Regeneration issues of small molecular sieve water removal devices
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I need to conduct an experiment recently that requires the removal of moisture from bottled nitrogen to achieve a purity of 99.9%. I am considering using molecular sieves for this purpose. The volume of the experimental equipment is around 0.5–1 cubic meter; it is filled with nitrogen at slightly positive pressure, and a fan is used to draw the nitrogen inside the equipment into a molecular sieve container where the moisture is removed. The amount of molecular sieve needed is approximately 2 kilograms. The molecular sieve container can be evacuated. My current plan is as follows: once the molecular sieve becomes saturated with water, it is regenerated by first evacuating the container, then using an electric heater inside the container to heat the molecular sieve particles. After reaching a certain temperature, this state is maintained for a while, followed by another period of evacuation, and finally the material cools down naturally. I’m not sure if this approach is feasible. If it is, could you provide some reference values regarding the heating temperature and time required? Which type of molecular sieve would be most suitable – 4A, 5A, or 13X? Thank you for your advice
Molecular sieves are used to adsorb substances with particle sizes smaller than those of their pores; larger substances cannot be adsorbed. The diameter of nitrogen is around 3.64, and 4A molecular sieves are capable of adsorbing nitrogen, so 3A molecular sieves should be used instead. If you have any further questions, feel free to message me. I have previous experience in the molecular sieve industry
Who can delete my previous replies? An enamel tank with an opening at the bottom is filled with 3A molecular sieve to dry liquids. When the molecular sieve becomes ineffective, it is removed through the bottom opening, washed with water, and the broken molecular sieve is separated using a large sieve. It is then placed in a large oven and dried at 300 degrees for 24 hours; after cooling, it can be reused
It’s totally feasible – molecular sieves are well-suited for this task. As for the specific heating temperature and time parameters, if there’s no ready-made data available, one can start with a rough idea; conduct a few experiments, and if that doesn’t work, try another dozen times :) After all, it’s an experiment, so consider it just an additional task. The above comes from someone who has been doing experiments in the chemical industry for several years
Regeneration using this method is feasible; low pressure and high temperature are favorable for regeneration. A 3A molecular sieve is used, with the temperature raised to 280°C. The heating time and number of cycles can be adjusted from longer to shorter values by measuring the gas dew point (to assess the effectiveness of regeneration)
I’m not sure what the nitrogen dew point you need is