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.