Liquified petroleum gas (LPG) is a fuel providing energy that can be found in our everyday life as it is used in many household appliances for cooking, heating, and hot water.
It is called liquefied gas because it is easily transformed into a liquid.
LPG needs only low pressure or refrigeration to change it into liquid from its gaseous state.
As a gas, LPG expands to 270 times its volume as a liquid. Therefore, it’s only logical that LPG is stored and transferred as a liquid, under pressure, in a gas bottle (e.g. propane tanks). LPG turns back into gas vapor when you release some of the pressure in the gas bottle by turning on your gas appliance.
Almost all of the uses for LPG involve the use of the gas vapor, not the liquefied gas. The LPG gas is ignited and burned to provide heat energy for various applications.
In this extensive guide, we are going to explore what is LPG and how does it work.
To begin with, LPG is used on gas stoves, cooktops, ovens, as heaters, fireplaces, and gas hot water systems are all popular in-home gas appliances.
There are also clothes dryers that run on petrol. BBQs, patio heaters, rooftop fireplaces, pizza ovens, and fire pits are all types of outdoor gas appliances.
Thousands of different commercial and industrial applications exist. LPG-fueled hot air balloons, Zamboni devices for ice rinks, and use as a propellant gas in various aerosol items are only a handful of the more uncommon applications.
LPG composition is primarily propane, butane, isobutane, butylenes, propylene and mixtures of these gases.
LPG is composed of liquid or gas (vapor), depending on pressure and LPG gas temperature.
Natural Gas Liquids (NGL) have the same LPG composition plus a few more gases not normally included in LPG. The full NGL list of components includes: ethane, ethene, butylenes, propylene, propene, isobutene, butadiene, pentane, pentene and pentanes plus, as well as propane, butane and isobutane.
LPG expansion is 270 times the volume of gas to the volume of liquid. So, 1L of liquid LPG (propane) expands to equal 270L of gaseous LPG. As there are 1000L in a cubic meter (m3), 1L of liquid LPG expands to 0.27m3.
Water boils at 100°C or 212°F, becoming a gas (steam). In contrast, LPG (propane) boils at -42°C or –44°F, becoming gas vapor. LPG stays liquid because it is under pressure in a gas cylinder.
The propane ignition temperature in air (ignition temperature of propane gas) is when it reaches a temperature between 470°C – 550°C (878°F – 1020°F). At this temperature, the propane will ignite without the need for a flame, spark or other ignition sources.
Propane flame temperature is 1967°C (3573ºF).
The dew point for LPG-propane is the temperature at which the gas transforms into a liquid state, a process known as liquefaction.
What is liquefaction?
Liquefaction is the method of transforming LPG vapor to LPG liquid, and it is dependent on the temperature and pressure of the vapor. The higher the temperature of the vapor, the higher the pressure needed to convert the vapor to liquid.
For propane vapor at 20°C must be pressurized to about 836 kPa to see it liquefy, and at 50°C, about 1713 kPa pressure is required. The lower the temperature, the easier it is to liquefy the vapor. For n-Butane vapor at 20°C must be pressurized to about 115 kPa to see it liquefy, and at 50°C, about 510 kPa pressure is required.
The liquefaction conditions for Propane and Butane mixtures are also affected by the structure of the mixture, as well as the temperature and pressure of the vapors