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Flash Point For Liquid Mixtures With Prode

flash point liquids prode

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#1 pdender

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Posted 14 March 2015 - 08:53 AM

how does the procedure in Prode Properties calculate the flash point and which are the limits of application ?
I know it is based on Le Chatelier method and it is limited to low pressures, for a pressure above 0.2 Atm should I define a different method ? 


#2 marchem

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Posted 14 March 2015 - 11:03 AM

at 0.2 Atm you shouldn't find problems.

Prode Properties stores flammability limits and heats of combustion for most chemicals in database,
the flash point can be calculated from Lower Flammability Limits and vapor composition,
the procedure is very simple

1) given P solve phase equilibria and determine composition
2) calculate the flammability limits at T (values in Prode database are stored at 25 C) with Zebatekis correlation (LFL - (0.182*(T-tf) / Hc)
3) for a mixture, lower flammability limit is calculated by Le Chatelier method
4) iterate to find the temperature corresponding to the lower limit partial vapor pressure

that is the method but since Prode Properties allows to extract values (of each chemical in database)

you can easily modify the above or create a different procedure.



#3 pdender

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Posted 24 March 2015 - 09:34 AM

thanks marchem,

I presume hc is the heat of combustion which Prode Properties calculates with the method StrHC(stream),

is it correct ?



#4 serra

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Posted 27 March 2015 - 11:49 AM

Hci is. the net heat of combustion,

as said by marchem, value is estimated by the function
Li(t)=Li(25°C)−0.182*(t−25)/Hci



#5 pdender

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Posted 01 April 2015 - 06:47 AM

thanks,

do you know how accurate these numbers are for mixtures ?

I have the values for pure fluids but I need those for mixtures.



#6 marchem

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Posted 04 April 2015 - 07:42 AM

pdender,

I know only a limited number of sources for flash points of mixtures,

one is DDB (Dortmund Data Bank),

comparing calculated vs. experimental data (for two mixtures) I found differences in the range 7-13 K






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