Liquefied Petroleum Gas Lpg

Overview

Engineering reference data for Liquefied Petroleum Gas Lpg in gases and compressed air.

Key Formulas

Ideal Gas Law

$PV = nRT$

Pressure × Volume = moles × gas constant × temperature.

Boyle's Law

$P_1 V_1 = P_2 V_2$

At constant temperature.

Charles's Law

$\frac{V_1}{T_1} = \frac{V_2}{T_2}$

At constant pressure.

Variables

Composition of LPG

LPG is a mixture of hydrocarbon gases. The primary components and their chemical formulas are listed below.

Key Properties & Phase Behavior

LPG exists in a liquid state under moderate pressure or at low temperatures, transitioning to a gaseous state under standard atmospheric conditions. This phase change is fundamental to its storage and transportation.

A key property is its calorific value, which represents the energy released during combustion. For LPG blends, this is often given as a range or for a reference composition like propane. The energy content can be calculated using the lower heating value ($LHV$) or higher heating value ($HHV$) of the individual components.

For storage, the pressure in a tank is governed by the vapor pressure of the mixture, which depends strongly on temperature. The relationship is often approximated using the Antoine equation for a pure component: $\log_{10}(P) = A - \frac{B}{C + T}$ where $P$ is the vapor pressure (in mmHg or bar), $T$ is the temperature (in °C or K), and $A$, $B$, and $C$ are component-specific constants. For LPG mixtures, more complex models like the Peng-Robinson equation of state are used to predict bubble point and dew point pressures.

References

• Original Source