4 replies to this topic

[fra.telli]

Hi everybody.

for a natural gas plant, I'm considering a silica gel unit for hydrocarbon dew point control (C6+ remouval - and "occasionally" dehydration).
Sorbead H or similar...
unfortunately, production profiles ranges are very wide: 1.0MSm3/d to 0.3Msm3/d
My question is: which should be the allowable gas flow turndown for the treatment unit?
Regeneration may be realised with 15-20% of dry&hot gas flow... so 20% is the maximum allowable turndown of this sistem? If you can regenerate silica gel bed with 20% gas flow, maybe 20% gas flow is the minimum allowable working flow even during absorption...
Sound reasonable to you?

Any comment is wellcome
Thank you

[Art Montemayor]

Fratelli:

Benvenuto.

Correct me if I am wrong in interpreting your query. I believe what you are considering is using an adsorption process to selectively adsorb C6+ components from natural gas and to also dehydrate the product (simultaneously adsorb water molecules as well). Simultaneous adsorption of hydrocarbons and water can be done, but I'm afraid you will have problems using adsorbents such as Sorbead H or silica gel. I believe you have to resort to using an "engineered" adsorbent – such as Molecular Sieves – to do what you describe. Mol Sieves are more expensive and require a higher energy input for regeneration. Regeneration temperatures can run as high as 700 oF and consequently require more expensive materials of construction.

Depending on what your proposed regeneration cycle and process looks like, you might not run into any problems with a turn-down ratio. Adsorption systems are very simple and direct Unit Operations. They can usually be turned down to ridiculously low rates – depending, of course, if you can maintain a constant available regeneration gas stream of adequate size and temperature. Therefore, your regeneration gas source is a critical factor in determining your regeneration capabilities.

Try to draw or sketch your cycle configuration. For examples of how this is done go to other threads on our Forums where this subject has been discussed in detail. You can use our "SEARCH" feature by keying in adsorption. Some example threads where you will find complete illustrations are:

http://www.cheresources.com/invision/index.php?showtopic=3859&hl=adsorption

http://www.cheresources.com/invision/index.php?showtopic=5890&hl=adsorption

http://www.cheresources.com/invision/index.php?showtopic=3400&hl=adsorption

Who would process design this proposed adsorption unit?

I hope this has been of help to you.

[Zauberberg]

SORBEAD/SORDECO units can be used for simultaneous dewpointing and dehydration, at least according to the information I have from process vendors. Together with H2O, mercaptans will be co-adsorbed in solid bed as well (if they are present in the gas stream), due to similar molecular structure to H2O.

[SORSinger]

Hi everybody.

for a natural gas plant, I'm considering a silica gel unit for hydrocarbon dew point control (C6+ remouval - and "occasionally" dehydration).
Sorbead H or similar...
unfortunately, production profiles ranges are very wide: 1.0MSm3/d to 0.3Msm3/d
My question is: which should be the allowable gas flow turndown for the treatment unit?
Regeneration may be realised with 15-20% of dry&hot gas flow... so 20% is the maximum allowable turndown of this sistem? If you can regenerate silica gel bed with 20% gas flow, maybe 20% gas flow is the minimum allowable working flow even during absorption...
Sound reasonable to you?

Any comment is wellcome
Thank you

[SORSinger]

SORBEAD H is fully suitable for hydrocarbon dewpoint control. If water is also present, Sorbead WS may also be recommended. SORBEAD is now part of BASF if you are looking for vendor assistance...

As for your question about minimum flow, I would suggest the general guideline of ensuring you maintain at least 0.01 psi/ft of bed pressure drop. This will ensure turbulent flow. Simply stating a % flow as a rule of thumb can lead to trouble.

I hope this helps...

SORSinger