7 replies to this topic

Could you give some detail about the solid model (SSM) which base version of Prode Properties adopts for multiphase equilibria ?

The documentation says it is based on liquid fugacity less contribute of molar heat of fusion but I think it is a bit more complex,

also solids in  phase  equilibria seem to work better with a EOS as Peng Robinson or Soave Redlich Kwong,

is that true ?

[marchem]

Prode Properties has several models for solid fugacity,

with Simplified Solid Solution SSM model included in Base version

fugacity of solid phase is calculated from fugacity of liquid phase as

 

Fsolid = Fliquid * exp(CT*Hf/Tm - CT*(cpl-cps)-...)

 

where

Hf = heat of fusion

Tm = melting point

cpl = heat capacity of liquid phase

cps = heat capacity of solid phase

there are additional terms which provide some contributes

 

Generally I utilize the SSM (Simplified Solid Solution) model with hydrocarbons,

it's good to predict vapor-solid as for example solidification of CO2,

for liquid-solid I utilize SSM or other models. 

For hydrocarbons a EOS as Soave Redlich Kwong or Peng Robinson can provide good accuracy. 

[pdender]

thanks Marchem,

what is the role (in phase equilibria) of the solid vapor pressure available in databank ?

Does Prode Properties utilize those values ?

[PaoloPemi]

the SSM model included in Base version doesn't utilize that information,

as noted by marchem there are other models for solid fugacity

also you may extract the data from database (Prode allows direct access to all properties of pure fluids) and create your own model.

[pdender]

thanks PaoloPemi,

so, can I calculate solid formation for a pure fluid with the solid vapor pressure available in Prode Properties databank or with SSM  (or other solid models) available in the library ?

[PaoloPemi]

I am not sure to understand the question,

do you wish to utilize the coded flash operations in PRODE PROPERTIES (T-P, H-P, H-T etc.) with multiphase (vapor-liquid-solid) option

or create your own  procedure ?

By the way for pure fluids you can calculate solid formation with the solid vapor pressure available in Prode Properties databank,

that's not difficult since you have only to compare the solid condition with the pressure in your system.

[pdender]

thanks Paolo !

yes, I can define the state of a (pure) fluid comparing its solid and liquid vapor pressure.

[PaoloPemi]

also please note that you may need specific thermodynamics (as a electrolytic model) for some liquid-solid equilibria as salts formation.