Estimation of C3 & C4 percentage in LPG from Density

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Estimation of C3 & C4 percentage in LPG

When LPG consist of n-Propane and n-Butane mainly with traces of ethane and pentane plus as impurities, LPG density at 15C can be used for estimation of C3 & C4 in it.  Depending upon the ambient temperature, there requires different percentages of C3 and C4 in LPG for proper efficient use in applications. Thus, following information empowers users more knowledge of C3 and C4 from LPG density at 15C.

The LPG derived from natural gas consists mainly Propane and Butane with minor impurities of Ethane and pentane.

Similar Apps on Petroleum Calculations developed by RJ Patel- see here.

Following table data taken from ASTM D 2598 can be used for estimation of LPG Composition.


Constants of Densities given above are empirical values for calculation purpose.
A trendline from above data, with assumption of approximate 1 % (Ethane + C5 & above) is derived as given in following table:  % in Vol.

%  C3 = 759.6 – 1305.5 x  (LPG Density@15 C).         Density in Kg/L or  g/cc.
%  C4 =  (99 - % C3).
% C2 + C5 = 1 % …..(Assumption)
Above equation is best suitable for LPG derived from Natural Gas.

Following table represents the data from above equation and from GC determination.
Sr.N.
LPG D15
% from Equation
% from GC

Kg/L
C3
C4
C3
C4
1
0.5463
46.4
52.6
47.3
51.9
2
0.5538
36.6
62.4
35.4
63.1
3
0.5647
22.4
76.6
23.5
75.2
4
0.5702
15.2
83.8
15.9
82.9
5
0.5773
5.9
93.1
6.6
92.4

Conclusion: The above equation estimates the C3 and C4 percentage satisfactorily in LPG.

An App giving LPG density conversion to 15 C and estimation of Propane and Butane as C3 and C4 can be found in authors App collection.

LPG Components C3 & C4 estimation from its Vapour pressure is given here.

Keywords:   LPG, Propane, Butane, Vapor Pressure, Density 

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