How to add the compound methyl nitrite (CH3ONO) in DWSIM ?

[Prashant Kumar]

Methyl Nitrite (CH3-O-N=O)
I wish to add methyl nitrite in DWSIM but there is no UNIFAC group related to -O-N=O. How else can I add it?
Thanks.

[Gregor Reichert]

Hi,
as you already noticed, no group is available for that component. Neither in UNIFAC nor MODFAC. Even the most advadnced model MODFAC(NIST) doesn't own a O=NO- group.
This fact doesn't allow you to calculate activity coefficients for mixtures.

But most important in the beginning are physical property data of a component to establish a new simulation.
These properties are estimated with the Joback-model. The groups of this model usually are assigned via UNIFAC groups automatically. But as this is not possible here, you have to assign these groups manually.
I think you may try the following Joback groups:
1 x -CH3 (group 1)
1 x -O- (group 22)
1 x =O (group 29)
1 x -N= (group 34)

This should result in a component wich can be used for simulations having at least similar properties to the real component. I strongly reccomend to replace as much estimated values by literature data or own data.
For calculations of phase equilibria you have to stick to ideal mixture calculations until you regress your own interaction coefficients for a model like NRTL or UNIQUAC

Gregor

[Prashant Kumar]

Thank you !