Process and device for monitoring the hydrogen concentration

• US 20030192781A1
• Filed: 01/22/2003
• Published: 10/16/2003
• Est. Priority Date: 04/11/2002
• Status: Active Grant

• Current Assignee: Dragerwerk AG
• Original Assignee: Dragerwerk AG
• Inventors: Kiesele, Herbert, Tschuncky, Peter
• Granted Patent: US 7,175,753 B2
• Time in Patent Office: Days
• US Class Current: 204/424
• CPC Class Codes: G01N 27/4045 for gases other than oxygen
• CPC Class Codes: G01N 27/4163 checking the operation of, or calibrating, the measuring apparatus G01N27/3274, G01N27/4175 and G01N33/0006 take precedence
• CPC Class Codes: G01N 33/005 H2

Abstract

A process and a device are provided for monitoring the hydrogen concentration in a gas with at least one device, which comprises an electrochemical gas sensor and a bipotentiostat, e.g., for use in internal combustion engines with hydrogen, in fuel cells and in the petrochemical industry. The electrochemical gas sensor used has two working electrodes (3) and (4), with which the hydrogen and oxygen concentrations are determined in the gas in different steps due to the application of a voltage by a bipotentiostat (5-18). In an additional, optional step, a voltage in the range of −1,100 mV to −800 mV is applied to a working electrode (4), so that hydrogen is formed at the working electrode (4) and the functional surface of the working electrode (4) as well as the sensitivity of the working electrode (3) to hydrogen can be checked. A cyclic repetition of the process steps, preferably offset in time, with two devices makes possible the continuous monitoring of the hydrogen and oxygen concentrations with regular checking of the working electrodes (3, 4) for their readiness to function.

Claims

1. A process for monitoring the hydrogen concentration in a gas mixture with at least one first device comprising an electrochemical gas sensor, the process following steps forming a measuring cycle, wherein the process begins with any one of the steps comprising:

a) applying a voltage to a first working electrode in a first potential range, bringing about the oxidation of hydrogen, via a first operational amplifier, applying a voltage to a second working electrode in a second potential range, bringing about the reduction of oxygen, via a second operational amplifier, measuring a current conduction proportional to the concentration of hydrogen at the first working electrode, measuring a current conduction proportional to the concentration of oxygen at the second working electrode, sending the measured current values as a signal to a microcontroller and comparing the measured values with a preset signal value at the microcontroller;

b) applying to the two working electrodes a voltage in the second potential range, bringing about a reduction of oxygen, via the first and second operational amplifiers, measuring a current conduction proportional to the concentration of oxygen at the first and second working electrodes, sending the measured current values as a signal to the microcontroller and comparing the measured values with preset signal values at the microcontroller; and

c) interrupting a connection between the first operational amplifier and the first working electrode by opening a first switch to form an open circuit, determining an open circuit potential at the first working electrode, sending the open circuit potential value as a signal to the microcontroller via an instrument amplifier, comparing the open circuit signal with preset parameters at the microcontroller, applying a voltage in the second potential range to the second working electrode, bringing about the reduction of oxygen, via the second operational amplifier, measuring a current conduction proportional to the concentration of the oxygen at the second working electrode, sending a measured current conduction as a signal to the microcontroller and comparing the current conduction signal with a preset signal value at the microcontroller.

2. A process in accordance with claim 1, further comprising the steps:

d) applying a voltage in the first potential range to the first working electrode, bringing about the oxidation of hydrogen, via the first operational amplifier, applying a voltage in a third potential range to the second working electrode, bringing about the production of hydrogen, via the second operational amplifier, measuring a current conduction proportional to the concentration of the hydrogen at the first working electrode, measuring a current conduction proportional to the production of hydrogen at the second working electrode, sending the measured current conduction as a signal to the microcontroller and comparing the measured current conduction signals with a preset signal value at the microcontroller.

3. A process in accordance with claim 1, further comprising the step:

sending a warning signal by the microcontroller when a signal sent to the microcontroller in one of the steps a), b) and c) is outside a tolerance range around a preset signal set in advance for each of the steps.

4. A process in accordance with claim 2, further comprising the step:

e) sending a warning signal by the microcontroller when a signal sent to the microcontroller in one of the steps a), b), c) and d) is outside a tolerance range around a preset signal set in advance for each of the steps.

5. A process in accordance with claim 1, wherein a range between 0 mV and 200 mV is selected as the first potential range.

6. A process in accordance with claim 1, wherein a range between −

700 mV and −

300 mV is selected as the second potential range.

7. A process in accordance with claim 2, wherein a range between −

1,100 mV and −

800 mV is selected as the third potential range.

8. A process in accordance with claim 1, wherein a sequence formed from the steps a), b) and c) is continuously repeated.

9. A process in accordance with claim 8, wherein a sequence formed from the steps a), b) and c) is continuously repeated for a second device, which has the same design as the first device.

10. A process in accordance with claim 9, wherein the sequence formed from the steps is carried out offset in time for the first and second devices, so that said step a) is always being carried out in at least one of the two devices.

11. A device comprising:

a first working electrode with a first operational amplifier for applying a voltage to the first working electrode in a first potential range, bringing about the oxidation of hydrogen;

a second working electrode with a second operational amplifier for applying a voltage to the second working electrode in a second potential range, bringing about the reduction of oxygen;

a measuring device with a microcontroller, the measuring device for determining an open circuit potential and measuring a current conduction proportional to the concentration of hydrogen at the first working electrode and measuring a current conduction proportional to the concentration of oxygen at the second working electrode and sending the measured current values as a signal to the microcontroller and comparing the measured values with a preset signal value at the microcontroller, the first and second operational amplifiers applying to the two working electrodes a voltage in the second potential range, bringing about a reduction of oxygen and the measuring device measuring a current conduction proportional to the concentration of oxygen at the first and second working electrodes and sending the measured current values as a signal to the microcontroller and comparing the measured values with preset signal values at the microcontroller and a switch interrupting a connection between the first operational amplifier and the first working electrode to form the open circuit and the measuring device determining an open circuit potential at the first working electrode and sending the open circuit potential value as a signal to the microcontroller via an instrument amplifier and comparing the open circuit signal with a preset signal value at the microcontroller and the second operational amplifier applying a voltage in the second potential range to the second working electrode, bringing about the reduction of oxygen, and the measuring device measuring a current conduction proportional to the concentration of the oxygen at the second working electrode and sending a measured current conduction as a signal to the microcontroller and comparing the current conduction signal with a preset signal value at the microcontroller, the first working electrode being part of one of a first device unit or a second device unit and covering the first potential range with 0 mV to 200 mV and the second potential range with −

700 mV to −

300 mV; and

the second working electrode covering the second potential range with −

700 mV to −

300 mV as well as the third potential range with −

1,100 mV to −

800 mV.

12. A process for monitoring the hydrogen concentration in a gas mixture with at least one first device comprising an electrochemical gas sensor, the process comprising the steps of forming a measuring cycle, beginning with any one of the steps of:

applying a voltage to a first working electrode in a first potential range, bringing about the oxidation of hydrogen, via a first operational amplifier and applying a voltage to a second working electrode in a second potential range, bringing about the reduction of oxygen, via a second operational amplifier and measuring a current conduction proportional to the concentration of hydrogen at the first working electrode and measuring a current conduction proportional to the concentration of oxygen at the second working electrode and sending the measured current values as a signal to a microcontroller and comparing the measured values with a preset signal value at the microcontroller;

applying to the two working electrodes a voltage in the second potential range, bringing about a reduction of oxygen, via the first and second operational amplifiers, and measuring a current conduction proportional to the concentration of oxygen at the first and second working electrodes and sending the measured current values as a signal to the microcontroller and comparing the measured values with preset signal values at the microcontroller;

interrupting a connection between the first operational amplifier and the first working electrode by opening a first switch to form an open circuit, and determining an open circuit potential at the first working electrode and sending the open circuit potential value as a signal to the microcontroller via an instrument amplifier and comparing the open circuit signal with a preset signal value at the microcontroller and applying a voltage in the second potential range to the second working electrode, bringing about the reduction of oxygen, via the second operational amplifier, and measuring a current conduction proportional to the concentration of the oxygen at the second working electrode and sending a measured current conduction as a signal to the microcontroller and comparing the current conduction signal with a preset signal value at the microcontroller.

13. A process in accordance with claim 12, further comprising the steps:

applying a voltage in the first potential range to the first working electrode, bringing about the oxidation of hydrogen, via the first operational amplifier, and applying a voltage in a third potential range to the second working electrode, bringing about the production of hydrogen, via the second operational amplifier and measuring a current conduction proportional to the concentration of the hydrogen at the first working electrode and measuring a current conduction proportional to the production of hydrogen at the second working electrode and sending the each measured current conduction as a signal to the microcontroller and comparing the measured current conduction signals with a preset signal value at the microcontroller.

14. A process in accordance with claim 12, further comprising the step:

sending a warning signal by the microcontroller when a signal sent to the microcontroller in one of the steps is outside a tolerance range around a preset signal set in advance for each of the steps.

15. A process in accordance with claim 12, wherein a range between 0 mV and 200 mV is selected as the first potential range.

16. A process in accordance with claim 12, wherein a range between −

700 mV and −

300 mV is selected as the second potential range.

17. A process in accordance with claim 12, wherein a range between −

1,100 mV and −

800 mV is selected as the third potential range.

18. A process in accordance with claim 12, wherein a sequence formed from the steps is continuously repeated.

19. A process in accordance with claim 18, wherein a sequence formed from the steps is continuously repeated for a second device, which has the same design as the first device.

20. A process in accordance with claim 19, wherein the sequence formed from the steps is carried out offset in time for the first and second devices, so that said step of applying a voltage to a first working electrode in a first potential range, bringing about the oxidation of hydrogen, via a first operational amplifier and applying a voltage to a second working electrode in a second potential range, bringing about the reduction of oxygen, via a second operational amplifier and measuring a current conduction proportional to the concentration of hydrogen at the first working electrode and measuring a current conduction proportional to the concentration of oxygen at the second working electrode and sending the measured current values as a signal to a microcontroller and comparing the measured values with a preset signal value at the microcontroller is always being carried out in at least one of the two devices.