Method and apparatus for estimating dosing error in a selective catalytic reduction system

Abstract

A method for determining dosed reductant by considering expected (37) and measured (38) exhaust output states from an SCR device (20), NOx sensor sensitivity data and performing a cross-correlation operation. A method of whether a Selective Catalytic Reduction (SCR) device (20) is mis-dosed, said NOx sensor sensitivity data being an indication of how sensitive the measured exhaust output state is to mis-dosing errors.

Description

technical field [0001] The present disclosure relates to a method and apparatus for estimating dosing errors in a selective catalytic reduction system. Background technique [0002] Selective catalytic reduction (SCR) systems can be used to convert nitrogen oxides (NOx), such as may be produced by internal combustion engines, into less harmful emissions such as nitrogen and water. An SCR system may include a catalyst / catalyst to facilitate a reaction between NOx that may be present in a gas stream passing through the SCR system, and a reductant to substantially remove the NOx from the gas stream. [0003] The reductant may be added to the gas stream and adsorbed onto the catalyst before it reacts with NOx in the gas stream passing through the SCR system. Where the reducing agent used is ammonia, it can be added to the gas stream as eg anhydrous ammonia, aqueous ammonia or urea which is thermally decomposed to ammonia in the SCR system before being adsorbed onto the catalyst...

AI Technical Summary

Problems solved by technology

[0014] However, ammonia sensors are not as reliable as NOx sensors, in addition to not taking into account any of the other factors related to dosing errors, such as sensor drift and changes in the level of ammonia that can be stored on the catalyst due to changes in catalyst temperature, and thus such systems are very unstable

Additionally, additional sensors increase system complexity and cost

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