Foaming in BASF AMDEA CO2 removal system 3

[Razif]

Dear all,

I was wondering if anyone has experienced similar trouble with foaming in their CO2 removal unit. We are having to add a substantial amount of antifoam every shift to combat the problem. We have opted to install an activated carbon sidestream filter to remove hydrocarbons from system, which we believe is the culprit. However, I cannot pinpoint a source. Someone suggested that AMDEA itself can be the source of hydrocarbons. Any comments/suggestions?

Additional info: Operations wise, the solution circulation rate is only slightly higher than optimum. There was no damage to the packing and other internals of the columns as observed during the last turn around.

 

[TBARBill]

Are your temperatures around the contactor stable? Winter can bring cooler ambients and resulting hydrocarbon fallout in piping between separator/scrubbers and contactors. Lower ambients can also cause trouble in solvent feed temps to the contactor, resulting in increased HC condensation in treating a rich gas stream.

Was your system designed for aMDEA or was it converted? How much experience with aMDEA do you have at this site? I am not experienced wth BASFs aMDEA (they are trying to get us to try it) but are having seasonal problems with HC in our MDEA system (and we're not even in Canada!).

 

[Razif]

Thanks for your prompt reply, TBARBill.

To answer your first question, the ambient temperature is fairly constant at about 30°C, being a tropical country (Malaysia). It might get only slightly cooler in the night and during the monsoon seasons, but not by a whole lot.

Our plant has only been running for about 2 years, so its pretty new and yes, the system was in fact designed for aMDEA from the start. On the whole the system works satisfactorily.

Do let me know if you think of anything else. Thanks.

 

[44715]

Dear Razif

In all ammonia plants designed by HTAS wherein the aMDEA process is used for CO2 removal, a sidestream filter of activated carbon system is proposed by the licensor and the anti foam injection is done.

as you are in malaysia may be get in touch with someone in fertilizer plant to know the operational problems

GB

 

[TBARBill]

A carbon filter on a portion of the rich amine stream is usually the best way to deal with foaming problems. Antifoams work well, but are expensive. They also violate the "if some is good, more is better" rule, so small amounts are the best way to go. It sounds like you're doing the right things.

 

[ammonia88]

Dear Razif,
The following things may be interesting although the use of Actvated carbon sounds pretty well.
1. What I understand the antifoam solution itself gets degraded after doing its job.This can also cause foaming.
2. Some of the tower packings must have got displaced from original places.
3. Trays codition must be checked as there is exess AMDEA circulation in the system.
Please do the LRD test of trays during TA/Shut Down.
4.CO2 in the Inlet Gas to absorber seems to be more than the design.
5. Consequences of MDEA carry over may be investigated. Effect on trays,packings and downstream equipments may be thoroughly checked.
Satyajit

 

[151270]

Dear Razif,

We had earlier facecd similar problem of foaming in CO2 absorber of our Hot potassium carbonate system.Our main observations on this are :
1) Too much of anti-foam agent makes soultion prone to foaming due to its degradation into organic compounds at stripper reboiler tube skin temperatures.
2) Degarded products can be removed by installing side stream filter of mechanical type with SS wire mesh. We have two such filters and had to clean filter every week during period we faced this problem.Pressure drop build-up was due to accumulation of sticky antifoam on filter.
3) From other reports, small broken particles of activated carbon remainsuspended in solution and can cause foaming.
4) We have SS pall ring packing in absorber and ceramic packing in stripper.During turnaround, we cleaned the pall rings first time since their installation in 1984.We found that a sizable quantity of packing had agglomerated into lumps which had to be broken.After cleaning, the pressure drop has become much more steady and antifoam is being added only ocassionly.
5) Foaming can also be due to operation near flooding point and uneven distribution of solution at top.I assume you have checked these.

Hope this is of help.
Ashwani Kaul

 

[spekuljak]

We revamped a Removal unit in ammonia plant, wich had severe foam trouble (it was impossible to operate it without antifoam injection). The original column was filled with random ceramic ring, and was revamped with structured packing and proprietary auxiliaries, specific for structured packing. The result were very satisfactory (no more foam). The key in amines system equipment is avoid the bubbling, so the generation of foam is strongly reduced, i.e., a submerged sparger is strongly not-recommended.

 

[mrmethane]

temperatures are critical with this type of amine,
first make sure you heat your inlet gas with amine,not cool it with amine, secondly the carbon filters will help but anti-foam kills charcoal filters.
too high of a flow rate over the top of a poorly designed contactor will cause this, as will too little flow.
We have a contactor that is over-sized by about 4 fold, and is only insulated on the bottom five feet, right now it is 30 degrees f. ambient, and the bottom temp of our contactor is only 75 degrees f., our inlet gas temp is 85 degrees f. to contactor, our lean amine is 125 degrees f into the contactor and I am running 38.2 gpm flow with 70mmscfd of 305 ppm c02 and 7.70 ppm h2s , sweetened gas has 14ppm co2 and no h2s, going through a cryo with nru final temps in the cold box are -305.00 f. with no c02 freeze ups, and we can start back up in 2 hours after we shut down, no dry out time due to c02, one other plant down the road shuts down once a year to dry out it takes them 3 days and an expensive nitrogen bill, not to mention down time! mr.methane

 

[rosch]

Dear Razif,
we have experience over 6 years similar trouble with foaming in our CO2 removal unit. The plant was design and built whith activated carbon sidestream filter but still have foaming.
Be ware that too much of anti-foam agent makes soultion prone to foaming also injection too fast get the same problem.
Still we didn't solve the problem.

Do you have also corrosion on the system ?

 

[kjaishankar123]

In the first place how do you confirm that there is foaming? the primary cause for foaming can be dirt in the system or oil. normally when plants are commissioned it is essential that ss packings are degreased but in your case i am not sure if this is done.

 

[Kaz2003]

Rafiz,
We run an MDEA and we have experienced foaming problems in a manner that we need to continously inject antifoam. However, we have investigated the problem and we're implementing modifications that we hope will eliminate the foaming causes.
1-Have you checked the residence time in the flash drum? Reduced residence time keeps a residual amount of hydrocarbons in the amine which can cause foaming.
2-Carbon filtration can only be effective with traces of dissolved HC in the amine and carbon beds performance is highly restricted by absorption of antifoam. Also mechanical filtration upstream and downstream of carbon beds is highly recommended to prevent contamination of amine by carbon dust wich can cause foaming.
3-Heat stable salts produced by amine degradation due to high temepature and oxygen ingress into the amine can cause foaming so frequent monitoring of these species is required and this may show that amine reclaiming is necessary.
4-Adequate Mechanical filtration of the full flow will reduce foaming.
5-We keep a temperature difference of 5-8°C between inlet gas and inlet amine to the contactor which is necessary to prevent the cooling of the gas and condensation of HC in the contactor.
6-EFFECIENT Inlet liquids seperation is very determining in preventing liquid HC pick up by the amine which could not removed by the carbon filtration and would cause foaming.


Regards

 

[mala6217]

dear razif,
in our aMDEA system, we generally add antifoam on continuous basis. in our plant,
- too much antifoam dosing causes foaming in system, it normally happens when concentrated soln. is made before dosing.
- norally after every plant start up, we experience foaming. we suspect that all the scale/dirt/foreign particles are dislodged from packing. we simply wait for a day, and keep on cleaning the sidestream filter.
- do u add solid pipprazine chips to increase its concentration? it normally promotes the degradation of solution, hence causes foaming in the system.it is advisable,not to use solid pipprazine chips.
- do u found scale on the plate type soln. heat exchangers, what do u do? do u face load limitations?
- what is the level of suspended solids (SS) in your system?
- in our system, SS are mainly silicone derivatives.
regards

 

[Volker]

Dear Mr. Razif,

To answer your questions in general, the following conditions could cause foaming:
1) Oil, fat, grease from insufficiently cleaned vessels or column packing
2) Heavy hydrocarbon or long chained organic acids entering with the feed
3) Dust from low temperature shift catalyst
4) Particles like dust, charcoal, etc
5) Contaminants in make-up water

 

[muruga2003]

one of the possible sources causing foaming is Activated carbon carryover. A properly installed post filter ( d/s of carbon filter) can avoid this problem. The bottom of the carbon filter bed may be stacked with 1/4 " alumina balls and then charge carbon to avoid particle slip. Degraded organics can also be the cause.The carbon filter when kept in circulation can remove the degraded organics.

 

[JSantos]

Mr Razif:
I spent 8 yrs in R&D, Technical Service and Latin American Business Development for GAS/SPEC (Dow MDEA) before it went to INEOS. As a researcher/tech service for Nat Gas, Ammonia, HYCO, IGCC=Power, and Refinery scrubbing units, I concluded that there were/are basically three types of anti-foams: silicone-based (polydimethylsiloxane- PDMS), polyglycols, and polyols (long-chain alcohols). I found that silicone anti-foams can be "overdosed" and cause foaming (as other replies to your posting indicated). The polyglycols seemed to work better and were less prone to the overdosage effect. Finally, the long-chain alcohols were sometimes effective, but generally needed to be continuously injected (100 ppm level). I had developed no data showing that polyglycols nor alcohols caused their own foaming problems. If you have to add anti-foam, then a combination of polyglycol and silica worked the best. Two liquid with different surface tensions will stablize the foam and cause a problem. HC, carbon filter fines and too much antifoam are culprits. "Absolute" filters: 1-5 micron will capture the antifoam from your system.
Hope my comments are useful.

JSantos

 

[RogerH]

Dear Razif, much have been written and Volker summarizes the sources quite effectively.
I would just like to add that to find the source can perhaps be done by monitor the foam height and stability at variuos locations in the plant which might help you to pinpoint the source. e.g. particle measurements can be done with the help of filter manufacturers, they normally gladly help doing this special analysis when they have a chance to sell a filter.
I have seen a variaty of different design but the best I have seen so far (and operated) is the one that TPA done, that is 100 % rich amine mech. filtering and 30-50% Carbon + after-mech. filtering. This one performed very well (no foaming upsets)and very low make-up. The other have not been that good. The backside is as usual invetment cost.