▁mole cular ▁s ieve ▁bed , ▁which ▁removes ▁any ▁remaining ▁water ▁v ap our , ▁as ▁well ▁as ▁carbon ▁dio x ide , ▁which ▁would ▁free ze ▁and ▁plug ▁the ▁cry ogen ic ▁equipment . ▁M ole cular ▁sie ves ▁are ▁often ▁designed ▁to ▁remove ▁any ▁g ase ous ▁hydro car b ons ▁from ▁the ▁air , ▁since ▁these ▁can ▁be ▁a ▁problem ▁in ▁the ▁subsequent ▁air ▁dist ill ation ▁that ▁could ▁lead ▁to ▁explos ions . ▁The ▁mole cular ▁sie ves ▁bed ▁must ▁be ▁reg ener ated . ▁This ▁is ▁done ▁by ▁installing ▁multiple ▁units ▁operating ▁in ▁altern ating ▁mode ▁and ▁using ▁the ▁dry ▁co - produ ced ▁waste ▁gas ▁to ▁des orb ▁the ▁water . ▁ ▁Process ▁air ▁is ▁passed ▁through ▁an ▁integrated ▁heat ▁ex ch anger ▁( us ually ▁a ▁plate ▁fin ▁heat ▁ex ch anger ) ▁and ▁co o led ▁against ▁product ▁( and ▁waste ) ▁cry ogen ic ▁streams . ▁Part ▁of ▁the ▁air ▁li que f ies ▁to ▁form ▁a ▁liquid ▁that ▁is ▁en rich ed ▁in ▁o xygen . ▁The ▁remaining ▁gas ▁is ▁rich er ▁in ▁nit ro gen ▁and ▁is ▁dist illed ▁to ▁almost ▁pure ▁nit ro gen ▁( typ ically ▁< ▁ 1 pp m ) ▁in ▁a ▁high ▁pressure ▁( HP ) ▁dist ill ation ▁column . ▁The ▁cond enser ▁of ▁this ▁column ▁requires ▁re fr iger ation ▁which ▁is ▁obtained ▁from ▁expand ing ▁the ▁more ▁o xygen ▁rich ▁stream ▁further ▁across ▁a ▁val ve ▁or ▁through ▁an ▁Exp ander , ▁( a