As general recommendations, I would be concerned if the TAN went above 0.2. If it gets to 0.3, you should take immediate corrective action. The compressor manufacturer may have other information on acceptable TAN levels depending on the specific application.
Carbon will not be effective in reducing the TAN. You will need something that can hold organic acids, typically molecular sieve or molecular sieve plus alumina filter driers work well. I would also be careful using filter driers with high levels of alumina as they can cause saponification of the polyolester lubricant.