Nitrogen generator (PSA)

A PSA nitrogen generator makes nitrogen aboard ship by pressure-swing adsorption, passing compressed air through a carbon molecular sieve that adsorbs oxygen and lets nitrogen pass. Two adsorber vessels alternate between pressurized adsorption and depressurized regeneration, swinging on a cycle of seconds to deliver a continuous stream, usually at 95 to 99.5% purity. The nitrogen inerts cargo tanks on tankers, blankets the cargo on chemical and LNG carriers, and purges fuel-gas piping on gas-fueled ships. PSA suits moderate flow at modest purity; for higher purity or flow, membrane units or cryogenic plants are used instead.