Gaseous Hydrogen/Oxygen Drying Subsystem The hydrogen and oxygen streams leaving the electrolysis unit contain water vapor that must be removed before the gases are liquefied so as to prevent ice formation. A drying subsystem (Fig. 5) is used to remove the water vapor. Wet gas leaving the electrolyzer at operating temperature enters a heat exchanger and rejects some of its heat to the drying radiator. The cooled gas stream then enters a cold trap where 99.9% of the water content of the stream is removed through condensation. A sorption dryer, consisting of a rotor built up of corrugated sheets impregnated with a hygroscopic salt, removes the remaining water from the stream. Drying takes place in approximately three-quarters of the rotor with regeneration of the sorption material taking place in the remaining quarter section. Regeneration is accomplished by reheating a portion of the gas stream exiting the cold trap and passing it through the rotor. All water removed in the drying process is sent back to the electrolysis unit [4], The drying subsystem equipment mass for the 250 kWe system was taken directly from Ref. [4], The 20 kWe drying subsystem mass was scaled linearly based on the total mass flow of wet gas into the driers.
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