[BobHawker]

Hi everyone,

I represent a trading company that supplies TEG to oil & gas companies for gas dehydration purpose.

Our last delivery has problems in that the enduser reported that they were reading 8.1 pH for rich glycol and 9.7 for lean glycol which exceeded their target range.

They then tested the pH which we supplied which comes out at pH 8.4 and they claim that this exceeds our specification of 6.0-8.0

If the the 8.4 TEG is returned to us, is there any method to reduce the pH to below 8.0?

Please bear in mind that I'm not from chemistry background, thank you for any advice offered.

[Arkcon]

First of all, you'll want to verify their results.  They could be wrong.

Second of all, what are your specifications?  If you really guarantee no more than 8.0, didn't you check first before shipping?  How do you test?

What else in in your triethylene glycol?  Does you supplier need to do a better job of purifying it?  Or did your company make it?  What do your engineers and chemists say?

The pH of a non-aqueous solution is, at best, a little dicey -- sort of a hit or miss result depending on the method used.  At worst, totally invalid, but on some levels this is a personal point of view.  At any rate, you may want to titrate to determine exactly how much alkali is there.  You'll want a chemist for this, and also to decide how to best neutralize the product and still have it work.  Although I'd bet re-purification would work best.

[BobHawker]

Hi Arkcon,

Thank you very much for your reply.

The pH reading of 8.4 by client was correct as we just did a sample testing by a 3rd party lab (SGS) which verified the result.

You are correct in that we should have the TEG pH tested before being shipped out from manufacturer. We will request a pH test from manufacturer before shipping out for future purchases.

Our problem now is we will have about 300+ drums of TEG with pH of 8.4 which is not acceptable to client and I don't think the supplier would be willing to take back the stock.

The client accepts delivery in tote tanks in which we do decanting from the drums into the tanks using pumps. 

Is it possible to mix say 1/2 a tank of pH 8.4 TEG with 1/2 a tank of pH 6.8 TEG (from another TEG supplier) to get TEG of pH 7.6?

Would that be worth trying out?

[curiouscat]

Did you do a full assay of your TEG? Is there moisture / water in it?

The pH reading of 8.4 by client was correct as we just did a sample testing by a 3rd party lab (SGS) which verified the result.

Can you post the assay procedure used by the 3rd party lab?

[curiouscat]

Is there an additive? MEA / DEA etc? Did your supplier add too much of it?

[curiouscat]

Is it possible to mix say 1/2 a tank of pH 8.4 TEG with 1/2 a tank of pH 6.8 TEG (from another TEG supplier) to get TEG of pH 7.6?

I doubt it. pH isnt additive. It's a log scale. You might need a lot more of the 6.8 stuff.

Random thought: Try bubbling air / CO2 ( if you have access ) through a sample / drum for a while & test to see if pH reduces.

I'd say bubble for 24 hours with a sample every 2 hours. TEG isnt volatile so you may not lose any vapors. But checkl  the assay. Dont want it out of spec by too much oxidation.

[BobHawker]

Hi Curiouscat,

Thank you for your input and suggestions.

I've attached the 3rd party lab test results which shows all the parameters tested, appreciate any comments that you have.

Bubbling air or CO2 through the TEG sounds interesting, may I know what is the rational behind it?

Lastly, what pH tester do you recommend for TEG? Thanks again for your interest and help.

[BobHawker]

For your information, we source TEG from various overseas suppliers and looking back on the test reports from this year, the pH value for the TEG goes as low as 5.25 and we had no complaint from client there.

It seems that lower pH value TEG is acceptable to client as the pH will rise during the dehydration process perhaps.

[curiouscat]

I've attached the 3rd party lab test results which shows all the parameters tested, appreciate any comments that you have.

Thanks. Your assay looks pretty good to me. I'm not an expert on this though.

Bubbling air or CO2 through the TEG sounds interesting, may I know what is the rational behind it?

Sure. For one, TEG's acidity is known to increase slightly over time due to formation of acidic byproducts on air oxidation. That's why some facilities will blanket TEG tanks with N2.

Your TEG seems too alkaline so if there was some acid generation I was wondering if it might compensate. Just speculative.

CO2 OTOH would also directly work as an acidity booster.

Lastly, what pH tester do you recommend for TEG?

I don't have a specific model in mind. I think most of the commercial ones are good enough. The critical bit is not testing neat but only after a 1:1 water dilution.

Your third party lab seems to have adhered to that so all seems well.

[curiouscat]

For your information, we source TEG from various overseas suppliers and looking back on the test reports from this year, the pH value for the TEG goes as low as 5.25 and we had no complaint from client there.

It seems that lower pH value TEG is acceptable to client as the pH will rise during the dehydration process perhaps.

Well too acidid & equipment will corrode.

Too alkaline & foaming might happen.

That's why there's a range. How strict a client is at each end of the spec. depends on specifics of their process, equipment etc.

[Jov_El]

BobHawker, were you able to decrease the pH of your TEG? What method did you use? can you share?

I am having the same situation now and badly needed some help.

Thanks!

[BobHawker]

Jov El

It turned out that the high result was probably due to contaminant from the tote tanks that the TEG was decanted into. The tanks were owned by the client and apparently they use the tanks for other chemicals as well. It was agreed that there might have been residues in the tanks which caused the pH of our TEG to spike.

Happy to say our TEG was not rejected and matter was resolved without us having to modify pH of the TEG.

[ulj]

Hi Guys, on the same material, TEG of course. my clients observed the pH is out of range 5.2 instead of 6 min. any ideas on how can be increased? Thank you

[Davide Congiu]

Hi Uly. In TEG/DEG dehydration units Methyl-Diethanolamine (MDEA) is commonly used for pH control to keep pH value between 6 and 8