METHOD FOR QUANTIFYING THE NATURAL HYDROGEN GENERATION POTENTIAL FROM ROCK SAMPLES

Abstract

The invention relates, on the one hand, to a method for automatically quantifying the dihydrogen generated by a sample of mineral or sedimentary source rock containing a metallic compound (such as iron), characterized in that a water reduction reaction is carried out in the presence of said sample and water vapor at a temperature of approximately 1200°C and the quantity of said dihydrogen generated by said sample during this reaction is determined with a view to qualifying said source rock as a potential source of natural hydrogen and, on the other hand, to a device for implementing said method. Abstract figure (Figure 1)

Description

Title of the invention: METHOD FOR QUANTIFYING THE POTENTIAL FOR THE GENERATION OF NATURAL HYDROGEN FROM ROCK SAMPLE

[0001] The present invention relates to a method and a device for continuous analysis of a hydrogen flow generated by chemical interaction between a water-laden carrier gas and a mineral rock sample.

[0002] In general, the invention aims to determine the quantity of hydrogen generated by a rock sample during a water reduction reaction at high temperature and in the presence of this sample. The invention also aims to analyze the kinetics of the reduction reaction as a function of the temperature and the quantity of water.

[0003] Due to the decline in hydrocarbon resources and growing global energy needs, and the search for a less carbon-intensive energy mix, the production of hydrogen worldwide and its use have become major issues.

[0004] Besides being a raw material for the chemical industry, particularly for the manufacture of fertilizers, hydrogen is a fuel. The low greenhouse gas emissions produced by the combustion of hydrogen make it a good candidate as an environmentally friendly resource in a context of global warming.

[0005] However, current hydrogen production remains highly dependent on fossil fuels. In fact, approximately 60% of the hydrogen produced comes from the high-temperature steam reforming of methane (or natural gas), itself most often produced using fossil fuels. Approximately 20% comes from coal gasification and the rest from liquid HC. Less than 5% comes from electrolysis, a process that requires a lot of electrical energy, even though this is most often produced by hydrocarbon or coal-fired thermal power plants.

[0006] The main problem posed by hydrogen as a clean energy, or raw material, is therefore its production. From then on, the exploration of sources of natural hydrogen takes on its full meaning. Although still in the prospective state, the understanding of natural systems for generating di-hydrogen should allow in the future to exploit this natural hydrogen without resorting to fossil fuels. It is in this context that the invention provides solutions for simulating in the laboratory the natural conditions for the production of hydrogen in geological layers.

[0007] The applications targeted by the invention are mainly located in the field of exploration of natural hydrogen sources throughout the world. More precisely, The invention is primarily (but not exclusively) concerned with a particular mode of hydrogen generation from mineral rocks. This mode of generation results from the interaction between water, present in abundance in all deep geological environments, and ferrous minerals present in certain types of rocks. This generation occurs naturally in various particular geological environments, such as in mid-ocean ridges, obduction zones, subduction zones and in certain Archean and Neoproterozoic cratons. These environments are subjected to high temperatures ranging from 100°C to 400°C (and sometimes more) thus promoting an oxidation-reduction reaction.

[0008] Several chemical reactions can generate hydrogen naturally. The best known is the serpentinization reaction, which characterizes the hydration of olivine into serpentine. This reaction generates hydrogen as a by-product. More precisely, water causes oxidation of the iron contained in fayalite (the ferruginous pole of olivine representing approximately 10% of olivines) according to the following reaction:

[0009] 2H2O + 3Fe2SiO4 = 2Fe3O4 + 3SiO2 + 2H2(g)

[0010] A similar reaction capable of producing hydrogen also exists during the hydration of orthopyroxene. In cratons, it is the iron-rich rocks, in particular the BIF (Banded Iron Formation) which will oxidize, the iron passing from ferrous (Fe2+) to ferric (Fe3+). This same reaction can take place in the presence of amphiboles, present in granites, they are also rich in iron

[0011] Just as in the early days of oil exploration, the first signs of hydrogen generation in the subsoil were found on the surface. Indeed, some places in the world are known for their natural di-hydrogen emanations, such as the Yanartas fires in Turkey which have been burning for more than 2500 years. Other hydrogen emanations have also been identified on the surface associated with a singular geomorphology of the circular depression type measuring from a few meters to several kilometers called "witches' rings" and in which the vegetation is different.

[0012] Furthermore, a natural "onshore" hydrogen deposit was discovered by chance and has been exploited in Mali by the company Petroma (now Hydroma) since 2010. This shallow well provides power to a turbine that generates electricity for a village of 1,500 inhabitants. Since then, numerous exploration permits have been requested around the world, such as in the United States, France and Australia.

[0013] On the offshore side, certain geological environments have been identified as being able to generate natural hydrogen. This is the case for all mid-ocean ridges but also for the Mariana Trench, in which several volcanoes Serpentinized mud produces a gas mixing hydrogen and methane.

[0014] In this context, the invention consists of a method and a device capable of rapidly and automatically analyzing rock samples in the laboratory in order to determine the quantity of hydrogen generated during a water reduction reaction in the presence of this sample. The invention thus makes it possible to deduce the residual potential for the production of natural hydrogen from the rocks from which this sample originates.

[0015] This aim is achieved according to a first aspect of the invention by means of a method for automatic quantification of the dihydrogen generated by a sample of mineral source rock containing a ferrous metal compound, characterized in that a water reduction reaction is carried out in the presence of said sample and water vapor from 300°C up to a temperature of approximately 1200°C and the quantity of said dihydrogen generated by said sample during this reaction is determined with a view to qualifying said source rock as a potential source of natural hydrogen.

[0016] One of the parameters sought by the method according to the invention is the temperature (TmH2) corresponding to the generation of a maximum quantity of hydrogen and making it possible to determine the kinetics of generation of said hydrogen.

[0017] Another parameter sought by the process of the invention is the molar yield (qnH2) and / or the mass yield (qmH2) of the water reduction reaction characterized by the ratio between the molar quantity of hydrogen produced (nH2) and the molar quantity of the rock sample containing the iron (n reagent) or its mass in the case of the mass yield, and which is defined according to the following formulas:

[0018] pn(H2) = 2ÏI1E2Ë. x iooetîm(H2) = x 100 n reactive m reactive

[0019] The method of the invention thus uses the quantity of hydrogen generated relative to the mass of sample used during the analysis to calculate the useful molar and mass yields (pnH2 and pmH2) and determine the hydrogen potential as well as the maturity of the source rock.

[0020] According to an advantageous characteristic of implementing this method, the water is brought into contact with the rock sample by means of an inert vector gas transporting water vapor.

[0021] The initial temperature of the reactor is between 200°C and 400°C and the final temperature of the reduction reaction is between 600°C and 1200°C.

[0022] Preferably, the gradient of the temperature rise is between 0.1 and 50°C / min.

[0023] The flow rate of the carrier gas is between 0 and 500 mL / min and its water content is controlled by raising the temperature of a liquid water reserve or by vaporizing liquid water in a hot gas flow.

[0024] At the outlet of the reactor, the gaseous effluents resulting from the water reduction reaction are separated to ensure the condensation of the water and the drying of the gaseous fraction of the effluents.

[0025] Then, this gaseous fraction is analyzed in order to determine the quantity of hydrogen produced by the sample.

[0026] Another object of the invention is a device for implementing the method described above for the continuous quantification of hydrogen emitted by a sample of mineral or sedimentary source rock, characterized in that it comprises a reactor intended to receive said sample, said reactor being provided with a pipe for injecting a carrier gas supplied by a tank containing water heated between 0 and 100°C and provided with a temperature maintenance line, heating means ensuring temperature increases from 0 to 1200°C inside the reactor, a separator collecting the gaseous effluents from the reactor and ensuring the condensation of the water and the escape of the gaseous fraction of the effluents towards a drying means and a hydrogen detector analyzing the dried gaseous fraction.

[0027] According to an advantageous characteristic of the invention, the device comprises a piston ensuring the introduction of the sample into the reactor.

[0028] In addition, the device comprises thermocouples intended to control the temperatures of the tank and of the temperature maintenance line of the injected vector gas as well as a flow meter ensuring control of the flow rate of the injected vector gas.

[0029] Preferably, the device of the invention comprises an injection nozzle controlling the quantity of water injected into the reactor as well as a hygrometer or a dew point detector intended to control the water content of the injected vector gas.

[0030] The invention makes it possible to provide precise and reliable information to companies prospecting for hydrogen of natural origin from simple samples of source rocks taken from the subsoil. In particular, this information ensures good visibility as to the potential of a geological zone for the production of hydrogen.

[0031] The implementation of the quantification method can be carried out in the laboratory using a simple and easy-to-implement device, including in a nomadic and / or remote manner.

[0032] The invention thus allows the analysis of the hydrogen generation potential of a rock sample in less than an hour, whereas similar analyses in autoclaves, for example, can last for weeks.

[0033] Other characteristics and advantages of the invention will emerge from reading the description which follows, with reference to the appended figures which are detailed below.

[0034] [Fig.l] represents an embodiment of the device of the invention with the path of the vector gas during the implementation of the method.

[0035] [Fig.2] is a graph representing hydrogen generation as a function of temperature from a siderite sample.

[0036] [Fig.3] is a graph representing hydrogen generation as a function of temperature from a sample of olivine.

[0037] For clarity, identical or similar elements are identified by identical reference signs in the description and in the figures.

[0038] Naturally, the modes of implementing the method of the invention and of producing the associated device illustrated schematically by the figures presented above and described below, are given only as a non-limiting example. It is explicitly provided within the framework of the invention that different modes can be proposed and combined with each other to propose others.

[0039] In general, the invention relates to the field of prospecting for sources of natural hydrogen via the analysis of hydrogen source rocks in the laboratory. More specifically, the method of the invention consists of automatically quantifying the dihydrogen generated by a sample of mineral or sedimentary rock containing a ferrous metal compound during a water reduction reaction up to a temperature of 1200°C. Determining the quantity of dihydrogen generated by this sample thus allows the qualification of the source rock as a potential source of natural hydrogen via the parameters qH2 and TmH2.

[0040] For this purpose, water in vapor form is brought into contact with the rock sample in a reactor 1 by means of an inert carrier gas (for example nitrogen N2), as illustrated in [Fig.l]. The gaseous effluents resulting from the high-temperature water reduction reaction are conveyed and separated to ensure condensation of the water and drying of the gaseous fraction. This dried gaseous fraction is then analyzed at the end of the process to determine the quantity of hydrogen initially present in the sample.

[0041] The initial temperature of the water in steam form injected into reactor 1 is between 200°C and 400°C and the final temperature of the reduction reaction is between 600°C and 1200°C.

[0042] Preferably, the gradient of the temperature rise in the reactor 1 is between 0.1 and 50°C / min in order to be able to study the kinetics of hydrogen generation. The flow rate of the vector gas injected into the reactor is between 0 and 500 mL / min and the water content of the vector gas is controlled via the temperature rise of a reserve of liquid water.

[0043] Preferably, the temperature cycle integrated into the process starts at 300°C and has a 3 min hold. Then, a temperature increase is carried out at a rate of 25°C / min up to a final temperature of 1200°C.

[0044] An embodiment of the device for implementing this method is re shown in [Fig. 1]. This device comprises a ceramic reactor 1 supplied by a tube 21 ensuring the continuous injection of an inert carrier gas. This reactor is designed to be able to withstand temperatures of up to 1200°C obtained by means of a winding of heating wires whose turns have been judiciously distributed in order to obtain a homogeneous and precise temperature at the level of the sample. The rock sample(s) are introduced into the reactor 1 via an automatic sampler system allowing the samples to be placed on a piston 11 ensuring their translational movement in the reactor 1 and its sealing once closed.

[0045] The carrier gas is previously charged with water by means of a hydration / humidification system. For this purpose, the injection pipe 21 of the carrier gas is connected to a tank 2 containing water heated between 0 and 100°C. Thus, according to the method of implementing the method and by means of the device illustrated by [Fig.l], the carrier gas injected into the reactor 1 makes it possible to entrain a quantity of water which is intended to react in the reactor 1 with the mineral phase of the rock sample.

[0046] The carrier gas hydration system here comprises a tank 2 containing distilled water which is arranged upstream of the pyrolysis reactor 1 and in which the carrier gas bubbles. A device for controlling the hygrometry of the gas may also be added optionally in order to test different humidification rates. This tank 2 is equipped with thermal means 20 (such as Joule effect resistors) ensuring the heating of the water from 0 to 100°C so as to ensure its passage from the liquid phase to the vapor phase.

[0047] The gas tubing 21 going from the balloon 2 to the inlet of the reactor 1 is itself maintained at an appropriate temperature using a line 22 ensuring temperature maintenance and thus avoiding any condensation before chemical interaction with the rock sample. The device of the invention further comprises a system of solenoid valves (not shown) whose automatic activation makes it possible to choose the bypass of the humidification mode.

[0048] The flow rate of the carrier gas can be controlled using mass flow meters (not shown) capable of varying flow rates from 0 to 500 mL / min.

[0049] Furthermore, the device comprises thermocouples 23 intended to control the temperatures of the flask 2, of the tubing 21 of the injected vector gas and of the reactor 1 (located below the sample and on the wall of said reactor) as well as a flow meter (not shown) ensuring the control of the flow rate of the injected vector gas.

[0050] Preferably, the device of the invention comprises an injection nozzle (not shown) controlling the parameters of the vector gas as well as a hygrometer and / or a dew point detector (not shown) intended to control the water content of the injected vector gas.

[0051] At the outlet of reactor 1, the device comprises a system 3 ensuring the separation between the gaseous effluents from the pyrolyzed sample and the liquid fraction. These effluents then pass through a drying means such as a desiccant 4 in order to eliminate any residual water.

[0052] A hydrogen detector 6 ensures the final analysis of the dried gaseous fraction and makes it possible to determine the quantity of hydrogen initially present in the sample. Depending on the type of hydrogen detector 6 used at the end of the line, it will be possible to add a series of traps 5 in order to remove elements likely to interfere with the measurement.

[0053] Examples of implementation of the method of the invention will now be described in detail below, being applied to two different rock samples but under identical experimental conditions.

[0054] In these examples, the temperature of the tank 2 is maintained at 90°C as well as the injection pipe 21. The vector gas circulating in the water tank has a flow rate of 100 mL / min. The temperature cycle used starts at 300°C with a temperature plateau of 3 min and ends at 1000°C. The temperature gradient used is 20°C / min.

[0055] The two samples analyzed are, respectively, siderite (iron carbonate - [Fig.2]) and olivine (main mineral constituent of the Earth's mantle - [Fig.3]). Siderite, with the formula FeCO3, is of synthetic origin and 100% pure with an iron content of around 48%. Olivine is of the natural forsterite type with an iron content of around 3.8%.

[0056] When analyzing 120 mg of siderite, a significant hydrogen peak is generated between 350°C and 500°C corresponding to the decarbonation range of this mineral ( [Fig.2]). The integration of this curve makes it possible to evaluate the production at approximately 0.16 mg, or 0.08 moles of hydrogen for 1 mole of siderite analyzed, representing a yield of 8%. Then the hydrogen production falls back to zero thereafter. In this example, the temperature (TmH2) is equal to 452°C.

[0057] The analysis of 120 mg of forsterite produces less hydrogen, which is expected because this rock contains twelve times less iron than siderite. The molar yield this time is 0.6%. Hydrogen begins to be produced from 600°C but it is between 800°C and 1000°C that the peak of production is observed ([Fig.3]). In this example, the temperature (TmH2) is equal to 890°C.

Claims

Claims

1. Method for automatic quantification of the dihydrogen generated by a sample of mineral or sedimentary source rock containing a metallic compound containing iron, characterized in that a water reduction reaction is carried out in the presence of said sample and water vapor whose temperature has risen to approximately 1200°C and the quantity of said dihydrogen generated by said sample during this reaction is determined with a view to qualifying said source rock as a potential source of natural hydrogen.

2. Method according to claim 1, characterized in that the water is brought into contact with the rock sample by means of an inert carrier gas carrying water vapor.

3. Method according to one of the preceding claims, characterized in that the gaseous effluents resulting from the water reduction reaction are separated to ensure the condensation of the water and the drying of the gaseous fraction of said effluents.

4. Method according to the preceding claim, characterized in that the dried gaseous fraction is analyzed in order to determine the quantity of hydrogen initially present in the sample.

5. Method according to one of the preceding claims, characterized in that the initial temperature of the water vapor before the temperature rise is between 200°C and 400°C.

6. Method according to one of the preceding claims, characterized in that the final temperature of the water vapor at the end of the temperature rise during the reduction reaction is between 600°C and 1200°C.

7. Method according to one of the preceding claims, characterized in that the gradient of the temperature rise is between 0.1 and 50°C / min.

8. Method according to one of the preceding claims, characterized in that the flow rate of the carrier gas is between 0 and 500 mL / min.

9. Method according to one of the preceding claims, characterized in that the water content of the carrier gas is controlled by raising the temperature of a water reserve or by vaporization of liquid water in a flow of hot gas.

10. Method according to one of the preceding claims, characterized in that the temperature (TmH2) corresponding to the generation is determined of a maximum quantity of hydrogen and the kinetics of generation of said hydrogen are deduced.

11. Method according to one of the preceding claims, characterized in that the quantity of hydrogen generated by the sample is used to calculate the useful molar and mass yields (pnH2 and qmH2) and determine the potential quantity of hydrogen in the source rock as well as the maturity of the source rock from which said sample originates.

12. Device for the continuous quantification of hydrogen emitted by a sample of mineral or sedimentary source rock, characterized in that it comprises a reactor (1) intended to receive said sample, said reactor being provided with a pipe (21) for injecting a carrier gas supplied by a balloon (2) containing water heated between 0 and 100°C and provided with a temperature maintenance line (22), a coiled reactor with heating wires ensuring temperature increases from 0 to 1200°C inside said reactor, a separator (3) collecting the gaseous effluents from the reactor and ensuring the condensation of the water and the escape of the gaseous fraction of the effluents towards a drying means (4) and a hydrogen detector (6) analyzing the dried gaseous fraction.

13. Device according to claim 12, characterized in that it comprises a piston (11) ensuring the introduction of the sample into the reactor (1).

14. Device according to one of claims 12 or 13, characterized in that it comprises thermocouples (23) intended to control the temperatures of the tank (2) and of the line (22) for maintaining the temperature of the injected vector gas.

15. Device according to one of claims 12 to 14, characterized in that it comprises a flow meter ensuring control of the flow rate of the injected vector gas.

16. Device according to one of claims 12 to 15, characterized in that it comprises an injection nozzle controlling the quantity of water injected into the reactor (1).

17. Device according to one of claims 12 to 16, characterized in that it comprises a hygrometer or a dew point detector intended to control the water content of the injected vector gas.

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