Propane is a versatile energy source used in many households and industries. This fuel powers home heating, cooking appliances, and industrial equipment. Its efficiency and portability make it a common choice for various applications.
Primary Sources of Propane
Propane is primarily a byproduct of processing natural gas and crude oil. It naturally exists as a component within these hydrocarbon mixtures found deep underground. As these raw materials are extracted, propane is collected as part of the gas or liquid stream. The availability of propane is closely linked to the production levels of natural gas and crude oil.
Extracting Propane from Natural Gas
A significant portion of the world’s propane supply comes from natural gas processing plants. Raw natural gas is primarily methane, but also contains other hydrocarbons like propane, butane, and ethane. These are known as natural gas liquids (NGLs). Separating NGLs from methane is essential to prevent operational issues in pipelines.
One method for separating propane is cryogenic expansion, which cools the natural gas stream to extremely low temperatures. As the temperature drops, NGLs, including propane, condense into a liquid while methane remains a gas. Another technique is absorption, where raw gas passes through a special oil that absorbs heavier hydrocarbons. The NGLs are then recovered from this oil by heating it.
Once collected, mixed NGLs undergo distillation in a fractionation unit. This process separates the NGL mixture into individual components like ethane, propane, and butane. Separation occurs based on their different boiling points. The isolated propane is then ready for further processing.
Producing Propane from Crude Oil
Propane is also generated during crude oil refining. Crude oil is a complex blend of various hydrocarbons. Refineries use fractional distillation to separate crude oil into different products, such as gasoline and diesel. This separation occurs in tall distillation columns where crude oil is heated and vaporized.
The vaporized crude oil rises through the column, cooling as it ascends. Hydrocarbons condense into liquid at different temperature levels. Heavier molecules condense lower, while lighter ones continue to rise. Propane, being one of the lightest hydrocarbons, rises to the top of the column where temperatures are coolest, typically around 25 degrees Celsius. It is collected as a gas, alongside other light hydrocarbons.
Refineries also produce propane through fluid catalytic cracking (FCC). This method breaks down heavier, complex hydrocarbon molecules into lighter ones. This increases the yield of products like gasoline. Propane is one of the lighter hydrocarbons produced during this cracking process, contributing to the overall supply.
Refining and Storing Liquid Propane
After extraction, propane undergoes refining to remove impurities like sulfur and water. This purification ensures quality standards and prevents corrosion in storage and transport systems. Specialized units use absorption or molecular sieves to remove these contaminants.
Propane is naturally colorless and odorless, making leaks undetectable. For safety, a distinctive odorant, typically ethyl mercaptan, is added. This compound gives propane its characteristic “rotten egg” or “cabbage-like” smell, allowing detection even at very low concentrations. Approximately 1.0 to 1.5 pounds of ethyl mercaptan are added per 10,000 gallons to ensure detectability.
For efficient storage and transportation, propane is converted into a liquid. This liquefaction occurs by compressing the gas and cooling it to around -42 degrees Celsius (-44 degrees Fahrenheit). In its liquid state, propane is approximately 270 times denser than its gaseous form. This allows large quantities to be stored and moved in a smaller volume. Liquid propane is then stored under pressure in specialized tanks and transported via pipelines, railcars, trucks, and ships to consumers.