Why does the catholyte need to be heated when the electrolyzer in chlorine production operates at an electric current density of 4.5 KA/M2?

Personal opinion: Asahi Kasei’s electrolytic cells are not strict regarding cell temperature; a value below 88 (90) is sufficient. When driving initially, the maximum tank temperature was probably around 70°C. The cells in chlor-alkali plants require this at least in terms of the design of their operating processes. A relatively stable temperature is required. From the very beginning, when driving, a temperature of over 80 degrees was required. Last edited by sister on 2008-11-29 08:20]

It’s not necessary to heat it; what’s important is to maintain the temperature of the tank. If that temperature can be achieved, then heating isn’t required

Since the brine entering the tank comes directly from the resin tower and its temperature remains constant, heating is necessary if the tank temperature is to be maintained at around 88 degrees under rated load.

What I would like to discuss with everyone is why Asahi Kasei’s electrolyzers need cooling under this load, while the chlorine processing system requires heating! ! 1

Factors affecting cell temperature: 1. Cell type 2. Current density 3. Anode solution flow rate 4. Anode solution temperature 5. Cathode solution flow rate 6. Cathode solution temperature 7. Electrolysis area of the cell 8. Electrode service life 9. Diaphragm service life 10. Anode solution concentration 11. Cathode solution concentration

1. For any type of battery cell, the cell temperature and operating current are directly related: a higher current results in a higher temperature. 2. I’m not very familiar with the tanks used in chlorine processing, but for the tanks used by Asahi Kasei NCH, the temperature inside these tanks is relatively low at the time of initial operation (when comparing under the same current level). Moreover, to prevent the gaskets from being damaged, it’s best to keep the tank temperature below 80 degrees on the first day; in other words, the current level should not be set too high ； As is well known, there is a direct relationship between slot voltage and slot temperature; different suppliers use different coefficients for this purpose. Some manufacturers heat the catholyte at the beginning of operation or during winter in order to achieve a lower voltage ； However, as the age of the cell and the membrane increases, the cell temperature rises gradually under the same conditions; therefore, even in winter, it is sometimes necessary to cool the catholyte ； 3. In my opinion, heating the catholyte to raise the tank temperature and reduce power consumption requires an economic analysis taking into account current coal and electricity prices; otherwise, it will be more costly than beneficial.

The tanks we use for chlorine processing, as mentioned above, don’t necessarily need to be heated; what’s important is to maintain a certain temperature inside the tanks. Ensuring the tank temperature can reduce the tank voltage. It can also improve current efficiency. Actually, I asked other factories about temperature issues; some of them continued to operate their equipment even after stopping steam supply for half a month, so the most important thing is still to maintain the temperature in the tanks. :handshake Last edited by limingshuguang on 2008-11-30 21:27]

Yes! In the electrolyzers designed by Asahi Kasei, the catholyte E273 does not include any steam heating pipelines at all. The design philosophy behind this is that even when the load on the electrolyzer is low, its temperature will still be higher than that of the saltwater fed into it. The saltwater fed into the electrolyzer, along with the recycled fresh water, has a temperature of over 70 degrees; when electricity is applied for electrolysis, the temperature reaches at least 75 degrees, even at a current level of 5.0 KA. This design takes into account the properties of Asahi Kasei’s membranes! Asahi Kasei Film is less affected by temperature; its coefficient of thermal expansion is lower at different temperatures compared to the other two companies. Therefore, when filling the Asahi Kasei electrolyzer, both the alkali solution and the brine are introduced at high temperatures, after which power is applied to start the operation. However, the ion membranes of the other two manufacturers are generally highly sensitive to temperature; therefore, it is necessary to fill the tank with low-temperature alkali and brine (usually alkali solutions and brines at temperatures below 65 degrees), and then gradually increase the temperature, in order to prevent the ion membranes from suffering local damage due to sudden exposure to high-temperature electrolytes ! If the ion membrane electrolyzer you are using is one manufactured by Asahi Kasei, and the E273 model does not come equipped with a steam pipeline – but it is not an Asahi Kasei ion membrane electrolyzer – it is advisable to install a steam pipeline on the E273 model in order to control the temperature of the electrolyzer during operation at low currents! The temperature of the electrolytic cell is generally maintained between 85 and 89 degrees. If a lower concentration of alkali solution is required, the temperature of the cell must also be lowered; in other words, within the range of 85–89 degrees, lower alkali concentration corresponds to a lower cell temperature, while higher alkali concentration corresponds to a higher cell temperature. Of course, this is within acceptable limits! Only in this way can the ion membrane maintain its fixed geometric dimensions and remain undamaged! ! This post was last edited by limingshuguang on 2008-12-4 09:35.]

The question raised by the original poster is worth exploring. In the chlor-alkali cells we use, a cell current density of around 4 kA requires steam heating in order to maintain the cell temperature above 88 degrees. Could it be that there are specific technical considerations in the design of chlor-alkali cells and Asahi Kasei’s cells to address this issue? Could an expert please advise whether there is any difference in the circulation rate of the anode solution depending on the type of groove? This post was last edited by rensheng0321 on 2008-12-31 07:08.]

In practical operation, the two factors that have the greatest impact on cell voltage are cell temperature and the concentration of the circulating alkali solution; generally, the cell temperature is controlled between 85 and 90. The tank temperature is too low, and the tank pressure is high. The cell temperature is too high; the electrolyzer cannot handle it. Last edited by limingshuguang on 2009-1-1 11:22.]