Operating Pressure Control
Heatless regenerative air dehumidifying equipment feature a short switching cycle between the two towers. Since there is not enough time for depressurizing and pressurizing (i.e. aligning the pressure inside the regeneration tower with the drying tower), dry purge air is delivered to the off-line tower while it is pressurizing, triggering fluctuations in operating pressure.
This pressure pulsation adversely affects both downstream equipment and upstream compressor controls. A heated regenerative air dehumidifying equipment effectively eliminates pressure fluctuations due to the switch-over process.
If a heated regenerative air dehumidifying equipment cannot be used in your operating environment, optimal cubic capacity of the air tank and pipes can be identified to minimize pressure pulsation.
The amount of air needed to increase the pressure of the on-line tower from 0 MPa to 0.69 MPa based on the total regeneration flow rate and the flow rate at the pressurization valve can be obtained using the following equation.
Where the internal cubic capacity of a vessel is V (1,012 m3), the total amount of air (VFP) is
Let's assume we are loading the compressor in a system with a rated compressor flow rate that's designed to align with the dehumidifying equipment’s regeneration flow rate and the flow rate of the on-line tower. If the controlled pressure difference, or ΔP, (occurring before the backup compressor command is activated), is 0.05 MpaG, the required capacity of piping and air tank (VALL) is
Considering that the air tank pressure can be increased from the load pressure to unload pressure while the compressor is running, the compressor's rated flow rate (QC) is greater than the load flow rate (QL). Therefore, the piping and air tank capacity actually required should be smaller than the VALL shown above.
・Absolute atmospheric pressure (MPa): 0.101325
・Internal cubic capacity of a vessel: V
・Total amount of air: VFP
・Controlled pressure difference: ΔP
・Required capacity of piping and air tank: VALL
