Anode-cathode chamber pressure difference and cell voltage
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This post was last edited by sunjl1981 on 2013-1-6 at 23:40. The pressure difference between the cathode chamber and the anode chamber at the top of the unit cell is 0.4 meters of water column. This positive pressure difference effectively reduces the slot voltage, whereas a negative pressure difference increases it by 0.4–0.5V per unit. How does the pressure difference between the anode and cathode chambers affect the cell voltage? Can someone talk about it in detail? # ， ， &
1. High cell pressure reduces the bubble effect, resulting in a smaller electrolyte pressure drop； But it can’t be too high either, otherwise the groove won’t be able to handle it ； 2. The positive pressure difference reduces the cell voltage compared to the negative pressure difference: the conductivity of the cathode solution is more than twice that of the anode solution.
Could you explain it in more detail? Thank you! Everyone, please speak up more!
Ugh, I’m not sure if it’s the ion-exchange membrane alkali production process; if so, the negative pressure difference affects more than just the cell voltage.
The explanation on the 2nd floor was quite clear: it is mainly because the conductivity of the catholyte differs from that of the anolyte, and as a result of the reverse pressure difference, the distance between the two liquids and the membrane changes.
It’s mainly related to the resistance of the electrolyte. Since the conductivity of the anode solution is much lower than that of the cathode solution, a positive pressure difference is maintained; however, if this difference is too large, the anode will deform and the voltage will increase as the distance between the electrodes increases. The negative pressure difference causes the membrane to lean toward the cathode, increasing the resistance of the anode solution and raising the voltage.
An appropriate pressure difference ensures that the ion exchange membrane can adhere effectively to the surface of the anode, preventing it from vibrating during operation and avoiding friction with the anode and cathode. When the pressure difference is insufficient, friction between the ion exchange membrane and the anode and cathode occurs in the upper part of the electrolyzer and near the anode liquid outlet, resulting in pinholes. When the pressure difference is negative, the voltage increases because the specific resistivity of the anode liquid is greater than that of the cathode liquid, leading to a rise in voltage. An excessive negative pressure difference can cause the cathode to deform and result in pinholes in the ion exchange membrane, while an excessive positive pressure difference can cause the anode to deform, leading to pinholes or salt bubbles in the ion exchange membrane. Therefore, maintaining an appropriate pressure difference is crucial for the proper operation of ion exchange membrane electrolysis.
During normal operation, maintaining stability in the pressure difference across the electrolyzer is crucial to preventing mechanical damage to the ion exchange membrane. Damage to the membrane mainly manifests as pinholes, with most of these pinholes appearing at the seams between the anode grids. In fact, it is inevitable for there to be fluctuations in pressure difference while the electrolyzer is in operation; what can be done is to try to keep these fluctuations within a narrow range. Even with such fluctuations present, the seams between the anode grids represent the weakest points. These pressure fluctuations cause the ion exchange membrane to vibrate continuously within the gaps between the anode grid seams, leading to friction between the curled edges of those seams and the membrane, which results in the formation of pinholes. Moreover, large positive pressure differences can cause the welds at these seams to separate, thereby damaging the membrane.