Antifoam dosage in Benfield Process

[JohnCalvin]

We have a Benfield process to remove CO2 from an LPG stream before it goes to a cryo unit. Currently we experience foaming problems and the dosage of antifoams is necessary. My question is two-fold: 1) is there an upper concentration limit above which it becomes simply ridiculous to dose any further antifoam and 2) what type of antifoams would be stable in a highly alkaline environment (pH 8 - 11) such as the Benfield process?

As a rule we have only made use of non-ionic surfactant antifoams in the process, but some of these components, e.g. fatty acids and polyglycol esters are definitely not stable in the given pH range and I have a concern with this.

Kind regards,

JohnCalvin@Geneva.com

 

[22082002]

Varoius NPRA sessions have dealt this question.
I am not sure whether it applies to 'benfeild' process, but all of the panelist recommended dosing not more than 6 ppm.

Regards,
SAA

 

[samy1234]

you can try silicon bases antifoam. normally antifoam PH is 7.0. we are using silicon based antifoam for co2 removal process.we use MEA for absorption.

 

[Montemayor]

JohnCalvin:

I have seen the foaming dilemma and been involved in a few also. I have the following comments:

1. Presumably, you hold an operating license on the Benfield Process. If, so, you must be following the dictates of Benfield regarding the addition of any substance (anti-foam or others) and are closely controlled and advised by them on the need to add ingredients to your solution. You should rely solely on Benfield to answer your queries or problems regarding the solution. If you resort to employing non-Benfield advice and solutions to your problem, you may forfeit your licensed warranty and performance expectations.

2. My experience with MEA tells me that there is a definite limit on the concentration of additives that you can use in an acid gas absorbing solution; my personal policy has been NO ADDITIVES, PERIOD. The more and more additives you put into your solution, the more the situation gets out of control. You quickly reach a point where you cannot identify the absorbing properties of your solution with accuracy. You wind up with a solution that can't be identified as to specific properties.

I would advise you to stick religiously with any instructions you receive from Benfield. Let's face it: you or the unit's owner accepted Benfield as the "experts" when you accepted and bought the unit and the license to operate it. Any Benfield warranties on performance will be nullified if you "tinker" or violate your agreement with them. Why would you risk it?

I hope this helps.


Art Montemayor
Spring, TX

 

[22082002]

Further to my earlier mail:

Foaming: has it gone up recently ? since you are asking how much more you can dose.
Instead of increasing antifoam, I suggest you check if iron-content has gone up or you have taken sidestream filters out of service for considerable time.

We operated the amine process with almost nil antifoam dosing. Highlights just for information:
-It was for H2S with MDEA
-The amine temp is recommended to be atleast 5°C more than process fluid temp. This is applicable for MEA also.This prevents HC condensation which leads to foaming, very important!

Just in case if you wish, you can read this paper:

http://www.bre.com/technicalpapers/technicalpaper.asp?articlenumber=45.

Regards,
Satish

 

[JohnCalvin]

Hello,

Thank you all for your answers - allow me to reply a little while. The original licensors of Benfield were Linde and they actually designed the process without antifoam usage. Be that as it may, UOP bought the process from them and when foaming was encountered, they recommended a polyethylene-polypropylene glycol surfactant from their corporation.

This is definitely stable in the given pH range, but indiscriminate dosing of it by ourselves has led to severe blockage problems. I agree that the best approach is no additives whatsoever, but the problem must be treated and at this stage only symptomatically. I do not know if we understand the true cause of it all. What I do know is that if 6 ppm is the antifoam limit, we have exceeded that more than a 1000 times!

Q.1 How can one distinguish between foam caused by physical operating parameters as opposed to that caused by chemical constituents?
Q.2 Where can I obtain information related to foaming and its causes, treatment etc.?

 

[22082002]

Hi,
I am giving these two links, first is eng-tips thread and other is from website. See if these help..

thread798-39310

http://www.huntsman.com/performance_chemicals/ShowPage.cfm?PageID=885

Regards,
SAA