TEG Contactor Efficiency

[B62plant]

Anyone give me rough idea of the efficiency of a TEG dehydration system ? For example if I have 10 lbs/mmscf of water in the inlet gas what should I get out ? I'm thinking it should be 1 lb/mmscf and the efficiency is 90% ?

 

[georgeverghese]

For packed columns,
a) Calculate the NTU required (no of transfer units required to reach a given exit water concentration for the given TEG flowrate and inlet lean TEG concentration)
b) Compute the HTU - this will be a function of the contact surface area / m2 of packing

Total packed bed height H = NTU x HTU x 1.1

Else use the Kremser Brown procedure to get the no of theoretical plates; then compute the bed height from
H= N x HETP x 1.1 where HETP = height equivalent to one theoretical plate

Use the design resource guidelines you have to compute these.

 

[B62plant]

Thanks, yeah I know this but I don't have the data. I could get it but I was just looking to see if anyone had any idea from experience of a rough efficiency of a typical system. It's not critical enough for me to spend time doing the calcs.
I was thinking about 95% removal of entrained water ?

 

[georgeverghese]

These questions you ask dont yield easy answers - work to get each parameter carefully. A shot in the dark on contactor eff also doesnt help when you get audited.

 

[B62plant]

I don't need too much accuracy so I've took samples of lean and rich TEG .. 0.8% and 7% ... I can work out a rough efficiency from this

 

[georgeverghese]

If you these values, then it may not be too difficult to get a good estimate of the exit gas water content. Use simple mass balance to get the exit water content in the gas, provided you have the following parameters also
a)Wet gas flow to the contactor, dry basis
b)Wet gas inlet water content
c)Lean TEG flowrate, dry basis

Careful with the wet gas water content, especially if you have high CO2 and or H2S at high pressures - see the GPSA for correction factors, or extract these from your process simulator with an appropriate EOS.