Dehy hydrocarbons

[Bopper09]

First off, it's my first post and I'm actually operating an oil / gas plant. But do have 4th class boiler ticket and a 2 yr petroleum Sait course. Hope I'm not too stupid to be on here.

I'm just wondering if anyone on here has any experience with a 90% gas stream through their dehy's. Since day 1 we've had hydrocarbon problems in our glycol, to the point where we actually physically skim the surge drums into a bin, consistently, even after 5 yrs of running. Our situation is recycling CO2 with 2 centrif compressors, obviously needing 2 dehy's before these that dry the aprox. 200 million of produced gas. We run through 2 inlet separators, then added 2 cyclone separators after that before the dehy's. We still have hydrocarbon problems in the glycol. We still skim the surge tanks, and actually have the surge tanks pressure up once in a while, from oil build up.

I guess there's quite a bit more info to give, but any suggestions would be helpful. We're told nothing is undersized.

Thanks

 

[zdas04]

90% gas, what is the other 10%? Liquids are a problem in a glycol contactor. Or do you mean 90% methane, 10% CO2 and other stuff? Most of the time when I see hydrocarbon liquids in a reboiler it is because the pressure drop moved some of the gases into the liquid part of their phase diagram. Usually this isn't a problem because the glycol out of the reboiler is hot enough to prevent condensation, but not always.

One thing to keep in mind, all the mechanical separators you'll every put in will have zero effect on components in the gaseous state. So if you have C5 in your inlet stream and the conditions stay right for it to be a gas you will have C5 in your outlet stream.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[Bopper09]

Oops I meant to put CO2 percentage, it's actually 87% CO2, with 1% H2S, and about 4% methane, 2% propane, and 2% butane is the main stream, the rest being C4 to C8. Our inlet separators / cyclones seem to dump about 10 barrels of liquid off a day, guessing from how much they dump. Couple questions I have would be if we don't flash enough off the flash drum? Our contactor inlet press is 190psi and flash drum is around 50psi, which we can't lower. Another thing is that I think we may overtreat in the field with a lot of xylene wash's, corrosion inhibitors which may get entrained in the gas stream? Even though our gas analysis doesn't show anything like that. Our reboilers keep close to 400F (200C) and the still's seem fine. We just can't get rid of oil in our glycol, and seems like there's nothing we can do about it.

 

[Bopper09]

We've got a gas analysis off one of our still columns, 12.4% C5 insoluble asphaltene's and 3.24% wax content. I guess that would explain the surge tank pressuring up, not carrying over with the waste gas to the incinerator?

http://www.oilfieldoperations.com

 

[SNORGY]

What is happening in the filtration that exists presumably between the rich gas / glycol flash drum and the regenerator?

 

[Bopper09]

We commonly go through a set of glycol filters every 1-2 days, yes rich glycol between the flash drum and reboiler

http://www.oilfieldoperations.com

 

[tobyman]

tobyman: Make sure your Glocol circulation rate is as per design, and that the Regeneration Temp is 204 deg. Check your Glycol PH it should be near neautral, if acidic u aint doing it correct a negative ph will cause corrosion