Apparatus for drying and/or cooling gas

The invention relates to an apparatus (10) for drying and/or cooling gas (12), in particular air, by means of a hygroscopic solution (14), said apparatus comprising an absorption device (16) which comprises at least one gas flow duct (18) and at least one flow duct (20) carrying the hygroscopic solution, wherein the inner or gas chamber (22) of a respective gas flow duct is at least partly delimited by a vapor-permeable liquid-tight membrane wall (24) and at least one flow duct is provided, which is formed between such a gas flow duct and a further such gas flow duct adjacent to the latter or an adjacent cooling unit (26) and which carries the hygroscopic solution, so that moisture, in particular water vapor, passes from the gas into the hygroscopic solution via the membrane wall and is absorbed in said solution.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a 35 U.S.C. §371 U.S. national entry of International Application PCT/EP2011/004967 (WO 2012/055477) having an International filing date of Oct. 5, 2011, which claims under 35 U.S.C. §119 the benefit of German Patent Application No. 10 2010 050 042.9, filed Oct. 29, 2010. The entire contents of both applications are incorporated herein by reference in their entirety.

The invention relates to an apparatus for drying and/or cooling gas, in particular air, by means of a hygroscopic solution. Such an apparatus can be used, for example, in air conditioning plants or the like.

Hygroscopic solutions have the property of binding moisture from the environment. A corresponding hygroscopic solution can comprise, for example, an aqueous saline solution of in particular lithium chloride, lithium bromide, calcium chloride, one of the newly developed, so-called ionic solutions and/or the like. The absorption capability of such a solution increases inter alia as the temperature drops.

It is the object of the invention to provide an improved apparatus of the initially named kind which ensures a drying performance or cooling performance which is as high as possible with a design which is as simple and compact as possible.

This object is satisfied in accordance with the invention by an apparatus for drying and/or cooling gas, in particular air, by means of a hygroscopic solution, having an absorption device which comprises at least one gas flow passage as well as at least one flow passage conducting the hygroscopic solution, wherein the inner space or gas space of a respective gas flow passage is bounded at least partly by vapor-permeable, liquid tight membrane wall and at least one flow passage is provided which conducts the hygroscopic solution and is formed between such a gas flow passage and a further such gas flow passage adjacent thereto or an adjacent cooling unit so that moisture, in particular water vapor, in transferred from the gas via the membrane wall into the hygroscopic solution and is absorbed therein.

The apparatus can be kept relatively simple and compact with a relatively large drying performance and cooling performance due to this design. In particular a larger number of gas flow passages can also be provided without problem, whereby the performance capability can be correspondingly further increased.

The hygroscopic solution flows through the absorption device, preferably in counterflow to the gas.

The absorption device can in particular comprise a plurality of gas flow passages in parallel with one another as well as a plurality of flow passages in parallel with one another and conducting the hygroscopic solution.

The flow passages of the absorption device conducting the hygroscopic solution can, for example, respectively be formed between two mutually adjacent gas flow passages.

Those embodiments are, however, also conceivable in which the flow passages of the absorption device conducting the hygroscopic solution are respectively formed between a gas flow passage and an adjacent cooling unit. A respective cooling unit in this respect preferably comprises a cooling fluid space at least partly bounded by a fluid-tight, heat-conducting cooling fluid space.

In accordance with a preferred practical embodiment of the apparatus in accordance with the invention, the hygroscopic solution exiting the absorption device is supplied to a regeneration device in which it is regenerated. The regenerated hygroscopic solution can then again be supplied to the absorption device.

The regenerated hygroscopic solution can be supplied to the absorption device via a cooler. The absorption capability of the hygroscopic solution reused in the absorption device is further increased by the additional cooling.

The gas exiting the absorption device is preferably supplied to a consumer.

In particular with a consumer with little gas loss, the gas coming from the consumer can be supplied to the regeneration device. It can be of advantage in this respect if the gas coming from the consumer is supplied to the regeneration device via a heat exchanger in which the gas is preferably heated.

Whereas the gas moisture increases again in the consumer, for example, the relative humidity is reduced again by such a heat exchanger.

In specific cases, however, it can also be of advantage if the gas coming from the consumer is led off as exhaust gas or exhaust air.

In this case, gas not coming from the consumer, for example, in particular inflow air such as environmental air, can be supplied to the regeneration device. The regeneration device can, however, generally also be operated without any supplied gas.

If the regeneration device is flowed through by a gas, it is advantageous if the hygroscopic solution flows through the regeneration device in counterflow to the gas.

In accordance with a preferred practical embodiment of the apparatus in accordance with the invention, the regeneration device comprises at least one gas flow passage as well as at least one flow passage conducting the hygroscopic solution, with the inner space or gas space of a respective gas flow passage being at least partly bounded by a vapor-permeable, liquid-tight membrane wall and at least one flow passage being provided which conducts the hygroscopic solution and is formed between such a gas flow passage and a further such gas flow passage adjacent thereto or an adjacent heating unit so that moisture, in particular water vapor, is transferred into the gas from the hygroscopic solution via the membrane wall and the hygroscopic solution is concentrated.

In this respect, the regeneration device advantageously comprises a plurality of gas flow passages in parallel with one another as well as a plurality of flow passages in parallel with one another and conducting the hygroscopic solution.

In this respect, it can be of advantage in specific cases if the flow passages of the regeneration device conducting the hygroscopic solution are respectively formed between two mutually adjacent flow passages.

Such embodiments are, however, also conceivable in which the flow passages of the regeneration device conducting the hygroscopic solution are respectively formed between a gas flow passage and an adjacent heating unit.

A further preferred practical embodiment of the apparatus in accordance with the invention is characterized in that the regeneration device has at least one condensation/evaporation stage which is flowed through by the hygroscopic solution exiting the absorption device and which comprises at least one condensation unit and at least one evaporator unit, with a respective condensation unit comprising a first vapor space at least partly bounded by a condensation wall and a respective evaporator unit comprising a second vapor space at least partly bounded by a vapor-permeable, liquid-tight membrane wall and with at least one flow passage being provided which conducts the hygroscopic solution and is formed between such a condensation unit and such an evaporator unit adjacent thereto so that the hygroscopic solution is heated via the condensation wall and the vapor arising from the hygroscopic solution arrives through the membrane wall in the second vapor space.

In this respect, the regeneration device expediently has a heating stage which is flowed through by the hygroscopic solution exiting the condensation/evaporation stage and which comprises at least one heating unit and at least one evaporator unit, with a respective heating unit comprising a heating fluid space at least partly bounded by a fluid-tight, heat-conducting wall and a respective evaporator unit comprising a vapor space at least partly bounded by a vapor-permeable, liquid-tight membrane, with at least one flow passage being provided which conducts the hygroscopic solution and is formed between a heating unit and an evaporator unit adjacent thereto so that the hygroscopic solution is heated via the fluid-tight, heat-conducting wall and the vapor arising from the hygroscopic solution arrives through the membrane wall in the vapor space and the vapor arising in this vapor space is preferably supplied to a condensation unit of the condensation/evaporation stage.

The regeneration device preferably comprises a condensation stage having at least one cooling unit and at least one condensation unit, with a respective cooling unit comprising a cooling fluid space at least partly bounded by a fluid-tight, heat-conducting wall and a respective condensation unit comprising a vapor space at least partly bounded by a condensation wall and with at least one cooling unit being directly adjacent to at least one condensation unit in the condensation stage so that the condensation wall of the respective condensation unit is cooled via the cooling unit. In this respect, vapor arising in a preceding condensation/evaporation stage is preferably supplied to the condensation stage.

If the regeneration devices comprises the previously mentioned system of at least one condensation/evaporation stage, heating stage and preferably also condensation stage, this system is preferably in a vacuum, the cooling fluid and the heating fluid are preferably at environmental pressure and the hygroscopic solution is preferably in a vacuum. In the condensation stage(s)/evaporation stage(s) and in the heating stage, the hygroscopic solution can in particular be at the boiling temperature corresponding to the absolute pressure in the vapor space of a respective adjacent evaporator unit over all stages, as is described in WO 2007/054311 which is herewith included in the disclosure content of the present application.

A respective heating unit of the heating stage can be flowed through by a heating fluid which is, for example, heated by solar power.

The vapor entering into a respective condensation unit of the condensation/evaporation stage condenses at the condensation surfaces. The corresponding heat is transferred to the hygroscopic solution via the respective surface. The vapor arising therein passes through the membrane of the adjacent evaporator unit into its vapor space which communicates with the pressure of the vapor space of the respective condensation unit of the following condensation/evaporation stage in the case of a plurality of condensation stages/evaporation stages.

In accordance with a preferred practical embodiment of the apparatus in accordance with the invention, it is designed as a modular flow system having a plurality of frame elements. In this respect, the different functional units such as in particular a respective gas flow passage, a respective cooling unit, a respective heating unit, a respective condensation unit and/or a respective evaporator unit are each provided in the form of such a frame element.

The frame elements are preferably provided with web structures via which they can in particular be connected to one another for forming the absorption device, the regeneration device, a respective condensation/evaporation stage, the heating stage and/or the condensation stage.

The frame elements can each comprise an inner region which is surrounded by an outer frame and which is preferably provided with an in particular grid-like spacer to whose two sides a respective corresponding functional surface, preferably in the form of a film or membrane, is in particular applied for forming a respective inner space or gas space, a respective vapor space, a respective heating fluid space or a respective cooling fluid space.

The web structures via which the individual frame elements can be connected to one another can, for example, be welded web structures or bonded structures via which the frame elements are welded or bonded to one another. In the case of welded web structures, a friction welding process, a laser welding process and/or a heating element welding process can be used, for example, for connecting the frame elements.

The gas drying apparatus and/or gas cooling apparatus can be designed in a particularly simple manner and can be varied in the desired manner using the frame elements in accordance with the invention. The frame elements or the units or stages obtained via them are characterized by a relatively simple form and provide different possibilities of the gas supply or air supply, cooling fluid supply and heating fluid supply. The respective drying processes and/or cooling processes as well as the regeneration processes can, for example, be realized only with membrane frame elements or with a combination of membrane frame elements and film frame elements, with frame elements also being conceivable which are provided with a membrane on the one side and with a film on the other side.

Mutually corresponding parts have the same reference numerals associated with them in the different Figures.

FIGS. 1 to 3show in a schematic representation a respective exemplary embodiment of an apparatus10for drying and/or cooling gas12by means of a hygroscopic solution14, with the gas12being able to be air, for example.

In this respect, the apparatus10comprises an absorption device16having at least one gas flow passage18as well as at least one flow passage20conducting the hygroscopic solution14. In this respect, the inner space or gas space22of a respective gas flow passage18is at least partly bounded by a vapor-permeable, liquid-tight membrane wall24.

At least one flow passage20is provided which conducts the hygroscopic solution (14) and is formed between such a gas flow passage18and a further such gas flow passage18adjacent thereto (cf.FIGS. 1 and 2) or an adjacent cooling unit26(cf.FIGS. 3 and 4) so that moisture, in particular water vapor, is transferred from the gas12via the membrane wall24into the hygroscopic solution18and is absorbed therein.

In this respect, the hygroscopic solution14can flow through the absorption device16in counterflow to the gas12.

The absorption device16can comprise a plurality of gas flow passages18in parallel with one another as well as a plurality of flow passages20in parallel with one another and conducting the hygroscopic solution14.

As can be seen fromFIGS. 1 and 2, the flow passages20of the absorption device16conducting the hygroscopic solution14can respectively be formed between two mutually adjacent gas flow passages18.

However, in particular such embodiments are also conceivable in which the flow passages20of the absorption device16conducting the hygroscopic solution are respectively formed between a gas flow passage18and an adjacent cooling unit26(cf.FIGS. 3 and 4). In this respect, a respective cooling unit26preferably comprises a cooling fluid space54at least partly bounded by a fluid-tight, heat-conducting wall48.

The hygroscopic solution14exiting the absorption device16can be supplied to a regeneration device28in which it is regenerated. The regenerated hygroscopic solution14is then preferably again supplied to the absorption device16.

As can be seen fromFIGS. 1 and 2, the regenerated hygroscopic solution14can in particular be supplied to the absorption device16via a cooler30.

The gas12exiting the absorption device16can be supplied to a consumer32.

It is of advantage in specific cases if the gas12coming from the consumer32is supplied to the regeneration device28(cf.FIGS. 1 and 2).

In this respect, the gas12coming from the consumer32can be supplied to the regeneration device28via a heat exchanger34in which the gas12is preferably heated.

The gas12coming from the consumer32can, however, also be led off as exhaust gas or exhaust air (cf.FIGS. 3 and 4).

In this respect gas12′ not coming from the consumer32, in particular inflow air such as environmental air, can be supplied to the regeneration device28, for example (cf.FIG. 3). Such embodiments are, however, also conceivable in which the regeneration device28is not flowed through either by gas coming from the consumer32or by gas not coming from the consumer (cf.FIG. 4, for example).

In the event that the regeneration device28is flowed through by gas, the hygroscopic solution14can in particular flow through the regeneration device28in counterflow to the gas12,12′ (cf.FIGS. 1 to 3).

As can in particular again be seen fromFIGS. 1 to 3, the regeneration device28can comprise at least one gas flow passage18as well as at least one flow passage20conducting the hygroscopic solution14, with the inner space or gas space22of a respective gas flow passage18being at least partly bounded by a vapor-permeable, liquid-tight membrane wall24and with at least one flow passage being provided which conducts the hygroscopic solution14and is formed between such a gas flow passage18and such a further gas flow passage18adjacent thereto (cf.FIG. 1) or an adjacent heating unit36(cf.FIGS. 2 and 3) so that moisture, in particular water vapor, is transferred into the gas12or12′ from the hygroscopic solution via the membrane wall24and the hygroscopic solution14is concentrated.

In this respect, the regeneration device28can comprise a plurality of gas flow passages18in parallel with one another as well as a plurality of flow passages20in parallel with one another and conducting the hygroscopic solution14(cf.FIGS. 1 to 3).

In particular in the latter case, the flow passages20of the regeneration device28conducting the hygroscopic solution can respectively be formed between two mutually adjacent gas flow passages18(cf.FIG. 1). Such embodiments are, however, also conceivable in which the flow passages20of the regeneration device28conducting the hygroscopic solution14are respectively formed between a gas flow passage18and an adjacent heating unit36.

The regeneration device28can, for example, also have at least one condensation/evaporation stage38which is flowed through by the hygroscopic solution14exiting the absorption device16and which comprises at least one condensation unit K and at least one evaporator unit V (cf.FIG. 4).

In this respect, a respective condensation unit K comprises a first vapor space42at least partly bounded by a condensation wall40and a respective evaporator unit V comprises a second vapor space44at least partly bounded by a vapor-permeable, liquid-tight membrane wall24. In this respect, at least one flow passage20which conducts the hygroscopic solution14and is formed between such a condensation unit K and such an evaporator unit V adjacent thereto is provided in a respective condensation/evaporation stage38. The hygroscopic solution14is in this respect heated via the condensation wall40and the vapor arising from the hygroscopic solution14arrives through the membrane wall24in the second vapor space44.

In addition, the regeneration device28can have a heating stage46which is flowed through by the hygroscopic solution14exiting the condensation/evaporation stage38and which comprises at least one heating unit36and at least one evaporator unit V (cf.FIG. 4again).

In this respect, a respective heating unit36comprises a heating fluid space50at least partly bounded by a fluid-tight, heat-conducting wall48and a respective evaporator unit V comprises a vapor space44at least partly bounded by a vapor-permeable, liquid-tight membrane wall24. At least one flow passage20which conducts the hygroscopic solution14and is formed between a heating unit36and an evaporator unit V adjacent thereto is provided in the heating stage46so that the hygroscopic solution14is heated via the fluid-tight, heat-conducting wall48and the vapor arising from the hygroscopic solution14arrives through the membrane wall24in the vapor space44. The vapor arising in this vapor space44is preferably supplied to a condensation unit K of the condensation/evaporation stage38(cf.FIG. 4again).

As can likewise again be seen fromFIG. 4, the regeneration device28can also comprise a condensation stage52having at least one cooling unit26and at least one condensation unit K. In this respect, a respective cooling unit26has a cooling fluid space54at least partly bounded by a fluid-tight, heat-conducting wall48and a respective condensation unit K has a vapor space42at least partly bounded by a condensation wall40. At least one cooling unit26is directly adjacent to at least one condensation unit K in the condensation stage52so that the condensation wall40of the respective condensation unit K is cooled via the cooling unit26. Vapor arising in a preceding condensation/evaporation stage38is preferably supplied to this condensation unit K.

A respective apparatus10for drying and/or cooling gas can in particular be designed as a modular flow system having a plurality of frame elements (cf.FIGS. 5 to 7). In this respect, the different functional units such as in particular a respective gas flow passage18, a respective cooling unit26, a respective heating unit36, a respective condensation unit K and/or a respective evaporator unit V are each provided in the form of such a frame element. The frame elements are preferably provided with web structures56via which they can in particular be connected to one another for forming the absorption device16, the regeneration device28or a respective condensation/evaporation stage38, the heating stage46and/or the condensation stage38of the regeneration device28. The frame elements can each comprise an inner region60which is surrounded by an outer frame58and which is preferably provided with an in particular grid-like spacer62to whose two sides a respective corresponding functional surface, preferably in the form of a film or membrane, is in particular applied for forming a respective inner space or gas space22, a respective vapor space42,44, a respective heating fluid space50or a respective cooling fluid space54etc.

In this respect, a respective membrane can in particular take over the function of a membrane wall24and a respective film can in particular take over the function of a condensation wall40or of a fluid-tight, heat-conducting wall48.

The different frame elements can, for example, be welded or adhesively bonded to one another via the web structures. If, for example, welding web structures are used, a friction welding process, a laser welding process and/or a heating element welding process can be used for connecting the frame elements, for example.

FIG. 5shows in a schematic representation an exemplary embodiment of a frame element which can be used, for example, both as a cooling unit and as heating unit26and36respectively. The spacer62can in particular be provided with a respective film on both sides in the present case. The heating fluid space or cooling fluid space50or54respectively formed between the films is flowed through by heating fluid or cooling fluid, e.g. water. The heating fluid or cooling fluid is supplied to and again removed from the heating fluid space or cooling fluid space50and54respectively via passages64, for example water passages. The passages64are connected to leadthroughs66in particular provided in the corner regions of the frame element and in particular for the heating fluid or cooling fluid. Leadthroughs68are additionally in particular provided for the hygroscopic solution14in particular in the region of the leadthroughs66.

The leadthroughs66,68provided on the left hand side ofFIG. 5can be provided, for example, for a heating fluid inlet or cooling fluid inlet or for a solution inlet and the leadthroughs66,68provided on the right hand side ofFIG. 5can be provided, for example, for a heating fluid outlet or cooling fluid outlet or for a solution outlet. The inlet and outlet for the fluid or the solution respectively can, however, also generally be otherwise arranged. Parallel flows, counter flows or crossflows can be realized, for example, via these leadthroughs66,68.

The frame element is, for example, rectangular in cross-section in the present case. Generally, however, a square form is also conceivable, for example (cf.FIG. 7, for example).

The leadthroughs66can, for example, respectively be delineated toward the inner region60by a web section70.

The frame element in accordance withFIG. 5having films in particular provided at both sides can in particular also be provided as a condensation unit K, with in this case a corresponding vapor space44being able to be formed between the films.

FIG. 6shows in a schematic representation an exemplary embodiment of a frame element e.g. forming a gas flow passage, an air flow passage or an evaporator unit V. In the present care, a respective vapor-permeable, water-tight membrane can in particular be applied to both sides of the spacer62. The frame element can in particular be open toward the inner region60e.g. on the two narrow sides for forming a gas flow passage or an air flow passage.

Leadthroughs66,68as well as web sections70can also be recognized in the representation in accordance withFIG. 6.

This frame element shown inFIG. 6is also again rectangular in cross-section.

The films and membrane can, for example, be adhesively bonded or welded to the frame elements. A different kind of fastening of these films and membranes is generally also conceivable.

FIG. 7shows in a schematic representation an exemplary embodiment of a frame element square in cross-section. In this respect, in particular leadthroughs66,68can also again be recognized in this representation.

In the case of this frame element having a square cross-section, the leadthroughs66,68are arranged rotationally symmetrically. On a rotation by 90°, leadthroughs of the same function therefore always come to line on one another in plan view. Classical crossflow apparatus can also be designed using such an arrangement. Such a circuit is achieved by rotating the frame elements by 90°.

In another respect, this frame element can in particular again be designed such as was described with reference toFIGS. 5 and 6.

The different frame elements can therefore be arranged relative to one another according to the function to be satisfied. In this respect, for example, a frame element provided in the form of a condensation unit K can in particular be spanned by condensation film and a frame element provided in the form of an evaporator unit V can in particular be spanned by membrane. A respective flow passage20conducting the hygroscopic solution14results between the membrane and the film by the bringing together of a frame element provided in the form of a condensation unit K and provided with a film and of a frame element provided in the form of an evaporator unit V and provided with a membrane. A spacer can still be inserted in this flow passage20. Instead of such a spacer, the in particular grid-like spacer46can also be designed, for example, such that defined passages for conducting the solution are formed on the filling of the flow passage20.

As results fromFIG. 1, a heat and mass transfer device can be realized using membrane frame elements, for example. Moist and hot air can, for example, be sent through the heat and mass transfer device which is an air cooler and air dryer in one.

So much concentrated hygroscopic solution can, for example, be conducted in counterflow through the flow passage bounded by membranes and conducting the hygroscopic solution that the air or gas flowing over the membranes is both dried and cooled. The solution is in this respect diluted and heated. The cooled and dried air is supplied to the consumer, for example to a ship or the like. In the consumer the air is heated again by loads such as electrical consumers and persons and the air humidity is increased by the consumer or by the persons. The return air, which in particular almost corresponds to the inflow air in large ships such as cruise ships, can be heated in a heat exchanger so that the relative humidity drops. In the desorber or regeneration device, this air comes into contact with the diluted solution via the membrane. Water is now expelled from the diluted solution. The solution is concentrated and is cooled by the evaporation of the water. In an optional downstream cooler, the concentrated solution can be cooled even further and can be supplied to the absorption device again.

As can be seen fromFIG. 2, for example, the heat and mass transfer device or the absorption device can, for example, be realized using membrane frame elements and the regeneration device can, for example, be realized using membrane frame elements and film frame elements. The regenerator or desorber is here therefore made up of membrane frame elements and film frame elements. Warm water flows, for example through the film frame elements in the desorber or regeneration apparatus and heats the solution and expels water from the solution. The evaporation heat is here provided, for example, by cooling the hot water from the heating circuit. The air flowing in from the consumer is also heated via the heated solution and can take up moisture. The concentrated solution can be cooled via a cooler downstream of the desorber or regeneration device.

As can be seen fromFIG. 3, a cooled absorber or a cooled absorption device and a heated desorber or a heated regeneration device can be provided. Such a combination is in particular of advantage when outside air is respectively used for the absorber and the desorber in the respective plant. This is also a suitable process for a cold storage in a concentrated solution since a larger water charge of the solution can be achieved in the cooled absorber. The absorption and desorption can here also take place at separate locations. The concentrated solution could then be delivered to the consumer as a cold store. The diluted solution could then be returned.

As can be seen fromFIG. 4, a cooled absorber or a cooled absorption device can be provided in combination with a regeneration device which comprises a system serving for the concentration of the hygroscopic solution and having at least one condensation/evaporation stage as well as a heating stage and preferably a condensation stage. In this respect, the system within the broken line ofFIG. 4is in a vacuum. The cooling fluid and the heating fluid are at environmental pressure and the solution is in a vacuum. The circumstances are in this respect substantially as is described in WO 2007/054311. Such a combination is in particular efficient when no waste heat is available for the desorption of the solution. The energy requirement for the desorption can be considerably reduced over the number of different stages using a correspondingly multistage concentration process. It is also of particular advantage that distilled water arises in the desorption process, that is water is acquired from the moist air.

As can be seen fromFIGS. 2 and 3, a heat exchanger72can, for example, be provided in the respective heating fluid circuit of the regeneration device28.

As can be seen fromFIG. 4, cooling water74can, for example, be supplied to the condensation stage52or to its cooling units26. The heating fluid for the heating units36of the heating stage46can be heated by solar power, for example.

As can be seen fromFIGS. 3 and 4, for example, a cooler76can be associated with the cooling fluid circuit of the absorption device or of the cooled absorber.

Instead of air, any desired other gas can generally also be provided. In addition, water vapor does not necessarily have to be removed in the respective dehumidification. Any desired other mass transfer can also take place on the dehumidification.

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