Device and methods of ammonia generation for NOx abatement
One embodiment of a method of operating a NOx abatement system comprises: introducing an exhaust stream to an ammonia generator in a normal flow direction, adsorbing NOx from the exhaust stream in the ammonia generator, diverting the exhaust stream around the ammonia generator, introducing hydrogen to the ammonia generator in a direction opposite the normal flow direction, and generating ammonia within the ammonia generator.
1. An ammonia generator, comprising:
a shell; and
a catalyst bed housed within said shell; wherein said catalyst bed comprises a substrate and a catalyst,
wherein said catalyst comprises a catalytic metal capable of reacting NOx and hydrogen to form ammonia, and a material capable of adsorbing NOx;
wherein said catalytic metal comprises about 100 g/ft 3 to about 260 g/ft 3 ruthenium, and about 10 g/ft 3 to about 50 g/ft 3 to platinum.
2. The generator of claim 1 , wherein said catalytic metal further comprises less than or equal to about 5 g/ft 3 rhodium and less than or equal to about 5 g/ft 3 palladium.
3. The generator of claim 1 , wherein said catalytic metal comprises no added rhodium and no added palladium.
4. The generator of claim 1 , wherein said ammonia generator is capable of converting about 20 vol % to about 75 vol % of NOx to ammonia, based upon a total volume of NOx in an exhaust stream.
5. The generator of claim 4 , wherein said ammonia generator is capable of converting about 30 vol % to about 65 vol % of NOx to ammonia, based upon a total volume of NOx in an exhaust stream.
6. The generator of claim 5 , wherein said ammonia generator is capable of converting about 40 vol % to about 55 vol % of NOx to ammonia, based upon a total volume of NOx in an exhaust stream.
7. The generator of claim 1 , wherein said material comprises neodymium.
8. A NOx abatement system, comprising:
an ammonia generator comprising an inlet end and an outlet end
an exhaust conduit connected in fluid communication to said inlet end;
a mixture conduit connected in fluid communication to said outlet end;
a by-pass circuit connected in fluid communication to said exhaust conduit on a first end and connected in fluid communication to said mixture conduit on a second end;
a reformer connected to said mixture conduit; and,
a valve capable of directing and inhibiting a flow of fluids, wherein said valve is disposed in said mixture conduit at a position capable of inhibiting flow of a fluid stream from said by-pass circuit into said ammonia generator and capable of directing reformate from said reformer into said ammonia generator.
9. The NOx abatement system of claim 8 , further comprising a selective catalytic reduction catalyst connected to said mixture conduit downstream from said by-pass conduit.
10. The NOx abatement system of claim 8 , wherein said ammonia generator comprises
a shell; and
a catalyst bed housed within said shell; wherein said catalyst bed comprises a substrate and a catalyst,
wherein said catalyst comprises a catalytic metal capable of reacting NOx and hydrogen to form ammonia, and a material capable of adsorbing NOx;
wherein said catalytic metal comprises about 100 g/ft 3 to about 260 g/ft 3 ruthenium, and about 10 g/ft 3 to about 50 g/ft 3 to platinum.
11. The NOx abatement system of claim 10 , wherein said catalytic metal further comprises less than or equal to about 5 g/ft 3 rhodium and less than or equal to about 5 g/ft 3 palladium.
12. The NOx abatement system of claim 11 , wherein said catalytic metal comprises no added rhodium and no added palladium.
13. A method of operating a NOx abatement system, comprising:
introducing an exhaust stream to an ammonia generator in a normal flow direction;
adsorbing NOx from said exhaust stream in said ammonia generator;
diverting said exhaust stream around said ammonia generator;
introducing hydrogen to said ammonia generator in a direction opposite said normal flow direction; and
generating ammonia within said ammonia generator.
14. The method of claim 13 , further comprising ceasing said diversion of said exhaust stream and introducing said ammonia to a selective catalytic reduction catalyst.
15. The method of claim 13 , further comprising converting about 20 vol % to about 75 vol % of said NOx to said ammonia, based upon a total volume of NOx in said exhaust stream.
16. The method of claim 15 , comprising converting about 30 vol % to about 65 vol % of said NOx.
17. The method of claim 16 , comprising converting about 40 vol % to about 55 vol % of said NOx.
18. The method of claim 13 , further comprising forming said hydrogen in a reformer.
19. The method of claim 13 , wherein said ammonia generator comprises
a shell; and
a catalyst bed housed within said shell; wherein said catalyst bed comprises a substrate and a catalyst,
wherein said catalyst comprises a catalytic metal capable of reacting NOx and hydrogen to form ammonia, and a material capable of adsorbing NOx;
wherein said catalytic metal comprises about 100 g/ft 3 to about 260 g/ft 3 ruthenium, and about 10 g/ft 3 to about 50 g/ft 3 to platinum.
20. The method of claim 19 , wherein said catalytic metal further comprises less than or equal to about 5 g/ft 3 rhodium and less than or equal to about 5 g/ft 3 palladium.