N-MDEA foaming

[231272]

Hello guys.
on our FCC unit, after TA we change MEA with N-MDEA. After that we notice foaming of N-MDEA. Some hydrocrabons are mixed with N-MDEA.
We drain N-MDEA, and we circulate with condensate in order to wash the system.
We try start up amine section, but we observe foaming.
Do you have some similar experience with foaming of N-MDEA solution? Do you have some advice ot tip how to solve this problem.
Thank you
R.

 

[Egbertvh]

Suppose that with N-MDEA you mean regular or non formulated MDEA.
MDEA has a higher solubility for hydrocarbons than MEA. This is caused by two things. Firstly due to the molecular stucture and secondly because MDEA is used at higher concentrations than MEA.
These things are often not told by chemical suppliers who only advertise the advantage.
One other item to remember is that MDEA also tends to have a higher corrosion tendency when HSAS are involved. HSAS are frequently found on FCC amine systems due to HCN in the gas.
Egbert van Hoorn
Amine Experts

 

[25362]

Normally up to 30% of the circulating amines should be filtered, some systems requiring 100% filtration.
Particle filtration and carbon adsorption remove not only contaminants before they react with the amine but also solids that can stabilize foam.

 

[231272]

Thank you for answers.
We use MDEA on HDS unit, and we do not have problems with foaming. 15 % of amine is filtered.
On FCC unit we don't have charchoal filter, and I realize that these can be one of problems.

I am surprised that MDEA is foaming when we mixed it with condensate (45 % soulution) - and without putting gas and any HC in it. Maybe system is not clean enough and we have some dirty or detergents rested after TA. MDEA is new.

Do you have some other tips.
Thank you again.
R.

 

[Egbertvh]

Fresh MDEA mixed with condensate should not foam.
Condensate sometimes has some chemicals in it.
It is most likely that the MDEA that you pulled out of the system for a sample was contaminated with some surfactants of the FCC MDEA system. It takes very little. 10-100 ppm detergent can be enough.
FCC amine systems are notorious for foaming and corrosion problems. Activated carbon rarely solves this problem.

Egbert