Anhydrous ammonia contamination of compressor oils

your oil can be reclaimed with a filter cart made by harvarad corporation. Or you could put a filter system on the compressor that will clean the oil and keep it clean as you operate the system. look up thier website. the filter will remove particals down to 1 micron and moisture in the oil as well.

There are oil stills commonly available for large refrigeration systems. The still will strip off the refrigerant so you can return the oil back to the compressor without excessive dilution. The stripped off refrigerant is fed back into the condensing unit and reused as well. The design of the still is very simple - a pot with an electric heater, correctly plumbed into the system.

I advise you to consult with a large mechanical contractor that deals with ammonia refrigeration systems to get more details.