Method for detecting or monitoring sulfur dioxide with an electrochemical sensor
First Claim
1. A method of detecting or monitoring sulfur dioxide in an emission gas comprisingcontacting the emission gas with an electrochemical micro-sensor device comprising a substrate supporting an arrangement of a working electrode, a reference electrode, and a counter electrode, wherein a first portion of the electrodes is covered with an insulator, and a second portion of the electrodes is covered with an electrolyte, and wherein the electrodes and the insulator are applied to the substrate using a thick film technique;
- maintaining the micro-sensor device at a constant temperature higher than the temperature of the emission gas contacting the micro-sensor device;
measuring the current output of the micro-sensor device;
determining if the current output indicates the presence of sulfur dioxide; and
generating a signal.
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Abstract
A thick film electrochemical micro-sensor device for detecting or monitoring sulfur dioxide, comprising a substrate to which is applied a working electrode, a counter electrode, a reference electrode, and optionally a heater and a temperature detector, wherein a portion of the electrodes is covered with an insulator, and a portion of the electrodes is covered with an electrolyte. The device is especially useful for detecting or monitoring sulfur dioxide in emission gases. A method of detecting or monitoring sulfur dioxide emissions using the electrochemical micro-sensor device includes contacting the emission gas with the sensor of the present invention, measuring the current output of the sensor, determining if the current output indicates the presence of sulfur dioxide, and generating a signal, that can be used to actuate a scrubber system when a pre-determined level of sulfur dioxide is detected.
36 Citations
18 Claims
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1. A method of detecting or monitoring sulfur dioxide in an emission gas comprising
contacting the emission gas with an electrochemical micro-sensor device comprising a substrate supporting an arrangement of a working electrode, a reference electrode, and a counter electrode, wherein a first portion of the electrodes is covered with an insulator, and a second portion of the electrodes is covered with an electrolyte, and wherein the electrodes and the insulator are applied to the substrate using a thick film technique; -
maintaining the micro-sensor device at a constant temperature higher than the temperature of the emission gas contacting the micro-sensor device;
measuring the current output of the micro-sensor device;
determining if the current output indicates the presence of sulfur dioxide; and
generating a signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
generating a first signal based on the current output of the micro-sensor device;
providing at least a second sensor substantially identical to the micro-sensor device, wherein the second sensor is adapted to detect interference from other chemical species besides sulfur dioxide;
contacting the emission gas with the second sensor;
measuring the current output of the second sensor;
generating a second signal based on the current output of the second sensor; and
subtracting the second signal from the first signal.
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5. The method of claim 1, wherein the substrate is an insulating material selected from the group consisting of plastic, glass, ceramic, quartz, and mixtures thereof.
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6. The method of claim 1, wherein the working electrode and counter electrode are each independently selected from the group consisting of gold, platinum, palladium, silver, silver-silver chloride, carbon, and mixtures thereof.
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7. The method of claim 1, wherein the reference electrode comprises one of silver-silver chloride and mercury-mercuric chloride.
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8. The method of claim 1, wherein said first portion of the electrodes is a connect portion and said second portion of the electrodes is a sensing portion, and wherein the connect portion connects the electrode to an electrical circuit, and is protected from the environment by the insulator, and wherein the sensing portion is exposed to the environment via the electrolyte.
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9. The method of claim 1, wherein the electrolyte comprises an ion conductive resin or membrane.
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10. The method of claim 1, further comprising a temperature detector, optionally wherein the temperature detector comprises platinum.
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11. The method of claim 1, wherein the micro-sensor device further comprises a heater, optionally wherein the heater comprises a substantially serpentine pattern of conductive material printed onto the opposite side of the substrate from the three electrodes.
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12. The method of claim 1, wherein the working and counter electrodes are disposed adjacent to each other, with a gap therebetween of less than or equal to about 0.2 inches over at least 90 percent of their length.
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13. The method of claim 1, wherein the arrangement of three electrodes is a substantially elliptical arrangement wherein the working and counter electrodes are substantially concentrically oriented with respect to each other without the reference electrode interposed between them.
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14. The method of claim 1, wherein the arrangement of three electrodes is a substantially circular arrangement wherein the working and counter electrodes are substantially concentrically oriented with respect to each other without the reference electrode interposed between them.
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15. The method of claim 1, wherein the arrangement of three electrodes is a rectangular arrangement wherein the working and counter electrodes are substantially concentrically oriented with respect to each other without the reference electrode interposed between them.
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16. The method of claim 1, wherein the arrangement of the three electrodes includes an adjacent working electrode and counter electrode, wherein portions of the working electrode are interdigitated with portions of the counter electrode, and wherein the reference electrode is disposed outwardly from the working and counter electrodes.
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17. The method of claim 1, wherein the insulator is an insulating material selected from the group consisting of glass, and a glass-containing dielectric material.
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18. The method of claim 1, wherein the thick film technique comprises the steps of:
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providing at least one template containing a pattern for the arrangement of the three electrodes;
contacting the substrate with the template;
applying at least one electrode precursor ink, and insulator precursor ink onto the template/substrate to form a sensor configuration according to the template pattern;
drying the sensor configuration;
firing the sensor configuration; and
covering a portion of the three electrodes with an electrolyte.
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Specification