4 replies to this topic

[CHE Guy17]

I am separating a multicomponent stream of water and 2 hydrocarbons. I want to separate the stream to remove as much of hydrocarbon 'A' as possible. If water has a boiling point of 100degC, hydrocarbon 'B' has a boiling point of 104degC and the component I want has a boiling point of 34degC would the recommended course of action to preheat the inlet stream to say 60degC so that 'A' vapourises and on entering the vessel the water and 'B' will just be separated out by gravity while the vapour will be pulled out by a vacuum pump.

Any help would be greatly appreciated.

Thanks

[Arpit_Jain]

Use flash in the first step. 34degC boiling liquid will separate out in the liquid stream and the rest will go out as vapour.

Now if water is not miscible with remaining hydrocarbon, you can use a decanter after looking at the LLE (liq-liq equilibrium) data.

If miscible then you will need a distillation column as boiling point difference is very less

Dear Professionals,
Please correct if I am wrong.

Thanks

Regards
Arpit

[sheiko]

Use flash in the first step. 34degC boiling liquid will separate out in the liquid stream and the rest will go out as vapour.

I believe the lighest molecules (lowest boiling point temperature and highest vapor pressure), i.e. hydrocarbon 'A' (and few molecules of hydrocarbon 'B' and water), would vaporize first and leave the flash drum via the vapor outlet at the top. The remaining liquid mixture, composed of hydrocarbon 'B' and water (and few molecules of hydrocarbon 'A'), would flow through the liquid outlet at the bottom of the flash drum.

Edited by sheiko, 21 February 2012 - 05:50 PM.

[pavanayi]

<sup>CHE guy,
The boiling points you mentioned are pure component values. Which means, if there was only pure component A, all of it would vapourise at 34°C. What you have is a mixture of components. When you heat it to 60°C (or for any other temperature between the mixture's bubble and dew points), A will vapourise. So will some B and C. This depends on the VLE. (But as you would expect, it will be mostly A initially). What you need to decide first is how much separation you want to achieve.

Arpit,
As pointed out by Sheiko, component A will separate out in the vapour stream and the rest in liquid stream, not as you mentioned.</sup>

Edited by pavanayi, 22 February 2012 - 03:26 AM.

[Arpit_Jain]

Yeah Sorry my mistake,

hydrocarbon A will come out as vapours

Thanks for correcting