6 replies to this topic

[mahfam]

Hi,

We had designed a Dehydration unit for 400 psig inlet pressure, and after construction it worked properly in this pressure. Now, they are having problems with the inlet gas pressure and cannot provide this pressure. The pressure has decreased to 330 psig. Outlet gas water content is fine; however, now they have some problems with the huge TEG circulation rate.

I checked the simulation and realized that with decreasing pressure; the inlet separator is not working properly anymore, meaning that it does not separate Hydrocarbons at all. Theoretically, all of these Hydrocarbons should get out of Contactor as the outlet gas, but in reality it does not happen. In unit, TEG absorbs lots of Hydrocarbons and Carry them to the Flash Tank. The Flash Tank hasn't been designed for this flow and condition and cannot separate HC from TEG. These phenomena cause foaming and other problems that are the reason of large TEG Make up.

On the other hand, the Separators inlet temperature is 85°F, and I'm afraid if I decrease that to less than 80°F (in order to separate HC in the separator), some emulsions will be formed between TEG & Hydrocarbons in the Contactor and the problem will remain.

Do you have any suggestions to solve this problem?

Thanks,

[shan]

Lower temperature will help your separator performance, because of slower gas velocity and heavier liquid droplet density. There will be no additional HC vapor condensing into your TEG because Gas/TEG Temperature Balance Heat Exchanger will reduce your Inlet Lean TEG temperature correspondingly.

If your separator is able to knock off all the liquid as expected, there will no HC liquid in the TEG contactor and no emulsion possibility of HC/TEG. Otherwise, you may consider installing a pre-filter to prevent liquid droplet entering TEG contactor.

[Erwin APRIANDI]

Hi mahfam,

First you have to check the adequacy of you inlet separator, to operate at new operating pressure and temperature. It may not be adequate to handle the same amount of gas, since lower pressure required bigger size of equipment due to lower density which means bigger volume for the same amount of mass.

One of the solution that you can used is to try to enhanced the separation in the inlet separator, this can be done by decreasing the operating temperature or to install a pre filter as per what has been suggested by shan.

But after that, you also have to check the adequacy of your contactor and other related equipment, to see how much that it can take by using the new operating condition.

Hope it help

[anjumaziz]

Separator insatlled at upstream of TEG contacting tower is not giving desired output. Inlet colascing filter should be there at downstream of separator for further tunning of inlet gas and lower down of higher hydrocarbon. What is the frequecny of carbon filter swicthover after this problem, TEG flash Tank temperature / pressure, and differential pressure across the TEG contacting tower?

[Alexsandres]

Mahfam,

Use antifoam. Your contactor will perform better. Since excessive foaming also enters the glycol flash tank and regeneration column, it will cause less performance of your regeneration.

We inject antifoam to contactor. Make sure proper mixing of antifoam to TEG.

[Propacket]

mahfam,


In order to increase capacity of the separator, the simplest solution is to replace your demister with a Specialty Demister. You can contact companies like ACS for the specialty demister. These specialty demisters can increase the separators capacity by 50%.

[Bobby Strain]

So, how did you come to the conclusion that the separator is not effectively working? And I am confused about the symtoms. I doubt that you are circulating much more glycol as you indicate; but experiencing loss and thefore having to makeup more. So you need to get a better handle on what is happening, then determine why. So far you have only presented your assessment of the root cause, but no evidence to support same. That makes it difficult to get long-distance help.
Bobby

Edited by Bobby Strain, 08 August 2012 - 01:17 PM.