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Hydrocarbons In Glycol Flash Tank


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#1 mahfam

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Posted 25 July 2011 - 05:43 PM

Hi,

What are the main reasons of seeing lots of Hydrocarbons in Glycol Flash Tank in Dehydration Projects?

Thanks,

#2 Technical Bard

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Posted 25 July 2011 - 10:07 PM

Hi,

What are the main reasons of seeing lots of Hydrocarbons in Glycol Flash Tank in Dehydration Projects?

Thanks,


The biggest reason this is probably happening is that the hydrocarbon dewpoint of the gas is higher than the glycol supply temperature. Easiest way to tell if this is true is whether the inlet gas (which is probably coming from a gas/liquid separator) is warmer than the lean glycol. Should be at least 10°C colder.


The second possible reason is if your gas contains significant aromatic species (BTEX), which are soluble in glycol. These however tend not to separate in the flash drum but are found in the still overhead vapours (which is bad from an environmental point of view).

#3 Erwin APRIANDI

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Posted 25 July 2011 - 10:14 PM

Very low temperature difference between the gas inlet temperature and gycol inlet temperature can cause condensation of Hydrocarbon in the contactor, which then sent over to the glycol flash drum. Or it may be becouse of carry over from the inlet gas.

Carry-over can be prevented by maintaining proper levels in the inlet separator and by keeping mist mats clean. Condensation in the contactor can be prevented by maintaining the inlet glycol temperature about 3 °C to 6 °C above the inlet gas temperature.

#4 mahfam

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Posted 25 July 2011 - 11:06 PM

Glycol temperature is almost 10'F higher than the inlet gas temperature, so condensation probably does not happen. I am not sure about the carryover in inlet gas, as the plant inlet flow rate has changed. Is it possible that the separator may nor be adequate for new flow?
If the gas contains significant aromatic species (BTEX), then what should I do to solve this problem?


Thanks,

#5 Vimalesh Agnihotri

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Posted 25 July 2011 - 11:57 PM

Dear Mahfam,
U need to check the outlet gas temperature from contactor. this should be lower than inlet glycol temperature to avoid hydrocarbon condensation in contactor bottom. hope this will solve your problem.

#6 Technical Bard

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Posted 26 July 2011 - 10:42 PM

Glycol temperature is almost 10'F higher than the inlet gas temperature, so condensation probably does not happen. I am not sure about the carryover in inlet gas, as the plant inlet flow rate has changed. Is it possible that the separator may nor be adequate for new flow?
If the gas contains significant aromatic species (BTEX), then what should I do to solve this problem?
Thanks,



I did work in a plant many years ago where carryover from an upstream separator was the cause of many problems in both amine and glycol systems. You should check the separator and potentially place a coalescing filter in the gas stream to capture any entrained droplets (if if appears the separator is undersized).


For BTEX, the solution is to either remove it from the gas upstream, remove it from the glycol via carbon bed (although this is expensive to operate), or incinerate the glycol regenerator vapour. You may also need to run the glycol regen hotter to ensure you strip the BTEX out. A company that has expertise in this field in Process Ecology in Canada (http://processecolog....php?r=services) (I do not work for them)







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