[Scilab-users] Flash distilaiton

[jasper van baten]

This sounds like a flash calculation more than a distillation 
calculation and is directly performed by thermodynamic servers made 
available via CAPE-OPEN.

Implementing such an algorithm in a stable and efficient manner from 
scratch is not straight forward and has been the subject of many 
publications in literature. If you are restricted to two phases (vapor 
and liquid) and you are sure to be between the dew and the bubble point 
(so that you are sure that both exist) it becomes a lot easier. There 
are literally dozens of algorithms that do this.

Phase equilibrium conditions at specified T and P are such that

- all fugacities of all compounds in the two phases are equal
- the vapor compositions add up to unity
- the liquid compositions add up to unity
- the amount of any compounds in the vapor added to the amount of the 
same compound in the liquid must equal the overall amount of the 
compound (compound balances, aka phase summation equation)

You can use simply a Rachford-Rice approach 
(https://en.wikipedia.org/wiki/Flash_evaporation), or the approach 
sketched by Michael Michelsen, "The isothermal flash problem, part II, 
phase split calculation" (Fluid Phase Equilibria 9 (1982), pp 21-40). If 
you are sure you need to track over a constant temperature line between 
a dew point and bubble point, a continuation method comes to mind.

But you will still need to have the (log) fugacity coefficients of all 
compounds for the vapor and the liquid phase.

Best wishes,

Jasper.


On 8/1/2013 09:51, Dang, Christophe wrote:
> Hello,
>   
> the following message was sent to me, so I post it back on the list so it can find the right audience.
>
> Regards
>
> %%%%%%%%%% Original message %%%%%%%%%%
>
> The variation of flash vapor/liquid composition for various temperatures chosen between the dew point and bubble point temperature of the liquid feed.
>
>   
> -----Original Message-----
> From: "Dang, Christophe" <Christophe.Dang at sidel.com>
> Date: Wed, 31 Jul 2013 18:06:43
> To: sandy_eze at yahoo.com<sandy_eze at yahoo.com>; International users mailing list for Scilab.<users at lists.scilab.org>
> Subject: RE: [Scilab-users] (no subject)
>
> Hello,
>
>> De la part de Eze-Okoli Ifeoma Sandra
>> Envoyé : mardi 30 juillet 2013 17:36
>>
>> Good day, i would like to know how to design a multi-component flash
>> distillation system using scilab
> This seems to be a physical/chemical engineering problem.
>
> Scilab performs calculations, but you decide which calculations.
>
> So, first decide what you have to calculate and how, and then we might be able to help you.
>
> Best regards
>
> --
> Christophe Dang Ngoc Chan
> Mechanical calculation engineer
>
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