CA2456522A1

CA2456522A1 - Method and apparatus for recovering water from atmospheric air

Info

Publication number: CA2456522A1
Application number: CA002456522A
Authority: CA
Inventors: Ronald King; Norman L. Arrison
Original assignee: G2T TECHNOLOGIES Inc
Current assignee: Individual
Priority date: 2004-01-30
Filing date: 2004-01-30
Publication date: 2005-07-30

Abstract

A method of separating water from air is provided comprising the steps of (a) contacting air having water vapour with an hygroscopic liquid mixture to produce a water rich hygroscopic liquid mixture, (b) heating at least a portion of the water rich hygroscopic liquid mixture to produce a gaseous mixture including water vapour and at least one other gaseous component, (c) condensing at least a portion of the water vapour in the gaseous mixture to produce liquid water and a depleted gaseous mixture at a first pressure, and (d) removing at least a portion of the at least one other gaseous component to maintain the first pressure below a predetermined pressure, wherein the depleted gaseous mixture is in fluid communication with the water rich hygroscopic liquid mixture. An absorber vessel is also provided for effecting the method of separating water from air.

Description

METHOD AND APP TUS FO RECO G 'DVA OM A SPHERIC
Field of Invert -on The present invention relates to a method and apparatus for recovering water from atmospheric air and, more particularly, relates to absorption of water vapour from atmospheric air by a liquid absorbent and subsequent regeneration of the liquid absorbent and recovery of the absorbed water vapour.
8ack~uound of the Invelytion It is a well understood fact that a large portion of the world's population, especially in underdeveloped countries, does not have access to clean, potable water. In the developed world, many of the sources of water for human consumption axe unable to keep pace with demand.
Further, quality is either unsustainable ox incrcasimgly expensive. Thus, the need for alternative affordable solutions is substantial. Tn many geographic regions, the need i&
critical for sustaining hum an health and li fe.
fxisting methods for extracting and recovering water from atmospheric air are known.
However, la~ovvn methods stiffer from the fact that they are energy intensive and operationally connplex. This embadimeztt describes a very efficient method of operation.
Summary of the Invention In one aspect, the present invention provides a method of separating water froze air comprising the steps of (a) contacting air having water vapour with an hygroscapic liquid mixture to produce a watEr rich hygroscopic liquid mixture, (b) heating at least a portion of the _, , _ , . _.watex..richhygwscopie liquid-mi~c~ture- a g water vapour and at least one other gaseous component, (c) condensing at least a portion of the water vapour in the gaseous mixture to produce liquid water and a depleted gaseous mixture at a first pressure, and (d) removing at least a portion of the at least one other gaseous component to maintain the first pressure below a predetermined pressure, wherein the depleted gaseous mixttu-e is in fluid eon-ununieation with the water rich hy~oseopic liquid mixture being heated.

in another aspect, the present invention provides a method of separating water from air comprising the steps of (a) contacting air having water vapour with an hygmscopic liquid mixture to produce a water rich hygroscopic liqud mixture, (b) heating at least a portion of the water rich hygroscopic liquid mixture to produce a gaseous mixture having water vapour, (c) condensing at least a portion of the water vapour in the gaseous mixture to produce liquid watEr and heat Energy, and (d) transferring an effective amount of the heat energy to a working fluid including a liquid to effect vapourization of at least a portion of tb~e liquid to produce a working fluid gaseous mixture.
In yet another aspect, the present invention provides a method of recovering water from air comprising the steps of: (a) contacting air having water vapour with an hygroscopic liquid mixture to produce a water rich hygroscopic liquid mixture, (b) in a first pressure envelope, heating the water rich hygroscopic liquid mixture to produce a gaseous mixture having water vapour, condensing at least a portion of the water vapour in the gaseous mixture to produce liquid water and a depleted gaseous mixture, and separating the liquid water from the depleted gaseous mixture so as to provide collected liquid water and a depleted gaseous mixturt at subatmosphelc pressure disposed in a vapour space above the collected liquid water, (c) effecting fluid pressure communication between a second pressure envelope and the vapour space, and (d) flowing the collected liquid from the first prtssurc envelope and into the second pressure envelope.
In a further aspect, the present invention provides an absorption system for effecting removal of water from atmospheric air by an hygroscopic liquid mixture comprising; an absorber vessel defining a space for facilitating contact between air having water vapour and an hygroscopic liquid mixture, including an input air flow inlet, configured for introducing an input air flow having water vapour into the space, a depleted air flow outlet, configured for discharging a depleted air flow, and means for introducing a hygroscopic liquid mixture into the space for effecting contact between the hygroscopic liquid mixture and the input air flow, a base, wherein the absorber vessel is rotatably mounted to the base about an axis for effecting positioning of the input air flow inlet at a desired position relative to the axis.

In another aspect, the present invention provides a method of recovering water from air comprising. (a) providing an absorption system for effecting removal of water from atmospheric air flow by an hygroscopic liquid mixture comprising an absorber vessel defining a space for facilitating contact between air having water vapour and au hygroscopic 11qu1d mixture, including an input air flow inlet, configured for irtttoducing an input air flow having water vapour into the space, a depleted air flow outlet, configured for discharging a depleted air flow, and means for introducing a hygroscopic liquid mixture into the space for effecting contact between the hygroscopic liquid mixture and the input air flow, and a base, wherein the absorber vessel rotatably mounted to the base about an axis for effecting positioning of the input air flow inlet at a desired position relative to the axis, (b) measuring the direction of atmospheric air flow;
and (c) rotating the absorber vessel about the axis so as to effect desired positioning of the input air flow inlet relative to the atmospheric air flow direction in response to the measured atmospheric air flow direction.
In one aspect, the present invention provides an absorber vessel de.fming a space for facilitating contact between air having water vapour and an hygroscopic liquid mixture, including an input air flow inlet, configured for introducing an input air flow having water vapour into the space, a depleted air flow outlet, configured for discharging a depleted air flow, at least one first liquid inlet spay nozzle, configured for introducing a largest diameter fine size droplet into the space at a first position, a second liquid inlet spray nozzle, configured for introducing a largest diameter coarse size droplet into the space at a second position disposed in closer proximity to the outlet relative to the introduced laz-gest diameter fine size nozzle, wherein the largest diameter coarse size droplet has a greater diameter than the largest diameter fine size droplEt when the same liquid is flowed through each of the first and second liquid inlet spray nozzles under the same operating conditions.
).n another aspect, the present invention providES a method of separating water from air comprising the steps of providing an absorber vessel defining a space For facilitating contact between air having water vapour and an hygroscopic liquid mixture, introducing an air flow into the space, spraying frst hygroscopic liquid mixture droplets into the space for effecting contact between the first hygroscopic liquid mixture and the air flow, wherein at lEast one of the first L~ _ hygroscopic liquid mixture droplets is a largest diameter one size droplet, and spraying second hygroscopic liquid mixture droplets into the space downstream of the first hygroscopic liquid mixture droplets for effecting contact between the second hygroscopic liquid mixture and the air flow containing an entrained portion of the first hydroscopic liquid mixture droplets, wherein at least one of the second hygroscopic liquid mixture droplets is a largest diameter coarse size droplet, wherein the largest diameter coarse size droplet has a greater diameter than the largest diameter fine size droplet.
1n another aspect, the present invention ,provides a method of separating water from air comprising the steps of (a) contacting air having water vapour with a hygroscopic liquid mixture consisting of a supersaturated aqueous solution of lithium chloride to produce a water rich hygroscopic liquid mixture, (b) heating at least a portion of the water rich hygroscopic liquid mixture to produce a gaseous mixture including water vapour and at least one other gaseous component, and (c) condensing at least a portion of the water vapour in the gaseous mixture to produce liquid water.
In another aspect, the present invention provides a method of separating water from air comprising the steps of (a) contacting air having water vapour with an hygroscopic liquid mixture to produce a water rich hygroscopic liquid mixture, (b) heating at Ieast a porhion of the water rich hygroscopic liquid mixture with heat generated by a waste heat source to produce a gaseous mixture including water vapour, and (c) eoudensing at least a portion of the water vapour to produce liquid water.
Description of the Drawings The invention wih be better understood and objects other than those set forth above will become appar~~t when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:
Figure 1 is a schematic illustration of an embodiment of the system of the present invention;

b'igure 2 is a schematic illustration of a second embodiment of the system of the present invention; and Figure 3 is a schematic illustration of an alternative embodiment of the combination of the condenser and the water holding tank of the system of the present invention.
Detailed Description Figures 1 and 2 illustrate embodiments of the present izlvention. The present invention includes a system 8 for effecting the separation of water vapour from atmospheric air. In this respect, the system 8 includes an absorber 10 for effecting the separation of wafer vapour from atmospheric air by absorption of the water vapour by a hygroscopic liquid mixture and subsequent recovery of the water vapour from the water rich hygroscopic liquid mixture as liquid water. In the Figure 1 embodiment, the absorber 10 is substantially vextical, and the flows of atmospheric air and the hygroscopic liquid mixture are countercurrent relative to one another. Itt the Figure 2 embodiment, the absorber is substantially horizontal, and the flows of atmospheric air and the hygroscopic liquid mixture are crossflow relative to one another.
The absorber 10 is configured for effecting contact between atmospheric air and a hygroscopiC liquid mixture to produce a depleted air system and a water rich hygroscopic liquid mixture. Water ricli hygroscopic liquid mixture describes a fluid flow which initially was a hygroscopic liquid mixture introduced into the absorber 10 which has subsequently absorbed water upon contact with atmospheric air in the absorber 10.
Preferably, the hygroscopic liquid nnixture is an aqueous solution of a hygroscopic solute.
More preferably, the hygroscopic liquid mixture is a liquid dessicant such as a solution of a Crroup 1 and/or a Group 2 salt (preferably a chloride), in water, glycol, glycerine or sulphuric acid. Even more preferably, the hygroscopie Liquid mixture is an aqueous lithium chloride (LiCl) solution. It is understood that various concentrations of aqueous lithium chloride solution are suitable for the purpose of a hygroscopie liquid mixtltre_ In a preferred embodiment, the hygroscopie liquid mixture comprises $om 30 wt% to 50 wt% LiCl Salt based upon the total weight of the aqueous lithium chloride solution. In one embodiment, the solution comprises about 40 wt% LiCI salt and 60 wt% water.
1n terms of the extent to whuich the hy,groscopic liquid mixture is able to absorb water from atmospheric air, it has been recognized that the hygroscopic liquid mixture can be a supersaturated aqueous solution of LiCI. In this respect, the hygroscopic liquid mixture can be an aqueous lithium chloride solution comprising an effective amount of LiCI to render the solution to be supersaturated (greater concentration of dissolved LiCI in water than that predicted under equilibrium conditions at a given temperature and pressure). The hygroscopic liquid mixture leaving the desotption vessel 46 can be a supersaturated solution of LiCI in water. The hygmscopic liquid mixture becomes such a supersaturated solution as a result of water being vaporized ii-om the water rich hygroscopic liqiud mixture. As water is vapourized in the desorption vessel 46, the concentration of the LiCI in the liquid mixture increases. Eventually, the concentration increases beyond the known equilibrium saturation point. So long as the mixture is relatively clean, the LiCI will not procipitate out as the LiCI
concexatration moves beyond the equilibrium saturation point. For example, the absorption process can opErate with aP~ h~gioscopic~licjuid mijctui-e consisting of ~an aqueous solution Having 40 wt% LiCl~based~on~ ~ ~~ ~-~~~~~~Y~ -~ ~~
the total weight of the solution, at a temperature less than 0°C and at atmospheric pressure. Such an aqueous solution is supersaturated at these temperature and pressure conditions, as sucli solution has a higher concentration of LiCI than would normally be obtained (ie. predicted by equilibrium data) in a saturated solution of LiCI in water (ic. 40 wt% LiCl dissolved in water at these temperature and pressure conditions is more than would normally be possible). It has been observed that the concentration of LiC1 in art aqueous solution functioning as the hygroscopic liquid mixture can exceed its equilibrium (saturation) concentration in aqueous solution (at a given temperature and pressure) by up to 7%. By using a supersaturated solution as the hygroscopic liquid mixture, additional water can be absorbed from the atmospheric air flow at lower temperatures by the same volume of hygtoscopic liquid mixture within the absorber.
In this respect, in one aspect, the present invention provides a method of separating water frozx~. air comprising the stops of (a) contacting air having water vapaur with a hygroscopie liquid mixture consisting of a supersaturated aqueous solution of lithium chloride to produce a water rich hygroscopic liquid mixture, (b) heating at Ieast a portion of the water rich hygroscopic liquid mixture to produce a gaseous mixture including water vapour and at least one other gaseous component, and (c) condensing at least a portion of the water vapour in the gaseous mixture to produce liquid water.
The absorber 10 is fluidly coupled to a desorber 12 to effect transfer of at least a portion of the water rich hygmscopic liquid mixture from the absorber 10 to the desorber 12. The desorber 12 is configured for heating the water rich hygroscopic liquid mixture to produce a gaseous mixture including water (in the form of water vapour) and small amounts of at least one othEr gaseous component and a regenerated hygmscopic liquid mixture.
Concomitantly, the vaporization of the gaseous mixture leaves a regenerated hygroscvpic liquid mixture for reuse in the absorber 10. The desorber I2 is fluidly coupled to a condenser 14 for transferring the gaseous mixture to the condenser 14. The condenser 14 is configured for condensing the water vapour in the gaseous mixture, In condensing the water vapour in the exemplary embodiment, the condenser 14 is also configured to transfer sufficient heat energy from the water vapour to a working fluid including a liquid to effect vaporization of at least a portion of the liquid (for example, the liquid of a working fluid in a heat pipe). lVxeans 60 are provided to effect removal of at least a portion of the other gaseous components from the gaseous ixaixture to maintain the pressure of the gaseous mixture below a predetermined pressure. In the preferred embodiment, the predetermined pressure is a subatmospheric pressure. Qnce the water rich hygroscopic liquid mixture is depleted of at least a portion of its contents by vaporization in the desorber 12, the remaining hygroscopic liquid mixture is returned to the absorber 10.
Absorber As mentioned above, the system 8 includes an absorber 10 having an absorber vessel 18 for e.Efecting contact between (i) atmospheric air having water vapour, and (ii) the hygroscopie liquid mixture. An electrical variable speed atmospheric air ~an 20 is provided and conbgured to continuously introduce the atmospheric air to the absorber vessel 18 in either a pull or push configuration and create a flow of atmospheric air through the absorber vessel 18. Prior to entering the absorber vessel 18, the atmospheric air passes through an air filtration system 22 to remove dust and other unwanted airborne particles. The atmospheric air flows through the absorber vessel 18 and becomes depleted in water vapour as the atmospheric air makes contact -s-with the hygroscopic liquid mixture in the reaction zone 19. The removal of water vapour from the atmospheric air is monitored by temperature, humidity and pressure sensors 28 located at the atmospheric air entrance and exit of the absorber vessel 18.
Referring to Figure 2, in one embodiment, tht absorber LO could be rotatably mounted to a base 21. In this respect, the absorber 10 is configured for rotation relative to the base 21 so that the atmospheric air entrance is facing the prevailing wind direction thereby reducing the amount of energy requzral to operate the fan 20. Wind speed and direction information can be obtained fxom a mast mounted weather station with the sensors to measure air temperature, rainfall, relative humidity, solar radiation, wind speed, wind direction, and barometric pressure.
To retrieve the weather measwerr~ents, a spread spectratn radio provides a data co~nr~ection bttween the weather station sensor assembly and the compufcr used to nul the software that stores and processes the weather information.. A variable control air flow damper 23 can be provided in the event the prevailing atmospheric air wind speeds exceed the desired atmospheric air flow rate through the absorber vessel 18. Rotatio~a on the base 21 and air flow damper 23 controls can be effected by the system 8 control software and rriechanically driven by electrical motors or other similar means. The benefit is minimal to no energy requirercerits to move atmospheric air through the absorber vessel 18.
In tlus respect, in one aspect, the present invention provides an absorption system far effecting removal of water from atmospheric air by an bygroscopie liquid mixttu-e comprising an absorber vessel 18 defining a space 19 for facilitating contact between air having water vapour and an hygroscopic liquid mixture, including an input air flow inlet I81, con$gured for introducing an input air flow having water vapour into the space, a depleted air flow outlet 182, configured for discharging a depleted air flow, and means for introducing a hygroseopic liquid mixture into the space 19 for effecting contact between the hygroscopic liquid mixture and the input air flow. The absorber vessel 1$ is rotatabiy mounted to the base 21 about an axis "X" for affecting positionixtg of the input air flow inlet at a desired position relative to the axis.
In parallel, in another aspect, the present invention provides a method of recovering water from air comprising (a) providing an absorption system for efl;ecting removal of water from atmospheric air flow by an hygroscopic liquid mixture comprising an absorber vessel defining a space for facilitating contact between air having water vapour and an hygroscopic liquid mixture, including an input air flow inlet, configured for introducing an input air flow having water vapour into the space, a depleted air flow outlet, configured for discharging a depleted air flow, and means for introducing a hygroscopic liquid mixture into the space for effecting contact between the hygroscopic liquid mixture and the input air flow, and a base, wherein the rotatably mounted to the base about an axis for effecting positioning of the input air flow inlet at a desired position relative to the axis, (b) measuring the direction of atmospheric air flow, and (c) rotating the absorber tank about the axis so as to effect desired positioning of the input air flow inlet relative to the atmospheric air flow direction.
Heat exchanger $0 is used to lower the tcmperaturc of the hygroscopic liquid mixture before it reaches the absorber 10 and is configured to transfer a portion of the heat created by the desorption process occurring in the desorber vessel 12 externally of the apparatus. Cooling improves the equilibrium tendency of absorption of the water vapour from the atmospheric air by the hygroscopic liquid mixture, thereby increasing the amount of water vapour that is captured and improving system efficencies. The heat exchanger can be configured to use any o~ the common heat exchanger cooling methods practised in industry ixtcluding the use of heat pipes.
The preferred embodiment is to use heat pipes as they require no external energy to work. The arnouat of cooling is controlled by temperature dii'ferendal from sensors 41 and 28 (sce Figurc 2).
In the Figure 2 embodiment, at least a portion of the hygroscopic liquid mixture is continuously circulated via conduit 403 by mechanical liquid pump 444 between the absorber's accumulator 15 and the shower assemblies 32, 33. This continuous circulation loads the hygroscopic liquid mixture with the captured atmospheric air water vapour resulting in a density reduction of the hygroscopic liquid mixture and its transformation to the water rich hygroseopic liquid mixture. This circulated hygroscopic liquid mixture is cooled by heat exchanger 401. The amount of cooling is controlled by the temperature differential measured between sensors 411 and 28.
In the Figure 2 embodiment, a portion of the water rich hygroseopic liquid mixture is recirculated directly to the shower assemblies 32, 33, while the remainder is directed {transferred) to the desorption vessel 46 (described) for regeneration purposes. Once regenerated as the hygroscopic liquid mixture, the hygroscopic liquid mpxt<we is flowed to the shower assemblies 32, 33. The proportion of water ricli hygroscopic liquid mixture transferred to the absorber vessel 46 intake is dependent on the rate of water vapour captured as indicated by the density changes measured by sensor 352. A standard inline ttxounted deity measuring device with a continuous digital feed to the application software computer is used.
The data feed can be via cable or wireless. Preferably, in the Figure 2 embodiment, the difference between concentration of LiCI within the hygroscopic liquid mixture leaving the outlet of the desorption vessel 46 and the concentration of LiCI within the hygroscopic liquid mixture entering the inlet of the absorber vessel 18, based upon the total weight of mixture, deviates no more than 5 wt%, and more preferably no ~x~,ore than I%, and even more preferably no more than 0.5 wt%, during continuous operation.
A plurality of transfer pipes 30 are provided to continuously introduce the hygroscopic liquid mixture to the absorber vessel 18 for contact with the atmospheric sir.
The transfer pipes 30 are fluidly coupled to shower assemblies 32, 33 disposed within the absorber vessel 18. The shower assemblies 32, 33 include spray nozzles which are configured to spray liquid spray droplets into the atmospheric air stream being flowed through the absorber vessel 18. Tlie spray nozzles 32 are disposed upstream of the spray nozzles 33, relative to the flowing atmospheric air.
The spray nozzles on shower assemblies 32 are designed to produce very fine size droplets and a dense spray pattern where the droplet spacing is minimal for the purposes of maximizing the liquid to gas surface contact area. It is preferred to maximize the liquid to gas surface contact area in order capture the greatest amount of water vapour from the atmospheric air per unit of energy consumed. l3roplet sizes approaching 500 macrons are desirable.
Experimentation has shown that the fine droplets 31 are prone to swirling in the airflow and can become entrained in the atmospheric sir flow and carried out of the absorber vessel 18 unless a method of containment is implemented.
In this respect, the spray nozzles on shower assemblies 33 are configured to pmduce coarse size droplets 34 at a position in the space 19 in closer proximity to the outlet 1$2 than the position at which the fine size droplets 33 arc introduced. The coarse size droplets 34 arc introduced downstream of the fne size droplets 31 for the purpose of capturing, or coalescing -II-with the fine spray droplets 31 which may become entrained in tine atmospheric air flow. '1,'he coarse droplets 34 include droplets having varying diameters. The coarse size droplet (or droplets) 34 having the largest diameter of the coarse size droplets 34 is herein referred to as the largest diameter coarse siu droplet. Similarly, the fine spray droplet (or droplets) 31 having the largest diameter of the fine spray droplets 31 is herein referred to as the largest diameter fine size droplet. In one aspect of the present invention, the diameter of the largest diameter coarse size droplets is greater than the diameter of the largest diameter fine size droplets. preferably, the largest diameter coarse size droplet has a diameter which is 100 times greater than the diameter of the largest diameter fine size droplet. More preferably, the largest diameter coarse size droplet has a diameter which is 1000 times greater than the diameter of the largest diameter fine size droplet. Even more preferably, the largest diameter coarse size droplet has a diameter which is 100,000 times greater than the diameter of the largest diameter 6ne size droplet.
'l l2he coarse size droplets 34 combine with the fine spray droplets 31 entrained in the air flow and, due to the force of gravity and the course spray droplets 34 nozzle exit speeds, arc carried downwards into the accumulator 15 located at the base of the absorber vessel I8. The accumulator 15 collects the water rich hygroscopic liquid mixttu~e for further processing. Mist capture screens lb, such as an electrostatic screen, are additionally provided to fnzther mitigate any mist carry over.
The hygroscopic liquid mixture flow rates to the shower assemblies 32, 33 are controlled by the nozzle design parameters which dictate the volumetric flow rate and fluid prossure required to atomize the liquid absorbent stream into hne spray droplets 31 and coarse spray droplets 34. l~Tozzle selection varies according to the operating conditions of a particular apparatus. Experimentation has shown these operating conditions include, but are not limited to, the atmospheric air temperature, pressure and relative humidity range for a given geographical location, the desired water production volume which governs the volume of atmosplieric air to be processed by the absorber 10, the volume of the absorber vessel 1$, the operating range of density and viscosity to the hygroseopic liquid mixture, the amount of prime and waste energy available, and Vhe desired water production rate and operating cost per gallon of water produced.

An example of a typical fine spray nozzle 32 is the Spraying Systems Co.
VeeJet'''M spray nozzles model H-W series. The jets produce a flat 110 spray pattern. Azx example of a typical coarse spray nozzle 33 is the Spraying Systems Co. FIoodjetT'a, wide angle spray nozzles model H-V'V series. The jets produce a flat 110 spray pattern. For the same operating conditions (temperature, pressure, flow rate), and using the same hygroscopic liquid mixture, the VeefetTM
spray nozzle having an orifice diamctcr of 0.061 inches produces a largest diameter fine size droplet whose diameter is less than the diameter of a largest diameter coarse size droplet produced by the FIoodJef~ spray nozzle having an orifice diameter of 0.066 inches. It has been observed that for an aqueous LiCI solution having 40 wt°!o LiCI based on the total weight of solution Flowing through the VeeJetT~ spray nozzle having a diametex of 0.061 inches at a flow rate of 0.52 GPM at a pressure of 30 psig, the largest diameter Extra size droplet has a smaller diameter than the largest diameter coarse size droplet produced when flowing the same aqueous lithium chloride solutio~a through a FloodJetTM spray nozzle having an orifice diameter of 0.066 inches at a flow rate of 0.8 GPM and at a pressure of 30 psig.
The desired hygroseopic liquid mixture fed to the shower assemblies 32, 33 comprises a predetermined ratio by weight percent of absorbent material (litluum chloride) and water as measured by density sensors 351, 352. This ratio of hygroscopic liquid mixture to the atmospheric air water vapour in the absorption cycle is controlled by a software algorithm that optimizes the atmospheric air flow rate, the hygroscopic liquid mixture nozzle spxay flow rate based on fluid pressure and the partial pressure di i'ferential between the partial pressure of water in the hygroscopic liquid mixture and the partial pressure of water vapour in the atmospheric air.
Information from sensors 28, 351 and 36 for the hygroscopic liquid mixture's density. and temperature, the atmospheric temperature, humidity, and pressure conditions, the available energy and the desixed water production rate are the primary inputs to the system control software algorithm.
A heat exchanger, such as heat pipes 38, is disposed in the absorber vessel 18 and is eocifigur~l to transfer at least a portion of the heat created by the absorption process occurring in the absorber vessel 18 externally of the absorber vessel 18. Such cooling is helpful for improving the equilibrium tendency of absorption of the water vapour from the atmospheric air by the hygros~.opic liquid mixture. The heat pipes 38 are coupled to cooling fins 40 disposed externally of the absorber vessel 18. The cooling fins 40 effect dissipation of the heat to the attnvsphere. In this respect, a fan 42 is provided tv blow air across the cooling fins 40 to assist in the heat dissipation. 'Z'lte fan 42 is controlled by temperature sensors 36 on the heat pipes.
Regeneratfon The regeneration process of the hygroscopic liquid mixture is performed by the desorber 12 which includes a desorption vessel 46 and a heater 48, The desorption vessel 46 is configured to operate under internal pressure conditions ranging from standard atmospheric pressure to a deep vacuum and is controlled by the level of vacuum in the condenser 14. The vacuum is typically achieved with a variable speed two-stage rotary van vacuum pump designed to lower the pressure iui the desorption vessel 46 and the condenser vessel 52 to a pressure of 25 Ton.
The desorption vessel 46 is configured to receive and contain the water rich hygroscoplc liquid mixture transferred from the absorber 10. The water rich hygroscopic liquid mixture is drawn into the desorption vessel 46 by the force of the vacuum within the desorption vessel 46 which results in a pressure differential between the absorber vessel 1$ and the desorption vessel 46. The level of the water rich hygroscopic liquid mixture in the desorption vessel 46 is controlled by the liquid level sensor and control naive assembly 49 by throttling the rich liquid absorbent flow rate as it flows to pump assembly 73 (see the Figure 2 embodiment).
The heater 48 is configured to impart heat energy to the water rich hygroscopic liquid mixtwe to e$ect continuous production of a gaseous mixture 50 from the water rich hygroscopic liquid mixture. The gaseous mixture 50 predominantly includes water vapour anl, to a small extent, other gaseous components, such as inert gases. By operating the desorbcr 12 under a partial vacuum, the vaporization temperature is effectively lowered, facilitating the use of lower grade heat (lower temperature) to effect release of the water vapour from the lean liquid absorbent_ The amount of heat introduced to the desorption vessel 46 is controlled by the temperature sensor 53 and pressure sensor 55 and the rich liquid absorbent de~.sity sensor 351 and the lean liquid absorbeztt density sensor 352. The system 8 control software uses the vacuum pressure from pressure sensor 622, the liquid absorbent density value from density sensor 352 and standard steam table teiuperature and absolute pressure values, adjusted to account for the liquid absorbent density which is higher than pure water, to determine the optimal operating temperature for the regenerator 12. This calculation is used to start the regeneration process and further temperature adjustments are made by the control software basEd on the data provided by the sensors 351 and 352 and the associated density differential. The regeneration process maintains this liquid absorbent density differential within lwt% by increasing or decreasing the heat introduced to the heat exchanger 48. Additional heat results in a faster vaporization rate which increases water production from the regenerator 12 and increases the density of the liquid absorbent departing the regenerator vessel 46. Tlus rich liquid absorbent flows into the lean liquid absorbent flow to the absorber thereby regenerating the liquid absorbent and maintaining the liquid absorbent density level at the desired concentration of LiCI salt to water by weight.
This is one preferred method of maintaining equilibrium between the volume of water captured by the absorber 10 from the atmospheric air's water vapour and the volume of water produced for consumption in the condenser 14. Other methods will become apparent to the experienced person skilled in the art. These include measuring the amount of water vapour rennoved by coraparing the hunudity levels of the incoming and outgoing air flow.
Calculating the water volume and comparing this value to the water produced in, the condenser and increasing or decreasing heat to the regenerator to maintain equilibrium. Another method would be to measure and maintain the volume of liquid desiccant in the system 8.
Heat may be supplied to the deserter 12 as waste heat from anoklier unit operation, such as a diesel engine generator 50. Referring to Figure 2, in the case of reciprocating engine, heat can be used from the exhaust flow as well as the engines coolant. The engine coolant heat exchanger 90 provides a method for raising the temperature of the lean liquid absorbent before it enters the desorption vessel 46. This lowers the amount of energy required to heat the incoming lean liquid absorbent in the desorption vessel 46. The exhaust flow 96 which is at a high temperature is used as the heat source for the desorption vessel 46. The exhaust flow redirector valve assembly 98 is used to control the amount of heat entering the heat exchanger 48, as measured by temperature sensor 53, by diverting a percentagt of the exhaust gas flow to the bypass pipe assembly 95. It is understood that such heat can be supplied from any one of a variety of sources, including other waste heat sources and prime heat sources such as, but not limited to, electric heaters, fossil fuels, solar, thermal and nuclear energy and hydrogen generators_ Waste heat is heat energy which is generated as a by-product by any process.
The waste heat would otherwise be expelled or rejected to the surrounding environment.
For example, an exhausted gaseous mixture from an engine can serve as a source of waste heat, as such gaseous mixture is, by de~ulition, typically expelled to the surrounding atmosphere. Also, engine coolant in the form of a liquid mixture or a gaseous mixture cant also serve as a somrce of waste heat, as the heat cornmuxaicated from the engine process to the coolant is then typically expelled or transferred to the atmosphere. Also, any oil lubricant to which heat energy is thermally communicated from an engine process can also serve as a source of waste heat, as the heat communicated from the engine process to the oil lubt'icant is then typically expelled or rejected or transferred to the atmosphere.
Tn the above cases (engine exhaust, engine coolant, engine lubricant), the heated cngi~ne fluid can be flowed or fluidly communicated away from the engine such that the heated fluid becomes disposed in thermal communication with the water rich hygroscopic liquid mixture so as to effect heating of the water rich hygroscopie liquid mixture and at least in part eontctbute to effecting vaporization of the water rich hygroscopic liquid mixture. l: ox example, such heated fluid may be flowed to the desorber 12 so as to thermally communicate heat energy to the water rich hygroscopic liquid mixture in the desorber 12. Alternatively, a heat pipe, or any other type of heat exchanger, could be used to indirectly effect heat transfer between the heat~l engine fluid and the water rich hygroscopic liquid m~lxture.
A further example of a source of waste heat is condensatt rejected from a strain turbine.
This includes condensate rejected from the steam driven turbine of a Rankin cycle engine. The steam turbine may also form part of a coal fired, gas powered, or nuclear powered electricity generating process. The condensate could be flowed or fluidly communicated into thermal communication disposition with the water rich hygcoscopic liquid mixture so as to effect heating of the water rich hygroscopic liquid mixture and at least in part contribute to effecting vaporization of the water rich hygroscopic liquid mixture. For example, such condenfsate may be flowed to the desorber 12 so as to thermally communicate heat energy to the vrater rich hygroscopic liquid mixture in the desorber 12. .Alternatively, a heat pipe, or any other type of heat exchanger could be used to indirectly effect heat transfer between the condensate and the water rich hygroscopic liquid mixture.
The hygl-oscopic liquid mixture in the desorber 12 is continuously removed for purposes of regeneration and return to the absorber 10. In this respect, a pump flow control assembly 73 is fluidly coupled to the desorber vessel 4b and is con:&gwred for continuously flowing the hygroscopie liquid mixture to the absorber 10, combining with the hygroscopie liquid mixture being circulated via c4nduit 403 {described about), thereby completing a regeneration cycle for the liquid absorbent. In the Figure 2 embodiment, the heat exchanger 80 transfers a portion of the heat contained in the hygroscopic liquid mixture (being transferred from the desorber vessel 46 to the absorber vessel 1$) to the incoming water rich hygroscopic liquid mixture thereby preheating the water rich hygroscopic liquid mixture and partially cooling the hygroseopie liquid mixture. The result is higher system energy efficiencies through lowering the regeneration energy reqtrirements for heating.
Condensation The gaseous mixture 50 continuously flows from the desorber 12 to the condenser 14 under the driving force of the partial vacuum created within the condenser vessel 52. In the preferred embodiment, the pressure of the gaseous mixture in the desorption vessel 46 and the condenser vessel 52 is within a range of between 25 Torr and 760 Torr {i.e.
0.4$3 psia and 14.7 psia). Preferably, it is as low as possible.
It is mderstood tliat the system 8 can be operated with gaseous mixtures having higher pressures in the desorption vessel 46 and the condenser vessel 52 although this is not the preferred embodiment due to energy efficiency losses. The desorber vessel 45 is fluidly coupled to the condenser vessel 52 by a txansfer pipe 54_ The transfer pipe 54 is as short as practical to keep pressure differentials as small as possible between the desorber vessel 4b and the condenser vessels 52. The condenser 14 includes a heat pipe assembly 58 disposed in the condenser vessel 52 for effecting cooling of the water vapour to effect condensation of liquid water from the water vapour of the gaseous mixture. Once condensed, the liquid water falls to the bottom of the condenser vessel 52.

The partial vacuum in the condenser vessel 52 is maintained by the condensing steam.
Prior to operation, the condenser vessel 52 is evacuated by the variable speed vacuum pump 60 to create the desired vacuum conditions.
Vacuum Pump The vacuum pump 60 also functions as tlae means for removing the other gaseous componalts present in the gaseous mixture to maintain the pressure of the gaseous mixture below a predetermined pressure within the condenser vessel 52. The accumulation of these other gaseous components in the condenser vessel 52 increases the pressure of the gaseous mixture in the desorber 12 and tht condenser vessel 52, and effectively ztecessitates a higher quality of heat (higher temperature) in the dcsorber 12 to release the gaseous mixture from the water rich hygroscopic liquid mixture. The vacuum pump 60 is triggered to effect removal of these other gaseous camponcnts upon a high eonoentration indication of the other gaseous components from within the condenser vessel 52.
In one embodiment, the high conecntratiort indication is a low temperature indication which is sensed in a region 1fi of the condenser vessel 52 proximate to the bottom of the vessel and above the level of the collected liquid water. The other gaseous caznponents of the gaseous mixture collect just above the level of the collected liquid marks as they have a higher molecular weight thazl the water vapour. The other gaseous components of the gaseous mixture release licit to the condensed water which falls downwardly in the condenser vessel 52.
.A,s gas accumulates aborre the collected water, a temperature and humidity sensor 621 senses a temperature of the gaseous mixture immediately above the collected water.
Temperature and float sensor 69 measures temperature and also liquid level of the collected liquid water. This gaseous mixture is at a lower temperature than the collected water. When the temperature differential between that measured by sensors 621 and 69 exceeds a predetermined amount, this indicates that an undesirable concentration of the other gaseous components are present in the gas innmediately above the collected water, and the vacuum pump 60 is activated to remove the other gaseous components frrnxl the condenser vessel 52. When the temperature difference returns below the predetermined amount, thereby indicating an acceptable amount of the other gaseous components, the vacuum pump GO is deactivated.

_ 1$ _ Another means of controlling the cycling of the vacuum pump GO is through the measurement of humidity immediately above the collected water, by the temperature and humidity sensor 621, which can indicate an utxacceptably high inert gas concentration if hutrddity falls below a predetermined set point. A further mss is the vacuum pressure sensor 55, which senses pressure changes in the condenser vessel 52, and which can indicate a build-up of other gaseous components to unacceptably high concentration levels. Any of these means fox sensing a hi,,ah pressure indication can also be combined for purposes of maintaining floe desired pressure within the condenser vessel 52 by triggering operation of the vacuum pump 60 to effect evacuation of the other gaseous components from the condenser vessel 52 until su~cient s~aseous components are removed.
In another embodiment, sensor 621 consists of a temperature sensor (which functions as described above) and a pressure sensor. The pressure sensor senses pressure just above the level of the collected liquid water. if the prESSUre is above a predetermined amount, pump GO is activated and operates until floe pressure returns below the predcterrxlined amount_ The ~racuum pump 60 is configured to draw the other gaseous components from proximate the bottom of the condenser vessel 52, but above the level of the condensed liquid water. The pipe 62 that draws the otlier gaseous components from proximate the bottom of the condenser vessel 52 extends, upwardly and is cooled by heat pipe assembly 58, permitting steam to condense so that only the other gaseous components ofthe gaseous mixture (other than steam) are pumped frora the condenser by the vacuum pump G0.
Heat Pipes The heat pipes 58 are used to effect condensation of the water vapour from the gaseous mixture for purposes of reducing the energy load requirements for the system $. Heat pipes are described in "What is a Heat pipe" at http://www.cheresources.com/htpiyes html. Suitable heat pipes include gravity flow type heat pipCs as well as capillary flow type heat pipes, Examples of a suitable working fluid Include propane, ethanol, and acetone. By using heat pipes 58 to effect the necessary cooling of the water vapour, the temperature differential of the working fluid in the heat pipe is srrxaller than for other convenrional heat transfer mechanisms.
This is because the heat transferrc;d from the water vapour to the working fluid, upon condensation of the water vapour, is primarily used as latent heat to vapourize the working fluid and does not cause a substantial increase in the temperature of the working fluid. As a result, the water vapour can be condensed at a lower temperature within the condenses vessel 52. Consequently, the gaseous mixture can be produced in the desorber 12 at lower temperatures, thereby zeducing the overall quality of heat energy required for the system. In the exemplary embodiment, the water vapour is condensed in the condenser vessel 52 within a temperature range of between 20°C and 85°C.
rn this respect, in one aspect, the present invention provides a method of separating water from air comprising the steps of (a) contacting air hawing water vapour with an hygroscopic liquid mixture to produce a water rich hygroscopic liquid mixture, (b) heating at least a portiatt of the water rich hy~oscopic liquid mixture to produce a gaseous mixture having water vapour, (c) condensing at least a gortion o~ the water vapour in the gaseous mixture to produce liquid water and heat energy, and (d) transfernng an effective amount of the heat energy to a waxking fluid including a liquid to effect vapourization of at least a portion of the liquid to produce a working fluid gaseous mixtwre.
The beat pipes 58 are coupled externally of the condenser vessel 52 to external cooling fns 64. The external cooling fins 64 effect dissipation of this heat to the atmosphere. A fan b6 is provided to blow air across the cooling fins 64 to assist in the heat dissipation. The fan 66 is controlled by temperature differentials between the temperature sensors 621, 622 on the condenser vessel 52 and the temperature sensor 623 on the heat pipes 58 and cooling ins 64.
Other embodiments may use this heat for other purposes, in which case the heat would not be dissipated to atmospheric but captured by conventional type heat exchangers which can include using heat rejected from the condenser 14 to preheat the water rich hygroscopic liquid mixture from the absorber 10. Other embodiments .may use otlier means of heat exchangers to remove heat from the heat pipe assembly 58 including refrigeration techniques and other conventional techniques practices in the HVAC industry_ Recovery of Collected Water A pump flow control assembly 70 is Fluidly coupled to the bottom of the condenser vessEl 52 to elect removal of the liquid water collected at the bottom of the condenser vessel 52 and transfer to a water holding tank 72 for storage and later use (for example, consumption).
The pump 70 is activated by the liquid level sensor 69 which maintains a constant water Ievel in the condenser vessel 52. The water in the holding tank 72 can be treated to maintain purity with carbon filters and ultraviolet light or other conventional treatment means.
An alternate configuration fox the holding tank 72 and condenser vessel 52 combination for effecting removal of the water collected at the bottom of the condenser vessel 52 is illustrated in Figure 3. This configuration enables the draining of the collected water to the holding tank 72 without using a pump flow assembly 70_ In order to be able to use the collected water, the water must be drained fmm the condenser vessel 52 into atmospheric pressure conditions. Preferably, such collected water should be svnply drained by gravity. hiowever, the collected water should be pressurized, to some degree, relative to its state within the condenser vessel 52 (the collected water has a pressure which is subatmospheric), prior to draining, in order to facilitate draining of the collected water within a reasonable time. It is also desirable to maintain low pressure conditions within the condenser vessel 52 and not intermittently pressurize the condenser vessel 52 simply for purposes of facilitating draining of the collected water.
To this end, it is preferred that the collected water, as an interzn.ediate step, be first drained from the condenser vessel 52 and into a water storage holding tank 72, wherein the pressure within the water holding tank 72 is comparable to that within the condenser vessel 52.
When sufficient water is drained into the water holding storage tank 72, the water holding teak is isolated from the condenser vessel 52 and then pressurized (for example, by opening a vent to atmosphere). A,s a result, water can be drained at a more reasonable rate into atmospheric conditions by gravity, as the pressure differential against which gravitational forces must operate to effect flow (discharge) of the water is reduced or eliminated.
rn this respect, in one aspect, the present invention provides a method of recovering water from air comprising the steps of (a) contacting air having water vapour with an hygroscopic liquid mixture to produce a water rich hygroscopic liquid mixture, (b) in a first pressure c;nvelope, heating the water rich hygroscopic liquid mixture to produce a gaseous mixture having water vapour, condensing at least a portion of the water vapour to produce liquid water and a ~21-depleted gaseous mixture, and separating the Liquid water from the depleted gaseous mixture so as to provide collected liquid water and a depleted gaseous mixture at sub-atmospheric pressure disposed in a vapour space above the collected liquid water, (c) effecting fluid pressure communication between a second pressure envelope Grad the vapour space; and (d}flowing the collected liquid water from the fixst pressure envelope and into the second pressure envelope.
Refernng to the Figure 3 embodiment, the draining of the water collected in the condenser vessel 52 to the holding tank 72 operates as follows_ When the holding tank 72 is first fluidly coupled to the condenser vessel 52, valves 701, 703, 707 and 708 are closed, and valves 702, 704, 705, and 706 are opened. This allows the vacuum pump 60 to evacuate the holding tanlt 72 and its coxtn~tion lines. Once a partial vacuum is established, valve 702 is closed, and valves 701, and 703 are opened. This allows collected water in the condenser vessel 52 to drain through valves 701, 704, and 705 into the holding tank 72 while any vapour is vented into the condenser vessel 52 through valves 703, and 70b_ Once the holding tank 72 is full, alI valves 701 to 706 are closed and holding tank 72 can be uncoupled 1.'xom the condenser vessel 52 (where quick release couplings are provided along the dotted line 720}. Altern tively, the holding tank can remain coupled to the condenser vessel 52 during draining. In this respect, while valves 701 to 706 are closed, valves 707 and 708 are opened to effect such draining. In this embodiment, the vacuum pump assembly 60 would be mounted to the condenser vessel 52 to facilitate vertical movement within the condenser vessel 52 to maintain a predetermined distance to the surface of the water collected in the condenser vessel 52 {and relative to the condenser vessel 52). This vertical movement can be facilitatEd through mechanical means or a float proximate to the surface of the water.
Operation In operation of the present invention, an hygroscopic liquid mixture is brought into contact in the absorber 10 with atmospheric air having water vapour. The hygrosCOpiC liquid mixture absorbs water vapour form the atmospheric air to produce a water rich lxygroscopic liquid mixture including absorbed water vapour.

_' At least a portion of the water rich hygroscoplc liquid mixture is heated in the desorber 12 under a partial vaeuuna to pxoduce a gaseous nvxture including water and at least one other gaseous component, such as an inert gas. The gaseous ttnixture is flowed to the condenser 14.
The water vapour of the gaseous mixture is cooled and condensed by a heat pipe system 58 in the condenser 14. In this respect, heat energy is transferred from the water vapour to the working fluid in the heat pipe system 5$ to effect vaporization of at least a portion of the liquid of the working fluid.
The gaseous mixture is maintained below a predetermined pressure when the water vapour is condensed. In this respect, in one aspect, the present invention provides a method of separating water from air comprising the steps of (a) contacting air having water vapour with an hygroseopic liquid mixture to produce a water rich hygroscopic liquid mixture, (b) heating at least a portion of the water rich hygroscopic liquid mixture to produce a gaseous mixture having water vapour and at least one other gaseous component, (c) condensiug at least a portion of the water vapour in the gaseous mixture to produce liquid water and a depleted gaseous mixture at a first pressure, and (d) removing at least a portion of the at least one other gaseous component to maintain the first pressure below a predetermined pressure, wherein the depleted gaseous mixture is in fluid communication with the water rich hygroscopic liquid mixture.
Although the disclosure describes arid illustrates preFerred embodiments of the invention, it is to be understood that the invention is not limited to these particular embodiments. Many variations and modifications will now occur to those skilled in the art. For definition of the invention, reference is to be made to the appended claims.

Claims

1. A method of separating water from air comprising the steps of:
(a) contacting air having water vapour with an hygroscopic liquid mixture to produce a water rich hygroscopic liquid mixture;

(b) heating at least a portion of the water rich hygroscopic liquid mixture to produce a gaseous mixture including water vapour and at least one other gaseous component;

(c) condensing at least a portion of the water vapour in the gaseous mixture to produce liquid water and a depleted gaseous mixture at a first pressure; and (d) removing at least a portion of the at least one other gaseous component to maintain the first pressure below a predetermined pressure.

wherein the depleted gaseous mixture is in fluid communication with the water rich hygroscopic liquid mixture being heated.

2. The method as claimed in claim 1, wherein the predetermined pressure is subatmospheric.

3. The method as claimed in claim 1, wherein the predetermined pressure is between 25 Torr and 760 Torr.

4. The method as claimed in claim 2, wherein at least a portion of the water vapour is absorbed by the hygroscopic liquid mixture during the contacting in step (a).

5. The method as claimed in claim 4, wherein the method further comprises the step of separating the liquid water from the depleted gaseous mixture such that the depleted gaseous mixture is disposed in a vapour space above the liquid water.

6. The method as claimed in claim 5, wherein the removing in step (d) occurs in response to a high concentration indication of one of the at least one other gaseous component.

7. The method as claimed in claim 5, wherein the removing in step (d) occurs in response to a high pressure indication in the vapour space.

8. The method as claimed in claim 5, wherein the removing in step (d) occurs in response to a low temperature indication in the vapour space.

9. The method as claimed in any of claims 5, wherein, the removing of at least a portion of the at least one other gaseous component is effected by a vacuum pump.

10. The method as claimed in claim 9, wherein the hygroscopic liquid mixture is an aqueous lithium chloride solution.

11. A method of separating water from air comprising the steps of:
(a) contacting air having water vapour with an hygroscopic liquid mixture to produce a water rich hygroscopic liquid mixture;
(b) heating at least a portion of the water rich hygroscopic liquid mixture to produce a gaseous mixture having water vapour;
(c) condensing at least a portion of the water vapour in the gaseous mixture to produce liquid water and heat energy; and (d) transferring an effective amount of the heat energy to a working fluid including a liquid to effect vapourization of at least a portion of the liquid to produce a working fluid gaseous mixture.

12. The method as claimed in claim 11, wherein the condensing is effected at least in part by the transferring in step (d).

13. The method as claimed in claim 12, wherein the working fluid is contained in a heat pipe.

14. The method as claimed in claim 13, wherein the hygroscopic liquid mixture is an aqueous lithium chloride solution.

15. The method as claimed in claim 14, wherein the condensing is effected at a subatmospheric pressure.

16. A method of recovering water from air comprising the steps of:
(a) contacting air having water vapour with an hygroscopic liquid mixture to produce a water rich hygroscopic liquid mixture;
(b) in a first pressure envelope, heating the water rich hygroscopic liquid mixture to produce a gaseous mixture having water vapour, condensing at least a portion of the water vapour in the gaseous mixture to produce liquid water and a depleted gaseous mixture, and separating the liquid water from the depleted gaseous mixture so as to provide collected liquid water and a depleted gaseous mixture at subatmospheric pressure disposed in a vapour space above the collected liquid water;
(c) effecting fluid pressure communication between a second pressure envelope and the vapour space; and (d) flowing the collected liquid from the first pressure envelope and into the second pressure envelope.

17. The method as claimed in claim 16, wherein the flowing step (d) is effected by draining the collected liquid water by gravity.

18. The method as claimed in claim 17, wherein the second pressure envelope is a tank.

19. The method as claimed in claim 18, wherein the hygroscopic liquid mixture is an aqueous lithium chloride solution.

20. The method as claimed in claim 19, wherein a vacuum pump is fluidly coupled to the vapour space to effect removal of at least a portion of the depleted gaseous mixture to maintain pressure within the vapour space at a subatmospheric pressure, and wherein the vacuum pump is also configured to effect evacuation of the tank.

21. An absorption system for effecting removal of water from atmospheric air by an hygroscopic liquid mixture comprising:
an absorber vessel defining a space for facilitating contact between air having water vapour and an hygroscopic liquid mixture, including:
an input air flow inlet, configured for introducing an input air flow having water vapour into the space;
a depleted air flow outlet, configured for discharging a depleted air flow;
and means for introducing a hygroscopic liquid mixture into the space for effecting contact between the hygroscopic liquid mixture and the input air flow;
a base;

wherein the absorber vessel is rotatably mounted to the base about an axis for effecting positioning of the input air vow inlet at a desired position relative to the axis.

22. A method of recovering water from air comprising:
(a) providing an absorption system for effecting removal of water from atmospheric air flaw by an hygroscopic liquid mixture comprising:
an absorber vessel defining a space for facilitating contact between air having water vapour and art hygroscopic liquid mixture, including an input air flow inlet, configured for introducing an input air flow having water vapour into the space, a depleted air flow outlet, configured for discharging a depleted air flow, and means for introducing a hygroscopic liquid mixture into the space for effecting contact between the hygroscopic liquid mixture and the input air flow; and a base;
wherein the absorber vessel rotatably mounted to the base about an axis for effecting positioning of the input air flow inlet at a desired position relative to the axis;
(b) measuring the direction of atmospheric air flow; and (c) rotating the absorber vessel about the axis so as to effect desired positioning of the input air flow inlet relative to the atmospheric air flow direction in response to the measured atmospheric air flow direction.

23. An absorber vessel defining a space for facilitating contact between air having water vapour and an hygroscopic liquid mixture, including:

an input air flow inlet, configured for introducing an input air flow having water vapour into the space;
a depleted air flow outlet, configured for discharging a depleted air flow;
at least one first liquid inlet spray nozzle, configured for introducing a largest diameter fine size droplet into the space at a first position;
a second liquid inlet spray nozzle, configured for introducing a largest diameter coarse size droplet into the space at a second position disposed in closer proximity to the outlet relative to the introduced largest diameter fine size droplet;
wherein the largest diameter coarse size droplet has a greater diameter than the largest diameter fine size droplet when the same liquid is flowed through each of the first and second liquid inlet spray nozzles under the same operating conditions.

24. The apparatus as claimed in claim 23, wherein the largest diameter coarse size droplet has a diameter which is 100 times greater than a diameter of the largest diameter fine size droplet when the same liquid is flowed through each of the first and second liquid inlet spray nozzles under the same operating conditions.

25. The apparatus as claimed in claim 23, wherein the largest diameter coarse size droplet has a diameter which is 1,000 times greater than a diameter of the largest diameter fine size droplet when the same liquid is flowed through each of the first and second liquid inlet spray nozzles under the same operating conditions.

26. The apparatus as claimed in claim 23, wherein the largest diameter coarse size droplet has a diameter which is 100,000 times greater than a diameter of the largest diameter fine size droplet when the same liquid is flowed through each of the first and second liquid inlet spray nozzles under the same operating conditions.

27. A method of separating water from air comprising the steps of:
providing an absorber vessel defining a space for facilitating contact between air having water vapour and an hygroscopic liquid mixture;
introducing an air flow into the space;
spraying first hygroscopic liquid mixture droplets into the space for effecting contact between the first hygroscopic liquid mixture and the air flow, wherein at least one of the first hygroscopic liquid mixture droplets is a largest diameter fine size droplet; and spraying second hygroscopic liquid mixture droplets into the space downstream of the first hygroscopic liquid mixture droplets for effecting contact between the second hygroscopic liquid mixture and the air flow containing an entrained portion of the first hydroscopic liquid mixture droplets, wherein at least one of the second hygroscopic liquid mixture droplets is a largest diameter coarse size droplet;
wherein the largest diameter coarse size droplet has a greater diameter than the largest diameter fine size droplet.

28. The method as claimed in claim 27, wherein the largest diameter coarse size droplet has a diameter which is 100 times greater than the diameter of the largest diameter fine size droplet.

29. The method as claimed in claim 27, wherein the largest diameter coarse size droplet has a diameter which is 100 times greater than the diameter of the largest diameter fine size droplet.

30. The method as claimed in claim 27, wherein the largest diameter coarse size droplet has a diameter which is 100,000 times greater than the diameter of the largest diameter fine size droplet.

31. A method of separating water from air comprising the steps of:
(a) contacting air having water vapour with a hygroscopic liquid mixture consisting of a supersaturated aqueous solution of lithium chloride to produce a water rich hygroscopic liquid mixture;
(b) heating at least a portion of the water rich hygroscopic liquid mixture to produce a gaseous mixture including water vapour and at least one other gaseous component;
(c) condensing at least a portion of the water vapour in the gaseous mixture to produce liquid water.

32. A method of separating water from air comprising the steps of:
(a) contacting air having water vapour with an hygroscopic liquid mixture to produce a water rich hygroscopic liquid mixture;
(b) heating at least a portion of the water rich hygroscopic liquid mixture with heat generated by a waste heat source to produce a gaseous mixture including water vapour;
and (c) condensing at least a portion of the water vapour to produce liquid water.