TSA Drying (TSA)

In plain terms

After the deoxo, hydrogen is still saturated with water vapour. A dryer passes it through towers packed with an adsorbent, such as a molecular sieve or alumina, which holds the water on its surface.

Once a bed is loaded, it must be regenerated while a second bed takes over. The two common methods differ in how they release the water:

• Temperature swing adsorption (TSA): heats the loaded bed to release the water, at roughly constant pressure, then cools it for the next cycle.
• Pressure swing adsorption (PSA): drops the bed pressure and purges it with dry product gas. It needs no heater, but the purge gas is product that is lost.

TSA and PSA are both used for electrolytic hydrogen. Kwon et al. (2023) describe a TSA dryer with heater-driven regeneration downstream of a PEM electrolyzer. Ligen et al. (2020) dried hydrogen from an alkaline electrolyzer with vacuum-assisted PSA at 98.4 % recovery, a 1.6 % drying loss.

Typical range

Regeneration heat, purge losses and outlet dew point depend on the adsorbent, cycle design and the target purity grade. One published data point: the vacuum-assisted PSA tested by Ligen et al. (2020) lost 1.6 % of the hydrogen in drying.

Why it moves LCOH

The dryer's main cost effect is the hydrogen it uses for purge and regeneration, which never reaches the customer. Every kilogram lost this way adds directly to cost per delivered kilogram. TSA also adds a heat load, which can come from waste heat in an integrated plant.

Common mistake