LNG vs. Propane
November 03, 2013
Energy providers in Yukon and NWT are actively considering investments in plant to enable the storage and use of Liquified Natural Gas (LNG). Propane has been shipped in by truck for decades. What is the difference in these commodities ?
Liquefied natural gas or LNG is natural gas (predominantly methane, CH4) that has been converted to liquid form for ease of storage or transport. Liquefied natural gas takes up about 1/600th the volume of natural gas in the gaseous state. 1 litre of LNG is equivalent to about 620 litres of natural gas.
- LNG is produced, or liquefied, from natural gas using an automated refrigeration process. LNG is transported and stored at low pressure in insulated containers.
- A single truck can haul up to 100,000 litres of LNG, representing 2,400 GJ of energy conversion potential.
- Before utilizing, LNG is regasified by warming the LNG to -5o Celsius through heat exchangers using ambient heat sources.
- Combustion of natural gas results in 30% less direct greenhouse gas emissions than diesel.
- The energy density of LNG is comparable to propane.
Propane is a three-carbon alkane with the molecular formula C3H8, normally a gas, but compressible to a transportable liquid. Unlike natural gas, propane is heavier than air (1.5 times as dense). In its raw state, propane sinks and pools at the floor.
- Propane is produced from both natural gas processing and crude oil refining. It is nontoxic, colorless and virtually odorless. As with natural gas, an identifying odor is added so the gas can be readily detected.
- One unit of propane in a liquid form has the same energy content as 270 units of propane in a gaseous form. Propane is a less dense product than LNG.
- Propane is stored and transported in steel cylinders as a liquid with a vapor space above the liquid. It does not have to be cooled like LNG. The vapor pressure in the cylinder is a function of temperature. When gaseous propane is drawn at a high rate, the latent heat of vaporisation required to create the gas will cause the bottle to cool.
- The trucks are used for propane transport typically carries 40,000-45,000 L. Less capacity than LNG trucks.
Natural gas contains approximately 1,030 BTU per cubic foot and propane contains 2,490 BTU per cubic foot.
LNG is a denser fuel that offers greater cost savings to energy producers than propane. Natural gas prices now are very low, meaning low cost LNG is pricing out other fuels like diesel and propane.
There is potential in the future to locate LNG liquefaction facilities in natural gas supply areas closer to markets in northern Canada. This is particularly true of NWT with vast natural gas resources in the Mackenzie Delta, the Cameron Hills and near the BC border.
- a)http://en.wikipedia.org/wiki/Liquefied_natural_gas and http://en.wikipedia.org/wiki/Propane