초록 ▼

An apparatus and a method for removing NOx from an exhaust stream of a lean-burn engine during an engine cold start are provided. The apparatus includes a close-coupled LNT coupled to a main LNT by a hollow conduit. NOx from the cold exhaust is initially stored on the close-coupled LNT. As the engin

An apparatus and a method for removing NOx from an exhaust stream of a lean-burn engine during an engine cold start are provided. The apparatus includes a close-coupled LNT coupled to a main LNT by a hollow conduit. NOx from the cold exhaust is initially stored on the close-coupled LNT. As the engine exhaust warms up, the close-coupled LNT reaches its operating temperature and reduces the stored NOx to N2. When the temperature of the close-coupled LNT reaches approximately 350° C., NOx is released from the close-coupled LNT, is absorbed on the main LNT, and is converted to N2 during fuel-rich conditions, The close-coupled LNT can be regenerated after the engine is turned off by providing heat. The released NOx during the regeneration of the closed-coupled LNT is absorbed by the main LNT. The stored NOx on the main LNT can be reduced to N2 during the next vehicle operation.

대표청구항 ▼

1. A method for the selective removal of NOx from a gaseous stream using lean NOx traps containing a catalyst that catalyzes the reduction of NOx to N2 and a compound that stores NOx as nitrates, comprising:heating a first lean trap to a temperature at which stored nitrates decompose and are release

1. A method for the selective removal of NOx from a gaseous stream using lean NOx traps containing a catalyst that catalyzes the reduction of NOx to N2 and a compound that stores NOx as nitrates, comprising:heating a first lean trap to a temperature at which stored nitrates decompose and are released; cooling the first lean NOx trap in an environment that does not contain NOx; passing the gaseous stream through the first lean NOx trap; and passing the gaseous stream through a second lean NOx trap, the second lean NOx trap storing NOx released from the first lean NOx trap. 2. The method of claim 1, comprising passing the gaseous stream through the first lean NOx trap at a temperature below 250° C.3. A method according to claim 1, comprising passing the gaseous stream through the first lean NOx trap at a temperature below 140° C.4. The method of claim 1, comprising passing the gaseous stream through the first lean NOx trap at a temperature below 200° C.5. The method of claim 4, wherein the temperature in the heating step is approximately 600° C.6. A method for reducing the total NOx released into the environment during operation from cold start to shut down of a vehicle containing an internal combustion engine comprising:operating the engine to produce an exhaust stream comprising NOx; passing the exhaust stream comprising NOx from the engine sequentially through a first LNT and a second LNT, wherein the LNTs comprise a catalyst that can cayalyze the reduction of NOx to N2 and compounds that can store NOx as nitrates; shutting off the engine; and after shutting off the engine, regenerating the first LNT by heating it to a temperature at which it releases stored NOx. 7. A method according to claim 6, comprising operating the internal combustion engine with alternating cycles of rich and lean fuel.8. A method according to claim 6, further comprising cooling the LNT in an environment that does not contain NOx.9. A method according to claim 6, wherein the engine is a diesel engine.10. A method according to claim 6, wherein the engine is a gasoline engine.11. A method according to claim 6, wherein regenerating the first LNT comprises heating it to 600° C.12. A method according to claim 11 wherein the heating step is carried out for about 30 seconds.