JPS6233504A - Membrane distillation apparatus - Google Patents

Abstract

PURPOSE:To prevent wasteful heat release and improve the heat efficiency without providing a heat insulating device and to facilitate the exchange and cleaning of the membranous tube by providing a heater at the central part of the heat-transfer tube and making the membranous tube part freely attachable and detachable. CONSTITUTION:A cooling heat medium passage 5 is formed between a cylindrical outer tube 1 and a heat-transfer tube 2 on the inside, the upper end surface of the outer tube 1 is closed by a top plate 14 and the lower end surface is opened. A rod-like heater 4 with the upper end supported by the top plate 14 and the free lower end is provided at the central part of the heat-transfer tube 2. A bottom plate 15 for closing the lower opening surface of the outer tube 1 is fixed by a flange coupling, etc., and made freely attachable and detachable to and from the outer tube 1 and the heat-transfer tube 2. A tube 13 for supporting the membranous tube 3 with close attachment is furnished on the bottom plate 15, the inside of the membranous tube 3 is used as a raw liq. passage 7 and the outside is used as an evaporation space 6. When the fixing means of the bottom plate 15 is released, the membranous tube 3 and a spacer 16 can be taken out from the outer tube 1 along with the bottom plate 15 and the membranous tube 3 can be easily exchanged.

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 concentrating a solution by N, a high temperature liquid to be treated, that is, a stock liquid such as hot sea water, is placed on the primary side of a porous polymer membrane that allows liquid vapor to pass through but not the liquid itself. The thermopar is used to circulate vapor generated from the raw solution and permeated through the porous membrane on the secondary side to be cooled and condensed, thus concentrating the raw liquid on the downstream side and obtaining a condensed liquid on the secondary side. Vaporization is already known, and various devices for it have been proposed.

For example, in Japanese Patent Publication No. 49-45461, a large number of membrane walls and a large number of heat transfer walls extending in the vertical direction are provided parallel to each other with a space between them, and two adjacent I!
! ! There is a high-temperature liquid passage between the membrane walls, a cooling water passage between two adjacent heat transfer walls, and a passage for generated steam and distilled water between the adjacent membrane walls and heat transfer walls. A device is described which defines a steam space and further defines cooling water passages between a heat transfer wall and a side wall at both ends of the device body.

<Problems to be Solved by the Invention> According to such conventional devices, the high-temperature stock solution is heated by a heat exchanger installed outside and then introduced into the device in parallel, so the thermal efficiency due to heat radiation during introduction is low. There was a problem that a decrease in the amount of water was inevitable.

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 such a membrane distillation apparatus with good thermal efficiency, in which membrane tubes can be easily replaced or cleaned.

Means for Solving the Problems> In the membrane distillation apparatus of the present invention, a cooling heat medium passage is formed by an outer tube and a heat transfer tube provided inside the outer tube, and one end surface of the heat transfer tube is is opened and the other end is closed with a first end plate, and a heater is provided in the center of the heat exchanger tube, and the vapor of the undiluted solution is kept between the surface of the heater and the inner surface of the heat exchanger tube without allowing the undiluted solution to pass through. A membrane tube made of a porous polymer membrane is provided, and one end surface of the membrane tube is closed with a second end plate, and the liquid solution is passed through the liquid flow path between the membrane tube and the heater. A condensate solution for taking out the condensate generated in the evaporation space between the membrane tube and the heat transfer tube to the outside, by providing a condensate inlet tube and a condensate outlet tube on either the first or second end plate, respectively. It is characterized in that a lead-out tube is provided on the second end plate, and the membrane tube is configured to be detachably attached to the heat exchanger tube.

<Example> FIG. 1 shows a longitudinal cross-sectional view of an example of the present invention, and FIG. 2 shows a cross-sectional view thereof.

The outer tube 1 has a cylindrical shape, and has a cooling water outlet 9 at its lower end and a cooling water outlet 8 at its upper end. A heat pipe 2 is provided, and a cooling heat medium flow path 5 is formed between the heat pipe 2 and the outer pipe.

The upper end surface of the outer tube 1 is closed with a top plate 14, and the lower end surface is open. A rod-shaped heater 4 whose upper end is supported by a top plate 14 and whose lower end is a free end is provided at the center of the heat exchanger tube 2 .

A bottom plate 15 that closes the opening surface of the lower end of the outer tube 1 is detachably fixed to the lower end portions of the outer tube 1 and the heat transfer tube 2. As this fixing means, a known technique such as a flange joint or a threaded joint can be used. A membrane support tube 13 is provided on the bottom plate 15, and the membrane tube 3 is closely supported by the support tube 13. The inside partitioned by this membrane tube 3 becomes the stock solution flow path 7,
The outside becomes an evaporation space 6. A stock solution inlet pipe 10 is provided at the upper end of the stock solution channel 7, and a stock solution outlet pipe 11 is provided at the lower end.
A condensate outlet pipe 12 is provided at the lower end of the evaporation space 6 . Further, a spacer 16 is provided on the outer periphery of the membrane tube 3.

The porous membrane constituting the membrane tube 3 needs to have no affinity for high-temperature stock solutions; for example, if the stock solution is an aqueous solution, it must be hydrophobic; furthermore, it must not allow the stock solution to pass through; , it is necessary that the vapor has the property of being permeable. 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.

However, even if the porous membrane is made of a hydrophilic resin such as polysulfone or cellulose resin, the surface of the porous membrane may be coated with a water-repellent resin such as a fluororesin or silicone resin to provide a hydrophobic porous membrane surface. In some cases, these resin films can also be used.

The heat transfer tube 2 is desirably a thin-walled tube made of a material with high heat conductivity, such as metal, but may be made of plastic as long as it is a heat transfer body that has a faster heat transfer rate than the heat transfer rate due to vapor diffusion.

The membrane tube 3 is formed by supporting a porous membrane on a support tube 13. In this case, the support tube only needs to be able to transmit liquid vapor, and for example, a woven or nonwoven fabric tube made of polyamide, fluororesin, etc., or a porous tube made of ceramic is preferably used.

In a variant embodiment of the invention, a circulation device or a stirring device may be provided to bring the stock solution into efficient contact with the membrane 3.

In the device of the present invention, the undiluted solution held in the membrane tube is heated by the heater, and only the vapor passes through while the undiluted solution is blocked by the membrane tube, and the vapor diffuses through the vapor space and is cooled on the surface of the heat transfer tube. , the steam condenses and is led out of the device via a condensate outlet pipe.

In addition, the solute in the stock solution is blocked together with the liquid by the membrane tube,
It is concentrated in the membrane tube. Therefore, for example, when seawater is used as the stock solution, the salts contained in the seawater are blocked by the membrane tube, and only water vapor passes through the membrane, so the seawater is concentrated in the membrane tube and distilled water can be obtained on the condensate side. can.

It goes without saying that the present invention can be applied to the separation and concentration of solutions containing organic substances as well as aqueous solutions containing inorganic salts such as seawater.

FIG. 3 shows a partially cutaway view of the membrane tube 3 taken out.

When the fixing means is removed, the membrane tube 3 and spacer 16 can be pulled out together with the bottom plate 15 from the outer tube, and the membrane tube 3 can be easily replaced.

<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! @There is almost no loss.

Further, since the membrane tube portion is detachable, the membrane tube can be easily replaced with a new one in a short time or can be cleaned.

[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 an explanatory diagram of the operation of the above embodiment. 1... Outer tube 2... Heat transfer tube 3... Membrane tube 4... Heater 5... Cooling heat medium channel 6... Evaporation space 7... Stock solution channel 13...・Membrane support tube 14...Top plate 15...Bottom plate

Claims (1)

[Claims] A cooling heat medium passage is formed by an outer tube and a heat transfer tube provided inside the outer tube, and one end surface of the heat transfer tube is opened and the other end surface is closed with a first end plate, and the heat transfer tube is closed. A heater is provided in the center of the heat exchanger tube, and a membrane tube made of a porous polymer membrane that does not allow the undiluted solution to pass through but allows the vapor of the undiluted solution to pass through is provided between the surface of the heater and the inner surface of the heat transfer tube. One end surface of the tube is closed with a second end plate, and a stock solution introduction pipe and a stock solution outlet pipe for passing the stock solution into the stock solution flow path between the membrane tube and the heater are connected to the first or second end plate, respectively. A condensate discharge pipe for taking out the condensate generated in the evaporation space between the membrane tube and the heat transfer tube to the outside is provided on the second end plate, and the membrane tube is connected to the heat transfer tube. A membrane distillation device configured to be detachable from the heat tube.