5 replies to this topic

[Sabrina Bsingh]

i am working on a girbotol unit and filter change outs are quite frequent. Rich amine from a visbreaking unit is sent to the unit for processing but when there are upsets on that unit, hydrocarbons is suspected to come over with the rich amine clogging up our filters requiring alot of change outs.Any suggestions on how to prevent this hydrocarbons from entering the unit and what are the implications on having heavy hydrocarbons in the amine system?

 

[Art Montemayor]

Sabrina:

 

You are never going to successfully operate an Amine Girbotol unit while hydrocarbons are contaminating your solution.  A lot of subsequent problems will essentially shut down the Girbotol regeneration equipment.

 

A visbreaker unit is usually composed of a fractionator and an optional vacuum fractionator.  No amines are normally employed in the visbreaker itself.  Please explain how your Rich amine originates in your visbreaker.  A detailed sketch will be an excellent means to tell us.

 

The famous, 87-year old Girbotol Process was developed by the Girdler Corporation as a means of removing acid gases (CO₂ and H₂S) from gaseous hydrocarbons using an ethanolamine in aqueous solution.  Perhaps you mean that the fractionator overheads gas and LPGs are being treated by a Girbotol unit with aqueous Amine solution.  If so, which amine is it?  Is it MEA or DEA?

 

Please supply our members with detailed and accurate basic data.

 

[Sabrina Bsingh]

hi sorry for not being clear, the sour gas from the VBU unit is sent to the absorber on that unit however if there is an upset sometimes there may be liquid hydrocarbon carryover into the absorber from the knock out drum. The rich amine would thus contain hydrocarbons which enters my Girbotol unit which regenerates the amine and send it back to the VBU. there is a lean amine filter which often clogs with black oil like substance whenever we send the lean amine to the VBU. I understand that this would cause a problem. any advice on what can be done to alleviate this problem and also would this contamination cause amine degradation?

 

DEA is used.

Edited by Sabrina Bsingh, 26 July 2017 - 09:12 AM.

[Bobby Strain]

You should improve the operation of the separator. And train your operators.

 

Bobby

[Sabrina Bsingh]

I cant train the operators that are not on the plant I am assigned to. Can anyone tell me the implications of having hydrocarbons in the system and what can be done at this point to prevent it from happening?

[Art Montemayor]

Sabrina:

 

What Bobby has stated is succinctly correct to the point in question.

 

We don’t know your job description, so he couldn’t know that you have no supervisory position in your plant.  But his basic advice holds:

It is imperative that NO hydrocarbons - especially liquid hydrocarbons - should enter the Diethanolamine regeneration system.  If this is occurring, as you have stated, the degree, frequency, and conditions under which this is happening should be controlled or, if not possible, should be reported in detail to some engineer who is responsible for the unit.

If this is a chronic or continuous occurrence, then the basic design, operation, or loading of the important knock out drum that is meant to protect the downstream DEA regeneration system is wrong or out of specification with the capacity and conditions under which it is supposed to operate.  This situation can't be allowed to continue and must be resolved.

 

I repeat: NO LIQUID HYDROCARBONS CAN BE ALLOWED TO ENTER THE RICH DEA SECTION.  Should that happen or continue to occur, the following will probably affect the operation and eventually shut it down:

• The DEA reboiler tube bundle will get coated, fouled, and encrusted with tarry or coked deposits on the shell side (especially if it is a direct-fired type) and reduce the capacity of the unit due to reduced heat transfer;
• The DEA solution will get contaminated and reduced in its sour gas absorption capacity, resulting in a reduced unit capacity that will progressively get worse as time continues;
• All equipment in contact with the DEA solution will get contaminated, fouled, and encrusted with hydrocarbon liquid or coked deposits.  This includes stripper trays or packing, solution heat exchangers and coolers, solution pumps and related piping and instruments.
• If you have a direct-fired reboiler, this situation could get very bad very quickly.  Encrusted or fouled reboiler tubes will reduce or halt the normal heat transfer and cause the tube bundle to get excessively hot and damaged due to an inability to release the heat into the rich DEA solution.  Depending on the instrument safeguards installed, this could get bad quickly.
• The answer to all this bad news is relatively simple:  obtain accurate and credible reports from the operators in order to confirm that the installed knock out drum is not adequate for the conditions it is handling.  The knock drum should be thoroughly inspected for defects and, if necessary, replaced with an adequate design that fulfills the basic design criteria of separating out all liquid hydrocarbons entrained in the sour gas.  You may not have any other choice if you want to continue operating an efficient and safe unit.

I hope I have made my point very clear: amine systems cannot operate in a contaminated manner and the correct design of a knock drum that ensures that no hydrocarbons present in the sour gas will enter the amine system is of utmost importance.  Your DEA solution should be circulating with a clear, yellowish color that resembles horse urine.  That has been my experience.  The clearer and purer you maintain your amine solution, the better and more efficient your unit will operate.  It's as simple as that.  The moment you start contaminating your solution is when you start to dig your own grave.