Liquefied Petroleum Gas (LPG)
Liquefied Petroleum Gas refers to two hydrocarbon gases, butane and propane, or their combination, which are kept in a liquid state. Small amounts of compounds such as propylene and butylene are also usually present in LPG. LPG is mainly used for heating applications and as fuel for vehicles. It is also used in the production of aerosols and as a refrigerant gas in cooling devices such as refrigerators and freezers.
LPG is a byproduct of natural gas purification and crude oil refining in refineries. The thermal value of LPG is 46.1 MJ/kg, which is higher than gasoline and fuel oil. It produces more energy on an equal weight basis but less energy on an equal volume basis due to its gaseous state and lower density. One liter of LPG weighs between 500 to 580 grams, while one liter of gasoline weighs between 710 to 770 grams. LPG liquefies at 21 degrees Celsius under a maximum pressure of 8 kg/cm². It is colorless, odorless, and tasteless when produced, so sulfur compounds like mercaptan (including ethyl mercaptan and methyl mercaptan) are added for safety.
LPG should not be confused with LNG (Liquefied Natural Gas), which is essentially natural gas (mainly methane and ethane) liquefied for easier and more cost-effective transportation. CNG (Compressed Natural Gas) is also natural gas that has been compressed to occupy less volume.
LPG is produced in refineries as a byproduct of crude oil refining and natural gas purification. Other uses of LPG include serving as a refrigerant in cooling equipment such as refrigerators and air conditioners.
LPG is also used in aerosols. Its thermal value is higher than gasoline and fuel oil, equivalent to 46.1 MJ/kg.
These gases have higher energy in equal weights, but not in equal volumes, due to their gaseous state and compression. For example, one liter of LPG weighs between 500 to 580 grams, while one liter of gasoline weighs between 710 to 770 grams.
Conditions for Liquefying LPG
LPG liquefies at 21 degrees Celsius and a pressure of 8 kg/cm². Since it is colorless, odorless, and tasteless, sulfur compounds like mercaptan are added during production. It's crucial to note that LPG is different from LNG, which is natural gas liquefied for easier transportation. LNG is essentially natural gas like methane and ethane, and CNG is natural gas compressed to occupy less volume.
LPG can be used both in small household applications and in industry. Therefore, most people refer to LPG as liquefied gas. LPG is available in various cylinder sizes, including 50 kg, 11 kg (household), 5 kg (large picnic), 2 kg (medium picnic), and 1 kg (small picnic) in Iran.
In the past, before cities were equipped with natural gas pipelines, people primarily used these cylinders for household applications, such as cooking and lighting during power outages. However, after the advent of natural gas pipelines, the use of these cylinders decreased.
LPG is also used in small industries where there is insufficient space or budget for large gas tanks. In such cases, people use 50 kg portable LPG cylinders, placing them outside the building and connecting them to the building’s gas piping system.
Industrial LPG Tank Capacities
Standard industrial tank capacities are categorized based on water capacity (the amount of water they can hold). These include tanks of 125 gallons, 250 gallons, 500 gallons, 1000 gallons, 1500 gallons, 2000 gallons, 3000 gallons, 6565 gallons, 9800 gallons, 12000 gallons, 20000 gallons, and 30000 gallons.
All industrial tanks, except for the 125 and 250-gallon tanks, are cylindrical. Additionally, all these tanks consist of a tank body and two end caps. Larger tanks (from 9800 gallons and up) also feature manholes (MANHOLE).
