4 replies to this topic

[Andalus Knight]

Dear All,

 

i have a TEG unit that can Treat 60 MMscfd of gas @1200 Psi , 130 f 

 

can it work with 3 MMscfd of gas @190 Psi , 88 f

 

please help

 

Best regards,

Andalus knight

[Art Montemayor]

^Andalus:

^{It might.  You would be using a lot of absorber packing needlessly - and very inefficiently.  You would have to modify the internal packing of both the absorber and the stripper.  You would also have to either slow down your circulation pump or buy a new one.  You would have to plug some tubes in your TEG exchangers.}

 

^{All of the above modification work would be only justified if you could successfully simulate the design (on ProMax) for operation at the 190 psig condition while obtaining the dewpoint you want on the product gas.  I don't think anyone on this Forum is going to do that for you.}

 

^{I have operated both 70 MM Scfd and 5 MM Scfd TEG units at 1,000 psig and ambient temperature and the physical size difference  is such that I wouldn't try what you are suggesting.  For such a small stream, I would either use calcium chloride dryers or adsorbers - whichever would comply with the product dewpoint desired.}

[gazepdapi1]

Art, why do you say you would have to slow down the pump? If he has packing inside the contactor, this shouldn't matter right?

[Art Montemayor]

 

Nertil1:

 

What is being proposed is a greater than a 20:1 turndown ratio.  And I am not correcting it for the low pressure effect either.  This is a tremendous turndown demand.  If I estimate it correctly (and here, I ask Andalus to tell us the dimensions of his contactor and regen towers) Andalus has a 2 - 2.5 meter diameter TEG contactor and he only needs a 0.75 meter contactor.  The TEG flow rate for the 70 MM Scfd case is normally very low to begin with (approx. 8 to 10 gpm); the required TEG flow rate for the 6 MM Scfd case is going to be so low that excessive channeling will take place (yes, even in structured packing).  The result will be that the contactor will be impossible to control in order to obtain the desired product dew point.  You have to ensure that ALL the gas comes into intimate contact with ALL the TEG.  I don’t see this happening in the existing contactor and the lower flow rate.

 

What would have to be done in order to control the absorption in the contactor is to reduce the internal diameter in the same by constructing an inner tube (and creating a dead space annulus) and installing the packing in the inner tube.  This is a LOT of modification work.  I’ll bet I could make a better and less expensive solution by using an old, scrapped pipeline 30-ft section, pack it and use that as the contactor.  With only 200 psig pressure, this would fit in conveniently.

 

I would also replace the relatively small stripper with another smaller pipe section and plug the excessive tubes in the heat exchangers.  If plate heat exchangers are being used, this is even easier.  The excess plates would be removed.  The pumps would be replaced with very small gear pumps.

 

[gazepdapi1]

Ok I see. I have noticed this on very low flow rates the water content does come up a bit but I always though that since the glycol is flowing as a thin film on the packing, gas flow rate wouldn't matter as it would be contacting the TEG anyways.