Question

In chemical engineering thermodynamics, I don't know when i use SRK/RK/Lee Kesler or z=z0+w*z1 equation. If the problem assume high pressure situatioin, could i only use z=z0+w*z1 equation?

For example <Five mol of calcium carbide are combined with 10 mol of water in a closed, rigid, high-pressure vessel of 1800 cm3 internal empty volume. Acetylene gas is produced by the reaction: The vessel contains packing with a porosity of 40% to prevent explosive decomposition of the acetylene. Initial conditions are 25°C and 1 bar, and the reaction goes to completion. The reaction is exothermic, but owing to heat transfer, the final temperature is only 125°C. Determine the final pressure in the vessel.>

When i solve the upper problem, could i use other equation like lee/kesler equation? not only SRK?

Answer 1

Among the methods asked by you, one can categorize them as following:

Cubic equation of states (EoS) --> SRK and RK

Generalized Correlation -->Lee/Kesler Correlation and Pitzer Correlation (Z =Z⁰ + wZ¹).

Both cubic EoS and Generalized correlations are applicable for gases at high pressure (non-ideal). However, the Lee/Kesler correlation is often more accurate as it is based on a modified form of the Benedict/Webb/Rubin equation of state (6th order EoS).

All these models are valid for non-polar fluids. For given example 'acetylene' being non-polar, the Lee/Kesler correlation will be most appropriate.

Also note that SRK is more accurate than RK.