A concentric self-thermal reactor

in which ammonia decomposition is carried out in the center tube and hydrogen combustion takes place in the annulus was analyzed by modeling and simulation. The performance of the reactor with hydrogen-air flow co-current or counter-current to the ammonia flow was investigated and compared with that under isothermal condition. In the co-current mode

the high concentration of ammonia corresponds with the high heat generation rate of hydrogen combustion

while in the counter-current mode

the combustion heat is firstly used to increase the temperature of the hydrogen-air flow then used by ammonia decomposition. Therefore

the reactor with co-current flow is much more efficient in terms of the high conversion and the full use of hydrogen combustion heat. The co-current flow reactor performs as well as an isothermal reactor when a high conversion is realized.