석유화학공장에서 나오는 배가스인 수소, 이산화탄소, 일산화탄소, 메탄의 원료혼합가스로부터 수소를 회수할 수 있는 다탑 PSA 공정을 orthogonal collocation법에 의해 전산모사하였다. 고순도 수소를 생산하기 위하여 흡착성능이 다른 두 흡착제를 연속으로 충전시킨 4탑 9단계 공정을 대상으로 하였다. 제올라이트와 활성탄의 충전비율은 제품의 순도 및 회수율에 영향을 미치며 각 흡착제에 대한 최적의 충전길이는 각각 60cm이었다. 주어진 충전비율에 대해서 최적의 흡착 압력과 원료기체 공급 속도가 각각 19 atm 및 11.0cm/s로 결정될 수 있었다. 고압에서 저압으로 떨어지면서 세정기체를 공급하는 향류 감압단계에서 압력변화의 크기(DP) 즉, 세정 단계로 공급되는 세정기체의 양이 제품의 회수율과 순도에 크게 영향을 미쳤다. DP가 1.3 atm이상에서는 DP가 증가함에 따라 순도가 크게 변하지 않았지만 회수율은 계속 감소하였다. DP가 커질수록 압력균등화 병류감압단계에서의 압력이 낮아지고 세정단계 다음에 이어지는 압력균등화 향류가압단계에서의 균등 압력도 낮아졌으며, 이에 따라 생성물 가압단계에서 압력을 높이는데 필요한 기체 생성물의 양이 증가하였다.

Numerical simulation for hydrogen-recovery multibed PSA process was performed by orthogonal collocation method for the feed mixture gas of hydrogen, carbon dioxide, carbon monoxide, and methane in petrochemical plant. A fourbed and nine-step process using a layered-bed which was consecutively packed with two different adsorbents in one bed was employed to produce high-purity hydrogen. The packing raito of zeolite to activated carbon affected the purity and recovery of the product. The optimum length of zeolite layer and that of activated carbon layer were 60cm each. The optimum adsorption pressure and feed velocity could be determined to be 19 atm and 11.0 cm/s, respectively, for given packing ratio. The recovery and purity of the product were strongly affected by Difference-Pressure(DP) which was defined as the difference between the initial high pressure and the final low pressure at the cocurrent blowdown step which delivers purge gas to the low pressure bed. When the DP was larger than 1.3 atm, the purity did not change much and the recovery was continuously decreased with increasing DP. As DP increased, the pressure at the pressure-equalization cocurrent depressurization step was lowered and the pressure at the pressure-equalization countercurrent pressurization step following purge step was also lowered. Therefore, the amount of the high-pressure product to pressurize the low-pressure column increased.

PSA Hydrogen Purification Separation Adsorption

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