MEASURING DEVICE AND METHOD FOR MEASURING THE HYDROGEN CONCENTRATION IN A GAS

Abstract

A measuring device and a method for measuring the hydrogen concentration in a gas. The measuring device for carrying out the method includes: an excitation light generator that transmits excitation light to a gas sample; a monochromator that provides a fraction of the Raman scattered light emitted by the illuminated sample to a measuring detector in order to determine a measured intensity of that fraction; and an evaluation unit that determines the hydrogen concentration as a linear function of the measured intensity. The fraction of Raman scattered light includes only light with wavelengths within a measurement wavelength range with a width of less than or equal to several nanometers and includes a measurement wavelength defined by a wavelength at which a Raman intensity spectrum of pure hydrogen gas exhibits a maximum.

Description

[0001] The present disclosure relates to a measuring device for measuring the hydrogen concentration contained in a gas and a method for its use.

[0002] Hydrogen in the gas phase is an important component of many chemical processes. For example, hydrogen is frequently used in fertilizer plants, refineries, and many other chemical facilities. The importance of hydrogen will continue to grow due to the increasing demand for it as an energy source, replacing fossil fuels to drastically reduce carbon dioxide emissions worldwide. To ensure safe and efficient processes using hydrogen, the hydrogen concentration of gases must be measured at one or more different stages of these processes.

[0003] Hydrogen concentration measurements can be performed, for example, using thermal conductivity detectors (TCDs), which are employed in gas chromatography for the analysis of inorganic gases. Thermal conductivity detectors measure the thermal conductivity of a gas between a heat source and a heat sink. The thermal conductivity of gases composed of multiple components depends on the thermal conductivities and concentrations of the individual components. Therefore, to determine the concentration of individual components based on the thermal conductivity of the gas, the thermal conductivities of the individual components must differ sufficiently. Consequently, thermal conductivity detectors exhibit low selectivity in distinguishing between gas components with similar thermal properties.Furthermore, changes in gas composition can negatively affect the measurement accuracy when measuring the concentration of individual components contained in the gas. Another problem is that the measurements are subject to drift and thermal disturbances, especially if the thermal conductivities of individual gas components exhibit different temperature dependencies.

[0004] Alternatively, solid-state sensors, such as capacitive or resistive solid-state sensors, can be used. In this case, the measurement of the hydrogen concentration is based on a change in an electrical property of a sensor element of the solid-state sensor, e.g., a capacitance or specific resistance of the sensor element, caused by an interaction of the hydrogen contained in the gas with the sensor element. Solid-state sensors offer higher selectivity than thermal conductivity detectors with respect to the influence of other components contained in the gas on the measurement accuracy of the hydrogen concentration. Unfortunately, solid-state sensors react slowly to changes in the hydrogen concentration to be measured. Another problem is that solid-state sensors are susceptible to contamination.For example, sensors containing palladium (Pd) for hydrogen adsorption can be contaminated by carbon monoxide (CO) or hydrogen sulfide (H2S) adsorbing onto the sensor element.

[0005] As another alternative, Raman spectroscopic measurement systems designed for gas analysis can be used to determine the hydrogen concentrations contained in gases. Raman spectroscopic measurement systems include a monochromatic light source that illuminates a gas sample and a spectrograph that scatters the Raman scattered light emitted by the sample into different wavelengths. Such systems further include a detector system that receives the scattered Raman scattered light and determines and provides Raman intensity spectra of the scattered light, and an evaluation unit that analyzes the Raman intensity spectra and determines the concentration of individual components of the sample based on a previously determined model. Raman spectrometric measurement systems are considerably more expensive than thermal conductivity detectors and solid-state sensors. They are also difficult to install.One of the reasons for this is that the model required to determine the concentrations of the individual gas components must be adapted to the specific application in which the measurement system is to be used, in a way that takes into account the influence of the background gas matrix of the gas being analyzed on the Raman intensity spectra. Accordingly, there is still a need for further contributions in this technical field.

[0006] For example, there is a need for an improved method for measuring hydrogen concentration in gases and / or a measuring device for carrying out such a method that can be manufactured more cost-effectively and / or installed more easily than conventional Raman spectrometric measurement systems. Another example is the need for a measuring device for hydrogen concentration in gases that has a shorter response time and / or is more robust, particularly less susceptible to contamination, than solid-state sensors and / or more selective than thermal conductivity detectors.

[0007] The present disclosure includes a measuring device for measuring a hydrogen concentration contained in a gas, wherein the measuring device includes the following: an excitation light generator that transmits excitation light to a sample of the gas, wherein the excitation light is configured to excite Raman scattering in the sample; a monochromator that receives light emanating from the sample and provides a fraction of the Raman scattered light contained in the light received by the monochromator, having wavelengths within a measurement wavelength range, wherein the measurement wavelength range includes a measurement wavelength given by a wavelength at which a Raman intensity spectrum of pure hydrogen gas exposed to the excitation light provided by the excitation light generator exhibits a maximum, and wherein the width of the measurement wavelength range is less than or equal to several nanometers, less than or equal to 5 nm, or less than or equal to 3 nm; a measurement detector that receives the fraction of Raman scattered light provided by the monochromator and determines and provides a measured intensity of the fraction of Raman scattered light; and an evaluation unit, which is connected to the measuring detector and is configured to determine the hydrogen concentration as a linear function of the measured intensity and to provide the hydrogen concentration.

[0008] The narrow measurement wavelength range, including the measurement wavelength, offers the advantage that the hydrogen concentration can be determined as a linear function of the measured intensity, and that the contribution of other components that may be present in the gas to the measured intensity is negligible. The resulting high selectivity allows the measuring device to be put into operation without requiring a detailed analysis of the gas composition at the measurement location. This enables the measuring device to be calibrated at the manufacturer and put into operation in a wide variety of applications using a plug-and-play procedure, particularly without the need for calibration measurements at the measurement location.

[0009] Another advantage is that detectors measuring the integral intensity of the incident light are inexpensive and exhibit short response times to changes in the intensity of the received light. This offers the benefit that the measuring device has short response times to changes in hydrogen concentration and can be manufactured at a significantly lower cost than conventional Raman spectroscopic measurement systems, which require resources for the acquisition and analysis of complete Raman intensity spectra.

[0010] According to a first embodiment, the monochromator includes a filter that receives the light emitted by the sample and filters out Raman scattered light contained in the light received by the filter, wherein the filter is a single- or multi-stage filter and / or includes a notch filter, an edge filter, a bandpass filter, and / or another type of filter element. In the first embodiment, the monochromator further includes a disperser that receives the Raman scattered light provided by the filter and scatters the Raman scattered light into light of different wavelengths, which propagates in wavelength-dependent directions.The disperser is, for example, a single- or multi-stage disperser and / or includes a grating, a diffraction grating, a reflecting grating, a holographic grating and / or another dispersing element, and the measuring detector is positioned to selectively receive the proportion of Raman scattered light scattered by the disperser.

[0011] In further embodiments, the measuring detector is a camera, a camera with an array of charge-coupled devices, a photodiode, a silicon photodiode, an avalanche photodiode, an avalanche silicon photodiode, or another type of detector configured to provide a measurement signal corresponding to a light intensity received by the detector; and / or the measuring detector has an active area of ​​1 mm². 2 - 2 mm 2 on.

[0012] The disclosure further includes an embodiment in which the linear function of the measured intensity is given by a sum of a product of a proportionality factor and a difference between the measured intensity and a reference intensity and an offset, wherein the proportionality factor, the reference intensity and / or the offset are each given by a constant which is determined during a calibration of the measuring device, and wherein the calibration includes calibration measurements which are carried out with the measuring device on reference samples with known hydrogen concentrations.

[0013] The disclosure further includes a second embodiment of the measuring device, which additionally comprises a reference detector connected to the evaluation unit. In the second embodiment The reference detector is a photodiode, a silicon photodiode, an avalanche photodiode, an avalanche silicon photodiode, or another type of detector configured to provide a measurement signal corresponding to a light intensity received by the detector; the reference detector is configured to determine and provide a reference intensity by determining the intensity of a fraction of the Raman scattered light contained in the light emanating from the sample, having wavelengths within a limited reference wavelength range, wherein Raman intensity spectra of the Raman scattered light emanating from the sample exhibit a constant baseline intensity; the evaluation unit is configured to determine the hydrogen concentration based on the measured intensity provided by the measurement detector and the reference intensity provided by the reference detector;and the linear function of the measured intensity is a linear function of the difference between the measured intensity and the reference intensity determined by the reference detector.

[0014] In certain embodiments according to the first and second embodiments, the reference detector is positioned such that it selectively receives the portion of the Raman scattered light scattered by the disperser that has wavelengths in the limited reference wavelength range.

[0015] The disclosure further includes a third embodiment, wherein the measuring device further comprises a monitoring detector configured to determine and provide a monitored intensity corresponding to an intensity of light emanating from the sample, and wherein the monitoring detector is a photodiode, a silicon photodiode, an avalanche photodiode, an avalanche silicon photodiode or another type of detector configured to provide a measurement signal corresponding to an intensity of light received by the detector.

[0016] In certain embodiments of the measuring device according to the third embodiment, a beam splitter is inserted between the sample and the monochromator, configured to split the incident light emanating from the sample into a major portion that is transmitted to the monochromator and a minor portion that is transmitted to the monitoring detector; or the monochromator includes a filter that receives the light emanating from the sample, the filter being configured as a beam splitter that splits the incident light emanating from the sample into a first portion, which is given by Raman scattering light and is transmitted through the filter, and a second portion that is reflected from the filter to the monitoring detector.

[0017] In a further embodiment of the measurement according to the third embodiment, the monitoring detector is connected to the evaluation unit; the evaluation unit is configured to determine the hydrogen concentration based on the measured intensity provided by the measuring detector and the monitored intensity provided by the monitoring detector; the linear function results from the sum of a product of a proportionality factor and a difference between the measured intensity and a reference intensity and an offset added to the product; the proportionality factor is inversely proportional to the intensity of the light emitted by the sample, which corresponds to the monitored intensity provided by the monitoring detector;and the reference intensity is either given by a constant or is determined and provided by a reference detector of the measuring device, which is configured to determine and provide the reference intensity by determining an intensity of a fraction of the Raman scattered light contained in the light emanating from the sample and having wavelengths within a limited reference wavelength range, wherein Raman intensity spectra of the Raman scattered light emanating from the sample have a constant baseline intensity.

[0018] The disclosure further includes a fourth embodiment of the measuring device, which further comprises an excitation detector configured to detect and provide an excitation intensity corresponding to the excitation intensity of the excitation light transmitted by the excitation light generator. In the fourth embodiment, the excitation detector is a photodiode, a silicon photodiode, an avalanche photodiode, an avalanche silicon photodiode, or another type of detector configured to provide a measurement signal corresponding to the light intensity received by the detector. Additionally or alternatively, the excitation detector is incorporated within the excitation light generator, or a beam splitter is inserted between the excitation light generator and the sample.In the latter case, the beam splitter is configured to split the incident excitation light into a main component that is transferred to the sample and a secondary component that is transferred to the excitation detector.

[0019] In certain embodiments, the measuring device further comprises a control unit that is contained in or connected to the excitation light generator. These embodiments include embodiments in which the control unit is connected to an excitation detector that detects and provides an excitation intensity corresponding to the excitation intensity of the excitation light transmitted by the excitation light generator, and the control unit is configured to regulate and / or control the excitation intensity transmitted by the excitation light generator based on the excitation intensity provided by the excitation detector; and / or embodiments in which the control unit is connected to a monitoring detector that detects and provides a monitored intensity corresponding to the intensity of the light emitted by the sample, and wherein the control unit is configured toto regulate and / or control the excitation intensity transmitted by the excitation light generator based on the monitored intensity provided by the monitoring detector, and / or to increase the excitation intensity transmitted by the excitation light generator when the monitored intensity decreases, and / or to decrease the excitation intensity transmitted by the excitation light generator when the monitored intensity increases. Certain embodiments of the measuring device according to the third and fourth embodiments further include a monitoring unit connected to the excitation detector and the monitoring detector. In these embodiments, the monitoring unit is configured to determine, monitor, and / or provide a sample efficiency of the sample based on a ratio of the monitored intensity provided by the monitoring detector and the excitation intensity provided by the excitation detector, and to issue a warning.if the sample efficiency deviates by more than a predetermined threshold from an initial efficiency determined at an initial time point, and / or to issue an alarm if the sample efficiency falls below a predetermined minimum efficiency.

[0020] In certain embodiments, the measuring wavelength is given by the wavelength at which the Raman intensity spectrum of pure hydrogen gas exposed to the excitation light provided by the excitation light generator exhibits its absolute maximum; and / or the measuring wavelength is given by a wavelength corresponding to a Raman wavenumber shift of 592 cm⁻¹. -1 corresponds.

[0021] In other embodiments, the measurement wavelength is given by a wavelength at which the Raman intensity spectrum of pure hydrogen gas exposed to the excitation light provided by the excitation light generator has a relative maximum, or a relative maximum that is predetermined such that a wavelength range around the relative maximum, in which contributions of several components that may be present in the sample in addition to hydrogen to the spectral intensities of a Raman spectrum of the sample are negligible or zero, is wider than a wavelength range around the absolute maximum of the Raman intensity spectrum of pure hydrogen gas, in which the contributions of the several components are negligible or zero.

[0022] In a fifth embodiment, the measuring wavelength is given by a wavelength corresponding to a Raman wavenumber shift of 4152 cm⁻¹. -1This corresponds to certain embodiments according to the fifth embodiment, the range of the measurement wavelength range is 3 nm to 5 nm.

[0023] In some embodiments, the measuring device further comprises a Raman signal amplifier with an optical element which focuses the excitation light onto a first focusing point in the sample, and a mirror arrangement with at least one focusing mirror which is arranged and configured to reflect incident light and focus it onto a focusing point associated with the respective mirror, such that the excitation light and the Raman scattered light resulting from interactions of the excitation light with the sample are reflected back into the sample at least once or several times before the light emanating from the sample via one of the focusing points is received and passed on to the monochromator.

[0024] In certain embodiments, the excitation light generator includes a laser, a gas laser, a laser diode, or another type of monochromatic light source, wherein the excitation light is monochromatic light with an excitation wavelength in the range of 250 nm to 1000 nm or in the range of 350 nm to 450 nm, the excitation light generator includes a pulsed laser, and a lock-in amplifier is connected to a signal output of the measuring detector and configured to provide the measured intensity based on a measurement signal provided by the measuring detector and a reference signal provided by the excitation light generator, and / or the sample is contained in a measuring cell, or a measuring cell is given by a flow cell that includes at least one transparent window through which the excitation light can enter the measuring cell and the light emanating from the sample can exit the measuring cell.The present disclosure further includes a method for measuring a hydrogen concentration in a gas, wherein the method comprises transmitting excitation light to a sample of the gas, wherein the excitation light is configured to excite Raman scattering in the sample, and measuring a measured intensity of a fraction of the Raman scattered light emanating from the illuminated sample, wherein the fraction of Raman scattered light includes only wavelengths occurring in a measurement wavelength range, the width of the measurement wavelength range being less than or equal to several nanometers, less than or equal to 5 nm or less than or equal to 3 nm, and the measurement wavelength range including a measurement wavelength given by a wavelength corresponding to a Raman wavenumber shift of 4152 cm⁻¹. -1 This corresponds to a wavelength that corresponds to a Raman wavenumber shift of 592 cm⁻¹. -1This corresponds to, or is determined by, a wavelength at which a Raman intensity spectrum of pure hydrogen gas exposed to the excitation light exhibits maximum intensity. This method further includes determining the hydrogen concentration as a linear function of the measured intensity and providing the hydrogen concentration.

[0025] The described embodiments and other features, advantages and disclosures contained herein, and the manner in which they are achieved, will become clearer by reference to the following description of various embodiments of the present disclosure in conjunction with the accompanying drawings, and the present disclosure will be more readily understood, wherein: Fig. 1 shows a block diagram of a measuring device according to the present disclosure; Fig. 2 an embodiment of the in Fig. The measuring device shown in 1 shows; Fig. 3 another embodiment of the in Fig. 1 measuring device shown, including a Raman signal amplifier; Fig. 4 shows another embodiment of a Raman signal amplifier; Fig. 5 shows a representative Raman intensity spectrum of a gas; Fig. Six Raman intensity spectra of pure nitrogen, pure carbon dioxide, pure methane, and pure hydrogen are shown; and Fig. 7 shows a process according to the present disclosure.

[0026] The present disclosure includes a measuring device 100 for measuring a hydrogen concentration C contained in a gas. A block diagram of the measuring device 100 is shown in Fig. 1 shown.

[0027] The measuring device 100 includes an excitation light generator 1 that transmits excitation light L0 to a gas sample 3. The excitation light generator 1 includes, for example, a laser, such as a laser diode or a gas laser, or another type of light source that provides excitation light L0 selected to excite Raman scattering in the sample 3. In at least one embodiment, the excitation light L0 is monochromatic light with an excitation wavelength λ0 in the range of 250 nm to 1000 nm, e.g., an excitation wavelength λ0 in the range of 350 nm to 450 nm, or, for example, an excitation wavelength λ0 of 405 nm.Monochromatic light in this range offers the advantage that the excitation wavelength λ0 is long enough to reduce or even eliminate the excitation of fluorescence that interferes with Raman spectroscopic measurements, for example, fluorescence of impurities in a measuring cell containing sample 3 and / or of transparent windows in a container containing sample 3, and short enough to ensure a high ratio of the signal strength of the Raman scattered light to the excitation power.

[0028] The measuring device 100 can further include a monochromator 5 which receives the light L1 emanating from the sample 3 and provides a fraction L2 of the Raman scattered light contained in the light L1 received by the monochromator 5 and wavelengths in a limited measurement wavelength range Δλ m exhibits the following: The measurement wavelength range Δλ mIt can have a bandwidth of several nanometers or less, e.g., a bandwidth of 5 nm or less, or a bandwidth of 3 nm or less. Furthermore, the measurement wavelength range Δλ includes m a measurement wavelength λ m a, given by a wavelength at which a Raman intensity spectrum of pure hydrogen gas exposed to the excitation light L0 provided by the excitation light generator 1 has a maximum.

[0029] The measuring device 100 further includes a measuring detector Dm which receives the fraction L2 of the Raman scattered light provided by the monochromator 5 and measures an intensity S H2The L2 fraction of the Raman scattered light is determined and provided. In certain embodiments, the measuring detector Dm can be, for example, a camera, such as a camera with an array of charge-coupled devices, a photodiode, such as a silicon photodiode, an avalanche photodiode, such as an avalanche silicon photodiode, or another type of detector configured to provide a measurement signal corresponding to the light intensity received by the detector.

[0030] The measurement wavelength range Δλ m including the measurement wavelength λ m The wavelength is chosen to ensure that the measuring detector Dm receives a significant amount of the Raman scattered light that has been Raman-scattered by the hydrogen molecules contained in sample 3. At the same time, due to the relatively narrow width of the measurement wavelength range Δλ, mThe measurement is highly selective. This selectivity offers the advantage that the contribution of Raman scattered light, which has been Raman-scattered by other components that may be present in sample 3 in addition to hydrogen, to the measured intensity S is taken into account. H2 is negligibly small. The wavelength-selective determination of the measured intensity S H2 The detection of Raman scattering light from hydrogen molecules enables the determination of the hydrogen concentration C without the need to record Raman intensity spectra over a wide wavelength range, as is generally required with conventional Raman spectroscopic analyzers, and without the need to establish an application-specific model for determining the hydrogen concentration based on the spectral intensities of these Raman intensity spectra at several different wavelengths.

[0031] The measuring device 100 can further include an evaluation unit 7 which is connected to the measuring detector Dm and is configured to measure the hydrogen concentration C contained in the sample 3 as a linear function f(S) H2 ) of the measured intensity S H2 , which is determined and provided by the measuring detector Dm, and to provide the concentration C thus determined.

[0032] The measuring device of the present disclosure provides the aforementioned advantages. Individual components of the measuring device 100 can be implemented in different ways without deviating from the scope of protection of the present disclosure. Various optional embodiments are described in more detail below.

[0033] For example, in certain embodiments, the excitation light generator 1 includes a pulsed laser that transmits excitation light pulses. In such an embodiment, the measuring device 100 additionally includes a lock-in amplifier 9, which is connected to a signal output of the measuring detector Dm and measures the intensity S. H2 based on a measurement signal provided by the measurement detector Dm and a reference signal provided by the excitation light generator 1. The combination of the pulsed laser with the lock-in amplifier 9 offers the advantage of an improved signal-to-noise ratio.

[0034] Additionally or alternatively, the Monochromator 5 can be implemented in different ways. Fig. Figure 2 shows an embodiment of a measuring device 200 in which the monochromator 5 includes a filter 11 and a disperser 13. The filter 11 is configured to receive the light L1 emitted by the sample 3 along a receiving path and to filter out the Raman scattered light LR contained in the light L1 received by the filter 11. In certain embodiments, the filter 11 can, for example, be a single-stage or multi-stage filter and / or include a notch filter, an edge filter, a bandpass filter, and / or another type of filter element. In certain embodiments, the filter 11 can, for example, be a notch filter with a filter area that defines the measurement wavelength λ. m excludes. As an example, in combination with an excitation light generator 1, which emits monochromatic excitation light L0 with an excitation wavelength λ0 of 405 nm and a measurement wavelength λ mA notch filter with a center wavelength of 405 nm and / or a full width at half maximum (FWHM) of 13 nm can be used to produce a wavelength of 487 nm.

[0035] The disperser 13 receives the Raman scattered light LR provided to the disperser 13 by the filter 11, e.g., transmitted light, and disperses the received Raman scattered light LR into light of different wavelengths, which propagates in wavelength-dependent directions. In certain embodiments, the disperser 13 can, for example, be a single-stage or multi-stage disperser and / or include a grating, for example, a diffraction grating, a reflecting grating, or a holographic grating, and / or another type of dispersing element.

[0036] In Fig. 2 the measuring detector Dm is positioned so that it selectively receives the fraction L2 of the scattered Raman scattered light LR, which consists exclusively of wavelengths in the limited measurement wavelength range Δλ mincludes.

[0037] In certain embodiments, the measuring detector Dm can be a photodiode, e.g. a silicon photodiode, an avalanche photodiode, e.g. an avalanche silicon photodiode, or another detector type with a small active area, e.g. an active area of ​​1 mm². 2 - 2 mm 2 This size of the active area offers the advantage that the wavelength range of the scattered Raman scattered light LR received by the active area is limited to the narrow measurement wavelength range Δλ. mThe range can be limited simply by appropriately positioning the measuring detector Dm, without requiring a large distance between the disperser 13 and the measuring detector Dm. The latter enables a particularly compact design of the measuring device 200. Additionally or alternatively, the measuring device 100, 200 can, in certain embodiments, include at least one optical element, e.g., a mirror, a lens, a beam combiner, and / or another type of optical element. Fig. Figure 2 illustrates an example where the optical elements include a focusing lens 15, which focuses the excitation light L0 transmitted from the excitation light generator 1 onto the sample 3, and / or a converging lens 17, which collects the light L1 emitted from the sample 3. The focusing lens 15 is arranged in the signal transmission path between the excitation light generator 1 and the sample 3. The converging lens 17 is arranged in the signal reception path between the sample 3 and the monochromator 5.

[0038] In certain embodiments, the sample 3 can be contained in a measuring cell 19.

[0039] Fig. Figure 2 shows an example where the measuring cell 19 is a flow cell that includes an inlet 21 for connection to a supply line providing gas to the flow cell and an outlet 23 for connection to a drain line that discharges the gas from the flow cell. In further embodiments, the measuring cell 19 can be a different type of measuring cell that contains the sample 3 and enables the transmission of the excitation light L0 into the sample 3 and the reception of the light L1 emitted by the sample 3.

[0040] In the Fig. 1 and Fig. In the embodiments shown in Figure 2, the excitation light generator 1 and the monochromator 5 are arranged on opposite sides of the sample 3. In such an embodiment, the measuring cell 19 includes a transparent window 25 on the side of the excitation light generator 1, through which the excitation light L0 emitted by the excitation light generator 1 enters the measuring cell 19, and a transparent window 25 on the side of the monochromator 5, through which the light L1 emanating from the sample 3 leaves the measuring cell 19.

[0041] In alternative embodiments, the excitation light generator 1 and the monochromator 5 can be positioned on the same side of the sample 3. An example of a corresponding measuring device 300 is shown in Fig. Figure 3 shows that in such an embodiment, the excitation light generator 1 can transmit the excitation light L0 to a mirror 27, which reflects the excitation light L0 onto a beam combiner 29. The beam combiner 29 directs the excitation light L0 along a counter-extending path F to an optical element 31, which focuses the excitation light L0 onto the sample 3 and collects the light L1 emitted from the sample 3. The beam combiner 29 is configured to transmit the light L1 emitted from the sample 3 along the counter-extending path F to the monochromator 5 and to provide the portion L2 of the Raman scattered light to the measuring detector Dm. As shown in Figure 3, the excitation light generator 1 can transmit the excitation light L0 to a mirror 27, which reflects the excitation light L0 onto a beam combiner 29. The beam combiner 29 is configured to transmit the light L1 emitted from the sample 3 along the counter-extending path F to the monochromator 5 and to provide the portion L2 of the Raman scattered light to the measuring detector Dm. Fig. In the embodiment shown in 2, the monochromator 5 of the Fig. The measuring device 300 shown in Figure 3 includes the filter 11 and the disperser 13. In such an embodiment, the measuring detector Dm is again positioned such that it selectively detects the fraction L2 of the Raman scattered light LR with a wavelength in the measurement wavelength range Δλ. m receives. Positioning the excitation light generator 1 and the monochromator 5 on the same side of the sample 3 offers the advantage that the sample 3 can be contained in a measuring cell 33, e.g. a flow cell, which includes only a single transparent window 25 through which the excitation light L0 is transmitted into the sample 3 and through which the light L1 emanating from the sample 3 leaves the measuring cell 33.

[0042] As a further alternative, in certain embodiments the excitation light generator 1 and the monochromator 5 can be positioned such that the monochromator 5 receives the light L1 emanating from the sample 3 along a receiving path that runs perpendicular to a transmission path along which the excitation light L0 is transmitted to the sample 3.

[0043] Regardless of the positioning of the excitation light generator 1 and the monochromator 5, the free propagation of the excitation light L0 and the light L1 emanating from the sample 3 offers the advantage that the optical elements used in the measuring device 100, 200, 300 can be arranged compactly. Examples of suitable optical elements are, for instance, those described in Fig. 2 the focusing lens 15 and the converging lens 17 shown, as well as the one in Fig. The mirrors 27, the beam combiner 29 and the optical element 31 shown. Free propagation also offers the advantage that the sample volume of sample 3 can be relatively small.

[0044] In certain embodiments, the measuring device 300 includes, for example, a Raman signal amplifier that improves the excitation efficiency of the excitation light L0, which excites the Raman scattering, and the collection efficiency of the resulting Raman scattered light LR. In such embodiments, Raman signal amplifiers disclosed in US 2014 / 0036347 A1 and US 2008 / 0180663 A1, which are hereby incorporated by reference, may be used.Such Raman signal amplifiers include an optical element that focuses the excitation light onto a first focusing point in the sample, and a mirror arrangement that includes at least one focusing mirror that reflects incident light, including the excitation light and the Raman scattered light resulting from an interaction of the excitation light with the sample, and focuses it onto a focusing point in the sample associated with the respective mirror. Fig. Figure 3 illustrates an example in which the Raman signal amplifier includes the optical element 31, which focuses the excitation light L0 onto the first focusing point P1 in the sample 3, and a mirror arrangement which, in the illustrated embodiment, includes only one focusing mirror 35. In this example, the focusing point associated with the focusing mirror 35 is given by the first focusing point P1, and the light L1 emanating from the sample 3 is received via the optical element 31.

[0045] Fig. Figure 4 shows another example of a Raman signal amplifier suitable for an embodiment of the measuring device 300, wherein the optical element 31 focuses the excitation light L0 onto the first focusing point P1 in the sample 3 and the mirror arrangement includes several focusing mirrors 37, 39, 41, which are arranged and configured to reflect and focus incident light onto the focusing points P1, P2 associated with the respective mirror 37, 39, 41, such that the excitation light L0 and the Raman scattered light resulting from the interaction of the excitation light L0 with the sample 3 are reflected back into the sample 3 several times before the light L1 emanating from the sample 3 is received via one of the focusing points P1 and passed on to the monochromator 5. Fig. For example, the light L1 emanating from sample 3 is received by the optical element 31 via the first focusing point P1.

[0046] As mentioned above, the hydrogen concentration C can be expressed as a linear function f(S). H2 ) of the measured intensity S H2 , which is measured by the measuring detector Dm. As an example, in certain embodiments the linear function f(S) H2 ) for example, given by a sum of a product of a proportionality factor A and a difference between the measured intensity S H2 and a reference intensity S ref and an offset B added to the product. In such an embodiment, the hydrogen concentration C is given by: C:= f(S H2 ) = A (S H2 - S ref ) + B.

[0047] In certain embodiments, the proportionality factor A and the reference intensity S are refand / or the offset B, for example, is each given by a constant. In such an embodiment, the constant values ​​of the proportionality factor A and the reference intensity S are ref and / or the offset B is determined, for example, during a calibration of the measuring device 100, 200, 300, for example a calibration which includes calibration measurements carried out with the measuring device 100, 200, 300 on reference samples 3 which contain known hydrogen concentrations.

[0048] The reference intensity S ref This corresponds, for example, to a baseline intensity I ref of the Raman spectrum of the Raman scattered light LR contained in the light L1 emanating from sample 3. This is shown in Fig. Figure 5 illustrates an example of a Raman intensity spectrum I(λ). S ) of a gas containing hydrogen and other components as a function of wavelength λ Sof the Raman scattered light LR in a wavelength range that corresponds to the measurement wavelength range Δλ m includes, shows. As in Fig. As shown in Figure 5, the complete Raman intensity spectrum I(λ) exhibits S ) individual peaks caused by Raman scattering, whose maximum intensities exceed the baseline intensity I ref exceed. Under normal operating conditions, the reference intensity S ref mainly due to noise, and can therefore be assumed to be constant in a large number of applications where the measuring device 100, 200, 300 can be used. However, in certain applications, the reference intensity S may be ref changes during the operating time of the measuring device 100, 200, 300. To give an example: changes in the reference intensity S refcan be caused by fluorescence, for example by fluorescence of deposits that form on the window(s) 25 of the measuring cell 19, 33.

[0049] Thus, in at least one embodiment according to the present disclosure, the measuring device 200, 300 additionally includes, for example, a reference detector Dref, which is connected to the evaluation unit 7 and is configured to measure the reference intensity S ref to determine and provide. In such an embodiment, the reference detector Dref is configured, for example, to determine and provide the reference intensity S. ref to determine by determining the intensity of a fraction L3 of the Raman scattered light LR contained in the light L1 emanating from sample 3 and wavelengths in a reference wavelength range Δλ ref exhibits the Raman intensity spectrum I(λ) S ) of the Raman scattered light LR the constant baseline intensity I refexhibits. A corresponding example for the reference wavelength range Δλ. ref is in Fig. 5 shown.

[0050] The width of the reference wavelength range Δλ ref can be identical or at least approximately identical to the width of the measurement wavelength range Δλ m be. In this case, the reference intensity S ref for example, by the intensity measured by the reference detector Dref. In certain embodiments, the reference intensity S ref e.g. as the product of the intensity measured by the reference detector Dref and a factor that corresponds to the ratio of the width of the reference wavelength range Δλ ref and the width of the measurement wavelength range Δλ m can be determined.

[0051] To determine the reference intensity S ref by means of the reference detector Dref, the one in the Fig. 2 and Fig. The monochromator 5 shown, including the filter 11 and disperser 13, has the advantage that the reference detector Dref is as shown in the Fig. 2 and Fig. 3 shown can be positioned so that it selectively filters the fraction L3 of the Raman scattered light LR scattered by the disperser 13 with wavelengths in the limited reference wavelength range Δλ ref receives the Raman intensity spectrum I(λ). s ) sample 3 shows no peaks.

[0052] In certain embodiments, the reference detector Dref is, for example, a photodiode, such as a silicon photodiode, an avalanche photodiode, such as an avalanche silicon photodiode, or another type of detector configured to provide a measurement signal corresponding to the light intensity received by the detector. In embodiments with the reference detector Dref, the evaluation unit 7 is, for example, configured to determine the hydrogen concentration C based on the measured intensity S. H2 to determine the measured detector Dm and the reference intensity S ref is determined by the reference detector Dref, e.g. based on a difference between the measured intensity S H2 and the reference intensity S ref is determined. In such an embodiment, the linear function f(S) H2 ) of the measured intensity S H2 for example a linear function f(S) H2- S ref ) the difference between the measured intensity S H2 and the reference intensity S ref Determining the hydrogen concentration C based on this difference offers the advantage that changes in the reference intensity S ref Factors that may occur during the operation of the measuring device 200, 300 are taken into account. This results in higher long-term stability of the measurement accuracy.

[0053] The measured intensity S H2 depends not only on the hydrogen concentration C in sample 3, but also on an excitation intensity I0 of the excitation light L0 provided by the excitation signal generator 1 and a sample efficiency η of the sample volume of sample 3.

[0054] In certain embodiments, the sample efficiency η is defined, for example, as a ratio of the intensity I1 of the light L1 emanating from sample 3 to the excitation intensity I0 of the excitation light L0, e.g., by η := I1 / I0. The dependence of the measured intensity S H2 The excitation intensity I0 of the excitation light and the sample efficiency η can be taken into account in various ways.

[0055] One approach is to assume that the excitation intensity I0 and the sample efficiency η are both at least approximately constant. In such an embodiment, the proportionality factor A and the offset B of the linear function f(S) are H2The parameters used to determine the hydrogen concentration C are both given by constants that can be determined, for example, as described above. This approach offers the advantage that it can be implemented without the measuring device needing to contain 100, 200, or 300 additional detection elements.

[0056] Another approach is to define the proportionality factor A as a product of a constant first factor A1, a second factor A2 that accounts for the sample efficiency η, and a third factor A3 that accounts for the excitation intensity I0. The second factor A2, which accounts for the sample efficiency η, is defined, for example, as a ratio of an initial value of the sample efficiency η(t0) at an initial time t0, e.g., during the calibration of measuring device 100, 200, 300, and a current value of the sample efficiency η(t) at a current time t, e.g., by A2 := η(t0) / η(t).

[0057] The third factor A3, which takes into account the excitation intensity I0, is defined, for example, as a ratio of an initial value of the excitation intensity I0(t0) at the initial time t0 and a current value of the excitation intensity I0(t) at the current time t, e.g. by A3:= I0(t0) / I0(t).

[0058] Based on these definitions, the proportionality factor A is calculated as follows: A:=A1⋅η(t0) / η(t)⋅I0(t0) / I0(t).

[0059] By replacing the sample efficiency η(to) at the initial time t0 and the sample efficiency η(t) at the current time t with the corresponding intensity ratios, given by η(t0):= I1(t0) / I0(t0) and η(t):= I1(t) / I0(t), the dependence of the proportionality factor A on the excitation intensity I0 is eliminated and the proportionality factor A is reduced to: A:=A1⋅I1(t0) / I1(t).

[0060] Considering that the first factor A1 and the intensity I1(t0) of the light L1 emanating from sample 3 at the initial time t0 are both constants, this representation of the proportionality factor A shows that changes in the excitation intensity I0 and the sample efficiency η can be taken into account simultaneously on the basis of a single additional measurement of the intensity I1(t) of the light L1 emanating from sample 3 at the current time t.

[0061] In embodiments of the present disclosure in which this approach is implemented, the measuring device 200, 300 can include a monitoring detector D1 configured to monitor an intensity I mto determine and provide the intensity I1(t) of the light L1 currently emitted from sample 3. In these embodiments, the monitoring detector D1 is connected to the evaluation unit 7, and the evaluation unit 7 is configured to determine the hydrogen concentration C based on the measured intensity S. H2 and the monitored intensity I provided by the monitoring detector D1 m to determine. In such an embodiment, the hydrogen concentration C is determined, for example, by: C:= A1 · I1(t0) / I1(t) - (S H2 - S ref ) + B, where the intensity I1(t) of the light L1 currently emanating from sample 3 is, for example, the product of a constant factor and the monitored intensity I m is determined, which is determined and provided by the monitoring detector D1, and wherein the reference intensity S refeither given by a constant or determined by the reference detector Dref and provided to the evaluation unit 7. Considering that the initial intensity I1(t0) of the light L1 emanating from sample 3 is a constant, the proportionality factor A is inversely proportional to the intensity I1(t) of the light L1 emanating from sample 3, which is the monitored intensity I provided by the monitoring detector D1. m corresponds.

[0062] In certain embodiments, the monitoring detector Dm is, for example, a photodiode, such as a silicon photodiode, an avalanche photodiode, such as an avalanche silicon photodiode, or another type of detector configured to provide a measurement signal corresponding to the light intensity received by the detector.

[0063] Fig. Figure 2 shows an embodiment in which a beam splitter 43 is inserted in the receiving path between the sample 3 and the monochromator 5. The beam splitter 43 divides the incident light L1 into a main component, which is transmitted to the monochromator 5, and a secondary component, which is transmitted to the monitoring detector D1, which measures the monitored intensity I. m of the light received by the monitoring detector D1 is determined and provided.

[0064] Fig. Figure 3 shows a further embodiment in which the filter 11 of the monochromator 5 is configured as a beam splitter, which divides the incident light into a first component containing the Raman scattered light LR, which is transmitted through the filter 11 to the disperser 13, and a second component, which is reflected from the filter 11 to the monitoring detector D1. This embodiment differs from the one shown in Fig. 2 embodiment shown in that the monitoring detector D1 does not receive the first component, including the Raman scattered light LR transmitted by the filter 11.

[0065] This leads to a measurement error in the intensity I1(t) of the light L1 emanating from sample 3 on the order of magnitude corresponding to the intensity of the Raman scattered light LR transmitted through filter 11. Considering that the intensity of the Raman scattered light LR emanating from sample 3 is significantly smaller than the intensity of all other components of the light L1 emanating from sample 3, especially the excitation light L0 contained within the light L1 emanating from sample 3, this measurement error is negligible. At the same time, using filter 11 as a beam splitter offers the advantage that the interference caused by the Fig. The signal losses caused by the additional beam splitter 43 shown in the diagram are avoided, which also reduce the intensity of the portion L2 of the Raman scattered light LR received by the measuring detector Dm.

[0066] Determining the hydrogen concentration C based on the monitored intensity I mThis offers the advantage of improved measurement accuracy of the hydrogen concentration C, as changes in excitation intensity I0 and sample efficiency η that may occur during operation of the measuring device 200, 300 are taken into account. This consideration is particularly advantageous in applications where the sample efficiency η can vary, for example, due to changes in the amount of excitation light L0 and / or the amount of Raman scattered light LR absorbed by the sample 3, and / or due to deposits that form on the window(s) 25 of the measuring cell 21, 33, which can reduce the transmittance of the window(s) 25.

[0067] In certain embodiments, the measuring device 200 can include a control unit 47, which is contained in or connected to the excitation light generator 1 and is connected to the monitoring detector D1. The control unit 47 is configured, for example, to regulate and / or control the excitation intensity I0 transmitted by the excitation light generator 1, based on the monitored intensity I. m , which is detected and provided by the monitoring detector D1. In such an embodiment, the control unit 47 is configured, for example, to increase the excitation intensity I0 transmitted by the excitation light generator 1 when the monitored intensity I m decreases and vice versa. This offers the advantage that fluctuations in the intensity I1(t) of the light L1 emitted by sample 3 are minimized.

[0068] In certain embodiments, the measuring device 200 may additionally include an excitation detector D0 configured to detect an excitation intensity I ex to determine and provide which corresponds to the current excitation intensity I0(t) of the excitation light L0 transmitted by the excitation light generator 1.

[0069] Fig. Figure 2 shows an embodiment in which a beam splitter 45 is inserted into the transmission path between the excitation light generator 1 and the sample 3. The beam splitter 45 divides the incident excitation light L0 into a main component, which is transmitted to the sample 3, and a secondary component, which is transmitted to the excitation detector D0, which determines the excitation intensity I. ex The excitation detector D0 determines and provides an intensity corresponding to the spurious component received by the excitation detector D0. In other embodiments, the excitation detector D0 can be contained within the excitation light generator 1.

[0070] Regardless of the position of the excitation detector D0, in certain embodiments the excitation detector D0 may be a photodiode, a silicon photodiode, an avalanche photodiode, an avalanche silicon photodiode or another type of detector configured to provide a measurement signal corresponding to the light intensity received by the detector.

[0071] The excitation intensity I ex The excitation intensity I0, determined by the excitation detector D0, can be used in one or more ways. In certain embodiments, for example, the measuring device 200 includes the control unit 47, which is connected to the excitation detector D0 and configured to regulate and / or control the excitation intensity I0 transmitted by the excitation light generator 1, based on the excitation intensity I. ex, which is determined and provided by the excitation detector D0. This regulation and / or control offers the advantage that fluctuations in the excitation intensity I0(t) of the excitation light L0 are minimized.

[0072] In embodiments that include the excitation detector D0 and the monitoring detector D1, the control unit 47 can be connected to and configured with the excitation detector D0 to regulate and / or control the excitation intensity I0 based on the excitation intensity I ex , as described above, and / or be connected to and configured with the monitoring detector D1 to regulate and / or control the excitation intensity I0, based on the monitored intensity I m , as described above.

[0073] Additionally or alternatively, in certain embodiments, the measuring device 200 includes, for example, a monitoring unit 49 connected to the excitation detector D0 and the monitoring detector D1. The monitoring unit 49 is configured, for example, to determine, monitor, and / or provide the sample efficiency η of sample 3, based on a ratio of the monitored intensity I. m , which is provided by the monitoring detector D1, and the excitation intensity I ex, which is provided by the excitation detector D0. Additionally or alternatively, the monitoring unit 49 is configured, for example, to issue a warning if the sample efficiency η determined by the monitoring unit 49 deviates from the initial efficiency η(t0), which is determined at the initial time t0, for example during the calibration of the measuring device 200, by more than a predetermined threshold, and / or configured to issue an alarm if the sample efficiency η determined by the monitoring unit 49 falls below a predetermined minimum efficiency.

[0074] Monitoring the sample efficiency η offers the advantage that changes in sample quality as well as impairments of the measuring cell 19, 33 containing the sample 3, for example contamination of the transparent window(s) 25 and / or deposits on the measuring cell 19, 33, which impair the sample efficiency η and thus also the hydrogen concentration measurement, can be detected early and appropriate countermeasures can be initiated in a timely manner.

[0075] As mentioned above, the measurement wavelength λ m , which are in the measurement wavelength range Δλ mThe Raman intensity spectrum of pure hydrogen gas exposed to the excitation light L0 provided by excitation light generator 1 exhibits a maximum at a wavelength. Each maximum occurs at a peak position of a Raman peak contained in the Raman intensity spectrum of pure hydrogen gas and is specified, for example, by the Raman shift Δk associated with that peak position. Based on the definition of the Raman shift Δk, given by Δk := (1 / λ0 - 1 / λ s ), where λ0 is the excitation wavelength of the excitation light L0 and λ s Given that the wavelength of the Raman spectrum is , the wavelength at which the respective maximum occurs can be calculated based on the Raman shift Δk that is associated with the respective maximum.

[0076] The limited width of the measurement wavelength range Δλ m including the measurement wavelength λm For example, it is predetermined based on the spectral position of the maximum used, such that there is a spectral overlap between the measurement wavelength range Δλ. m and are minimized, negligible or zero in the spectral ranges where other components that may be present in sample 3 of the gas exhibit Raman bands.

[0077] In certain embodiments, the measuring wavelength λ m for example, given by the wavelength at which the Raman intensity spectrum of pure hydrogen gas exposed to the excitation light L0 provided by the excitation light generator 1 reaches its absolute maximum M abs (H2) exhibits the absolute maximum M abs (H2) occurs at a Raman wavenumber shift Δk of 592 cm⁻¹ -1 For example, in combination with the excitation light L0 with an excitation wavelength λ0 of 405 nm, the measurement wavelength λ m, corresponding to the absolute maximum M abs (H2) of the Raman intensity spectrum of pure hydrogen, given by 415 nm. Predetermining the measurement wavelength λ m , so that they have a Raman wavenumber shift Δk of 592 cm -1 corresponds to the value at which the Raman intensity spectrum of pure hydrogen gas reaches its absolute maximum M abs (H2) offers the advantage of correspondingly high measured intensities S H2 , which in turn results in a correspondingly high measurement resolution for the hydrogen concentration measurements.

[0078] In such embodiments, the width of the measurement wavelength range Δλ m For example, a relatively small predefined wavelength range, such as less than or equal to 3 nm. The narrow width of the measurement wavelength range Δλ mThis offers the advantage that the contribution of other components, e.g., carbon dioxide, carbon monoxide, ethane, propane, ammonia, methane, pentane, hexane, butane and / or nitrogen, which may be present in sample 3, to the measured intensity S is taken into account. H2 , which is measured by the measuring detector Dm, is negligibly small.

[0079] Alternatively, in certain embodiments the measuring wavelength λ m for example, given by a wavelength at which the Raman intensity spectrum of pure hydrogen gas exposed to the excitation light L0 provided by the excitation light generator 1 exhibits a relative maximum M rel (H2) exhibits.

[0080] In such embodiments, the relative maximum M rel (H2) and correspondingly the measurement wavelength λ m for example, predetermined such that a wavelength range around the relative maximum M rel(H2) around, in which contributions of several components that may be present in sample 3 in addition to hydrogen to spectral intensities of a Raman intensity spectrum of sample 3 are negligible or zero, wider than a wavelength range around the absolute maximum M abs(H2) is around, where the contributions of the multiple components are negligible or zero. In such an embodiment, the multiple components considered are, for example, components contained in the gas at a measurement location, for example, where the measuring device 100, 200, 300 is to be used. Alternatively, the multiple components are, for example, a predetermined selection of components commonly found in hydrogen-containing gases in several different applications. In such an embodiment, the selection of components includes, for example, carbon dioxide, carbon monoxide, ethane, propane, ammonia, methane, pentane, hexane, butane, and / or nitrogen.

[0081] Predetermining the measurement wavelength λ mSuch a setting, in which it is surrounded by a broad wavelength range where the contributions of the multiple components are negligible or zero, offers the advantage of achieving higher selectivity. Additionally or alternatively, due to the flexibility gained through this selection, a larger measurement wavelength range Δλ can be achieved. m e.g. a measurement wavelength range Δλ m with a width of less than or equal to 5 nm, for example, a width of 3 nm to 5 nm, can be used. The latter offers the advantage of increasing the maximum permissible manufacturing tolerances, which in turn reduces the manufacturing costs of the measuring device 100, 200, 300.

[0082] For example, in certain embodiments the measuring wavelength λ m for example, given by a wavelength corresponding to a Raman wavenumber shift Δk of 4152 cm -1 This corresponds to the Raman wavenumber shift Δk of 4152 cm⁻¹. -1lies far outside the wavenumber range normally covered by conventional Raman spectroscopic measurement systems, and offers the advantage that the distance between the relative maximum M rel (H2) and the next Raman peak, which is related to other components that may be present in the gas, is relatively very large. This aspect is discussed in Fig. Figure 6 illustrates the Raman intensity spectra of pure nitrogen, pure carbon dioxide, pure methane and pure hydrogen in a wavenumber shift range of 1000 cm⁻¹. -1 up to 4500 cm -1 shows, where the relative maximum M rel (H2) of the Raman intensity spectrum of pure hydrogen at the Raman wavenumber shift Δk of 4152 cm -1 is specified.

[0083] As described above in connection with the measuring devices 100, 200, 300, which perform hydrogen concentration measurements, the present disclosure also includes a method 700 for measuring a hydrogen concentration contained in a gas, as described in Fig. Figure 7 shows the procedure 700 comprising a step 710 for transferring excitation light L0 to the gas sample 3 and a step 720 for measuring the measured intensity S. H2 of the L2 fraction of Raman scattered light emanating from the illuminated sample 3. As explained above, the L2 fraction includes only wavelengths within the measurement wavelength range Δλ. m occur. Here too, the range width of the measurement wavelength range Δλ m smaller than or equal to several nanometers, smaller than or equal to 5 nm, or smaller than or equal to 3 nm, and the measurement wavelength range Δλ m The measurement wavelength λ is included. m, which is given by a wavelength corresponding to a Raman wavenumber shift of 4152 cm -1 This corresponds to a wavelength that corresponds to a Raman wavenumber shift of 592 cm⁻¹. -1 corresponds to, or by another wavelength at which the Raman intensity spectrum I(λ) S ) of pure hydrogen gas exposed to the excitation light L0 exhibits a maximum intensity. The method can further include a step 730 for determining the hydrogen concentration C as a linear function f(S) H2 ) the measured intensity and provision of the hydrogen concentration, as described in detail herein.

[0084] In certain embodiments, the method further includes, for example, at least one of the additional method steps that are performed by at least one of the measuring devices 100, 200, 300 described above in relation to the embodiments according to the present disclosure. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 2014 / 0036347 A1

[0044] US 2008 / 0180663 A1

[0044]

Claims

[1] Measuring device (100, 200, 300) for measuring a hydrogen concentration (C) contained in a gas, wherein the measuring device (100, 200, 300) comprises: an excitation light generator (1) configured to transmit excitation light (L0) to a sample (3) of the gas, wherein the excitation light (L0) is selected to excite Raman scattering in the sample (3); a monochromator (5) configured to receive the light (L1) emanating from the sample (3) and to provide a fraction (L2) of the Raman scattered light contained in the light (L1) received by the monochromator (5), wherein the fraction (L2) comprises wavelengths within a measurement wavelength range (Δλ) m ) exhibits, wherein the measurement wavelength range (Δλ m ) a measurement wavelength (λ m) includes a wavelength at which a Raman intensity spectrum of pure hydrogen gas exposed to the excitation light (L0) of the excitation light generator (1) has a maximum, and wherein a range width of the measurement wavelength range (Δλ) m ) less than or equal to 5 nm or less than or equal to 3 nm; a measuring detector (Dm) configured to receive the fraction (L2) of Raman scattered light provided by the monochromator (5) and to measure an intensity (S H2 ) to determine and provide the proportion (L2) of Raman scattered light; and an evaluation unit (7) connected to the measuring detector (Dm) and configured to measure the hydrogen concentration (C) as a linear function (f(S) H2 )) of the measured intensity (S H2 ) to determine and provide the hydrogen concentration (C). [2] Measuring device (100, 200, 300) according to claim 1, wherein the monochromator (5) includes: a filter (11) configured to receive the light (L1) emanating from the sample (3) and to filter Raman scattered light (LR) contained in the light (L1) received by the filter (11), wherein the filter (11) is a single-stage or multi-stage filter and / or includes a notch filter, an edge filter, a bandpass filter and / or another type of filter element; and a disperser (13) configured to receive the Raman scattered light (LR) provided by the filter (11) and to disperse the Raman scattered light (LR) into light of different wavelengths, which propagates in wavelength-dependent directions, wherein the disperser (13) is a single- or multi-stage disperser and / or includes a grating, a diffraction grating, a reflecting grating, a holographic grating and / or another type of dispersing element, wherein the measuring detector (Dm) is arranged such that it selectively receives the fraction (L2) of the Raman scattered light (LR) scattered by the disperser. [3] Measuring device (100, 200, 300) according to claim 1 to 2, wherein: the measuring detector (Dm) is a camera, a camera with an array of charge-coupled devices, a photodiode, a silicon photodiode, an avalanche photodiode, an avalanche silicon photodiode, or another type of detector configured to provide a measurement signal corresponding to a light intensity received by the detector; and / or The measuring detector (Dm) covers an active area of ​​1 - 2 mm. 2 a. [4] Measuring device (100, 200, 300) according to claims 1 to 3, wherein: the linear function (f(S) H2 )) of the measured intensity (S H2 ) is given by a sum of a product of a proportionality factor (A) and a difference between the measured intensity (S) H2 ) and a reference intensity (S ref ) and an offset (B); the proportionality factor (A), the reference intensity (S ref) and / or the offset (B) are each given by a constant that is determined during a calibration of the measuring device; and Calibration includes calibration measurements performed with the measuring device on reference samples with known hydrogen concentrations. [5] Measuring device (200, 300) according to claims 1 to 4, further comprising a reference detector (Dref) connected to the evaluation unit (7), wherein: the reference detector (Dref) is a photodiode, a silicon photodiode, an avalanche photodiode, an avalanche silicon photodiode or another type of detector configured to provide a measurement signal corresponding to a light intensity received by the detector; the reference detector (Dref) is configured to provide a reference intensity (S ref) to determine and provide by determining the intensity of a fraction (L3) of the Raman scattered light (LR) contained in the light (L1) emanating from the sample (3) and wavelengths within a limited reference wavelength range (Δλ) ref ) exhibits, where Raman intensity spectra (I(λ) s )) of the Raman scattered light (LR) emanating from the sample (3) a constant baseline intensity (I ref ) exhibit; the evaluation unit (7) is configured to determine the hydrogen concentration (C) based on the measured intensity (S) provided by the measuring detector (Dm). H2 ) and the reference intensity (S) provided by the reference detector (Dref). ref to determine; and the linear function (f(S) H2 )) of the measured intensity (S H2 ) a linear function of a difference between the measured intensity (S H2 ) and the reference intensity (S) determined by the reference detector (Dref).ref ) is. [6] Measuring device (200, 300) according to claim 5, wherein the reference detector (Dref) is arranged such that it selectively receives the portion (L3) of the Raman scattered light (LR) scattered by the disperser (13) which has wavelengths in the limited reference wavelength range (Δλ). ref ) exhibits. [7] Measuring device (200, 300) according to claims 1 to 6, further comprising a monitoring detector (D1) configured to measure a monitored intensity (I m ) to determine and provide an intensity (I1(t)) of the light (L1) emitted by the sample (3), wherein the monitoring detector (D1) is a photodiode, a silicon photodiode, an avalanche photodiode, an avalanche silicon photodiode or another type of detector configured to provide a measurement signal corresponding to a light intensity received by the detector. [8] Measuring device (200, 300) according to claim 7, wherein: a beam splitter (43) is arranged and configured between the sample (3) and the monochromator (5) to split the incident light (L1) emanating from the sample (3) into a main component that is transmitted to the monochromator (5) and a secondary component that is transmitted to the monitoring detector (D1); or the monochromator (5) includes a filter (11) arranged to receive the light (L1) emanating from the sample (3), the filter (11) being configured as a beam splitter which splits the incident light emanating from the sample (3) into a first component which is given by Raman scattering light and is transmitted through the filter (11) and a second component which is reflected from the filter (11) to the monitoring detector (D1). [9] Measuring device (200, 300) according to claims 7 to 8, wherein: the monitoring detector (D1) is connected to the evaluation unit (7); the evaluation unit (7) is configured to determine the hydrogen concentration (C) based on the measured intensity (S) provided by the measuring detector (Dm). H2 ) and the monitored intensity provided by the monitoring detector (D1) (I m ) to determine; the linear function (f(S) H2 )) is given by a sum of a product of a proportionality factor (A) and a difference between the measured intensity (S) H2 ) and a reference intensity (S ref ) and an offset (B) added to the product; the proportionality factor (A) is inversely proportional to the intensity (I1(t)) of the light (L1) emitted by the sample (3), which is the monitored intensity (I) provided by the monitoring detector (D1). m ) corresponds; and the reference intensity (S ref) is either given by a constant or is determined and provided by a reference detector (Dref) of the measuring device (200, 300) configured to provide the reference intensity (S ref ) to determine and provide by determining the intensity of a fraction (L3) of the Raman scattered light (LR) contained in the light (L1) emanating from the sample (3) and wavelengths in a limited reference wavelength range (Δλ ref ) exhibits, where Raman intensity spectra (I(λ) s )) of the Raman scattered light (LR) emanating from the sample (3) a constant baseline intensity (I ref exhibit. [10] Measuring device (200, 300) according to claims 1 to 9, further comprising an excitation detector (D0) configured to measure an excitation intensity (I ex) to determine and provide an excitation intensity (I0(t)) of the excitation light (L0) transmitted by the excitation light generator (1), wherein the excitation detector (D0) is a photodiode, a silicon photodiode, an avalanche photodiode, an avalanche silicon photodiode or another type of detector configured to provide a measurement signal corresponding to the light intensity received by the detector, and / or where: the excitation detector (D0) is contained in the excitation light generator (1); or a beam splitter (45) is arranged between the excitation light generator (1) and the sample (3), wherein the beam splitter (45) is configured to split incident excitation light (L0) into a main component which is transferred to the sample (3) and a secondary component which is transferred to the excitation detector (D0). [11] Measuring device (200) according to claims 1 to 10, further comprising a control unit (47) which is contained in or connected to the excitation light generator (1), wherein the control unit (47) is connected to an excitation detector (D0) which is configured to provide an excitation intensity (I ex ) to determine and provide an excitation intensity (I0(t)) of the excitation light (L0) transmitted by the excitation light generator (1), wherein the control unit (47) is further configured to determine the excitation intensity (I) transmitted by the excitation light generator (1). ex ) based on the excitation intensity provided by the excitation detector (D0) (I ex ) to regulate and / or control, and / or wherein the control unit (47) is connected to a monitoring detector (D1) which is configured to monitor an intensity (I m) to determine and provide which corresponds to an intensity (I1(t)) of the light (L1) emanating from the sample (3), and is configured to: Rules and / or controls of the excitation intensity (I ex ), which is transmitted by the excitation light generator (1), based on the monitored intensity (I m ), which is provided by the monitoring detector (D1); and / or Increasing the excitation intensity (I ex ), which is transmitted by the excitation light generator (1) when the monitored intensity (I m ) decreases and / or reduces the excitation intensity (I ex ), which is transmitted by the excitation light generator (1) when the monitored intensity (I m ) increases. [12] Measuring device (200) according to any one of claims 1 to 11, further comprising: a monitoring detector (D1) configured to monitor an intensity (I m) to determine and provide an intensity (I1(t)) of the light (L1) emanating from the sample (3); an excitation detector (D0) configured to detect an excitation intensity (I ex ) to determine and provide an excitation intensity (I0(t)) of the excitation light (L0) transmitted by the excitation light generator (1); and a monitoring unit (49) connected to the excitation detector (D0) and the monitoring detector (D1), wherein the monitoring unit (49) is configured to do at least one of the following: Determine, monitor and / or provide a sample efficiency (η) of the sample (3) based on a ratio of the monitored intensity (I) m ), which is provided by the monitoring detector (D1), and the excitation intensity (I ex ), which is provided by the excitation detector (D0); Issue a warning if the sample efficiency (η) deviates from an initial efficiency (η(t0)) determined at an initial time (t0) by more than a predefined threshold; and Issue an alarm if the sample efficiency (η) falls below a predefined minimum efficiency. [13] Measuring device (100, 200, 300) according to claims 1 to 12, wherein: the measurement wavelength (λ m ) is given by the wavelength at which the Raman intensity spectrum of pure hydrogen gas exposed to the excitation light (L0) provided by the excitation light generator (1) reaches its absolute maximum (M abs (H2)); and / or the measurement wavelength (λ m ) is given by a wavelength corresponding to a Raman wavenumber shift (Δk) of 592 cm -1 corresponds. [14] Measuring device (100, 200, 300) according to claims 1 to 12, wherein the measuring wavelength (λ m) is given by a wavelength at which the Raman intensity spectrum of pure hydrogen gas exposed to the excitation light (L0) provided by the excitation light generator (1) exhibits a relative maximum (M rel (H2)) or a relative maximum (M rel (H2)) exhibits, which is predetermined such that a wavelength range around the relative maximum (M rel (H2)), in which wavelength range contributions of several components that may be present in the sample (3) in addition to hydrogen are negligible or zero to the spectral intensities of a Raman intensity spectrum of the sample (3), is wider than a wavelength range around the absolute maximum (M abs (H2)) of the Raman intensity spectrum of pure hydrogen gas, in which the contributions of the several components are negligible or zero. [15] Measuring device (100, 200, 300) according to claims 1 to 12, wherein the measuring wavelength (λ m) is given by a wavelength corresponding to a Raman wavenumber shift (Δk) of 4152 cm -1 corresponds. [16] Measuring device (100, 200, 300) according to claim 15, wherein the range width of the measuring wavelength range (Δλ) m ) 3 nm to 5 nm. [17] Measuring device (300) according to claims 1 to 16, further comprising a Raman signal amplifier with an optical element (31) which focuses the excitation light (L0) onto a first focusing point (P1) in the sample (3), and a mirror arrangement with at least one focusing mirror (35, 37, 39, 41) which is arranged and configured such that it reflects and focuses incident light onto a focusing point (P1, P2) which is associated with the respective mirror (35, 37, 39, 41), such that the excitation light (L0) and the Raman scattered light (LR) resulting from interactions of the excitation light (L0) with the sample (3) are reflected back into the sample (3) at least once or several times before the light (L1) emanating from the sample (3) via one of the focusing points (P1) is transmitted to and received by the monochromator (5). [18] Measuring device (100, 200, 300) according to claims 1 to 17, wherein at least one of the following applies: the excitation light generator (1) includes a laser, a gas laser, a laser diode or another type of monochromatic light source; The excitation light (L0) is monochromatic light with an excitation wavelength in a range of 250 nm to 1000 nm or in a range of 350 nm to 450 nm; The excitation light generator (1) includes a pulsed laser and a lock-in amplifier (9) which is connected to a signal output of the measuring detector (Dm) and is configured to measure the intensity (S). H2 ) based on a measurement signal provided by the measuring detector (Dm) and a reference signal provided by the excitation light generator (1); and The sample (3) is contained in a measuring cell (19, 33) or a flow cell which includes at least one transparent window (25) that allows the excitation light (L0) to enter the measuring cell (19, 33) and the light (L1) emitted from the sample (3) to exit the measuring cell (19, 33). [19] Method (700) for measuring a hydrogen concentration (C) contained in a gas, wherein the method (700) comprises: Transfer of excitation light (L0) to a sample (3) of the gas, wherein the excitation light (L0) is configured to excite Raman scattering in the sample (3); Measuring a measured intensity (S H2 ) a fraction (L2) of the Raman scattered light emanating from the illuminated sample (3), wherein the fraction (L2) includes only wavelengths that fall within a measurement wavelength range (Δλ) m ) appear, where a range width of the measurement wavelength range (Δλ) m) smaller than or equal to several nanometers, smaller than or equal to 5 nm, or smaller than or equal to 3 nm, where the measurement wavelength range (Δλ) m ) a measurement wavelength (λ m ) includes a wavelength corresponding to a Raman wavenumber shift of 4152 cm -1 This corresponds to a wavelength that corresponds to a Raman wavenumber shift of 592 cm⁻¹. -1 corresponds to, or is given by a wavelength at which a Raman intensity spectrum of pure hydrogen gas exposed to the excitation light (L0) has a maximum; Determining the hydrogen concentration (C) as a linear function (f(S) H2 )) of the measured intensity (S H2 ); and Providing the hydrogen concentration (C).

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