Chil:
I’ve had what is considered ample experience in the design, modifications, startups, and operations of TEG natural gas dehydrating units. I’m presently evaluating one such large unit.
What you describe in your original post can be addressed and resolved very simply. Allow me to address each of your concerns in that first posting:
1. I am needing some information about removing entrained hydrocarbons from glycol used in the dehydration of a natural gas stream. My research has failed to produce answers.
The resolution to entrained hydrocarbons entering the TEG Contactor (and the rest of the regeneration unit) is simple: entrainment of hydrocarbons is NOT ALLOWED and should be arrested prior to entering the contactor. This is normally done with a properly designed 2 phase separator. You cannot allow the hydrocarbons to enter the TEG system for obvious reasons that you are now experiencing. Why you have allowed this to happen is a good question. The reason you can’t find any information on how to combat and remove them AFTER you’ve allowed contamination is simple: sucessful operators don’t allow this to happen. In those cases where you might get some contamination and/or slugs, you should have skimming capabilities within your TEG Flash Vessel – which is upstream of the TEG Stripper/Reboiler. How to design this Flash Vessel is described in the GPSA Engineering Databook – which I presume you have a copy of. If you don’t have a copy, you should buy one and study it diligently.
2. Will filtration and activated carbon remove the hydrocarbons and surfactants?
The Activated Carbon Adsorber and the Sock Filter are items that are there to remove trace quantities of impurities in the circulated TEG. These will not have the capability of removing the quantities that you describe. Where does the “surfactants” come from and how do they appear in the TEG? I have always succeeded in running trouble-free TEG units and one of the main reasons for that is that I never, never add anything other than TEG to my circulating absorbent. When you add inhibitors and/or other little tidbits of other chemicals to the TEG you are asking for trouble – and you usually get it right away, BIG time.
3. What about inadvertently lowering the PH with the carbon?
What about it? If you are saying that the Activated Carbon lowers the pH of the TEG, then you are absolutely wrong. You definitely don’t want to run a low pH TEG within the system. This will start and propagate corrosion problems. One way to fight this is to use the Activated Carbon adsorbers to remove the acidic compounds formed (usually by oxygen in the system). Once the pH is lowered, then you are almost forced to add Borax (or something similar) to the TEG and break my “golden rule” of never adding anything else to the TEG. This is a bad operating situation that you want to avoid and you certainly don’t need.
4. Or is some type of distillation devise needed to remove the hydrocarbons?
No. The removal of significant liquid hydrocarbons is done by the skimmer compartment within the TEG Flash Vessel. You mention “dirty” gas, but you don’t quantify or qualify the “dirt” in the gas. Nor do you explain how and where the gas got “dirty”. That is the place to start in resolving your operating problems. Attack and eliminate the SOURCE of the problem – not the effects of the problem.
Additionally, some of the information and ideas you are now throwing out simply do not make good sense. You should know that the temperature of the Lean TEG entering the contactor should be approximately 10 oF higher than the gas entering the same contactor. This is to avoid condensing some of the heavier hydrocarbons in the contactor. Your idea on the cathodic protection is another similar idea that probably won’t work. You are, once again, avoiding to attack and eliminate the SOURCE of the problem and only attacking the effects.
You also are asking about salt contamination. Do you, or do you not have salt contamination. If you do, then you should apply the universal engineering “K.I.S.S.” rule: attack and eliminate the source of the problem. Otherwise you are in for some very bad and costly engineering experiences that won’t look very good in your resume.
Some excellent sources of information and data on the design and operation of TEG units that I recommend is found in the GPSA Engineering Databook, John Campbell’s excellent series on Hydrocarbon processing, and in the papers published by the Laurance Reid Gas Conditioning Conferences at the University of Oklahoma. These should all be required reading for anyone related to designing or operating a natural gas dehydration unit. You can obtain the Laurance Reid GCC papers in CD format.
Contrary to what technologist is advising you (“With TEG you have to face many problems”), there are NO extraordinary problems involved in operating a TEG dehydration unit. Hell, there are probably tens of thousands presently drying natural gas out in the world today. Most of these units are in totally remote and harsh “Oil Patch” locations and receive little or no attention. There is a BIG difference between producing TEG and operating successful and effective field TEG dehydration units. Compared with most other processes, TEG operations are a piece of cake – if designed and maintained properly. That is well-known engineering fact and not just theory or conjecture.
Basically, your problems (as you describe them) are the result of BAD HOUSEKEEPING. Clean up your act (& your gas) and you will eliminate practically all your headaches.
I hope this experience helps out.
ChemBuddy | 
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Topic: triethylene glycol (Read 23142 times)