AMMONIA GAS SENSOR METHOD AND DEVICE
First Claim
1. A method of detecting the concentration of ammonia in a gas comprising the steps of:
- receiving a source stream of gas;
splitting the source stream of gas into first and second streams of gas;
exposing one of said first and second streams of gas to a first catalyst system under conditions capable of converting NH3 present in the gas to N2;
exposing the remaining one of said first and second streams of gas to a second catalyst system under conditions capable of converting NH3 present in the gas to NO;
exposing each of said first and second streams of gas through a third catalyst system to establish a steady state concentration ratio between NO and NO2, whereby the NO2 percentage of the total NOx gas present is in the range of about 0.5% to about 10%;
detecting the levels of NOx present in said first and second streams of gas; and
calculating the difference in NOx concentrations between said first and second streams of gas.
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Accused Products
Abstract
A mixed potential sensor device and methods for measuring total ammonia (NH3) concentration in a gas is provided. The gas is first partitioned into two streams directed into two sensing chambers. Each gas stream is conditioned by a specific catalyst system. In one chamber, in some instances at a temperature of at least about 600° C., the gas is treated such that almost all of the ammonia is converted to NOx, and a steady state equilibrium concentration of NO to NO2 is established. In the second chamber, the gas is treated with a catalyst at a lower temperature, preferably less than 450° C. such that most of the ammonia is converted to nitrogen (N2) and steam (H2O). Each gas is passed over a sensing electrode in a mixed potential sensor system that is sensitive to NOx. The difference in the readings of the two gas sensors can provide a measurement of total NH3 concentration in the exhaust gas. The catalyst system also functions to oxidize any unburned hydrocarbons such as CH4, CO, etc., in the gas, and to remove partial contaminants such as SO2.
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Citations
47 Claims
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1. A method of detecting the concentration of ammonia in a gas comprising the steps of:
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receiving a source stream of gas; splitting the source stream of gas into first and second streams of gas; exposing one of said first and second streams of gas to a first catalyst system under conditions capable of converting NH3 present in the gas to N2; exposing the remaining one of said first and second streams of gas to a second catalyst system under conditions capable of converting NH3 present in the gas to NO; exposing each of said first and second streams of gas through a third catalyst system to establish a steady state concentration ratio between NO and NO2, whereby the NO2 percentage of the total NOx gas present is in the range of about 0.5% to about 10%; detecting the levels of NOx present in said first and second streams of gas; and calculating the difference in NOx concentrations between said first and second streams of gas. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A sensor for measuring total ammonia (NH3) concentration in a source stream of gas, comprising:
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first and second flow paths for dividing the source stream of gas into first and second streams of gas; a first catalyst system exposed to the first flow path for converting NH3 present in the first stream of gas to N2; a second catalyst system exposed to the second flow path for converting NH3 present in the second stream of gas to NO; a third catalyst system exposed to the first and second flow path to establish a steady state concentration ratio between NO and NO2, whereby the NO2 percentage of the total NOx gas present is in the range of about 0.5% to about 10%; and a sensor element for detecting the levels of NOx present in the first and second streams of gas. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of detecting the concentration of ammonia in a gas comprising the steps of:
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receiving a source stream of gas; splitting the source stream of gas into first and second streams of gas; exposing one of said first and second streams of gas to a first catalyst system under conditions capable of converting NH3 present in the gas to N2; exposing the remaining one of said first and second streams of gas to a second catalyst system under conditions capable of converting NH3 present in the gas to NO; exposing said first and second streams of gas through a third catalyst comprising a catalyst selected from the group consisting of;
RuO2, CuO, Ag, and Pt;establishing a steady state concentration ratio between NO and NO2, whereby the NO2 percentage of the total NOx gas present is in the range of about 0.5% to about 10%; detecting the levels of NOx present in said first and second streams of gas; and calculating the difference in NOx concentrations between said first and second streams of gas. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
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30. A method of detecting the concentration of ammonia in a gas comprising the steps of:
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receiving a source stream of gas; splitting the source stream of gas into first and second streams of gas; exposing one of said first and second streams of gas to a first catalyst system under conditions capable of converting NH3 present in the gas to N2; exposing the remaining one of said first and second streams of gas to a second catalyst system under conditions capable of converting NH3 present in the gas to NO; establishing a steady state concentration ratio between NO and NO2, whereby the NO2 percentage of the total NOx gas present is in the range of about 0.5% to about 10%; detecting the levels of NOx present in said first and second streams of gas; and calculating the difference in NOx concentrations between said first and second streams of gas. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A sensor for measuring total ammonia (NH3) concentration in a source stream of gas, comprising:
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first and second flow paths for dividing the source stream of gas into first and second streams of gas; a first catalyst system exposed to the first flow path for converting NH3 present in the first stream of gas to N2; a second catalyst system exposed to the second flow path for converting NH3 present in the second stream of gas to NO; a sensor element for detecting the levels of NOx present in the first and second streams of gas; and an equilibrating stage including RuO2, CuO, Ag, or mixtures thereof for establishing a steady state concentration ratio between NO and NO2. - View Dependent Claims (41, 42, 43, 44, 45, 46, 47)
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Specification