Heat and material exchanger

This application is the U.S. national phase of International Application No. PCT/FR2019/051812 filed Jul. 18, 2019 which designated the U.S. and claims priority to FR Patent Application No. 1856934 filed Jul. 25, 2018, the entire contents of each of which are hereby incorporated by reference.

BACKGROUND

The invention relates to a heat and material exchanger.

Known in the prior art of heat and material exchangers in particular are exchangers using direct contact between a sprayed liquid and a gas. This type of exchanger allows effective exchange of heat and of material but has a major disadvantage linked to the entrainment of liquid drops in the gas flow. This entrainment of drops constitutes a risk when the liquid is toxic or corrosive.

Also known are exchangers allowing an indirect exchange in which the flow is separated by membranes permeable to the vapor and impermeable to the liquid. The implementation of such exchangers is delicate, due to the static pressure of the liquid flowing in the pipe formed by the membranes. This pressure can cause sealing problems and requires membranes having particular mechanical properties contradictory with permeability to the vapor which make them ineffective and costly to manufacture.

The invention proposes a heat and material exchanger which does not have the disadvantages of those of the prior art.

OBJECT AND SUMMARY OF THE INVENTION

The invention relates to an exchanger including:substantially parallel and vertical membranes, permeable to vapor and impermeable to a liquid, these membranes delimiting zones, each of these zones belonging alternately to a first type of zone or to a second type of zone;the zones of the first type including in the upper portion a spray nozzle configured to spray a liquid along a plane substantially parallel to the membranes, and in the lower portion a first liquid collector, independent and separated from the zones of the second type, anda first pipe arranged to supply the spray nozzles of the zones of the first type with said liquid.

In a particular embodiment of the invention, the membranes are of polypropylene or of polyamide.

In conformity with the invention, the liquid can be an aqueous solution more or less rich in salt, or salt-free.

In a first embodiment, the exchanger according to the invention includes a passage allowing the circulation of a gas in the zones of the second type.

In a particular arrangement of this first embodiment, the exchanger according to the invention includes a fan allowing improving the circulation of the gas in the zones of the second type.

The invention also relates to a method for using an exchanger according to this first embodiment, this method including:a step of circulating a relatively hot and humid gas in the zones of the second type;a step of circulating a relatively cold and salt-rich liquid in the first pipe, this liquid being sprayed by the spray nozzles in the zones of the first type; anda step of collecting a warmed and diluted liquid in the first collector.

The invention relates to another method for using an exchanger according to the first embodiment of the invention, this method including:a step of circulating a relatively cold gas in the zones of the second type;a step of circulating a relatively hot and salt-poor liquid in the first pipe, this liquid being sprayed by the spray nozzles in the zones of the first type; anda step of collecting a cooled and concentrated liquid in the first collector.

In these two methods, the spray nozzles disperse the liquid at a pressure identical to that of the gas in the zones of the first type. The gas which circulates in the adjacent zones of the second type is heated and saturated with vapor when the liquid is hotter than the gas and when its vapor pressure is greater than that of the gas.

In the reverse case, if the liquid is colder than the gas and its vapor pressure is lower than that of the gas, the gas is cooled and its vapor concentration is reduced.

The liquid, (or solution) after the exchange, cooled and concentrated or heated and diluted, is collected in a collector arranged so that there is no contact between the liquid and the gas.

In a second embodiment of the exchanger according to the invention:the zones of the second type include in the upper portion a spray nozzle configured to vaporize a liquid along a plane substantially parallel to the membranes, and in the lower portion a collector, independent and separated from the zones of the first type; anda second pipe supplying the spray nozzles of the zones of the second type with a liquid.

In this second embodiment, the exchange of mass and of heat occurs between two liquids separated by the membranes.

The invention also relates to a method of using an exchanger according to this second embodiment. This method includes:a step of circulating a relatively cold and salt-poor liquid in the first pipe, this liquid being sprayed by the spray nozzles in the zones of the first type;a step of circulating a relatively hot and salt-rich liquid in the second pipe, this liquid being sprayed by the spray nozzles in the zones of the second type;a step of collecting a warmed and diluted liquid in the first collector in the lower portion of the zones of the first type; anda step of collecting a cooled and concentrated liquid in the second collector in the lower portion of the zones of the second type, this second collector being separated from the first collector to prevent mixing of the collected liquids.

In this embodiment, the hot and diluted solution is concentrated by surrendering its heat and some vapor to the second, cold solution which is warmed and diluted.

Generally, the invention thus proposes an exchanger of heat and mass between a liquid and a gas or between two liquids through a membrane, the heat and mass exchange being due to a difference of temperature and a difference of vapor pressure between the two fluids. The permeability of the membrane to the vapor of the liquid solvent allows the transfer of vapor between the two fluids.

Thus, the expressions “hot,” “cold,” “diluted,” “concentrated,” “salt-rich,” “salt-poor” must be understood in a relative sense, for expressing the differences between the state of the fluids on either side of the membranes to allow the exchanges of heat and mass between the zones of the first and second type, and not in an absolute sense.

The invention can in particular be used for:concentrating or diluting a solution by the evaporation or condensation of vapor with no gap in total pressure on either side of a membrane permeable to the solvent vapor;dehydrating or humidifying a gas by exchange with a cold and concentrated solution or a hot and diluted solution without entering into contact with the solution.

FIRST EMBODIMENT

FIG.1shows an exchanger100conforming to a first embodiment of the invention. It can be used to refresh and dehumidify hot and humid air (for example 25° C. and 60% RH) circulating in the zones Z30delimited by membranes30permeable to water vapor. A fan40can be used for blowing the hot air.

In the embodiment described here, a zone Z20with a spray nozzle over it is located on either side of each air circulation zone Z30. These spray nozzles20are supplied by a pipe10in which a cold (typically 15° C.) and salt-rich liquid circulates. The spray nozzles20spray the liquid substantially into a flat sheet R parallel to the membranes30.

In this embodiment of the invention, like in those described hereafter, the liquid supply pressure upstream of the nozzles can be on the order of 2 bars.

When the salt-rich liquid is sprayed by the spray nozzles20in the zones Z20, the air comprised in these zones Z20surrenders its humidity which is absorbed by the salt. It becomes colder and drier than the air in the zones Z30.

The air in the zones Z30cools and its humidity migrates toward the zones Z20through the membranes30, as shown by the horizontal arrows. The liquid in the zones Z20is diluted; it is recovered in a collector50arranged so that the liquid collected is not in contact with the zones Z30.

In this embodiment:the more the liquid sprayed by the spray nozzles20is concentrated with salt, the more the dehumidification of the hot and humid air in the zones Z30is favored; andthe more the liquid sprayed by the spray nozzles20is cold, the more the cooling of the air circulating in the zones Z30is favored.

SECOND EMBODIMENT

FIG.2shows an exchanger200conforming to a second embodiment of the invention. It can be used to cool and concentrate a hot and salt-poor, or even salt-free liquid.

In the embodiment described here, this liquid (at 35° C. for example) is sprayed by the spray nozzles21in zones Z21delimited by membranes permeable to water vapor, the spray nozzles being supplied by a pipe11. The spray nozzles21spray the liquid substantially in a flat sheet R parallel to the membranes30.

As in the first embodiment, the zones Z21are separated by zones Z30in which air circulates. But in this embodiment, the air in these zones Z30is colder than the liquid sprayed in the zones Z21. The air in the zones Z30is for example at ambient temperatures, for example at 24° C.

In the zones Z21, the air, in contact with the hot sprayed liquid, is warmed and charged with humidity. The liquid cools and is concentrated. It is collected in a collector51arranged so that the liquid collected is not in contact with the zones Z30.

The water vapor migrates from the zones Z21to the zones Z30through the membranes30as shown by the horizontal arrows. In the zones Z30, the air is warmed and is charged with humidity.

This second embodiment of the invention advantageously allows cooling the liquid below the temperature of the air circulating in the zones Z30, thanks to the phenomenon of evaporation, until it attains the wet-bulb temperature.

THIRD EMBODIMENT

FIGS.3and4show a third embodiment of the invention. It can be used to desalinate a liquid.

In this embodiment, the exchanger300includes:a pipe10supplying the spray nozzles20with a cold salt-poor, or even salt-free liquid, this liquid being sprayed by the spray nozzles20in the zones Z20; anda pipe11supplying the spray nozzles21with a hot, concentrated salt liquid, this liquid being sprayed by the spray nozzles21in the zones Z21.

The zones Z20and Z21are alternated and separated by membranes30permeable to water vapor. In each of the zones, the spray nozzles20,21spray the liquid in a flat sheet R substantially parallel to the membranes.

In the zones Z21, the air in contact with the hot liquid is warmed and is charged with humidity. The water vapor migrates toward the zones Z20through the membranes30.

In the zones Z20, the air is warmed and is charged with water vapor due to the migration of water vapor coming from the zones Z21as shown by the horizontal arrows.

In the zones Z20, the air surrenders its heat to of the flow of cold, salt-poor liquid increasing the quantity of water. The hot and diluted liquid is collected in a collector50arranged so that this liquid is not in contact with the zones Z21.

In the zones Z21, the quantity of water is reduced due to the migration, and the salt-rich liquid is concentrated. The cold and concentrated liquid is exhausted by U-shaped pipes leading through openings61into a collector51arranged so that this liquid is not in contact with the zones Z20.

This embodiment allows concentrating the salt-rich liquid introduced into the pipe11: it can be used for desalination operations.

In this third embodiment of the invention, the exchanger300has a structure7to which the membranes30are attached. The collectors50and51have shoulders in which these membranes30are inserted, thus avoiding any contact between the different liquids.

An arrangement of this type can also be used in the exchangers100and200described previously with reference toFIGS.1and2to avoid contact between the liquid in the collectors50,51and the air circulating in the zones Z30.

OTHER USE EMBODIMENT OF THE INVENTION

As previously mentioned, in the embodiment ofFIG.1, the solution recovered in the collector50is diluted by the water vapor which has migrated from the zones Z30through the membrane30. It is necessary, to be able to re-use it at the input to the pipe10, to remove the water added to it.

To carry out this operation, it is possible to head the diluted solution recovered in the collector50and to inject it into the pipe11of the exchanger ofFIG.2in order to reduced its temperature and to concentrate it.