Method and apparatus for detecting an increased hydrogen concentration in a liquid and / or a gas-liquid mixture

Abstract

The invention relates to a method for detecting an increased hydrogen concentration in a liquid (2), preferably in water, and / or in a gas-liquid mixture (3), which preferably contains water, comprising the steps: a) cleaving the hydrogen molecules contained in the liquid (2) and / or in the gas-liquid mixture (3) into two H+ protons each, b) measuring the pH in the region of the cleaved hydrogen molecules and c) comparing the measured pH with a pH of the liquid (2) and / or of the gas-liquid mixture (3) measured at an earlier point in time. The invention also relates to an apparatus (1) for implementing the method and to an electrochemical system comprising an apparatus (1) according to the invention.

Description

[0001] Description

[0002] Title:

[0003] Method and device for detecting an increased hydrogen concentration in a liquid and / or a gas-liquid mixture

[0004] The invention relates to a method and a device for detecting an elevated hydrogen concentration in a liquid, in particular in water, and / or a gas-liquid mixture. The gas-liquid mixture can, in particular, contain water as the liquid.

[0005] The preferred application of the invention is electrochemical systems, in particular electrolysis and / or fuel cell systems. The invention therefore further relates to an electrochemical system with a device according to the invention.

[0006] State of the art

[0007] With the help of an electrolysis system, hydrogen (H2) and oxygen (O2) can be obtained from water (H2O) by chemical splitting, whereby electrical current is required for the chemical splitting.

[0008] With the help of a fuel cell system, hydrogen and oxygen can be converted into electricity, heat and water in an electrochemical reaction.

[0009] Both systems, or electrochemical plants, therefore contain hydrogen, oxygen, and liquid water. Since the separation of the hydrogen and oxygen gases within the electrochemical cells of an electrolysis or fuel cell stack occurs solely through the cell membranes, diffusion processes can lead to mixing of the two gases. Depending on the hydrogen concentration, an explosive gas mixture can form. This must be prevented.

[0010] Therefore, the state of the art uses hydrogen sensors that can detect the hydrogen concentration in a gas mixture. However, the hydrogen sensors available on the market can only be used in gases. This means they are not suitable for detecting the hydrogen concentration in liquids, such as water, or in gas-liquid mixtures.

[0011] For electrolysis systems, especially PEM electrolysis systems, this means that – since no pure gas leaves the electrolysis stack – the hydrogen concentration in the oxygen can only be measured after a gas-liquid separator using a hydrogen sensor. However, an explosive gas mixture can form along the path to the gas-liquid separator, posing a safety risk.

[0012] A similar problem can occur during the operation of fuel cell systems, for example when liquid water is discharged from the anode side together with hydrogen-containing anode gas.

[0013] The present invention is concerned with increasing safety during the operation of an electrochemical plant. In particular, an elevated or dangerously high hydrogen concentration in a liquid and / or a gas-liquid mixture is to be detected early on in order to prevent the formation of an explosive gas mixture.

[0014] To achieve this objective, the method having the features of claim 1 and the device having the features of claim 7 are proposed. Advantageous developments of the invention can be found in the respective subclaims. Furthermore, an electrochemical system with a device according to the invention is specified.

[0015] Disclosure of the invention

[0016] The proposed method for detecting an increased

[0017] Determining the hydrogen concentration in a liquid, preferably in water, and / or in a gas-liquid mixture, which preferably contains water, comprises the steps of: a) splitting the hydrogen molecules contained in the liquid and / or in the gas-liquid mixture into two H+ protons each, b) measuring the pH value in the region of the split hydrogen molecules and c) comparing the measured pH value with a pH value of the liquid and / or the gas-liquid mixture which was measured at an earlier time.

[0018] The splitting of hydrogen molecules into two H+ protons each influences the pH of the liquid, so that by comparing the pH values ​​measured at different times, it is possible to determine whether the hydrogen concentration in the liquid has changed. Since the change in pH correlates with the number of H+ protons in the liquid, the pH can also be used to determine when the hydrogen concentration has become too high.

[0019] An increased hydrogen concentration or an increased number of H2 molecules does not change the pH of the liquid and / or the gas-liquid mixture. This means that the splitting of the H2 molecules into two H+ protons is a prerequisite for detecting a change in pH and thus an increased hydrogen concentration.

[0020] By comparing the pH value measured in step b) with a previous pH value measured without prior splitting of the hydrogen molecules present at that time, at least the presence of hydrogen molecules in the liquid and / or in the gas-liquid mixture can be detected.

[0021] By comparing the pH value measured in step b) with an earlier pH value measured after the hydrogen molecules present at that time had been split, an increase in the number of hydrogen molecules can be detected. Furthermore, the pH value can be used to determine the number of hydrogen molecules contained in the liquid and / or gas-liquid mixture. Liquid water, for example, has a pH of approximately 7, regardless of the number of H2 molecules dissolved in the water. If H2 molecules present in the water are split into two H+ protons each, the pH value changes. The more H+ protons present, the lower the pH value. The pH value of the water can therefore be used to determine not only the presence of hydrogen molecules, but also the hydrogen concentration in the water.

[0022] To carry out the process according to the invention, it is proposed that in step a) the hydrogen molecules are split by external excitation. External excitation can be achieved in various ways, for example, by ionizing the hydrogen molecules.

[0023] According to a preferred embodiment of the invention, in step a), the hydrogen molecules are split using light beams. The light beams can be used to excite the H2 molecules required for splitting. Light beams in the form of laser beams are preferably used. Using the laser beams, specific areas of the liquid or gas-liquid mixture can be irradiated in a targeted manner. The pH value is then measured in the irradiated area in the next step. The irradiated area is therefore also the measurement area.

[0024] Preferably, light or laser beams are used whose frequency essentially corresponds to the resonant frequency of the hydrogen molecules. The light or laser beams are then better absorbed by the hydrogen molecules, thus exciting them more strongly.

[0025] Furthermore, in step b) a pH sensor is preferably used to measure the pH value.

[0026] Furthermore, the pH value measured in step c) is preferably stored in a data storage device, which preferably also stores the pH value used as a reference value. The previously measured and stored pH value is therefore available as a reference value, allowing short-term changes to be recorded. This is advantageous from a safety perspective. The proposed method should therefore be carried out as regularly as possible and at relatively short intervals in order to be able to determine the hydrogen concentration in the liquid or gas-liquid mixture based on the measured pH value.

[0027] Furthermore, a device for detecting an elevated hydrogen concentration in a liquid, preferably in water, and / or in a gas-liquid mixture, which preferably contains water, is proposed. The device comprises: a closed volume for receiving the liquid and / or the gas-liquid mixture; a light source, preferably a laser, arranged outside the volume for generating light or laser beams; a pH sensor for measuring the pH value of the liquid and / or the gas-liquid mixture; and an evaluation device with a data memory in which a pH value of the liquid and / or the gas-liquid mixture is stored.

[0028] The proposed device comprises all the components necessary to carry out the previously described inventive method. The device thus enables the same advantages to be achieved. In particular, the device can be used to detect the presence of hydrogen molecules in a liquid or in a gas-liquid mixture, as well as an increase in the hydrogen concentration. The device thus forms a hydrogen sensor that—unlike known hydrogen sensors—can also be used in liquids or gas-liquid mixtures.

[0029] The closed volume of the device is preferably bounded by at least one wall that is at least partially permeable to light or laser beams. The light source or laser can thus be arranged outside the volume and thus outside the liquid or gas-liquid mixture.

[0030] According to a preferred embodiment of the invention, the closed volume is formed by a fluid line or a fluid reservoir. In this way, the device can be very easily integrated into an electrochemical system, in particular into an electrolysis and / or fuel cell system. Furthermore, the fluid line forming the closed volume or the fluid reservoir forming the closed volume is preferably connected to an outlet of a cell stack comprising a plurality of electrochemical cells. The outlet can in particular be a stack outlet of an electrolysis and / or fuel cell stack. A liquid or a gas-liquid mixture, which may contain hydrogen, is thus supplied to the fluid line or the fluid reservoir. With the aid of the device according to the invention, the hydrogen concentration in the liquid or in the gas-liquid mixture can then be monitored.In this way, a dangerously high hydrogen concentration can be detected early on, preventing the formation of an explosive gas mixture.

[0031] Since the preferred field of application of the invention is electrochemical systems, an electrochemical system, in particular an electrolysis system and / or a fuel cell system, is further proposed, comprising a device according to the invention. In the case of an electrolysis system, the device is preferably arranged between the outlet of an electrolysis stack and a gas-liquid separator. In the case of a fuel cell system, the device is preferably integrated into an anode subsystem, downstream of a drain valve for emptying a water tank of a water separator.

[0032] The invention and its advantages are described in more detail below with reference to the accompanying drawings. These show:

[0033] Fig. 1 is a schematic representation of a device according to the invention for detecting an increased hydrogen concentration in a gas-water mixture and

[0034] Fig. 2 is a schematic representation of the device of Figure 1 during the splitting of the hydrogen molecules contained in the gas-water mixture into two H+ protons each.

[0035] Detailed Description of the Drawings Figure 1 shows a device 1 according to the invention for detecting an elevated hydrogen concentration, which is integrated into an electrolysis system, specifically in the region of a fluid line 7 connected to an outlet 8 of an electrolysis stack (not shown). The fluid line 7 connects the outlet 8 to a gas-liquid separator 9, in which the gas phase of a gas-liquid mixture 3 is separated from a liquid 2, in this case water (H2O). The gases are hydrogen (H2) and oxygen (O2).

[0036] A pH sensor 6 is arranged on the fluid line 7, with the aid of which the pH value of the liquid 2 or the gas-liquid mixture 3 can be measured. Since the liquid in the fluid line 7 is water (H2O), the pH value is 7, regardless of the H2 concentration in the gas-liquid mixture 3. The H2 molecules have no influence on the pH value of the liquid 2 or the gas-liquid mixture 3. A conventional hydrogen sensor cannot be used to measure the hydrogen concentration in the gas-liquid mixture 3, as this only works in gases. This means that with a conventional hydrogen sensor, the hydrogen concentration can only be measured downstream of the gas-liquid separator 9.

[0037] With the aid of the device 1 according to the invention, in particular with the aid of the pH sensor 6 and a light source 5 in the form of a laser 10 (see Figure 2), the hydrogen concentration in the gas-liquid mixture 3 can be detected upstream of the gas-liquid separator 9. For this purpose, the laser 10 is activated and the laser beams are directed onto a region of the fluid line 7 in which the pH sensor 6 is arranged. For this purpose, the fluid line 7 is designed to be permeable to laser beams - at least in some regions. The laser beams are absorbed by the H2 molecules, causing them to split into two H+ protons each. These influence the pH value of the liquid 2 or the gas-liquid mixture 3, so that a change in the hydrogen concentration can be determined based on the change in the pH value. This is because an increased hydrogen concentration lowers the pH value in the region of the split or ionized H2 molecules.

Claims

Claims 1 . Method for detecting an increased hydrogen concentration in a liquid (2), preferably in water, and / or in a gas-liquid mixture (3), which preferably contains water, comprising the steps of: a) splitting the hydrogen molecules contained in the liquid (2) and / or in the gas-liquid mixture (3) into two H+ protons each, b) measuring the pH value in the region of the split hydrogen molecules and c) comparing the measured pH value with a pH value of the liquid (2) and / or the gas-liquid mixture (3) which was measured at an earlier time.

2. Process according to claim 1, characterized in that in step a) the hydrogen molecules are split by external excitation.

3. Process according to claim 1 or 2, characterized in that in step a) the hydrogen molecules are split by means of light beams, preferably by means of laser beams.

4. Method according to claim 3, characterized in that light beams are used whose frequency substantially corresponds to the resonance frequency of the hydrogen molecules.

5. Method according to one of the preceding claims, characterized in that a pH sensor (6) is used in step b).

6. Method according to one of the preceding claims, characterized in that the pH value measured in step c) is stored in a data memory, in which the pH value used as a comparison value is preferably also stored.

7. Device (1) for detecting an increased hydrogen concentration in a liquid (2), preferably in water, and / or in a gas-liquid mixture (3), which preferably contains water, comprising a closed volume (4) for receiving the liquid (2) and / or the gas-liquid mixture (3), a light source (5) arranged outside the volume (4), preferably a laser, for generating light or laser beams, a pH sensor (6) for measuring the pH value of the liquid (2) and / or the gas-liquid mixture (3), an evaluation device with a data memory in which a pH value of the liquid (2) and / or the gas-liquid mixture (3) is stored.

8. Device (1) according to claim 7, characterized in that the closed volume (4) is delimited by at least one wall which is at least partially permeable to light or laser beams.

9. Device (1) according to claim 7 or 8, characterized in that the closed volume (4) is formed by a fluid line (7) or a fluid reservoir, which is preferably connected to an outlet (8) of a cell stack comprising a plurality of electrochemical cells.

10. Electrochemical system, in particular electrolysis system and / or fuel cell system, with a device (1) according to one of claims 7 to 9.

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