JPH1110147A - Distilling apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distilling apparatus whose distilling productivity is heightened. SOLUTION: Membrane modules 11 constituted of evaporating parts 12 and condensing parts 15 are installed in three stages. A sea water sending-out pipe 26 is led out of a cooling pipe 24A and connected with a leading-in side of a warm sea water leading-in part 13B and the discharge side of the warm sea water leading-in part 13B is connected with leading in side of a cooling pipe 24C to compose a first raw water flow route. On the other hand, a warm sea water leading-in part 13A, a cooling pipe 24B, and a warm sea water leading-in part 13C are connected in series in the same manner as the first raw water flow route to compose a second raw water flow route. The tip end of the second raw water flow route and the terminal end of the first raw water flow route are connected with each other through a heating means 28 to compose a distilling apparatus 10. In such a distilling apparatus 10, the sum of the values produced by subtraction of the inlet temperature of the condensing parts 15 from the inlet temperature of the evaporating parts 12 becomes the maximum and the energy efficiency can be made the maximum and at the same time by installing a plurality of the membrane modules 11, water production efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desalination apparatus for obtaining fresh water from seawater, river water, etc., and more particularly to a hydrophobic porous membrane (PV membrane) which prevents permeation of liquids and suspended substances and allows water vapor to permeate. The present invention relates to a desalination apparatus for extracting fresh water using the apparatus.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining fresh water from seawater or river water, a method such as a pervaporation method is known. FIG. 6 is a conceptual diagram showing the principle of fresh water generation in the pervaporation method. As shown in FIG. 1, in the pervaporation membrane module 1, the warm seawater chamber 2 and the cold seawater chamber 3 are connected via the heating device 4, and the production is performed between the warm seawater chamber 2 and the cold seawater chamber 3. Water room 5
Is provided so as to be sandwiched between both chambers. A hydrophobic porous membrane (PV membrane) is provided between the warm-sea water chamber 2 and the production water chamber 5 to prevent the permeation of liquids and suspended substances while allowing water vapor to permeate.
The cold seawater chamber 3 and the production water chamber 5 are partitioned by a cooling plate 7. When the pervaporation membrane module 1 configured as described above is operated, water vapor permeates through the micropores of the hydrophobic porous membrane 6 from the seawater introduced into the warm seawater chamber 2 due to the vapor pressure difference between the hydrophobic porous membrane 6 and the seawater. Then, it moves to the production water chamber 5 side. The water vapor that has moved to the production water chamber 5 is condensed under the influence of the cooling plate 7 that is in contact with the cold seawater, becomes distilled water (fresh water), and is sent out from the production water chamber 5 to the outside.

[0003]

However, in the above-mentioned pervaporation method, distilled water is taken out using a slight vapor pressure difference before and after the hydrophobic porous membrane 6, so that its energy efficiency (performance ratio, performance ratio, Water production ratio) was never high. For this reason, it has been studied to increase the production efficiency of distilled water by setting the pressure on the production water chamber 5 side to a negative pressure and increasing the pressure difference before and after the hydrophobic porous membrane 6. In 1, the distance between the hydrophobic porous membrane 6 and the cooling plate 7 is reduced in order to improve the heat transfer rate between the warm seawater chamber 2 and the cold seawater chamber 3. Therefore, even if suction is performed from the outlet side of the production water chamber 5, the entirety of the production water chamber 5 is set to a negative pressure only by the hydrophobic porous membrane 6 being in close contact with the cooling plate 7 near the exit of the production water chamber 5. It was difficult.

Further, in the pervaporation membrane module 1, since the distance between the hydrophobic porous membrane 6 and the cooling plate 7 is short as described above, when the distilled water is sent out from the production water chamber 5, considerable flow resistance is generated. And the pressure in the production water chamber 5 increased due to the flow resistance. In the production water chamber 5, the steam pressure difference is originally small at a place where the heat exchange is sufficiently performed at a low temperature. For this reason, it is conceivable that the pressure increase caused by the flow resistance is larger in such a portion.

Further, since the pressure from the warm seawater through the hydrophobic porous membrane 6 is used for sending distilled water from the production water chamber 5, both pressures are applied to the production water chamber 5 to make the hydrophobic water. A small difference in vapor pressure before and after the porous membrane 6 is narrowed, and the energy efficiency is further reduced. In addition, increasing the flow rate of warm seawater to increase the temperature difference from seawater before heating in order to secure the production of distilled water has also been a factor that deteriorates energy efficiency.

In the structure of the pervaporation membrane module 1,
In order to obtain the production water volume, the temperature of the warm seawater chamber 2 and the temperature of the cold seawater chamber 3
The larger the difference from the temperature is, the better. However, increasing the temperature difference between the two means lowering the energy efficiency. Moreover, for that purpose, the flow rate of seawater passing through the pervaporation membrane module 1 must be increased, and increasing the flow rate of the seawater is dependent on the rate of fresh water, that is, the amount of seawater pumped and the amount of freshwater extracted therefrom. Another problem is that the ratio is reduced.

An object of the present invention is to provide a fresh water generator capable of improving energy efficiency and fresh water production rate and increasing fresh water productivity by focusing on the above conventional problems.

[0008]

Means for Solving the Problems The inventors of the present invention have made various studies to improve the energy efficiency and have conducted experiments. As a result, a plurality of evaporating sections and condensing sections are connected alternately, and heating or cooling means are provided in the middle thereof. It has been found that when one is provided, there is a difference in energy efficiency depending on the combination.

The present invention has been made based on the above findings, and a fresh water generator according to the present invention is provided with an evaporating section for taking out water vapor from raw water through a hydrophobic porous membrane, and for taking in and condensing the water vapor. A plurality of membrane modules including a condensing section are provided, and after selecting one of the evaporating section and the condensing section in the first-stage membrane module, the opposite side is selected in the next-stage membrane module, and this is selected in the final stage. The first raw water flow path is formed by repeatedly connecting the membrane modules in series to form a first raw water flow path, and the second raw water flow path is formed by connecting the remaining side of the membrane module in series in the same order as the first raw water flow path to form a second raw water flow path. The first raw water flow path and the second raw water flow path were connected in series via a cooling means.

Preferably, the membrane module is composed of an odd number of stages, and the evaporating section is divided into a plurality of stages along the raw water flow path, and the condensing section divided by the same number of stages as the evaporating section is provided with suction means. The membrane modules were configured to be connected individually via

[0011]

According to the study by the inventors, the structure of the membrane module is divided into the evaporating section and the condensing section, so that the hydrophobic porous membrane does not contact the condensing section side. For this reason, the pressure on the back side of the hydrophobic porous membrane can be set to a negative pressure, and the extraction of water vapor is performed based on the difference between the vapor pressures before and after the hydrophobic porous membrane. Can be increased. In addition, since water (gas) moves from the evaporating section to the condensing section, the flow resistance during the movement can be reduced, and the delivery of distilled water from the production water chamber requires a hydrophobic porous membrane. Since the pressure from the warm seawater through the membrane is not used, there is no factor for narrowing the pressure difference before and after the hydrophobic porous membrane, and thus the energy efficiency can be improved.

The provision of a plurality of membrane modules makes it possible to repeatedly take out fresh water from the same raw water for the number of membrane modules installed, thereby improving the fresh water production rate. Furthermore, the first-stage membrane module side of the first raw water flow path is set to the last-stage membrane module side of the second raw water flow path,
Alternatively, if the first-stage membrane module side of the second raw water flow path is set to be connected to the last-stage membrane module side of the first raw water flow path, each membrane module can be connected between the first raw water flow path and the second raw water flow path. Since the distillation operation is performed by alternately exchanging heat every time, the sum of the values obtained by subtracting the inlet temperature of the condenser from the inlet temperature of the evaporator in each membrane module is the combination of the connection between the evaporator and the condenser. And the highest energy efficiency can be achieved.

If the number of installed membrane modules is an odd number, the order of connection of the evaporating section and the condensing section in the present apparatus is all alternated, so that the effect of the heating or cooling means on the raw water can be small. Therefore, the load on the heating or cooling means is reduced, and the energy efficiency can be increased.

If the membrane module is configured such that the evaporating section is divided into a plurality of stages along the raw water flow path and the condensing sections divided by the same number of stages as the evaporating section are individually connected via suction means, It is possible to set the degree of negative pressure of each evaporating section partitioned by the means.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of a fresh water generator according to the present invention will be described in detail with reference to the drawings.

FIG. 2 is an explanatory view of the structure of the membrane module.
As shown in the figure, the membrane module 11 (within the range of the broken line)
It comprises an evaporator 12 for extracting water vapor from seawater as raw water, and a condenser 15 for taking in and condensing the water vapor.

In the evaporating section 12, two spaces are formed by a hydrophobic porous film 18 (hereinafter referred to as a PV film) for preventing the permeation of a liquid or a suspended substance while allowing the water vapor to permeate, and the space is formed on one side. The hot seawater introduction section 13 is provided with an inlet / outlet port so that heated seawater (hot seawater) can be introduced and discharged. And the steam extraction part 14 on the other side
Is divided into a plurality of stages (seven stages in the figure) along the warm seawater introduction unit 13 so that no flow is generated between adjacent steam extraction units 14. In this way, the steam delivery pipes 20 are individually drawn out from the steam extraction sections 14 divided into a plurality of stages, and can be connected to a steam condensation section described later.

On the other hand, the condensing section 15 is provided with a steam condensing section 17 partitioned by the same number of stages as the steam extracting section 14, and a cooling pipe 24 is provided so as to pass through the steam condensing sections 17 set in multiple stages. Have been. The cooling pipe 2
The introduction of seawater (cold seawater) before heating is possible inside 4, and the introduction direction is opposite to the introduction direction of warm seawater in the evaporating section 12. A plurality of cooling fins are provided outside the cooling pipe 24 so as to increase the condensation efficiency of the steam fed from the steam outlet 14 via the steam delivery pipe 20. The steam condensing section 1
A suction pump 22 serving as a suction means is connected to 7, and by operating the suction pump 22, the negative pressure on the steam extraction section 14 side can be individually set. In the present embodiment, the suction pump 22 is used for the purpose of improving energy efficiency. However, a blower is used instead of the suction pump 22 for the purpose of improving fresh water efficiency, and the ejection port of the blower is directed to the condensing section 15 side. Thus, the steam extraction section 14 may be set to a negative pressure. Further, a fresh water take-out pipe 11A is drawn out from the bottom of the steam condensing section 17, so that distilled water obtained by the condensing action can be taken out of the membrane module 11.

FIG. 1 is a connection explanatory view showing the configuration of a fresh water generator according to the embodiment. As shown in the drawing, the fresh water generator 10 according to the embodiment includes the above-described membrane module 11 (11
A, 11B, 11C) in odd stages (3 in this embodiment).
Stage).

An introduction pipe 30 is connected to the introduction side (upper side in the figure) of the cooling pipe 24A in the first stage membrane module 11A, and cool seawater is supplied from a tank (not shown) provided outside the fresh water generator 10 to the condensation section 15A. It is possible to introduce. Then, the seawater delivery pipe 26 is drawn out from the discharge side (lower side in the figure) of the cooling pipe 24A and connected to the introduction side of the warm seawater introduction section 13B in the second stage membrane module 11B. The discharge side is connected to the introduction side of the cooling pipe 24C in the third-stage membrane module 11C, and forms a first raw water flow path. Then, the warm seawater introduction sections 13A, 2A of the first stage membrane module 11A, which is the remaining side of the membrane module 11,
The cooling water pipe 24B of the membrane module 11B of the first stage and the hot seawater introduction portion 13C of the membrane module 11C of the third stage are connected in series in the same order as the above-mentioned first raw water channel to form a second raw water channel. Then, the inlet of the warm seawater introduction portion 13A, which is the tip of the second raw water flow path, and the discharge port of the cooling pipe 24C, which is the end of the first raw water flow path, are connected to configure the fresh water generator 10. In addition, between the inlet of the warm seawater inlet 13A and the outlet of the cooling pipe 24C,
A heating device 28 is connected to heat the passing seawater.

A procedure for extracting fresh water from seawater using the fresh water producing apparatus 10 configured as described above will be described. First, when seawater is introduced into the desalination apparatus 10 using the introduction pipe 30, the seawater alternately passes through the evaporating unit 12 and the condensing unit 15 and is discharged from the discharge side of the warm seawater introducing unit 13C in the final stage membrane module 11C. You. In this state, when the heating device 28 provided in the middle of the raw water flow path is operated, the temperature of the seawater passing through the heating device 28 rises so that a temperature difference occurs between the evaporating unit 12 and the condensing unit 15. Become. FIG. 3 is a temperature diagram showing the temperature of seawater at the inlet / drain outlet positions in the evaporating section 12 and the condensing section 15. That is, as shown in the figure, when seawater is introduced into the fresh water generator 10 and the heating device 28 is operated, in the first stage membrane module 11A, seawater passing through the membrane module 11A for the second time is supplied to the warm seawater introduction unit 13A. Introduced new (cooling) seawater into cooling pipe 2
4A. Here, the seawater introduced into the warm seawater introduction unit 13A is heated by the heating device 28 provided at the preceding stage, and a temperature difference from fresh seawater is generated.

In the membrane module 11A, the steam extraction section 1A in contact with the warm seawater introduction section 13A and the cooling pipe 24A.
4 and the steam condensing section 17 are partitioned into a plurality of stages, so that the extraction of steam through the PV film 18 is performed independently by each stage. For this reason, the temperature gradient at the partitioned part can be reduced, so that the efficiency of extracting steam can be increased. In addition, as described above, the suction pump 22
Is provided, and independent negative pressure setting is possible. For this reason, if the suction force of the suction pump 22 is increased toward the lower temperature side (the discharge side of the hot seawater introduction unit 13A), and the steam extraction unit 14 on the discharge side of the hot seawater introduction unit 13A is set to a negative pressure, the lower the temperature, the lower the temperature. Insufficient pump pressure difference
, The efficiency of extracting water vapor can be increased.

The extraction of water vapor through the PV film 18 is as follows. When a temperature difference occurs between the warm seawater introduction unit 13A and the cooling pipe 24A, a vapor pressure difference occurs before and after the PV film 18 (in addition, a negative pressure by the suction pump 22 is also applied). For this reason, the water vapor permeates through the fine holes of the PV film 18 and moves to the water vapor take-out part 14A. The steam that has moved to the steam extracting section 14A is sent into the steam condensing section 17A via the steam connecting pipe 20. When the steam reaches the steam condensing section 17A, the steam becomes
It is cooled by the cooling pipe 24A that performs a cooling function, and is taken out as distilled water from the steam condensing section 17 by the condensing function. Since the heat exchange is performed between the hot seawater introduction unit 13 and the cooling pipe 24 due to the condensation of the steam, the relative temperature difference between the two does not change, but the hot seawater introduction unit 13 proceeds from the inlet to the discharge outlet. As the temperature of the seawater decreases, the temperature of the seawater on the cooling pipe 24 side increases as the water advances from the inlet to the outlet.

The seawater on the side of the warm seawater introducing section 13A and the seawater on the side of the cooling pipe 24B introduced into the first-stage membrane module 11A pass through the first-stage membrane module 11A, and then are introduced into the second-stage membrane module 11B. You. Here, in the second-stage membrane module 11B, the seawater on the hot seawater introduction portion 13A side is introduced into the cooling pipe 24B side, and the seawater on the cooling pipe 24A side is introduced into the hot seawater introduction portion 13B side. As in the first-stage membrane module 11A, distilled water can be taken out by the heat exchange. In the subsequent membrane module 11 as well, if heat exchange is performed alternately between the hot seawater introduction section 13 side and the cooling pipe 24 side, distilled water can be taken out.

In the fresh water generator 10 configured as described above,
Evaporation unit 12 and condensation unit 15 in the same membrane module 11
Since water vapor is generated due to the temperature difference from the above and distilled water is taken out, distilled water can be taken out from all the membrane modules 11 provided in three stages. Then, the seawater introduced into the fresh water generator 10 is extracted by the PV membrane 18 by the amount of the additional membrane module 11, so that the fresh water rate can be improved. The upper limit of the fresh water generation rate is desirably set to about 50% in consideration of the durability of the PV membrane 18 and the corrosion resistance of the fresh water generator 10. The number of the membrane modules 11 may be set.

Although FIG. 1 shows a combination of the evaporating section 12 and the condensing section 15 of the membrane module 11 provided in three stages, other combinations exist other than the connection example. FIG. 4 is an explanatory diagram of a connection example showing a combination of an evaporator and a condenser when three stages of membrane modules 11 are provided (excluding the combination of FIG. 1). As shown in the figure, when three stages of the membrane modules 11 are provided, and the evaporating units are 1, 2, and 3 in order from the upper stage, the number of combinations of the condensing units to be connected is represented by the following formula. .

[Equation 1] 3! / 1! = 3 * 2 * 1/1 = 6 (way)

The inventor provided only one heating device 28 between the evaporating unit 12 and the condensing unit 15 thus combined (immediately before the first-stage evaporating unit), and simplified the entire fresh water generator 10. And the combination with the highest energy efficiency was confirmed by experiments. As a result, the value obtained by subtracting the seawater temperature on the condensing section 15 introduction side from the seawater temperature on the evaporating section 12 introduction side in each membrane module 11 is obtained.
By adding each time, the example of the combination shown in FIG.
It was found that the numerical value was the largest among the combinations and the energy efficiency was the largest. It has been confirmed that the effect of the combination shown in FIG. 1 does not change even when the number of stages exceeds three.

FIG. 5 shows a case where the membrane module 11 has an even number (four stages).
It is explanatory drawing which shows the structure of the provided fresh water generator. In the case where the membrane module 11 is set to an even-numbered stage as shown in FIG.
When trying to connect the first raw water flow path and the second raw water flow path, the condensing section 15A and the condensing section 15D are continuous. As described above, when the membrane module 11 has an even number of stages, the cooling device 32 is provided between the condenser 15A and the condenser 15D to cool the seawater of the condenser 15D heated by the evaporator 12D and to cool the condenser 1
What is necessary is just to introduce into 5A. The introduction pipe 30 is connected to the condenser 15
In the configuration connected to the A side, it goes without saying that the heating device 28 is used instead of the cooling device 32.

In the present embodiment, since the configuration of the fresh water generator 10 is divided into the evaporating section 12 and the condensing section 15, the configuration of the PV film 18 in the evaporating section 12 does not matter. Therefore, the configuration of the PV film 18 can be freely set depending on the application, such as a spiral type or a laminated type. On the other hand, since the influence of the PV film 18 does not need to be taken into consideration in setting the shape of the cooling pipe 24 even in the condensing section, for example, the fin shape of the cooling pipe 24 can be set freely.

In this embodiment, the inlet pipe 30 is connected to the condenser 15A to feed the cold seawater. However, the inlet pipe 30 is connected to the evaporator 12A, and the heated seawater is supplied to the evaporator. You may send in. Thus, the fresh water generator 10
Can achieve the same effect as the present embodiment. When configuring such a fresh water generator, the cooling device 32 may be provided at the same position instead of the heating device 28.

[0031]

As described above, according to the present invention, there are provided a plurality of membrane modules each comprising an evaporating section for extracting water vapor from raw water via a hydrophobic porous membrane, and a condensing section for capturing and condensing the water vapor. After selecting one of the evaporating section and the condensing section in the first-stage membrane module, selecting the opposite side in the next-stage membrane module and repeating this up to the last-stage membrane module to connect in series First
While forming the raw water flow path, the remaining side of the membrane module is connected in series in the same order as the first raw water flow path to form a second raw water flow path, and the first raw water flow path is connected to the first raw water flow path via heating or cooling means. Since the second raw water flow path is connected in series, it is possible to improve energy efficiency and fresh water production rate and increase fresh water productivity.

The membrane module is configured such that the evaporating section is partitioned into a plurality of stages along the raw water flow path, and the condensing sections partitioned by the same number of stages as the evaporating section are individually connected via suction means. Accordingly, it is possible to set the degree of negative pressure of each of the partitioned evaporating sections, and if the degree of negative pressure is increased on the low temperature side where the vapor pressure difference is small, the productivity of fresh water can be further increased.

[Brief description of the drawings]

FIG. 1 is a connection explanatory diagram showing a configuration of a fresh water generator according to an embodiment.

FIG. 2 is a diagram illustrating the structure of a membrane module.

FIG. 3 is a temperature diagram showing the temperature of seawater at the inlet / drain outlet position in the evaporating section 12 and the condensing section 15.

FIG. 4 is an explanatory diagram of a connection example showing a combination of an evaporator and a condenser when three stages of membrane modules 11 are provided (excluding the combination of FIG. 1).

FIG. 5 is an explanatory diagram showing a configuration of a fresh water generator provided with an even number (four stages) of membrane modules 11;

FIG. 6 is a conceptual diagram showing the principle of fresh water generation in the pervaporation method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pervaporation membrane module 2 Hot sea water chamber 3 Cold sea water chamber 4 Heating device 5 Production water chamber 6 Hydrophobic porous membrane (PV membrane) 7 Cooling plate 10 Fresh water generator 11 Membrane module 12 Evaporator 13 Hot seawater introduction part 14 Take-out part 15 Condensing part 16 Cold seawater introducing part 17 Steam condensing part 18 Hydrophobic porous membrane (PV membrane) 20 Steam delivery pipe 22 Suction pump 24 Cooling pipe 26 Seawater delivery pipe 28 Heating device 30 Introductory tube 32 Cooling device

Claims (3)

[Claims] 1. A plurality of membrane modules each comprising an evaporator for extracting water vapor from raw water via a hydrophobic porous membrane, and a condenser for taking in the water vapor and condensing the vapor, are provided. After selecting one of the condensing section and the other, the opposite side is selected in the next-stage membrane module, and this is repeated until the final-stage membrane module is connected in series to form the first raw water flow path, The remaining side of the membrane module is connected in series in the same order as the first raw water flow path to form a second raw water flow path, and the first raw water flow path and the second raw water flow path are connected via heating or cooling means. A fresh water generator characterized by being connected in series. 2. The fresh water generator according to claim 1, wherein the membrane module is provided in an odd number of stages. 3. The membrane module is partitioned into a plurality of stages along the raw water flow path, and the membrane modules are individually connected to the condensing units partitioned by the same number of stages as the evaporating units via suction means. The fresh water generator according to claim 1 or 2, wherein the fresh water generator is configured.