 # Peng Robinson Equation In Eq-Comp

EQ-COMP is a process simulation software that predicts vapour-liquid equilibrium properties like bubble point, hydrocarbon dew point, water dew point, two phase properties, phase envelope, vapour/ gas compressibility factor, liquid compressibility factor and latent heat of vapourization for multicomponent mixtures of non-polar or mildly polar hydrocarbons and non-polar or mildly polar inorganic gases. These VLE properties can be used in designing various equipments in hydrocarbon industry like multicomponent distillation columns, hydrocarbon storages, flash chambers, hydrocarbon pumps etc and in oil and gas well simulation studies. EQ-COMP also draws binary VLE curves like concentration diagrams (x-y plots), temperature-concentration diagrams (T-x-y plots), enthalpy-concentration diagrams (H-x-y plots) and critical loci curves for binary mixtures of non-polar or mildly polar hydrocarbons and non-polar or mildly polar inorganic gases. These binary VLE curves can be used in Mccabe Thiele method or Ponchon Savarit method to design distillation columns for binary mixtures.

Cubic equations of state like Soave-Readlich-Kwong equation and Peng-Robinson equation are single equations that can predict both liquid and vapour properties. This makes them the most simple and generalized method for calculating Vapour Liquid equilibrium properties. Cubic equations give accurate vapour phase properties and reasonably accurate liquid phase properties for non-polar or mildly polar compounds. EQ-COMP uses Peng-Robinson cubic equation of state for calculating various vapour liquid equilibrium properties. Peng-Robinson equation was initially published in year 1976 and its modified version was published in year 1978. EQ-COMP uses modified version of Peng-Robinson equation published in year 1978. Peng-Robinson equation is the preferred equation used for calculating VLE properties for mixtures of non-polar or mildly polar compounds. As most of the hydrocarbons and inorganic gases present in petroleum upstream and downstream systems are either non-polar or mildly polar so Peng-Robinson equation is the preferred equation for petroleum systems. Peng-Robinson equation predicts liquid phase properties more accurately than other cubic equations like Soave-Readlich-Kwong equation.

Modified version of Peng-Robinson equation published in year 1978 is given below:

R T a(T)
P = ----------- - -------------------------------
v - b v (v + b) + b (v - b)

Here, R is the gas constant, P is the absolute pressure, T is the absolute temperature, v is the molar volume, and b and a(T) are given by:

R Tc
b = 0.07780 ----------
Pc

R 2 Tc 2
a(T) = 0.45724 ------------- (T)
Pc

T) = [1 + k (1 - ( T/Tc ) 0.5) ]2

 <= 0.49 k = 0.37464 + 1.54226  - 0.26992 2

 > 0.49 k = 0.379642 + 1.48503  - 0.164423 2 + 0.016666 3

EQ-COMP calculates vapor liquid equilibrium properties like bubble points, hydrocarbon dew points and VLE curves for hydrocarbon mixtures, Vapour Liquid Equilibrium, Phase Envelope, Dew Point, Phase Equilibrium, Bubble Point.

Posted on 2013-07-11, By: *

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