System and method for measuring the effective concentration of at least one chemical component of a flowing fluid

Abstract

The invention relates to a system (100) for measuring the effective concentration of at least one chemical component of a flowing fluid (200) for an electrochemical generator system, the measurement system comprising: - a light source (10) configured to emit an excitation light beam (11), - a measuring cell (20) comprising a fluidic conduit adapted to a flow of the fluid, the excitation light beam passing through the fluid for a first light beam (12), - an optical device (30) reflecting the first light beam to form a second light beam (14) after passing through the flowing fluid, - a reference optical element (50) positioned on the optical path of one of said light beams, - a Raman spectrometer (45) configured to receive the second light beam and generate a Raman spectrum, - a computing unit (60) programmed to: · calculate,Based on a first part of the Raman spectrum relating to said composition, an adjustment value, calculate the effective concentration of said chemical component taking into account the adjustment value. Figure for the abbreviation: Fig. 1,

Description

Title of the invention: System and method for measuring an effective concentration of at least one chemical component of a flowing fluid Technical field of the invention

[0001] The present invention relates generally to the measurement of concentrations in fluids, in particular gases.

[0002] It relates more particularly to a system for measuring a concentration of at least one chemical component of a flowing fluid for an electrochemical generator system of the fuel cell or electrolyser type.

[0003] The invention finds a particularly advantageous application in the measurement of gas entering or leaving such an electrochemical generator system. State of the art

[0004] A fuel cell type electrochemical generator system makes it possible to generate electrical energy from the oxidation of fuel. This fuel is, for example, hydrogen. This produces electricity from hydrogen.

[0005] Conversely, an electrochemical generator system of the electrolyser type makes it possible to generate a chemical component from electrical energy. For example, an electrochemical generator system comprising an electrolytic cell based on the electrolysis of water makes it possible, using electrical energy, to generate hydrogen and oxygen. This results in the generation of hydrogen.

[0006] In order to be able to characterize the state of such an electrochemical generator system in operation, and thus estimate the performance in real time, it is necessary to measure the concentrations of the different chemical elements entering and / or leaving the electrochemical generator system.

[0007] Solutions consist of extracting a portion of the gas at the inlet or outlet of the electrochemical generator system and analyzing said gas with or without destruction of the extracted sample. In practice, a portion of the flow is diverted to a measuring system which is often based on the use of a Raman spectrometer. This extraction, however, causes disturbances in the operation of the electrochemical generator system.

[0008] Furthermore, during the Raman spectrometry measurement, the excitation light beam may vary in intensity and / or wavelength. This variation is for example due to thermal fluctuations of the light source. These variations then lead to variations in the measured concentrations. Presentation of the invention

[0009] In this context, the present invention provides a system for measuring an effective concentration of at least one chemical component of a flowing fluid for an electrochemical generator system, the measuring system comprising: - a light source configured to emit an excitation light beam, - a measuring cell comprising a fluid conduit adapted to a flow of the fluid in flux, the measuring cell comprising two sealed portholes arranged laterally on the fluid conduit and positioned opposite each other on a main optical axis transverse to the fluid conduit, the portholes being respectively arranged to receive the excitation light beam and transmit a first light beam formed by diffusion and / or transmission of the excitation light beam through the fluid in flux, - an at least partially reflective optical device positioned to reflect the first light beam and form a reflected light beam in the direction of the flowing fluid, the portholes being respectively arranged to receive the reflected light beam and transmit a second light beam formed by diffusion and / or transmission of the reflected light beam through the flowing fluid, - a reference optical element whose composition is predetermined, the reference optical element being positioned on the optical path of one of said light beams, - a Raman spectrometer configured to receive the second light beam and generate, on the basis of the second light beam, a Raman spectrum, - a calculation unit programmed for: • calculate, on the basis of a first part of the Raman spectrum relating to said composition, an adjustment value; and H determine, on the basis of a second part of the Raman spectrum relating to said chemical component, an intermediate concentration of said chemical component, then calculate, on the basis of the intermediate concentration and the adjustment value, the effective concentration of said chemical component; and / or H calculate, on the basis of the fitting value and the Raman spectrum, an adjusted Raman spectrum, and then determine, on the basis of a part of the adjusted Raman spectrum, the effective concentration of said chemical component.

[0010] Thus, the measuring cell according to the invention makes it possible to measure the concentrations of the different chemical components without diversion of the flow.

[0011] Furthermore, thanks to the invention, intrinsic variations of the excitation light beam are taken into account when measuring the concentration. Here, the term "effective" simply means, especially as opposed to "intermediate", that the concentration is corrected for certain variations in the measuring system or the electrochemical generator system. The "effective" concentration is therefore a reliable concentration.

[0012] Indeed, the reference optical element provides, on the Raman spectrum, a reference measurement (determined from the first part of the spectrum) which is independent of the fluid in flow. This means in particular that the reference measurement is not affected by variations in composition or pressure of the fluid in flow. This reference measurement therefore provides direct information on the excitation light beam.

[0013] The reference measurement can, on the one hand, provide information on variations in the intensity of the excitation light beam. For this purpose, the reference measurement, and the adjustment value deduced therefrom, are relative to an intensity of the Raman spectrum. The adjustment value is then directly dependent on said intensity fluctuations, which makes it possible to correct the intermediate concentration to make it independent of the intensity fluctuations of the excitation light beam.

[0014] The reference optical element thus makes it possible to obtain a measurement of the concentration which is independent of the intensity of the excitation light beam, namely the effective concentration.

[0015] The reference measurement can also provide information on variations in the wavelength of the excitation light beam. For this, the reference measurement, and the adjustment value deduced therefrom, are relative to a Raman shift of the Raman spectrum. The adjustment value is then directly dependent on said wavelength fluctuations, which makes it possible to adjust the Raman spectrum, which is more particularly adjusted in wavenumber, so that the concentrations deduced therefrom are independent of the wavelength fluctuations of the excitation light beam.

[0016] According to an advantageous and optional characteristic of the invention, in which the fluid is a gas, and the calculation unit is programmed to: • measure an effective concentration of each chemical component of the flowing fluid, • calculate a total concentration based on a sum of each effective concentration, • correct at least one of said effective concentrations on the basis of the total concentration.

[0017] Thus, variations in gas pressure are taken into account when measuring the actual concentrations. Indeed, the total concentration provides direct information on the gas pressure since it is independent of the relative concentrations of each chemical component of the gas.

[0018] When the total concentration is equal to 100%, it is not necessary to correct the actual concentrations.

[0019] Conversely, when the total concentration is greater (respectively less) than 100%, this means that the gas pressure is greater (respectively less) than a reference pressure used to calibrate the system. The calculation unit can then correct downwards (respectively upwards) the actual concentrations of the chemical components of the gas.

[0020] Other advantageous and non-limiting characteristics of the system according to the invention, taken individually or in all technically possible combinations, are the following: - the adjustment value is calculated on the basis of a comparison between said second part of the Raman spectrum and a part of a comparison Raman spectrum acquired previously or subsequently and corresponding to said second part; - the adjustment value depends on: H of a ratio between an intensity of the first part of the Raman spectrum and a corresponding intensity of said part of the comparison Raman spectrum, or H of a difference between a Raman shift of the first part of the Raman spectrum Raman spectrum and a corresponding Raman shift of said part of the comparison Raman spectrum, - the reference optical element is positioned between the measuring cell and the at least partially reflective optical device; - the composition of the reference element is selected based on said chemical component so that the first part of the Raman spectrum is distinct from the second part of the Raman spectrum; - the reference optical element is selected from the group comprising: plastic materials, crystalline materials, doped glasses; - the reference optical element is transparent and crossed by the first light beam or the second light beam; - the reference optical element is arranged so as to maintain the path of the first light beam or the second light beam straight through the reference optical element; - the reference optical element comprises one of the portholes; - the reference optical element comprises a gas or liquid sealed in an enclosure; - the reference optical element is a non-transparent solid arranged on said optical device and blocking only part of the first light beam; - the correction of said effective concentration comprises the division of said effective concentration by said total concentration; - said chemical component is selected from water, nitrogen, hydrogen, oxygen, carbon dioxide, methane, carbon monoxide.

[0021] The invention also provides a method for measuring a concentration of at least one chemical component of a flowing fluid comprising the following steps: - emission of an excitation light beam, - diffusion and / or transmission of the excitation light beam through the flowing fluid so as to form a first light beam, - reflection of the first light beam on an at least partially reflecting optical device into a light beam reflected towards the flowing fluid and diffusion and / or transmission of the reflected light beam through the flowing fluid so as to form a second light beam; - generation, by a Raman spectrometer, of a Raman spectrum based on the second light beam, - determination, on the basis of a first part of the Raman spectrum relating to a predetermined composition of a reference optical element positioned on the optical path of one of said light beams, of an adjustment value; and H determine, on the basis of a second part of the Raman spectrum relating to said chemical component, an intermediate concentration of said chemical component, then calculate, on the basis of the intermediate concentration and the adjustment value, the effective concentration of said chemical component; and / or H calculate, on the basis of the fitting value and the Raman spectrum, an adjusted Raman spectrum, and then determine, on the basis of a part of the adjusted Raman spectrum, the effective concentration of said chemical component.

[0022] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Detailed description of the invention

[0023] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0024] In the attached drawings:

[0025] [Fig-1] is a schematic representation from above of a measuring system according to the invention in which the reference optical element is solid.

[0026] [Fig.2] is a schematic side view of a measuring cell of another example of a measuring system according to the invention in which the reference optical element is liquid or gaseous.

[0027] [Fig.3] is a block diagram of a sequence of steps implemented by the measurement system of [Fig.l].

[0028] [Fig.4] is a graphical representation of a Raman spectrum obtained by the spec- trometer of the system of [Fig.l].

[0029] [Fig.5] is a graphical representation of spectrometry measurements from the spectrum of [Fig.4].

[0030] [Fig.6] is a graphical representation of the concentrations (in percentage) of two chemical components of a flowing fluid, measured using the system of [Fig.l], over time.

[0031] In [Fig.l], a schematic view of a measuring system 100 is shown, making it possible in particular to measure concentrations of chemical components (i.e. chemical elements, typically molecules) present in a flowing fluid 200. The flowing fluid 200 may be in gaseous or liquid form. The term “flowing” here means, as will be clearly understood below, that the flowing fluid 200 is flowing at the time of the measurement. The flowing fluid 200 is hereinafter simply called fluid 200.

[0032] As shown in [Fig.l], the measuring system 100 here comprises a light source 10, a measuring cell 20, an optical device 30, a spectrometer 45, a reference optical element 50 and a calculation unit 60.

[0033] The measuring system 100 is particularly suitable for carrying out measurements on the fluid 200 coming from or supplying an electrochemical generator system 301. The electrochemical generator system 301 can be used as an electrolyzer. For example, the electrochemical generator system 301 is an electrolyzer used for the production of hydrogen. The electrochemical generator system 301 then consumes electricity in order to produce hydrogen.

[0034] In another application, the electrochemical generator system 301 is used to generate electricity. In this case, the electrochemical generator system 301 consumes a fuel, for example hydrogen, in order to produce electricity.

[0035] The spectrometer 45 is particularly suitable for measuring the concentration of at least one chemical component of the fluid 200 among water, nitrogen, di-hydrogen, dioxygen, carbon dioxide, methane, carbon monoxide.

[0036] Thus, the spectrometer 45 is preferably a Raman spectrometer.

[0037] Here, as shown in [Fig.l], the light source 10 and the spectrometer 45 are here part of a spectrometry device 40. In the example of [Fig.l], the spectrometry device 40 is placed opposite the measuring cell 20. However, conventionally, the light source 10 and the spectrometer 45 can be placed at a distance of the measuring cell 20 and the light beam emitted by the light source can be routed using fiber optic cables.

[0038] The light source 10 is preferably a laser having a high intensity. Here, the light source 10 is for example a laser with a power of 1.5 W which emits a monochromatic light beam at a wavelength of 532 nm. The light source 10 is of high power in order to obtain a Raman signal having an intensity sufficiently high to allow an integration time compatible with real-time monitoring, for example at a rate of between 0.1 Hz and 10 Hz. Alternatively, the excitation light beam is generated from any light source suitable for Raman spectrometry. The light source 10 is for example controlled by the spectrometer 45.

[0039] The light source 10 produces a beam generally called the “light beam” and which, as detailed below, more particularly comprises: an excitation light beam, a first light beam, a reflected light beam and a second light beam.

[0040] The measuring cell 20 comprises an inlet opening 21, an outlet opening 22, a first porthole 23, a second porthole 24 and a casing 25. The ports 23, 24 are positioned at lateral openings provided in the casing 25. The casing 25 and the ports 23, 24 here delimit a fluid conduit inside which the fluid 200 flows. The fluid conduit therefore extends from the inlet opening 21 to the outlet opening 22 of the measuring cell 20.

[0041] As shown in [Fig.l], the inlet opening 21 is connected to a first conveying conduit 302 for the fluid 200, itself connected to the electrochemical generator system 301. This first conveying conduit 302 thus fluidically connects the electrochemical generator system 301 to the measuring cell 20. The outlet opening 22 is connected to a second conveying conduit 303 for the fluid 2, itself connected to a reservoir 304 designed to collect the fluid 200. This second conveying conduit 304 thus fluidically connects the measuring cell 20 to the reservoir 304.

[0042] Thus, as shown in [Fig. 1], the measuring cell 20 makes it possible to carry out measurements on the outgoing fluid 200, i.e. produced by the electrochemical generator system 301. As shown in [Fig. 1], the measuring cell 20 is for example connected to an outlet of an electrolyser for the generation of hydrogen.

[0043] Of course, reciprocally, the outlet opening can be connected to a conduit for conveying fluid in flow at the inlet of the electrochemical generator system. In this case, the measuring cell makes it possible to carry out measurements on the fluid entering the electrochemical generator system. The measuring cell is for example connected to an inlet of an electrochemical generator system of the fuel cell type. hydrogen for generating electricity from hydrogen.

[0044] In order not to cause any change in pressure or flow rate of the fluid 200, the section of the inlet opening 21, the section of the outlet opening 22 and the section of the casing 25 are preferably each greater than or equal to the section of the conveying conduits 302, 303 of the fluid 200.

[0045] The portholes 23, 24 are sealed, which means that the fluid 200 cannot escape from the fluid conduit at the level of the side openings.

[0046] Here, the measuring cell 20 comprises seals (not shown) interposed between the casing 25 and the portholes 23, 24. The measuring cell 20 comprises, for example, one seal per porthole 23, 24. The seals are, for example, manufactured with a fluoroelastomer material (commonly called FKM or viton).

[0047] Here, the term “porthole” means a glazed part of any shape allowing optical access to the interior of the casing 25, that is to say to the interior of the fluid conduit.

[0048] Thus, each porthole 23, 24 here comprises a glass slide. These glass slides are preferably made from a borosilicate or aluminosilicate glass or an alkali-aluminosilicate glass, for example from BK7 or with Gorilla Glass. Preferably, the glass slides do not have a surface coating on their face in contact with the fluid 200 (i.e. their face oriented towards the inside of the casing 25). The composition and arrangement of the glass slides make it possible to avoid any degassing or contamination of the fluid 200 which would be likely to pollute the measurement.

[0049] The two portholes 23, 24 are arranged laterally on the casing 25 downstream of the inlet opening 21 and upstream of the outlet opening 22 with reference to the flow of the fluid 200. The two portholes 23, 24 are positioned opposite one another. For example, when the casing 25 is of circular section, the two portholes 23, 24 are arranged diametrically opposite one another. In another example, when the casing 25 is of square or rectangular section, the two portholes 23, 24 are arranged on two opposite faces of the casing 25. In all cases, the two portholes 23, 24 are arranged so that the fluid 200 flows between the portholes 23, 24.

[0050] As shown in [Fig.l], the measuring cell 20 is arranged so that the two portholes 23, 24 are aligned on a main optical axis OA transverse to the direction of flow of the fluid 200. This means that the portholes 23, 24, and more particularly their glass plate, intersect the main optical axis OA. In the example shown in [Fig.l], the main optical axis OA is more specifically perpendicular to the direction of flow of the fluid 200.

[0051] The two portholes 23, 24, and more particularly their glass blade, are configured to transmit the light beam. Preferably, as shown in [Fig.l], this light beam propagates along a main illumination axis aligned with the main optical axis OA, i.e. parallel to the main optical axis OA.

[0052] As shown in Figures 1 and 2, the system 100 also comprises a focusing element 70 arranged on the path of the light beam, between the light source 10 and the first porthole 23. The focusing element 70 is configured to focus the light beam in the fluid 200 between the two portholes 23, 24. The focusing element 70 is for example a lens or an objective, as shown in [Fig. 2],

[0053] Alternatively, the focusing element and the first porthole could be combined into a single element.

[0054] The optical device 30 is at least partially reflective. In this case, as shown in [Fig. 2], the optical device 30 is a concave mirror of hemispherical shape. The device 30 is here arranged so that its center of curvature is on the main optical axis OA, equidistant between the two portholes 23, 24.

[0055] As shown in [Fig.l], the optical device 30 is arranged opposite the second porthole 24. The optical device 30 thus makes it possible to reflect the light coming from the latter towards the second porthole 24. The optical device 30 is therefore placed opposite the light source 10 with respect to the measuring cell 20.

[0056] The measuring cell 20 is thus of the double pass type because, associated with the optical device 30, it allows double excitation of the fluid 200. Indeed, the light beam passes through the measuring cell 20 and is then refocused in the fluid 200, which makes it possible to double the excitation. This optical configuration also has the advantage of doubling the solid collection angle by collecting the light emitted towards the spectrometer 45 but also that emitted towards the optical device 30 which is then reflected and returned towards the spectrometer 45. The term “double pass” is thus linked to the round trip path of the light beam in the measuring cell 20. However, the fluid 200 only passes through the measuring cell 20 once, in the direction of the flow, without interruption of the flow.

[0057] The reference optical element 50 is positioned on the optical path of the light beam. In other words, the reference optical element 50 is arranged between the light source 10 and the spectrometer 45. This positioning allows the reference optical element 50 to interact with the light beam on its path between the light source 10 and the spectrometer 45.

[0058] As shown in Figures 1 and 2, the reference optical element 50 is positioned between the measuring cell 20 and the optical device 30. This positioning advantageously makes it possible to take into account, that is to say to compensate for, any fluctuations in light intensity linked to the measuring cell 20 such as an obscur- sealing of portholes 23, 24.

[0059] The reference optical element 50 has a predetermined composition. In practice, this means that the composition is selected during the assembly of the measurement system 100. The composition of the optical element is also invariant (unlike the composition of the fluid which can vary over time). By “invariant” is meant that the composition remains unchanged on the scale of the concentration measurements and in particular, when the latter are monitored in real time. This also means that it is insensitive to variations in pressure of the fluid 200.

[0060] The reference optical element 50 may comprise a gas, a liquid or a solid.

[0061] In the example of [Fig.l], the reference optical element 50 is solid. The element reference optics 50 comprises for example a polymer material, a crystalline material, a doped glass.

[0062] In the example of [Fig. 2], the reference optical element 50 is gaseous or liquid. As shown in [Fig. 2], the gas or liquid is then sealed in an enclosure 51. The gas may for example be carbon dioxide. The liquid may for example be a benzene derivative such as xylene. As shown in [Fig. 2], the enclosure 51 is here provided with a transparent window 52 sealingly closing the enclosure 51. Here, the optical device 30 is also sealed in the enclosure 51.

[0063] In any case, as detailed later, the solid, gas or liquid of the reference optical element 50 is preferably adapted to the chemical components of the fluid 200.

[0064] Here, as shown in [Fig.l], the reference optical element 50 is transparent. It is then crossed by the light beam, in particular after its first passage through the measuring cell 20. The reference optical element 50 can be arranged so as to keep the optical path of the light beam passing through it rectilinear. In other words, the reference optical element 50 does not deflect the light beam passing through it. The reference optical element 50 can also deflect the light beam passing through it; in this case, the measuring system 100 comprises optical adjustment means for correcting the path of said beam.

[0065] The computing unit 60 comprises at least one memory and at least one processor. The computing unit 60 also comprises interfaces allowing the computing unit 60 to receive information from the spectrometer 45. Here, the computing unit 60 acts as a synchronization box and triggers the light emission and the data acquisitions of the spectrometer 45, which means that the computing unit 60 controls the data acquisitions.

[0066] The memory of the computing unit 60 is a computer-readable recording medium comprising instructions which, when executed by the processor, make it possible to determine the effective concentration of at least one chemical component of fluid 200 based on data provided by spectrometer 45.

[0067] The measuring system 100 makes it possible to implement a method for measuring the concentration of at least one chemical component of the fluid 200. This method is described with reference to FIGS. 3 to 6. In these figures, the fluid 200 comprises, for example, two components, namely nitrogen and hydrogen. For illustrative purposes, the concentrations are predetermined: the concentration of hydrogen is approximately twice the concentration of nitrogen (see [Fig. 6]).

[0068] As shown in [Fig. 3], this method begins with a first step E1 of emitting an excitation light beam 11 by the light source 10. As a reminder, the intensity of the excitation light beam 11 may be caused to fluctuate. These fluctuations may, for example, come from the light source 10 or from the light routing circuit (for example, the aforementioned fiber optic cables).

[0069] The method continues with a second step E2 comprising the diffusion and / or transmission of the excitation light beam 11 through the fluid 200 so as to form a first light beam 12.

[0070] As visible in [Fig.l], this second step E2 also comprises the transmission of the excitation light beam 11 through the first porthole 23 and the transmission of the first light beam 12 through the second porthole 24. The first light beam 12 passes through the second porthole 24 towards the optical device 30.

[0071] The method then comprises a third step of interaction with the reference optical element 50. The third step here comprises a first sub-step E31, which takes place during the outward path of the light beam (i.e. before reflection on the optical device 30), during which the interaction comprises the passage of the first light beam 12 through the reference optical element 50 (see [Fig.l]).

[0072] The method then comprises a fourth step E4 in which the optical device 30 reflects the first light beam 12 into a reflected light beam 13 in the direction of the second porthole 24, and therefore in the direction of the fluid 200. The optical device 30 is positioned to receive the first light beam 12. The reflecting optical device 30 being positioned outside the measuring cell 20, any interaction between the fluid 200 and a reflective coating, for example metallic, of the optical device 30 is avoided. This makes it possible to prevent any pollution of the fluid 200. The optical device 30 is configured to focus the reflected light beam 13 in the measuring cell 20 between the two portholes 23, 24, for example in the middle of the two portholes 23, 24.

[0073] The method then continues with a second sub-step E32 of the third step of interaction with the reference optical element 50. During this second sub-step E32, which takes place during the return path of the light beam (i.e. after reflection on the optical device 30), the interaction comprises the passage of the reflected light beam 13 through the reference optical element 50 (see [Fig. 1]).

[0074] The method then comprises a fifth step E5 comprising the diffusion and / or transmission of the reflected light beam 13 through the fluid 200 so as to form a second light beam 14.

[0075] As visible in [Fig.l], this fifth step E5 also comprises the transmission of the reflected light beam 13 by the second porthole 24 and the transmission of the second light beam 14 by the first porthole 23. The second light beam 14 passes through the first porthole 23 in the direction of the optical element 70. The optical element 70 makes it possible to focus the second light beam 14 in the direction of the spectrometer 45.

[0076] The method then comprises a sixth step E6 of generation, by the spectrometer 45, of a Raman spectrum on the basis of the second light beam 14. Such a Raman spectrum is represented in [Fig.4].

[0077] In order to produce this Raman spectrum, the spectrometer 45 is configured to receive the second light beam 14, which here comprises Raman signals emitted by the fluid 200 (thanks to its excitation by the excitation light beam 11 and by the reflected light beam 13) and the reference optical element 50 (thanks to its excitation by the first light beam 12 and by the reflected light beam 13). Conventionally, the spectrometer 45 comprises a diffraction grating and a light sensor. It also comprises a processing system for reading the light sensor and deducing the Raman spectrum therefrom. The method then comprises a seventh step E7 during which the calculation unit 60 generates spectrometry measurements from the Raman spectrum.

[0078] The computing unit 60 first generates a spectrometry measurement per chemical component, i.e. here one for nitrogen and one for hydrogen. These spectrometry measurements relating to the chemical components are subsequently called spectrometry measurements of interest.

[0079] The spectrometric measurement of interest of each chemical component is based on a part of the Raman spectrum relating to said chemical component.

[0080] For example, on the Raman spectrum of [Fig.4], an intensity I of the signal provided by the light sensor is represented as a function of the Raman shift Aco (in cm1). The Raman shift is represented in wavenumber, that is to say in inverse units of the wavelength. The intensities are presented in arbitrary units corresponding for example to a photon count by the light sensor.

[0081] This intensity I has in particular a first peak at approximately 2301 cm 1 corresponding to dinitrogen (N2) and a second peak at approximately 4100 cm 1 corresponding to dihydrogen (H2). Thus, the part of the Raman spectrum near the first peak is "relative" to nitrogen, particularly in the sense that it includes the characteristic peak of this chemical component. Similarly, the part of the Raman spectrum near the second peak is "relative" to dihydrogen.

[0082] The Raman shifts associated with chemical components are well known in the literature (and universal because they are normalized in wavelength). Thus, conventionally, for each chemical component, the spectrometry measurement of interest can correspond to the height of the associated peak (for example the maximum of the peak), or to the area of this peak, i.e. the surface of this peak which is for example calculated for a predetermined shift interval.

[0083] The term "part of the Raman spectrum relating to a chemical component" is therefore understood to mean a Raman shift value or a set of Raman shift values which is characteristic of said chemical component, in the sense that, in Raman spectrometry, said chemical component emerges in a predetermined manner at these Raman shift values.

[0084] In practice, the parts of the Raman spectrum relating to the chemical components are here Raman shift intervals (i.e. ranges of Raman shift values, here expressed in cm1). In the example of [Fig.4], the part of the Raman spectrum relating to dinitrogen, referenced PI, is an interval 100 cm1 wide centered around 2330 cm1 (peak associated with dinitrogen). The part of the Raman spectrum relating to dihydrogen, referenced P2, is an interval of 80 cm1 centered around 4160 cm 1 (peak associated with dihydrogen). The spectrometry measurements of interest then correspond respectively to the integral of the intensity I over these parts PI, P2 of the Raman spectrum, i.e. to the areas under the peaks.

[0085] Of course, the widths of the aforementioned intervals can be defined more or less broadly. It is indeed possible to adjust the measuring system 100 to increase the spectral resolution of the spectrometer 45 and obtain finer peaks. The parts of the Raman spectrum relating to the chemical components can then be defined more narrowly.

[0086] Alternatively, the parts of the Raman spectrum relating to the chemical components could be a single Raman shift value, with the spectrometry measurements of interest then corresponding to the intensities of the spectrum at these shift values.

[0087] In the seventh step E7, the calculation unit 60 also generates a spectrometry measurement relating to the reference optical element 50. This spectrometry measurement relating to the reference optical element is subsequently called the reference spectrometry measurement.

[0088] In the Raman spectrum of [Fig.4], the reference optical element 50 is made of glass, here fused silica, which provides a fluorescence signal. Unlike the peaks associated with the chemical components, the fluorescence signal is extended. In [Fig.4], the signal fluorescence is clearly visible since it raises the baseline of the spectrum. The intensity of the fluorescence signal depends on the quality of the glass, with lower quality glass providing a stronger fluorescence signal, which advantageously allows the intensity of the fluorescence signal to be modified.

[0089] In the same way as for the chemical components, since the composition of the reference optical element 50 is predetermined and invariant, a part of the spectrum "relative" to the reference optical element 50 can be determined. Therefore, "part of the Raman spectrum relative to the reference optical element" means a Raman shift value or a set of Raman shift values which is characteristic of the reference optical element 50, more particularly of its composition.

[0090] In practice, the part of the Raman spectrum relating to the reference optical element 50 is here also a Raman shift interval (i.e. ranges of Raman shift values, here expressed in cm1). In the example of [Fig.4], the part of the Raman spectrum relating to the reference optical element 50, referenced P3, extends from 2600 cm 1 to 3800 cm 1 (fluorescence signal associated with fused silica). The reference spectrometry measurement then corresponds to the integral of the intensity I over this part P3 of the Raman spectrum.

[0091] Alternatively, the part of the Raman spectrum relating to the reference optical element could be a single Raman shift value, the spectrometry measurement of interest then corresponding to the intensity of the spectrum at this shift value.

[0092] Advantageously, the composition of the reference optical element 50 is selected as a function of the chemical components to be detected in the fluid 200. This composition is selected so that the parts P1, P2 of the Raman spectrum relating to the chemical components are distinct, i.e. disjoint, from the part P3 of the Raman spectrum relating to the reference optical element 50 (as is the case in [Fig.4]). Thus, the spectrometry measurements of interest are not affected by the reference spectrometry measurement and vice versa.

[0093] Alternatively, it is possible to select the reference optical element so that it provides a Raman peak (and not an extended fluorescence signal).

[0094] At this stage of the method, the spectrometry measurements of interest depend on the concentrations of the chemical components in the fluid 200, the pressure of the fluid 200 and the intensity of the light beam, i.e. the intensity of the excitation light beam 11. Here, each spectrometry measurement of interest depends in a globally linear manner on each of these parameters. The reference spectrometry measurement depends solely on the intensity of the excitation light beam 11 (since its composition is predetermined and invariant).

[0095] In [Fig.5], the spectrometry measurements of interest and the reference spectrometry measurement are repeated over time and represented graphically. In this graphic, the concentrations and the pressure of the fluid 200 are invariant. We can clearly see that the variations in the spectrometry measurements of interest (H2 and N2) are correlated to the variations in the reference spectrometry measurement (referenced R), and therefore, through the latter, to the variations in intensity of the excitation light beam 11. In this figure, the abscissa scales are relative here in order to be able to distinguish all the spectrometry measurements.

[0096] The advantage of the measuring system 100 is to be able to compensate for such variations (due to variations in the intensity of the excitation light beam 11) of the spectrometry measurements of interest thanks to the reference spectrometry measurement (and therefore thanks to the reference optical element 50). This thus makes it possible to make the concentration measurements independent of the intensity of the excitation light beam 11. A first phase of the method, comprising steps E8 to E10, therefore consists of making the concentration measurements independent of the intensity of the excitation light beam 11.

[0097] During an eighth step E8 of the method, the calculation unit 60 converts each spectrometry measurement of interest into an intermediate concentration of the chemical component associated with the measurement. For this, for each chemical component, the calculation unit 60 implements a calibration function.

[0098] Each calibration function is here pre-recorded on the memory of the calculation unit 60. Conventionally, each calibration function is representative of an affine relationship between the spectrometry measurement of interest and the concentration of the chemical component. Each calibration function is determined using measurements carried out on standard fluids comprising predetermined concentrations of the chemical component. Each calibration function is established for a predetermined and controlled reference pressure of the standard fluid. The calibration functions are for example established for a reference pressure of between 1 and 5 bars. Here, the reference pressure is equal to 1 bar.

[0099] The method comprises a ninth step E9 of calculating, on the basis of the reference spectrometry measurement, an adjustment value.

[0100] For this, the calculation unit 60 compares the reference spectrometry measurement with a comparison spectrometry measurement from a comparison Raman spectrum acquired, by the spectrometer 45, before or after the reference spectrometry measurement. The comparison spectrometry measurement is obtained like the reference spectrometry measurement, that is to say on the basis of the intensity of the comparison Raman spectrum considered at the same Raman shift values as those used to determine the reference spectrometry measurement. In other words, the comparison spectrometry measurement therefore corresponds to the reference spectrometry measurement shifted in time.

[0101] In practice, the part of the comparison Raman spectrum used to determine the comparison spectrometry measurement is therefore also a Raman shift interval, and more specifically the same Raman shift interval as the part P3 of the Raman spectrum relating to the reference optical element 50. Thus, in the example of [Fig.4], the comparison spectrometry measurement is also obtained as the integral over the interval 2600 cm 1 to 3800 cm 1 of the intensity of the comparison Raman spectrum (also generated by the spectrometer 45).

[0102] Alternatively, the Raman shift interval related to the comparison spectrometry measurement could be slightly wider, narrower or shifted, compared to that related to the reference spectrometry measurement.

[0103] Here, the comparison Raman spectrum is acquired at an initial instant preceding the concentration measurements (and therefore preceding the reference and interest spectrometry measurements). Here, the fluid 200 is already circulating in the measuring cell 20 during the acquisition of the comparison Raman spectrum. Alternatively, this comparison Raman spectrum can be acquired at the end of the concentration measurements, which makes it possible to process the data acquired by the spectrometer 45 after the fact.

[0104] To calculate the adjustment value, the calculation unit 60 more particularly performs a ratio between the reference spectrometry measurement and the comparison spectrometry measurement.

[0105] Finally, during a tenth step E10 of the method, the calculation unit 60 calculates each effective concentration of each chemical component as the ratio (i.e. the division) between the intermediate concentration of said chemical component and the adjustment value. Remarkably, the measured effective concentrations are then independent of the fluctuations in intensity of the excitation light beam 11 since these concentrations are normalized by the adjustment value which is directly dependent on said fluctuations.

[0106] Preferably, the measurement of the effective concentrations is repeated to ensure temporal monitoring of these effective concentrations. For this, the Raman spectrum is for example generated at a frequency of 1 Hz. However, it is possible to implement the steps of the method only once to obtain a measurement of the effective concentrations only at a given time.

[0107] At this stage, the effective concentrations are made independent of the fluctuations in intensity of the excitation light beam 11. Advantageously, the measuring system 100 also makes it possible to make the effective concentrations independent of the fluctuations in pressure of the fluid 200. Such pressure variations occur in particular when the fluid 200 is a gas. A second phase of the method (comprising steps E1 to E13) then consists of making the measured effective concentrations independent of the pressure of the fluid 200.

[0108] To compensate for pressure variations, it is necessary to determine all the chemical components potentially present in the fluid 200. Indeed, determining the effective concentration of each component of the fluid 200 makes it possible to calculate a total concentration CT which must theoretically be 100% since it takes into account all the chemical components of the fluid. A deviation from this nominal value is then representative of a pressure variation which, thanks to the measuring system 100, can then be compensated.

[0109] The method therefore comprises an eleventh step El 1 of measuring the effective concentration of each component of the fluid 200. The effective concentrations are here relative concentrations expressed as a percentage. Of course, they can be expressed in other units.

[0110] The method then comprises a twelfth step E12 in which the calculation unit 60 sums the effective concentrations to determine the total concentration CT of chemical component of the fluid 200. The total concentration CT is thus equal to the sum of all the effective concentrations.

[0111] The method then ends with a thirteenth step El3 of correction of actual concentrations based on total concentration.

[0112] During the thirteenth step El3, the calculation unit 60 corrects the actual concentrations by dividing them by the ratio between the total concentration CT and a total reference concentration. The total reference concentration is a theoretical total concentration, i.e. equal to 100% since the concentrations are here expressed as a percentage.

[0113] Thus, when the total concentration CT is different from 100, said ratio is different from 1 and the calculation unit 60 then corrects the effective concentrations. Conversely, when the total concentration CT is 100%, the effective concentrations are not corrected since the ratio is equal to 1.

[0114] In the example of [Fig.6], the fluid 200 is a gas comprising only two chemical components whose proportions are invariant: nitrogen (N2) and hydrogen (H2). The total concentration CT is therefore equal to the sum of the two effective concentrations. Over the first period, before time T1, the calculation unit 60 does not correct the effective concentrations since the total concentration is equal to 100%. Conversely, over the second period, after time T1, the total concentration is 120%, which means that the pressure of the fluid 200 has increased by 20% compared to the first period. Over this second period, the effective concentrations are therefore overestimated by 20%. The calculation unit 60 is then programmed to divide the effective concentrations by 1.2 (ratio of the total concentration 120% to the theoretical total concentration 100%).

[0115] The present invention is in no way limited to the embodiment described and re presented, but the person skilled in the art will know how to make any variation in accordance with the appended claims.

[0116] For example, the adjustment value can also make it possible to correct variations in the wavelength of the light beam. Indeed, although the light source is designed to emit a light beam at a reference wavelength, here 532 nm, variations of a few nanometers around this reference wavelength can occur.

[0117] To capture them, the reference optical element is preferably selected to provide a Raman peak on the Raman spectrum generated by the spectrometer. However, it is also possible to monitor these variations around this reference wavelength via a fluorescence signal.

[0118] The calculation unit is then programmed to measure, on the Raman spectrum, the Raman shift (in cm1) corresponding to the peak associated with the reference optical element. The calculation unit more specifically determines the reference measurement as the Raman shift corresponding to the maximum of the intensity of the Raman spectrum on the part of the Raman spectrum relating to the reference optical element.

[0119] The adjustment value can then be defined as the difference (in wavelength or in wave number) between the reference measurement and a comparison Raman shift which corresponds either to a predetermined value or to the Raman shift measured on the comparison Raman spectrum. The adjustment value is then representative of a variation in wavelength of the excitation light beam. More specifically, it allows the calculation unit to determine said variation in wavelength of the excitation light beam relative to its reference wavelength.

[0120] The calculation unit can then calculate an adjusted Raman spectrum, more specifically adjusted in wavenumber (or wavelength). The adjusted Raman spectrum takes into account the fact that the excitation light beam has varied in wavelength. The adjusted Raman spectrum thus corresponds to the Raman spectrum adjusted in wavelength (or wavenumber). The calculation unit then determines the concentrations of the chemical components as detailed above, i.e. by means of the parts of the Raman spectrum relating to the chemical components and the calibration functions, on the basis of the adjusted Raman spectrum. These concentrations are then also described as “effective” in the sense that they are more reliable (because they are wavelength corrected) than concentrations that would be acquired without processing (i.e. without wavelength adjustment) directly from the Raman spectrum.

[0121] Preferably, the calculation unit is programmed to successively implement the wavelength correction and then the intensity correction. For this, the calculation unit first determines the adjusted Raman spectrum to take into account takes into account possible variations in wavelength of the light source, then determines, on the basis of the adjusted Raman spectrum, the spectrometry measurements to calculate the intermediate concentrations and then the effective concentrations. In practice, the calculation unit then determines a first adjustment value for the wavelength correction and then a second adjustment value for the intensity correction. This means that steps E7 to E9 are carried out on the basis of the adjusted Raman spectrum.

[0122] As another example, the reference optical element may be positioned elsewhere than between the measuring cell and the optical device. For example, it is positioned between the light source and the measuring cell (it is then crossed by the excitation light beam and the second light beam). Indeed, to produce the reference spectroscopy measurement, it is sufficient for the reference optical element to be positioned on the optical path of the light beams, i.e. the optical path of the excitation light beam and / or of the first light beam and / or of the reflected light beam and / or of the second light beam.

[0123] The reference optical element can also interact with the light beam by reflection. In this case, the reference optical element is not transparent. For example, the optical element comprises a deposit, i.e. a thin, typically metallic layer, covering the optical device. This deposit is then preferably provided on only a portion, preferably a minority portion, of the reflective surface of the optical device. Thus, a portion of the first beam is reflected by the optical device while another distinct portion is reflected by the reference optical element. This makes it possible to maintain a high signal-to-noise ratio for the spectrometry measurements of interest.

[0124] The reference optical element could also deflect the light beam. The measurement system may then include additional optical elements, such as mirrors and lenses, to direct and / or shape the light beam.

[0125] Although represented as a separate element of the measuring system, the reference optical element can be combined with another element of the measuring system in the sense that said other element has a predetermined and invariant composition making it possible to generate the reference spectrometry measurement. The reference optical element can for example be one of the windows, for example made of sapphire and then having a Raman peak around 4200 cm1 (the reference spectrometry measurement can then consist of the height of this peak).

Claims

Claims

1. System (100) for measuring an effective concentration of at least one chemical component of a flowing fluid (200) for an electrochemical generator system (100), the measuring system (100) comprising: - a light source (10) configured to emit an excitation light beam (11), - a measuring cell (20) comprising a fluid conduit adapted to a flow of the flowing fluid (200), the measuring cell (20) comprising two sealed portholes (23, 24) arranged laterally on the fluid conduit and positioned opposite each other on a main optical axis (OA) transverse to the fluid conduit, the portholes (23, 24) being respectively arranged to receive the excitation light beam (11) and transmit a first light beam (12) formed by diffusion and / or transmission of the excitation light beam (11) through the flowing fluid (200),- an at least partially reflective optical device (30) positioned to reflect the first light beam (12) and form a reflected light beam (13) towards the flowing fluid (200), the portholes (23, 24) being respectively arranged to receive the reflected light beam (13) and transmit a second light beam (14) formed by diffusion and / or transmission of the reflected light beam (13) through the flowing fluid (200), - a reference optical element (50) whose composition is predetermined, the reference optical element (50) being positioned on the optical path of one of said light beams (11, 12, 13, 14), - a Raman spectrometer (45) configured to receive the second light beam (14) and generate, on the basis of the second light beam (14), a Raman spectrum, - a computing unit (60) programmed to:, • calculate, on the basis of a first part (P3) of the Raman spectrum relating to said composition, an adjustment value; and H determine, on the basis of a second part (PI, P2) of the Raman spectrum relating to said chemical component, an intermediate concentration of said chemical component, then calculate, on the basis of the intermediate concentration and the adjustment value, the effective concentration of said chemical component; or H calculate, on the basis of the fitting value and the Raman spectrum, an adjusted Raman spectrum, and then determine, on the basis of a part of the adjusted Raman spectrum, the effective concentration of said chemical component.

2. A measurement system (100) according to claim 1, wherein the adjustment value is calculated on the basis of a comparison between said first part (P3) of the Raman spectrum and a part of a comparison Raman spectrum, acquired previously or subsequently, corresponding to said first part (P3).

3. A measuring system according to claim 2, wherein the adjustment value depends: H on a ratio between an intensity of the first part (P3) of the Raman spectrum and a corresponding intensity of said part of the comparison Raman spectrum, or H on a difference between a Raman shift of the first part (P3) of the Raman spectrum and a corresponding Raman shift of said part of the comparison Raman spectrum.

4. Measuring system (100) according to one of claims 1 to 3, wherein the reference optical element (50) is positioned between the measuring cell (20) and the at least partially reflective optical device (30).

5. A measuring system (100) according to one of claims 1 to 4, wherein the composition of the reference optical element (50) is selected as a function of said chemical component so that the first part of the Raman spectrum is distinct from the second part of the Raman spectrum.

6. Measuring system (100) according to one of claims 1 to 5, in which the reference optical element (50) is selected from the group comprising: plastic materials, crystalline materials, doped glasses.

7. Measuring system (100) according to one of claims 1 to 6, in which the reference optical element (50) is transparent and crossed by the first light beam (12) or the second light beam (14).

8. A measuring system (100) according to claim 7, wherein the reference optical element (50) is arranged to maintain the path of the first light beam (12) or the second light beam (14) through the reference optical element (50) rectilinear.

9. Measuring system (100) according to one of claims 7 and 8, in which the reference optical element (50) comprises one of the portholes (23, 24).

10. A measuring system (100) according to one of claims 7 to 9, wherein the reference optical element (50) comprises a gas or a liquid sealed in an enclosure (51).

11. Measuring system (100) according to one of claims 1 to 6, in which the reference optical element (50) is a non-transparent solid arranged on said optical device (30) and blocking only a portion of the first light beam (12).

12. Measuring system (100) according to one of claims 1 to 11, wherein the flowing fluid (200) is a gas, and wherein the calculation unit (60) is programmed to: • measure an effective concentration of each chemical component of the flowing fluid (200), • calculate a total concentration (CT) on the basis of a sum of each effective concentration, • correct at least one of said effective concentrations on the basis of the total concentration (CT).

13. The measuring system (100) of claim 12, wherein correcting said effective concentration comprises dividing said effective concentration by said total concentration (CT).

14. Measuring system (100) according to one of claims 1 to 13, wherein said chemical component is selected from water, nitrogen, hydrogen, oxygen, carbon dioxide, methane, carbon monoxide.

15. A method for measuring a concentration of at least one chemical component of a flowing fluid (200) comprising the following steps: - emitting an excitation light beam (11), - scattering and / or transmitting the excitation light beam (11) through the flowing fluid (200) so as to form a first light beam (12), - reflecting the first light beam (12) on an optical device (30) at least partially reflecting into a reflected light beam (13) in the direction of the flowing fluid (200) and scattering and / or transmitting the reflected light beam (13) through the flowing fluid (200) so as to form a second light beam (14); - generating, by a Raman spectrometer (45), a Raman spectrum on the base of the second light beam (14), - determination, on the basis of a first part (P3) of the Raman spectrum relating to a predetermined composition of a reference optical element (50) positioned on the optical path of one of said light beams (11, 12, 13, 14), of an adjustment value; and H determine, on the basis of a second part (PI, P2) of the Raman spectrum relating to said chemical component, an intermediate concentration of said chemical component, then calculate, on the basis of the intermediate concentration and the adjustment value, the effective concentration of said chemical component; Or H calculate, on the basis of the fitting value and the Raman spectrum, an adjusted Raman spectrum, and then determine, on the basis of a part of the adjusted Raman spectrum, the effective concentration of said chemical component.