[Dzoni]

Hi there,

I've got a Mass Transfer Operations assignment, and one part is basically absorbing benzene from flue gases in an absorption tower using a wash oil. Nothing difficult. However, I need the molecular weight of the wash oil in order to calculate the molar flow rates to be able to do a mass balance. I believe our lecturer wants us to go and find out what possible wash oil(s) can be used.

I've done a search on Google, which linked to a practice question from some or other university where they used 260 g/mol as the molecular weight of the wash oil. However, it didn't state what the wash oil is, and I am very apprehensive of using their given value. I've also looked through Perry's "Gas-Liquid Operations" section, and all I found was a mention of wash oils being commonly used for absorption of light hydrocarbons, but no specifics.

Can anyone tell me what wash oil(s) can be used, or at least point me in the right direction?

Thanks!

P.S.: What happened to all the resource searches that used to be on this site, on the left?

[eugenedakin]

Hello Dzoni,

Although I have not personally performed this test, my best guess would be using a longer chain hydrocarbon (with cyclic rings - based on the philosophy that like-dissolves-like), that diesel, paraffinic, asphaltenic and heavy-aromatic-naphthalenes would act as a good solvent to maximize benzene uptake.

Light aromatics or gasoline (petrol) would work, but may have problems when regenerating the solvent (by a thermal method).

I hope this helps,

Sincerely,

Eugene

[Dzoni]

Thanks for the speedy reply, Eugene!

Do you (or anyone else) know of a specific solvent, though? You see, while I agree with what you say completely, I believe our lecturer wants us to find out what the "industry standard" is, if there is such a thing for this application. Is there any literature I should look for in the library?

Thanks

[Dzoni]

I do think it's some kind of petroleum distillate, maybe cycloparaffin? But which one???

[eugenedakin]

Hello Dzoni,

Unfortunately, I do not know of any 'industrial standard'.  In the oilfield, industry standard is a highly relative term.  What is acceptable in the North Sea may not work efficient enough (with the appropriate capital costs) for Canada.  What may work in Canada may not meet environmental standards for a different part of the world. 

According to the Merck Index, benzene is miscible  with alcohol, chloroform, ether, carbon disulphide, carbon tetrachloride, glacial acetic acid, acetone and oils.  You have many possible chemicals to choose from, and also the miscible solvent HIGHLY depends on your benzene capture process (efficiency, contact time, etc.) and also depends on the method in which you are going to reclaim benzene from regenerating your chemical (heat, separation, etc.). 

First, decide upon a chemical, then select your process.  If your process doesnt work, then try to design the process then select the chemical.

I hope this helps!

Sincerely,

Eugene

[Dzoni]

Thanks once again, Eugene! 

[eugenedakin]

Hello Dzoni,

Your welcome... I just hope that you are able to reach an answer.

Sincerely,

Eugene