Friday, July 10, 2009

Compressed air dryer / nitrogen generator

In my last post, I described designing and welding a pressure vessel for a compressed air dryer. I'll describe the completed dryer in the this post.

The purpose of this project is to take dirty, oily, damp air from a compressor, and provide very clean, very dry nitrogen to the liquid nitrogen generator.

The airflow path is as follows:

Air inlet -> mechanical filter -> carbon filter -> air dryer #1 -> air dryer #2 -> carbon filter -> mechanical filter -> humidity sightglass -> nitrogen membrane -> flow valve -> output

Oil vapor is a big problem when using conventional compressors with systems that rely on having clean air. Mechanical filters are not able to capture all of the oil odor, so that is why I also included activated carbon filters. I made these filters out of Harbor Freight pneumatic oilers. I gutted the oilers, added some filter material, rearranged the airflow path and threw in some activated carbon. Even though the photo shows the two filters joined together, this is just a mechanical connection -- each filter is actually plugged off. The flow goes between the bottom of the bowl and either the left or right outlet.

The whole system is fitted with 1/4" compression fittings.

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