PSA hydrogen production
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Personally, I think the first and second stages of PSA hydrogen production systems offer no other advantages aside from a higher hydrogen recovery rate; the investment required is quite high. I’d like to hear the opinions of experts on this
Since this is about hydrogen production, the hydrogen recovery rate is a key indicator. Although secondary pressure swing adsorption may seem like a costly investment in the short term, when considering the additional amount of hydrogen that can be recovered, such an investment is still worthwhile.
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Why is adding a secondary pressure swing adsorption unit necessary? To achieve better hydrogen purity?
It’s that the PSA system has been changed from a single stage to two stages, with the second-stage gas being used to flush and regenerate the first stage, thereby improving the hydrogen recovery rate! Investment should be 1.5-2 times the regular PSA
I see. So the recycled exhaust gas goes through pressure swing adsorption again, with two sets of pressure swing adsorption units, one in operation and one as a backup, is that right?
It’s also possible that at the first stage, not all impurities can be removed completely; then, through secondary treatment, the purity of hydrogen is increased, which makes it more suitable for applications with high requirements
The first stage removes most of the impurities, while the second stage removes them further； In the first stage, there are many pressure equalization cycles; the hydrogen content in the desorption vent gas is low. In the second stage, there is no venting at all; all gases are returned to the first stage for recovery ；
To achieve better regeneration, the two-stage adsorbent should have methods for venting, such as reverse venting, nitrogen flushing, or vacuum pumping
A single-stage PSA can ensure that the hydrogen purity remains above 99.95%. The secondary stage is meant to recover that 30% of hydrogen in the purge gas. If you calculate the investment period and the time required for recovery, you’ll see it’s not suitable. However, our unit was designed with a level 2 system, but it was never implemented. That’s the leader’s concern.