Selective NOx catalytic reduction system including an ammonia sensor
First Claim
1. A system for control of nitrogen oxide concentrations in a stream of exhaust gas from an internal combustion engine, comprising:
- a) a first catalytic element disposed in said stream of exhaust gas for catalytically reducing nitrogen oxides to elemental nitrogen;
b) a second catalytic element disposed in said stream of exhaust gas downstream of said first catalytic element for further catalytic treatment of said exhaust gas;
c) a system for injecting an ammoniacal chemical reductant into said stream of exhaust gas ahead of said first and second catalytic elements; and
d) an ammonia sensor disposed in said stream of exhaust gas between said first and second catalytic elements for sensing ammonia concentrations in said stream of exhaust gas.
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Abstract
An improved SCR system for controlling NOx levels in internal combustion engine exhaust, comprising a least one ammonia sensor disposed at an intermediate longitudinal location in an SCR catalyst and in communication with a System Control Module (SCM). The ammonia measurement permits calculation of ammonia storage on catalyst sites via a stored SCM algorithm. Locating the ammonia sensor midway in the catalyst allows for optimum control of NOx reduction and permits the portion of the catalyst downstream of the sensor to be treated as a slip catalyst, thus minimizing or eliminating the need for a second slip catalyst and housing, and reducing the size, volume, complexity, and cost of an SCR system. In-brick ammonia sensor permits the system to manage engine exhaust to a desired NOx conversion level and ammonia slip target value, thus minimizing the rate of consumption of ammonia while meeting required limits for NOx emissions.
37 Citations
14 Claims
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1. A system for control of nitrogen oxide concentrations in a stream of exhaust gas from an internal combustion engine, comprising:
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a) a first catalytic element disposed in said stream of exhaust gas for catalytically reducing nitrogen oxides to elemental nitrogen; b) a second catalytic element disposed in said stream of exhaust gas downstream of said first catalytic element for further catalytic treatment of said exhaust gas; c) a system for injecting an ammoniacal chemical reductant into said stream of exhaust gas ahead of said first and second catalytic elements; and d) an ammonia sensor disposed in said stream of exhaust gas between said first and second catalytic elements for sensing ammonia concentrations in said stream of exhaust gas. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An internal combustion engine, comprising a system for control of nitrogen oxide concentrations in a stream of exhaust gas from said engine, wherein said system includes
a first catalytic element disposed in said stream of exhaust gas for catalytically reducing nitrogen oxides to elemental nitrogen, a second catalytic element disposed in said stream of exhaust gas downstream of said first catalytic element for further catalytic treatment of said exhaust, a system for injecting an ammoniacal chemical reductant into said stream of exhaust gas ahead of said first and second catalytic elements, and an ammonia sensor disposed in said stream of exhaust gas between said first and second catalytic elements for sensing ammonia concentrations in said stream of exhaust gas.
Specification