TABLE OF CONTENTS Liquefied petroleum gases (often referred to as LPG or LPGas) are a constituent of crude oil or the condensate of natural gas fields (NGL). They are the C3 and C4 hydrocarbons, propane and butane, respectively, which have the property of being gases at normal ambient temperature but can be liquefied and kept in the liquid state by quite moderate pressure. Gases released from crude oil are called associated gases while those found without heavier hydrocarbons are known as unassociated gases . The North Sea gas wells are good examples of the latter.
Methane is the major constituent of both associated and unassociated gas at source. There will be higher (heavier) hydrocarbons in varying amounts present in the gas, associated gas having more than unassociated gas.
When crude oil is refined some of the processes yield additional gaseous products. The C3 and C4 constituents differ from those released from crude oil or from NGLs, which are saturated hydrocarbons. Refinery gases are high in unsaturates , e.g. propene (propylene) and butene (butylene). These unsaturated hydrocarbons are a valuable source of chemical process intermediates and enjoy a large market alongside naphtha.
The major constituents of LPG can be shown by the following molecular diagrams:
No doubt the most successful exploitation of the peculiar properties of LPG has been its use as a fuel gas. Originally used predominantly in refineries for process heating, its value as a fuel was first realized before the...
