JPS6265705A - Membrane distillation device - Google Patents

Abstract

PURPOSE:To improve the heat efficiency of the titled device by repeatedly providing a raw liq. passage, a membranous pipe, a heat-transfer pipe and a partition pipe to form a multistage structure and reutilizing the raw liq. which has once been used as the cooling heat source in a succeeding stage. CONSTITUTION:The first membranous pipe 2, the first heat-transfer pipe 4 and a partition pipe 6 are provided around a heater 1 furnished on the center axis to form the first raw liq. passage 3, the first evaporation space 5 and the first cooling water passage 7. Then the second membranous pipe 8, the second heat-transfer pipe 9 and the second partition pipe 10 constituting the second stage are successively furnished on the outer periphery of the partition pipe 6 to form the second raw liq. passage 11, the second evaporation space 12 and the second cooling water passage 13. The raw liq. is introduced into the second cooling water passage 13 from a raw liq. inlet pipe 14. The raw liq. heated in the passage is introduced into the first cooling water passage 7 by a connection pipe 15 and then introduced into the first and the second raw liq. passage 3 and 11 by a connection pipe 16. The steam permeated through the membranous pipes 2 and 8 is condensed and liquefied on the surfaces of the heat- transfer pipes 4 and 9 and the condensate is discharged from a condensate discharge pipe 18.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a membrane distillation apparatus, and more specifically, to thermopervaporation, which performs distillation by promoting evaporation of a stock solution using heat.

<Prior art> As a method for separating and concentrating a solution, a high temperature liquid to be treated, that is, a raw liquid such as hot sea water, is passed through the primary side of a porous polymer membrane that allows liquid vapor to pass through but not the liquid itself. The vapor generated from the stock solution and passed through the porous membrane is cooled and condensed on the secondary side, thus concentrating the stock solution on the next side and obtaining a condensed liquid on the secondary side. ration is already known, and various devices for it have been proposed.

For example, in Japanese Patent Publication No. 49-45461, a large number of vertically extending membrane walls and a large number of heat transfer walls are provided parallel to each other with a space between them, and a gap between two adjacent membrane walls is disclosed. A high-temperature raw liquid passageway is provided, a cooling water passageway is provided between two adjacent heat transfer walls, and a steam space is provided between the adjacent membrane wall and heat transfer wall, which serves as a passageway for generated steam and distilled water. A device is described in which cooling water passages are formed between the heat transfer wall and the side wall at both ends of the device body.

<Problems to be Solved by the Invention> According to such a conventional device, the high-temperature stock solution is heated by a heat exchange layer thrown outside and then introduced into the device in parallel. There was a problem in that a decrease in thermal efficiency due to heat radiation was unavoidable.

Therefore, the main object of the present invention is to provide a membrane distillation apparatus with good thermal efficiency, which prevents wasteful heat radiation without providing a heat insulating device.

Another object of the present invention is to provide a membrane distillation apparatus with good thermal efficiency and large capacity for the above reasons.

Still another object of the present invention is to use the undiluted solution as a heating medium for cooling,
An object of the present invention is to provide a membrane distillation apparatus that does not require cooling water.

Still another object of the present invention is to provide a multiplexed structure to
The stock solution, which has been used as a cooling heat medium and whose temperature has risen, is reused as a heat medium for cooling in the next stage, and the stock solution whose temperature has risen in this way is introduced into the stock solution passage, and by reusing such heat, thermal efficiency is improved. An object of the present invention is to provide a membrane distillation apparatus with further improved properties.

Means for Solving the Problems〉 The membrane distillation apparatus of the present invention includes a heater provided at the shaft center,
A membrane tube made of a porous polymer membrane that forms a liquid passageway around the heater and allows the vapor of the liquid to permeate through it without allowing the liquid to pass through, and a heat transfer tube that forms a vapor space around the membrane tube. and a partition tube that forms a cooling heat medium passage around the heat transfer tube, and a raw liquid passage, a membrane tube, a heat transfer tube, and a partition tube are repeatedly provided on the same axis around the outer periphery of the partition tube, and the raw liquid is used as a cooling heat medium. It is characterized in that the condensate liquid that is discharged through the raw liquid passage around the heater and condensed in the vapor space is led out to the outside after being used as a heater.

Effect> The stock solution introduced from the outside is first used as a heating medium for cooling the outermost stage, and then is used as a heating medium for cooling stages closer to the center, and its temperature gradually increases. On the other hand, the stock solution around the heater in the center is heated by the heater and has the highest temperature, and the stock solution whose temperature gradually decreases due to evaporation is used as the stock solution in stages farther from the center. With such a multi-stage configuration, heat exchange between the raw liquid and the cooling heat medium is performed in each stage. The condensate generated at each stage in the multi-stage configuration is collected in parallel and led to the outside.

<Example> FIG. 1 shows a longitudinal cross-sectional view of an example of a two-stage configuration of the present invention,
FIG. 2 shows a sectional view taken along the line AA'.

It has a cylindrical shape as a whole, and a heater 1 is provided on the central axis, and a first membrane tube 2 is provided around the heater 1, and a first stock solution passage is provided between the heater 1 and the membrane tube 2. 3 is formed, a first heat exchanger tube 4 is provided around the membrane tube 2, a first evaporation space 5 is formed between the membrane tube 2 and the heat exchanger tube 4, and a first heat exchanger tube 4 is provided around the heat exchanger tube 4. A partition pipe 6 is provided, and a first cooling water passage 7 is formed between the heat transfer tube 4 and the partition pipe 6. On the outer periphery of the partition pipe 6, a second membrane pipe 8 constituting the second stage is provided. Second heat exchanger tube9. A second partition pipe lO is sequentially provided to connect the second stock solution passage 11. Second evaporation space 12. A second cooling water passage 13 is formed. The second partition pipe 10 is the outermost pipe and thus becomes the outer pipe of the device. In the figure, evaporation spaces 5 and 1
The waveform depicted in 2 represents a spacer.

The lower end of the second cooling water passage 13 is connected to the stock solution introduction pipe 14, and the upper end of the second cooling water passage 13 and the first cooling water passage 7
The upper ends thereof are connected by a connecting pipe 15, the lower end of the first concentrate passage 3, the lower end of the second concentrate passage 11, and the lower end of the first cooling water passage 7 are connected by a connecting pipe 16,
The upper end of the stock solution passage 11 is connected to a stock solution discharge pipe 17. Further, a condensate outlet branch pipe is connected to the lower end of the steam space 5, 120 of each stage, and is commonly connected to form one condensate outlet pipe.

The porous membranes constituting the membrane tubes 2 and 8 must have no affinity for high-temperature stock solutions; for example, if the stock solution is an aqueous solution, it must be hydrophobic; It is necessary to have the property of not allowing the vapor to pass through, but allowing the vapor to pass through. Furthermore, since the stock solution is heated, heat resistance is also required.

Therefore, when the stock solution is an aqueous solution, a porous membrane made of a fluororesin such as polytetrafluoroethylene resin is particularly preferred since it has both heat resistance and hydrophobicity. but,
For example, even if a porous membrane is made of a hydrophilic resin such as polysulfone resin or cellulose resin, when the surface is coated with a water-soluble resin such as a fluororesin or silicone resin to provide a hydrophobic porous membrane surface. These resin films can also be used.

The heat transfer tubes 4 and 9 are preferably thin-walled tubes made of a material with high heat conductivity, such as metal, but may be made of plastic as long as the heat transfer body has a heat transfer rate faster than the heat transfer rate due to vapor diffusion.

The membrane tube 2.8 is formed by supporting a porous membrane on a support tube. In this case, the support tube only needs to be able to permeate liquid vapor, and for example, a woven or nonwoven fabric tube made of polyamide, fluororesin, etc., or a porous ceramic membrane tube is preferably used.

FIG. 3 schematically shows the flow of the stock solution in the above example. The stock solution is introduced through the membrane tube to the extent that the amount condensed and discharged is sufficiently replenished, but any overflow is discharged from the discharge tube 17. The temperature of each part is the lowest in the second cooling water passage 13, for example 15 to 20°C, the second lowest in the first cooling water passage 7, for example 25 to 30°C, and the temperature in the first stock liquid passage in the center. 3 is the highest, for example, 80 to 90°C, and the second stock solution 1Jtl path 11 is the second highest, for example, 50 to 60°C.

In this state, only the vapor of the high-temperature raw solution passes through the membrane tube and diffuses into the vapor space, is cooled on the surface of the heat transfer tube, is condensed and liquefied, and is taken out from the condensate extraction tube. Further, the solute in the stock solution is blocked together with the solvent by the membrane tube, concentrated, and discharged from the stock solution discharge pipe.

In this example, an apparatus with a membrane area of 0.25 m was used,
When tap water with a conductivity of 180 μS/C11 was used as the stock solution, a permeate with a conductivity of 1.2 μS/cffi was obtained at 2.3 A/h per 1.5 kWh of heat input. FIG. 4 shows a model diagram of an embodiment of the three-stage configuration of the present invention.

In the figure, the right end corresponds to the center and the left end corresponds to the outer periphery. The stock solution flow path is not limited to that of the embodiment, and can be modified in various ways.

<Effects of the Invention> According to the present invention, the solution is separated and concentrated by heating the stock solution and passing the vapor through a membrane, so unlike the conventional reverse osmosis method, there is no need to pressurize the stock solution to a high pressure. Moreover, it has extremely good solute blocking performance. Moreover,
Since the heat transfer tube is immersed in the center of the stock solution flow path, there is no need for a heat insulation device and there is almost no heat loss.

Further, since the structure is multi-stage, a large amount of permeate can be recovered, and heat exchange is performed at each stage, so the amount of condensed liquid per amount of heat input increases.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, and FIG. 2 is a cross-sectional view thereof. FIG. 3 is a model diagram showing the stock solution flow path in the above embodiment, and FIG. 4 is a model diagram showing the stock solution flow path in another embodiment of the present invention. 1... Heater 2.8... Membrane tube 3.11... Stock solution passage 4.9... Heat transfer tube 5.12... Evaporation space 6.10... Partition tube 7.13. ... Cooling water passage 14 ... Stock solution introduction pipe 17 ... Stock solution discharge pipe 18 ... Condensate extraction pipe

Claims (2)

[Claims] (1) A heater provided at the axial center, and a membrane tube formed with a polymeric porous membrane that forms a concentrate passage around the heater and does not allow the concentrate to pass through, but allows the vapor of the concentrate to pass through. , a heat exchanger tube that forms a vapor space around the membrane tube, a partition tube that forms a cooling heat medium passage around the heat exchanger tube, a raw solution passage, a membrane tube, a heat exchanger tube, and a partition around the outer periphery of the partition tube. tubes are provided repeatedly on the same axis, and the concentrate is discharged through the concentrate passage around the heater after being used as a heating medium for cooling;
A membrane distillation apparatus configured so that the condensate condensed in the vapor space is led to the outside. (2) The undiluted liquid is first introduced into the outermost cooling heat medium passage, and the undiluted liquid whose temperature has risen due to the heat exchange is used as a cooling heat medium closer to the center, and then introduced into the undiluted liquid passage. A membrane distillation apparatus constructed as claimed in claim 1.