GB2519520A

GB2519520A - A water production plant

Info

Publication number: GB2519520A
Application number: GB1318647.3A
Authority: GB
Inventors: Sami Mikati
Original assignee: WINTON ENTPR Ltd
Current assignee: WINTON ENTPR Ltd
Priority date: 2013-10-22
Filing date: 2013-10-22
Publication date: 2015-04-29
Also published as: WO2015059448A1; GB201318647D0

Abstract

A water production plant 10 comprising an atmospheric water generator 36 and a power source 12, 38 powered by gas and comprising a combustion engine 12 and/or a fuel cell 38. The atmospheric water generator is powered by the power source wherein water in the exhaust gas of the combustion engine and/or from the fuel cell and water generated by the atmospheric water generator is captured. The captured water may be bottled in a bottling plant 26 for drinking. The apparatus may be situated near an oil or gas well 1. Carbon dioxide produced by the combustion engine and or fuel cell may be injected into a hydrocarbon well to increase gas or oil production. A later embodiment relates to a method of producing water from gas using the production plant.

Description

A WATER PRODUCTION PLANT

FIELD

The present invention relates to an apparatus for generating drinking water from gas fields and oil fields, which flare gas. The invention has particular utility when dealing with fields of "stranded" gas. The term "stranded" is used to refer to hydrocarbon deposits, and in particular gas deposits, where the transport costs make it uneconomic to invest in infrastructure to deliver the gas to consumers (be that domestic or industrial) at locations geographically remote from the gas deposit.

BACKGRoUND

Every year, billions of dollars worth of natural gas is flared (burnt off) during oil andior gas production. Flaring of gas is particularly common at gas production sites in locations that make it uneconomic to invest in infrastructure to deliver the gas to consumers at locations geographically remote from the gas deposit. In remote locations, a supply of gas in excess of 20mmscfd (million standard cubic feet per day which is equal to 566,367m3 per day) may be large enough to justify some liquefaction technology or the cost of installing a pipeline to the market. Many gas sources do not fall into these categories. Other gas resources, such as gas fields, rather than oil fields producing associated gas, are too small to develop and again fall into the problem of not being big enough to justify the liquefaction technology or a pipeline to market.

The amount of natural gas being flared and vented annually is equivalent to 30 per cent of the European Union's annual gas consumption as of 2012. In Africa alone, the annual amount of gas flared is equivalent to half the continent's power consumption.

Gas tlaring has a global impact on climate change by producing about 400 million tons of greenhouse gas emissions annually. In addition, residents in nearby communities have experienced chronic health problems, including bronchial, thoracic, rheumatic, and eye problems. Other problems include acid rain. Venting, rather than flaring is even worse for the environment as methane has 21 times the Global Warming Potential (GWP) of carbon dioxide.

SUMMARY

According to a first aspect of the invention, there is provided a water production plant having an atmospheric water generator and a power source powered by gas and comprising a combustion engine and/or a fuel cell, wherein the atmospheric water generator is powered by the power source and wherein water in the exhaust gas of the combustion engine and/or from an outlet of the fhel cell and water generated by the atmospheric water generator is captured.

Captured water may be used in the production of drinking water, used to irrigate crops or in the production of bio-fliel.

Advantageously, where a combustion engine is provided it may be used to drive a generator. Advantageously the water production plant may further comprise at least one turbo expander. Turbo expanders are used to reduce gas pressure by gas expansion, and in doing so they provide rotational motion and torque. The water production plant may comprise one or more generators which may be driven by a turbo expander.

Advantageously, the water production plant comprises means for producing drinking (potable) water. It may further comprise a bottling plant for bottling the drinking water.

Additionally or alternatively, the water production plant may comprise a soft drinks plant for production of soft drinks from the drinking water.

Advantageously, the water production plant includes an absorption chiller and/or an adsorption chiller in combination with the combustion engine and/or the fuel cell. The absorption chiller may be operable to condense atmospheric moisture. The moisture may be supplied to a bottling plant. The absorption chiller may absorb heat from the combustion engine and/or the fuel cell.

The combustion engine may be diesel or bio-fuel powered instead of or in addition to being powered by a fuel gas. As used herein "fuel gas" refers to a gas that can be eombusted with air. An example is "natural gas".

One or more heat exchangers may be provided in the water production plant and be operable to distribute heat between elements of the plant. For example, a heat exchanger may be provided downstream of the turbo expander or a pressure reduction part of the water production plant. A second heat exchanger may be provided in communication with the combustion engine. As such, cold from the turbo expander may be provided to the atmospheric water generator. Additionally or alternatively, cold from the turbo expander may be used to cool the bottling plant and/or the combustion engine. Similarly heat from the combustion engine and/or other heat sources may be used to inhibit component of the gas freezing in gas pipes downstream of a turbo expander.

Water from an exhaust of the combustion engine and/or from the outlet of the fad cell may be used as a cooling medium within the water production plant.

Captured water may be treated in an ultraviolet and/or ozone treatment plant operable to subject the captured water to ultraviolet and/or ozone.

Carbon dioxide produced by the combustion engine and/or the fuel cell may used to carbonate the captured water. Where the water production plant includes a soft drinks plant, the carbon dioxide may be used to carbonate soft drinks.

In embodiments comprising a fuel cell, the fuel cell may be powered by the fuel gas and may be operable to generate electricity and/or concentrate carbon dioxide produced by the combustion engine. Carbon dioxide, either concentrated or un-concentrated, may then bc used to carbonate the captured water. The fuel cell is preferably a molten carbonate fuel cell. However other fuel cell technologies may also be used or become available. The carbon dioxide may be concentrated by injection into the fuel cell alongside a slipstream of fuel gas. Thus, carbon dioxide can be separated from the fuel cell outlet more easily because its dilution with air is reduced.

According to a second aspect of the invention, there is provided a method of producing water from stranded gas, comprising generating electricity by combusting the stranded gas in an engine to drive a generator and/or oxidising the stranded gas in a fuel cell; condensing water from the atmosphere using the generated electricity; and collecting thc eondcnscd water and the water from combustion or oxidation of the gas.

Embodiments of the invention thus provide a method of and an apparatus for converting gas, for example stranded gas, into water, thereby reducing gas venting, as well as reducing particulates in the air, and reducing acid rain. Such a system also reduces the strain on ground water and its exploitation and therefore the risk of geological damage. It also reduces light and noise pollution that can result from flaring, thereby reducing disruption to the lives of residents of the area surrounding the stranded gas field. For the owner of a stranded gas field, embodiments of the disclosure provide an extra source of revenue, and may create a source of carbon dioxide which can be used for carbonating water or soft drinks, or may be re-injected into gas and oil wells or injected into a greenhouse or bio-fuel production facility while carbon dioxide

emissions from the gas field are reduced.

Embodiments of the present invention also allow for commercialisation of gas, which would otherwise have been lost to the atmosphere by flaring or otherwise. Using stranded gas that would normally be wasted or undeveloped.

The inventor realised that embodiments of the disclosure improve the commercial viability ofthe individual technologies by combining them together.

The inventor further realised that, looking at the power budget for a water production facility as a whole, that electricity and other infrastructure utilities may require the plant to be connected to a local area power network or distribution centre. The overall dependency on infrastructure of a water production and bottling plant could be significantly reduced or eliminated by placing it in proximity or conjunction with a stranded gas source. Excess power from the water production plant may be used for other purposes.

BRIEF DESCRIPTION OF THE DwINos

Embodiments of the disclosure will now be described, by way of non-limiting example only, with reference to the accompanying Figures, in which: Figure 1 is a diagram of an apparatus for collecting and flaring gas in a stranded gas

field; and

Figure 2 is a schematic diagram of a water production centre.

DEscRipTioN OF SoME EMII0D1MENT5

The inventor has realised that gas, such as stranded gas, could be used to produce drinking water by capturing water from combustion of the gas in a combustion engine and/or use of the gas in a fuel cell and utilising electricity and heat generated from the combustion engine andior the fuel cell to condense atmospheric moisture. Further, by utilising turbo-expansion technology more electricity can be generated and cooling can be provided for condensing atmospheric water. Embodiments described herein have particularly application at wells producing gas volumes in the region of between 0.Smmscf/day (half a million standard cubic feet per day which is equal to 14,158m3 per day) and 20mmsef'day (twenty million standard cubic feet per day which is equal to 566,367m per day).

Figure 1 shows a typical prior art apparatus for flaring gas at a gas field. The apparatus is situated near to an oil and gas well 1 and comprises a compressor 2, a hydrocarbon liquid separator 3 and one or more burners 4. The compressor 2 condenses out intermediate products from the gas stream that may be commercially viable to collect and distribute. Gas is then separated from liquid in the stream by the hydrocarbon liquid separator 3 before being provided to the burner 4 where it is burnt in air. Parts of the apparatus may be owned by a single organisation or may be owned by multiple organisations. For example, a single party may own the stranded gas field, and different steps in the oil and gas extraction contracted out to multiple parties.

The inventor realised that by situating a water production plant near or on a stranded gas field, electricity generated from the stranded gas could meet some or all of the power requirements of the plant.

Figure 2 is a schematic diagram of a water production plant 10 constituting an embodiment of this disclosure. The water production plant 10 may be installed at or close to a stranded gas field, or situated close to or at a well 1 used primarily for the extraction ofoil but from which gas may also be extracted. Fossil fuels other than oil and gas may also be extracted from the well 1. These other products or fuels may be more commercially valuable than the gas and hence may not be stranded.

Alternatively, the well 1 may be a gas well which would not be commercially exploited due to its size.

The water production plant 10 may comprise one or more of a combustion engine 12 and a fuel cell 38. The combustion engine 12 may be provided in combination with and drivingly connected to at least one generator 14 for generating electricity. Electricity output from the fuel cell 38 and/or the generator 14 may be used to power some or all of the water production plant 10. Preferably the entirety of the power requirements for the plant can be generated at the plant 10.

A gas extractor 20 receives gas from the well and/or is used to extract gas from the well 1 using known techniques, such as those described with reference to Figure 1. The gas extractor 20 may be part of the water production plant 10 or may be separate from it.

The gas extractor 20 may comprise a let down station for reducing the pressure of the gas exiting the well 1. AdditionaHy or alternatively, the plant 10 may further comprises at least one turbo-expander 22 coupled to the gas extractor 20 and operable to receive high pressure gas which may then expand in a turbo-expander 22 creating torque. Thus the turbo expander can function as a let down station so as to reduce the gas pressure.

The torque from the turbo expander may be used to drive the generator 14 or a second generator (not shown) providing additional electricity to the water production plant 10.

In some embodiments, the turbo-expander 22 may be incorporated into the gas extractor 20.

The generator 14 and optional further generator may provide enough electricity to power the entire water production plant 10. Accordingly, by situating the water production plant 10 in the proximity of a stranded well 1, the production plant 10 can be provided with its energy source thus obviating the need for a connection to locally distributed power.

In some embodiments, where the combustion engine 12 is present, gas is received at the combustion cnginc 12 cithcr dircctly from thc gas cxtractor 20 or from thc turbo expander 22, and it is burnt in air producing heat, water and carbon dioxide in accordancc with thc cquation below.

CI-J4() + 202(g) -3 CO, + Thus thc cxhaust gas contains uscful amount of watcr vapour which can bc co!lcctcd and uscd in thc production of watcr.

In embodiments having the fuel cell 38, gas extracted from the well 1 may be injected into a fttcl ccli 38, and thc the! ccli 38 may bc opcrablc to convcrt fucl gas into watcr, hcat and carbon dioxidc and to gcncratc clcctricity. Thc fuc! ccli may, for cxamp!c, bc a moltcn carbonatc fhcl cdl. Elcetricity gcncratcd by thc fhcl cdl may bc uscd to power the water production plant 10. The water from the fuel cell may be captured and purified at the water production plant 10.

Thc watcr production plant 10 furthcr compriscs an atmosphcric watcr gcncrator 36 operable to extract water from the atmosphere. The atmospheric water generator 36 may be any means operable to extract water from the atmosphere. The atmospheric water gencrator 36 may reeeivc clcctricity from onc or more of the fuel cell 38 and thc generators 14 (where present). The water generator 36 may further comprise a compressor and/or condenser powered by electricity generated at the plant 10 by the fuel cell or the combustion engine or turbo expander driven generator 14.

Water produced by the atmospheric water generator and one or more of the combustion engine 12 and the thel cell 30 is captured and preferably combined.

The captured water may then be collected and provided to the water treatment faci!ity 16. The water treatment facility 16 may comprise a treatment plant 24 and a storage and bottling plant 26. At the treatment plant 24, water received from the combustion engine 12, fue! cell 38, atmospheric water generator and any other source may be processed and stored. For example the water may be screened/filtered and/or chlorinated to minimize growth of fouling organisms. The water may then be treated using ozone disinfection to oxidise toxic waterborne organisms and/or ultraviolet disinfection. Additionally or alternatively, the treatment plant 24 may use other known potable water purification tcchniqucs to rendcr the cxtractcd water suitable for human consumption. Treated water from the treatment plant 24 may then be passed to the storage and bottling plant 26 where it may be stored for local distribution or bottled for local or regional distribution or export from the stranded gas field. "Bottled" in this context includes placing the water into bulk storage vessels for transport Additionally or alternatively, the storage and bottling plant 26 may incorporate a soft drinks manufacturing plant (not shown) operable to manufacture soft drinks from thc water received from the treatment plant 24.

The storage and bottling plant 26 may also be operable to carbonate the drinking water before or during bottling. In order to do so, the bottling plant 26 may use carbon dioxidc captured from the exhaust gascs of thc combustion cnginc. Additionally or alternatively, the bottling plant 26 may use carbon dioxide produced by the fuel cell 38.

The water production plant 10 may comprise a carbon dioxide capture and treatment plant 25 opcrablc to remove carbon dioxidc from the cxhaust gas received from the combustion engine 12 or from an outlet of the fuel cell 38, puri' the carbon dioxide and convert it into a suitable form for carbonating water and/or soft drinks. Suitable carbon dioxide separation technologies include membrane separation and pressure swing adsorption. This list is not intended to be limiting. When used in combination with the combustion engine 12, the fuel cell 28 may intake carbon dioxide exhaust gas from the combustion engine 12 to concentrate the emitted carbon dioxide before being provided to the carbon dioxide capture and treatment plant 25.

The treated carbon dioxide may then be compressed and stored in a carbon dioxide store 27 coupled to the storage and bottling plant 26. By capturing carbon dioxide produced by the combustion of the fuel gas or created in the fuel cell 38, emissions at the stranded gas field may be significantly reduced while providing a source of carbon dioxide suitable for carbonation of fluids for human consumption.

In addition or as an alternative to using the carbon dioxide for carbonation, waste carbon dioxide from thc combustion engine 12 and/or thc fuel ccli 38 may bc ductcd towards greenhouses to enrich their environment thereby enhancing the rate of growth of plants situatcd thcrcin.

Additionally or alternatively, captured water and carbon dioxide may be used in the production of bio-fuels. For example, carbon dioxide and water may be used to cultivate algae by photosynthcsis so as to producc fats, oils and othcr bio-flicls, as is known in the art. Accordingly, embodiments of the invention provide for conversion of stranded gas into bio fuels.

It will be appreciated that some elements of the water production plant 10, such as the combustion cnginc 12 and fficl cdl 38, cmit hcat whcrcas othcr clcmcnts, such as at the turbo expander 22, absorb heat. Accordingly, the water production plant 10 preferably further comprises a network of pipes connected to heat exchangers to distribute heat throughout the plant 10. For example, in cmbodimcnts whcrc thc turbo-expander 22 is present, a first heat exchanger 28 may be provided downstream of the turbo-expander 22, in gas flow terms. A further heat exchanger (not shown) may also be provided upstrcam of thc turbo-cxpandcr 22 so as to warm thc high prcssurc gas prior to it arriving at the turbo-expander 22.

A second heat exchanger 30 may also be provided at the site of the combustion engine 12 and/or the fuel cell 38, and may be operably coupled to the combustion engine 12, gcncrator 14 andlor thc fucl cdl 38.

A heat exchange medium, such as a gas or water, may be circulated between the heat exchangers via a heat exchange bus (not shown). The flow of the heat exchange medium bct-wccn any of thc hcat cxchangcrs may bc controllcd by a system of valves, which may incorporate electrically operated valves. The valves may be controlled using a computerised control module 32.

Heat generated by the combustion engine 12 and/or the fuel cell 38 may also be used in low temperature desalination plants where the stranded gas field is situated in the proximity of a source of salt water.

In some embodiments, one or more water condensing capture plates 34 may be provided in fluid connection with the heat exchange medium via the heat exchange bus.

The capture plates 34 may be operable to capture atmospheric water and provide it to thc water treatment facility 16 where it may be treated in a similar manner to the water produced by the atmospheric water generator 36.

Heat and/or cold may also be delivered via the heat exchange bus to the atmospheric water generator 36 to enhance atmospheric water extraction.

In addition to combusting gas released from the well 1, the combustion engine 12 may also combust other fuels extracted from the gas field and/or diesel or bio-fuel.

The water production plant 10 may comprise an absorption and/or adsorption chiller (not shown) for regeneration purposes and which can further cool the heat exchange fluid via a further heat exchanger. The absorption chiller may operate to condition the air in the bottling plant or may also be used to produce water. The absorption chiller may use desiccants to extract water from the air. Heat from the heat transfer network may be provided to the absorption chiller to aid water extraction from the aft.

It is thus possible to reduce the environmental impact of flaring gas by converting it to a usable commodity.

Claims

CLAIMSA water production plant having an atmospheric water generator and a power source powered by gas and comprising a combustion engine and/or a fuel cell, wherein the atmospheric water generator is powered by the power source and wherein water in the exhaust gas of the combustion engine and/or from an outlet of the fuel cell and water generated by the atmospheric water generator is captured.
2. A water production plant as claimed in claim 1, wherein the captured water is used for the production of drinking water.
3. A water production plant as claimed in claim 1 or 2, wherein the water production plant further comprises one or more generators driven by a turbo expander powered by the expansion of the gas and/or the combustion engine where a combustion engine is included.
4. A water production plant as claimed in any claims 2 or 3, further comprising a bottling plant for bottling the drinking water.
5. A water production plant as claimed in any preceding claim further comprising an absorption chiller and/or an adsorption chiller in combination with the combustion engine and/or the fuel cell.
6. A water production plant as claimed in any preceding claim wherein the water production plant includes the combustion engine and the combustion engine is operable to combust diesel or bio-ftiel.
7. A water production plant as claimed in any of claims 3 to 7, further comprising one or more heat exchangers operable to distribute heat between one or more of the atmospheric water generator and, where included, the combustion engine, the fuel cell, the turbo-expander, the bottling plant and other elements of the plant as appropriate.
8. A water production plant as claimed in any preceding claim, wherein water from an exhaust of the combustion engine or from the outlet of the fuel ccli is used as a cooling medium within the water production plant.
9. A water production plant as claimed in any preceding claim, further comprising an ultraviolet and/or ozone trealment plant fur subjecting the captured water to ultraviolet and/or ozone treatment.
10. A water production plant as claimed in any of the preceding claims, wherein carbon dioxide produced by the combustion engine and/or the fuel cell is injected in to a hydrocarbon well to increase gas or oil production or is used in the production of bio-fiiel or is used to carbonate the captured water.
11. A water production plant as claimed in any preceding claim, wherein the water production plant includes the fuel cell and the fuel cell is operable to concentrate carbon dioxide produced by the combustion engine.
12. A method of producing water fix,m gas, comprising: generating electricity by combusting the gas so as to drive a generator and/or oxidising the gas in a fuel cell; condensing water from the atmosphere using an atmospheric water generator powered by the generated electricity; and collecting condensed water and the water fixm combustion and/or oxidation.
13. A method of producing water as claimed in claim 12, further comprising producing drinking water from the collected water.
14. A method of producing water as claimed in claim 12, further comprising carbonating thc drinking water using carbon dioxidc produced during combustion or oxidation of the gas.
15. A method of producing water as claimed in claims 13 or 14, further comprising bottling the drinking water.
16. A method of producing water as claimed in any of claims 12 to 15, further comprising: extracting the gas from a gas well; generating electricity by reducing the pressure of the extracted gas using a turbo expander to drive a generator; and condensing water fitm the atmosphere using electricity generated fim the pressure reduction.
17. A method of producing water as claimed in any of claims 12 to 16, further comprising inputting carbon dioxide produced by combustion of the gas into the the! cell.
18. A method of producing water as claimed in any of claims 12 to 17, further comprising producing bio-fitel using water and carbon dioxide produced during combustion or oxidation of thc gas.
19. A method as claimed in any of claims 12 to 18, in which the gas is "stranded" gas.