Process conditions and control requirements for starting up a new ion exchange membrane cell (incentives may be provided as appropriate)

1. Provide the combination of the cell and membrane； Answer: Wood electrolyzer + DuPont membranes from the United States. 2. Specify the temperature and concentration requirements for the electrolyzer during operation ； Answer: The electrolytic cell must be operated in strict accordance with the operating procedures; the rate of temperature increase needs to be controlled, and the temperature difference between the anode and cathode solutions should not be too large. The temperature of the cathode solution should be kept at 50 degrees, with its concentration maintained between 27% and 29%. In the initial stage, the heating rate is controlled at around 1 hour per 5 degrees. 3. It would be best to analyze further the basis for determining the conditions ； Answer: Overall, the Woody electrolyzer features a relatively simple operating process among domestic high-current-density electrolyzers. Y-type filters are prone to getting clogged at the inlet pipes for the catholyte and anolyte. It is also important to pay attention to the rate of temperature rise within the electrolyzer; the operation procedures must be followed strictly, and the rate of temperature increase should be controlled properly. The temperature difference between the catholyte and anolyte should not be too large. Additionally, adjusting the nitrogen valve at the end of the electrolyzer is necessary to maintain the appropriate pressure difference within it. 4. Were there any abnormalities during the startup of the new membrane? ； Answer: The membrane leak test was successful before driving, but one of the ion membranes was damaged during the process of filling the system with fluid and increasing the current while driving. Other issues are not very obvious. 5. Others. Answer: After starting the vehicle, the electrolyzer voltage rises by 20–30 mV. We are currently in contact with Wood’s technical staff to discuss possible solutions; Haiyou can also share his own opinions. This post was last edited by yzhms on 2009-2-12 15:47]

1. Heat up to 75 degrees? 2. What are the concentration requirements at the beginning of driving? 3. How many hours can normal production be maintained? 4. Has the issue of membrane channel formation been discussed with the supplier?

Generally, an operating temperature of over 70 degrees is sufficient for ion exchange membranes, but Asahi Kasei’s electrolyzers can start operating at 50 degrees. Last edited by yzhms on 2009-2-13 17:56.]

Under such circumstances, what are the requirements for concentration control?

1. Provide the combination of the cell and membrane； Answer: Beihua Machinery electrolyzer + Asahi Kasei film from Japan. 2. Specify the temperature and concentration requirements for the electrolyzer during operation ； Answer: The cathode temperature is around 70°C at the start of operation; we generally keep it between 68–70°C. It is important to maintain the cell temperature at around 70°C before powering it on. The concentration of the cathode solution, which corresponds to the concentration of the final alkaline product, is 32±0.5. The anode solution temperature is 60±5°C; before powering on, the concentration during circulation is 210±10 g/l. Once power is applied, the concentration should be adjusted to that of the refined salt water pipeline, which is 280–300 g/l, with our target being around 295–300 g/l. When increasing the current during startup, the cell temperature should not rise too quickly – we control this increase at a rate of 2°C per hour. During the first startup, thorough analysis is essential, as many problems can be identified in advance through the analysis data. 3. It’s best to conduct further analysis to determine the basis for these settings ； Answer: Beihua Machinery’s tanks account for a significant share of the market in China; their manufacturing processes are relatively mature, and their prices are lower than those of imported ones. Regardless of where the equipment comes from, operation is what matters most. Following the operation manual provided by Beihua Machinery usually eliminates any problems during the first start-up. There are many factors that can affect the proper operation of the equipment, and both the basic design and the installation of the equipment are crucial. For example, if the installation company fails to provide adequate protection when welding pipes made of special materials such as titanium or 310S, or if the working environment is poor, or if argon isn’t used as required or not at all, leaks will occur after the equipment starts operating, which leads to more frequent shutdowns and increased workload – a very troublesome situation. 4. Were there any abnormal situations during the initial operation of the new membrane? ； Answer: (1) It is very necessary to carry out thorough leak tests using grooves and membranes when starting up the system for the first time. (2) We encountered a situation where the current increased too rapidly, resulting in unstable flow at the anode liquid outlet; slowing down the current rate restored normal operation. (3) To improve employees’ ability to adjust pressure differences, it is first necessary to understand what a pressure difference is and how to adjust it when it is too high or too low. (4) Analysis work during the initial startup phase must be thorough, as some problems may not be visible on the surface, but can be identified and resolved by analyzing the data – I have learned this firsthand. (5) During the early stages of operation, nitrogen replacement failed multiple times; eventually, all bypasses in the hydrogen system were replaced several times, and after multiple tests, the purity of the nitrogen became satisfactory. This is also important, as it is absolutely impossible to start the system if the nitrogen replacement is unsuccessful. (6) After the system started operating, the alkali pump (P–274) stopped suddenly. Failure to detect this issue promptly led to a low level in the high-level tank, large fluctuations in pressure difference, and automatic shutdown due to a high level of liquid in D–270. The problem was found to be with the frequency converter; originally it was a Siemens model, but it was replaced with an ABB model, and now everything is working properly. 5. Other matters. Answer: Our hydraulic system wasn’t very stable at first; the pressure would fluctuate sometimes high and sometimes low. After changing the oil after it had been operating for a while, it became normal. It’s likely that there was air or dirt in the oil. Is it necessary to invest in a voltage monitoring system connected to the DCS computer during installation? Last edited by Le Tiantian on 2009-2-13 23:09.]

1. Heat up to 75 degrees? Answer: Keep the temperature at around 80°C while driving. 2. What are the concentration requirements at the beginning of driving? Answer: Its operating concentration is kept between 27% and 29%. 3. How many hours can normal production be carried out? Answer: The drive was successful; it took only 6 hours from the start of power supply to have the entire system connected. 4. Has the issue related to the formation of the membrane channels been discussed with the supplier? Answer: According to the operating procedures provided by the design institute, it only states that operation should take place under conditions of slightly higher concentration and slightly higher temperature (the term \"slightly higher\" refers to the control parameters), but the specific methods of operation are not detailed. I’m curious to hear any good suggestions you might have.

1. Provide the combination of the cell and membrane； Chlorine Engineering + Asahi Kasei + Asahi Sales. The Japanese are bad; they gave us the new models for trial use for free. The specific model cannot be provided at the moment, but it’s really poor quality – several sheets leaked after use, so I replaced them all with those from Asahi Kasei. The quality is clearly different just by looking at it. It seems that Asahi Kasei’s product is FN-4404. 2. Specify the temperature and concentration requirements for the electrolyte during operation ； It was done in accordance with the requirements of the chlorine project. 60 degrees, then gradually increase the temperature. The concentration is 27%. 3. It would be best to analyze further the basis for determining the conditions ； Perform some verifications as required, such as leak testing, to confirm that the vehicle is ready for operation. Then, based on the procedures and experience. They all try to do it; each process is different, and none are the same. It’s fine to keep it running. 4. Have there been any abnormal occurrences while driving with the new film in place? ； Yes, the membrane has leaked. Measure the voltage in the unit slot; if it’s not okay, shut down that single circuit, replace the component, and then turn it back on. 5. Others. One drive was successful, but there were many small problems at first; I stopped the car around 30 times in the first half of the time. Things got better later on, and now I’m working hard as if it were 200 days. This post was last edited by yzhms on 2009-2-14 at 16:41.]

1. Specify the combination of cell and membrane: Beihua Machinery electrolyzer + Asahi Kasei membrane from Japan. 2. State the temperature and concentration requirements for the electrolyzer during operation； Answer: During startup, we generally keep the cathode temperature at around 65–70°C. The concentration of the cathode solution, which is also the concentration of the final alkaline product, is 32–32.3%. The anode solution temperature is 60±5°C; its concentration during filling is 210±10 g/l. During circulation, it should be switched to the concentration of brine, which is usually 280–300 g/l. When increasing the current during startup, do so gradually, and pay attention to the chlorine-hydrogen pressure difference as well as the cell voltage. 3. It would be best to conduct further analysis to determine the basis for these settings ； Answer: Proper operation of the equipment is of utmost importance. When driving the machine, it is essential to follow the instructions in the operation manual. 4. Were there any abnormal situations that occurred during the startup of the new membrane? ； Answer: No abnormalities occurred during the startup of the new membrane, but quite a number of issues did arise during normal operation. 5. Others. Answer: The key is to maintain stable operation to avoid excessive fluctuations in pressure difference

The mass fraction of the anode solution should be such that the NaCl content in the brine is within (18.5 ± 1)%, with a mass concentration of 196–205 g/L. If the mass concentration of the brine fed into the tank is too low (below 290 g/L), it can lead to a low mass concentration in the anode solution. If this mass concentration remains low for an extended period of time, the different rates of water penetration through the two layers of the composite membrane – higher in the sulfonic acid layer than in the carboxylic acid layer – can disrupt the balance of water penetration at the interface of the membrane, causing it to bubble. During operation of the electrolytic cell, the bubbles contain aqueous solutions of NaOH and NaCl; after the cell is stopped and the liquid is drained for cleaning, the bubbles contain only water. If operations are performed incorrectly or if the process of starting and stopping is frequent, it will lead to frequent fluctuations in the pressure difference across the cell, causing severe vibration of the membrane. The burrs on the weld points on the membrane frames can easily cause bubbles to rupture, resulting in the carboxylic acid layer of the composite membrane blocking OH- and Cl- ions and thus creating a \"short circuit\". This allows more Cl- ions to penetrate into the catholyte, increasing the NaCl content in NaOH and reducing the current efficiency. If bubbles form on the membrane but it does not rupture, their impact on current efficiency and the NaCl content in NaOH is minimal.

1. Provide the combination of the cell and membrane； Answer: Asahi Kasei electrolyzer + Asahi Kasei membrane. 2. Specify the temperature and concentration requirements for the electrolyzer during operation ； Answer: The cathode temperature is around 60°C at startup; we usually keep it between 60–70°C. The cathode concentration is 32±0.5%, while the anode solution temperature is also 60°C. Before powering on, the concentration is 290 g/l, as we do not use diluted salt water for switching. When increasing the current during startup, the temperature of the cell should not rise too rapidly; in other words, the rate of current increase should be relatively slow. Once the current reaches 0.5 KA, it is necessary to monitor the voltage of each cell, as well as the condition of the hoses and the flow rate. 3. It would be best to conduct further analysis to determine the basis for these settings ； Answer: The tank temperature is controlled at 85–90 degrees; the resistance is relatively low, and the tank voltage is also low. 4. Were there any abnormalities during the startup of the new membrane? ； Answer: (1) Groove testing and membrane testing are very important. (2) Improve employees’ operational skills to prevent large negative pressure differences from occurring. (3) Strengthen central control analysis to ensure that the alkali concentration is within the acceptable range. (4) Nitrogen purging is crucial; it is absolutely not permissible to start the system if the purging is not done properly.

1. Provide the combination of the cell and membrane； Answer: Asahi Kasei electrolyzer + Asahi Kasei membrane. 2. Specify the temperature and concentration requirements for the electrolyzer during operation ； Answer: Before filling with liquid: The cathode temperature is around 60°C, the concentration is 30–32%, and the temperature of the brine in the resin tower is 65°C. Pure water or dilute brine is added to the tank. Power supply is initiated once the temperature in the filling circulation tank rises above 70°C. The current increase rate is generally recommended to be 200–300 A/min; unless there are special circumstances, no prolonged stay is usually allowed at a current density below 1.5 kA/m2. Normal operation: Tank temperature 86–89°C, brine temperature 60°C, concentration 300–315 g/L; concentration of brine exiting the tank 195–215 g/L, pH 2–2.5; concentration of alkali exiting the tank 30–32 g/L, chlorine pressure 35 KPa, hydrogen pressure 39.5 KPa, pressure difference 4.5 KPa. 3. It would be advisable to conduct further analysis to determine the basis for these parameters ； Answer: Before feeding the liquid in, the temperature difference between the liquids should not be too large. Since the brine needs to be diluted with pure water, its temperature is kept a bit higher; during circulation, the temperature of the liquid is increased further, and once everything is operating normally, the temperature of the brine drops to 60°C. A caustic concentration of 30% is sufficient for driving, as no pure water has been added yet since the current is below a certain level. 4. Were there any abnormalities during the startup of the new membrane? ； Answer: (1) No acid was added after operation, resulting in unsatisfactory dechlorination effect ； This post was last edited by yzhms on 2009-2-26 14:51]

1. Provide the combination of the cell and membrane； Answer: Beihua Machinery electrolyzer + Asahi Kasei film from Japan. 2. Specify the temperature and concentration requirements for the electrolyzer during operation ； Answer: The cathode temperature is around 70°C at startup; we generally keep it between 70–72°C. The cathode concentration is controlled at 32±0.5%. The temperature of the anode solution is 60±5°C. The concentration of the anode solution during circulation before power application is 210±10 g/l, while the concentration in the refined salt water pipeline after power is applied is 280–300 g/l. 3. It would be best to analyze further the basis for determining the conditions ； Answer: The electrolyzers produced by Beihua Ji account for a significant share of the use in China’s ion membrane industry. Generally speaking, they are relatively inexpensive, utilize Asahi Kasei’s traditional manufacturing processes, and their technology is fairly mature. However, their lifespan is relatively short – leakage problems become severe after 3 years of use, and the coatings on the anode and cathode also suffer considerable damage. Overall, their performance is inferior to that of Chlorine Engineering and Woody electrolyzers. 4. Were there any abnormalities during the startup of the new membrane? ； Answer: (1) When driving the vehicle for the first time, we carefully carried out groove leak testing and membrane leak testing. (2) To prevent too rapid an increase in current, our factory strictly controls the rate of current increase during startup. (3) There were fluctuations in the flow rate of the pipeline carrying pure water to the catholyte solution, but since it was detected in time and appropriate actions were taken, no losses occurred. Please be mindful of this point every time the system is started up.

1. Provide the combination of the cell and membrane； Answer: Beihua Machinery electrolyzer + Asahi Kasei film from Japan. 2. Specify the temperature and concentration requirements for the electrolyzer during operation ； Answer: At a temperature of 80, the concentration remains stable for 8 hours; at 30%, it stays stable for 72 hours. It would be best to conduct further analysis to determine the basis for these conditions ； When driving a membrane for the first time, if the temperature is too high while it has not been fully extended, this can have irreversible damage to the membrane. Asahi Kasei requires that the concentration used during the first use of such membranes not be too high. 4. Were there any abnormal occurrences during the initial operation of the new membrane? ； None

On the 7th floor, the concentration of brine when it enters the tank via vehicle should be no less than 190 g/L, right?

Nippon Asahi Kasei Films: The initial operating current density for the new film is set at 4.0, and this value is maintained for 72 hours; after that period, a higher load can be applied.