Exhaust gas detection and treatment, and related systems

Abstract

A method for calculating the relative ratios of NH3 and NOx in exhaust gases to detect NH3 slip using NOx sensors includes measuring a first NOx level at an upstream NOx sensor, administering a first predetermined dose of urea to the exhaust gases, measuring a second NOx level at a downstream NOx sensor, administering a second predetermined dose of urea to the exhaust gases, measuring a third NOx level at the downstream NOx sensor, calculating a difference between the second NOx level and the third NOx level, and comparing the difference between the second NOx level and the third NOx level to a lookup table to determine a ratio of a concentration of NH3 to a concentration of NOx in the exhaust gases. Related systems and methods are also disclosed.

1 . A method of determining a ratio of NO x  to NH 3  in exhaust gases, the method comprising:
 providing an exhaust system for an agricultural vehicle, the exhaust system comprising:
 an upstream NO x  sensor; 
 a downstream NO x  sensor; 
 a catalytic converter comprising a first catalyst; 
 a urea injector; and 
 an exhaust control unit; 
 measuring a first NO x  level of the exhaust gases at the upstream NO x  sensor; 
 administering a first predetermined dose of urea to the exhaust gases; 
   measuring a second NO x  level of the exhaust gases at the downstream NO x  sensor;   administering a second predetermined dose of urea to the exhaust gases;   measuring a third NO x  level of the exhaust gases at the downstream NO x  sensor;   calculating a difference between the second NO x  level and the third NO x  level; and   comparing the difference between the second NO x  level and the third NO x  level to a lookup table to determine a ratio of a concentration of NH 3  to a concentration of NO x  leaving the exhaust gases.   
     
     
         2 . The method of  claim 1 , wherein the second predetermined dose of urea is larger than the first predetermined dose of urea. 
     
     
         3 . The method of  claim 1 , wherein the exhaust system further comprises a second catalyst. 
     
     
         4 . The method of  claim 1 , wherein the first catalyst is a selective catalytic reduction catalyst. 
     
     
         5 . The method of  claim 3 , wherein the first catalyst is an ammonia oxidation catalyst. 
     
     
         6 . The method of  claim 1 , wherein the exhaust system further comprises a temperature sensor. 
     
     
         7 . The method of  claim 1 , wherein the exhaust system further comprises a diesel particulate filter. 
     
     
         8 . An agricultural vehicle comprising an exhaust system configured to carry out the method of  claim 1 . 
     
     
         9 . A method of treating an exhaust gas, the method comprising:
 measuring a first NO x  concentration in an exhaust gas flow;   administering a first dose of NH 3  to the exhaust gas flow during a first time period and passing the exhaust gas flow through a catalytic converter;   measuring a second NO x  concentration in the exhaust gas downstream of the catalytic converter responsive to the first dose;   administering a second dose of NH 3  to the exhaust gas flow during a second time period and passing the exhaust gas flow through the catalytic converter;   measuring a third NO x  concentration in the exhaust gas downstream of the catalytic converter responsive to the second dose;   calculating a difference between the second NO x  concentration and the third NO x  concentration; and   comparing the difference between the second NO x  concentration and the third NO x  concentration to calibration data to determine a ratio of a concentration of NH 3  to a concentration of NO x  in the exhaust gas flow leaving the catalytic converter.   
     
     
         10 . The method of  claim 9 , wherein the second dose of NH 3  is larger than the first dose of NH 3 . 
     
     
         11 . The method of  claim 9 , further comprising filtering particulate material from the exhaust gas flow. 
     
     
         12 . The method of  claim 9 , wherein administering the first dose of NH 3  and administering the second dose of NH 3  each comprise injecting urea into the exhaust gas flow and hydrolyzing urea to form NH 3  and CO 2 . 
     
     
         13 . The method of  claim 9 , further comprising reacting the NH 3  with NO x  in the catalytic converter to form N 2  and H 2 O. 
     
     
         14 . The method of  claim 9 , further comprising determining the ratio of the concentration of NH 3  to the concentration of NO x  in the exhaust gas flow without measuring the concentration of NH 3 . 
     
     
         15 . An exhaust gas treatment system, comprising:
 an upstream NO x  sensor;   a urea injector;   a catalytic converter comprising a first catalyst downstream of the upstream NO x  sensor and the urea injector;   a downstream NO x  sensor downstream of the catalytic converter; and   an exhaust control unit, wherein the exhaust control unit is configured to:
 measure a first NO x  concentration in an exhaust gas flow at the upstream NO x  sensor; 
 administer a first dose of urea to the exhaust gas flow at the urea injector; 
 measure a second NO x  concentration in the exhaust gas at the downstream NO x  sensor; 
 administer a second dose of urea to the exhaust gas flow at the urea injector; 
 measure a third NO x  concentration in the exhaust gas at the downstream NO x  sensor; 
 calculate a difference between the second NO x  concentration and the third NO x  concentration; and 
 compare the difference between the second NO x  concentration and the third NO x  concentration to calibration data to determine a ratio of a concentration of NH 3  to a concentration of NO x  in the exhaust gas flow entering the exhaust system. 
   
     
     
         16 . The system of  claim 15 , wherein the catalytic converter further comprises a second catalyst having a composition different from the first catalyst. 
     
     
         17 . The system of  claim 15 , wherein the first catalyst is a selective catalytic reduction catalyst. 
     
     
         18 . The system of  claim 17 , wherein the first catalyst is an ammonia oxidation catalyst. 
     
     
         19 . The system of  claim 15 , further comprising a temperature sensor configured to communicate with the exhaust control unit. 
     
     
         20 . The system of  claim 15 , further comprising a diesel particulate filter.