Control of selective catalytic reduction
AssigneeRicardo UK Limited
InventorsHector Sindano, Ben Rogers, Andy Noble, Matthew Keenan, Phil Mortimer
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Abstract
A method of controlling a rate of introduction of a NOx reducing substance or precursor to a catalyst component. The method comprises obtaining the amount of NOx entering the catalyst component, modeling the amount of NOx reducing substance or precursor in the catalyst component and controlling the rate of introduction of the NOx reducing substance or precursor to reduce NOx.
Claims18
An apparatus comprising a controller configured to control the rate of an introduction component for providing a NOx reducing precursor to a catalyst component, the controller:
- obtaining an amount of NOx entering the catalyst component from a NOx sensor,
- modeling an amount of NOx reducing substance or precursor in the catalytic component to react with the NOx obtained by the NOx sensor, and
- controlling the rate of the introduction component to produce NOx reducing substance or precursor to reduce NOx,
- wherein an optimum NOx reducing precursor introduction rate, Mu_inj_rate_opt, satisfies the relation:
- Mu_inj_rate_opt=(ku·Mnox_rate−Mu_stored/Tau_rel)/X
- wherein ku is the amount of NOx reducing substance required to reduce one mole of NOx;
- Mu_stored is the mass of NOx reducing precursor stored in the catalyst;
- Tau_rel is a time constant for the rate of NOx reducing precursor release from the catalyst;
- and
- Mnox_rate is the mass flow rate of NOx emission entering the catalyst component, and X is the fraction of introduced NOx reducing precursor that immediately decomposes into NH3.
A method of controlling a rate of introduction of a NOx reducing precursor to a catalyst component, comprising:
- obtaining the amount of NOx entering the catalyst component without monitoring the amount of NOx leaving the catalyst component, modeling the amount of NOx reducing substance or precursor in the catalyst component and controlling the rate of introduction of the NOx reducing precursor to reduce NOx,
- wherein the step of modeling the amount of NOx reducing substance or precursor further comprises:
- modeling the amount of introduced NOx reducing precursor converted into NOx reducing substance dependent on a catalyst component temperature;
- modeling the amount of NOx reducing precursor stored in the catalyst component dependent on the catalyst component temperature;
- and
- modeling the amount of stored NOx reducing precursor released dependent on the catalyst component temperature;
- wherein an optimum NOx reducing precursor introduction rate, Mu_inj_rate_opt, satisfies the relation:
- Mu_inj_rate_opt=(ku·Mnox_rate−Mu_stored/Tau_rel)/X
- wherein ku is the amount of NOx reducing substance required to reduce one mole of NOx;
- Mu_stored is the mass of NOx reducing precursor stored in the catalyst;
- Tau_rel is a time constant for the rate of NOx reducing precursor release from the catalyst;
- and
- Mnox_rate is the mass flow rate of NOx emission entering the catalyst component and X is the fraction of introduced NOx reducing precursor that immediately decomposes into NH3.
Dependencies are inferred from the claim text.