Answers to common questions about reverse osmosis membrane and ion exchange resin (41-50)

41. To which compounds is the Dow FILMTEC membrane stable?

The stability of the membrane depends on many factors, such as temperature, pressure, concentration, pH, trace organic minerals (oil), bacteria, oxidants, heavy metals, and so on. Therefore, it is impossible to give specific data indicators of stability. The most effective way is to identify these potentially harmful factors before starting the system and prevent them from happening through pretreatment.

42. What are the advantages of short membrane leaf and blade multi-element structure design?

In the membrane element with many short leaf blades, the flux of the membrane surface is more uniform, so that higher water production efficiency of the membrane element can be obtained, and the possibility of pollution is significantly reduced. However, due to production technology reasons, many membrane component suppliers are still stuck in the structural design of the older generation of components, unable to make breakthroughs in this regard.

43. If the water intake of the two systems is the same, but the operating temperature is different, what is the difference in the water distribution of the membrane elements of the two systems?

The higher the water temperature, the lower the operating pressure. Although the operating pressure is reduced, it corresponds to the first element in the reference system operating at low temperatures, which will still produce higher water production. At high water temperature, the end of the system still has the same osmotic pressure, but the operating pressure is reduced, so that the membrane surface velocity of the last membrane element at high water temperature is lower than that of the low-temperature operating system. Therefore, the system running at high water temperature The non-uniformity of the flux distribution of components increases significantly, that is, the flux of components at the front end of the system is higher, and the flux of components at the end of the system is lower. This situation is not conducive to balanced and stable operation of the system.

44. What is the harm of silicon in boiler feed water?

In the high-pressure boiler feed water, the problem of silicon must be solved. This is because silicon exhibits a greater ability to volatilize with steam. Subsequently, the silicon contained in the steam will be deposited in the glass state on the turbine blades in a glassy state due to the decrease in steam pressure, affecting the turbine Flat efficiency. Both active and colloidal silicon can cause this failure, because at the temperature of the high-pressure boiler, the colloidal silicon will decompose into silicate and then evaporate into the vapor phase.

45. Can the membrane system start and stop frequently?

The membrane system is designed based on continuous operation, but in actual operation, there will always be a certain frequency of startup and shutdown. When the membrane system is shut down, it must be used for low-pressure flushing with its produced water or water that has been qualified for pretreatment to replace high-concentration concentrated water containing scale inhibitors from the membrane element. Measures should also be taken to prevent water from leaking into the system and introducing air, because if the components lose water and dry out, irreversible loss of production water flux may occur. If the shutdown is less than 24 hours, there is no need to take measures to prevent the growth of microorganisms. However, if the shutdown time exceeds the above-mentioned regulations, the protective liquid should be used for system preservation or regular flushing of the membrane system.

46. ​​Does ROSA5 include an automatic design function?

ROSA5 does not currently have an automatic design function, and plans to add this function in a future upgraded version of ROSA.

47. In the design of a three-stage system, is it possible to use the product water holding pressure in the first stage and a pressure lift pump before the third stage?

of course

48. How to design the product water back suction tank?

In the seawater desalination system, it is sometimes necessary to design the produced water back to the suction tank. The required volume is usually the volume of the pressure vessel minus the volume of the membrane element (considering the void ratio of the element).

49. How to determine the direction of the brine seal ring installed on the membrane element?

It is required that the brine seal ring on the membrane element is installed at the water inlet end of the element, and the opening faces the water inlet direction. When the pressure vessel is fed with water, its opening (lip) will be further opened to completely seal the inlet water from the membrane element and Bypass between the inner walls of the pressure vessel.

50. Can chlorine dioxide (ClO2) be used as a bactericide for membrane systems?

It is generally not allowed to use chlorine dioxide as a bactericidal agent for membrane elements. It is similar to the bactericidal effect of chlorine, but the bactericidal effect is equal to or slightly higher than that of chlorine. The difference with dissolved chlorine is that ClO2 only acts as an oxidant and does not add chlorine. Reaction, so the damage potential to the membrane is low. Some users have been successfully applied in the Dow FILMTEC membrane system, but should be extremely careful when using, because the presence of metal ions in the solution will catalyze the degradation reaction of ClO2 on the membrane, only the fungicide DBNPA is considered to be more Safe and effective, the use of ClO2 may result in damage to membrane performance.

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