US 7,442,555 B2 · Ammonia gas sensor method and device

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.

Claims43

Dependent claims

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;
absorbing SO2 from at least one of said 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 equilibrium concentration ratio between NO and NO2;
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.

6 more elements

Dependencies are inferred from the claim text.

Ammonia gas sensor method and device

Life of this patent

Ammonia gas sensor method and device

Life of this patent

Abstract

Claims43