Understanding LPG Composition and Safety Chemicals

Liquefied Petroleum Gas (LPG) Overview

Liquefied Petroleum Gas (LPG) is a stored, pressurized gas primarily composed of propane and butane.

LPG is utilized in a wide range of applications such as cooking, heating, and industrial processes. It is stored as a liquid under high pressure, typically around 200-210 psi. When the pressure is reduced, LPG vaporizes and can be used as a gas for various purposes.

Origins of LPG

LPG originates from two main sources: natural gas and oil extraction, and crude oil refining. Approximately 60% of LPG is recovered during natural gas and oil extraction, while the remaining 40% comes from the refining of crude oil.

Natural Gas Processing

During the extraction of raw natural gas, it is a mixture of various gases and liquids. The commercial natural gas is primarily composed of methane. However, it also contains ethane, propane, and butane. These components are separated out depending on the 'wetness' of the gas produced. Natural gas processing is a significant source of LPG, contributing approximately 60% of the total produced.

Crude Oil Refining

In oil refineries, LPG is produced at various stages of the refining process, such as atmospheric distillation, reforming, and cracking. The yield of LPG from crude oil can vary between 1% and 4%, depending on the type of crude oil, the sophistication of the refinery, and market values for propane and butane. Crude oil refining is the source of approximately 40% of LPG produced worldwide.

Properties of LPG

The basic properties of LPG provide insight into its composition and why it is used in various applications.

LPG Attributes:

Odourless and Colourless: LPG is a mixture of propane and butane in varying compositions, and it is naturally odourless and colourless. Highly Flammable: LPG is highly flammable, with a flammable range in the 2 to 9 LPG:Air ratio. Phase Transition: At normal temperatures, LPG remains a gas. However, under pressure, it is kept in a liquid state. Expansion: One drop of liquid LPG can expand 250 times when it changes to vapour, resulting in the potential to fill a large space rapidly.

Emphasizing Safety with Ethyl Mercaptan

To ensure the safety of users, a strong-smelling chemical called Ethyl Mercaptan is added to LPG. Typically, it is added at a composition of 20-ppm (parts per million). Ethyl Mercaptan provides a distinct and pungent smell that is easily detectable by humans, allowing for early detection of LPG leaks before any potential hazards occur.