Question about PSA

The higher the purity of the raw material, the lower the absorption rate, and the adsorbent cannot be utilized fully; hence, the utilization efficiency is low

A high product purity indicates that the height from the adsorption front to the outermost layer of the adsorbent must be high, higher than that for products with lower purity. The adsorbent in this section has hardly been used for adsorption at all; as a result, its utilization rate is low and the yield is also low

High purity means that less material is adsorbed, resulting in a low effective utilization rate of the molecular sieve; a large amount of product gas ends up going elsewhere during regeneration

To increase the purity of the product, it is necessary to minimize the adsorption time during this process, in order to avoid saturation and the introduction of impurities into the product. As a result, the adsorption time is reduced over a certain period; less gas is produced per unit volume of adsorbent, leading to a lower effective utilization rate of the adsorbent.

From the perspective of PSA operation, to increase the purity of the product gas, it is necessary to reduce the load or shorten the adsorption time; as a result, the utilization rate of the adsorbent cannot be maximized

With the same adsorbent, the product purity is adjustable. Taking hydrogen as an example, for the same processing volume, the higher the purity, the shorter the time required to release hydrogen (which in practice means reducing the adsorption time). It is essential to ensure proper pressure reduction and regeneration processes; otherwise, the time spent on the hydrogen release process (the adsorption process) becomes longer, resulting in lower recovery rates and efficiency. Under the same purity requirements, the larger the processing volume, the shorter the time available for hydrogen release in order to maintain the desired concentration. As a result, the overall time required for impurity adsorption is reduced, and the space velocity increases. The adsorbent needs to be regenerated sooner than it reaches adsorption equilibrium; this leads to a lower absorption efficiency and, consequently, a lower recovery rate. The longer the time for adsorbing impurities, the closer it is to adsorption equilibrium; consequently, more time is spent on releasing hydrogen. The higher the efficiency of the adsorbent, the less hydrogen is carried away by the desorbing gas during the regeneration process, and thus the higher the hydrogen recovery rate. You can pay attention to observing the operations and analyzing the data. Under the same concentration requirement, the smaller the gas flow rate, the lower the concentration of the target component retained in the purified gas, and the longer the acceptable adsorption time ； At the same adsorption time, the smaller the gas flow rate, the higher the hydrogen concentration, and the lower the concentration of the target retained component in the desorbed gas. At the same gas flow rate, the higher the concentration requirement, the shorter the acceptable adsorption time, and the higher the concentration of the target component retained in the desorbed gas. For PSA used in hydrogen production, the same concentration requirements generally apply; the smaller the gas flow rate, the longer the upper limit for the adjustable adsorption time ； The fewer hydrogen components in the analyzed gas, the better. The larger the gas volume, the shorter the adsorption time becomes; as a result, the overall cycle time is reduced, the frequency of desorption and regeneration increases, and the hydrogen concentration in the desorption gas rises.