Patent Application
20250066190
The present application relates to a method and system for producing synthesis or reducing gas comprising carbon monoxide (CO) and hydrogen (H2) from various sources of carbon and hydrogen (H2). More particularly, the method for producing synthesis or reducing gas uses at least one first carbon source which is CO2 and at least one second carbon source comprising a hydrocarbon
Gaseous mixtures based on carbon monoxide and hydrogen—commonly known as synthesis or reducing gases—are used in the manufacture of a wide range of basic products such as synthetic liquid hydrocarbons and alcohols. In addition, they can be used in the production of reducing gases in the metallurgical industry (for example, the direct reduction of iron oxides).
To produce such gases, which include carbon monoxide (CO), a source of carbon is required to feed the process. The carbon source can come from fossil resources such as natural gas or coal. Using a carbon source and water vapor, a mixture of carbon monoxide and hydrogen can be produced. Within well-known approaches to accomplish this, natural gas reforming techniques and steam gasification of coal can be mentioned.
The fight against climate change will have to involve, among other things, a substantial reduction in greenhouse gas (GHG) emissions, particularly those of CO2 and methane. At present, considerable efforts are being made to minimize the consumption of fossil resources as a source of energy and also as a basic ingredient in many chemical syntheses. The use of CO2 as a carbon source in the production of synthesis gas is one approach being considered to reduce these GHG emissions.
CO2 is found in the ambient air, but also in atmospheric discharges from industrial processes emitting CO2 (e.g., cement plant, aluminum plant, steel plants, etc.). The process of capturing CO2 from ambient air, from biogenic sources, or released by industrial processes to recycle it for later use is also known as “Carbon Capture Utilization” (CCU). The CO2 thus captured can be used as a carbon source for producing synthesis gas for the production of a wide range of products with improved carbon neutrality, i.e., whose production and use cycle involves low net GHG emissions, when CO2 comes from biogenic sources or ambient air. It is thus possible to produce carbon synthetic fuels that are more carbon-neutral and can be used in existing infrastructures. It is also possible to produce synthesis gases that can be used to formulate reducing gases for the metallurgical industry (e.g., for the direct reduction of metal oxides).
There are several ways to use CO2 as a basic reagent to provide carbon for the production of synthesis gas. The most practical way consists in converting the CO2 into carbon monoxide (CO) according to the reaction (A) called “Reverse Water Gas Shift” or RWGS.
CO2+H2→CO+H2O(vapor) (A)
By reacting CO2 with an excess of hydrogen (H2), mixtures based on hydrogen and CO can be produced.
Catalytic bed reactors are generally used to carry out the RWGS reaction (A). However, the use of conventional catalysts to carry out reaction (A) is not without certain limitations in relation to the desired conversion rate for CO2. Indeed, to obtain high conversion rates, high temperatures are required (e.g., over 1200° C.), but the use of conventional catalysts is problematic at high temperature levels.
Another method for producing synthesis gas is based on the combustion of hydrogen with pure oxygen in the presence of an oxy-flame. The oxy-flame generates heat and water vapor, according to reaction (B).
H2+½O2→H2O(vapor)+HEAT (B)
The water vapor generated by the oxy-flame according to reaction (B) and also by the RWGS reaction (A), during the production of synthesis gas, can be considered as a “loss” of hydrogen and have an impact on operating costs. A method that can take advantage of the water vapor generated, using it to produce synthesis gas, would be desirable.
According to a first aspect, the present technology relates to a method for producing synthesis gas comprising carbon monoxide (CO) and hydrogen (H2), the method comprising:
According to one embodiment, the production of the first gas comprising at least carbon monoxide (CO) and water vapor (H2O), in the first zone, is carried out at a temperature of at least 1000° C. and at most 2400° C.
According to another embodiment, the production of the first gas comprising at least carbon monoxide (CO) and water vapor (H2O), in the first zone, is carried out at a temperature of between about 1000° C. and about 1900° C.
According to another embodiment, generating the synthesis gas, in the second zone, is carried out at a temperature of at least 700° C. and at most 1500° C.
According to another embodiment, generating the synthesis gas, in the second zone, is carried out at a temperature of between about 700° C. and about 1000° C.
According to another embodiment, generating the synthesis gas, in the second zone, is carried out at a temperature lower than a temperature in the first zone.
According to another embodiment, the oxidizing stream is fed into a lower, central part of the first zone and the first reducing stream is fed into the lower part of the first zone at the periphery of the oxidizing stream.
According to another embodiment, the second gas generated in the second zone comprises synthesis gas and residual CO2 and the method further comprises recycling a portion of the second gas to the first zone.
According to another embodiment, a portion of the second gas is recycled in the first reducing stream.
According to another embodiment, the method further comprises cooling the portion of the second gas to be recycled, prior to recycling.
According to another embodiment, the method is carried out in a plurality of reactors in parallel, each reactor having the first zone which receives the oxidizing stream and the first reducing stream and where the first gas is produced, and the second zone which receives the second reducing stream and where the second gas is generated.
According to a further embodiment, the reactor comprises a plurality of first zones and a shared second zone, and wherein:
According to another aspect, the present technology relates to a system for producing a synthesis gas comprising carbon monoxide (CO) and hydrogen (H2), the system comprising at least one reactor and said reactor comprising at least one first reaction zone and at least one second reaction zone, wherein:
According to one embodiment, the first zone is at a temperature of at least 1000° C. and at most 2400° C. during the production of the first gas comprising at least carbon monoxide (CO) and water vapor (H2O).
According to another embodiment, the first zone is at a temperature between about 1000° C. and about 1900° C. during the production of the first gas comprising at least carbon monoxide (CO) and water vapor (H2O).
According to another embodiment, the second zone is at a temperature of at least 700° C. and at most 1500° C. during the production of the synthesis gas.
According to another embodiment, the second zone is at a temperature between about 700° C. and about 1000° C. during the production of the synthesis gas.
According to another embodiment, generating the synthesis gas, in the second zone, is carried out at a temperature lower than a temperature in the first zone.
According to another embodiment, the second gas generated in the second zone comprises the synthesis gas and residual CO2 and the system further comprises means for recycling a portion of the second gas to the first zone.
According to another embodiment, the means for recycling comprises a duct conveying the portion of the second gas to be mixed with the first reducing stream.
According to another embodiment, the system further comprises a device for cooling the portion of the second gas to be recycled, prior to recycling.
According to another embodiment, the first zone and the second zone are each of cylindrical shape.
According to another embodiment, the system comprises a first means for feeding the oxidizing stream into a lower, central part of the first zone and a second means for feeding the first reducing stream into the lower part of the first zone at the periphery of the oxidizing stream.
According to another embodiment, the first means consists of a first central tube and the second means consists of an annular space extending perpendicularly between an outer wall of the central tube and an inner wall of the first zone.
According to another embodiment, the system comprises a third means for feeding the second reducing stream in the second zone.
According to another embodiment, the first zone and the second zone are each cylindrical in shape and the third means consists of an opening formed by an annular space extending between an outer wall of the first zone and an inner wall of the second zone, optionally in an upper region of the first zone and a lower region of the second zone.
According to another embodiment, the system comprises a plurality of reactors in parallel, each reactor having the first zone receiving the oxidizing stream and the first reducing stream and where the first gas is produced, and the second zone receiving the second reducing stream and where the second gas is generated.
According to another embodiment, the reactor comprises a plurality of first zones and a shared second zone, and wherein:
According to some aspects, the method and/or system according to the present technology may comprise the following embodiments.
According to one embodiment, the oxidizing stream comprises oxygen and CO2.
According to another embodiment, the first reducing stream comprises hydrogen (H2) and CO2, and optionally water vapor in a H2O/H2 ratio from 0 to 1, preferably in a H2O/H2 ratio from 0 to 0.5.
According to another embodiment, the oxidizing stream and the first reducing stream each comprise CO2.
According to another embodiment, only the oxidizing stream comprises CO2.
According to another embodiment, the CO2 comes from an industrial waste, is biogenic CO2 from biogas, is CO2 captured directly from ambient air or a mixture thereof.
According to another embodiment, the hydrogen present in the first reducing stream results from a water electrolysis reaction.
According to another embodiment, the hydrogen present in the first reducing stream results from a water electrolysis reaction in an electrolyzer which is powered by electricity produced from a renewable source (e.g. produced from solar energy, wind energy, hydraulic energy, biomass or geothermal energy) or nuclear energy.
According to another embodiment, the hydrogen present in the first reducing stream results from a steam reforming reaction of natural gas or methane in a process in which the CO2 generated is at least partly captured and sequestered.
According to another embodiment, the hydrogen present in the first reducing stream comprises hydrogen resulting from a water electrolysis reaction in an electrolyzer which is powered by electricity produced from a renewable source (e.g., produced from solar energy, wind energy, hydraulic energy, biomass or geothermal energy) or nuclear energy, and hydrogen resulting from a steam reforming reaction of natural gas or methane in a process for which the CO2 generated is at least partly captured and sequestered.
According to another embodiment, the hydrogen present in the first reducing stream further comprises hydrogen resulting from a methane pyrolysis reaction.
According to another embodiment, the hydrogen, oxygen and CO2 are fed in the first zone in a H2/O2 molar ratio of at least 2, and a H2/CO2 molar ratio of least 1.8.
According to another embodiment, the hydrogen, oxygen and CO2 are fed in the first zone in a H2/O2 molar ratio of between 2 and 10, and a H2/CO2 molar ratio of between 1.8 and 9.
According to another embodiment, the oxygen and CO2 are fed in the first zone in a O2/CO2 molar ratio of at least 0.5.
According to another embodiment, the oxygen and CO2 are fed in the first zone in a O2/CO2 molar ratio of between 0.5 and 6.
According to another embodiment, generation of the synthesis gas comprises steam reforming the hydrocarbon(s) with the water vapor comprised in the first gas.
According to another embodiment, the second reducing stream further comprises water vapor and the generation of the synthesis gas comprises steam reforming of the hydrocarbon(s) with the water vapor comprised in the first gas and the water vapor comprised in the second reducing stream.
According to another embodiment, the second carbon source comprises a fossil or renewable hydrocarbon.
According to another embodiment, the second carbon source comprises fossil or renewable natural gas.
According to another embodiment, the second carbon source comprises methane.
According to another embodiment, the second carbon source comprises methane from biogas.
According to another embodiment, the second reducing stream further comprises an organic compound derived from biomass.
According to another embodiment, the second reducing stream further comprises a compound of formula CαHβOγ with α varying from 1 to 5, β varying from 2 to 10 and γ varying from 1 to 4.
According to another embodiment, the second reducing stream comprises methane (CH4) and optionally hydrogen (H2) in a H2/CH4 molar ratio of between 0 and 2.5.
According to another embodiment, the second reducing stream comprises methane (CH4) and optionally hydrogen (H2) and a molar ratio between the CH4 fed and a total amount of H2 fed in the two zones is between 0.1 and 1.
According to another embodiment, the second reducing stream further comprises hydrogen (H2).
According to another embodiment, the hydrogen present in the second reducing stream results from a steam reforming reaction of natural gas or methane in a process in which the CO2 generated is at least partly captured and sequestered.
According to another embodiment, the second reducing stream comprises a quantity of hydrogen to balance the molar composition of the synthesis gas to have H2/CO≥2 and (H2—CO2)/(CO+CO2)≥2.
According to another embodiment, the second reducing stream comprises methane (CH4) and optionally water vapor (H2O), and a molar ratio of water vapor (H2O) to CH4 is between 0 and 2.
According to another embodiment, the second reducing stream further comprises water vapor.
According to a further embodiment, the production of carbon monoxide and water vapor in the first zone is carried out in the absence of a catalyst.
According to another embodiment, the generation of the second gas comprising the synthesis gas in the second zone of the reactor is carried out in the absence of a catalyst.
According to another embodiment, the oxygen (O2) present in the oxidizing stream results from a water electrolysis reaction.
According to another embodiment, the oxygen (O2) present in the oxidizing stream comes from an air separation unit (ASU).
According to a further aspect, the present technology relates to the use of a synthesis gas produced by the method as defined in the present description or by the system as defined in the present description, for the manufacture of chemical products or fuels.
According to one embodiment, the use enables the manufacture of synthetic hydrocarbons.
According to yet another aspect, the present technology relates to the use of a synthesis gas produced by the method as defined in the present description or by the system as defined in the present description, as a reducing agent for the metallurgical industry.
According to yet another aspect, the present technology relates to the use of a system as defined in the present description for the treatment of gaseous industrial effluents containing CO2.
All technical and scientific terms and expressions used herein have the same meanings as those generally understood by the person skilled in the art of the present technology. The definition of certain terms and expressions used are nevertheless provided below.
The term “about” as used in the present document means approximately, in the region of, and around. When the term “about” is used in connection with a numerical value, it modifies it, for example, above and below by a variation of 10% compared to the nominal value. This term can also take into account, for instance, the experimental error of a measuring device or the rounding of a value.
When an interval of values is mentioned in the present application, the lower and upper limits of the interval are, unless otherwise indicated, always included in the definition.
In the present description, the terms “synthesis gas”, “reducing gas” and “syngas” are used interchangeably to identify a gas mixture comprising at least carbon monoxide (CO) and hydrogen (H2). In some embodiments, the synthesis gas, reducing gas or syngas may comprise CO2.
The term “stream” is used to describe the different gas streams involved in the production of the synthesis gas in the different zones inside the reactor.
The term “carbon source” describes the chemical compound(s) that are used to provide the carbon that ends up in the synthesis gas produced. Thus, the carbon source provides at least the carbon that ends up in the carbon monoxide (CO) being produced. Different chemical compounds can be used as carbon source. The present method uses at least CO2 and at least one hydrocarbon (i.e., a compound based essentially on carbon and hydrogen) as the carbon source to produce the synthesis gas. According to some embodiments, the hydrocarbon used as one of the carbon sources is methane (CH4) or fossil or renewable natural gas (RNG). According to some embodiments, other carbon sources such as organic compounds comprising carbon, hydrogen and oxygen may be used, as will be explained below.
The expressions “electricity from renewable sources” or “electricity produced from renewable sources” refer to electricity produced from solar energy, wind energy, hydraulic energy, biomass or geothermal energy.
The expression “fossil natural gas” as used in this description refers to a mixture of gaseous hydrocarbons (essentially methane) resulting from the natural transformation of organic matter from underground deposits.
The expression “renewable natural gas” (RNG) as used in this description refers to a gaseous fuel also known as biomethane or first-generation RNG, which can generally contain between 55 and 99% methane, produced from biogas resulting from the anaerobic digestion of organic matter.
This document therefore presents an innovative method for producing synthesis gas using at least CO2 as carbon source and involving an oxy-flame generated by reaction between oxygen and hydrogen. More specifically, the method of producing synthesis gas comprises: feeding an oxidizing stream comprising oxygen (O2) and a first reducing stream comprising hydrogen into at least a first reaction zone of at least one reactor, wherein the oxidizing stream and/or the first reducing stream further comprises a first carbon source which is CO2; generating an oxy-flame in the first zone by reaction between the oxygen in the oxidizing stream and the hydrogen in the first reducing stream, and producing a first gas comprising at least carbon monoxide (CO) and water vapor (H2O) by bringing the oxidizing stream and the first reducing stream into contact with the oxy-flame; feeding the reactor with a second reducing stream comprising a second carbon source comprising at least one hydrocarbon; and generating in a second zone of the reactor a second gas comprising the synthesis gas, from the first gas coming from the first zone and the second reducing stream by means of a reaction involving the hydrocarbon.
As mentioned above, the method uses at least CO2 as carbon source to produce the synthesis gas. The CO2 can have various origins. Hence, the method may use CO2 from industrial waste, biogenic CO2 from biogas, or CO2 captured directly from ambient air, e.g., by the Direct Air Capture (DAC) process. In some embodiments, the carbon source comprises CO2 captured from ambient air or CO2 from biomass, in which case the carbon is referred to as “carbon neutral” or “biogenic”.
In the first reaction zone 12, the oxy-flame 22 is produced by the combustion of hydrogen (H2) from the first reducing stream 18 in the presence of oxygen (O2) from the oxidizing stream 16 according to the aforementioned reaction (B). This flame is bright and radiant and provides the heat required to sustain the reaction which will produce a first gas comprising carbon monoxide (CO) produced from the first carbon source comprising at least CO2, and also comprising water vapor, according to reaction (A) of the RWGS. Thus, the first gas comprising at least carbon monoxide (CO) and water vapor (H2O) is obtained by “contacting” the oxidizing stream and the first reducing stream with the oxy-flame. The expression “contacting” according to the present method is understood to mean a distance “d” between the oxidizing stream and the reducing stream which can range from 0 to 50 mm, and preferably from 0 to 30 mm. The distance “d” between the oxidizing stream and the reducing stream in can be 0 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm or any value in between. For example, the distance “d” may be from 0 to 50 mm, from 0 to 40 mm, from 0 to 30 mm, from 0 to 20 mm, or from 0 to 10 mm. In addition, the oxy-flame can generate ionic species and free radicals which can promote the conversion of the carbon source to CO. Thus, it should also be noted that the production of carbon monoxide and water vapor in the first reaction zone 12 can be achieved in the absence of a catalyst such as conventionally used solid catalysts. The combustion of hydrogen (H2) in the presence of oxygen (O2) to produce the oxy-flame may be initiated by an ignition device. According to some embodiments, the oxy-flame may make it possible to reach a temperature, in the first reaction zone, of at least 600° C. According to other embodiments, the temperature reached in the first zone 12 is of at least 1000° C. and at most 2400° C. According to some embodiments, the reactor may be equipped with thermal insulation around the reaction zones to minimize heat loss and thus maintain the temperature in the reactor high enough to support the reactions. According to some embodiments, the production of the first gas comprising at least carbon monoxide (CO) and water vapor (H2O) in the first zone 12 may be carried out at a temperature of between about 1000° C. and about 2300° C., or between about 1000° C. and about 2200° C., or between about 1000° C. and about 2100° C., or between about 1000° C. and about 2000° C., or between about 1000° C. and about 1900° C. The temperature in the first zone 12 may also vary between about 1000° C. and about 1800° C., between about 1000° C. and about 1700° C., between about 1000° C. and about 1600° C., or between about 1000° C. and about 1500° C. In some embodiments, as shown in
In some embodiments, the first carbon source, which comprises CO2, is fed to the first zone of the reactor with the oxygen from the oxidizing stream. In another embodiment, the first carbon source, which comprises CO2, is fed to the first zone of the reactor with the hydrogen from the first reducing stream. In some cases, a portion of the first carbon source, which comprises CO2, is fed to the first zone of the reactor with the oxygen from the oxidizing stream and another portion of the first carbon source is fed to the first zone of the reactor with the hydrogen from the first reducing stream. In a preferred embodiment, the first carbon source, which comprises CO2, is fed to the first zone only with the oxygen from the oxidizing stream.
As previously mentioned, CO2 may come from various origins. In some embodiments, the CO2 comes from industrial waste, is biogenic CO2 from a biogas, or is CO2 captured directly from ambient air. In some preferred embodiments, the CO2 used as the first carbon source is biogenic CO2 from a biogas.
According to an embodiment, the hydrogen required in the present method may be hydrogen qualified as low carbon footprint hydrogen. According to one embodiment, the hydrogen required in the present method to produce the oxy-flame in the first zone, i.e., the hydrogen present in the first reducing stream 18, may, at least in part, result from a water electrolysis reaction. This hydrogen is called “green hydrogen” if the electrolyzer in which electrolysis of the water is carried out is powered by electricity produced from a renewable source, such as solar energy, wind energy, hydraulic energy, biomass or geothermal energy. In some embodiments, the electricity used for the electrolysis of water may be derived from nuclear energy, which is an energy source that does not emit greenhouse gases, and this hydrogen may also be referred to as “pink hydrogen” in the context of the present technology.
According to another embodiment, the hydrogen present in the first reducing stream 18 fed to the first zone of the reactor may be “blue hydrogen”, i.e., hydrogen resulting from a steam reforming reaction of natural gas or methane in a process in which the CO2 generated is at least partially captured and sequestered.
According to yet another embodiment, the hydrogen present in the first reducing stream 18 fed to the first zone of the reactor may be “turquoise hydrogen”, i.e., hydrogen resulting from a methane pyrolysis reaction.
According to yet another embodiment, the hydrogen present in the first reducing stream 18 fed to the first zone of the reactor may be “pink hydrogen”, i.e., hydrogen resulting from a water electrolysis reaction powered by nuclear energy.
It is also possible to use mixtures of hydrogen from various sources to feed the first zone, to produce the oxy-flame and to form the first gas comprising carbon monoxide (CO) and water vapor (H2O). Thus, in some embodiments, the first reducing stream 18 may comprise a mixture of green hydrogen and blue hydrogen, or a mixture of green hydrogen and turquoise hydrogen, a mixture of blue hydrogen and turquoise hydrogen, a mixture of green hydrogen, blue hydrogen and turquoise hydrogen.
In some embodiments, the quantities of hydrogen supplied to the first zone 12 (e.g., green, blue, pink and/or turquoise hydrogen) are metered so as to reduce operating costs as much as possible while ensuring that, at the reactor outlet, the molar composition of the synthesis gas satisfies the following equations (C) and (D):
H2/CO≥2 (C)
(H2—CO2)/(CO+CO2)≥2 (D)
These equations also take into account the fact that additional hydrogen can be introduced into the second zone 14 of the reactor via the stream 24, as will be discussed below, to balance the composition of the synthesis gas.
In particular embodiments, hydrogen, oxygen and CO2 are supplied to the first zone 12 in a H2/O2 molar ratio of at least 2, and a H2/CO2 molar ratio of at least 1.8. According to another embodiment, hydrogen, oxygen and CO2 may be fed into the first zone in a H2/O2 molar ratio of between 2 and 10, and a H2/CO2 molar ratio of between 1.8 and 9. Thus, hydrogen and oxygen can be fed into the first zone 12 with a H2/O2 molar ratio of about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, or about 10, or any value in between. In addition, the quantity of hydrogen and the quantity of CO2 fed into the first zone can be adjusted so that the H2/CO2 molar ratio is about 1.8, or about 2, or about 3, or about 4, or about 5, or about 6, or about 7, or about 8, or about 9, or any value between these values. According to some embodiments, oxygen and CO2 can be supplied to the first zone in an O2/CO2 molar ratio of at least 0.5. For example, oxygen and CO2 may be supplied to the first zone in an O2/CO2 molar ratio of between 0.5 and 6. Thus, the quantity of oxygen and the quantity of CO2 fed to the first zone can be adjusted so that the O2/CO2 molar ratio is about 0.5, or about 1, or about 2, or about 3, or about 4, or about 6, or any value in between these values. The H2/O2, H2/O2 and O2/CO2 molar ratios may be adjusted according to the quantity of other gases supplied to the reactor, if any, and according to the desired ratio of CO and H2 in the final synthesis gas.
It should be noted that in some embodiments, the oxidizing stream 16 and/or the reducing stream 18 may contain, in addition to the inputs described above, a certain quantity of impurities and water vapor. According to some embodiments, the reducing stream 18 may contain water vapor up to a H2O/H2 molar ratio of 0.5.
Again, referring to
The second reaction zone receives the gas formed in the first reaction zone which comprises at least CO and water vapor generated by reactions (A) and (B) and possibly some residual CO2 and/or hydrogen H2. This second reaction zone 14 is further fed by a second reducing stream 24 comprising a second carbon source comprising at least one hydrocarbon. In addition, the reducing stream 24 may comprise water vapor. After reaction of the second reducing stream with the first gas in the second reaction zone of the reactor, a second gas 26 comprising the synthesis gas is recovered at the outlet of the reactor 28.
The second reducing stream 24 comprises at least one hydrocarbon as a second carbon source, and the generation of the synthesis gas, in the second reaction zone 14, is carried out in part by steam reforming of the hydrocarbon(s) with the water vapor included in the first gas and/or any water vapor present in the reducing stream 24 as mentioned above. This carbon source can be a fossil or renewable hydrocarbon, preferably methane or fossil or renewable natural gas (RNG). In some embodiments, the second carbon source is methane derived from biogas. In the case where a hydrocarbon which is methane is used, reaction (E), and reaction (F) in the presence of residual CO2, occur in the second zone 14.
CH4+H2O→CO+3H2 (E)
CH4+CO2→2 CO+2H2 (F)
By steam reforming of the hydrocarbon(s) fed into the second zone, a synthesis gas meeting the criteria presented by equations (C) and (D) can be obtained.
As explained above, hydrogen may also be supplied to the second zone 14 to produce the synthesis gas. When additional hydrogen is supplied to zone 14 by the reducing stream 24, on one hand the composition of the synthesis gas can be balanced in order to comply with equations (C) and (D) as mentioned above, and, on the other hand, water vapor and residual CO2 can be reduced in this zone.
In addition, the molar proportions of CO and H2 in the synthesis gas can also be varied by supplying the second zone 14 with both one or more hydrocarbons and hydrogen.
According to some embodiments, the hydrogen which is fed via the second reducing stream 24 in the second zone 14 may be blue hydrogen as described above, i.e., hydrogen resulting from a steam reforming reaction of natural gas or methane in a process for which the CO2 generated is at least partly captured and sequestered.
According to some embodiments, the second reducing stream 24 may comprise methane (CH4) and optionally hydrogen (H2) in a H2/CH4 molar ratio of between 0 and 2.5.
According to another embodiment, the second zone can be supplied with a second reducing stream 24 comprising methane (CH4) and optionally hydrogen (H2), such that the molar ratio between the CH4 supplied and a total quantity of H2 supplied in the two zones is between 0.1 and 1.
It should be noted that in some embodiments, the second reducing stream 24 may contain, in addition to the inputs described above, water vapor and a small quantity of impurities.
According to some embodiments, the reducing stream 24 fed into the second zone 14 may comprise methane (CH4) and optionally water vapor (H2O) with a molar ratio of water vapor (H2O) to CH4 which may be between 0 and 2.
According to some embodiments, the reducing stream 24 fed into the second zone 14 may further comprise organic compounds derived from biomass, i.e., comprising biogenic carbon. These organic compounds comprising biogenic carbon may have the formula CαHβOγ with α varying from 1 to 5, β varying from 2 to 10, and γ varying from 1 to 4.
According to some embodiments, the reaction in the second zone 14 of the reactor is carried out at a temperature which is lower than the temperature in the first zone 12. In some embodiments, the synthesis gas can be generated in the second zone 12 at a temperature of at least 700° C. and at most 1500° C. In some cases, the temperature in the second reaction zone may be between about 700° C. and about 1000° C. Thus, the temperature in the second reaction zone can also be between about 700° C. and about 1400° C., between about 700° C. and about 1300° C., between about 700° C. and about 1200° C., between about 700° C. and about 1100° C., between about 700° C. and about 1000° C., between about 700° C. and about 900° C., or between about 700° C. and about 800° C. It is possible to achieve a lower temperature in the second zone 14 in various ways, for example by adjusting the insulation and/or the heating or cooling system of the reactor. In some embodiments, the desired temperature can be achieved in the second reaction zone 14 by using a wall that is less insulated than, for example, the reactor wall in the first zone. It is also possible, in some cases, to use a cooling system to achieve the desired temperature in the second zone of the reactor.
According to some embodiments, the production of synthesis gas in the second zone 14 of the reactor can be carried out in the absence of catalysts such as solid catalysts (e.g., metal catalysts) as conventionally used.
With the use of the second reaction zone 14, the quantity of water vapor resulting from the reaction taking place in the first zone 12 and the quantity of water vapor optionally present in the stream 24 fed into this second zone are substantially reduced. This is an important advantage. In addition, in some embodiments, if CO2 remains in zone 14 as a result of the reactions occurring therein, and it is preferable to reduce it further, a return loop 30 as shown in
According to a particular embodiment, the production of synthesis gas according to the present method may comprise feeding, into the first zone 12, an oxidizing stream 16 comprising oxygen and a renewable carbon source and a first reducing stream 18 comprising green hydrogen, and, in the second zone 14, feeding blue hydrogen and a fossil carbon source. If the renewable carbon source is CO2 and the fossil carbon source is methane, the reactions involved can enable the production synthesis gas efficiently and at low cost. Equation (G) below shows a typical overall reaction scheme that can be achieved:
½O2+H2(green)+CO2(renewable)+2CH4(fossil)+H2(blue)→3(CO+2H2) (G)
Considering that, although the method can use fossil carbon sources as inputs, it also uses CO2 as an input, the net GHG emissions from the reactor can be zero or very close to zero; this method can be considered as a carbon capture and utilization (CCU) method.
A schematic representation of a reactor that can be used to implement the present method is shown in
In some embodiments, a cylindrically shaped reactor may be used which comprises two reaction zones, as described above. In some embodiments, each of the two zones may itself be cylindrical.
Reactor 10 may comprise a first means for feeding the oxidizing stream 16 into a lower, central part of the first zone 12 and a second means for feeding the first reducing stream 18 into the lower part of the first zone at the periphery of the oxidizing stream. In some embodiments, the reactor may comprise a first central tube through which the oxidizing stream 16 is fed into the first zone 12 and an annular space extending perpendicularly between an outer wall of the central tube and an inner wall of the first zone 12 for feeding the first reducing stream 18. In addition, the reactor may comprise a third means for feeding the second reducing stream 24 into the second zone 14. In some embodiments, this third means may consist of an opening formed by an annular space extending between an outer wall of the first zone 12 and an inner wall of the second zone 14. According to some embodiments, the annular space through which the second reducing stream 24 is fed into the reactor may extend between the outer wall of the first zone 12 and the inner wall of the second zone 14 in an upper region of the first zone and a lower region of the second zone. In some embodiments, the inlets to each of the streams 16, 18 and 24 may be at the same level as shown in
According to another embodiment, the production of the synthesis gas can be carried out using a plurality of reactors positioned in parallel, as shown in
According to yet another embodiment, the production of synthesis gas can be carried out using a reactor comprising a plurality of first zones 12 and a shared second zone 14 (
The synthesis gas obtained from the reactor outlet is generally cooled and then used in a subsequent chemical synthesis. The method described herein can produce synthesis gases based on CO and H2 that are balanced, i.e., with appropriate proportions of CO and H2, to then allow the production of a variety of products by conventional chemical syntheses. Thus, by controlling the nature and quantity of the reagents used (e.g., the flow rate of the gas streams), it is possible to produce a synthesis gas in which the proportion of CO and H2 is adapted so that the mixture can be used in a subsequent chemical synthesis. It is also possible to influence the proportion of CO and H2 in the synthesis gas by controlling the temperature and eventually the pressure in each reaction zone of the reactor. This pressure is generally around atmospheric pressure and can typically vary between 1 and 5 bars (absolute pressure), for each zone. According to some embodiments, the absolute pressure in the first zone may range from 1 to 5 bars, or from 1 to 4 bars, or from 1 to 3 bars, or from 1 to 2 bars. The absolute pressure in the first zone may be about 1 bar, about 2 bars, about 3 bar, about 4 bar, about 5 bars, or any pressure value in between these values. According to some embodiments, the absolute pressure in the second zone may be from 1 to 5 bars, or from 1 to 4 bars, or from 1 to 3 bars, or from 1 to 2 bars. The absolute pressure in the second zone may be about 1 bar, about 2 bars, about 3 bars, about 4 bars, about 5 bars, or any pressure value between these values. In some embodiments, the pressure in the first zone and the pressure in the second zone are very close or even the same.
In some embodiments, the synthesis gas produced by the present method can be used to produce a large number of basic chemical products and fuels. These products include methanol and hydrocarbons such as those found in motor gasoline, diesel, kerosene, to name a few examples. In some embodiments, the synthesis gas produced by the present method is used as a reducing agent for the metallurgical industry, inter alia, for the direct reduction of metal oxides, in particular iron oxides.
The synthesis gas production method described above and the reactor that can be used to carry out this method therefore have several advantages. The reagents are readily available and can be derived from renewable sources and the method is simple to implement. There is no need to use solid catalysts. It is possible to use hydrogen from a variety of sources and it is therefore possible to reduce costs by using hydrogen produced at lower cost. It is possible to use hydrogen with a low carbon footprint (e.g. green, blue, turquoise and/or pink hydrogen). So, if green hydrogen is produced at a higher cost than blue hydrogen, for example, the amount of green hydrogen used in the method can be reduced by using blue hydrogen in addition to green hydrogen, or simply by using only blue hydrogen. The method also takes advantage of the water vapor generated during CO2 reduction, using it to produce the synthesis gas. This avoids the need to condense a large quantity of water, as is the case with other known methods, and avoids an indirect loss of hydrogen via the water vapor. The method has a beneficial environmental effect by recycling CO2 while allowing the efficient conversion of other carbon sources such as fossil hydrocarbons, such as methane. Finally, the method provides a significant overall conversion of the carbon entering the reactor into CO, while being flexible through the relative and in situ conversions of CO2 and hydrocarbon(s).
As examples, laboratory tests have been carried out to demonstrate the concept proposed in this application. These examples are based on a set-up similar to that shown in
The reactor consists of an external alumina tube (99.8% Al2O3) with an internal diameter of 13.54 mm and an external diameter of 19.05 mm over a length of 212 mm. The reaction volume is 33 cm3. The gases enter through three spaces, a central space and two annular spaces defined by the ends of two concentric alumina tubes: a central tube and a medial tube. These two concentric tubes have the following dimensions respectively: an internal diameter of 6.31 mm with an external diameter of 4.11 mm for the central tube, and an internal diameter of 8.48 mm with an external diameter of 12.34 mm for the medial tube. The end of the central tube defines the path of the oxidizing stream 16 of the first zone of the reactor, while the annular space between the external diameter of the central tube and the internal diameter of the medial tube defines the path of the reducing stream 18 of the first reaction zone. Finally, the annular space between the inner diameter of the outer tube and the outer diameter of the medial tube defines the path of the second reducing stream of the second reaction zone 24.
The outer alumina tube, which defines the wall of the reaction chamber, is itself surrounded—along the entire length of the reactor—by a calcium silicate-based insulating jacket (thermal conductivity 0.3 W/m·K, density 1.36 g/cm3) of cylindrical shape with an external diameter of 132 mm and an internal diameter of 20 mm (not shown in
In each of these examples, oxygen is mixed with CO2 and this mixture forms the oxidizing stream 16 of the first reaction zone. In the examples, the fed hydrogen forms the reducing stream 18 of the first zone. In the first and third examples, methane is fed to form the reducing stream 24 of the second zone, whereas in the second example, a mixture of methane and water vapor forms the reducing stream 24 of the second zone. The methane-water vapor mixture is produced by a device for hot saturation of the methane flow in the presence of a controlled flow of water.
Each of the examples is shown in Table 1. In this table, for each of the gases supplied, the number of the gas stream in question (16, 18 or 24) is given in brackets, alongside the volume flow rate of that gas (sL/min, i.e., the flow rate at 25° C., 1 atm). A sample of the gas leaving the reactor is dried by rapid cooling (to −1° C.) before being sent to a mass spectrometry analysis system. Gas analysis is therefore performed on a dry basis.
The table shows the analysis of the gas leaving the reactor as determined by mass spectrometry. From the volume composition of the gas, the ratio S equal to (H2—CO2)/(CO+CO2) is calculated based on the respective volume fraction of each of the gases H2, CO2 and CO in the dry gas obtained. The methane and CO2 conversion rates are calculated from atomic balances and from the composition of the gas (dry basis) as obtained from gas analysis by mass spectrometry. The table also shows the rate of conversion to CO of the total carbon entering the reactor, i.e., the carbon contained in the CO2 fed plus the carbon contained in the CH4 fed.
The table also shows the temperature as measured using a thermocouple located 25 mm from reactor outlet 28. The measured temperature value is used to calculate the average residence time of the reactants (i.e., all the gases fed) in the reactor, based on the reaction volume as described above and considering that the reactor is operating at atmospheric pressure.
It should be noted that no measurable quantities of carbon were observed in the reactor after the tests.
Table 1 presents the results obtained for each of the two examples.
The results of examples 1, 2 and 3, as shown in Table 1, demonstrate the flexibility of the method and system according to the present description. This flexibility results essentially from the geometric distinction of the reactive zones in the reactor. In particular, the configuration used in these examples (see
The results of examples 1 and 2 show that the supply of water vapor is not critical for achieving high methane conversion. In fact, adding water to the second zone only slightly increases the conversion of methane (from 79% to 83%) (by reaction (E)) but leads to a reduction in the conversion of CO2, probably by favouring the reverse of reaction (A). The results of example 3 show that a high and equivalent conversion of CH4 and CO2 can be achieved by adding a certain amount of excess hydrogen in the first zone (9 vs. 6 sL/min). Indeed, this excess hydrogen seems to help convert CO2 more efficiently in the first zone by reaction (A)). In this same example 3, it is observed that the conversion of CH4 is not significantly affected by the increase in the conversion of CO2 due to the fact that this CH4 is fed separately into the second zone.
Although some embodiments of the technology have been described above, the technology is not limited to these sole embodiments. Several modifications could be made to any of the embodiments described above without departing from the scope of the present technology as contemplated.
| Number | Date | Country | Kind |
|---|---|---|---|
| 3154398 | Apr 2022 | CA | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2023/050479 | 4/6/2023 | WO |
