Method of transporting carbon dioxide and / or hydrogen using methanation and subsequent re-separation

Abstract

Processes for transporting hydrogen and / or carbon dioxide are described. A process comprises the methanation of hydrogen and carbon dioxide to produce a methanation product comprising methane, transport of the methanation product to a second location, and conversion of the methanation product at the second location to produce hydrogen and carbon dioxide.

Description

METHOD OF TRANSPORTING CARBON DIOXIDE AND / OR HYDROGEN USING METHANATION AND SUBSEQUENT RE-SEPARATIONFIELD

[0001] The present disclosure generally relates to a process for transporting carbon dioxide and / or hydrogen from a first location to a second location. In particular, the process comprises transforming the carbon dioxide and / or hydrogen at a first location into a stream comprising methane, transporting the stream to a second location, and separating the stream comprising methane into carbon dioxide and / or hydrogen at the second location.BACKGROUND

[0002] Hydrogen is expected to play a significant role in the global energy transition and goals of reducing CO2 emissions following the 2015 Paris agreement. Hydrogen will play a major role, in particular, in the power, industry and transportation markets. Hydrogen emits only water during its combustion. Therefore, it is being considered as an alternative to more traditional fuels such as natural gas (which emits CO2 when combusted). Further, hydrogen may be produced in a number of "green," decarbonized, or low-emission processes. For example, hydrogen may be produced by water electrolysis powered by renewable power. When hydrogen is produced in such a manner, it becomes a "carbon free" energy carrier which can be used in gas turbines to produce "carbon free" electricity.

[0003] As of 2020, nearly 80% of the hydrogen produced in the US originated from natural gas reforming. Natural gas reforming is a process in which natural gas catalytically reacts with steam to produce a synthesis gas or "syngas," comprising a mixture of H2, CO, CO2, and CH4. Another process, partial oxidation (POx), is a process in which natural gas is oxidized by oxygen to produce a synthesis gas or "syngas," comprising a mixture of H2, CO, CO2, and CH4. In either case, hydrogen is then extracted from the syngas through a series of conversion and purification steps. Therefore, hydrogen may be generated by steam methane reforming (SMR), autothermal reforming (ATR), or a partial oxidation (POx) reaction, which typically takes place at elevated temperatures with external heat provided by the combustion of hydrocarbons.

[0004] The conversion of natural gas and steam into syngas in an SMR, ATR, orPOx process produces carbon dioxide. In an SMR reaction, the conversion of natural gas and steam into syngas accounts for approximately 60% of the total CO2 emissions of the reformingoperation. The other 40% of emissions originate from the combustion of hydrocarbons to produce heat necessary for the reforming reaction to happen. Many avenues have been explored for the reduction of overall emissions of SMR, ATR, or partial oxidation processes. For example, recycle and combustion of off gases to produce the heat needed for the reaction or recovery of the heat generated when combusting the eventual hydrogen product. However, these improvements only displace some of the emissions.

[0005] For the hydrogen produced in a natural gas reforming operation (e.g., SMR, ATR, or partial oxidation) to be considered low-emission, decarbonized, or "clean," it is essential that CO2 emissions be captured, sequestered or otherwise used.

[0006] Various CO2 capture technologies are available to capture the reforming process emissions and emissions from associated combustion of natural gas. However, a problem persists when the location at which the CO2 emissions are generated and captured is not a suitable location for sequestration or other uses of the emissions. For example, the location at which the CO2 emissions are generated may lack the necessary geological reservoirs, readily available or cost efficient land, or the infrastructure for sequestration. Thus, it may be necessary to transport the CO2 that is captured to a second location. The logistics of this transportation, particularly when a long transportation distance is required to reach the closest potential geological CO2 reservoir, have presented many challenges. For example, the transportation typically involved the construction of dedicated pipelines, liquification of the carbon dioxide gas, and / or transport of the carbon dioxide via railroad lines.

[0007] Accordingly, there remains a need in the art to develop processes wherein CO2 and / or CO are captured and efficiently transported over long distances and sequestered at a second location.

[0008] Water electrolysis powered by renewable energy is one of the most sought after pathways to produced low-carbon hydrogen. This pathway is sometimes called "green hydrogen." The ability to produce green hydrogen is directly linked to the availability of abundant renewable power. The deployment of green hydrogen technologies currently faces several hurdles. Regions rich in renewable power are often distant from the consumption centers of the green hydrogen. Therefore, current systems either require large power transmission systems to bring the power to the consumption centers or large hydrogen distribution systems, such as gaseous hydrogen pipelines or a liquid hydrogen supply chain. These issues are further exacerbated when renewable power areas are far inland, and require increasingly complex export supply chains. Gaseous hydrogen pipelines, although well proven,require large compression power because of the specificities of the hydrogen molecule. Liquid hydrogen is costly to transport, because it requires power intensive and complex liquefaction systems to maintain temperatures below -250°C, as well as special features for transportation to maintain hydrogen in a liquid state and minimize evaporation.

[0009] Therefore, there remains a need in the art to develop new and improved processes where the green hydrogen can be transported efficiently to consumption areas. In particular, there remains a need in the art to develop new and improved processes wherein the CO2 and / or CO gases can be captured and transported to a second location as described above, and simultaneously hydrogen (e.g., green hydrogen) can be transported to the second location.BRIEF SUMMARY

[0010] One aspect of the present invention is directed to a process for transporting gas. The process comprises providing hydrogen gas and an inlet stream comprising carbon dioxide to a methanation unit; methanating the hydrogen gas and the inlet stream in a first location to produce a methanation product stream comprising methane; transporting the methanation product stream to a second location; and converting the methanation product stream at the second location to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide.

[0011] Another aspect of the invention is directed towards a process where the hydrogen gas to the methanation reaction utilizes hydrogen that is partially or entirely green hydrogen.

[0012] Another aspect of the present invention is directed to a process for transporting gas comprising a steam methane reforming process. The steam methane reforming process comprises providing a source gas comprising natural gas into a steam methane reformer to produce a flue gas from which a first carbon-dioxide containing stream is separated and a reformer product stream; subjecting the reformer product stream to a water-gas shift reaction to produce a water-gas shift product stream, the water-gas shift reaction comprising reacting carbon monoxide from the reformer product stream with water to produce carbon dioxide and hydrogen; removing carbon dioxide from the water-gas shift product stream to produce a CO2- depleted hydrogen stream and a second carbon dioxide-containing stream; and optionally subjecting the C Ch-depleted hydrogen stream to a pressure-swing adsorption process (PSA) to adsorb at least a portion of the undesirable components and produce a hydrogen rich product stream and a depleted hydrogen product stream. After the steam methane reforming process,an external source of hydrogen gas (i.e. not the hydrogen rich product stream) and an inlet stream comprising one or more of the first carbon dioxide-containing stream, the second carbon dioxide-containing stream, or a combination thereof is provided to a methanation unit. The hydrogen gas and the inlet stream are methanated in a first location to produce a methanation product stream comprising methane. The methanation product stream is transported to a second location. Finally, the methanation product stream is converted at a second location to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide.

[0013] Another aspect of the invention is directed to a process for transporting gas comprising a steam methane reforming process that comprises a cryogenic separation step. The steam methane reforming process comprises providing a source gas comprising natural gas into a steam methane reformer to produce a flue gas from which a first carbon-dioxide containing stream is separated and a reformer product stream; capturing carbon dioxide from the reformer product stream to produce a second carbon dioxide-containing stream and a CCh-depleted reformer product stream; introducing the CCh-depleted reformer product stream into a cryogenic separation process to produce a carbon monoxide-containing stream and a CO- depleted reformer product stream; and optionally subjecting the CO-depleted reformer product stream to a pressure-swing adsorption process to adsorb at least a portion of the undesirable components and produce a hydrogen rich product stream and a depleted hydrogen product stream. After the steam methane reforming process, an external source of hydrogen gas (i.e. not the hydrogen rich product stream) and an inlet stream comprising one or more of the first carbon dioxide-containing stream, the second carbon dioxide-containing stream, the carbon monoxide-containing stream or a combination thereof is provided to a methanation unit. The hydrogen gas and the inlet stream are methanated in a first location to produce a methanation product stream comprising methane. The methanation product stream is transported to a second location. Finally, the methanation product stream is converted at a second location to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide.

[0014] Another aspect of the present invention is directed to a process for transporting gas comprising an autothermal reforming process. The autothermal reforming process comprises contacting a source gas comprising natural gas, a source of steam, and a source of oxygen in an autothermal reformer to produce a reformer product stream; subjecting the reformer product stream to a water-gas shift reaction to produce a water-gas shift product stream, the water-gas shift reaction comprising reacting the carbon monoxide from the reformerproduct stream with water to produce carbon dioxide and hydrogen; removing carbon dioxide from the water-gas shift product stream to produce a C Ch-depleted stream and a second carbon dioxide-containing stream; and optionally subjecting the CCh-depleted stream to a pressureswing adsorption process to adsorb at least a portion of the undesirable components and produce a hydrogen depleted product stream and a hydrogen rich product stream. The autothermal reforming process optionally comprises heating the source gas comprising natural gas in a pre-heater through external combustion of hydrocarbon which produces a flue gas from which a first carbon-dioxide containing stream is separated. After the autothermal reforming process, an external source of hydrogen gas (i.e. not the hydrogen rich product stream) and an inlet stream comprising one or more of the first carbon dioxide-containing stream, the second carbon dioxide-containing stream, or a combination thereof is provided to a methanation unit. The hydrogen gas and the inlet stream are methanated in a first location to produce a methanation product stream comprising methane. The methanation product stream is transported to a second location. Finally, the methanation product stream is converted at a second location to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide.

[0015] A still further aspect of the present invention is directed to a process for transporting gas comprising an autothermal reforming process comprising cryogenic separation. The autothermal reforming process comprises contacting a source gas comprising natural gas, a source of steam, and a source of oxygen in an autothermal reformer to produce a reformer product stream; capturing carbon dioxide from the reformer product stream to produce a second carbon dioxide-containing stream and a CCh-depleted reformer product stream; introducing the CCh-depleted reformer product stream into a cryogenic separation process to produce a carbon monoxide-containing stream and a CO-depleted reformer product stream; and optionally subjecting the CO-depleted reformer stream to a pressure-swing adsorption process to adsorb at least a portion of the undesirable components and produce a hydrogen depleted product stream and a hydrogen rich product stream. The autothermal reforming process optionally comprises heating the source gas comprising natural gas in a preheater through external combustion of hydrocarbon which produces a flue gas from which a first carbon-dioxide containing stream is separated. After the autothermal reforming process, an external source of hydrogen gas (i.e. not the hydrogen rich product stream) and an inlet stream comprising one or more of the first carbon dioxide-containing stream, the second carbon dioxide-containing stream, the carbon monoxide-containing stream or a combination thereof is provided to a methanation unit. The hydrogen gas and the inlet stream are methanated in a firstlocation to produce a methanation product stream comprising methane. The methanation product stream is transported to a second location. Finally, the methanation product stream is converted at a second location to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide.

[0016] Other objects and features will be in part apparent and in part pointed out hereinafter.BRIEF DESCRIPTION OF THE FIGURES

[0017] Figure 1 illustrates a flow diagram of a process of the present disclosure wherein carbon dioxide and hydrogen are transported from a first location to a second location.

[0018] Figure 2 illustrates a flow diagram of the process of Figure 1, wherein the carbon dioxide is generated in a natural gas reforming process.

[0019] Figure 3 illustrates a flow diagram of a steam methane reforming (SMR) process for producing hydrogen comprising a catalytic reforming reaction, water-gas shift reaction, CO2 capture, and pressure-swing adsorption (PSA) process.

[0020] Figure 4 illustrates a traditional flow diagram of an autothermal reforming (ATR) process for producing hydrogen from natural gas comprising pre-heating, pretreatment, auto-thermal reforming, steam generation, a water-gas shift reaction, CO2 capture, and PSA.

[0021] Figure 5 illustrates a flow diagram of a process of the present disclosure wherein steam methane reforming, water electrolysis, and methanation occur at a first location and hydrogen generation and carbon dioxide sequestration occur at a second location.

[0022] Figure 6 illustrates a flow diagram of a process of the present disclosure wherein steam methane reforming, water electrolysis, and methanation occur at a first location and hydrogen generation and carbon dioxide sequestration occur at a second location, wherein the steam methane reforming process comprises cryogenic separation.

[0023] Figure 7 illustrates a flow diagram of a process of the present disclosure wherein autothermal reforming, water electrolysis, and methanation occur at a first location and hydrogen generation and carbon dioxide sequestration occur at a second location.

[0024] Figure 8 illustrates a flow diagram of a process of the present disclosure wherein autothermal reforming, water electrolysis, and methanation occur at a first location and hydrogen generation and carbon dioxide sequestration occur at a second location, wherein the autothermal reforming process comprises cryogenic separation.

[0025] Corresponding reference characters indicate corresponding parts throughout the drawings.DETAILED DESCRIPTION

[0026] The inventors of the present invention have discovered an improved process for transportation of carbon dioxide and / or hydrogen that is efficient, cost effective, and presents far less risk than previously used methods of transportation.

[0027] In the present invention, at a first location, hydrogen gas and captured carbon dioxide are combined in a methanation unit to prepare a methanation product stream comprising methane. The methanation product is then transported to a second location (e.g., via conventional methane pipelines). At the second location, the methanation product is converted to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide. For example, the methanation product may be converted (e.g., reformed) by SMR, ATR, or partial oxidation. The second product stream comprising carbon dioxide may then be sequestered or otherwise used at the second location. A flow diagram of this process is shown in Figure 1.

[0028] Figure 2 illustrates a flow diagram of the process of Figure 1 wherein the carbon dioxide originates from a natural gas reforming process. The off-gases comprising carbon dioxide or carbon dioxide and carbon monoxide are recovered from the reforming process and directed to the methanation step as an inlet stream. An external source of hydrogen gas (i.e. not the hydrogen product of the reforming process) is combined with the inlet stream in the methanation process. The process then progresses as set forth in Figure 1.

[0029] In certain embodiments, the external source of hydrogen gas used in the methanation process may be produced by a low or no-emission process (e.g., a water electrolysis process). In further embodiments, the hydrogen gas used in the methanation process may be produced by a process comprising renewable energy (e.g., solar energy, wind energy, geothermal energy, hydroelectric energy, tidal energy, or nuclear energy). In either of these embodiments, "green" hydrogen is produced at a first location, transported to a secondlocation as a methanation product stream, and then recovered as a distinct hydrogen gas stream after the methanation product stream is converted. In this way, it is possible to not only safely transport CO2 and / or CO to a location more suitable for sequestration, but it is possible to easily transport "green" hydrogen between locations at the same time.

[0030] When the CO2 emissions originate from a SMR, ATR, or partial oxidation processes, the configuration of the present disclosure provides a significant advantage over the prior known processes. The present disclosure provides a process for decarbonizing the hydrogen produced from natural gas reforming operation, in a location where hydrogen is needed and sequestration of CO2 and / or CO is not feasible, and simultaneously transporting both the recovered CO2 and / or CO and an additional (e.g., green) source of hydrogen produced at a first location (in excess of what the SMR produces) over long distances.CO2 and / or CO Gas Generation

[0031] Although discussion herein is directed to the capture of CO2 and / or CO at a first location, transport to a second location, and sequestration of CO2 and / or CO at a second location, wherein the CO2 and / or CO originate from SMR, ATR, or partial oxidation processes, it will be understood that the described processes for transport and sequestration are equally applicable to the transport of CO2 and / or CO gas emissions originating from other sources. Additionally, although discussion herein is primarily directed to CO2, the process is equally applicable to the treatment and processing of other gasses such as CO.Steam Methane Reforming (SMR)

[0032] A steam methane reforming (SMR) process generally comprises feeding a source gas comprising a hydrocarbon (e.g., natural gas) to a reformer and catalytically converting the source gas in the presence of steam to form a reformer product stream, or "syngas" (e.g., comprising a mixture of H2, CO, CO2, and CH4), and a flue gas.

[0033] For example, in one embodiment, a SMR process comprises combusting a fuel gas (e.g. natural gas) to produce a heated gas, and introducing heated gas and a source gas comprising natural gas into a steam methane reformer to produce a reformer product stream (syngas) and a flue gas from which carbon dioxide is separated (i.e. first carbon dioxidecontaining stream). The reformer product stream is typically hydrogen rich. In certain embodiments, the reformer product stream is subjected to a water-gas shift reaction to produce a water-gas shift product stream; the water-gas shift reaction comprising reacting the carbon monoxide from the reformer product stream with water in a catalytic reactor to produce carbondioxide and hydrogen. Carbon dioxide is then removed from the water-gas shift product stream to produce a C Ch-depleted hydrogen stream and a second carbon dioxide-containing stream. Finally, the CCh-depleted hydrogen stream may be optionally subjected to a pressure-swing adsorption (PSA) process to further purify the stream (e.g., adsorb at least a portion of the undesirable components) and produce a relatively pure hydrogen product stream (i.e. >99.99% hydrogen) and a PSA tail gas. In previous configurations, this PSA tail gas would typically be recycled to the reformer for further combustion. However, in certain embodiments of the present disclosure, the PSA tail gas may be further processed and / or used to form at least a portion of the inlet gas to the methanation unit, as described in further detail below.

[0034] A flow diagram of an exemplary SMR process comprising a catalytic reforming reaction, water-gas shift reaction, CO2 capture, and PSA process is shown in Figure 3. In this configuration, the first carbon dioxide-containing stream separated from the flue gas and / or CO2 from the CO2 capture step (i.e. second carbon dioxide-containing stream) may be used to form at least a portion of the inlet stream to the methanation unit.

[0035] The catalytic reaction of the feed stream in the reformer requires high temperatures. In some embodiments, this heat is primarily achieved by combustion of the hydrocarbon in the reformer. In other embodiments, heat may be provided by the heated gas from combustion of a burner that is fed with air, natural gas, and / or outlet gasses of downstream unit operations (e.g., the PSA tail gas from the optional pressure-swing adsorption step). The CO2 emissions from this optional combustion may be captured and directed to the methanation unit as a portion of the inlet stream as described herein, used in the reforming process, or used in other applications such as mechanical drive.

[0036] The hot syngas (i.e. reformer product stream) resulting from the reformer is optionally cooled in a series of exchanger and boiler(s) to produce steam. The steam may be optionally used as a source of heat for other unit operations on-site or for other applications (e.g. steam turbines drives or generator). The steam may be optionally recycled to the inlet of the SMR or used elsewhere in the process as a source of heat. The steam produced from the cooled syngas may also or alternatively be used for other purposes in the plant (e.g. steam turbine drivers for compressors, steam turbine generators, etc.).

[0037] The cooled syngas (i.e. reformer product stream) is then directed to one or more water-gas shift reactor(s) to form a water-gas shift product stream. In the shift reactor, steam is added to the cooled syngas to convert CO into CO2 and H2 and produce a water-gasshift product stream. The water-gas shift reaction may comprise contacting the reformer product stream with a catalyst. The catalyst may comprise, for example, a base metal.

[0038] After the water-gas shift reaction, the water-gas shift product stream may be subjected to one or more CO2 capture steps to produce a C Ch-depleted hydrogen stream and a second carbon dioxide-containing stream. For example, CO2 may be separated from the water-gas shift product stream by a process comprising absorption, adsorption, membrane separation, cryogenic separation, cryogenic distillation, or combinations thereof. For example, the water-gas shift product stream may be directed to an absorption unit operation to remove at least a portion of the CO2 present in the stream.

[0039] In certain embodiments, a final purification step may be conducted to remove impurities and reach the desired concentration of hydrogen in the hydrogen product stream. For example, this optional purification step may comprise a pressure-swing adsorption (PSA) process. The optional PSA process comprises adsorbing residual carbon dioxide, carbon monoxide, methane, and other impurities using an adsorbent material at high pressures. The adsorbent material of the PSA process may comprise, for example, one or more zeolite. A PSA process may produce a relatively pure hydrogen product stream comprising >99.99% hydrogen. The resulting exit gas of this final purification step is a highly purified hydrogen gas (i.e. a hydrogen product stream). The components adsorbed in the PSA process may be selected from the group consisting of carbon monoxide, carbon dioxide, methane or water, and combinations thereof. The adsorbed components may then be desorbed from the adsorbent material, in the form of a PSA tail gas, and sent to burners on-site as a source of fuel.

[0040] In certain embodiments wherein the reformer product stream (syngas) is not subjected to a water gas shift reaction and carbon dioxide removal, the concentration of carbon dioxide and / or carbon monoxide in the PSA tail gas may be high enough that the PSA tail gas can be used as a portion of the inlet stream to the methanation unit operation. In embodiments where the PSA tail gas is directed to the methanation unit, the PSA tail gas may first require further processing. For example, the PSA tail gas may first be subjected to a CO2 capture step, where the captured CO2 is ultimately directed as a portion of the inlet stream to the methanation unit.

[0041] In certain configurations, the process may be utilized without a final purification step (e.g., without being subjected to a PSA or methanation process).

[0042] In another embodiment, a SMR process similarly comprises introducing steam and a source gas comprising natural gas into a steam methane reformer to produce a reformer product stream and flue gas from which carbon dioxide is separated (i.e. first carbon dioxide-containing stream). Instead of subjecting the reformer product stream to a water-gas shift reaction, carbon dioxide is first captured from the reformer product stream as a second carbon dioxide-containing stream, resulting in a CO2 depleted reformer product stream. The CO2 depleted reformer product stream is further processed in a cryogenic separation process (e.g., cold box), as described in further detail below, to separate carbon monoxide from the reformer product stream and form a carbon monoxide-containing stream and a CO-depleted reformer product stream. Both the captured carbon dioxide (i.e. second carbon dioxide- containing stream) and the separated carbon monoxide (i.e. carbon monoxide-containing stream) may be directed to a methanation step as an inlet stream as described herein. In certain embodiments, the captured carbon dioxide and the separated carbon monoxide are first combined, and the combined stream is then directed to a methanation step as an inlet stream as described herein.

[0043] In some embodiments, the concentration of CO2 in the first carbon dioxide- containing stream (i.e. a CCh-containing stream separated from the flue gas) may be about 90 wt% or more, about 91 wt% or more, about 92 wt% or more, about 93 wt% or more, about 94 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 98 wt% or more, about 99 wt% or more, or about 99.9 wt% or more. In other embodiments, the concentration of CO2 in the first carbon dioxide-containing stream may be from about 90 wt% to about 99.9 wt%, from about 91 wt% to about 99.9 wt%, from about 92 wt% to about 99.9 wt%, from about 93 wt% to about 99.9 wt%, from about 94 wt% to about 99.9 wt%, from about 95 wt% to about 99.9 wt%, from about 96 wt% to about 99.9 wt%, from about 97 wt% to about 99.9 wt%, from about 98 wt% to about 99.9 wt%, or from about 99 wt% to about 99.9 wt%.

[0044] In some embodiments, the concentration of CO2 in the second carbon dioxide-containing stream may be about 90 wt% or more, about 91 wt% or more, about 92 wt% or more, about 93 wt% or more, about 94 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 98 wt% or more, about 99 wt% or more, or about 99.9 wt% or more. In other embodiments, the concentration of CO2 in the second carbon dioxide- containing stream may be from about 90 wt% to about 99.9 wt%, from about 91 wt% to about 99.9 wt%, from about 92 wt% to about 99.9 wt%, from about 93 wt% to about 99.9 wt%, from about 94 wt% to about 99.9 wt%, from about 95 wt% to about 99.9 wt%, from about 96 wt%to about 99.9 wt%, from about 97 wt% to about 99.9 wt%, from about 98 wt% to about 99.9 wt%, or from about 99 wt% to about 99.9 wt%.

[0045] In certain embodiments, the concentration of CO2 in the hydrogen product stream (e.g., C Ch-depleted hydrogen stream, CO-depleted reformer product stream, or hydrogen rich product stream) may be about 35 wt.% or less, about 30 wt.% or less, about 25 wt.% or less, about 20 wt.% or less, about 15 wt.% or less, about 10 wt.% or less, about 5 wt.% or less, about 4 wt.% or less, about 3 wt.% or less, about 2 wt.% or less, about 1 wt.% or less, about 0.5 wt.% or less, or about 0.25 wt.% or less. For example, from about 35 wt.% to about 0.25 wt.%, from about 30 wt.% to about 0.25 wt.%, from about 25 wt.% to about 0.25 wt.%, from about 20 wt.% to about 0.25 wt.%, from about 10 wt.% to about 0.25 wt.%, from about 5 wt.% to about 0.25 wt.%, from about 4 wt.% to about 0.25 wt.%, from about 3 wt.% to about 0.25 wt.%, from about 2 wt.% to about 0.25 wt.%, from about 1 wt.% to about 0.25 wt.%, or from about 0.5 wt.% to about 0.25 wt.%.

[0046] In embodiments comprising a cryogenic separation process, the concentration of CO in the separated CO stream (i.e. carbon monoxide-containing stream) may be about 90 wt% or more, about 91 wt% or more, about 92 wt% or more, about 93 wt% or more, about 94 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 98 wt% or more, about 99 wt% or more, or about 99.9 wt% or more. In other embodiments, the concentration of CO in the carbon monoxide-containing stream may be from about 90 wt% to about 99.9 wt%, from about 91 wt% to about 99.9 wt%, from about 92 wt% to about 99.9 wt%, from about 93 wt% to about 99.9 wt%, from about 94 wt% to about 99.9 wt%, from about 95 wt% to about 99.9 wt%, from about 96 wt% to about 99.9 wt%, from about 97 wt% to about 99.9 wt%, from about 98 wt% to about 99.9 wt%, or from about 99 wt% to about 99.9 wt%.

[0047] The first carbon dioxide-containing stream, the second carbon dioxidecontaining stream, and / or the carbon monoxide-containing stream may be directed to a methanation process as described in further detail herein. In some embodiments, at least a portion of the first carbon dioxide-containing stream and / or the carbon monoxide-containing stream may be recycled to the burner and combusted and / or recycled to the reformer and converted in presence of steam.

[0048] In certain embodiments, the hydrogen product stream of the SMR may be used to produce further products (e.g., ammonia, methanol, etc.).

[0049] Various improvements to the steam methane reforming process may be enacted to increase the overall performance of the process and / or purity of the product. For example, in one embodiment, at least a portion of the hydrogen product stream may be directed to a hydrogen-fueled gas turbine as a source of fuel and the hydrogen-fueled gas turbine exhaust gas may be used to produce at least a portion of the heated gas introduced into the steam methane reformer. In another embodiment, the reformer product stream is also cooled, producing steam. At least a portion of this steam is then directed to the hydrogen-fueled gas turbine as a diluent.Autothermal Reforming (ATR)

[0050] An autothermal reforming (ATR) process conducts a high temperature catalytic reforming reaction, similar to an SMR process, to convert a source gas comprising a hydrocarbon into a syngas. However, in an ATR process, the majority of the source of the heat for the reaction is not external to the reformer. Instead, a majority of the heat is produced by the combustion of natural gas and oxygen directly in the catalyst bed of the auto-thermal reformer.

[0051] An autothermal reforming (ATR) process generally comprises a pre-heater upstream of an auto-thermal reformer. Natural gas is combusted in a pre-heater unit operation to generate heat and produce a heated natural gas stream and a flue gas stream from which carbon dioxide is separated (i.e. first carbon dioxide-containing stream). The heated natural gas stream is at a temperature lower than that of the temperature of the downstream auto-thermal reformer. The resulting stream is then directed to the auto-thermal reformer where it is combusted with oxygen in the presence of steam in a catalyst bed. The oxygen used in this process may be substantially pure. For example, about 95 wt% or greater, about 99 wt% or greater, about 99.5 wt% or greater, or about 99.9 wt% or greater. Since the auto-thermal reformer conducts a catalytic reaction of natural gas at high temperatures, a reforming reaction similar to that of the steam methane reforming reaction described above takes place. The autothermal reaction produces a hot syngas mixture that may be further processed as discussed herein.

[0052] The hot syngas resulting from the ATR process is cooled in a series of heat exchanges, including a boiler to produce steam. The steam may be optionally recycled to the inlet of the ATR to be mixed with the feed gas and the oxygen, or used elsewhere in the pre- heating / pre-treatment process as a source of heat. The steam produced from the cooled syngas may also or alternatively be used for other purposes in the plant (e.g. steam turbine drivers forcompressors, steam turbine generators, etc.). In certain configurations, the hot syngas may be cooled by the incoming natural gas feed, in order to reduce pre-heating needs for the incoming natural gas.

[0053] The cooled syngas (i.e. reformer product stream) is then directed to one or more water-gas shift reactors, one or more CO2 capture steps, and one or more optional purification (e.g., PSA) steps. Each of the water-gas shift, CO2 capture, and optional purification steps are conducted in the manner set forth above with respect to the SMR process. In certain embodiments, at least a portion of the impurities from the PSA and / or other purification step(s) may be recycled to the pre-heater as a fuel and / or recycled directly to the inlet of the auto-thermal reformer.

[0054] Alternatively, the CO2 might be recovered from a PSA tail gas through other purification step(s) to produce a second carbon dioxide-containing stream and utilized as described in further detail below. For example, in certain embodiments wherein the reformer product stream (syngas) is not subjected to a water gas shift reaction and carbon dioxide removal, the concentration of carbon dioxide and / or carbon monoxide in the PSA tail gas may be high enough that the PSA tail gas can be used as a portion of the inlet stream to the methanation unit operation. In embodiments where the PSA tail gas is directed to the methanation unit, the PSA tail gas may first require further processing. For example, the PSA tail gas may first be subjected to a CO2 capture step, where the captured CO2 is ultimately directed as a portion of the inlet stream to the methanation unit.

[0055] In another embodiment, an ATR process comprises introducing source gas comprising natural gas into a reformer to produce a syngas comprising hydrogen, carbon monoxide, carbon dioxide, and methane and a flue gas stream comprising carbon dioxide (i.e. from which a first carbon dioxide-containing stream is separated). Instead of subjecting the syngas to a water-gas shift reaction, carbon dioxide is first captured from the syngas as a second carbon dioxide-containing stream. The CO2 depleted syngas stream is further processed in a cryogenic separation process, as described in further detail below, to separate carbon monoxide from the syngas and form a carbon monoxide-containing stream. Both the captured carbon dioxide (i.e. first carbon dioxide-containing stream) and the separated carbon monoxide (i.e. carbon monoxide-containing stream) may be directed to the methanation unit to form a portion of the inlet stream, or may be combined and then directed to a methanation step as an inlet stream as described herein. In some embodiments, a a first carbon dioxide-containing streammay be separated from the flue gas and also combined and directed as an inlet stream to the methanation step.

[0056] In certain configurations, the process may be utilized without a final purification step (e.g., without being subjected to a PSA or methanation process).

[0057] Figure 4 illustrates one embodiment of an ATR process. In Figure 4, the ATR process comprises heating a source gas comprising natural gas in a pre-heater and contacting the heated source gas, a source of steam, and a source of oxygen in an autothermal reformer to produce a reformer product stream (syngas). Steam is generated from the latent heat of the reformer product stream, wherein at least a portion of the source of steam introduced in the autothermal reformer comprises steam generated from the latent heat of the reformer product stream. The reformer product stream is subjected to a water-gas shift reaction to produce a water-gas shift product stream; the water-gas shift reaction comprising reacting the carbon monoxide with water to produce carbon dioxide and hydrogen. Carbon dioxide is removed from the water-gas shift product stream to produce a CCh-depleted hydrogen stream and a second carbon dioxide-containing stream. Finally, the CCh-depleted hydrogen stream is subjected to an optional pressure-swing adsorption process to adsorb at least a portion of the impurities and produce a pure hydrogen product stream and a PSA tail gas that may be recycled to the feed preheater for combustion.

[0058] In some embodiments, the concentration of CO2 in the first carbon dioxide- containing stream (i.e. that is separated from the flue gas) may be about 90 wt% or more, about 91 wt% or more, about 92 wt% or more, about 93 wt% or more, about 94 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 98 wt% or more, about 99 wt% or more, or about 99.9 wt% or more. In other embodiments, the concentration of CO2 in the first carbon dioxide-containing stream may be from about 90 wt% to about 99.9 wt%, from about 91 wt% to about 99.9 wt%, from about 92 wt% to about 99.9 wt%, from about 93 wt% to about 99.9 wt%, from about 94 wt% to about 99.9 wt%, from about 95 wt% to about 99.9 wt%, from about 96 wt% to about 99.9 wt%, from about 97 wt% to about 99.9 wt%, from about 98 wt% to about 99.9 wt%, or from about 99 wt% to about 99.9 wt%.

[0059] In some embodiments, the concentration of CO2 in the second carbon dioxide-containing stream may be about 90 wt% or more, about 91 wt% or more, about 92 wt% or more, about 93 wt% or more, about 94 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 98 wt% or more, about 99 wt% or more, or about 99.9 wt% or more. In other embodiments, the concentration of CO2 in the second carbon dioxide-containing stream may be from about 90 wt% to about 99.9 wt%, from about 91 wt% to about 99.9 wt%, from about 92 wt% to about 99.9 wt%, from about 93 wt% to about 99.9 wt%, from about 94 wt% to about 99.9 wt%, from about 95 wt% to about 99.9 wt%, from about 96 wt% to about 99.9 wt%, from about 97 wt% to about 99.9 wt%, from about 98 wt% to about 99.9 wt%, or from about 99 wt% to about 99.9 wt%.

[0060] In various embodiments, the concentration of CO2 in the CCh-depleted hydrogen stream may be about 35 wt.% or less, about 30 wt.% or less, about 25 wt.% or less, about 20 wt.% or less, about 15 wt.% or less, about 10 wt.% or less, about 5 wt.% or less, about 4 wt.% or less, about 3 wt.% or less, about 2 wt.% or less, about 1 wt.% or less, about 0.5 wt.% or less, or about 0.25 wt.% or less. For example, from about 35 wt.% to about 0.25 wt.%, from about 30 wt.% to about 0.25 wt.%, from about 25 wt.% to about 0.25 wt.%, from about 20 wt.% to about 0.25 wt.%, from about 10 wt.% to about 0.25 wt.%, from about 5 wt.% to about 0.25 wt.%, from about 4 wt.% to about 0.25 wt.%, from about 3 wt.% to about 0.25 wt.%, from about 2 wt.% to about 0.25 wt.%, from about 1 wt.% to about 0.25 wt.%, or from about 0.5 wt.% to about 0.25 wt.%.

[0061] In embodiments comprising a cryogenic separation process of CO from the syngas, the concentration of CO in the separated CO stream (i.e. carbon monoxide-containing stream) may be about 90 wt% or more, about 91 wt% or more, about 92 wt% or more, about 93 wt% or more, about 94 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 98 wt% or more, about 99 wt% or more, or about 99.9 wt% or more. In other embodiments, the concentration of CO in the carbon monoxide-containing stream may be from about 90 wt% to about 99.9 wt%, from about 91 wt% to about 99.9 wt%, from about 92 wt% to about 99.9 wt%, from about 93 wt% to about 99.9 wt%, from about 94 wt% to about 99.9 wt%, from about 95 wt% to about 99.9 wt%, from about 96 wt% to about 99.9 wt%, from about 97 wt% to about 99.9 wt%, from about 98 wt% to about 99.9 wt%, or from about 99 wt% to about 99.9 wt%.

[0062] In certain embodiments, at least a portion of the hydrogen product stream is directed to a hydrogen-fueled gas turbine as a source of fuel. In certain embodiments, the hydrogen-fueled gas turbine produces exhaust gas that is used to heat the source gas comprising natural gas in the pre-heater.

[0063] In other embodiments, at least a portion of the hydrogen product stream is directed to a hydrogen-fueled gas turbine as a source of fuel and the hydrogen-fueled gas turbine produces exhaust gas that is used to heat the source gas comprising natural gas in thepre-heater. The reformer product stream is also cooled, producing steam. At least a portion of this steam is then directed to the hydrogen-fueled gas turbine as a diluent.Partial Oxidation (POx)

[0064] A partial oxidation (POx) process typically comprises combustion of a sub stoichiometric fuel-to-air mixture in a reformer. For example, the partial oxidation of methane (i.e. fuel) creates a hydrogen-rich syngas.

[0065] Thermal partial oxidation is a process wherein the generation of syngas depends upon the fuel-to-air ratio directed to the reformer and the temperature used in the reaction. In a thermal partial oxidation reaction, the operating temperature is typically between about 1200°C and about 1500°C or greater than about 1200°C.

[0066] The syngas produced by the partial oxidation reaction may be processed in any of the manners described above with respect to SMR or ATR processes. For example, the reformer product stream (syngas) may be subjected to a water gas shift, CO2 capture (to produce a CCh-depleted hydrogen stream and a second carbon dioxide-containing stream), and optional further purification steps (e.g., PSA). In other embodiments, instead of subjecting the reformer product stream to a water-gas shift reaction, carbon dioxide is first captured from the reformer product stream to form the second carbon dioxide-containing stream. The reformer product stream is then processed in a cryogenic separation process, as described in further detail below, to separate carbon monoxide from the reformer product stream and form a carbon monoxide-containing stream. The first carbon dioxide-containing stream (i.e. that is separated from the flue gas), second carbon dioxide-containing stream, carbon monoxide-containing stream, or combinations thereof may be then be directed to the methanation process as an inlet stream.

[0067] In some embodiments, the concentration of CO2 in the first carbon dioxide- containing stream (i.e. that is separated from the flue gas) may be about 90 wt% or more, about 91 wt% or more, about 92 wt% or more, about 93 wt% or more, about 94 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 98 wt% or more, about 99 wt% or more, or about 99.9 wt% or more. In other embodiments, the concentration of CO2 in the first carbon dioxide-containing stream may be from about 90 wt% to about 99.9 wt%, from about 91 wt% to about 99.9 wt%, from about 92 wt% to about 99.9 wt%, from about 93 wt% to about 99.9 wt%, from about 94 wt% to about 99.9 wt%, from about 95 wt% to about99.9 wt%, from about 96 wt% to about 99.9 wt%, from about 97 wt% to about 99.9 wt%, from about 98 wt% to about 99.9 wt%, or from about 99 wt% to about 99.9 wt%.

[0068] In some embodiments, the concentration of CO2 in the second carbon dioxide-containing stream may be about 90 wt% or more, about 91 wt% or more, about 92 wt% or more, about 93 wt% or more, about 94 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 98 wt% or more, about 99 wt% or more, or about 99.9 wt% or more. In other embodiments, the concentration of CO2 in the second carbon dioxide- containing stream may be from about 90 wt% to about 99.9 wt%, from about 91 wt% to about 99.9 wt%, from about 92 wt% to about 99.9 wt%, from about 93 wt% to about 99.9 wt%, from about 94 wt% to about 99.9 wt%, from about 95 wt% to about 99.9 wt%, from about 96 wt% to about 99.9 wt%, from about 97 wt% to about 99.9 wt%, from about 98 wt% to about 99.9 wt%, or from about 99 wt% to about 99.9 wt%.

[0069] In various embodiments, the concentration of CO2 in the CCh-depleted hydrogen stream may be about 35 wt.% or less, about 30 wt.% or less, about 25 wt.% or less, about 20 wt.% or less, about 15 wt.% or less, about 10 wt.% or less, about 5 wt.% or less, about 4 wt.% or less, about 3 wt.% or less, about 2 wt.% or less, about 1 wt.% or less, about 0.5 wt.% or less, or about 0.25 wt.% or less. For example, from about 35 wt.% to about 0.25 wt.%, from about 30 wt.% to about 0.25 wt.%, from about 25 wt.% to about 0.25 wt.%, from about 20 wt.% to about 0.25 wt.%, from about 10 wt.% to about 0.25 wt.%, from about 5 wt.% to about 0.25 wt.%, from about 4 wt.% to about 0.25 wt.%, from about 3 wt.% to about 0.25 wt.%, from about 2 wt.% to about 0.25 wt.%, from about 1 wt.% to about 0.25 wt.%, or from about 0.5 wt.% to about 0.25 wt.%.

[0070] In embodiments comprising a cryogenic separation process, the concentration of CO in the separated CO stream (i.e. carbon monoxide-containing stream) may be about 90 wt% or more, about 91 wt% or more, about 92 wt% or more, about 93 wt% or more, about 94 wt% or more, about 95 wt% or more, about 96 wt% or more, about 97 wt% or more, about 98 wt% or more, about 99 wt% or more, or about 99.9 wt% or more. In other embodiments, the concentration of CO in the carbon monoxide-containing stream may be from about 90 wt% to about 99.9 wt%, from about 91 wt% to about 99.9 wt%, from about 92 wt% to about 99.9 wt%, from about 93 wt% to about 99.9 wt%, from about 94 wt% to about 99.9 wt%, from about 95 wt% to about 99.9 wt%, from about 96 wt% to about 99.9 wt%, from about 97 wt% to about 99.9 wt%, from about 98 wt% to about 99.9 wt%, or from about 99 wt% to about 99.9 wt%.

[0071] In SMR, ATR, or partial oxidation operations, prior to the reforming process, the feed stream may be subjected to an optional pre-treatment unit operation where sulfur compounds are removed and long hydrocarbons are pre-reformed. Pre-reforming entails steam reforming of a portion of the feed stream and methanation of the heavier hydrocarbons resulting from the pre-reforming operation. The feed stream may also be subjected to other pretreatment unit operation(s) as required for the efficiency and / or economic viability of the process.

[0072] Although reference is made herein to producing a first carbon dioxidecontaining stream (i.e. that is separated from the flue gas), second carbon dioxide-containing stream, and carbon monoxide-containing stream, and directing these streams to the methanation unit, it will be understood that process or economic considerations may impact whether each of these streams are recovered or utilized. For example, in certain embodiments, capture and / or concentration of carbon dioxide from the flue gas may not be economically feasible. In such an embodiment, the process may not comprise recovering a first carbon dioxide-containing stream and using this stream in the methanation process. Similarly, in certain embodiments, capture and / or concentration of carbon dioxide from the second carbon dioxide-containing stream may not be economically feasible. In such an embodiment, the process may not comprise recovering a second carbon dioxide-containing stream and using this stream in the methanation process. Still further, in certain embodiments, the carbon monoxide- containing stream may not have a sufficient carbon monoxide content, or capture and / or concentration of carbon monoxide from this stream may not be economically feasible. In such an embodiment, the process may not comprise recovering a carbon monoxide-containing stream and using this stream in the methanation process.

[0073] While reference has been made herein to specific configurations, including as illustrated in the figures, it will be well understood that various design modifications may be undertaken and still be within the scope of the present disclosure. For example, the postreforming steps (e.g., CO2 capture, water-gas-shift, cryogenic separation, etc.) may be conducted in any order, multiple iterations of each step may be performed (e.g., multiple CO2 capture steps in series), or other design modifications may be made to improve the operations and / or the CO2 and / or CO capture of the process. Still further, the reforming unit operations may comprise one or more optional pre-treatment, pre-processing, pre-heating, etc. steps prior to reforming.

[0074] In certain embodiments, the heated natural gas stream may be optionally directed to a pre-treatment unit operation where at least a portion of the heated hydrocarbon feed stream is pre-reformed to form methane and / or where the heated natural gas stream is otherwise treated (e.g., to remove sulfur).CO2 and / or CO Gas Capture

[0075] During the SMR, ATR, or partial oxidation operations discussed above, carbon monoxide, carbon dioxide, or other byproducts may be produced. For example, at various points in the SMR, ATR, or partial oxidation processes there may be present a CO2- containing flue gas (i.e. or a first carbon dioxide-containing stream separated therefrom), syngas (e.g., comprising a mixture of H2, CO, CO2, and / or CH4), water-gas shift product stream, captured CO2 (i.e. second carbon dioxide-containing stream), separated CO stream (i.e. carbon monoxide-containing stream) from a CO cryogenic separation (e.g., cold box) operation, or other waste streams comprising CO2 and / or CO. Any of these streams may be utilized as a source of carbon dioxide for the methanation step described herein. Alternatively, any of these streams may be optionally subjected to further processing prior to use as a source of carbon dioxide for the methanation step described herein. For example, purification / concentration steps to concentrate the carbon dioxide prior to use as the inlet stream to the methanation step.

[0076] In some embodiments, CO cryogenic separation may be used to separate carbon monoxide from syngas or other streams produced during a SMR, ATR, or partial oxidation process. The cryogenic separation may be any conventional cryogenic separation process suitable for the separation of carbon monoxide. For example, the CO cryogenic separation process may comprise a design utilizing a methane wash (e.g., scrubbing with liquid methane), partial condensation, or a carbon monoxide wash. In certain embodiments, the CO cryogenic separation process comprises a methane wash. In other embodiments, the CO cryogenic separation process comprises partial condensation.

[0077] The above-identified streams of the SMR, ATR, or partial oxidation operations (or the result of further processing of these streams (e.g., by a cryogenic separation process)) may then be utilized as at least a portion of the inlet stream comprising carbon dioxide that is directed to the methanation unit operation of the present invention. For example, in one embodiment, the carbon monoxide recovered in the cryogenic separation step may be directed to the methanation unit in addition to the inlet stream comprising carbon dioxide or may be combined with the inlet stream prior to introduction into the methanation unit.Hydrogen Generation

[0078] The hydrogen gas utilized for the methanation step comprises externally produced hydrogen. That is, hydrogen not originating from the SMR, ATR, or partial oxidation operations that provide the carbon dioxide and / or carbon monoxide for the methanation step. In certain embodiments, at least a portion of the hydrogen gas introduced into the methanation unit for formation of a methanation product stream may be prepared by "green" or low- emission technologies.

[0079] For example, in one embodiment, at least a portion of the hydrogen gas introduced into the methanation unit is prepared by a water electrolysis process. Water electrolysis (i.e. water splitting) generally comprises the introduction of electrical energy into water to separate water into its constituent components of oxygen and hydrogen gas. The water electrolysis process may comprise any suitable water electrolyzer. For example, Silyzer (commercially available from Siemens Energy).

[0080] In other embodiments, at least a portion of the hydrogen gas introduced into the methanation unit is prepared by pyrolysis of a feed stream selected from the group consisting of biomass, natural gas, waste products, or combinations thereof.

[0081] In the water electrolysis process (or any other "green" or low-emission process for forming hydrogen gas), at least a portion of the energy used to produce the hydrogen gas may be a renewable or low-emission energy source. For example, in one embodiment, the renewable energy is selected from the group consisting of solar energy, wind energy, geothermal energy, hydroelectric energy, tidal energy, or nuclear energy.Methanation

[0082] The present invention is directed to the conversion of hydrogen and one or more of CO2 and CO in a methanation operation, and transport of the methanation product stream to a second location.

[0083] Methanation is a process for the conversion of carbon dioxide and / or carbon monoxide to methane using a hydrogenation reaction. The hydrogenation reaction typically takes place in the presence of a catalyst. For example, the methanation catalyst may comprise nickel, palladium, platinum, or combinations thereof. The reaction generally follows the reaction schemes set forth below.CO + 3 H2CH4+ H2O

[0084] The methanation process produces a methanation product stream comprising methane. As noted in the above reaction schemes, the methanation reaction is exothermic and produces high amounts of heat. Another byproduct of this methanation reaction is water.

[0085] The water produced from the methanation process comes from the molecules of hydrogen brought to the methanation process. Because the desired product from the methanation process is methane, rather than water, it may be desirable in certain embodiment to complement the "green" source of hydrogen with hydrogen from other sources (e.g., from the SMR, ATR, or partial oxidation). In such embodiments, a second stream of hydrogen may be added from the SMR, ATR or POx and mixed with the "green" hydrogen stream. Under certain regulatory regimes, such an embodiment may be considered by the regulator to transform a higher percentage of the green hydrogen into methane (as opposed to transforming this hydrogen into water) for transport to the second location. That is, in certain situations, it may be possible to assert that the water produced during methanation is a result of the hydrogen from other sources, and the methane produced during the methanation process is a result of the green hydrogen. A greater benefit may be achieved under these regulatory regimes by asserting that the hydrogen recovered at the second location is a majority or wholly based upon the green hydrogen produced at the first location.

[0086] The heat generated in the methanation process may be recovered and recycled to nearby plant operations in order to realize cost savings. For example, the heat may be used in a boiler to produce steam to drive turbomachinery or power generators. In such embodiments, the steam produced from the methanation reaction may drive the compressors of an air separation unit supplying oxygen to the ATR.

[0087] The water generated in the methanation process may also be recovered and recycled to nearby plant operations in order to realize cost savings. For example, the water may be directed to water treatment before feeding a water electrolysis process to produce hydrogen further re-used in the methanation loop, as described elsewhere herein or utilized in steam generation operations, water gas shift operations, or other aspects of a natural gas reforming process that require water.

[0088] In certain embodiments, the methanation process is directed to conversion of an inlet stream comprising carbon dioxide and / or carbon monoxide, wherein at least a portion of the carbon dioxide and / or carbon monoxide is recovered from SMR, ATR, or partial oxidation operations as described above. In one embodiment, the gases converted in the methanation unit operation (i.e. the inlet stream) may comprise one of more of the following sources: carbon dioxide-containing streams resulting from combustion in the steam methane reformer, autothermal reformer pre-heater, autothermal reformer, or partial oxidation reformer, syngas (e.g., comprising a mixture of H2, CO, CO2, and / or CH4), a water-gas shift product stream, captured CO2 streams (i.e., a second carbon dioxide-containing stream), a separated CO stream (i.e. carbon monoxide-containing stream) from a cryogenic separation process, or other waste streams comprising CO2 and / or CO. In other embodiments, the gases converted in the methanation unit operation (i.e. the inlet stream) may comprise the first carbon dioxide- containing stream, the second carbon dioxide-containing stream, separated CO stream, or combinations thereof, as described above.

[0089] As explained elsewhere herein, the inlet stream directed to the methanation process may comprise a CO stream originating from a CO cryogenic separation process during the SMR, ATR, or partial oxidation process. Carbon monoxide generally has a higher conversion efficiency to methane in a methanation process than carbon dioxide. Therefore, in certain embodiments, it may be desirable to separately capture carbon monoxide from the SMR, ATR, or partial oxidation process (e.g., by a cryogenic separation process) and direct that carbon monoxide-containing stream directly to the methanation unit. In other embodiments, the carbon monoxide-containing stream may be combined with the carbon dioxide-containing stream(s) prior to introduction into the methanation unit. One embodiment of the present invention is directed to supplying a carbon monoxide-containing stream directly to the methanation unit. Another embodiment of the present invention is directed to combining a carbon monoxide-containing stream and a carbon dioxide-containing stream (e.g., the first carbon dioxide-containing stream and / or the second carbon dioxide-containing stream) and supplying the combined stream to the methanation unit.

[0090] In one embodiment, the methanation unit operation is conducted at a first location that also contains a source of hydrogen gas or a hydrogen gas production operation. In another embodiment, the methanation unit operation is conducted at a first location that also contains a source of carbon dioxide-containing inlet gas. In some embodiments, the methanation unit operation is conducted at a first location that contains both a source ofhydrogen gas or a hydrogen gas production operation and a source of carbon dioxidecontaining inlet gas.

[0091] In certain embodiments, the methanation product stream comprises about 50 vol.% or greater, about 60 vol.% or greater, about 70 vol.% or greater, about 80 vol.% or greater, about 90 vol.% or greater, about 95 vol.% or greater, about 96 vol.% or greater, about 97 vol.% or greater, about 98 vol.% or greater, or about 99 vol.% or greater of methane. In other embodiments, the methanation product stream comprises from about 25 vol.% to about 100 vol.%, from about 30 vol.% to about 100 vol.%, from about 40 vol.% to about 100 vol.%, from about 50 vol.% to about 100 vol.%, from about 60 vol.% to about 100 vol.%, from about 70 vol.% to about 100 vol.%, from about 70 vol.% to about 99 wt%, from about 70 vol.% to about 98 vol.%, from about 70 vol.% to about 97 vol.%, from about 70 vol.% to about 96 vol.%, or from about 70 wt% to about 98 vol.% of methane.Transportation and Processing of Methanation Product Stream at a Second Location

[0092] The present invention is further directed to the transportation of the methanation product stream comprising methane from a first location to a second location.

[0093] In some embodiments, the distance between the first location and the second location may be about 100 feet or greater, about 1,000 feet or greater, about 2,000 feet or greater, about 3,000 feet or greater, about 4,000 feet or greater, about 5,000 feet or greater, about 1 mile or greater, about 5 miles or greater, about 10 miles or greater, about 15 miles or greater, about 20 miles or greater, about 25 miles or greater, about 50 miles or greater, about 75 miles or greater, about 100 miles or greater, about 200 miles or greater, about 300 miles or greater, about 400 miles or greater, about 500 miles or greater, or about 1,000 miles or greater.

[0094] In other embodiments, the distance between the first location and the second location may be from about 100 feet to about 1,000 miles, from about 1,000 feet to about 1,000 miles, from about 2,000 feet to about 1,000 miles, from about 3,000 feet to about 1,000 miles, from about 4,000 feet to about 1,000 miles, from about 5,000 feet to about 1,000 miles, from about 1 mile to about 1,000 miles, from about 5 miles to about 1,000 miles, from about 10 miles to about 1,000 miles, from about 15 miles to about 1,000 miles, from about 20 miles to about 1,000 miles, from about 25 miles to about 1,000 miles, from about 50 miles to about 1,000 miles, from about 75 miles to about 1,000 miles, from about 100 miles to about 1,000 miles, from about 200 miles to about 1,000 miles, or from about 250 miles to about 1,000 miles.

[0095] At the second location, the methanation product stream comprising methane is converted to prepare the desired product streams. In one embodiment, the conversion process entails converting the methanation product stream comprising methane back into the separate streams which were used to form the methanation product, namely a carbon dioxide-containing stream and a hydrogen gas stream. For example, the methanation product stream may be converted at the second location into a first product stream comprising hydrogen and a second product stream comprising carbon dioxide. This conversion process may comprise any suitable process for preparing the first product stream and second product stream. For example, in one embodiment, the methanation product stream is converted to the first product stream and second product stream utilizing an SMR, ATR, or partial oxidation process as described above.

[0096] In some embodiments, the distance between the first location and the second location may be about 100 feet or greater, about 1,000 feet or greater, about 2,000 feet or greater, about 3,000 feet or greater, about 4,000 feet or greater, about 5,000 feet or greater, about 1 mile or greater, about 5 miles or greater, about 10 miles or greater, about 15 miles or greater, about 20 miles or greater, about 25 miles or greater, about 50 miles or greater, about 75 miles or greater, about 100 miles or greater, about 200 miles or greater, about 300 miles or greater, about 400 miles or greater, or about 500 miles or greater. Transforming the carbon dioxide and / or carbon monoxide into a methanation product stream comprising methane allows for easier transport in existing natural gas pipeline networks and is easily recovered at the second location as a carbon dioxide and / or carbon monoxide stream by subjecting the stream to conversion. Likewise, transforming the hydrogen into a methanation product stream comprising methane allows for easier transport in existing natural gas pipeline networks and is easily recovered at the second location as a hydrogen gas by subjecting the stream to conversion.

[0097] Numerous additional benefits may be realized by transporting the carbon dioxide and / or carbon monoxide as described above. When carbon dioxide and / or carbon monoxide is transported across such distances, the regulatory conditions, available land and equipment, and operation costs can vary widely between the two locations. For example, in certain regulatory schemes, it may be costly to sequester, dispose of, or otherwise process carbon dioxide and carbon monoxide. In some situations, the first location where a SMR, ATR, or partial oxidation process produces carbon dioxide and / or carbon monoxide may have land cost that is so prohibitive that these gases cannot be efficiently processed or sequestered on-site. In other situations, the regulatory scheme in the first location may be such that processing or sequestering of these gases would be burdensome or cost prohibitive. By transporting the carbon dioxide and / or carbon monoxide to a second location, it is possible to take advantage of cheaper land costs and / or a more favourable regulatory regime. For example, the carbon dioxide and / or carbon monoxide may be transported from a costal or high population center where the SMR, ATR, or partial oxidation process is conducted and sequestered in a more rural or less-populous location. Similarly, the carbon dioxide and / or carbon monoxide may be transported from a state having stringent requirements as to the processing of greenhouses gases to a state having less stringent environmental or regulatory requirements related to the processing of greenhouse gases.

[0098] Similarly, when hydrogen is transported across such distances, the regulatory conditions, available land and equipment, and operation costs can vary widely between the two locations. For example, hydrogen may be more efficiently and economically produced at a first location that is adjacent to water and / or has low energy costs. This is particularly important when hydrogen gas is prepared using "green" or low-emission technologies as described above. The "green" hydrogen can then be transported to a second location where "green" hydrogen can be sold at a higher price, where the regulatory scheme provides compensation or rebates or obligations for using "green" hydrogen, or where the regulatory scheme imposes penalties for not using "green" or low-emission fuel sources. This process is particularly useful in situations where renewable, "green", or low-emission energy is readily available at a first location, but unavailable at a second location. Further, the transportation of hydrogen gas (i.e. not the transportation of a methanation product as described herein) typically requires high compression and power costs. The hydrogen gas must be pressured for transport to form a liquified hydrogen and maintained at very low temperatures. The present disclosure negates the need for such costly transport requirements.

[0099] Figure 5 presents an exemplary flow diagram of one embodiment of the process of the present invention. Figure 5 illustrates a flow diagram of a process wherein steam methane reforming, water electrolysis, and methanation occur at a first location. The reformer produces a flue gas (from which a first carbon dioxide-containing stream is separated) and reformer product stream (syngas), which is the contacted with water in a water-gas-shift reaction to convert carbon monoxide into carbon monoxide and hydrogen. Carbon dioxide is captured from the product of this shift reaction as a second carbon dioxide-containing stream. The second carbon dioxide-containing stream is combined with other CCh-containing gas(es)captured from the flue gas of the reformer (e.g., the first carbon dioxide-containing stream separated from the flue gas) and the combined stream is directed to a methanation step as an inlet stream comprising carbon dioxide. Hydrogen produced from a water electrolysis process is also fed to the methanation unit. Hydrogen and carbon dioxide are then reacted in the methanation unit to produce water and a methanation product stream comprising methane. The water produced in the methanation step is recycled to the water electrolysis step or to the steam methane reforming process for steam generation or use in the water-gas-shift reaction. The methanation product stream comprising methane is directed to a second location wherein the stream is subjected to a reformation unit operation whereby hydrogen is generated and carbon dioxide is captured. The carbon dioxide may be sequestered or otherwise processed and the hydrogen may be used as a "green" hydrogen at the second location.

[0100] Figure 6 presents a flow diagram similar to that of Figure 5. In Figure 6, the reformer produces a flue gas (from which a first carbon dioxide-containing stream is separated) and stream of syngas (reformer product stream). Carbon dioxide is captured from the syngas as a second carbon dioxide-containing stream and the syngas is further processed in a cryogenic separation process to separate carbon monoxide from the syngas. Both the captured carbon dioxide (i.e. second carbon dioxide-containing stream) and the separated carbon monoxide (i.e. carbon dioxide-containing stream) are combined with other CCh-containing gas(es) captured from the flue gas of the reformer (e.g., the first carbon dioxide-containing stream separated from the flue gas) and the combined stream is directed to a methanation step as an inlet stream comprising carbon dioxide. The process then progresses as otherwise set forth in Figure 5.

[0101] Figure 7 presents an exemplary flow diagram of one embodiment of the process of the present invention. Figure 7 illustrates a flow diagram of a process wherein autothermal reforming, water electrolysis, and methanation occur at a first location. A portion of the hydrocarbon feed stream is directed to a preheater to produce a flue gas (from which a first carbon dioxide-containing stream is separated) and a heated feed stream. The feed stream is then directed for pre-treatment and sent to the autothermal reformer. The autothermal reformer produces a stream of syngas, which is contacted with water in a water-gas-shift reaction to convert carbon monoxide into carbon monoxide and hydrogen. Carbon dioxide is captured from the product of this shift reaction as a second carbon-dioxide containing stream. The second carbon-dioxide containing stream is directed to a methanation step as an inlet stream comprising carbon dioxide. Optionally the first carbon dioxide-containing streamseparated from the flue gas may also be directed to the methanation unit. Hydrogen produced from a water electrolysis process is fed to the methanation unit. Hydrogen and the inlet stream comprising carbon dioxide are then reacted it the methanation unit to produce water and a methanation product stream comprising methane. The water produced in the methanation step is recycled to the water electrolysis step and / or for steam generation in the ATR process. The methanation product stream comprising methane is directed to a second location wherein the stream is subjected to a reformation unit operation whereby hydrogen is generated and carbon dioxide is captured. The carbon dioxide may be sequestered or otherwise processed and the hydrogen may be used as a "green" hydrogen at the second location.

[0102] Figure 8 presents a flow diagram similar to that of Figure 7. In Figure 8, the autothermal reformer produces a stream of syngas. Carbon dioxide is captured from the syngas (reformer product stream) and the syngas is further processed in a cryogenic separation process to separate carbon monoxide from the syngas. The captured carbon dioxide and the separated carbon monoxide are combined and the combined stream is directed to a methanation step as an inlet stream comprising carbon dioxide. The process then progresses as otherwise set forth in Figure 7.

[0103] When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles "a", "an", "the" and "said" are intended to mean that there are one or more of the elements. The terms "comprising", "including" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0104] In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

[0105] As various changes could be made in the above products and methods without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

Claims

WHAT IS CLAIMED IS:

1. A process for transporting gas, comprising: providing hydrogen gas and an inlet stream comprising carbon dioxide to a methanation unit; methanating the hydrogen gas and the inlet stream in a first location to produce a methanation product stream comprising methane; transporting the methanation product stream to a second location; and converting the methanation product stream at the second location to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide.

2. The process of claim 1, wherein the conversion process at the second location comprises steam methane reforming (SMR), auto-thermal reforming (ATR), or partial oxidation (POx)3. The process of claim 1 or 2, wherein at least a portion of the hydrogen gas provided to the methanation unit is produced by electrolysis or pyrolysis4. The process of claim 3, wherein the electrolysis is powered using renewable energy selected from the group consisting of solar energy, wind energy, geothermal energy, hydroelectric energy, tidal energy, or nuclear energy.

5. The process of claim 3, wherein the pyrolysis comprises a feed stream selected from the group consisting of biomass, natural gas, waste products, or combinations thereof.

6. The process of any one of claims 1 to 5, wherein at least a portion of the inlet stream comprising carbon dioxide is produced by a process comprising steam methane reforming (SMR), autothermal reforming (ATR), or partial oxidation (POx).

7. The process of any one of claims 1 to 6, wherein methanating the hydrogen gas and the inlet stream further produces water, and the water is recovered and recycled to one or more of the electrolysis, SMR, ATR, or POx processes.

8. The process of any one of claims 1 to 7, wherein the second product stream is sequestered or utilized at the second location.

9. The process of any one of claims 1 to 8, wherein the distance between the first location and the second location is about 100 feet or greater, about 1,000 feet or greater, about 2,000 feet or greater, about 3,000 feet or greater, about 4,000 feet or greater, about 5,000 feet or greater, about 1 mile or greater, about 5 miles or greater, about 10 miles or greater, about 15 miles or greater, about 20 miles or greater, about 25 miles or greater, about 50 miles or greater, about 75 miles or greater, about 100 miles or greater, about 200 miles or greater, about 300 miles or greater, about 400 miles or greater, or about 500 miles or greater.

10. The process of any one of claims 1 to 9, wherein the methanation product stream is transported to the second location via a gaseous pipeline.

11. A process for transporting gas, comprising: a steam methane reforming process comprising: providing a source gas comprising natural gas into a steam methane reformer to produce a flue gas from which a first carbon-dioxide containing stream is separated and a reformer product stream; subjecting the reformer product stream to a water-gas shift reaction to produce a water-gas shift product stream; the water-gas shift reaction comprising reacting carbon monoxide from the reformer product stream with water to produce carbon dioxide and hydrogen; removing carbon dioxide from the water-gas shift product stream to produce a CCh-depleted hydrogen stream and a second carbon dioxidecontaining stream; and optionally subjecting the C Ch-depleted hydrogen stream to a pressureswing adsorption process to adsorb at least a portion of the undesirable components and produce a hydrogen rich product stream and a depleted hydrogen product stream; providing hydrogen gas and an inlet stream comprising one or more of the first carbon dioxide-containing stream, the second carbon dioxide-containing stream, or a combination thereof to a methanation unit; methanating the hydrogen gas and the inlet stream in a first location to produce a methanation product stream comprising methane;transporting the methanation product stream to a second location; and converting the methanation product stream at a second location to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide.

12. A process for transporting gas, comprising: a steam methane reforming process comprising: providing a source gas comprising natural gas into a steam methane reformer to produce a flue gas from which a first carbon-dioxide containing stream is separated and a reformer product stream; capturing carbon dioxide from the reformer product stream to produce a second carbon dioxide-containing stream and a CCh-depleted reformer product stream; introducing the CCh-depleted reformer product stream into a cryogenic separation process to produce a carbon monoxide-containing stream and a CO- depleted reformer product stream; and optionally subjecting the CO-depleted reformer product stream to a pressure-swing adsorption process to adsorb at least a portion of the undesirable components and produce a hydrogen rich product stream and a depleted hydrogen product stream; providing hydrogen gas and an inlet stream comprising one or more of the first carbon dioxide-containing stream, the second carbon dioxide-containing stream, the carbon monoxide-containing stream, or a combination thereof to a methanation unit; methanating the hydrogen gas and the inlet stream in a first location to produce a methanation product stream comprising methane; transporting the methanation product stream to a second location; and converting the methanation product stream at a second location to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide.

13. The process of claim 11 or 12, wherein the first carbon dioxide-containing stream and / or second carbon dioxide-containing stream further comprise carbon monoxide.

14. The process of any one of claims 11 to 13, wherein methanating the hydrogen gas and the inlet stream further produces water;wherein the water is subjected to an electrolysis process to produce at least a portion of the hydrogen gas provided to the methanation unit or is directed to the steam methane reforming process.

15. The process of any one of claims 11 to 14, wherein the conversion process comprises steam methane reforming (SMR), auto-thermal reforming (ATR), or partial oxidation (POx).

16. A process for transporting gas, comprising: an autothermal reforming process comprising: contacting a source gas comprising natural gas, a source of steam, and a source of oxygen in an autothermal reformer to produce a reformer product stream; subjecting the reformer product stream to a water-gas shift reaction to produce a water-gas shift product stream; the water-gas shift reaction comprising reacting the carbon monoxide from the reformer product stream with water to produce carbon dioxide and hydrogen; removing carbon dioxide from the water-gas shift product stream to produce a CCh-depleted stream and a second carbon dioxide-containing stream; and optionally subjecting the C Ch-depleted stream to a pressure-swing adsorption process to adsorb at least a portion of the undesirable components and produce a hydrogen depleted product stream and a hydrogen rich product stream; wherein the autothermal reforming process optionally comprises heating the source gas comprising natural gas in a pre-heater to produce a flue gas from which a first carbon-dioxide containing stream is separated; providing hydrogen gas and an inlet stream comprising one or more of the first carbon dioxide-containing stream, the second carbon dioxide-containing stream, or a combination thereof to a methanation unit; methanating the hydrogen gas and the inlet stream in a first location to produce a methanation product stream comprising methane; transporting the methanation product stream to a second location; andconverting the methanation product stream at a second location to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide.

17. A process for transporting gas, comprising: an autothermal reforming process comprising: contacting a source gas comprising natural gas, a source of steam, and a source of oxygen in an autothermal reformer to produce a reformer product stream; capturing carbon dioxide from the reformer product stream to produce a second carbon dioxide-containing stream and a CCh-depleted reformer product stream; introducing the CCh-depleted reformer product stream into a cryogenic separation process to produce a carbon monoxide-containing stream and a CO- depleted reformer product stream; and optionally subjecting the CO-depleted reformer stream to a pressureswing adsorption process to adsorb at least a portion of the undesirable components and produce a hydrogen depleted product stream and a hydrogen rich product stream; wherein the autothermal reforming process optionally comprises heating the source gas comprising natural gas in a pre-heater to produce a flue gas from which a first carbon-dioxide containing stream is separated; providing hydrogen gas and an inlet stream comprising at least a portion of the first carbon dioxide-containing stream, the second carbon dioxide-containing stream, the carbon monoxide-containing stream, or a combination thereof to a methanation unit; methanating the hydrogen gas and the inlet stream in a first location to produce a methanation product stream comprising methane; transporting the methanation product stream to a second location; and converting the methanation product stream at a second location to produce a first product stream comprising hydrogen and a second product stream comprising carbon dioxide.

18. The process of claim 16 or 17, wherein the first carbon dioxide-containing stream and / or second carbon dioxide-containing stream further comprise carbon monoxide.

19. The process of any one of claims 16 to 18, wherein methanating the hydrogen gas and the inlet stream further produces water; wherein the water is recovered and purified and then subjected to an electrolysis process to produce at least a portion of the hydrogen gas provided to the methanation unit or is directed to the autothermal reforming process.

20. The process of any one of claims 16 to 19, wherein the conversion process comprises steam methane reforming (SMR), auto-thermal reforming (ATR), or partial oxidation (POx).

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