AU2021203267A1

AU2021203267A1 - A method for reducing greenhouse gas emissions

Info

Publication number: AU2021203267A1
Application number: AU2021203267A
Authority: AU
Inventors: Ian Porter
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-05-21
Filing date: 2021-05-21
Publication date: 2021-12-09

Abstract

A method for reducing greenhouse gas emissions, the method comprising the steps of: reacting carbon dioxide with hydrogen at a methanation facility to produce a synthetic methane gas; liquefying the synthetic methane gas to produce a liquefied synthetic methane; transferring the liquefied synthetic methane to a facility comprising a gas turbine; regasifying the liquefied synthetic methane; combusting the synthetic methane gas in the gas turbine; capturing carbon dioxide produced by the combustion of the synthetic methane gas to provide captured carbon dioxide; liquefying the captured carbon dioxide to produce liquefied captured carbon dioxide; and transferring the liquefied captured carbon dioxide to the methanation facility. 1/1 DRAWINGS b0 *Ifb UC 8 'Np 'N1

Description

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A METHOD FOR REDUCING GREENHOUSE GAS EMISSIONS TECHNICAL FIELD

[0001] The present invention relates to a method for reducing greenhouse gas emissions associated with the present state of the art of the Liquefied Natural Gas (LNG) industry.

BACKGROUND ART

[0002] The greenhouse gas effect, in which carbon dioxide and other greenhouse gases in the atmosphere act like a blanket, absorbing IR radiation and preventing it from escaping into outer space, was first described by former NASA scientist Dr James Hansen in 1988. In a study published in 2016, Dr Hansen warned that climate models do not properly reflect and mitigate the pace of global warming and climate change. Even with a global warming of'only'2° Celsius coastal areas would be threatened by the imminent rise of sea level and the associated extreme weather conditions.

[0003] In December 2015, the international community agreed to limit the rise of the mean temperature of the earth's atmosphere to below 2°C compared to the pre industrial level, thereby limiting climate change. To achieve this global political goal, the European Union - for example - must reduce its emissions of greenhouse gases by 80% to 95% by 2050 compared to 1990 levels.

[0004] The combustion of fossil fuels releases carbon dioxide that has been buried for millions of years. In 2017, it is estimated that the combustion of fossil fuels released 36.15 GigaTonnes of carbon dioxide to the atmosphere, which represents 76% of total global emissions.

[0005] In 2017, the Liquified Natural Gas (LNG) industry contributed 7.21 GigaTonnes of carbon dioxide, which represents 20% of global carbon dioxide fossil fuel emissions. Australia is the world's second largest producer of LNG and in 2018, the carbon dioxide emissions from the 10 currently built LNG plants reached almost 50 million tonnes. However, these emissions only relate to the carbon dioxide released through combustion within the LNG operation and the venting of production carbon dioxide gases separated from the natural gas prior to the liquefaction process, these being the so called "Scope 1 and 2 emissions". This total does not include the burning of the LNG product in foreign countries, which is estimated to emit an additional 780 million tonnes of carbon dioxide (11% of global LNG related carbon dioxide emissions), referred to as "Scope 3 emissions".

[0006] The current annual global LNG production level of approximately 380bn tonnes is expected to rise to 700bn tonnes by 2035. This 84% increase in LNG production will lead to an equivalent increase in LNG associated carbon dioxide emissions unless mitigating action is taken.

[0007] Although carbon dioxide may be captured and sequestered, sequestration results in significant disposal and monitoring costs with a long-tail monitoring liability as well as uncertainties as to the on-going integrity of the storage site's ability to contain the large reserves of carbon dioxide involved.

[0008] Thus, there would be an advantage (both environmentally and commercially) if it were possible to capture and recycle carbon dioxide emissions and ventings prior to its eventual sequestration while maximising use of existing infrastructure and facilities.

[0009] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

SUMMARY OF INVENTION

[0010] The present invention is directed to a method for reducing greenhouse gas emissions, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

[0011] In a first aspect, the invention resides broadly in a method for reducing greenhouse gas emissions, the method comprising the steps of:

a. Reacting carbon dioxide with hydrogen at a methanation facility to produce a synthetic methane gas;

b. Liquefying the synthetic methane gas to produce a liquefied synthetic methane;

c. Transferring the liquefied synthetic methane to a facility comprising a gas turbine; d. Regasifying the liquefied synthetic methane; e. Combusting the synthetic methane gas in the gas turbine; f. Capturing carbon dioxide produced by the combustion of the synthetic methane gas to provide captured carbon dioxide; g. Liquefying the captured carbon dioxide to produce liquefied captured carbon dioxide; and h. Transferring the liquefied captured carbon dioxide to the methanation facility.

[0012] In a second aspect, the invention resides broadly in a method for reducing greenhouse gas emissions, the method comprising the steps of:

a. Obtaining a source of carbon dioxide and a source of hydrogen;

b. Reacting the carbon dioxide with the hydrogen at a methanation facility to produce a synthetic methane gas;

c. Liquefying the synthetic methane gas at a liquefaction facility to produce a liquefied synthetic methane;

d. Transferring the liquefied synthetic methane to a facility comprising a gas turbine;

e. Regasifying the liquefied synthetic methane using a heat exchanger associated with the facility comprising the gas turbine;

f. Combusting the synthetic methane gas in the gas turbine;

g. Capturing carbon dioxide produced by the combustion of the synthetic methane gas to provide a captured source of carbon dioxide; and

h. Transferring the captured source of carbon dioxide from the facility comprising the gas turbine to the methanation facility.

[0013] The terms "reactants", "reaction products", "reaction by-products", and "reaction co-products" as used herein are terms with a broad meaning and are given their ordinary and conventional meaning to those skilled in the art, and refer without limitation to molecules and/or compounds used in and/or produced by electrolysis, methanation, combustion, decomposition, hydrogenation, or the like.

[0014] The term "receiving terminal" as used herein is intended to refer to a facility which has the ability to perform one or more of the functions: load or unload a liquefied gas, store a liquefied gas, regasify a liquefied gas, liquefy a gas, deliver a gas into a pipeline, and the like.

[0015] The term "liquefied" as used herein is intended to refer to a compound or similar substance that has been processed in a manner such that it has become a liquid or been provided with fluid-like properties.

[0016] The method for reducing greenhouse gas emissions may be conducted at one or more locations. Any suitable location may be used. In some embodiments, at least some of the steps of the method of the present invention may be conducted at locations at which a source of carbon dioxide and/or a source of hydrogen is available. Such sources of carbon dioxide and/or hydrogen may include a facility comprising a gas turbine, a liquefaction facility, a methanation facility, a hydrogen production facility, or any suitable combination thereof. In other embodiments of the invention, carbon dioxide and/or hydrogen may be captured at a separate facility (such as a steelmaking plant or similar industrial facility) and the captured gas transferred to a location at which one or more steps of the method may be conducted.

[0017] The steps of the method of the present invention may be conducted at one or more locations. More preferably, the steps of the method of the present invention may be conducted at two or more locations. For instance, obtaining a source of carbon dioxide and combusting synthetic methane gas may be conducted at one location or may be conducted at different locations. For instance, liquefaction of carbon dioxide may be conducted at the same location as the carbon dioxide was captured, or the carbon dioxide may be liquefied at a different location. The steps of the method of the present invention may be conducted in any suitable facility. For instance, the facility may be an existing facility, a greenfield facility, a brownfield facility, a converted facility, a relocated facility (as in a facility relocated from another location, for instance to take advantage of more favourable conditions at the site of the relocation), or any suitable combination thereof. In an embodiment of the invention, the steps of the method of the present invention may be conducted in an existing LNG facility. In this instance, it is envisaged that dual utilisation of the same facility may reduce costs and extend the productive life of existing infrastructure.

[0018] It is envisaged that in use, one or more of reactants, reaction products, reaction by-products, reaction co-products, or the like, may be transferred from one location to another location in order to complete one or more steps of the method. The one or more of the reactants, reaction products, reaction by-products, reaction co products, or the like, may be transferred from one location to another location via a receiving terminal. The different locations may be relatively close to one another or may be relatively distant to one another. In this instance, it is envisaged that one or more of the reactants, reaction products, reaction by-products, reaction co-products, or the like, may be transferred via a pipeline system, or by ship, road or rail tankers, or any suitable combination thereof. However, it will be understood that the method of transferring the one or more of the reactants, reaction products, reaction by-products, reaction co products, or the like, may vary depending on the type of material being transferred and the conditions under which it is transferred, the volume of materials being transferred, the distance between the locations and the type of infrastructure available.

[0019] It is envisaged that in use, one or more of the reactants, reaction products, reaction by-products, reaction co-products, or the like, may be liquefied or converted to a dense phase or supercritical state to make it easier to transport and store the gas. Said reaction products may also be in the two phase (i.e. gas and liquid) state. It will be understood that liquefaction may include chilling and/or pressurising a compound or similar substance to its ideal cryogenic transport and/or storage pressure and temperature. In this instance, it is envisaged that compressing a compound in its gaseous or liquid state to a dense phase state may provide the compound with properties of both a liquid and a gas. However, it will be understood that the form of the compound may vary depending on the temperature and pressure applied in the context of the compound's phase diagram and whether the compound is pure or comprises a mixture of compounds. In an embodiment of the invention, the hydrogen may be converted to ammonia before it is transferred from one location to another location.

[0020] In an embodiment of the invention, one or more of the reactants, reaction products, reaction by-products, reaction co-products, or the like, may be stored and/or transported in refrigerated and pressurised fluid containers. Any suitable refrigerated and pressurised fluid container may be used. Preferably, however, the refrigerated and pressurised fluid container may be of sufficient size, shape and configuration to manage stress induced by the internal pressure of the fluid contained therein, optimise the ratio of the fluid mass to container mass and maximise the filling of available storage and/or transport space. In some embodiments, the refrigerated and pressurised fluid containers may be VOTRANSTM or ENZG@ containment systems manufactured by Enersea Transport and described in US patent number 9,033,178.

[0021] While carbon dioxide emissions may be captured during transit of any suitable ship, road or rail tanker, it is envisaged that, in some embodiments, carbon dioxide emissions may be captured during transit of ships, road or rail tankers transferring carbon dioxide, hydrogen, synthetic methane gas and/or ammonia. In an embodiment of the invention, a ship, road or rail tanker transferring carbon dioxide, hydrogen, synthetic methane gas and/or ammonia, may use ammonia and/or hydrogen fuel cells for motive power and utility generation. In this instance, it is envisaged that using ammonia and/or hydrogen fuel cells for power generation may reduce greenhouse gas emissions. Alternatively, the ship, road or rail tanker transferring carbon dioxide, hydrogen, synthetic methane gas and/or ammonia, may be powered conventionally, may be driven by a gas turbine or diesel engine which may be fuelled partly (i.e. co-fired) or completely by hydrogen or ammonia, solely or together with other fuels such as methane, diesel fuel or other fossil derived fuel products, may use a hybrid propulsion system, or the like. In this instance, it is envisaged that the ship, rail or road tanker may be provided with an apparatus for capturing carbon dioxide emissions in transit. Any suitable conventional post-combustion carbon capture and sequestration apparatus may be used, and no specific discussion of this is necessary. In an embodiment of the invention, the captured carbon dioxide may be sequestered using a source of calcium. In use, it is envisaged that the resulting calcium carbonate may be disposed of in the ocean or transferred to a processing facility to release the sequestered carbon dioxide.

[0022] Preferably, the method for reducing greenhouse gas emissions comprises the step of obtaining carbon dioxide and hydrogen from respective sources thereof. The carbon dioxide and hydrogen may be obtained from any suitable source thereof. The carbon dioxide and/or the hydrogen may be obtained from one or more sources.

The source of carbon dioxide and the source of hydrogen may be obtained from the same location or may be obtained from different locations.

[0023] Any suitable source of carbon dioxide may be used. For instance, the source of carbon dioxide may be carbon dioxide captured from pre-combustion processes (such as syngas production, steam reforming, partial oxidation of carbon-based fuels, gasification of fossil fuels or biomass, and the like), post-combustion processes (such as combustion of carbon-based fuels, power generation facilities, industrial sources (such as steelmaking plants), 'flaring off' of methane at oil fields, production and/or processing facilities, and the like), liquefaction facilities (such as boil-off gas, gas turbines, power generation for heat exchangers, and the like), oxy-fuel combustion, direct air capture, emissions of the cement industry, or any suitable combination thereof. Alternatively, the source of carbon dioxide may be carbon dioxide captured during pre processing of crude natural gas, decarbonation of calcium carbonate, and the like. In an embodiment of the invention, the source of carbon dioxide may comprise carbon dioxide obtained from one or more locations. For instance, the source of carbon dioxide may comprise carbon dioxide captured from emissions of a power generation facility or from a liquefaction facility, and boil-off gas from liquefied carbon dioxide storage. Alternatively, the source of carbon dioxide may comprise carbon dioxide captured from pre-processing crude natural gas and steam methane reforming.

[0024] In an embodiment of the invention, the source of carbon dioxide may be carbon dioxide associated with produced natural gas. In this instance, it is envisaged that the source of carbon dioxide may be obtained by adsorbing carbon dioxide in crude natural gas into an amine solvent or a solid adsorbent or by membrane separation technologies.

[0025] In an embodiment of the invention, the source of carbon dioxide may be carbon dioxide emissions resulting from combustion of carbon-based fuel (such as coal, oil, natural gas, methane gas, synthetic methane gas, and the like) at power generation facilities and/or an industrial source. In this instance, the source of carbon dioxide may be obtained from the combustion gases by adsorption, absorption, cryogenic separation and/or membrane separation.

[0026] In an embodiment of the invention, the source of carbon dioxide may be carbon dioxide produced as a by-product of steam methane reformation or syngas production. In this instance, carbon monoxide produced as a by-product of steam reforming methane (to produce hydrogen) may undergo a water-gas shift reaction to convert the carbon monoxide into carbon dioxide and hydrogen.

[0027] In an embodiment of the invention, the source of carbon dioxide may be direct air capture. In another embodiment of the invention, the source of carbon dioxide may be carbon dioxide produced by combustion or'flaring off' of methane at oil fields or at production and/or processing facilities.

[0028] It is envisaged that the carbon dioxide may be obtained from multiple sources.

[0029] Preferably, however, the carbon dioxide may be in a form which is relatively easy to transport and store. For instance, the carbon dioxide may be a gas, a pressurised gas, a solid, a liquid, a subcritical fluid, a supercritical fluid, a cryogenic liquid, in a dense phase state, a carbon dioxide-adsorbent system, a carbon dioxide solvent system, a carbon dioxide-carrier system, or any suitable combination thereof. In use, it is envisaged that the carbon dioxide may be in a single phase, may be in two phases in equilibrium, or may be in three phases in equilibrium. For instance, the carbon dioxide may comprise a liquid phase and a gas phase in equilibrium, a supercritical fluid, or a dense phase. However, it will be understood that the form of the carbon dioxide may vary depending on the temperature and pressure used to liquefy the carbon dioxide.

[0030] In an embodiment of the invention, the carbon dioxide may be liquefied after it has been captured to form a liquefied captured carbon dioxide. It is envisaged that the liquefied captured carbon dioxide may be carbon dioxide in a liquid or dense phase state. In an embodiment of the invention, the carbon dioxide may be captured on an adsorbent material. Any suitable adsorbent material may be used. For instance, the adsorbent material may be a hyper-crosslinked polymer, an amine-based solvent, amine-functionalised polymers, and the like.

[0031] Any suitable source of hydrogen may be used. For instance, the source of hydrogen may be hydrogen gas produced by electrolysis of water, steam reforming, partial oxidation of carbon-based fuel, thermocatalytic methane decomposition (methane cracking), by thermolysis, by gasification of fossil fuels or biomass, ammonia decomposition, or any suitable combination thereof.

[0032] In an embodiment of the invention, the hydrogen may be produced by water electrolysis. In a preferred embodiment of the invention, the hydrogen may be a renewably produced hydrogen gas. In this instance, it is envisaged that water electrolysis may be solar and/or wind powered and uses proton exchange membranes, alkaline electrolysis and/or solid oxide electrolysis. It is envisaged that, in use, oxygen generated as a co-product of the water electrolysis process may be used in a fuel cell. In this instance, it is envisaged that using oxygen instead of air in a fuel cell may improve the efficiency of the fuel cell and eliminate nitrogen oxide emissions. Alternatively, the oxygen generated as a co-product of the water electrolysis process may be used in an oxygen fired gas turbine.

[0033] In an embodiment of the invention, the source of hydrogen may be a metal hydride. Any suitable metal hydride may be used, for instance, the metal hydride may be an alkali metal hydride, an alkaline earth metal hydride, a complex aluminium hydride, a borohydride, an amide-hydride system, a mixed complex hydride system or the like. In an embodiment of the invention, the source of hydrogen may be magnesium hydride. In an embodiment of the invention, the source of hydrogen may be a mixed complex hydride such as lithium amide and magnesium hydride. In an embodiment of the invention, the metal hydride may further comprise a reaction co-product. In this instance, it is envisaged that the reaction co-product may be used to improve the storage and/or reaction properties of the metal hydride, may increase the rate of hydrogen desorption, may decrease the activation energy of desorption.

[0034] In an embodiment of the invention, the source of hydrogen may be ammonia. In this instance, nitrogen may act as a carrier for the hydrogen. In an embodiment of the invention, the source of hydrogen may be methane. In this instance, carbon may act as a carrier for the hydrogen. In both of these embodiments, it is envisaged that the chemical decomposition of ammonia and methane may result in the generation of hydrogen. The chemical decomposition of ammonia and methane may be achieved using any suitable technique.

[0035] The hydrogen may be of any suitable form. Preferably, however, the hydrogen may be in a form which is easy to transport and store. For instance, the hydrogen may be a gas, a pressurised gas, a solid a liquid, a subcritical liquid, a supercritical liquid, a hydrogen-adsorbent system, a hydrogen-solvent system, a hydrogen-carrier system, or the like.

[0036] In an embodiment of the invention, the source of hydrogen may be a hydrogen carrier. Any suitable hydrogen carrier may be used. For instance, the hydrogen carrier may be ammonia, toluene, methyl cyclohexane, formic acid, methanol, methane, an aromatic carrier, an alkali metal hydride, an alkali earth metal hydride, a metal hydride, or any suitable combination thereof. Preferably, however, the hydrogen carrier may be in a form which is easy to transport and store and is readily dehydrogenated to release a source of hydrogen.

[0037] The method for reducing greenhouse gas emissions comprises the step of reacting the carbon dioxide with the hydrogen at a methanation facility to produce a synthetic methane gas. In use, it is envisaged that the carbon dioxide and/or the hydrogen may be obtained from and/or reacted at the same location or may be obtained from a site of capture and transported to a different location for reaction. For instance, the site of capture of the carbon dioxide and/or the hydrogen may be at the methanation facility. Alternatively, the carbon dioxide and/or the hydrogen may be obtained from a site of capture and transferred to the methanation facility for reaction. In use, it is envisaged that the carbon dioxide and/or the hydrogen may be transferred from a site of capture to the methanation facility via a pipeline system, or by ship, road or rail tankers, or any suitable combination thereof. The carbon dioxide and/or the hydrogen may be transferred from a site of capture to the methanation facility via a receiving terminal.

[0038] In an embodiment of the invention, the carbon dioxide and/or the hydrogen may undergo a preparation step prior to the methanation reaction step. Any suitable preparation step may be used. For instance, the carbon dioxide and/or the hydrogen may be converted from one phase to another phase, may be recovered by desorption or be stripped or separated from an adsorbent, solvent or carrier, may undergo a chemical reaction to convert a carbon dioxide carrier and/or a hydrogen carrier into a source of carbon dioxide and/or a source of hydrogen respectively, may be treated to remove impurities (such as water, hydrogen sulphides, nitrogen, carbon monoxide, and the like), or any suitable combination thereof. For instance, where the source of hydrogen may be ammonia, it is envisaged that the ammonia will be decomposed to produce the hydrogen for reaction. For instance, where the source of carbon dioxide may be a liquefied carbon dioxide, it is envisaged that the liquefied carbon dioxide may be depressurised and passed through a heat exchanger to regasify the liquefied carbon dioxide to produce the carbon dioxide for reaction in the methanation facility.

[0039] The carbon dioxide and the hydrogen may be reacted to produce a synthetic methane gas. Any suitable reaction may be used. For instance, the methanation reaction may be an artificial photosynthesis using a nanoparticle catalyst, anaerobic bacterial decomposition of vegetable matter, a Sabatier reaction, and the like. Preferably, however the methanation reaction is a Sabatier reaction. In use, it is envisaged that the heat energy released by the methanation reaction may be used to improve the efficiency of water electrolysis and hydrogen production, release hydrogen from storage in a magnesium powder storage slurry, superheat steam used in the methanation reaction, decompose ammonia to produce a source of hydrogen, regasify a liquefied source of carbon dioxide and/or a liquefied source of hydrogen, assist in improving the efficiency of a combined cycle gas turbine facility, and any suitable combination thereof.

[0040] In an embodiment of the invention, the method for reducing greenhouse gas emissions comprises the step of recovering the water by-product of the methanation reaction and transferring it to a water electrolysis facility. In this instance, it is envisaged that re-cycling water may assist in reducing the amount of fresh water used in the electrolysis process.

[0041] The method for reducing greenhouse gas emissions comprises the step of liquefying the synthetic methane gas to produce a liquefied synthetic methane. Preferably, the liquefied synthetic methane may be synthetic methane in a liquid or dense phase state. The synthetic methane gas may be liquefied at any suitable facility. For instance, the synthetic methane gas may be liquefied in a liquefaction facility located at the methanation facility, at a liquefaction facility located remotely from the methanation facility, at an existing LNG liquefaction facility, at a liquefaction facility located at a receiving terminal, or any suitable combination thereof. Preferably however, the liquefaction facility may be located conveniently to a source of synthetic methane gas.

[0042] The synthetic methane gas may undergo a preparation step prior to liquefaction. Any suitable preparation step may be used. For instance, the synthetic methane gas may be treated to remove impurities (such as water, hydrogen sulphides, nitrogen, carbon dioxide, carbon monoxide, and the like), may be blended with a source of hydrogen, a source of methane gas, a source of ethane or a higher alkane, may be chilled by a heat exchanger, may be compressed or densified, or any suitable combination thereof. In an embodiment of the invention, the synthetic methane gas may undergo one or more heat exchange processes to chill the synthetic methane gas prior to liquefaction. In use, it is envisaged that the preparation step may improve the ability to transport and/or store the synthetic methane gas prior to liquefaction, may improve the energy efficiency of the liquefaction facility, may reduce the energy required to chill a synthetic methane gas blend, or the warm energy recovered may be used to assist in the regasification of liquefied carbon dioxide.

[0043] The preparation step may be undertaken at any suitable location. For instance, the preparation step may be undertaken at a methanation facility, remotely from a methanation facility, at a liquefaction facility, remotely from a liquefaction facility, or any suitable combination thereof.

[0044] The synthetic methane gas may be liquefied using any suitable process. For instance, the synthetic methane gas may be compressed under pressure, may be condensed by cooling, or any suitable combination thereof. In an embodiment of the invention, the synthetic methane gas may be cooled by heat exchange. Any suitable heat exchanger may be used. For instance, the heat exchanger may be a shell and tube heat exchanger, a plate heat exchanger, a plate and shell heat exchanger, an adiabatic wheel heat exchanger, a plate fin heat exchanger, a pillow plate heat exchanger, a fluid heat exchanger, a waste heat recovery unit, a phase-change heat exchanger, a direct contact heat exchanger, a helical-coil heat exchanger, a spiral heat exchanger, and the like. In an embodiment of the invention, the heat exchanger may be a cold box heat exchanger.

[0045] In an embodiment of the invention, the synthetic methane gas may be cooled using a regenerative cooling cycle. For instance, the regenerative cooling cycle may be the Hampson-Linde cycle, the Siemens cycle, and the like. In an embodiment of the invention, the synthetic methane gas may be cooled using a mixed refrigerant process. Any suitable mixed refrigerant process may be used. For instance, the mixed refrigerant process may be a single mixed refrigerant process or a dual mixed refrigerant process, such as the Air Products AP-C3MRTM, AP-DMR T M , AP-XTM and AP N T M processes, the Air Liquide LIQUEFIN T M , SMARTFIN M T and TURBOFIN TM

processes. In a further embodiment of the invention, the synthetic methane gas may be cooled using a cascade process. For instance, the cascade process may be the ConocoPhillips cascade process.

[0046] In an embodiment of the invention, the synthetic methane gas may be cooled by heat exchanged against a chilled fluid. Preferably, the synthetic methane gas may be cooled by heat exchange against a liquefied captured source of carbon dioxide. In this instance, it is envisaged that the heat exchange process assists in the liquefaction of the synthetic methane gas and regasification of the liquefied captured source of carbon dioxide. The regasified captured source of carbon dioxide may be transferred to a methanation facility for reaction with a source of hydrogen.

[0047] In use, it is envisaged that the carbon dioxide emissions from a gas turbine driving a refrigeration compressor and/or a power generation unit at the liquefaction facility may be captured to provide a captured source of carbon dioxide.

[0048] The method for reducing greenhouse gas emissions comprises the step of transferring the liquefied synthetic methane to a facility comprising a gas turbine. The liquefied synthetic methane may be transferred to any suitable facility comprising a gas turbine. For instance, the facility may be a power station which generates electricity commercially, a liquefaction facility, a commercial or industrial site using gas for power generation, a commercial or industrial site using gas for manufacturing processes (such as boilers, fluid bed driers, rotary kilns, furnaces, and the like), a gas fuelling station or storage location for gas powered vessels or vehicles, and any suitable combination thereof. In a preferred embodiment of the invention, the liquefied synthetic methane may be transferred to a facility comprising a gas turbine, wherein the gas turbine may be associated with a heat recovery steam generator. Preferably, the liquefied synthetic methane may be transferred to a facility comprising a gas turbine, wherein the gas turbine may operate in an open cycle system or a combined cycle system.

[0049] The liquefied synthetic methane may be transferred to a facility comprising a gas turbine by any suitable means. For instance, the liquefied synthetic methane may be transferred to the facility comprising a gas turbine via a pipeline system, or by ship, road or rail tankers, or any suitable combination thereof. In an embodiment of the invention, the liquefied synthetic methane may be transferred from the methanation facility to the facility comprising a gas turbine via a receiving terminal. In an embodiment of the invention, the liquefied synthetic methane may be transferred from the methanation facility to the facility comprising a gas turbine and the captured carbon dioxide may be transferred from the facility comprising a gas turbine to the methanation facility using the same ship, road or rail tankers. In this instance, it is envisaged that dual utilisation of the ship, road or rail tankers may reduce costs.

[0050] The liquefied synthetic methane may undergo a preparation step prior to combustion at a facility comprising a gas turbine. Any suitable preparation step may be used. For instance, the liquefied synthetic gas may be blended with a source of hydrogen, a source of methane gas, a source of ethane or a higher alkane. Preferably, the liquefied synthetic methane may undergo regasification prior to combustion.

[0051] The method for reducing greenhouse gas emission comprises the step of regasifying the liquefied methane gas. The liquefied methane gas may be regasified at any suitable facility. For instance, the liquefied methane gas may be regasified in a regasification facility located at the facility comprising a gas turbine, at a regasification facility located remotely from the facility comprising a gas turbine, at an existing LNG regasification facility, at a regasification facility located at a receiving terminal, or any suitable combination thereof. Preferably however, the regasification facility may be located conveniently to a source of carbon dioxide.

[0052] The liquefied synthetic methane may undergo a preparation step prior to regasification. Any suitable preparation step may be used. For instance, the liquefied synthetic methane may be warmed by a heat exchanger, may be decompressed, or any suitable combination thereof. In an embodiment of the invention, the liquefied synthetic methane may undergo one or more heat exchange processes to warm the liquefied synthetic methane prior to regasification. In use, it is envisaged that the preparation step may improve the energy efficiency of the regasification plant and/or the cold energy recovered may be used to assist in the liquefaction of captured carbon dioxide.

[0053] The preparation step may be undertaken at any suitable location. For instance, the preparation step may be undertaken at a facility comprising a gas turbine, remotely from the facility comprising a gas turbine, at a regasification facility, remotely from the regasification facility, or any suitable combination thereof.

[0054] The liquefied synthetic methane may be regasified using any suitable process. For instance, the liquefied synthetic methane may be decompressed, may be heated, or any suitable combination thereof. In an embodiment of the invention, the liquefied synthetic methane may be warmed by heat exchange. Any suitable heat exchange arrangement may be used. For instance, the heat exchanger may be a shell and tube heat exchanger, a plate heat exchanger, a plate and shell heat exchanger, an adiabatic wheel heat exchanger, a plate fin heat exchanger, a pillow plate heat exchanger, a fluid heat exchanger, a waste heat recovery unit, a phase-change heat exchanger, a direct contact heat exchanger, a helical-coil heat exchanger, a spiral heat exchanger, and the like. In an embodiment of the invention, the heat exchanger may be a cold box heat exchanger.

[0055] In an embodiment of the invention, the liquefied synthetic methane may be warmed by heat exchanged against a heated fluid. Preferably, the liquefied synthetic methane may be warmed by heat exchange against a captured source of carbon dioxide. In this instance, it is envisaged that the heat exchange process assists in the regasification of the liquefied synthetic methane and liquefaction (or densifies) of the captured source of carbon dioxide. The liquefied captured source of carbon dioxide may be transferred to the methanation facility.

[0056] In an embodiment of the invention, the liquefied captured source of carbon dioxide may be compressed before being transferred to a methanation facility for reaction with a source of hydrogen.

[0057] In an embodiment of the invention, a source of hydrogen may be blended with the synthetic methane gas prior to combustion. In a further embodiment of the invention, methane gas derived from traditional fossil sources may be blended with the synthetic methane gas prior to combustion. In a yet further embodiment of the invention, ethane or a higher alkane may be blended with the synthetic methane gas prior to combustion.

[0058] The method for reducing greenhouse gas emissions comprises the step of combusting the synthetic methane gas in a gas turbine. The synthetic methane gas may be combusted for any suitable power generation purpose. For instance, the synthetic methane gas may be combusted for commercial electricity generation, for powering a commercial or industrial site, for manufacturing processes, for powering vessels or vehicles, for mechanically driven refrigeration compressors involved in the liquefaction of methane, and the like. In an embodiment of the invention, the synthetic methane gas may be combusted at a facility for commercial electricity generation. For instance, the synthetic methane gas may be combusted at a gas-fired power plant, such as an open cycle gas turbine plant, a closed cycle gas turbine plant, a combined cycle gas turbine plant, a reciprocating engine, or the like. In this instance, it is envisaged that combusting the synthetic methane gas in a combined cycle gas turbine plant may reduce greenhouse gas emissions. In an embodiment of the invention, the synthetic methane gas may be combusted at a liquefaction facility to provide power to drive a refrigeration compressor.

[0059] The method for reducing greenhouse gas emissions comprises the step of capturing carbon dioxide produced by the combustion of the synthetic methane gas to provide a captured source of carbon dioxide. The carbon dioxide may be captured by any suitable means. For instance, the carbon dioxide may be captured by adsorption, absorption, cryogenic separation, membrane separation, or any suitable combination thereof. Any suitable conventional post-combustion carbon capture and sequestration apparatus may be used, and no specific discussion of this is necessary.

[0060] In an embodiment of the invention, the method for reducing greenhouse gas emissions comprises the step of capturing nitrogen oxides produced by the reaction of nitrogen and oxygen during the combustion reaction. However, it will be understood that the amount of nitrogen oxides produced during combustion will vary depending on a number of factors, such as the type of material being combusted, the temperature of combustion, and whether air is injected during combustion. The nitrogen oxides may be captured by any suitable means. For instance, the nitrogen oxides may be captured by adsorption, absorption, selective catalytic reduction using ammonia injection, catalytic oxidation and adsorption, scrubbing solutions, or any suitable combination thereof. Any suitable conventional post-combustion nitrogen oxide capture and sequestration apparatus may be used, and no specific discussion of this is necessary.

[0061] In an embodiment of the invention, the captured source of carbon dioxide may undergo a preparation step prior to transfer to a methanation facility. Any suitable preparation step may be used. For instance, the carbon dioxide may be recovered by desorption or be stripped or separated from an adsorbent, solvent or carrier, may undergo a chemical reaction to convert a carbon dioxide carrier into a source of carbon dioxide, may be treated to remove impurities (such as water, hydrogen sulphides, nitrogen, carbon monoxide, and the like), may be converted from one phase to another phase, or any suitable combination thereof. However, it will be understood that the type of preparation step required will vary depending on a number of factors, such as the type of fuel being combusted and the method of capturing the carbon dioxide.

[0062] In a preferred embodiment of the invention, the captured source of carbon dioxide may be liquefied before being transferred to the methanation facility. Preferably, the liquefied captured carbon dioxide may be in dense phase before being transferred to the methanation facility.

[0063] The liquefied captured carbon dioxide may be transferred from the facility comprising a gas turbine to the methanation facility by any suitable means. For instance, the liquefied captured source of carbon dioxide may be transferred to the methanation facility via a pipeline system, or by ship, road or rail tankers, or any suitable combination thereof. In an embodiment of the invention, the liquefied captured carbon dioxide may be transferred from the facility comprising a gas turbine to the methanation facility via a receiving terminal.

[0064] In an embodiment of the invention, the liquefied captured source of carbon dioxide may be transferred from the facility comprising a gas turbine to the methanation facility and produced ammonia may be transferred from an ammonia synthesis facility to the facility comprising a gas turbine using the same ship, road or rail tankers. In this instance, it is envisaged that dual utilisation of the same ship, road or rail tankers may reduce costs.

[0065] In an embodiment of the invention, the method for reducing greenhouse gas emissions comprises the step of transferring the liquefied synthetic methane to a hydrogen production facility. The liquefied synthetic methane may be transferred to any suitable hydrogen production facility. For instance, the hydrogen production facility may be a steam methane reformation facility, a thermocatalytic methane decomposition facility, or any suitable combination thereof.

[0066] The liquefied synthetic methane may be transferred from the methanation facility to a hydrogen production facility by any suitable means. For instance, the liquefied synthetic methane may be transferred to the hydrogen production facility via a pipeline system, or by ship, road or rail tankers, or any suitable combination thereof. In an embodiment of the invention, the liquefied synthetic methane may be transferred from the methanation facility to the hydrogen production facility via a receiving terminal. In an embodiment of the invention, the liquefied synthetic methane may be transferred from the methanation facility to the hydrogen production facility and a captured source of carbon dioxide may be transferred from the hydrogen production facility to the methanation facility using the same ship, road or rail tankers. In an embodiment of the invention, the liquefied synthetic methane may be transferred from the methanation facility to the hydrogen production facility and a source of hydrogen may be transferred from the hydrogen production facility to the methanation facility using the same ship, road or rail tankers. In this instance, it is envisaged that dual utilisation of the same ship, road or rail tankers may reduce costs.

[0067] The liquefied synthetic methane may undergo a preparation step prior to conversion to hydrogen. Any suitable preparation step may be used. Preferably, the liquefied synthetic methane may undergo regasification prior to combustion.

[0068] The liquefied methane gas may be regasified at any suitable facility. For instance, the liquefied methane gas may be regasified in a regasification facility located at the hydrogen production facility, at a regasification facility located remotely from the hydrogen production facility, at an existing LNG regasification facility, at a regasification facility located at a receiving terminal, or any suitable combination thereof. Preferably however, the regasification facility may be located conveniently to a source of carbon dioxide.

[0069] The liquefied synthetic methane may undergo a preparation step prior to regasification. Any suitable preparation step may be used. For instance, the liquefied synthetic methane may be warmed by a heat exchanger, may be decompressed, or any suitable combination thereof. In an embodiment of the invention, the liquefied synthetic methane may undergo one or more heat exchange processes to warm the liquefied synthetic methane prior to regasification. In use, it is envisaged that the preparation step may improve the energy efficiency of the regasification plant and/or the cold energy recovered may be used to assist in the liquefaction of captured carbon dioxide.

[0070] The preparation step may be undertaken at any suitable location. For instance, the preparation step may be undertaken at a facility comprising a gas turbine, remotely from the facility comprising a gas turbine, at a regasification facility, remotely from the regasification facility, or any suitable combination thereof.

[0071] The liquefied synthetic methane may be regasified using any suitable process. For instance, the liquefied synthetic methane may be decompressed, may be heated, or any suitable combination thereof. In an embodiment of the invention, the liquefied synthetic methane may be warmed by heat exchange. Any suitable heat exchange arrangement may be used. For instance, the heat exchanger may be a shell and tube heat exchanger, a plate heat exchanger, a plate and shell heat exchanger, an adiabatic wheel heat exchanger, a plate fin heat exchanger, a pillow plate heat exchanger, a fluid heat exchanger, a waste heat recovery unit, a phase-change heat exchanger, a direct contact heat exchanger, a helical-coil heat exchanger, a spiral heat exchanger, and the like. In an embodiment of the invention, the heat exchanger may be a cold box heat exchanger.

[0072] In an embodiment of the invention, the liquefied synthetic methane may be warmed by heat exchanged against a heated fluid. Alternatively, where the hydrogen production facility produces hydrogen using steam reformation and water gas shift reactions, the liquefied synthetic methane may be warmed by heat exchange against a captured source of carbon dioxide. In this instance, it is envisaged that the heat exchange process assists in the regasification of the liquefied synthetic methane and liquefaction of (or densifies) the captured source of carbon dioxide. The liquefied captured source of carbon dioxide may be transferred to the methanation facility or to a liquefaction facility which services the methanation facility.

[0073] The synthetic methane gas may be converted to hydrogen and transferred from the hydrogen production facility to a facility comprising a gas turbine.

[0074] Any suitable method of converting the synthetic methane gas to hydrogen may be used. For instance, the synthetic methane gas may undergo steam reforming, a combination of steam reforming and water gas shift, partial oxidation, a combination of partial oxidation and water gas shift, a thermocatalyic decomposition reaction (such as the Hazer process), or any suitable combination thereof.

[0075] In an embodiment of the invention, the heat required for the conversion of synthetic methane gas to hydrogen may be provided by the conversion of hydrogen to ammonia (carrier for hydrogen), and any suitable combination thereof. Alternatively, the synthetic methane gas may undergo steam reforming using an electrically heated catalytic reactor.

[0076] In an embodiment of the invention, the heat required for the conversion of synthetic methane gas to hydrogen may be provided by combustion of a carbon-based fuel. In this instance, it is envisaged that the carbon dioxide produced by power generation may be captured to provide a captured source of carbon dioxide. The carbon dioxide may be captured by any suitable means. For instance, the carbon dioxide may be captured by adsorption, absorption, cryogenic separation, membrane separation, or any suitable combination thereof. Any suitable conventional carbon capture and sequestration apparatus may be used, and no specific discussion of this is necessary.

[0077] The captured carbon dioxide may be transferred from the hydrogen production facility to the methanation facility. However, it will be understood that whether the hydrogen production facility generates carbon dioxide as a by-product of the reaction will depends on the type of reaction used to convert synthetic methane gas to hydrogen. For instance, steam reforming and partial oxidation reactions followed by a water gas shift reaction may generate carbon dioxide as a by-product of the reaction. The carbon dioxide may be captured by adsorption, absorption, cryogenic separation, membrane separation, or any suitable combination thereof.

[0078] The hydrogen from the hydrogen production facility may be transferred to a facility comprising a gas turbine by any suitable means. For instance, the hydrogen may be transferred to the facility via a pipeline system, or by ship, road or rail tankers, or any suitable combination thereof.

[0079] The hydrogen may undergo a preparation step prior to transfer to a facility comprising a gas turbine. Any suitable preparation step may be used. For instance, the hydrogen may be recovered by desorption or be stripped or separated from an adsorbent, solvent or carrier, may be treated to remove impurities (such as carbon dioxide, carbon monoxide, nitrogen, and the like, may be converted from one phase to another phase, or any suitable combination thereof. However, it will be understood that the type of preparation step required will vary depending on a number of factors, such as the type of reaction being undertaken and the method of capturing the hydrogen. In an embodiment of the invention, the hydrogen may be liquefied or densified prior to transfer to a facility comprising a gas turbine. In a preferred embodiment of the invention, the hydrogen may be converted into ammonia and transferred to a facility comprising a gas turbine.

[0080] The hydrogen may be converted into ammonia using any suitable process. For instance, ammonia may be synthesised using a Haber-Bosch process, a reverse fuel cell, a membrane reactor, and the like. Preferably, however, the ammonia synthesis reaction is a Haber-Bosch process. In use, it is envisaged that converting the hydrogen into ammonia instead of liquefying the hydrogen may reduce energy requirements and make it easier to transport and store the hydrogen.

[0081] The hydrogen may be combusted for any suitable purpose. For instance, the hydrogen may be combusted for commercial electricity generation, for powering a commercial or industrial site, for manufacturing processes, for powering vessels or vehicles, and the like. Alternatively, the hydrogen may be combined with one or more gases prior to combustion in the facility comprising a gas turbine.

[0082] The present invention provides numerous advantages over the prior art. For instance, the present invention provides a method of reducing or eliminating most of the carbon dioxide emissions associated with liquefied natural gas and/or liquefied synthetic methane into the atmosphere by capturing and recycling the carbon dioxide. In addition, the method creates a circular economy for carbon dioxide and monetises carbon dioxide so that eventual sequestration becomes a non-material overhead. The present invention provides a method of improved energy conservation by using heat exchangers to capture and exchange energy between regasification and liquefaction steps. In addition, in the case of facilities which are modified or converted with the invention steps mentioned, existing infrastructure can be utilised. This offers significant cost advantages in that the infrastructure does not need to be written down financially and has the opportunity to have a productive life extension. The present invention also enables the liquefied natural gas industry to utilise renewable wind and solar power to deliver cleaner green energy.

[0083] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0084] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS

[0085] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

[0086] Figure 1 illustrates a representation of a method of reducing greenhouse gases according to an embodiment of the invention.

DESCRIPTION OF EMBODIMENTS

[0087] In Figure 1, a representation of a method of reducing greenhouse gases according to an embodiment of the invention is illustrated. Carbon dioxide and hydrogen may be obtained from respective sources thereof and reacted with hydrogen at methanation facility 12 to produce a synthetic methane gas. In use, it is envisaged that the source of hydrogen may be renewably produced by electrolysis at a water electrolysis facility 10. In use, it is envisaged that carbon dioxide may be derived from multiple sources and transported to a methanation facility 12 for storage and conversion to synthetic methane gas.

[0088] Synthetic methane gas may be liquefied at a liquefaction facility 14 to produce a liquefied synthetic methane. In use, it is envisaged that the synthetic methane gas may be cooled by heat exchange against a liquefied captured source of carbon dioxide prior to the synthetic methane gas entering the liquefaction facility. In this instance, it is envisaged that the heat exchange process assists in the liquefaction of (densifies) the synthetic methane gas and regasification of the liquefied captured source of carbon dioxide.

[0089] Liquefied synthetic methane may be transferred by a gas carrier 16 to a regasification facility 18. In use, it is envisaged that the liquefied synthetic methane may be warmed by heat exchange against a captured source of carbon dioxide. In this instance, it is envisaged that the heat exchange process assists in the regasification of the liquefied synthetic methane and liquefaction of (densifies) the captured source of carbon dioxide.

[0090] The synthetic methane gas may be combusted for power generation at facility comprising a gas turbine 20. Carbon dioxide produced by the combustion of synthetic methane gas may be captured and transferred to methanation facility 12. In use, it is envisaged that the captured carbon dioxide may be liquefied and transferred by gas carrier 16 to methanation facility 12.

[0091] Alternatively, the synthetic methane gas may be converted to hydrogen at a hydrogen production facility 22 using a suitable process. The hydrogen from hydrogen production facility 22 may be transferred to a facility comprising a gas turbine (not shown) for combustion. In use, it is envisaged that the hydrogen may be liquefied or converted to ammonia and transferred by a gas carrier to a facility comprising a gas turbine for combustion. Where hydrogen is produced by steam methane reformation, carbon dioxide produced as a by-product of the process may be captured and transferred to methanation facility 12. In use, it is envisaged that the captured carbon dioxide may be liquefied and transferred by a gas carrier 16 to methanation facility 12.

[0092] In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0093] Reference throughout this specification to 'one embodiment' or'an embodiment' means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases 'in one embodiment' or'in an embodiment' in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0094] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims

1. A method for reducing greenhouse gas emissions, the method comprising the steps of:

c. Transferring the liquefied synthetic methane to a facility comprising a gas turbine;

d. Regasifying the liquefied synthetic methane;

e. Combusting the synthetic methane gas in the gas turbine;

f. Capturing carbon dioxide produced by the combustion of the synthetic methane gas to provide captured carbon dioxide;

g. Liquefying the captured carbon dioxide to produce a liquefied captured carbon dioxide; and

h. Transferring the liquefied captured carbon dioxide to the methanation facility.

2. A method for reducing greenhouse gas emissions, the method comprising the steps:

a. Obtaining a source of carbon dioxide and a source of hydrogen;

e. Regasifying the liquefied synthetic methane using a heat exchanger associated with the facility comprising the gas turbine; f. Combusting the synthetic methane gas in the gas turbine; g. Capturing carbon dioxide produced by the combustion of the synthetic methane gas to provide a captured source of carbon dioxide; and i. Transferring the captured source of carbon dioxide from the facility comprising the gas turbine to the methanation facility.

3. A method for reducing greenhouse gas emissions according to claim 1 or claim 2, wherein the carbon dioxide and/or the source of carbon dioxide is one or more of carbon dioxide captured from pre-combustion processes, post-combustion processes, liquefaction facilities, oxy-fuel combustion, direct air capture, emissions of the cement industry, or pre-processing of crude natural gas.

4. A method for reducing greenhouse gas emissions according to claim 1 or claim 2, wherein the hydrogen and/or the source of hydrogen is one or more of hydrogen gas produced by electrolysis of water, steam reforming, partial oxidation of carbon-based fuel, thermocatalytic methane decomposition, thermolysis, gasification of fossil fuels or biomass, or ammonia decomposition.

5. A method for reducing greenhouse gas emissions according to claim 4, wherein the hydrogen and/or the source of hydrogen is hydrogen gas produced by electrolysis of water and/or ammonia decomposition.

6. A method for reducing greenhouse gas emissions according to any one of claims 1 to 5, wherein the synthetic methane gas and/or the captured carbon dioxide may undergo a preparation step prior to liquefaction.

7. A method for reducing greenhouse gas emissions according to claim 6, wherein the preparation step comprises one or more heat exchange processes to chill the synthetic methane gas and/or the captured carbon dioxide prior to liquefaction.

8. A method for reducing greenhouse gas emissions according to any one of claims 1 to 7, wherein the synthetic methane gas and/or the captured carbon dioxide may be cooled by heat exchanged against a chilled fluid.

9. A method for reducing greenhouse gas emissions according to claim 8, wherein the synthetic methane gas may be cooled by heat exchanged against a liquefied captured source of carbon dioxide and/or the captured carbon dioxide may be cooled by heat exchanged against a liquefied synthetic methane.

10. A method for reducing greenhouse gas emissions according to any one of claims 1 to 9, wherein the gas turbine is associated with a heat recovery steam generator.