Regarding the PSA sequence
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Our unit has 10 adsorption towers; the configuration has been changed from 10-2-4 to 10-2-3. This voltage equalization process is missing one step; what are its advantages and disadvantages?
In pressure equalization, the number of towers has been reduced from 4 to 3; as a result, the pressure difference for pressure equalization increases. A longer pressure equalization time is beneficial for regeneration, but it prolongs the adsorption time, which affects the purity of the product gas
The number of voltage equalization cycles affects the hydrogen yield. Theoretically, the more equalization times there are, the higher the hydrogen yield.
I can’t figure out why a higher number of voltage equalization cycles results in a higher hydrogen yield
Pressure swing adsorption involves adsorption at high pressure and desorption at low pressure; the more times this pressure equalization is carried out, the lower the pressure becomes, and the more impurities are removed in the desorption process
I’m a beginner; could you explain why the lower the number of voltage equalization cycles, the lower the voltage?
The pressure at the end of the 4D process is surely lower than that at the end of the 3D process; the subsequent steps of forward flushing, reverse flushing, and rinsing are used to release the pressure that remains after the 4D or 3D process is completed. The higher the end pressure at which voltage equalization occurs, the more Analysis gas is released, and the less product gas remains. The pressure equalization process involves reducing the pressure inside the recovery tower; the more times this is done, the higher the hydrogen recovery rate will naturally be
Since you seem to be struggling with this issue, let’s take an example: Suppose the adsorption pressure is 2.2 MPa and the pressure at the end of flushing is 0.03 MPa. The pressure difference for four cycles of pressure equalization is = (2.2 – 0.03)/5 = 0.434 MPa. After the first cycle, the pressure is 1.766 MPa; after the second cycle, it’s 1.332 MPa; after the third cycle, it’s 0.898 MPa; after the fourth cycle, it’s 0.464 MPa, followed by flushing at 0.03 MPa. The pressure difference for three cycles of pressure equalization is = (2.2 – 0.03)/4 = 0.5425 MPa. After the first cycle, the pressure is 1.6575 MPa; after the second cycle, it’s 1.115 MPa; after the third cycle, it’s 0.5725 MPa, followed by flushing at 0.03 MPa. It can be seen that the pressures at the end of the four-cycle and three-cycle processes are different. Since the pressure is lower after four cycles of equalization, more hydrogen is recovered, resulting in a higher recovery rate! I’m not sure if you understand with this explanation
The lower the pressure, the cleaner the rinsing – is that correct?