METHOD FOR REGENERATING LEAN NOx TRAP OF EXHAUST PURIFICATION SYSTEM PROVIDED WITH LEAN NOx TRAP AND SELECTIVE CATALYTIC REDUCTION CATALYST AND EXHAUST PURIFICATION SYSTEM

• US 20170074191A1
• Filed: 11/30/2015
• Published: 03/16/2017
• Est. Priority Date: 09/15/2015
• Status: Active Grant

• Current Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Original Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Inventors: KANG, Jungwhun, KIM, Young Jic, JO, Won Jin
• Granted Patent: US 9,702,310 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 2260/04 for regeneration or reactivation, e.g. of catalyst
• CPC Class Codes: F01N 2430/06 by varying fuel-air ratio, e.g. by enriching fuel-air mixture
• CPC Class Codes: F01N 2560/025 for measuring or detecting O2, e.g. lambda sensors
• CPC Class Codes: F01N 2560/026 for measuring or detecting NOx
• CPC Class Codes: F01N 2560/06 the means being a temperature sensor
• CPC Class Codes: F01N 2560/08 the means being a pressure sensor
• CPC Class Codes: F01N 2570/14 Nitrogen oxides
• CPC Class Codes: F01N 2570/18 Ammonia
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 2610/1453 Sprayers or atomisers; Arrangement thereof in the exhaust apparatus
• CPC Class Codes: F01N 2900/08 said parameters being related to the engine
• CPC Class Codes: F01N 2900/1404 Exhaust gas temperature
• CPC Class Codes: F01N 2900/1406 Exhaust gas pressure
• CPC Class Codes: F01N 2900/1614 NOx amount trapped in catalyst
• CPC Class Codes: F01N 2900/1622 Catalyst reducing agent absorption capacity or consumption amount
• CPC Class Codes: F01N 3/021 by means of filters
• CPC Class Codes: F01N 3/0807 by using absorbents or adsorbents
• CPC Class Codes: F01N 3/0814 combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F01N 3/0885 : Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps
• CPC Class Codes: F01N 3/206 : Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents F01N3/2066 takes precedence
• CPC Class Codes: F01N 3/2066 : Selective catalytic reduction [SCR]
• CPC Class Codes: F02D 2200/08 : Exhaust gas treatment apparatus parameters
• CPC Class Codes: F02D 2200/0806 : NOx storage amount, i.e. amount of NOx stored on NOx trap
• CPC Class Codes: F02D 41/0235 : in relation with the state of the exhaust gas treating apparatus control of exhaust gas treating apparatus per se F01N
• CPC Class Codes: F02D 41/0275 : the exhaust gas treating apparatus being a NOx trap or adsorbent
• CPC Class Codes: F02D 41/1446 : the characteristics being exhaust temperatures
• CPC Class Codes: Y02A 50/20 : Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies

Abstract

A method for regenerating a lean NOx trap (LNT) of an exhaust purification system having the LNT and a selective catalytic reduction (SCR) catalyst includes determining whether a regeneration release condition of the LNT is satisfied; determining whether a regeneration demand condition of the LNT is satisfied; and performing regeneration of the LNT if the regeneration release condition of the LNT and the regeneration demand condition of the LNT are satisfied, wherein satisfaction of the regeneration release condition of the LNT is determined based on an NOx amount absorbed in the LNT, an NH3 amount stored in the SCR catalyst and temperature at an upstream of the SCR catalyst.

Claims

1. A method for regenerating a lean NOx trap (LNT) of an exhaust purification system having the LNT and a selective catalytic reduction (SCR) catalyst, comprising:

determining whether a regeneration release condition of the LNT is satisfied;

determining whether a regeneration demand condition of the LNT is satisfied; and

performing regeneration of the LNT when the regeneration release condition of the LNT and the regeneration demand condition of the LNT are satisfied,

wherein satisfaction of the regeneration release condition of the LNT is determined based on an NOx amount absorbed in the LNT, an NH3 amount stored in the SCR catalyst, and temperature at an upstream of the SCR catalyst.

2. The method of claim 1, wherein the regeneration release condition of the LNT is satisfied when the NOx amount absorbed in the LNT is greater than or equal to a threshold NOx amount, and a final factor calculated based on a base factor, a first correction factor according to the NH3 amount stored in the SCR catalyst, and a second correction factor according to the temperature at the upstream of the SCR catalyst is greater than or equal to a predetermined value.

3. The method of claim 2, wherein the first correction factor decreases or is maintained as the NH3 amount stored in the SCR catalyst increases.

4. The method of claim 2, wherein the second correction factor increases or is maintained as the temperature at the upstream of the SCR catalyst is lowered.

5. The method of claim 1, wherein the regeneration release condition of the LNT is satisfied when a final factor calculated based on a base factor according to the NOx amount absorbed in the LNT, a first correction factor according to the NH3 amount stored in the SCR catalyst, and a second correction factor according to the temperature at the upstream of the SCR catalyst is greater than or equal to a predetermined value.

6. The method of claim 5, wherein the first correction factor decreases or is maintained as the NH3 amount stored in the SCR catalyst increases.

7. The method of claim 5, wherein the second correction factor increases or is maintained as the temperature at the upstream of the SCR catalyst is lowered.

8. The method of claim 1, further comprising:

determining whether a regeneration stop condition of the LNT is satisfied during performing the regeneration of the LNT; and

stopping the regeneration of the LNT and switching to a normal operation mode when the regeneration stop condition of the LNT is satisfied.

9. An exhaust purification system comprising:

an engine including an injector which injects fuel thereinto, generating power by burning a mixture of air and the fuel, and exhausting the exhaust gas generated at combustion process to outside through an exhaust pipe;

a lean NOx trap (LNT), which is mounted on the exhaust pipe, absorbing nitrogen oxide (NOx) contained in the exhaust gas at a lean air/fuel ratio, releasing the absorbed nitrogen oxide at a rich air/fuel ratio, and to reduce the nitrogen oxide contained in the exhaust gas or the released nitrogen oxide using a reductant including carbon or hydrogen contained in the exhaust gas;

a dosing module mounted at an exhaust pipe downstream of the LNT and directly injecting a reducing agent into the exhaust gas;

a selective catalytic reduction (SCR) catalyst mounted at the exhaust pipe downstream of the dosing module and reducing the NOx contained in the exhaust gas by using the reducing agent injected by the dosing module; and

a controller configured to perform denitrification (DeNOx) by using the LNT and/or the SCR catalyst according to a driving condition of the engine,

wherein the controller performs regeneration of the LNT when both of a regeneration demand condition of the LNT and a regeneration release condition of the LNT are satisfied, and

wherein the controller determines whether the regeneration release condition of the LNT is satisfied based on an NOx amount absorbed in the LNT, an NH3 amount stored in the SCR catalyst, and a temperature at an upstream of the SCR catalyst.

10. The exhaust purification system of claim 9, wherein the regeneration release condition of the LNT is satisfied when the NOx amount absorbed in the LNT is greater than or equal to a threshold NOx amount, and a final factor calculated based on a base factor, a first correction factor according to the NH3 amount stored in the SCR catalyst, and a second correction factor according to the temperature at the upstream of the SCR catalyst is greater than or equal to a predetermined value.

11. The exhaust purification system of claim 10, wherein the first correction factor decreases or is maintained as the NH3 amount stored in the SCR catalyst increases.

12. The exhaust purification system of claim 10, wherein the second correction factor increases or is maintained as the temperature at the upstream of the SCR catalyst is lowered.

13. The exhaust purification system of claim 9, wherein the regeneration release condition of the LNT is satisfied when a final factor calculated based on a base factor according to the NOx amount absorbed in the LNT, a first correction factor according to the NH3 amount stored in the SCR catalyst, and a second correction factor according to the temperature at the upstream of the SCR catalyst is greater than or equal to a predetermined value.

14. The exhaust purification system of claim 13, wherein the first correction factor decreases or is maintained as the NH3 amount stored in the SCR catalyst increases.

15. The exhaust purification system of claim 13, wherein the second correction factor increases or is maintained as the temperature at the upstream of the SCR catalyst is lowered.

16. The exhaust purification system of claim 9, wherein the controller, during performing the regeneration of the LNT, stops the regeneration of the LNT and switches into a normal operation mode when the regeneration stop condition of the LNT is satisfied.