GB2560016A

GB2560016A - Method and apparatus for obtaining usable water

Info

Publication number: GB2560016A
Application number: GB1703102.2A
Authority: GB
Inventors: Roche Sean
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-02-27
Filing date: 2017-02-27
Publication date: 2018-08-29
Also published as: GB201703102D0

Abstract

A method of obtaining usable water comprises supplying water-bearing vegetable matter 16 to a chamber 12, drawing gas from the chamber to reduce the pressure in the chamber, applying heat to the vegetable matter, causing water to evaporate from it, condensing water out of the gas drawn from the chamber and collecting the condensed water 32 for use. Preferably the vegetable matter comprises cactus. Ideally the residual vegetable matter is used to generate combustible gas. The method may further comprise capturing waste heat from one or both of: a refrigeration system for supply of a coolant to the condenser and one or more pumps used to draw the gas from the chamber, and supplying at least part of the captured waste heat to the vegetable matter during evaporation of the water. Preferably the method further comprises capturing solar heat and supplying at least part of the captured solar heat to the vegetable matter during evaporation of the water. Also claimed is an apparatus 10 for supply of potable water comprising: a chamber, a vacuum pump 18, a heat source 36, a condenser 20 and a water collection 32 and supply arrangement.

Description

(71) Applicant(s):

Sean Roche

ICL Vacuum Cooling, Unit 3B1 Dairy Business Park, Long Lane, Liverpool, L9 7BD, United Kingdom (56) Documents Cited:

GB 2158222 A CN 204359055 U CN 102589269 A

WO 1995/029600 A1 CN 106338190 A US 3436313 A1 (72) Inventor(s):

Sean Roche (58) Field of Search:

INT CL A23L, A23N, A23P, B01D, C02F, F26B Other: EPODOC, WPI, INTERNET, PATENT FULLTEXT (74) Agent and/or Address for Service:

Bartle Read

Liverpool Science Park, 131 Mount Pleasant, LIVERPOOL, L3 5TF, United Kingdom (54) Title of the Invention: Method and apparatus for obtaining usable water Abstract Title: Method and apparatus for obtaining usable water (57) A method of obtaining usable water comprises supplying water-bearing vegetable matter 16 to a chamber 12, drawing gas from the chamber to reduce the pressure in the chamber, applying heat to the vegetable matter, causing water to evaporate from it, condensing water out of the gas drawn from the chamber and collecting the condensed water 32 for use. Preferably the vegetable matter comprises cactus. Ideally the residual vegetable matter is used to generate combustible gas. The method may further comprise capturing waste heat from one or both of: a refrigeration system for supply of a coolant to the condenser and one or more pumps used to draw the gas from the chamber, and supplying at least part of the captured waste heat to the vegetable matter during evaporation of the water. Preferably the method further comprises capturing solar heat and supplying at least part of the captured solar heat to the vegetable matter during evaporation of the water. Also claimed is an apparatus 10 for supply of potable water comprising: a chamber, a vacuum pump 18, a heat source 36, a condenser 20 and a water collection 32 and supply arrangement.

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METHOD AND APPARATUS FOR OBTAINING USABLE WATER

The present invention relates to a method and apparatus for obtaining and supplying usable water. The invention is based on exploitation of vegetable matter for this purpose.

It has been estimated that over a billion people are subject to water stress, meaning that they do not have access to adequate potable water. Those affected are predominantly in the developing world, although economically prosperous regions are not immune to the effects of drought. Water shortage naturally affects regions with hot climates and low rainfall and is regarded as a growing global problem.

So there is a pressing social and commercial need for an economically viable source of potable water which is usable in hot dry regions of the world.

There are various existing technologies which can in principle be applied to supply of usable water to such regions. Many of these are based on desalination of seawater, which can for example be achieved through distillation, membrane-based processes such as reverse osmosis, or purification techniques involving freezing. Such processes are typically expensive in terms of the energy consumed and the required investment in commercial scale plants. Of course such techniques are also dependent on a supply of seawater, and are thus often implemented at coastal sites.

Those regions which are subject to water stress often have large areas of land which, due to the high temperatures and low rainfall it experiences, is not well suited to growing conventional crops, and is thus unproductive.

A separate major issue facing twenty first century society is the need to reduce dependence on combustion of fossil fuels as an energy source, in order to reduce emission of greenhouse gases which are widely held to be causing global warming. One alternative energy source, regarded as favoured over fossil fuel combustion due to its lower net input of carbon to the planet's atmosphere, is based on the use of biomass - vegetable matter which is in itself combustible, or which can be used to produce combustible material (as in the case of so-called biogas processes, which produce combustible gases such as methane). Note that the term vegetable is used throughout this document in its wider sense to refer to plants and plant life, and not in the narrow sense in which it refers to certain food plants alone. One of the challenges in wide-scale adoption of biomass as an energy source is that of growing suitable vegetable matter on a sufficient scale and in an economically viable manner.

The present inventor has recognised that problems relating to supply of usable water can be addressed by use of vegetable matter as a water source. Plants collect and store water from their environment, and subject to provision of an adequately practical and economical means to extract and purify that water, they can be used as a water supply for usage by human populations.

According to a first aspect of the present invention there is a method of obtaining usable water comprising supplying water-bearing vegetable matter to a chamber, drawing gas from the chamber to reduce pressure in the chamber and applying heat to the vegetable matter, causing water to evaporate from it, condensing water out of the gas drawn from the chamber, and collecting the condensed water for use.

According to a second aspect of the present invention there is an apparatus for supply of potable water, comprising a chamber for receiving water-bearing vegetable matter, a vacuum pump for drawing atmospheric gas from the chamber to create a partial vacuum in it to evaporate water from the vegetable matter, a heat source for applying heat to the vegetable matter, a condenser arranged to cause water to condense from the atmospheric gas drawn from the chamber, and a water collection and supply arrangement for collecting the condensed water and supplying it for use.

The gas drawn from the chamber will typically be a mixture of air and water vapour.

The invention makes it possible to exploit plant crops as a source of usable water.

The reduced pressure in the chamber reduces the boiling point of water contained in the vegetable matter. Applied heat maintains the matter at a temperature above the boiling point. The vapour given off by boiling is then pulled into a separate condenser chamber where it is condensed back into a liquid and collected for further use.

It is especially preferred that the vegetable matter used in the method comprises cactus. Cacti are well suited to growing in the types of hot arid environment often subject to water shortage. Cacti can be grown on land unsuitable for other more conventional crops. Some varieties are self-seeding and extremely easy to grow. Hence growing and harvesting cacti makes it possible to commercially exploit what might otherwise be regarded as waste land. Some varieties of cactus are fast growing. Cacti are well adapted to hot environments, being effective at extracting water and storing it. The water content of a cactus can be of the order of 85% by mass, making a cactus an effective reservoir of water if a suitable means can be provided of extracting and adequately purifying that water.

Calculations by the inventor demonstrate that water yield from cactus cultivated for use in accordance with the present invention can be high enough to make the process both practical and economically viable, as a means of supplying communities in hot regions of the world with usable water.

One potential obstacle to such use of cacti is that water extracted from them contains malic acid, which has a strong sour taste. Although used in small quantities as a flavouring and food additive, malic acid is also an irritant. It thus needs to be at least partially removed from water extracted from cacti if that water is to be used for human consumption. The method and apparatus according to the present invention perform that function. It is found that under vacuum malic acid is not evaporated along with the water but instead tends to crystallise at low pressure, and so remains in situ.

As well as water, the method according to the present invention provides as an output a residue of dried vegetable matter. Thanks to its low water content this residue is well suited to use as fuel. That is, it forms valuable biomass which may itself be combustible, or may be used e.g. in biogas processes to produce combustible material, or may be used in other ways to release usable energy from it. The method according to the present invention preferably further comprises collecting the vegetable residue and supplying it use as biomass. The residue may in some embodiments be subject to further treatment to improve its properties as a fuel. It may for example be sun dried to further reduce its moisture content.

Where the vegetable matter employed comprises cactus, the residue will typically comprise malic acid, concentrated due to the removal of water. Malic acid has commercial value, e.g. as a food additive. The method according to the present invention preferably further comprises collecting malic acid from the vegetable residue and supplying it for use.

The apparatus used to extract water from the vegetable matter may, geographically, be sited close to the land on which that matter is grown, to minimise transportation requirements. The invention lends itself to moderate scale plants at a community level, although it can be scaled for larger plants.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic representation of major functional components of a water extraction plant embodying the present invention; and

Figure 2 is a plan view of a practical water extraction plant embodying the present invention in which certain features are represented diagrammatically.

Principle of operation

The present invention involves exploitation of vegetable matter as a source of usable water. More specifically, according to the present embodiment, it provides water which is potable - suitable for human consumption. The water is extracted from the vegetable matter by a process in which it is placed under a partial vacuum (i.e. a pressure less than atmospheric pressure), with heat being applied to prevent its temperature from falling below the evaporation point. The boiling point of water is reduced as its pressure is reduced, so that the application of a partial vacuum causes water in the vegetable matter to evaporate. The resultant water vapour can then be condensed and collected to provide a supply of water which has been at least partially purified, and can be used for human consumption or other purposes. In evaporating, the water absorbs heat (the latent heat of vaporisation) from its surroundings, causing the vegetable matter to cool. This cooling effect could cause freezing of water in the vegetable matter if unchecked. Heat is applied to resist such freezing and to maintain a temperature above the evaporation point.

Simplified system

The apparatus used in the present embodiment has something in common with known apparatus used in vacuum cooling, a process used to chill and preserve crops and other produce. Figure 1 is a schematic representation of a suitable system 10.

A processing chamber 12 within an enclosure 14 receives the vegetable matter 16 to be processed. The diagram shows a single tray containing the vegetable matter but in practice better use will be made of the volume within the enclosure 14, which may for example have shelving throughout its depth to receive trays bearing the vegetable matter. The enclosure 14 has an opening enabling the vegetable matter 16 to be introduced, but is able to be sealed so that a partial vacuum can be created within it. It may have a door with a suitable peripheral seal for this purpose (not shown in Figure 1).

The term partial vacuum is used throughout this document to refer to a pressure less than external atmospheric pressure.

Pressure in the processing chamber 12 is reduced in use by means of a vacuum pump 18. Figure 1 symbolically indicates a single vacuum pump but multiple pumps may be used in a practical embodiment. The vacuum pump 18 is connectable to the processing chamber 12 via a water condenser 20 and isolating valves 22, 23 on either side of the water condenser. Within the water condenser 20 are cooled surfaces on which water vapour drawn from the processing chamber 12 by the vacuum pump 18 condenses. The water condenser 20 comprises a condenser enclosure 21 through which the vapour/air is drawn, this enclosure forming a condenser chamber 25 within which the condensed water collects. The water condenser 20 is able to discharge condensed water to a reservoir 32 via a discharge valve 34.

In the present embodiment the water condenser 20 is cooled by a refrigeration system of a type which, in this embodiment, runs on conventional principles, having a compressor 24 which supplies gaseous refrigerant to an air blown refrigeration condenser 26, from which the now liquid refrigerant reaches an expansion valve 28 leading to a refrigerant conduit 30 within the water condenser 20. The refrigerant conduit 30 takes the form of conventional evaporator coils, in the present embodiment (they form the evaporator with respect to the refrigeration system 22 - evaporation of the refrigerant takes place within them - although they also form part of the condenser 20 - condensation of water takes place around them). Suitable refrigerants include (a) ammonia and (b) glycol.

A heating arrangement 36 is provided within the processing chamber 12 for applying heat to the vegetable matter 16, to prevent it from freezing. The nature of this heating arrangement and the manner in which it is driven will be considered further below.

Operation of the system

Operation of the system 10 involves the following steps.

The vegetable matter typically requires processing to prepare it for use. Where the matter in question is cactus, it is macerated to facilitate release of water. Suitable machinery for this purpose is known to the skilled person and will not be described herein. Some other forms of vegetable matter will also require maceration. The vegetable matter needs to be delivered into the processing chamber 12, for which purpose it may be carried in open-topped trays or troughs placed on shelves inside the chamber. In other embodiments other means of delivery, better suited to automation, may be employed.

Once the vegetable matter has been loaded into the processing chamber 12, the chamber is sealed and processing begins. The vacuum pump 18 is operated to draw atmospheric air out of the processing chamber 12, reducing pressure inside it. Initially the air may be drawn through a path which bypasses the water condenser 20 (this path is not shown in Figure 1, which is somewhat simplified). This is not essential - air may be drawn through the water condenser 20 from start-up. When the pressure has been reduced sufficiently that water in the vegetable matter has begun to boil, the bypass path is closed and the atmosphere from the processing chamber 12 is instead drawn through the water condenser 20. This atmosphere contains water vapour evaporated from the vegetable matter, which is collected in the water condenser 20.

The evaporation of the water from the vegetable matter removes heat (the latent heat of vaporisation) and thus has a chilling effect. Unchecked, this would cause the material in the chamber 12 to fall below the evaporation point, and even to freeze. Heat applied by the heating arrangement 36 is variable. The applied heat is controlled, during processing, to maintain the temperature inside the chamber 12 above the boiling point of water. Note that this does not imply that the temperature is high since as the pressure drops, the temperature required to boil the water falls - a temperature as low as 3 degrees Celsius may be reached.

Periodically, the water condenser 20 may reach something approaching its full capacity. The process of de-pressurising the chamber 12 is then suspended and water is discharged from the water condenser 20. This involves closing the isolating valves 22, 24, so that the vacuum pump 18 is disconnected from the chamber 12 but ingress of atmospheric air to the chamber 12 is prevented, and opening the discharge valve 34 to allow the water to discharge into the reservoir 32. Then the discharge valve 34 is closed, the isolating valves 22, 24 are opened, and the process of drawing atmospheric gas from the chamber 12 through the water condenser 20 to collect water continues.

Other physical arrangements and operating procedures could be adopted for discharging water from the condenser.

When the process is complete, pressure in the chamber 12 is equalised, the dried residue of the vegetable matter is removed and the chamber 12 is re-loaded ready for another operating cycle. Multiple cycles can be carried out in a day.

In small scale trials it has been found that the water collected is suitable for human consumption.

The residual material removed from the chamber 12 at the end of the process comprises (a) dewatered biomass well suited to use in energy production and (b) malic acid, concentrated by the removal of water, which can be collected and used for commercial purposes. The collected biomass may be in a suitable form for combustion as fuel, or may be further dried and then burnt, or may be used in manufacture of combustible gas such as methane through a known biogas process.

A practical system

Figure 2 shows the physical layout of a real plant 100 operable according to the principles described with reference to Figure 1. The enclosure 14 forming the processing chamber 12 is in this example a substantial cuboidal metal structure whose periphery is indicated by a rectangle in the drawing and is reinforced by substantial metal beams indicated at 38. It has in this example a sliding door 40 which is opened for loading and unloading, and which has a peripheral seal (not shown) to enable the chamber 12 to be sealed against ingress of air. This embodiment has a bank of three vacuum pumps 18 connected through a conduit 42 to the chamber 12, and a bank of three compressors 24 for the refrigeration system. The refrigeration condenser 26 is an air blown device using electric fans. The water condenser 20 feeds the reservoir 32, as described above with reference to Figure 1.

Energy considerations

There are several energy consuming systems in the plant:

the compressors 24 used for refrigeration;

the refrigeration condensers 26, whose fans require energy;

the vacuum pumps 18; and the heating arrangement 36.

Of these, the compressors 24, condensers 26 and vacuum pumps 18 all produce waste heat in operation.

It is desirable to minimise or even avoid a requirement for input of energy to the plant from such sources as the electrical grid or on-site generators consuming fossil fuels, not only because such input energy is potentially costly, and its production environmentally burdensome, but because the plant may be located close to the point of production of the vegetable matter, in locations where such energy sources are not available or are difficult to install.

In the illustrated plant 100, the heating arrangement 36 can make use of any or all of the following heat sources to supply heat to the vegetable matter during its processing:

waste heat from the plant's other energy consuming systems;

heat released from biomass;

ambient heat from the plant's environment;

heat derived from a different renewable energy source receiving energy from the plant's environment.

The plant 100 has a heat exchanger 44 which receives heat from one or more of these sources. Thus in Figure 2, a conduit 46 takes heated coolant (which could be in the form of air or of liquid coolant) from the vacuum pumps 18 to the heat exchanger. A further conduit 48 leads heated coolant (which may be in the form of warm air, for example) from the refrigeration condenser 26 to the heat exchanger 44. The heat exchanger 44 may also receive heat from a solar energy collection system 50, e.g. of the type which supplies fluid heated by the sun. In suitable environments the heat exchanger 44 may be warmed by passage of ambient air, as indicated by arrows 52.

The heat exchanger 44 serves to heat a working fluid which carries heat to the vegetable matter in the chamber 12 via conduits 36. Its thermal output is, as noted above, varied in operation to maintain a temperature in the chamber 12 above the evaporation point of water at the prevailing pressure.

The other major energy consuming systems of the plant 100 - the condensers, compressors and vacuum pumps - all need to be mechanically driven. In the present embodiment they are run by electric motors, but the electricity required for the purpose is obtained from a local renewable source. Figure 2 shows a bank 56 of photovoltaic solar cells whose output is used to charge an energy store 58 in the form of one or more electrical batteries. Vanadium redox type batteries are well suited to this application for their longevity, potentially high capacity, and their ability to withstand deep discharge and long periods of disuse. The DC electrical output of the energy store 58 may be conditioned to a form suitable for use by the plant through an inverter 60 and related componentry. Other renewable energy sources such as wind turbines could be adopted in other embodiments.

The present embodiment of the invention is thus able to provide a plant which is either self-sufficient in energy terms, or which has low requirements for input energy from non-renewable sources (e.g. to supplement renewable sources when they happen to be unavailable). This makes the invention well suited to use in developing countries and in inaccessible areas. Plant can be sited close to the land on which the vegetable matter is grown, minimising transportation costs and making this a process that can be adopted at a local community level.

Vegetable matter

The vegetable matter used in the process may be cultivated specifically for the purpose. It is envisaged for example that where it takes the form of cactus, land may be harvested in rotation to keep the plant active for much or all of the year. Cacti can grow rapidly, are able to survive drought, require little attention and can self-seed, making such cultivation especially productive and straightforward.

But in other applications the relevant vegetable matter may take the form of waste or discarded food. Large volumes of food are routinely disposed of by many communities and the present invention makes it possible to exploit these, practically and commercially, rather than allowing them to go to waste and requiring unproductive disposal. Uncultivated plants such as weeds could also be utilised.

Cactus may for example comprise 80 to 90% water by mass, with 1-2% by mass being malic acid and the remainder being solid matter that forms the residue after processing. So a metric tonne of cactus can in principle yield 800 to 900 litres of potable water, 10-20 litres of acid, typically predominantly malic acid, and 80 kg. or more of biomass for use in energy generation. Little or none of the material grown goes to waste.

Embodiments are non-limiting

The embodiments described above serve as illustrations rather than as limitations on the scope of the invention as determined by the appended claims. It must be understood that in numerous respects the apparatus used in implementation of the invention may differ from what is disclosed herein. For example while a conventional refrigeration plant is used to cool the water condenser 20, other types of cooling system are of course widely known (e.g. using heat pumps such as Peltier devices) so there are other design options in this respect. Any suitable means may be employed for loading and unloading vegetable matter to and from the chamber 12, perhaps by means of large containers which can be inserted and removed quickly to minimise down time between operating cycles. There are numerous other such options with respect to various aspects of the plant's function, as will be apparent to the skilled person.

Claims

1. A method of obtaining usable water comprising supplying water-bearing vegetable matter to a chamber, drawing gas from the chamber to reduce pressure in the chamber and applying heat to the vegetable matter, causing water to evaporate from it, condensing water out of the gas drawn from the chamber, and collecting the condensed water for use.

2. A method as claimed in claim 1 further comprising treating the vegetable matter to promote evaporation of water from it.

3. A method as claimed in claim 2 wherein the said treatment comprises macerating the vegetable matter prior to evaporation of the water from it.

4. A method as claimed in claim 1 or claim 2 comprising supplying the collected water for human consumption.

5. A method as claimed in claim 1 or claim 2 further comprising collecting residual vegetable matter after evaporation of the water from it and supplying it as an energy source.

6. A method as claimed in claim 5 in which the residual vegetable matter is used to generate combustible gas.

7. A method as claimed in any preceding claim in which the vegetable matter comprises cactus.

8. A method as claimed in claim 6 in which malic acid is crystallised during evaporation of the water from the cactus.

9. A method as claimed in claim 7 or claim 8 in which malic acid is collected from residue of the cactus after evaporation of the water from it.

10. A method as claimed in any preceding claim in which, during the process of evaporating water from the vegetable matter, a condenser is employed to condense the water, the condenser being periodically isolated from the chamber and opened to discharge water from it to a reservoir.

11. A method as claimed in any preceding claim comprising capturing waste heat from one or both of (a) a refrigeration system for supply of coolant to the condenser; and (b) one or more pumps used to draw the gas from the chamber, and supplying at least part of the captured waste heat to the vegetable matter during evaporation of the water from it.

12. A method as claimed in any preceding claim further comprising capturing solar heat and supplying at least part of the captured solar heat to the vegetable matter during evaporation of the water from it.

13. A method as claimed in any preceding claim further comprising generating power from a renewable source proximal to the chamber and using the generated power to drive either or both of (a) a refrigeration system for supply of coolant to the condenser; and (b) one or more pumps used to draw the gas from the chamber.

14. A method as claimed in any preceding claim further comprising generating power from a residue of the vegetable matter remaining after evaporation of water from it, and driving either or both of (a) a refrigeration system for supply of coolant to the condenser; and (b) one or more pumps used to draw the gas from the chamber using the generated power.

15. An apparatus for supply of potable water, comprising a chamber for receiving water-bearing vegetable matter, a vacuum pump for drawing gas from the chamber to create a partial vacuum in it to evaporate water from the vegetable matter, a heat source for applying heat to the vegetable matter during application of the partial vacuum, a condenser arranged to cause water to condense from the atmospheric gas drawn from the chamber, and a water collection and supply arrangement for collecting the condensed water and supplying it for use.

16. An apparatus as claimed in claim 15 further comprising a macerator for macerating the vegetable matter to promote evaporation of water from it.

17. An apparatus as claimed in claim 15 or claim 16 in which the condenser is configured to collect the condensed water and to discharge it to a reservoir.

18. An apparatus as claimed in claim 17 in which the condenser is provided with a valve arrangement for isolating the condenser from the chamber, enabling water collected in the condenser to be discharged to the reservoir without loss of vacuum in the chamber.

19. An apparatus as claimed in any of claims 15 to 18 in which the vacuum pump is connectable to the chamber via the condenser, so that the vacuum pump draws the gas from the chamber through the condenser.

20. An apparatus as claimed in any of claims 15 to 19 in which the chamber contains cactus.

21. An apparatus as claimed in any of claims 15 to 20, further comprising equipment for collection of malic acid from the vegetable matter.

22. An apparatus as claimed in any of claims 15 to 21, further comprising equipment for generating power from a residual part of the vegetable matter after evaporation of the water from it.

23. An apparatus as claimed in claim 22 in which the said equipment is configured to capture combustible gas released from the residual part of the vegetable matter.

24. An apparatus as claimed in claim 22 in which the said equipment is configured to burn the residual part of the vegetable matter.

25. An apparatus as claimed in any of claims 15 to 24 further comprising means for capturing waste heat from one or more of:

the vacuum pump(s);

a refrigeration system for associated with the condenser;

and the said heat source comprises means for supplying at least part of the captured waste heat to the chamber.

26. An apparatus as claimed in claim 25 in which the means for capturing waste heat comprises at least one heat exchanger arranged to receive waste heat from at least one of (a) the vacuum pump(s) and (b) the refrigeration system.

27. An apparatus as claimed in claim 25 or claim 26 comprising a heat exchanger which serves to heat a working fluid supplied to the chamber to supply heat to the vegetable matter.

28. An apparatus as claimed in any of claims 15 to YI further comprising a solar energy system for supplying heat to the chamber.

29. An apparatus as claimed in any of claims 15 to 28 further comprising a renewable energy generation system for generating electrical power to run the apparatus.

30. An apparatus as claimed in claim 29 in which the renewable energy generation system comprises photovoltaic cells.

31. An apparatus as claimed in claim 22 in which the said equipment for generating power is configured to supply the generated power to the apparatus to operate it.

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Application No: GB1703102.2 Examiner: Mr Peter Davies