Only thing I know of to control moisture in an air tank is drain the air daily.
You might find a pop off valve similar to what is on a compressor on a semi truck. Not only does it control the air pressure in the tanks because the compressor always runs as the engine does, but it blows moisture out in the process. I'm no expert on this subject but if I had your problem I think that is the first thing I would look into. I do know that all air compressed from the atmosphere has water in it which separate's when compressed and will find it's way to the lowest point in a system. I felt the need to reply as no one else has yet. Hang in there and maybe someone else with your problem will help out. Good luck.