Mr. Norman Lieberman – What does it indicate if we have a gradual increase in CO2 in the vacuum tower waste gas to the vacuum heater? A year ago the CO2 concentration was one percent and now it is ten percent. Our vacuum is still quite acceptable. Also, the nitrogen (but not oxygen) concentration of the waste gas stream is also increasing, which I assume indicates an air leak.
--Carl
Carl – You most likely have an air leak in the vacuum heater transfer line feeding the vacuum tower. The leak is getting progressively worse. Since the leaking line is under a slight vacuum, relatively small amounts of air are drawn into the vacuum tower. The oxygen then reacts with the hydrocarbons to form CO2 (and perhaps some CO). Regardless, if you have a sudden loss of vacuum, the area of the leak will pressure-up. Hot vacuum tower feed will erupt from such a leak and auto-ignite. This is a very dangerous situation and I’ve been involved in such incidents three times in my career.
I don’t really know how to advise you. Shutting down to repair the leak in the transfer line may very well result in a fire. One of my clients burned down their vacuum tower due to such a failure. Sorry for the bad news, but I believe my analysis is quite accurate.
--Norm
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