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Please help keep it that way by submitting your questions.
(disclaimer: D-Foam, Inc. is not responsible for the accuracy of the questions or answers listed on this page)
Question - What is the difference between froth and foam?
Answer - Stability or break time. Foam that breaks fast enough not to create a hydraulic restriction in the column is invisible to
operating instruments. Each tower, in fact, each tray in a tower has its own unique sensitivity to froth break time.
Question - How can water white (clean) amine foam like crazy, and dirtier amine not foam at all?
Answer - The contaminants you can see in an amine sample do not cause foaming. It's the invisible, soluble surfactants that form
stable bubbles. In fact, most of the visible contaminants amplify the formation of stable foam up to a certain "critical" concentration,
then inhibit foaming if the concentration increases. The reverse is true with some visible contaminants. Operating conditions are
also responsible for changes in amine foaming tendencies. Lower temperatures and higher solution viscosities increase the
solution's tendency to foam.
Question - What is the difference between silicone and alcohol based antifoam?
Answer - A detailed answer can be found in our 2005 technical paper, Antifoam What is it?, in the library section. The differences
are not the most important aspect of these two different classes of antifoam.
Question - How does antifoam work? Why does it seem to stop working, sometimes, and more need to be added ?
Answer - A good, fundamental review of the most common antifoams used in sulfur recovery processes is given in our publication,
Antifoam What Is It?, in the library section. Antifoams (AFAs) work by incorporating themselves into the foam bubble's cell wall
(lamellae), thereby creating weak spots. A diagram and pictures are given in the publication. Antifoam exhaustion is normally
attributed to silicone based AFAs which are comprised of two primary components; solid silica particles in a polysiloxane oil (liquid)
carrier. If the two components separate for any reason; settling, or multiple foamings, it doesn't work as well. The insoluble oil
fraction continues to act as an AFA, but with lower efficiency. Alcohol based AFAs do not experience this separation problem
because they lack a solid phase component. With all of that said, the principle reason most antifoams appear to exhaust is their
removal by mechanical filters and/or activated carbon, or inactivation due to being tied up with suspended solids. When AFAs and
solids get together, they form agglomerates that dramatically reduce the antifoam's activity. (see the pictures on our Lab Testing and
Samples pages.) The best way we have found to investigate antifoam activity (or lack thereof) is to test the actual foaming tendency
of the solution, and then have a look at it under the microscope. If the antifoam is present, or agglomerated, we can see it (and take
its picture for you).
Question - Can string wound filters cause foaming?
Answer - No, and Yes. The widely believed urban legend that oil left on the fibers of cotton filters can cause foaming is only partially
true. Any oil that contains a fraction that is soluble in amines can cause foaming if that soluble fraction acts as a surfactant
(detergent). In the cases we've seen where the filters appeared to be responsible for foaming the root causes were always soluble
contaminants. The filters looked like the culprits, but were actually helping the foam form indirectly by removing the antifoam, either
by itself or as a sticky antifoam-solids agglomerate. Activated carbon beds can do the same thing.
Question - Do formulated amine solutions foam more frequently than non-formulated?
Answer - No. However, formulated amines are normally used at higher solution strengths than non-formulated. If the more
concentrated solution has a higher viscosity, its foaming tendency can be increased.
Question - Are there any conferences or workshops that offer more information about operational problems in amine plants?
Answer - YES! We are happy to report that the Laurance Reid Gas Conditioning Conference (Oklahoma University) offers the best
"grass roots" operations based technical conference we've ever attended.....anywhere! One of the favorite aspects of the conference
is the Round Table discussion at end of the 3 day conference where literally any question is addressed by hundreds of engineers
and design specialists from all over the world! We can't say enough about their program, check out their website linked above.
Question - Can filters and activated carbon eliminate my amine foaming problems?
Answer - No, but they help so keep them on-line and maintained! Mechanical filters remove suspended solids that stabilize froth
that would normally not cause foaming symptoms, and dramatically amplify erosion corrosion in process piping and equipment.
Activated carbon, if properly maintained, can adsorb most of the dissolved surfactants that ultimately cause amine foaming. Some
of the properties of activated carbon make it unreliable in amine processes. A good review of the advantages and disadvantages,
as well as engineering data, is given in our publication Activated Carbon in Amines .
Question - How much free liquid hydrocarbon does it take to cause an amine solution to foam?
Answer - This is a trick question. One of the most common misconceptions (urban legends) handed down through almost 100
years of sweetening hydrocarbon gases and liquids with amine solutions is that free liquid hydrocarbon actually causes amine
foaming. That's right, liquid hydrocarbon does NOT cause amine foaming. In fact, settleable liquid hydrocarbon acts like antifoam
(see Hydrocarbon Effects on Foaming). Most antifoams used in this industry are either mixtures of silica solids and silicone based
oils, or large molecular weight alcohols (oils) which are also insoluble in amine (see Antifoam). If the contaminating liquid
hydrocarbon has an amine soluble fraction that can act as a detergent (surfactant), it may cause solution foaming (see Foaming
Abatement 02, Myth Busting 06). There is also significant evidence that suggests these soluble hydrocarbon fractions inhibit gas to
liquid mass transfer which would directly affect the amine's ability to remove acid gas (see The Effect of Hydrocarbon 02).
Question - How does the SigmaPure system work?
Answer - The system creates foam, separates it from the bulk solution, allows it to drain, and separates the gas and liquid
fractions. The gas fractions are recycled to make more foam while the liquid fraction (waste) is recycled to break the constantly
developing foam. See ( SigmaPure Treating and Troubleshooting )
Question - Antifoam has to be easier and certainly cheaper than using SigmaPure, right?
Answer - WRONG! This illustrates a huge misconception surrounding the use of antifoam. Antifoam temporarily covers up the
effects of foam causing contaminants. They are still in the solution, invisible, and concentrating! SigmaPure removes foaming
contaminants so they can't cause the plant to upset. A similar question would be, "An adhesive bandage has to be easier and
certainly cheaper than penicillin, right?" Postponing a problem only makes it worse. Is SigmaPure cheaper and easier than
working with the state and federal environmental agencies, and their fines, when the plant has exceedences due to foaming
upsets? Absolutely no question about it!
Question - How much foaming gas does it use?
Answer - The SigmaPure System can use any non-oxidizing gas to create foam. The two gases of choice are nitrogen or fuel gas.
The initial charge of foaming gas provides SigmaPure system operating pressure, as well as mass transfer area for surfactant
adsorption. The foaming gas is constantly being recycled during treating, so very little actual gas volume is lost.
Question - Does the SigmaPure system use any filters or activated carbon that need to be changed on a routine basis?
Answer - NO! It doesn't require any additives or backwash materials either.
Question - How long does it take for the SigmaPure skid to make our foaming stop?
Answer - The plant's response time to D-Foaming treatment will depend on: the rate at which the surfactant concentration is
reduced, (generation/ingress versus contaminant removal rates), and any amplifying or inhibiting contaminants in the solution,i.e.,
solids, antifoam, liquid hydrocarbon. In a typical application where the surfactants causing the foaming were generated over a long
period of time with antifoam being added to keep the plant under control, the plant would be expected to respond within 6-12 hours.
Keep in mind that "response" means a reduction in foaming symptoms, not complete elimination. Normally, plant operations
requires antifoam injections on an "as needed" basis during treating. Antifoam masks the affects of foam causing surfactants so
their removal is inhibited every time an injection is made.
Question - How long will a D-Foaming treatment last?
Answer - The answer is extremely plant dependent. Some of the plants we've treated haven't required another treatment for 3 years.
On the other hand, some have started foaming again hours after taking the Sigma Pure System off line. Contamination rate and
the condition of the plant's process column internals dictate how long the treatment lasts.
Question - How much waste does this thing generate, and what do we do with it after it is generated?
Answer - The volume of waste generated will vary with the volume of solution treated, the surfactants present, and the density of the
foam produced by the SigmaPure System during treating. A general rule of thumb for waste generation would be less than 300
ppm treated (<300 gallons from 1MM gallons treated). The waste disposal method is of course up the plant, but normally it is
considered "waste amine", and is disposed of accordingly.