Method and system for anhydrous ammonia recovery
View Patent ↗An apparatus for recycling exhaust gas includes a vessel containing a reversible ammonia sorber material which is exothermic when sorbing (“loading”) ammonia and which is endothermic when releasing (“unloading”) ammonia. A first valve selectively couples a source of exhaust gas including ammonia to a first port of the vessel, a second valve selectively couples a vacuum pump to the vessel, and a third valve selectively coupling a second port of the vessel to an output. A controller opens and closes the first valve, the second valve and the third valve to implement a loading phase, an intermediate venting phase and an unloading phase for the vessel.
1. A method for recovering ammonia from exhaust gas comprising:
loading a vessel, during a loading phase of not less than 1 minute and not more than forty minutes, with an input gas containing ammonia via a vessel inlet proximate to a first portion of the vessel, wherein the vessel contains a reversible ammonia adsorber material;
venting the vessel via a venting outlet, under a vacuum condition, during an intermediate venting phase after the loading phase, wherein the intermediate venting phase has a duration defined by at least one of a time threshold, a vapor pressure threshold and an N 2 content threshold; and
unloading the vessel via an unloading outlet, under a vacuum condition, during an unloading phase after the intermediate venting phase, whereby ammonia is recovered from exhaust gas.
2. The method as recited in claim 1 wherein the venting outlet and the unloading outlet are the same.
3. The method as recited in claim 1 wherein the vessel inlet and the unloading outlet are the same.
4. The method as recited in claim 1 wherein the unloading outlet is different from the vessel inlet and is positioned in the first portion of the vessel.
5. The method as recited in claim 1 wherein, at the end of the intermediate venting phase, less than 1% of the vented gas is N 2 .
6. The method as recited in claim 1 wherein the vessel is provided with at least one temperature sensor.
7. The method as recited in claim 6 wherein the at least one temperature sensor includes a thermocouple positioned within a second portion of the vessel.
8. The method as recited in claim 6 wherein the initiation of the venting phase is based upon at least one of sensing of a threshold temperature within the vessel and of a timed duration limit of the loading operation.
9. The method as recited in claim 8 wherein the threshold temperature is in the range of about 1 to 75° C. above a reference temperature.
10. The method as recited in claim 9 wherein the threshold temperature is in the range of about 5 to 40° C. above the reference temperature.
11. The method as recited in claim 10 wherein the threshold temperature is in the range of about 10 to 30° C. above the reference temperature.
12. The method as recited in claim 8 wherein the timed duration limit of the loading operation has a factory-set predetermined maximum.
13. The method as recited in claim 8 where the timed duration limit of the loading operation has a field-adjustable predetermined maximum.