Q & A > Question Details
We monitor the VOC emission comes from our VR, Asphalt and MCB(Main Column Bottoms from RFCC) tanks regularly, and found the VOC emission range from several hundreds to several thousands ppmv.
These tanks are fixed roof design followed API code.
The VOC contains C1, C2 and C3 compounds mainly, and trace sulfur compounds with bad smell.
Since we have successful experience of caustic scrubber installed downstream of tanks to remove trace sulfur compound (i.e. H2S). We plan to install a downstream scrubber to improve this situation. Would you please advice which solvent is suitable for this application (for light hydrocarbon removal from vent), or other system can be used?
03/01/2012 A: Morgan Rodwell, Fluor Canada Limited, morgan.rodwell@fluor.com
If the tanks are blanketed with natural gas, I would collect the vent with a vapour recovery system and return to the fuel system. If they are not blanketed, and this mixture contains air / hydrocarbons, there is significant explosion hazard. I would recommend blanketing the tanks. If it is blanketed with nitrogen, then you "could" recover the hydrocarbon using a solvent like heavy naphtha or kerosene, but you would need to keep it cool to get good recovery.
03/01/2012 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
I have seen activated carbon canisters used successfully to remove hydrocarbons from tank vents.
You might also be able to use something like diesel feed to a hydrotreater to scrub the light hydrocarbons out of the tank vents. At one refinery I worked at we put a layer of diesel in our sour water stripper feed tank to help control tank emissions and that worked well. You can't put diesel in these tanks but in an external scrubber it might work. The diesel leaving the scrubber, would need to return to a process that will strip the light ends back out. That's why hydrotreater feed makes sense, since the product strippers already in use will serve that purpose.