The hydrogen gas plant based on ammonia cracking process consist of a ammonia cracker unit and PSA unit. In the ammonia cracker unit anhydrous ammonia is cracked at 8000c to 8500c to produce craced ammonia. The cracked ammonia contains 75% of hydrogen and 25% of nitrogen. In the PSA unit, cracked ammonia is passed through a desiccant in twin tower where the hydrogen gas is separated from the nitrogen gas.