liquid, and individual evaporation effect cans, which are advantageous for many specific processes. The present invention is
It is particularly applicable to desalination of water and wash water, and evaporation of black liquor during paper pulp production, but is not limited thereto.

[0002]

BACKGROUND OF THE INVENTION Conventional evaporators for desalination of water are typically multiple evaporators having multiple heat transfer tubes. Both vertical and horizontal tube evaporators are used. Typically, salt water is sprayed on the outside of the tube to produce steam. The steam produced from the salt water flows to the next utility can where it provides heat for further evaporation at lower temperatures. The salt water may be partially preheated with some steam and flows countercurrently with steam. In most cases, the main steam and downstream steam flow inside a horizontal tube where they condense and contribute to the product water stream. The conventional multi-effect evaporator used to evaporate black liquor in the production of paper pulp is a vertical type,
As a heating element, there is a vertically extending uneven surface type plate heat exchanger, for example, the plate heat exchangers described in U.S. Pat. Nos. 3,211,219 and 3,512,239. The disclosures of each are incorporated herein by reference).

[0003]

SUMMARY OF THE INVENTION According to the present invention, there are provided multiple effect evaporators, methods of performing evaporation using multiple effect evaporators, and individual effect cans of evaporators, many of which are provided. It has the advantageous features of. Each effect can of the present invention includes an uneven surface type plate heat exchanger that is long in the horizontal direction. The uneven surface type plate heat exchanger is a set of one set or more sets and is arranged in a state of being vertically stacked. The structure with horizontally arranged plates with uneven surface has high heat transfer coefficient, uniform liquid distribution, relatively small vapor pressure loss between heating elements, and good droplet separation (minimum Accompany)). Therefore, this is an advantage over conventional horizontal tubular evaporators. It also has economic advantages over known vertical textured surface plate heat exchanger evaporators used in paper pulp manufacturing. The present invention achieves 15-20% better packing efficiency in the same space than that of comparable vertical textured plate heat exchanger evaporators, with corresponding savings in equipment costs in general. Be done.

According to one embodiment of the present invention, there is provided a method of vaporizing a vaporizable liquid using a multi-effect vaporizer. In a multi-effect evaporator, each effect can has one or more sets (eg, first and second sets) of horizontally elongated textured plate heat exchanger evaporator elements. By the way, this element is described in U.S. Pat. No. 3,211,
219 and 3,512,239. Each set of elements has internal passages and an external heat exchange surface, with the first set being arranged above the second set. The effect cans are connected in series, the first-stage can has the highest temperature and the last-stage has the lowest temperature. The method includes the following steps (when using the first and second set plate elements): (A) Introducing a horizontally flowing heating fluid into the internal passages of both two elements of the first effect can and into the internal passages of at least the second set of elements in all subsequent stages of the effect can. (B) Providing a circulating head of liquid to be evaporated on top of the first set of elements of each effect can. (C) Flowing liquid downward from the liquid head to the outer surfaces of the first and second sets of heat exchange elements of each effect can. (D) A step of extracting the vapor of the evaporative circulating liquid from each effect can and removing the droplets from the vapor to separate the entrained liquid from the vapor. (E) A step of recirculating the circulating liquid that has not evaporated to the liquid head attached to the effect can. (F) A step of horizontally supplying the steam extracted from each effect can to the effect can of the next stage as the heating fluid of the above step (a) (however, the final stage is an exception). And (g) a step of taking out a clean condensate from the final effect can. It is also possible to add a step (h) of preheating the liquid to be evaporated before introducing it into the liquid head of the first effect can. This preheating is accomplished by passing the liquid through the internal passages of the first set of elements of all utility cans except the first stage utility can. The liquid flows countercurrently to the steam flowing through the second set of internal passages from the first effect can to the final stage effect can. It is also possible to add a step of compressing the vapor extracted from the final effect can, raising the temperature of the final stage, and supplying this vapor as compressed fluid to the first effect can as the heating fluid in step (a). .. Furthermore,
It is also possible to add a step (j) of removing the non-condensable gas from each effect can and recovering most of the heat value from this before discharging the non-condensable gas. For each effect can excluding the final effect can, a condensate is collected between step (f) and step (e), and the liquid thus collected is passed to the effect can of the next stage and flushed. It is also possible to add a step of making it.

The present invention is particularly useful for desalination of water for producing fresh water from seawater, but for vaporizing black liquor discharged from the pulp and paper manufacturing process, or a liquid having a similar action. Can also be used.

According to another one of the embodiments of the present invention, an evaporator effect can is provided. The evaporator effect can includes the following parts. A horizontally extending vessel having a top, a bottom, a first end and a second end. One or more sets of plate heat exchange evaporating elements having an uneven surface that is long in the extending direction and that includes an internal passage and an external surface. In this case, the second set of
The plate heat exchange evaporation element having an uneven surface that is long in the extending direction also includes an internal passage and has an external surface. Means for introducing heated fluid into the interior passages of at least a second set of textured plate heat exchange evaporation elements. Means for attaching a first set and a second set of plate heat exchange evaporating elements on a textured surface, the means for attaching the first set above the second set in the horizontally long vessel. To evaporate the circulating fluid,
Means for introducing the circulating liquid to be evaporated near the top of the vessel so that the liquid drops in the form of a falling liquid film on the outer surfaces of the first and second evaporator elements. Droplet separation device installed in the tank. The process of drawing the evaporative circulation liquid from the tank through the droplet separation device. A means to collect the non-evaporated circulating fluid separately at the bottom of the tank. And the circulating liquid outlet from the bottom of the tank. The means for introducing the circulating liquid is a tray-like one having an open top and a bottom-bottom, which is mounted and mounted on the heat exchange element, and the bottom of the tray has a plurality of openings. It is preferable to include the following. Means may be provided to introduce preheated liquid into the internal passages of the designated (eg, first set) element and countercurrently flow with the fluid introduced into the internal passages of the second set of elements. ..

According to yet another embodiment of the present invention, a multi-stage evaporator is provided in which a plurality of effect cans are interconnected in a series of effect cans. The series of effect cans includes from the first, highest temperature effect can to the last, lowest temperature effect can. Each one of the effect cans in the series
It is as described above. For each effect can except the first effect can, the means for introducing the heating fluid is connected to the means for withdrawing the evaporative circulation liquid from the effect can in the preceding stage. Separation walls are also provided near the elements of each effect can, together with the bottom of the tank, to define the condensation chamber. An outlet for sending this "clean" condensate to a similar condensing chamber is provided to exit from the bottom of the condensing chamber and flush into the next stage of the effect can to exit the last effect can.

It is the main object of the present invention to use a multi-effect can to effect the effective evaporation of an evaporable liquid. This and other objects of the invention will be apparent upon a closer examination of the detailed description of the invention and the appended claims.

Now, the drawings will be described in detail. FIG. 1, generally designated by the reference numeral 10, is a multiple-effect evaporator according to the present invention. In this evaporation device, a horizontally long tank 11 is supported by a plurality of base legs 12, and many elements such as a heater 13 are included at one end thereof. For the embodiment actually shown in FIG. 1, the tank is, for example, about 400 feet long,
It contains 14 utility cans. However, the present invention is not limited to a specific number of effect cans, and a plurality of effect cans of 14 or less or more can be provided. Tank 11
Has a top 14, a bottom 15, and first and second ends 16, 17 respectively.

One of the simple forms that the evaporator 10 of the present invention can take is shown in FIG. In this figure, only three effect cans are shown. The first stage effect can (effect can 1) has the highest temperature and pressure, and the final stage effect can (effect can 3) has the lowest temperature and pressure. Each utility can contains one or more sets (at least one set) of evaporator elements. For example, each set includes a plate heat exchange evaporator element with a horizontally long asperity surface generally indicated by reference numeral 20 which is the first set and a horizontally long asperity generally indicated by reference numeral 21 which is the second set. A surface plate heat exchanger evaporator element is included. Each set of 20 and 21 can be formed using many uneven surface plate plates arranged in pairs. The pair of uneven surface plate plates are attached at intervals. For example, each set of 20 and 21 can be configured by collecting 200 pairs of the plate plates.

The textured surface plate plate itself is described in the above-mentioned US Pat. Nos. 3,211,219 and 3,512,239, the disclosures of each of which are already incorporated herein by reference. Quoted in the book. As such, each pair of plates has an interior passageway and an exterior surface. The first set 20 is arranged on top of the second set 21, and this second set 21 is supported and leveled by the means for attaching these sets. See, for example, support beam 22 in FIG. This is tank 1
1 is a typical structure for supporting the elements 20, 21 in one. Although in the following description, mostly only two sets of uneven surface plate evaporator elements are described, it is also possible to stack the plates on top of each other using three, four or more sets, Conversely, sometimes only one set is needed. See, for example, the third set 20 ', shown as utility cans 13 in FIGS. It is arranged between the first set and the second set.

Means are provided for introducing heating fluid to the internal passages of at least the second set of textured surface plate evaporator elements 21. For the first effect can, heating fluid is introduced into both sets 20, 21. Preferably,
Such means include, for example, for the first effect can, a conduit 23 extending to the outer wall 24 of the first effect can 1, and an internal pressure wall 25 is also provided to provide the remaining portion of the first effect can to the second effect. Separate from utility can. However, the internal passages in the 20 and 21 groups are different. On the bottom 15 of the tank of the first effect can, reference numeral 26
There is provided a condensate chamber generally indicated by. "beautiful"
The condensate outlet exits the condensing chamber 26. The condensed vapor components of the heating fluid introduced horizontally into the internal passage of the first effect can are collected in the chamber 26.

Each effect can, for example the first effect can, of the evaporator 10 of FIG. 2 also has means for introducing the circulating liquid to be evaporated near the top of the tank, the circulating liquid to be evaporated being the element 2
It falls on the outer surface of 0, 21 and a part of the circulating liquid is evaporated. The circulating liquid introducing means preferably comprises a vertically extending conduit section 29, which is a recirculation conduit 30 and a pump 31.
Is connected to the bottom of the tank 11 for circulating liquid and the like.
Pull out via the outlet 32 attached to the. The conduit 29 leads to a tray dispersion plate 33 at the top of the effect can, where a "head" or liquid level of liquid (schematically shown in FIGS. 2-5 and 7) is formed in the tray 33. The tray 33 typically has a depth of 1 inch or more. The liquid level in each effect can is the liquid level controller 3
Controlled by No. 4, this regulator operates a valve 35 in line 36 extending from the circulating fluid collecting bottom portion (or sump) 37 of each effect can.

Typically, the tray 33 has a horizontally extending bottom 38 (see FIG. 6) and is provided with means for defining a plurality of regularly spaced openings 39 in the plate. .. This opening enables the circulating liquid to form a uniform dispersed flow from the bottom 38 of the tray 33 and flow in a film form on the outer surfaces of the 20 and 21 sets of elements.

Specific details of the mechanism for supplying circulating fluid from conduit 29 are shown in FIGS. The vertically extending conduit 29 is connected to a tee 40. The tee includes a first end and a second end 41, 42, each end of which is a transverse conduit 4 respectively.
The outlet is open at the center of 3,44. Conduits 43, 4
The open end of No. 4 is an elbow 45, and this elbow is open to the approximately liquid surface of the tray 33. Supports 46 (see Figures 5 and 7)
Alternatively, the opening bottom end of the elbow 45 may be installed at a slight distance from the horizontal bottom 38 of the tray 33.

A part of the circulating liquid that falls on the surface of the set of elements 20 and 21 in the form of a film passes through a demister, that is, a droplet separator 48. The entrained droplets are removed from the vapor in the demister 48, and the droplets drop into the sump 37 along with the non-evaporated circulating fluid in addition to those condensed in the effect can. The steam itself then passes through outlet 49 and into the heated fluid inlet of the next effect can.

Non-condensable gas is also withdrawn from each effect can. The non-condensable gas passes through conduit 50 through orifice 51 or valve 52 to line 53. The line 53 is connected to a common pump (or steam ejector) 54 for all non-condensable gases, so that each effect can can be partially evacuated, so that the non-condensable gases reach the discharge location 55. become. As described with respect to FIGS. 3 and 4, the thermal value of the non-condensable gas is preferably largely recovered before it is actually disposed of.

The clean condensate from chamber 26 preferably passes through outlet 27 and into the clean condensate chamber 26 associated with the next effect can, as previously described. The liquid level in the condensate chamber is controlled by the liquid level controller 57. This regulator actuates the valve (or orifice) in line 27 to move (and control the flow rate) the condensate from one effect can to the next and to stop it. is there.

The inlet liquid to be evaporated is supplied from source 59. In the embodiment shown in FIG. 2, the source 59 is salt water, for example seawater. Seawater is the cooler 60 first
After cooling the condensate / produced water in the conduit 27 from the last effect can (effect can 3) and cooling the final product (demineralised water / fresh water), the water emerges in the conduit 62. From the cooler 60, the salt water passes through a conduit 62 into a designated set, for example, the inside of the first set 20 of the final effect can (effect can 3), and horizontally and from the first effect can to the final effect can. Flows countercurrently to the steam flow to. The salt water continues to flow through conduit 62 to the point where the conduit meets the first effect can recirculation conduit 30. After that, it becomes the evaporable inlet water for the entire evaporator 10. Of course, passing through the cooler 60 (which takes heat here),
The salt water is then preheated and more easily evaporated by passing through the first set of textured surface plate evaporator elements of all but the first effect can. Steam generated in an external tubular cylindrical preheater (not shown) from the previous effect can also be used to counterheat preheat the brine.

Another part of the salt water from the inlet 59 is the cooler 6
Enter 3. This heated inlet salt water then joins partly with line 62 via line 64 and the rest is returned as salt water 65 of normal salt concentration (for example to the sea). Cooler 63
The liquid cooled in (1) is the liquid (not the circulating liquid) extracted from the sump 37 of the final effect can via the line 36 from the final effect can. This liquid is concentrated salt water, and after part of the heat is recovered from it in the cooler 63, it is sent to the discharge place at 66.

In the embodiment of FIG. 2, a vapor compressor 67 is provided because new steam for the line 23 leading to the first effect can is not readily available. This vapor compressor uses electric power to raise the temperature and pressure of the vapor circulating from the vapor outlet 49 of the final stage effect can (third effect can) to the line 68.

Although the present invention is not limited to the particular temperature ranges and flow rates described, FIG. 2 exemplifies the temperatures of various fluids at different locations in the system. 3 and 4 show
A multi-effect evaporator 10 is shown where a low pressure steam 69 source is readily available. In this particular embodiment, 14 utility cans are used, but more or less may be used. In the structure of this embodiment, the same as the embodiment of FIG. 2 is indicated with the same reference numerals. The basic structure and operation of the apparatus of FIGS. 3 and 4 is generally the same as that of FIG. 2, with the following differences.

The liquid extracted from the clean condensate chamber 26 of the first effect can to the conduit 27 is not naturally flowed to the next effect can but is extracted by the pump 70 and the liquid level controller 71. Is sent to a source of clean condensate 72, controlled by. This liquid is eventually reheated (together with fresh make-up water) to a low pressure steam source 69.

A structure for recovering most of the heat value from the non-condensable gas in the line 53 is provided. This structure is in the form of a conventional steam ejector with a condenser 74, the outlet of which is connected via line 75 to a second steam ejector 76, which in turn It is connected to the second condenser 77. High temperature steam goes through line 78 and steam ejector 7
It is supplied to 3,76. The heat in the condensers 74, 76 is recovered by the inlet salt water 59 passing through the line 79.

After the final stage (14th) utility can, the vapor in line 49 enters surface condenser 80. The surface condenser 80 has largely the same structure as each individual utility can, with the difference that the inlet brine is the first set of uneven surface plate evaporator elements 2.
Salt water source 59 rather than passing through 0 internal passages
Is supplied to the tray 38 at the top of the can from a line 81 leading to a film flowing over the outer surface of the elements 20, 21. The condensate extracted from the surface condenser 80 to the line 27 flows to the cooler 60, where it is cooled and finally becomes the produced water 61. The circulating water in the line 36 withdrawn from the surface condenser 80 is mixed with the inlet brine in the heated line 83 (by the cooler 60) which is further heated in the heater / cooler 63. Then, it flows to the line 64 and enters the first set element 20 of the final effect can of the evaporator 10 by the driving force from the pump 84. In addition to heating the inlet liquid, a heater /
The cooler 63 cools the withdrawn and concentrated circulating liquid in the conduit 36 from the fourteenth effect can.

The circulating liquid and the extracted circulating liquid are taken out from the same outlet 32 by the pump 31. That is, the circulation line 30 and the circulating liquid withdrawal conduit 36 are connected together to the pump 31, as opposed to being connected separately in the embodiment of FIG.

Although the embodiments of FIGS. 3 and 4 have been described with reference to desalination of brine, the temperatures indicated are actually for black liquor evaporation. When actually used for desalination,
Low pressure steam from source 69 typically has a temperature of 212 °
And each effect can is not pressurized, but the effect can should be under varying degrees of vacuum.

In FIG. 7, an embodiment of the components that differs slightly from that shown in FIGS. 1-6 is shown. In FIG. 7, vapor from one effect can, after passing through the droplet separator 48, flows as a heating fluid to both heat exchange elements 20, 21 of the next effect can. Therefore, the non-condensable gas is 2
Is drawn into conduit 50 from the top of both sets 0,21,
Clean condensate is withdrawn from the bottom of both sets 20, 21 at its downstream end, rather than the upstream end (as shown in FIGS. 2, 3 and 4) of the utility can. In this embodiment, the evaporative liquid is not preheated (possibly no need for preheating ... because it is black liquor from some paper pulp process for example) and the preheating is an external tubular cylindrical heater (Fig. (Not shown).

The following method can be carried out step by step using the operating multi-effect evaporator 10. Although the present invention is described in terms of using two sets of evaporator elements, it should be understood that any number of sets (one or more sets) can be used.

Heated fluid from the source 69 or vapor compressor 67 is introduced horizontally into the internal passageways 23 of both the first and second sets 20, 21 of the first effect canister surface plate evaporator elements. , And the vaporized vapor is introduced into the internal passages of at least the second set 21 of all subsequent effect cans.
The circulating fluid pressure head is a tray 3 on top of the first set element of each effect can.
3 established to allow liquid to flow downwardly from this head to the outer surface of both sets 20, 21 of textured surface plate evaporator elements of each effect can. The evaporated portion of the circulating liquid is dedropped by the demister 48, and the droplets are separated from the vapor,
The separated liquid is circulated from each effect can to a liquid head (a tray 33) attached to the effect can by a pump and a circulation line 30. The steam in the line 49 that has passed through the demister 48 is supplied as heating fluid from each effect can to the effect can of the next stage (excluding the effect can of the last stage). In the last stage effect can, steam is sent to line 68 where its temperature is raised by vapor compressor 67 and to surface condenser 80 where it condenses and passes through line 27 to clean condensate. It may be taken out as. In either case, the clean condensate is withdrawn from the last stage utility can via line 27 to produce the final product (typically fresh water).

The product liquid coming from the last stage effect can or surface condenser via line 27 passes through a cooler 60 where the temperature is reduced below about 80 ° F. Non-condensed gas is withdrawn to conduit 53, preferably heat is recovered from this gas using steam ejectors 73, 76, condensers 74, 77 and similar equipment (see Figures 3 and 4). And Eventually, the product water flows to 61, the return salt water having the same concentration as the inlet salt water flows to 65, and the concentrated salt water flows to 66.

Therefore, according to the present invention, the method of evaporating the evaporable liquid is provided with a multiple-effect evaporator and a specific effect can for the multiple-effect evaporator, and it will be understood that each of them is advantageous. .. According to the present invention, the investment cost is saved as compared with the vertical uneven surface plate type evaporator, more uniform liquid dispersion, smaller vapor pressure loss between heating elements, as compared with the horizontal tube type evaporator, Better drop separation (less entrained drops) and / or higher heat transfer coefficient is obtained.

Since the present invention is shown and described herein only in what is presently considered to be the most practical and preferred embodiment,
It will be apparent to those skilled in the art that many modifications of the invention are possible within the scope of the invention. Therefore, the scope of the present invention should be construed to the full extent of the appended claims and to include all equivalent structures and methods.

[Brief description of drawings]

FIG. 1 is a side elevational view of an exemplary multi-effect evaporation tank of the present invention for a desalination evaporator.

FIG. 2 is a schematic system diagram of a triple-effect evaporator equipped with a vapor compressor, which can be used in the tank of FIG.

FIG. 3 is part of a schematic diagram for 14 effect evaporators using clean low pressure steam as the heating fluid.

FIG. 4 is the remainder of the schematic diagram for 14 effect evaporators using clean low pressure steam as the heating fluid.

5 is a schematic view of the end of the tank of FIG. 1 showing one can.

6 is a top view of a circulating liquid dispersion system of the evaporator of FIG.

FIG. 7 is a side schematic view showing in detail the interconnection between two effect cans, relating to a variant of the evaporator of FIGS. 3 and 4.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Evaporating device, 11 ... Vase whose horizontal direction is horizontal, 12 ... Support leg, 13 ... Heating element, 14 ... Top part, 15 ... Bottom part, 1
6, 41 ... First end, 17, 42 ... Second end, 20 ... Plate heat exchange with uneven surface whose longitudinal direction is horizontal First set of evaporator elements, 21 ... Plate heat exchange with uneven surface whose longitudinal direction is horizontal Second set of evaporator elements, 23 ... Heating fluid inlet, 26 ... Condensate chamber, 27, 36, 49, 53, 68, 75, 78, 7
9 ... Line, 29 ... Vertically extending conduit, 30 ... Circulation conduit, 31, 70 ... Pump 32, 49 ... Outlet, 33 ... Basin, 34, 57 ... Liquid level controller, 37 ... Liquid repair bottom part ( Sump), 38 ... bottom of basin plate, 39 ... opening, 43, 44 ... transverse conduit, 45 ... elbow, 48 ... droplet separating device (demister), 50, 62
... Conduit, 51 ... Orifice, 52 ... Valve, 54, 73, 7
6 ... Steam ejector, 55 ... Discharge location, 58 ... Valve (orifice), 59 ... Water source, 60, 63 ... Cooler, 6
1 ... Generated water, 65 ... Salt water with normal salt concentration, 66 ... Discharge place, 67 ... Vapor compressor, 69 ... Low pressure steam source, 72 ...
Clean condensate, 74, 77 ... Condenser, 80 ... Surface condenser

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiel Dei Infant United States, 12801-3686, Glens Falls, New York, Ritzy Center (no address) Kamayaya Incorporated

Claims (10)

[Claims] 1. At least one set of horizontally elongated textured surface plate heat exchanger evaporator elements (20) disposed in each effect can, each set of elements having a passageway inside and an outside. Using a multi-effect evaporator (10) having heat exchange surfaces and effect cans connected in series, including a first, highest temperature effect can and a final, lowest temperature effect can. In a method of evaporating an evaporable liquid, (a) a first effect can element (2
0) introducing a horizontally flowing heating fluid into the inner passages and into the inner passages of all subsequent stages of the effect can, (b) to be vaporized to the top of the first set of elements of each effect can. A step of providing a circulating liquid head of the liquid, (c) a step of flowing the liquid downward from the liquid head to the outer surface of each effect can, (d) extracting the vapor of the evaporative circulating liquid from each effect can, and forming droplets therefrom The step of removing and separating the entrained liquid from the vapor, (e) the step of recirculating the circulating liquid that has not evaporated to the liquid head attached to the effect can, (f) the vapor extracted from each effect can, It includes the steps of horizontally supplying the liquid supplied to the above step (a) to the effect cans of the next stage excluding the final stage, and (g) removing the clean condensate from the effect cans of the final stage. Evaporable liquid using a multi-effect evaporator characterized by: The method of evaporation. 2. The at least one set of evaporator elements comprises at least first and second set elements (20, 21),
The method of claim 1 further characterized in that for each effect can, the first set is disposed so as to overlap the top of the second set, and a circulating head is provided at the top of the first effect can of each set. the method of. 3. The method of claim 1 further characterized in that step (a) is performed on the first effect can by introducing steam into the first effect can. 4. A step (h) of preheating the liquid to be evaporated before introducing it into the liquid head of the first effect can, which preheating is applied to all the effects except the first-stage effect can. By passing this liquid through the internal passages of the first set of elements of the can, which is countercurrent to the vapor flowing through the second set of internal passages from the first effect can to the final effect can. The method of claim 2, wherein the method comprises flowing. 5. Removing non-condensable gas from each effect can,
The method according to claim 1, further comprising the step (j) of recovering most of the heat value from the non-condensable gas before discharging the non-condensable gas. 6. The method according to claim 1, further characterized in that the liquid to be evaporated is black liquor discharged from the paper pulp manufacturing process or salt water. 7. An evaporative effect can comprising a horizontally extending vessel (11) having a top (14), a bottom (15), a first end (16) and a second end (17), wherein an internal passage is provided. A first set of plate heat exchange evaporative elements having an uneven surface that is long in the extending direction and that has an outer surface, and means (23) for introducing a heating fluid into the internal passages of the plate heat exchange evaporative elements having the uneven surface, Means for mounting the first set of plate heat exchange evaporation elements on a textured surface, the means for arranging the elements in the vessel so that their longitudinal directions are horizontal (2
2) Means for introducing the circulating liquid to be evaporated near the top of the tank so that the liquid falls in the form of a falling liquid film on the outer surface of the element to evaporate the circulating liquid to some extent (4).
1, 29, 33, etc.), a droplet separating device (48) mounted in the tank, a means (for example, 25) for extracting the evaporated circulating liquid from the tank through the droplet separating device, and a circulating liquid that has not evaporated. Means for collecting the above in the tank at the bottom (2
6) and a horizontal evaporation effect can characterized by a circulating liquid outlet (36) from the bottom of the tank. 8. An internal passage is included and has an external surface,
A second set of plate heat exchange evaporating elements having a textured surface elongated in the extending direction (the first set is attached to the top of the second set and the second set of elements is horizontal in its longitudinal direction). 8. An evaporative effect can according to claim 7, characterized in that said heating fluid introducing means introduces heating fluid into the internal passages of said first and second sets of elements. 9. A basin plate (33) having an open top and a bottom bottom mounted on the heat exchange element, the means for introducing a circulating liquid, and a bottom part of the basin plate (33). 38)
A liquid to be preheated to the internal passages of the first set of elements, characterized in that it comprises means for defining an opening uniformly distributed in the bottom of the tray with a plurality of openings (39). 9. An evaporative effect can according to claim 8 further comprising means for introducing and allowing countercurrent flow with fluid introduced into the second set of internal passages of the element. 10. A multi-stage evaporator comprising a plurality of effect cans interconnected to a series of effect cans from a first, highest temperature effect can to a last, lowest temperature effect can. A horizontally extending vessel (1) having a top (14), a bottom (15), a first end (16) and a second end (17).
1); a first set of plate heat exchanger evaporator elements (20) having internal passages and having an outer surface and having a textured surface that is long in the extending direction; extending direction having inner passages and having an outer surface A second set of plate heat exchange evaporator elements (21) with a long rough surface; means for introducing heating fluid into at least the internal passages of said second set of plate heat exchanger evaporator elements with a rough surface (eg 23) So that the first set and the second set of plate heat exchange evaporating elements having an uneven surface are placed in the tank with the longitudinal direction thereof horizontal and the first set placed on the second set. Means (22) for attaching to said means for introducing the circulating liquid to be vaporized near the top of said vessel, so that the liquid falls into a falling film on the outer surfaces of said first and second sets of elements, Means (31, 2) for evaporating the circulating liquid to some extent
9, 33, etc.); Droplet separating device (48) mounted in the tank; Means for extracting the circulating liquid evaporated from the tank through the droplet separating device (for example, 25); Circulating liquid not evaporated And means for collecting the liquid separated by the droplet separator at the bottom of the tank (26); and each effect can in series characterized by a circulating liquid outlet (36) from the bottom of the tank And, for each effect can except the first effect can, the means for introducing a heating fluid is connected to the means for extracting the circulating liquid evaporated from the effect can of the preceding stage.