Glycol dehydration plant salt problem 3

[tincap]

Salt carryover is causing problems in a triethylene glycol (TEG) dehydration plant. I have graphs for NaCl and for CaCl2 solubility in TEG from the oil and gas journal. Does anyone know of any data for mixes of salts in TEG (or for that matter MEG), or of any general sources of data relating to salt solubility in glycol.

(we're attempting to alleviate the carryover problem, and are looking at mobile clean up options for TEG, but I'm trying to determine what the limit of salt is. The general rule of thumb is that TEG needs to be reclaimed or replaced when its salt concentration reaches 1%. I'd appreciate any advice).

 

[mb44]

Have you spoken to the TEG package vendor?

mb

 

[jay165]

My reference book (Oilfield Processing of Petroleum, Vol. 1 by Manning and Thompson) recommends a value of 2500 ppmw (approx. 1/4 what you're using) as a maximum acceptable value of salt concentration in TEG. The authors state that salt deposits cause heater tube hot spots and fired tube failures (assuming you have a fired tube reboiler).

Hope this helps and that you find the source of your produced water carryover.

 

[homan0135]

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[tincap]

mb44 - am talking to vendors.

Thanks jay165. One problem is that NaCl has inverse solubility with temperature (CaCl2 other way round). NaCl comes out in lean TEG during the hot part of the regen. CaCl2 comes out at cooler temps. Some references state that you can operate at 1% salt in TEG (but don't state what salt). My own research suggests that this may be possible for CaCl2 but not for NaCl. I suspect that the 2500ppmw in Manning may refer to NaCl.

I'd appreciate any other insight anyone may have regarding salt solubility limits in TEG.

 

[MGlycol]

The solubility of sodium chloride in TEG solutions in a normal operating range is the following:
Temperature °F TEG % by wt. NaCl % by wt.

50 90 5.2
50 95 4.5
50 100 4.3
100 90 4.8
100 95 4.0
100 100 3.5
150 90 4.3
150 95 3.5
150 100 2.8

With reference to calcium chloride, I know that with a glycol solution at 95% the CaCl content is 1% at 100 °F. For more information on the solubility of salts in glycols try to contact the Dow Chemical Company 2020 Dow Center, Midland, MI 48674, 1-800 / 447-4369

 

[tincap]

Thanks MGlycol. The data you tabulate for NaCl agrees with the charts that I have from an article in oil and gas journal. Do you have a reference for your values.

 

[MGlycol]

Dear tincap,
my reference is "Gas conditioning fact book" by Dow Chemical Company.
Regards
MGlycol

 

[bewdley]

My company is now commissioning a MEG plant where brackish water is carried over.
Besides solubility, there are other considerations to take into account, e. g. supersaturation, variability of salt content and nature, variable EG concentration.
No simple task if I may say.