KR20100016519A - Desalination apparatus and method of desalination - Google Patents

Abstract

A desalination apparatus, and method of desalination, with which condensed water can be efficiently obtained while preventing scale deposition. Desalination apparatus (1) is one equipped with multiple-effect evaporation unit (2) having multiple evaporators capable of not only feeding a water to be treated to the external surface of heat transfer tube adapted to cause steam to pass through the interior thereof to thereby produce steam and concentrated water from the water but also forming condensed water through condensation of steam in the heat transfer tube, the multiple evaporators (2a to 2t) interconnected so that the steam produced by anterior-stage evaporator is led into the interior of heat transfer tube of posterior-stage evaporator as heat source, wherein the multiple evaporators (2a to 2t) are divided into multiple evaporator groups (3A to 3E) along the direction from the anterior stage side to the posterior stage side, and wherein there are provided scale component removing means (5) for removing at least portion of the scale component in raw water to thereby produce descaled water; mixed water feeding means (6) for feeding a mixed water consisting of a mixture of raw water and descaled water as a water to be treated to the heat transfer tube of each of the evaporators (2a to 2d) of the first evaporator group (3A) disposed on the most anterior stage side among the multiple evaporator groups (3A to 3E); and dilution water feeding means (7) for feeding a dilution water consisting of a mixture of concentrated water and mixed water as a water to be treated to the heat transfer tube of each of the evaporators (2e to 2h) of the second evaporator group (3B) disposed on one low temperature side among the first evaporator group (3A).

Description

Desalination Apparatus and Desalination Method {DESALINATION APPARATUS AND METHOD OF DESALINATION}

The present invention relates to the construction of a desalination apparatus for generating fresh water.

As a method of producing beverage water from seawater, for example, methods proposed in Patent Documents 1 and 2 are known. In these methods, the drinking condensate removes the scale component from the raw seawater using a nanofiltration membrane, mixes the seawater from which the scale component has been removed, and the original seawater, and supplies the mixed water. It is produced by distilling the mixed water by feeding it to a multi-effect evaporator as water.

Patent Document 1: Japanese Patent Laid-Open No. 2003-507183

Patent Document 2: King Abdulaziz City for Science and Technology, Saudi Arabia, Patent # 1000; 30/7/2006.

Problems to be solved by the present invention

Scale components such as calcium sulfate contained in the raw water to be treated by being fed to the multi-effect evaporator are easily precipitated from the surface of the heat transfer tubes in the evaporator when the temperature is high and thus the solubility is low. In order to prevent precipitation of the calcium sulfate scale, it is necessary to arrange such that the maximum operating temperature of the evaporator and the concentrated magnification of the untreated water supplied are as low as possible. This has a problem in that it is difficult to effectively produce pure water for drinking and the like.

In the method of producing fresh water as proposed in Patent Document # 1, precipitation of the scale inside the evaporator cannot be completely prevented. As a result, the thermal efficiency of the evaporator is deteriorated, and the condensed water for drinking cannot be produced efficiently. On the other hand, one of the claims of Patent Document # 2 relates to a desalination system of multi-effect destillation (MED) or Vapor Compression Distillation (VCD) using nanofiltration pretreatment without specific technology of desalination system. It is about.

The present invention is to provide a specific configuration of a multi-effect desalination apparatus based on the system claimed in Patent Document # 2 that can efficiently generate condensate and prevent precipitation of scale.

Means to solve the problem

An object of the present invention described above is a multi-effect evaporator having a plurality of evaporation tube; And a plurality of heat transfer tubes through which steam passes, and by supplying the feed water to the outer surfaces of the plurality of heat transfer tubes, steam and concentrated brine are generated from the feed water, and the steam generated in the preceding evaporation tube is transferred to the next evaporation tube. The plurality of evaporation tubes are connected to each other in such a way that the vapor can be used as a heat source in the next evaporation tube, and the plurality of evaporation tubes are arranged from upstream to downstream, respectively. by a desalination apparatus divided into groups). The desalination apparatus includes: scale component removing means for removing at least a portion of scale components contained in raw raw water to produce scale component removing water; A heat transfer tube of each evaporation tube of the first evaporation tube group positioned at the most upstream in the plurality of evaporation tube groups, the mixed water supply means for supplying a mixed water of raw raw water and scale component removal water as supply water; A dilution water provided by mixing the concentrated brine and the mixed water mixed by the mixed water supply means is supplied to the heat transfer tubes of the respective evaporating tubes of the second evaporating tube group located on the low temperature side after the first evaporating tube group. Dilution water supply means for supplying as water is further provided.

In this desalination apparatus, the dilution water supply means is configured to supply the dilution water provided by mixing the concentrated brine generated in the first evaporation tube group and the mixed water to the heat transfer tubes of each evaporation tube of the second evaporation tube group. It is preferable to be.

Each of the evaporation tube groups other than the first and second evaporation tube groups is supplied with a heat transfer tube of each evaporation tube, and concentrated brine generated in any one of a plurality of evaporation tube groups other than the first and second evaporation tube groups. It is preferable that a concentrated brine supply means for supplying water is provided.

Further, the dilution water supply means may evaporate the dilution water provided by mixing concentrated brine produced by flash evaporation, concentrated brine produced in the second evaporation tube group, and mixed water provided by the mixed water supply means. It is preferably configured to feed into the heat transfer tubes of each evaporation tube of the tube group.

The scale component removing means is preferably a nanofiltration membrane device.

The object of the present invention described above includes a plurality of evaporation tubes and a plurality of heat transfer tubes through which steam passes, and by supplying supply water to the outer surfaces of the plurality of heat transfer tubes, steam and concentrated brine are generated from the supply water. The plurality of evaporation tubes are connected to each other in such a way that steam generated in an evaporation tube is introduced into a heat transfer tube in a next evaporation tube so that steam can be used as a heat source in the next evaporation tube, and the plurality of evaporation tubes are upstream. It can be achieved by a method for generating fresh water using a desalination apparatus divided into a plurality of groups each arranged from downstream to downstream. The fresh water generating method includes a scale component removing step of removing at least a portion of scale components included in raw raw water to produce scale component removing water; A mixed water supplying step of supplying mixed water of raw raw water and scale component removing water as supply water to a heat transfer tube of each evaporating tube of the first evaporating tube group positioned at the most upstream in the plurality of evaporating tube groups; A heat transfer tube of each evaporation tube of the second evaporation tube group located on the low temperature side after the first evaporation tube group, wherein dilution water provided by mixing the concentrated brine and the mixed water provided in the mixed water supplying step is supplied as supply water. Dilution water supplying step of supplying.

Effects of the Invention

The present invention provides a desalination apparatus and a method of generating freshwater that can efficiently generate condensate by operating a desalination apparatus at a high concentration at a high concentration ratio while preventing precipitation of scale.

1 is a schematic view showing a desalination apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram schematically showing an evaporation tube of the desalination device shown in FIG. 1. FIG.

3 is a configuration diagram schematically showing a modification of the desalination apparatus shown in FIG. 1.

4 is a configuration diagram schematically showing another modified example of the desalination device illustrated in FIG. 1.

FIG. 5 is a configuration diagram schematically showing another modified example of the desalination device shown in FIG. 1. FIG.

FIG. 6 is a configuration diagram schematically showing a modification of the desalination apparatus shown in FIG. 6. FIG.

FIG. 7 is a flowchart when the mixed water is twice concentrated using the desalination apparatus shown in FIG. 1. FIG.

FIG. 8 is a flowchart when the mixed water is concentrated three times using the desalination apparatus shown in FIG. 1. FIG.

FIG. 9 is a flowchart when the mixed water is concentrated twice by supplying the mixed water to the third evaporation tube group. FIG.

10 is a flowchart when the mixed water is concentrated three times by supplying the mixed water to the third evaporation tube group.

11 is a flowchart when the mixed water is concentrated twice by supplying the mixed water to the fifth evaporation tube group.

12 is a flowchart when the mixed water is concentrated three times by supplying the mixed water to the fifth evaporation tube group.

Explanation of Reference Marks

1: desalination device

2: evaporator

2a to 2t: evaporation tube

3A: first evaporator group

3B: second evaporator group

3C: third evaporator tube group

3D: fourth evaporator tube group

3E: Fifth Evaporator Group

4: tank

5: scale component removal means (nanofiltration membrane device)

6: Mixed water supply means

7: dilution water supply means

8: condenser

9: concentrated brine supply means

Hereinafter, a desalination apparatus according to the present invention will be described with reference to the accompanying drawings. 1 is a schematic configuration diagram of a desalination apparatus according to an embodiment of the present invention, Figure 2 is a schematic configuration diagram of an evaporation tube of the desalination apparatus. It can be seen that each component in the figures is partially enlarged or reduced in order to facilitate understanding of the configuration, and thus is not shown in actual size.

As shown in FIG. 1, the desalination apparatus 1 includes a tank 4 for storing raw raw water such as seawater, a nanofiltration membrane 5 for removing scale components contained in raw raw water, Supply steam duct 10 for introducing hot driving steam generated by the multi-effect evaporator 2, a boiler (not shown), etc. into the evaporator 2, supplying the mixed water supply means 6, diluting water Means 7 and a condenser 8 are provided.

The nanofiltration membrane device 5 removes at least a portion of scale components such as calcium sulfate (CaSO ₄ ) contained in untreated raw water such as seawater stored in the tank 4 to generate scale component removal water, and the condenser It is a scale component removal means arrange | positioned between 8 and the tank 4. As shown in FIG. The nanofiltration membrane device 5 mainly has a function of removing divalent ions. In particular, the nanofiltration membrane apparatus 5 which can remove a sulfate ion effectively is preferable. Such a device makes it possible to generate scale component removal water from which the scale component is effectively removed from raw raw water (sea water) supplied to the nanofiltration membrane device.

The evaporator 2 is constituted by connecting a plurality of evaporating tubes 2a to 2t in series, and as shown in FIG. 2, each of the evaporating tubes is a hermetic evaporation chamber 21 and an indirect heater 22. And a spray nozzle 23 for spraying the feed water. The inner bottom of the evaporation chamber 21 receives supply water sprayed through the spray nozzle 23 to the outer surface of the heat transfer tube 221 of the indirect heater 22 due to heat exchange performed by the heat transfer tube 221. It functions as a concentrated brine reservoir 24 that stores a portion of the concentrated brine produced by evaporation. In the inner bottom of the evaporation chamber 21, the concentrated brine stored in the concentrated brine inlet 26a and the concentrated brine reservoir 24 for introducing the concentrated brine generated in the preceding evaporation tube into the next subsequent effect. Further provided is a brine outlet 26b for draining. A steam outlet 25a for discharging steam generated on the outer surface of the heat transfer tube 221 by heat exchange with the heat transfer tube 221 is provided at the top of the evaporation chamber 21.

The indirect heater 22 includes a plurality of heat transfer tubes 221 disposed in the evaporation chamber 21, a first header 222 and a second header attached to one end of the plurality of heat transfer tubes 221, respectively. 223). The first header 222 has a steam inlet 25b for introducing steam into the heat transfer tube 221 and a condensate inlet 27a for introducing condensate generated in the heat transfer tube 221 in another evaporation tube. Is provided. The second header 223 is provided with a condensate outlet 27b for discharging the condensate generated in the heat transfer tube 221 by heat exchange with the heat transfer tube 221. When the amount of condensate stored in the first header 222 exceeds a predetermined amount, the condensate is supplied to the second header 223 through the inner side of the lowermost heat transfer tube 221.

The spray nozzle 23 disposed on the indirect heater 22 is a means for spraying feed water onto the outer surface of the heat transfer tube 221.

As shown in FIG. 1, the steam outlet 25a in the upstream evaporator tube is fed through the steam duct 25 so that the steam generated in the upstream evaporator tube is supplied as a heat source to the heat transfer tube 221 in the intermediate downstream evaporator tube. The evaporation tubes are connected to each other in a manner that is connected to the vapor inlet 25b in the downstream evaporation tube. The brine outlet 26b in the upstream evaporator is connected to the brine inlet 26a in the intermediate downstream evaporator via a brine feed duct 26, produced in the upstream evaporator and then concentrated brine reservoir ( The concentrated brine stored in 24 is fed to the concentrated brine reservoir 24 in the intermediate downstream evaporator. The condensate outlet 27b in the upstream evaporator is connected to the condensate inlet 27a in the intermediate downstream evaporator via a condensate duct 27, produced in the heat transfer tube 221 in the upstream evaporator, and then the second Condensed water stored in the header 223 is supplied to the first header 222 of the indirect heater 22 in the intermediate downstream evaporator.

The driving steam duct 10 for introducing the driving steam generated by the boiler or the like is connected to the steam inlet 25b of the first header 222 of the indirect heater 22 in the uppermost evaporating tube 2a. In the uppermost evaporation tube 2a, the condensate inlet 27a and the concentrated brine inlet 26a are unnecessary.

A steam discharge duct 51 for introducing steam into the condenser 8 to be described later is connected to the steam outlet 25a of the second header 223 of the indirect heater 22 in the downstream evaporation tube 2p. , The condensate discharge duct 53 for discharging the condensate to the outside is connected to the condensate outlet (27b). Further, the concentrated brine discharge duct 54 for discharging the stored concentrated brine to the outside is connected to the concentrated brine outlet 26b formed at the bottom of the evaporation chamber 21.

The plurality of evaporation tubes 2a to 2t in the evaporator 2 configured as described above are divided into a plurality of groups arranged downstream from the upstream. More specifically, the plurality of evaporator tubes are arranged in order from upstream to downstream, the first evaporator tube group (3A), the first evaporator tube group (3B), and the third evaporator tube group (3C). The fourth evaporator group 3D, and the fifth evaporator group 3E. Each of the evaporation tube groups 3A to 3E is configured to have four evaporation tubes. The number of evaporation tubes of each of the evaporation tube groups 3A to 3E may be appropriately selected according to design conditions and the like. In this structure, since the driving steam is introduced into the evaporation tube 2a disposed at the most upstream in the first evaporation tube group 3A, the operating temperature in the first evaporation tube group 3A is among the five groups. The highest. The operating temperature decreases gradually from the second evaporator group 3B to the fifth evaporator group 3E. The operating temperature in the evaporator tubes of each evaporator group decreases from upstream to downstream.

The mixed water supply means 6 uses the nanofiltration membrane apparatus 5 to remove mixed water of scale component removal water obtained by removing at least a portion of scale components from raw raw water and raw water supplied from the tank 4, As the treated water to be treated, it is supplied to the heat transfer tube in the evaporation tube of the first evaporation tube group 3A disposed at the most upstream in the plurality of evaporation tube groups 3A to 3E. This mixed water supply means 6 is connected to the feed pump (not shown) and the mixed water supply duct 61 connected to each of the spray nozzles 23 of the evaporating pipes 2a to 2d of the first evaporating pipe group 3A. Equipped. A portion of the scale component removal water supply duct 61 is configured in such a manner as to pass through a cooling unit (not shown) provided inside the condensation device 8, and the scale component passes through the scale component removal water supply duct 61. The removal water functions as a coolant to condense the steam supplied to the condensation device 8.

The dilution water supply means 7 is concentrated brine produced in the second evaporator tube group 3B disposed adjacent to the first evaporator tube group 3A on the low temperature side, and the evaporation of the second evaporator tube group 3B. The dilution water provided as the treated water to be treated is supplied by mixing the mixed water provided by the mixed water supply means to the heat transfer tube in the pipes 2e to 2h. More specifically, the dilution water supply means 7 includes concentrated brine stored in the evaporation tube 2h disposed at the downstream of the second evaporation tube group 3B and the evaporation tube 2e of the second evaporation tube group 3B. To 2h) each of the concentrated brine ducts 71 introduced into the spray nozzles 23 and the concentrated brine ducts 71 are connected to the mixed water supply duct 61 and supplied through the mixed water supply means 6. A mixed water discharge duct 72 for introducing a portion of the mixed water into the concentrated brine duct 71, and a feed pump (not shown) are provided. This configuration can reduce the concentration of scale components such as calcium sulfate in the treated water to be supplied to the heat transfer tubes 221 in the evaporation tubes 2e to 2h of the second evaporation tube group 3B.

Each of the evaporation tube groups 3C, 3D, and 3E other than the first evaporation tube group 3A and the second evaporation tube group 3B is a first evaporation tube group 3A and a second evaporation tube group 3B. Concentrated brine supply means for supplying the concentrated brine produced in any other evaporation tube group as the treated water to be treated to each evaporation tube of each evaporation tube group (3C, 3D, 3E). In the embodiment shown in FIG. 1, the concentrated brine supply means 9 in the third evaporation tube group 3C is stored in the evaporation tube 21 disposed on the downstream side in the third evaporation tube group 3C. The concentrated brine is configured to be supplied as treated water to be treated to the evaporation tubes 2i to 2l of the third evaporation tube group 3C. The concentrated brine supply means 9 in the fourth evaporation tube group 3D is configured to supply concentrated brine stored in the evaporation tube 2p disposed on the downstream side of the fourth evaporation tube group 3D in the fourth evaporation tube group. It is configured to supply as treated water to be treated to the evaporation tubes 2m to 2p of 3D. The concentrated brine supply means 9 in the fifth evaporation tube group 3E receives concentrated brine stored in the evaporation tube 2t disposed on the downstream side of the fifth evaporation tube group 3E. It is configured to supply the treated water to be treated to the evaporation tubes 2q to 2t of 3E). Each concentrated brine supply means 9 is a concentrated brine supply duct 91 for introducing concentrated brine into a spray nozzle 23 of each of the evaporation tubes of the feed pump (not shown) and the evaporation tube groups 3C, 3D, and 3E. It is provided.

The condenser 8 uses the mixed water passing through the mixed water supply duct 61 for the steam discharged from the discharge portion 25a of the evaporation tube 2t disposed on the downstream side of the multi-effect evaporator 2. Indirectly cooled to produce condensate. The generated condensate is discharged to the outside through the duct 52.

Hereinafter, a method of generating condensed water for use as drinking water using the desalination apparatus 1 having the above-described configuration will be described. First, the driving steam generated by the boiler or the like is supplied to the evaporator 2 through the driving steam duct 10, and then the mixed water obtained by mixing the scale component removal water and the raw raw water is supplied to the mixed water supply means 6. By the evaporator 2.

The driving steam supplied to the evaporator 2 is introduced into the heat transfer tube 221 of the evaporator tube 2a disposed on the most upstream side in the first evaporator tube group 3A. The mixed water supplied by the mixed water supply means 6 is distributed to the spray nozzles 23 of each of the evaporating tubes 2a to 2d of the first evaporating tube group 3A, and the evaporating tubes 2a to 2d Is sprayed as treated water to be treated on the outer surface of the heat transfer tube 221.

The mixed water sprayed onto the outer surface of the heat transfer tube 221 of the most upstream evaporator tube 2a in the first evaporator tube group 3A exchanges heat with the driving vapor passing through the inside of the heat transfer tube 221. A portion of the mixed water evaporates and the residual vapor is introduced as a heat source into the heat transfer tube 221 of the evaporation tube 2b in the intermediate downstream evaporation tube. In addition, the mixed water not evaporated at the outer surface of the heat transfer tube 221 is concentrated brine with increased concentrations of salinity and scale components. The remaining concentrated brine flows down along the outer surface of the heat transfer tube 221 and is then stored at the bottom of the evaporation chamber 21. Next, the concentrated brine is fed from the concentrated brine outlet 26b to the intermediate downstream evaporator 2b via the concentrated brine supply duct 26. In addition, the driving steam passing through the inside of the heat transfer tube 221 is converted into condensate by heat exchange with the mixed water sprayed on the outer surface of the heat transfer tube 221. The condensate is stored in the second header 223 of the indirect heater 22 and is introduced into the first header 222 of the indirect heater 22 of the intermediate downstream evaporator 2b via the condensate duct 27. do.

Mixing sprayed onto the outer surface of the heat transfer tube 221 from the spray nozzle 23 in the evaporating tube 2b disposed next to the most upstream evaporating tube 2a on the downstream side of the first evaporating tube group 3A. Heat exchange occurs between the water and steam generated in the intermediate upstream evaporator tube 2a and passing through the inside of the heat transfer tube 221. This process produces steam and concentrated brine and also produces condensate in the heat transfer tube 221. This same process is carried out continuously in the evaporation tubes 2c and 2d of the first evaporation tube group 3A.

The operation of the second evaporation tube group 3B will be described below. The dilution water provided by mixing the concentrated brine stored in the evaporation tube 2h disposed downstream of the second evaporation tube group 3B and the mixed water introduced through the mixed water mixing means 33 is a second evaporation tube. It is sprayed as treated water to be treated on the outer surface of the heat transfer tube 221 of the evaporation tubes 2e to 2h in the group 3B. In the evaporating tube 2e disposed on the uppermost side in the second evaporating tube group 3B, the dilution water sprayed on the heat transfer tube 221 and the lowest downstream in the first evaporating tube group 3A. Heat exchange takes place between the vapor generated in the evaporation tube 2d and passing through the inside of the heat transfer tube 221. This process not only produces steam and concentrated brine, but also condensate in the heat transfer tubes 221. Dilution sprayed from the spray nozzle 23 onto the outer surface of the heat transfer tube 221 in the evaporator tube 2f disposed downstream of the most upstream evaporator tube 2e in the second evaporator tube group 3B. Heat exchange occurs between the water and steam generated in the intermediate upstream evaporation tube 2e and passing through the inside of the heat transfer tube 221. This process not only produces steam and concentrated brine, but also condensate in the heat transfer tube 221. This same process is carried out continuously in the evaporation tubes 2g and 2h following the second evaporation tube group 3B.

The concentrated brine stored in the evaporation tube 21 positioned downstream from the third evaporation tube group 3C is the outer surface of the heat transfer tube 221 of the evaporation tubes 2i to 2l in the third evaporation tube group 3C. Sprayed up. In the most upstream evaporation tube 2i in the third evaporation tube group 3C, the concentrated brine sprayed on the heat transfer tube 221 and the evaporation disposed on the most downstream side of the second evaporation tube group 3B. Heat exchange occurs between the steam generated in the tube 2h and passing through the inside of the heat transfer tube 221. This process not only produces concentrated brine with increased steam and salinity, but also condensate in the heat transfer tube 221. In the evaporating tube 2j disposed on the middle downstream side of the most upstream evaporating tube 2i in the third evaporating tube group 3C, spraying from the spray nozzle 23 is performed on the outer surface of the heat transfer tube 221. Heat exchange between the concentrated brine and the steam produced in the intermediate upstream evaporation tube 2i and passing through the inside of the heat transfer tube 221. This process not only produces steam and concentrated brine, but also condensate in the heat transfer tube 221. This same process is carried out continuously in the other evaporation tubes 2k and 2l of the third evaporation tube group 3C.

Also, this same process as in the third evaporator tube group 3C is repeated in the fourth and fourth evaporator tube groups 3D and 3E.

The condensed water produced in the heat transfer tube 221 in the evaporator tubes 2a to 2t of the evaporator 2 is continuously introduced into the downstream evaporator tube through the condensate duct 27. Finally, the condensate is discharged from the condensate outlet (2) of the evaporator tube 2t (lowest evaporator tube in the fifth evaporator group 3E) disposed downstream of the evaporator 2 via the condensate discharge duct 53. 27b). In addition, the steam formed on the surface of the heat transfer tube 221 of the downstream evaporator tube 2t in the evaporator 2 is introduced into the condenser 8 through the steam discharge duct 51 and converted into condensed water, It is discharged through the duct 52. The condensed water discharged from the evaporator 2 and the condensed water discharged from the condenser 8 may be used as treated water for other fields in various industries such as drinking water, process water, and electronics.

Some of the concentrated brine stored in the downstream evaporator tube 2t in the evaporator 2 is discharged from the concentrated brine outlet 26b to the outside through the concentrated brine discharge duct 54.

The desalination apparatus 1 of this embodiment has the highest operating temperature of the first evaporation tube group 3A among all the evaporation tube groups in which scale components such as calcium sulfate are easily precipitated during the evaporation-condensation process for obtaining condensate. In the evaporation tubes 2a to 2d, the mixed water having the lowest scale component concentration is supplied as the treated water to be treated. This reliably prevents the deposition of scale on the heat transfer tubes 221 and the like in the evaporation tubes 2a to 2d.

In addition, the desalination apparatus 1 is a dilution having a low scale component concentration to the evaporation tubes 2e to 2h of the second evaporation tube group 3B having the second highest operating temperature after the first evaporation tube group 3A. Since the water is configured to be supplied, precipitation of scale on the surface of the heat transfer tube or the like of the evaporation tubes 2e to 2h of the second evaporation tube group 3B can be reliably prevented.

By reliably preventing the deposition of scale on the surface of the heat transfer tube 22! Of the evaporation tube, the decrease in the heat exchange efficiency in the heat transfer tube 221 can be prevented. This makes it possible to efficiently produce condensate for drinking and other applications.

Since precipitation of the scale can be prevented, it is possible to further increase the temperature of the driving steam supplied to the evaporator 2 to operate the evaporation tubes 2a to 2t even under higher operating temperature conditions and / or higher concentration conditions. have. This makes it possible to efficiently generate a large amount of condensate. In addition, since the operating temperature in the evaporation tubes 2a to 2t can be increased, the specific volume of vapor in the evaporation tubes 2a to 2t can be reduced. Therefore, the volume of the evaporation tubes 2a to 2t can be reduced, and thus the desalination apparatus 1 can be miniaturized.

Part of the treated water that is treated in the evaporation-concentration process in the evaporation tubes 2e to 2h of the second evaporation tube group 3B is formed of untreated raw water and scale component removal water supplied through the mixed water discharge duct 72. It is mixed water. Therefore, the flow rate of the mixed water supplied to the evaporation tubes 2a to 2d of the first evaporation tube group 3A is such that the process in the evaporation tubes 2a to 2d can be performed in the most efficient manner. It can be maintained as, it is possible to increase the flow rate of the mixed water treated in the desalination process in the entire desalination device (1). As a result, condensate for drinking and other applications can be efficiently produced from a large amount of mixed water.

Although the embodiments of the desalination device 1 according to the present invention have been described above, the specific configuration of the present invention is not limited to these embodiments. In the present embodiment, the dilution water supply stage 7 removes the dilution water prepared by mixing the concentrated brine produced in the second evaporation tube group 3B and the mixed water introduced through the mixed water discharge duct 72. It is configured to feed into a heat transfer tube of two evaporator tube groups. However, for example, as shown in FIG. 3, the dilution water provided by mixing the concentrated brine produced in the first evaporation tube group and the mixed water supplied through the mixed water discharge duct 72 may be provided to the second evaporation tube group 3B. It can be configured to be supplied to the heat transfer tube of the evaporation tube (2e to 2h) in the.

As shown in FIG. 1, this embodiment shows that a portion of the concentrated brine produced and stored in the evaporation tube groups 3C, 3D, 3E provided with the concentrated brine supply means 9 is treated via the concentrated brine supply means 9. It is configured to be supplied to the evaporation tubes of the evaporation tube groups 3C, 3D and 3E as treated water. However, the present invention is not limited to this configuration. For example, as shown in FIG. 3, the concentrated brine supply means 9 is provided with an evaporator tube group 3B immediately upstream to the evaporator tube groups 3C, 3D, 3E provided with the concentrated brine supply means 9. , 3D, 3D) may be configured to supply a portion of the concentrated brine generated and stored in the downstream evaporation tubes 2h, 2l, 2p to each evaporation tube.

The present embodiment is configured in such a manner that dilution water provided by mixing concentrated brine and mixed water is supplied only to the evaporation tubes 2e to 2h of the second evaporation tube group 3B, but the configuration of the present invention is not limited thereto. For example, if there is a concern that a scale, such as calcium sulfate, may occur in the evaporation tubes 2i to 2l of the third evaporation tube group 3C, the dilution water provided by mixing concentrated brine and mixed water may provide a third evaporation tube group ( The structure supplied to the evaporation tubes 2i-2l of 3C) can be employ | adopted.

In this embodiment, for example, as shown in FIG. 4, a configuration in which the preheating means 100 is provided as a means for heating the mixed water passing through the mixed water supply duct 61 may be employed. FIG. 4 shows a configuration in which the mixed water is heated by using steam generated in the evaporation tubes 2e to 2t in the second evaporation tube groups 3B to 5E as the heat source. This configuration can effectively raise the temperature of the mixed water sprayed on the surface of the heat transfer tubes 221 of the evaporating tubes 2a to 2d in the first evaporating tube group 3A, and the mixed water and the evaporating tube ( It is possible to reduce the temperature difference between the driving steam passing through the heat transfer tubes 22! Of 2a to 2d). This increases the amount of steam generated in the evaporation tubes 2a to 2d, and as a result can efficiently produce condensate from the mixed water.

In addition, the present embodiment provides a reverse osmosis membrane apparatus (RO apparatus) such that the scale component removal water passing through the nanofiltration membrane apparatus 5 is supplied to the reverse osmosis membrane apparatus (RO apparatus) as supply water to generate pure water. Mixed water is produced by mixing RO brine produced by the reverse osmosis membrane apparatus (RO apparatus) with untreated raw water, and then the mixed water is evaporated in the first evaporation tube group 3A as treated water to be treated. It may have a configuration supplied to the pipe (2a to 2d). This can not only generate drinking water for drinking, etc. from the reverse osmosis membrane device, but also achieve efficient generation of fresh water. If necessary, an additional mixed solution of seawater and RO brine treated by the nanofiltration membrane may be supplied to the evaporation tubes 2a to 2d of the first evaporation tube group 3A.

In the embodiment shown in FIG. 1, if the pressure of the driving steam passing through the driving steam duct 10 is high enough to compress the steam produced in any evaporation tube of the evaporator 2, A steam recompression ejector 101 may be provided along the way, and a configuration as shown in FIG. 5 may be employed in which a portion of the steam generated in the evaporation tube may be supplied to the vapor recompression ejector 101. In FIG. 5, a portion of the steam produced in the downstream evaporation tube 2d in the first evaporation tube group 3A is supplied to the vapor recompression ejector 101 through the vapor discharge duct 102. In this configuration, steam generated in the evaporation tube 2d can be used as a heat source for the other evaporation tubes 2a to 2c disposed upstream with respect to the evaporation tube 2d. Thus, condensed water (product water) required with fewer evaporation tubes can be obtained. The value obtained by dividing the range of operating temperature of the evaporator 2 (corresponding to the difference in operating temperature between the uppermost evaporating tube 2a and the lowermost evaporating tube 2t) by the number of evaporating tubes is obtained between the adjacent evaporating tubes. It is substantially equal to the difference in operating temperature. Thus, the smaller the evaporation tubes required, the larger the difference in operating temperature between adjacent evaporation tubes. This configuration makes it possible to efficiently generate drinking water for drinking or the like from the mixed water. The evaporation tube to which the steam discharge duct 102 is connected may be appropriately selected according to design conditions and the like.

In addition, a plurality of vapor recompression ejectors 101 are provided, and the configuration as shown in FIG. 6 in which steam generated in the other evaporation tubes 2d and 2h is supplied to one of the plurality of vapor recompression ejectors 101 is adopted. You may. The driving steam passing through one steam recompression ejector 101 is introduced into the heat transfer tube 221 of the uppermost evaporation tube 2a in the first evaporation tube group 3A, and the other vapor recompression ejector 101 is introduced. The driving steam passing through is introduced into the heat transfer tube 221 other than the heat transfer tube of the top evaporation tube 2a in the first evaporation tube group 3A.

In this embodiment, in order to prevent precipitation of a soft scale such as calcium carbonate in the evaporation tube, an acid may be added to untreated raw water such as seawater, followed by a decarbonization process.

In this embodiment, a flash evaporation duct and a second evaporation tube group for directing the concentrated brine produced in the first evaporation tube group 3A to the evaporation tubes 2e to 2h of the second evaporation tube group 3B. Decompression means for depressurizing the inside of the evaporation tubes 2e to 2h of 3B is provided, wherein the concentrated brine produced in the first evaporation tube group 3A performs flash evaporation in the second evaporation tube group 3B. May be employed to be supplied to the evaporation tubes 2e to 2h. Such a configuration can more efficiently produce condensate for drinking and other applications. When such a configuration is adopted, the dilution water supply means 7 is concentrated brine produced by flash evaporation, concentrated brine produced by heat exchange with heat transfer tube 221 and mixed water introduced through the mixed water discharge duct 72. The dilution water including the is supplied to the heat transfer tubes of the evaporation tubes 2e to 2h of the second evaporation tube group 3B.

The present inventors confirmed the evaporation tube mentioned above by calculating the solubility product as mentioned later. When untreated water having the same characteristics is used as the feed water supplied to the desalination apparatus, it is preferable to employ a liquid supplying method capable of generating as much condensed water (product water) as possible within a range where scale precipitation does not occur. . In other words, when the concentrated magnification value of the treated water to be supplied to the multi-efficiency evaporator 2 to be treated is increased, it is possible to generate the generated water more efficiently. Hereinafter, the efficient production of concentrated water (generated water) achieved by the desalination apparatus 1 and the method of generating fresh water according to the present invention will be described. Table 1 shows typical raw raw water (untreated seawater), scale component removal water (NF-generated water) in which the scale component was partially removed by the nanofiltration membrane apparatus 5, and the concentration of the scale component in the RO brine. In Table 1, the concentration of the scale component in the NF-generated water produced using the NF membrane (XUS-229323) manufactured by The Dow Chemical Company as the nanofiltration membrane apparatus 5 is described. . Regarding the quality of RO brine, the concentration of scale components in RO brine produced by the reverse osmosis membrane apparatus (RO apparatus) using the RO membrane (SW30HRLE-400) manufactured by The Dow Chemical Company is shown.

TABLE 1

Scale components Untreated water NF generation RO brine Ca (ppm) 480 180 1025 SO ₄ (ppm) 3200 100 255 CI (ppm) 23000 21000 46740 TDS (ppm) 102000 33000 77545

Evaporation tube 2a in the first evaporation tube group 3A through the mixed water supply means 6, the mixed water produced by mixing untreated seawater (untreated raw water), NF generated water and RO brine shown in Table 1 in a predetermined ratio. To 2d). Specifically, the mixed water includes 55 wt% untreated seawater (untreated raw water), 18 wt% NF produced water, and 27 wt% RO brine. The concentration of the scale component in the mixed water thus produced is shown in Table 2.

TABLE 2

Scale components Mixed water Ca (ppm) 411 SO ₄ (ppm) 1849 CI (ppm) 29050 TDS (ppm) 49977

Table 3 shows the condensate (generated water) at the rate of 24000 t / day using the desalination apparatus 1 having the constitution shown in FIG. 1 from the mixed water having the concentration of the scale components shown in Table 2. Evaporation and operating temperature (evaporation temperature). Table 3 shows the evaporation and operating temperature (evaporation temperature) of the most upstream evaporation tubes 2a, 2e, 2i, 2m, 2q in the evaporation tube groups 3A to 3E as an example. As shown in Fig. 1, the heated steam is supplied to the most upstream evaporator tube 2a in the first evaporator tube group 3A, and the temperature and pressure in the evaporator tube are controlled in the first evaporator tube group 3A. It gradually decreases from the most upstream evaporation tube 2a to the most downstream evaporation tube 2t in the fifth evaporation tube group 3E. In the evaporator tube groups 3A to 3E, the treated water to be treated is fed in parallel to each evaporator tube, and the amount of evaporation in the evaporator tube is made equal, thus concentrated brine at the surface of the heat transfer tube of the evaporator tube. The concentration of is also the same. The evaporation tubes 2a, 2e, 2i, 2m, and 2q shown in Table 3 are evaporation tubes in which scale precipitation easily occurs among all the evaporation tube groups.

[Table 3]

Evaporator tube group 1st evaporation tube 2a of the 1st evaporation tube group 5th evaporation tube 2e of the 2nd evaporation tube group Evaporation rate (kg / h) 50000 50000 Evaporation Temperature (℃) 125 109

Table 4 shows that the mixed water having the scale component concentration as shown in Table 2 under the evaporation conditions as shown in Table 3, that is, the evaporation temperature and the amount of evaporation, is evaporated in the desalination apparatus 1 until its concentration ratio value is 2 or 3. -Shows the result of calculation of the solubility product of when processed in the concentration process. FIG. 7 is a flowchart when the concentration magnification value in the desalination device 1 is 2. FIG. 8 is a flowchart when the concentration magnification value in the desalination apparatus 1 is 3. In calculating the solubility product here, it is assumed that the flow rate of the mixed water introduced from the mixed water supply means 6 into the dilution water supply means 7 becomes zero.

Table 4 shows the highest concentration of the concentrate (total dissolved solids, TDS), the solubility product of calcium and sulfate ions, and the highest acceptable solubility product of the concentrate on the surface of the heat transfer tube of the evaporator tube. If the solubility product exceeds the maximum allowable solubility product during operation of the desalination device, precipitation of scale occurs. Here, the value of the highest allowable solubility product ([Ca] × [SO ₄ ]) shown in the graph of FIG. 4 is the technical data book (OSW14.16Page 1A, 14.16Page 1B) of the Office of Saline Water. Calculated based on However, in order to determine the solubility product limit, it is measured by dissolving calcium sulfate (anhydrous) in raw and concentrated brine and treating mixed water of scale component removal water and raw raw water (untreated seawater) as feed water. There is a difficulty in applying directly to. When compared based on the concentration of the chlorine component, the US Department of State Salt Water Bureau data is obtained under conditions that are more stringent than those for descaling water. Therefore, there is no problem for convenience in determining the solubility product limit, and can be made safe. To more accurately calculate the solubility product limit, the ionic strength of the feed water can be used as a reference.

The calculation of the solubility product in Table 4 is described below. For example, a method of determining the solubility product in the evaporation tube 2a of the first evaporation tube group 3A when the concentration magnification value in the desalination apparatus is 2 will be described. According to FIG. 7, the flow rate of the mixed water supplied to the evaporation tube 2a in the first evaporation tube group 3A can be obtained by the formula: (2000t / hr) / 4 evaporation tubes = 500t / hr The flow rate of the steam produced in the evaporation tube 2a can be obtained by the formula: (200t / hr) / 4 evaporation tubes = 50t / hr. Therefore, the concentrated magnification value in the evaporation tube 2a can be obtained by the formula: (500t / hr) / (500t / hr-50t / hr) = 1.1111. Therefore, the concentrated brine in the evaporation tube 2a has a calcium component concentration of 411 x 1.1111 = 457 ppm and a sulfuric acid concentration of 1849 x 1.1111 = 2054 ppm. Therefore, the calcium content can be obtained by the formula: 457/40/1000 = 0.011425 mol / mole (where 40 is the atomic weight of calcium), and the sulfate ion component is represented by the formula: 2054/96/1000 = 0.021396 mol / 1, where 96 is the molecular weight of sulfate ions. Therefore, the solubility product of calcium sulfate is (calcium component) x (sulfate ion component) = 0.011425x0.021396 = 0.000244.

TABLE 4

 Item 1st evaporation tube 2a of the 1st evaporation tube group 5th evaporation tube 2e of the 2nd evaporation tube group 9th evaporation tube (2i) of the third evaporation tube group 13th evaporator of the 4th evaporator group (2m) 17th evaporator of the 5th evaporator group (2q) 2x brine concentration TDS (ppm)  55530  72082  82380  96110  115332 Solubility product [Ca] × [SO ₄ ]  0.000244  0.000412  0.000538  0.000732  0.001054 Highest acceptable water product [Ca] × [SO ₄ ]   0.000355   0.000468   0.000733   0.001641   0.00309 Presence of Scale  radish  radish  radish  radish  radish 3 times drainage concentration TDS (ppm)  57666  78635  96110  123570  172998 Solubility product [Ca] × [SO ₄ ]  0.000264  0.00049  0.000732  0.00121  0.00237 Highest acceptable water product [Ca] × [SO ₄ ]   0.000354   0.000501   0.000804   0.00191   0.00372 Presence of Scale  radish  radish  radish  radish  radish

As can be clearly seen from the results shown in Table 4, calcium ions in each of the evaporation tubes 2a, 2e, 2i, 2m, 2q, which are located on the most upstream side of the evaporation tube groups 3A to 3E, are easily precipitated with scale components. The solubility product of and sulfate ion is lower than the maximum allowable solubility product. This indicates that even if the desalination device is operated under extreme high temperature conditions such as 125 ° C., there is no risk of scale precipitation occurring on the surface of the heat transfer tubes of the evaporator tube and at other sites. Therefore, the desalination apparatus of the present embodiment achieves efficient generation of condensed water (product water) for drinking and other fields.

For comparison, the solubility product was calculated when the mixed water was supplied to the evaporation tube in the third evaporation tube group 3C and the mixed water was supplied to the evaporation tube in the fifth evaporation tube group 3E. Table 5 and Table 6 show the results. The concentration factor value in the desalination device 1 is 2 or 3. FIG. 9 is a flowchart in the case where the mixed water is supplied to the evaporation tube in the third evaporation tube group 3C under the assumption that the desalination apparatus 1 has a concentration magnification value of 2, and FIG. The flowchart in the case. FIG. 11 is a flowchart in the case where the mixed water is supplied to the evaporation tube in the fifth evaporation tube group 3E under the assumption that the concentration ratio of the desalination device 1 is 2, and FIG. 12 is the concentration magnification value of 3. This is a flowchart from.

TABLE 5

 Item 1st evaporation tube 2a of the 1st evaporation tube group 5th evaporation tube 2e of the 2nd evaporation tube group 9th evaporation tube (2i) of the third evaporation tube group 13th evaporator of the 4th evaporator group (2m) 17th evaporator of the 5th evaporator group (2q)     2x brine concentration TDS (ppm)  102975  79329  55530  96110  115332 Solubility product [Ca] × [SO ₄ ]  0.00084  0.000499  0.000244  0.000732  0.001054 Highest acceptable water product [Ca] × [SO ₄ ]   0.000562   0.000501   0.000562   0.001641   0.00309 Presence of Scale  U  radish  radish  radish  radish     3 times drainage concentration TDS (ppm)  131059  96110  57666  123570  172998 Solubility product [Ca] × [SO ₄ ]  0.001361  0.000732  0.000264  0.00121  0.00237 Highest acceptable water product [Ca] × [SO ₄ ]   0.000684   0.000596   0.000562   0.001905   0.003236 Presence of Scale  U  U  radish  radish  radish

TABLE 6

 Item 1st evaporation tube 2a of the 1st evaporation tube group 5th evaporation tube 2e of the 2nd evaporation tube group 9th evaporation tube (2i) of the third evaporation tube group 13th evaporator of the 4th evaporator group (2m) 17th evaporator of the 5th evaporator group (2q)     2x brine concentration TDS (ppm)  210630  182546  146037  107094  55530 Solubility product [Ca] × [SO ₄ ]  0.003516  0.002641  0.00169  0.000909  0.000244 Highest acceptable water product [Ca] × [SO ₄ ]   0.000871   0.000876   0.001023   0.001758   0.001955 Presence of Scale  U  U  U  radish  radish     3 times drainage concentration TDS (ppm)  257880  232092  197278  157823  57666 Solubility product [Ca] × [SO ₄ ]  0.00527  0.00469  0.003084  0.001974  0.000264 Highest acceptable water product [Ca] × [SO ₄ ]   0.000861   0.000933   0.001161   0.002113   0.001995 Presence of Scale  U  U  U  radish  radish

As can be clearly seen from the results shown in Tables 5 and 6, when the mixed water is supplied to the third and fifth evaporation tube groups 3C and 3E, the heat transfer tube at both the concentration ratio values 2 and 3 Scale precipitation of was found. This indicates that the concentration ratio value needs to be controlled to be 2 or less in order to efficiently produce concentrated water (product water) for drinking and other fields.

Claims (6)

A multi-effect evaporator having a plurality of evaporation tubes; And a plurality of heat transfer tubes through which steam passes, and by supplying the feed water to the outer surfaces of the plurality of heat transfer tubes, steam and concentrated brine are generated from the feed water, and the steam generated in the preceding evaporation tube is transferred to the next evaporation tube. The plurality of evaporation tubes are connected to each other in such a way that the vapor can be used as a heat source in the next evaporation tube, and the plurality of evaporation tubes are arranged from upstream to downstream, respectively. Desalination apparatus divided into groups), Scale component removing means for removing at least a portion of the scale component contained in the raw raw water to produce scale component removing water; A heat transfer tube of each evaporation tube of the first evaporation tube group positioned at the most upstream in the plurality of evaporation tube groups, the mixed water supply means for supplying a mixed water of raw raw water and scale component removal water as supply water; A dilution water provided by mixing the concentrated brine and the mixed water mixed by the mixed water supply means is supplied to the heat transfer tubes of the respective evaporating tubes of the second evaporating tube group located on the low temperature side after the first evaporating tube group. Dilution water supply means Desalination apparatus further comprising a. The method of claim 1, The dilution water supply means Configured to supply dilution water provided by mixing the concentrated brine produced in the first evaporation tube group with the mixed water provided by the mixed water supply means to the heat transfer tubes of each evaporation tube of the second evaporation tube group. Desalination device. The method of claim 2, Each of the evaporation tube groups other than the first and second evaporation tube groups Supplying concentrated brine produced in any one of a plurality of evaporation tube groups other than the first and second evaporation tube groups to the heat transfer tubes of each evaporation tube of the evaporation tube group other than the first and second evaporation tube groups Concentrated brine supply means for supplying as Desalination device. The method of claim 1, Flash evaporation means for supplying the concentrated brine produced in the first evaporation tube group to each evaporation tube of the second evaporation tube group to perform flash evaporation, The dilution water supplying means supplies dilution water provided by mixing concentrated brine produced by the flash evaporation, concentrated brine produced in the second evaporation tube group, and mixed water provided by the mixed water supplying means. Configured to feed into the heat transfer tubes of each evaporation tube of the group Desalination device. The method according to any one of claims 1 to 4, The scale component removing means is a nanofiltration membrane device Desalination device. A plurality of evaporation tubes and a plurality of heat transfer tubes through which steam passes, and by supplying the feed water to the outer surfaces of the plurality of heat transfer tubes, steam and concentrated brine are generated from the feed water, and the steam generated in the preceding evaporation tube is next The plurality of evaporation tubes are connected to each other in such a way that a vapor can be used as a heat source in the next evaporation tube so that the plurality of evaporation tubes are arranged upstream and downstream respectively. A method of generating fresh water using a desalination apparatus divided into groups, A scale component removal step of removing at least a portion of the scale component contained in the raw raw water to produce scale component removal water; A mixed water supplying step of supplying mixed water of raw raw water and scale component removing water as supply water to a heat transfer tube of each evaporating tube of the first evaporating tube group positioned at the most upstream in the plurality of evaporating tube groups; A heat transfer tube of each evaporation tube of the second evaporation tube group located on the low temperature side after the first evaporation tube group, wherein dilution water provided by mixing the concentrated brine and the mixed water provided in the mixed water supplying step is supplied as supply water. Dilution water supply stage How to generate fresh water comprising a.

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