Method and device for safe storage and use of volatile ammonia storage materials
There is described a method and apparatus ( 100, 100′ ) for storing and delivering ammonia wherein at least two ammonia storage materials ( 1 a, 2 a ) capable of reversibly adsorbing or absorbing ammonia having different ammonia vapor pressures are used. Ammonia storage material ( 2 a ) having a lower vapor pressure, which is only partially saturated with ammonia or void of ammonia, is brought into fluid communication with ammonia storage material ( 1 a ) having a higher ammonia vapor pressure to adsorb or absorb ammonia released from the ammonia storage material ( 1 a ) having a higher ammonia vapor pressure when the latter is higher than a pressure threshold. An automotive NO x treatment system ( 200 ) comprising such apparatus ( 100, 100′ ) is also described.
1. A system for storing and delivering ammonia, comprising:
first and second storing/delivery units connectable in fluid communication, said first and second storing/delivery units comprising heating means and
containing first and second solid ammonia storage materials capable of reversibly ad- or absorbing and desorbing ammonia,
wherein the first ammonia storage material in the first storing/delivery unit has a higher vapour pressure than the second ammonia storage material in the second storing/delivery unit.
2. The system according to claim 1 , wherein the first storing/delivery unit has a first shell with a surface area A 1 and a heat-transfer coefficient α 1 and the second storing/delivery unit has a second shell with a surface area A 2 and a second heat-transfer coefficient α 2 , and wherein the following relation applies: α 2 A 2 >α 1 A 1 .
3. The system according to claim 1 , further comprising a buffer container being connectable in fluid communication to at least one of the first and second storing/delivery units.
4. The system according to claim 1 , further comprising an absorbing unit being connectable in fluid communication to at least one of the first and second storing/delivery units wherein the absorbing unit either contains a reversibly ad- or absorbing and desorbing ammonia storage material or an irreversibly ad- or absorbing ammonia storage material.
5. The system according to claim 1 , comprising a control valve arrangement for connecting at least the first storing/delivery unit with an ammonia consumer.
6. The system according to claim 5 wherein the ammonia consumer is selected from a catalyst for SCR of NO x in oxygen-containing exhaust gas, a catalytic device for splitting ammonia into nitrogen and oxygen and a fuel cell.
7. The system according claim 6 wherein SCR of NO x in the oxygen-containing exhaust gas is effected in an automobile, truck, train, ship or other motorized machine, vehicle or engine-driven generator.
8. Automotive NO x treatment device comprising a system according to claim 1 .