Notes

Slide Show

Outline

1	PETE 310 Lectures # 9 & 10 Ideal and Real Gases
2	Equations of State The Ideal Gas Ideal gas properties Volume of gas molecules is negligible compared with gas volume Forces of attraction or repulsion between molecules or walls of container are zero No loss of internal energy due to collisions
3
4
5	Internet Lesson on Ideal Gas Behavior Experimental instructions Problems with solutions
6	Ideal Equation of State Construction
7	Boyle & Charles laws
8	Boyle & Charles laws
9	Ideal Gas Mixture The pressure in a vessel containing an ideal gas mixture (n) or a single gas component (n_k) is
10	Partial Pressure P_k is the partial pressure of component k, and by definition
11	Density of ideal gas
12	Mixtures of Ideal Gases Dalton’s law of partial pressures Amagat’s law of partial volumes Specific gravity of a gas
13	Apparent Molecular Weight of a Gas Mixture Determine the M_wa and density of a mixture of 30%C₁, 40%C₂, and 30%C₃ at T=200^oF and P=4000 psia
14	Behavior of Real Gases
15	Equations of State for Gases Ideal gas Real gas
16	Compressibility Factor Charts
17	The Principle of Corresponding States
18	Typical Reduced Parameters Material properties are usually expressed in terms of reduced parameters such as: Reduced Temperature:
19	"Reduced Pressure:" Reduced Pressure: Reduced Molar Volume:
20	Reduced Parameters Usually T_r and P_r à V_r obtained as a function of T_r and P_r These are called two-parameter Corresponding States models Three-parameter corresponding states models improve predictions but third parameter is not V_r (not independent variable)
21	Generalized Corresponding States Three-Parameter This third parameter is called the acentric factor. It takes into account the non-spherical nature of molecules Peng Robinson and the Soave Redlich Kwong equations of state (EOS) are examples of three parameter corresponding states models.
22	Compressibility Factor Charts Following the POC only one compressibility factor chart can be used to determine volumetric properties of any pure fluid by using its reduced properties. The shape of this chart is in general.
23	Corresponding States Correlations & Models
24	Extension of Corresponding States to Mixtures Z factor charts (all built from EOS) are also used for multicomponent systems in this case the coordinates used are “pseudo-reduced properties” For a mixture you can use the same charts as for a pure component.
25	Pseudoreduced Properties For mixtures the same type of charts apply but using “pseudoreduced properties” which are defined similarly as the ratio of pressure (or temperature) with “pseudoreduced critical pressure" (or temperature). These pseudocritical properties are an average of the critical properties of the components in the mixture. Charts for mixtures can also be used for single component fluids.
26	Compressibility factor Z as a function or pseudoreduced pressure
27	Pseudocritical Properties of Natural Gases Pseudoreduced Pressure Pseudoreduced Temperature
28	Pseudocritical Properties of Natural Gases If only the specific gravity and Mw of of the gases is known then charts are available to estimate these pseudocritical properties (McCain figure 3-10 ).
29	Pseudocritical Properties of Natural Gases Naturally the degree of accuracy is reduced substantially. We well see methods when compositional information is available, in this case:
30	Pseudocritical Properties of Natural Gases Once Z is evaluated you can find the gas density as
31	Z-factor chart for low reduced pressures