Combustion Temperatures of BTEXs

[RRE]

A colleague is looking at installing a combustion burner to burn the BTEXs (benzene, toulene, ethylbenzene, and xylenes) from a TEG glycol still. The combustion device has a 400F temp shutoff. For some reason, this temp seems low to totally combust BTEXs. (The project team prefers combustion over condensing the BTEXs). Any help is appreciated.

 

[NeedAHoliday]

RRE,

(This is a copy of my post from Heat: Combustion Engineering)

We had a D&C project for destruction of BTEX. We have a operating combustion temperature of ~800C (1472F) to give 99.9%+ efficiency. Generally you need to be above a minimum of 650C (1200F) for any chance at a higher degree of destruction for BTEX, but this will depend on several other factors.

An important thing to keep in mind is the %conc of combustable material in you off gas as you need to maintain below 25% LEL to be able to put any sort of energy source near your gas stream, and TEG has a LEL of 0.9%vol (UEG is ~9.2%vol) which is generally below the compounds in your BTEX mixture (LEL of BTEX is around 1-1.9%vol), so you may have a problem there as, so far I have had to dilute in almost all cases the inlet gas stream where I have had BTEX present due to the nature of the processes.

Besides this it appears as though you want to try and destroy the BTEX without effecting the TEG. Your BTEX has a lower boiling point obviously to the TEG however BTEX has a higher autoignition tempetature to the TEG. Realistically I don't see how you can achieve destruction of BTEX to any great degree without degrading/destroying the TEG.

As the boiling point of TEG is about 285C (545F) and the BTEX is in the order of 80-150C (176-302F) it appears as though the best option is to condense the BTEX if you want to save the TEG. There may be other technologies out there that can target the BTEX without compromising the TEG but I'm not familiar with them.

K.

 

[augiedog]

We have used elevated incinerators to dispose of H2S and BTEX in the TEG still effluent (overhead line from still sloped back to the still from the nozzle on the vertical incinerator so any condensed water runs back) with good results, and this is probably your best approach. We used fuel gas on temp control to maintain the 1200°F mentioned above.