methane absorption in TEG

[I2P]

We have a tri ethylene glycol dehydration contactors and regeneration units for the same. I have read some literature from US Env. Protection agency regarding the methane losses in glycol operated dehydration towers. Since we are also in the processes of optimisation of dehydration operations, I would like to know how to exactly quantify the cubic ft of methane absorbed per gallon of glycol circulated.While it is true that low temperature favours water absorption, it also leads to hydrocarbon absorption and thus the need to work out the inlet gas temperature which would give the desired dew point depression and minimise the methane loss. Presently we are operating at an inlet temp of 45 to 47 deg c, with an inlet water content of 90 lb/mmscf and outlet content spec of 7 lb/mmscf. Tower pr. is 65 bar.Our design temp range for gas inlet temp is upto 55 deg C. How much of methane absorption would I be preventing if I raise the inlet temp to 55 deg C?
thanks in advance

 

[ThinkPad0]

What's the TEG circulation rate? Have u checked for BTEX in feed gas / regen vent? R u using any stripping gas? CAA specifies the limits of emissions from glycol plant. CAPP has a gr8 compilation on Best Management practices on BTEX emission.
The right approach in your case would be to reduce the inlet temp and reduce the TEG circulation rate to a minimum permissible.
Regards.....

 

[Chemeng1122]

I cannot quantify the amount of C1 adsopbed by the glycol, but I do know that it is relatively small, assuming that the contactor is in good mechanical conditions (chimney tray, valves, downcomers, LCV controls, etc).

ThnikPad mentioneda very good point in BTEX emissions. BTEX is a much greater concern then C1 in the dehy because TEG does have a tendancy to absorb these aromatic compounds, but a very low adsorbtion capacity for straight chain hydrocarbons.

Any C1 that you do absorb would be mainly because of high circ rates or perhaps losing the liquid seal in the contactor, which is very rare unless the contactor is in extremly poor shape.

Andrew Lechelt
Technical Support Engineer
Quadra Chemicals

http://www.quadrachemicals.com