Pressure swing adsorption apparatus for high purity hydrogen purification from ammonia decomposition and hydrogen purification method using the same
The present disclosure relates to a pressure swing adsorption apparatus for high purity hydrogen purification from ammonia decomposition and a hydrogen purification method using the same, and more specifically, the pressure swing adsorption apparatus includes a plurality of adsorption towers including a guard bed unit and a hydrogen purification unit, in which each adsorption tower is packed with different adsorbents, to purify high purity hydrogen from mixed hydrogen gas produced after ammonia decomposition, make it easy to replace the adsorbent for ammonia removal, minimize the likelihood that the lifetime of the adsorbent in the hydrogen purification unit is drastically reduced by trace amounts of ammonia, efficiently recover hydrogen of the guard bed unit, thereby maximizing the hydrogen recovery rate compared to a conventional pressure swing adsorption process including a pretreatment unit and a hydrogen purification unit, and respond to a large change in ammonia concentration in the raw material.
1 . A hydrogen purification method using a pressure swing adsorption apparatus, comprising:
providing the pressure swing adsorption apparatus comprising:
a raw material feed pipe for supplying a mixed hydrogen gas produced after ammonia decomposition;
a plurality of adsorption towers including a guard bed unit disposed at a lower position and a hydrogen purification unit disposed at an upper position;
a vacuum pump connected to the plurality of adsorption towers to maintain the plurality of adsorption towers under vacuum pressure; and
a plurality of valves configured to open and close pipes connecting the plurality of adsorption towers and the vacuum pump,
wherein each adsorption tower of the guard bed unit is packed with a first adsorbent and a second adsorbent arranged in layers to selectively remove moisture and ammonia, respectively, from the mixed hydrogen gas,
wherein each adsorption tower of the hydrogen purification unit is packed with a third adsorbent to selectively remove nitrogen from the mixed hydrogen gas, and
wherein during operation a lowest pressure reached in each adsorption tower of the guard bed unit is not less than one fourth of a raw material feed pressure;
feeding the mixed hydrogen gas produced after ammonia decomposition into an adsorption tower of the guard bed unit through the raw material feed pipe;
selectively adsorbing and removing moisture by allowing the fed mixed hydrogen gas to pass through the first adsorbent packed at a lower layer region of the adsorption tower in the guard bed unit;
selectively adsorbing and removing ammonia by allowing the mixed hydrogen gas free of moisture to pass through the second adsorbent packed at an upper layer region of the adsorption tower in the guard bed unit;
feeding the mixed hydrogen gas free of moisture and ammonia into an adsorption tower of the hydrogen purification unit; and
selectively adsorbing and removing nitrogen by allowing the fed mixed hydrogen gas free of moisture and ammonia to pass through the third adsorbent packed in the adsorption tower in the hydrogen purification unit to acquire purified hydrogen.
2 . The hydrogen purification method of claim 1 , wherein the step of selectively adsorbing and removing ammonia reduces an amount of ammonia in the mixed hydrogen gas free of moisture to less than 0.1 ppm, and
wherein the step of selectively adsorbing and removing nitrogen reduces an amount of nitrogen in the purified hydrogen to less than 10 ppm.
3 . The hydrogen purification method of claim 1 , wherein the guard bed unit comprises first through fifth adsorption towers, and the hydrogen purification unit comprises first through fifth adsorption towers,
wherein the method further comprises:
operating each of the first through fifth adsorption towers of the guard bed unit to perform an adsorption step, a first pressure equalization step, a second pressure equalization step, a purge providing step, a countercurrent blowdown step, a vacuum purge step, a first pressurization step, a second pressurization step, and a final pressurization step by product in sequence; and
operating each of the first through fifth adsorption towers of the hydrogen purification unit to perform an adsorption step, a first pressure equalization step, a second pressure equalization step, a purge providing step, a countercurrent blowdown step, a vacuum purge step, a first pressurization step, a second pressurization step, and a final pressurization step by product in sequence.
4 . The hydrogen purification method of claim 3 , further comprising:
regenerating the first adsorbent and the second adsorbent of an adsorption tower of the guard bed unit by supplying a tail gas emitted from an adsorption tower of the hydrogen purification unit as a purge gas to the adsorption tower of the guard bed unit after the countercurrent blowdown step.
5 . The hydrogen purification method of claim 1 , wherein the guard bed unit comprises first through sixth adsorption towers, and the hydrogen purification unit comprises first through sixth adsorption towers,
wherein the method further comprises:
operating each of the first through sixth adsorption towers of the guard bed unit to perform an adsorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge providing step, a countercurrent blowdown step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a final pressurization step by product in sequence; and
operating each of the first through sixth adsorption towers of the hydrogen purification unit to perform an adsorption step, a first pressure equalization step, a second pressure equalization step, a third pressure equalization step, a purge providing step, a countercurrent blowdown step, a vacuum purge step, a first pressurization step, a second pressurization step, a third pressurization step, and a final pressurization step by product in sequence.