Hydrogen recovery hollow fiber membrane

Your membrane separator is damaged. Different membrane separators use various materials; Tianbang Company of Dalian Institute of Chemical Physics uses polysulfone, while Pemeia uses polyimide. These two materials have different tolerances to ammonia. For pure gaseous ammonia, polysulfone can tolerate levels of 200 ppm or less, while polyimide can tolerate levels of 10 ppm or less. For an ammonia solution at a concentration of 10%, the membranes made of polyimide material will dissolve directly in the ammonia, while polysulfone membranes will not dissolve; however, their performance will be affected and their separation efficiency will decline. When pure liquid water enters the membrane separator, it can cause the head on the permeate side of the membrane separator to crack due to the swelling effect of water. I don’t know which factory you work for, but if liquid is detected in the ammonia washing tower, the machine should be stopped immediately; it can be restarted only after the liquid issue has been resolved.

1. The tolerance level for membranes has always been expressed in PPM, but it’s not clear whether this means that levels below XX ppm can be ignored without any issues, while levels above that cause damage; or whether the amount of time the membrane operates at XX ppm determines the degree of damage until it finally becomes unusable ! I hope experienced folks can offer guidance; it would be best if the best phrasing had a source. 2. Our membrane is from the Japanese company UBE; it should be made of polyimide. However, when the distributor checked with UBE, they stated that the ammonia tolerance level is 100 ppm, with 50 ppm being the allowable level for use in the membrane (in my opinion, 50 ppm is completely unacceptable).
3. I soaked the broken membrane fibers from UBE in ammonia solution – about 10% concentration – for around 20 seconds, and there was no visible reaction. 4. The membrane produced by the Dalian Institute of Physical Chemistry (is this polysulfone? There is no impact after introducing liquid (water flows out loudly once it’s placed behind the membrane); the permeate flow rate of UBE decreases by 40% after introducing liquid

Reply to 1# iamduyuming: I’m not sure which one of the membranes is damaged in your case; we also have a damaged membrane, but it’s the second one.

1. The tolerance of membranes to ammonia is basically determined by the respective membrane separation device manufacturers themselves. It can be said that ammonia does have an impact on the membrane fibers. In my opinion, the ammonia concentration specified in ppm levels is sufficient to ensure that the membrane separator will not get damaged or experience a decline in performance due to excessive ammonia levels within the time frame specified in the contract. However, operating the membrane separator for extended periods in an environment with ammonia present will definitely lead to a decline in its performance. There are many reasons for such a performance decline over time, such as prolonged exposure to air currents and the condensation of water vapor on the surface of the membrane fibers; in these cases, ammonia accounts for a relatively small proportion of the factors contributing to the performance decline ； 2. I don’t find the results from the dealer’s inquiries very credible ； 3. If that membrane filament is soaked for a longer time and at a higher temperature, the reaction time may be reduced ； 4. I’m not sure whether the sound of water flowing behind the membrane you mentioned refers to the membrane from the Institute of Chemical Physics or that from UBE; relatively speaking, the membrane from the Institute of Chemical Physics has greater tolerance ；

1. The contract stipulates a one-year warranty period for the membrane. If the ammonia level is above the specified limit, as long as the increase isn’t severe, the membrane can generally still be used properly within the warranty period; however, its performance will gradually decline. As for the issue of a normal service life of ten years, as long as the ammonia level remains within acceptable limits, the ammonia washing process is stable, and there are no operational problems, then a ten-year usage period is entirely feasible. In China, several users have been using membrane hydrogen production systems for over ten years; one of these users experienced an ammonia leak due to an operational error at first, but it was detected and addressed promptly. Since the year 2000, that system has been in use to this day, with its performance remaining essentially unchanged. 2. It can be said that if the ammonia washing is done properly, the lower the ammonia content, the longer the normal service life of the membrane – sometimes even far exceeding the theoretical 10-year service life. Whether it is a domestic membrane, a Japanese membrane, or an American membrane, the lower the ammonia content, the longer its service life. 3. Regarding the issue of a membrane’s tolerance to ammonia, I believe users should not subjectively judge the quality of a membrane based on its ability or inability to withstand ammonia. If proper ammonia treatment is carried out, then the ability to resist ammonia cannot be used as a criterion for assessing the quality of the membrane. Would you use the ability of a car to run on 90-octane gasoline as a standard to determine its quality when buying a car? For similar items, a slight increase in precision may require not just a slightly higher standard for the manufacturing and usage environment as well. 4. Regarding the user’s question about which membrane is damaged, I have some doubts. Domestic membranes are generally connected in series; if the issue lies in an excessive ammonia level, how could only the second membrane get damaged? Both membranes should be damaged at the same time, with the first membrane either being the most severely affected or the least so (it’s not possible to determine for now whether it’s more severe or less). When a set of membranes processes the same gas, it’s unlikely that just one membrane would get damaged without any reason. Can anyone provide an explanation? 5. We have not conducted experiments to determine whether polyimide films dissolve in dilute ammonia, but it is certain that they will not dissolve within one or two hours. When the ammonia level exceeds the limit, damage to the Prisen membrane manifests as a change in the color of the membrane fibers and increased brittleness. There was once a customer in Yunnan who used a Prisen membrane hydrogen production system. During the commissioning process, the system met all the required specifications and operated normally. However, a few months later, the customer claimed that the membrane was damaged. After experts confirmed that the membrane indeed had been damaged, they opened the housing and found that the entire membrane module consisted only of one end cap, which was blackened; all of the membrane fibers had turned into residues that resembled something like burnt fibers (similar to paper turned to ash). To date, this phenomenon has occurred only once, and the cause remains unknown. It is speculated that some organic solvent may have gotten into the system or that the membrane was exposed to high temperatures.

I would like to ask how much damage back-filming can cause to membrane separators

The Prisen II membrane used by Bermia is made of polyimide, with a requirement that the ammonia content be below 50PPM; liquid water can cause the membrane fibers to break. Reduce the permeate gas volume to lower the recovery rate.