4 replies to this topic

[MikeM1]

Hi All,

I am looking into vacuum distillation as a method to purify amine that has a build up of HSS and amine degradation products. I am having troubles finding information on column specifications (ie. column diameters, # of trays, column height).

Can anyone point me in the right direction?

[Art Montemayor]

Mike:

You have to be SPECIFIC in your basic data. Some amines simply can't be "regenerated" via distillation - such as diethanolamine and triethanolamine. Are you referring to a Monoethanolamine recovery unit that uses semicontinuous steam distillation?

Amine (MEA) recovery is covered in detail in Kohl & Riesenfeld's classic book, "Gas Purification.

What column specifications are you referring to? Do you mean you intend to use a distillation column for distilling MEA? You don't recover MEA with a column; you simply use a very basic, small still with no trays or column.

[MikeM1]

Thanks for the reply Art.

I am looking at using DEA. I am aware that DEA can not be distilled at atmospheric pressure. DEA begins to degrades at 205°C, while its normal boiling point is 270°C. Under vacuum pressures the boiling point of DEA can be reduced to ~160°C.

I am intending on designing a vacuum distillation column to remove the HSS and amine degradation products. The DEA (and water) will vaporize in the column and the contaminants (HSS and degradation products) will be left in the bottoms.

I was hoping someone knew of of a source that explains how I can design a column for this purpose, or whether it is just a small still.

[Art Montemayor]

Mike:

I highly encourage and recommend that you be more specific in your engineering studies and exercises. You will avoid a lot of silly and un-needed errors and mis-conceptions.

The DEA (diethanolamine) you are referring to is employed in the selective removal of H2S and CO2, but IN A WATER SOLUTION OF 20 TO 25% WT. Therefore, when you try to recover (or "reclaim") the contaminated and degraded portion of the solution, you have to deal with a WATER SOLUTION - not the pure, undiluted compound. You correctly state that " DEA begins to degrades at 205°C, while its normal boiling point is 270°C". But that is PURE DEA, and you are dealing with a water solution!

Therefore, you have to consider and accept the fact that you are going to have to obtain an equilibrium diagram for the DEA solution to find out what will be the boiling point and the concentration of the overheads vapor.

There is a lot of information on the subject on the Internet. Just Google and spend some time researching it. I picked up the attached paper within 10 minutes. You should put in some of your own time into this effort if you intend to go forward with your project.

Good luck.

Attached Files

•  Amine Degradation & Reclaiming.pdf   156.73KB   87 downloads

[MikeM1]

Thanks Art.