Precautions after the new ion exchange membrane is put into use
Thread Content
After replacing the membrane in the entire electrolyzer, a certain pattern was observed: after operating at currents ranging from 10,000A to 125,000A for 1 month, the current gradually increased to 150,000A; whereas after 10 days of operation, it also reached 150,000A. The voltage and the amount of acid added to the electrolyzer differed significantly in these cases. The calculated difference in direct current consumption was around 80 kWh. Let’s analyze together what requirements there are regarding the use of the new membrane.
Which manufacturer’s membrane is it, and what does the manufacturer’s technical specification state? What is the maximum electrical density required? What is the electrical density during actual operation? What is the quality of the brine? Specifically, what is the level of calcium and magnesium ions in it? What about other situations?
Based on operational experience, when putting the new electrochemical membrane into service for power generation, it is necessary to ensure that the cell temperature remains above 70 degrees. During operation, the current should not exceed 11 KA for 24 hours or more; after operating at 12.5 KA steadily for more than half a month, the load can be determined as needed. The purpose of doing this is to evenly open the water channels in the membrane.
This post was last edited by nanren2 on 2016-9-24 at 10:02. We have encountered this phenomenon before as well: when operating under high load, if the operation is shifted to low load, the acid addition rate for the electrolyzer must be reduced, otherwise the acidity level will become too high! In the electrolyzer, as the current density increases, the amount of acid added also increases (this amount refers to the ratio coefficient between the acid added and the current); this is because the degree to which the channels in the ion membrane (at the microscopic level) open is related to the current density – higher current density means that the channels open more widely, while lower current density results in less opening ； It is more related to temperature; when the temperature is high, the channels open up more, and vice versa. It is not acceptable for ion membrane channels to be either too large or too small. If the channels are too large, the ability of the fixed ions in the membrane to repel hydroxide ions is reduced; if the channels are too small, the strong binding between sodium ions and the fixed ions in the membrane also results in a decreased ability to repel hydroxide ions. This phenomenon, as perceived individually, also indicates a change in current efficiency! The current efficiency under high-current operating conditions is lower than that under low-current conditions; this may be due to the channels in the membrane being too wide. Reducing the temperature appropriately can narrow these channels and thus improve current efficiency! I would also like to ask everyone if they have encountered this phenomenon as well: that is, when operating under high load conditions, if the operation is switched to low load, the acid addition rate for the electrolyzer must be reduced, otherwise the acidity level becomes too high! This phenomenon is particularly noticeable in devices where there is no heating function for the catholyte in the electrolyzer, and where adjustments are made to the current temperature changes Therefore, it can also be concluded that at low current levels, the high current efficiency is due to the channels in the ion membrane being open; whereas at high currents, the high temperature and high electric density cause the channels in the ion membrane to open more widely, resulting in a relatively lower efficiency! Therefore, I personally believe that even when operating at high electric density, the temperature should not be too high in terms of current efficiency!