When natural gas is cooled to a temperature of approximately -160°C at atmospheric pressure, it condenses to a liquid called liquefied natural gas (LNG). One volume of this liquid takes up about 1/600th the volume of natural gas at a stove burner tip. LNG weighs less than one-half that of water, actually about 45% as much. LNG is odorless, colorless, non-corrosive, and non-toxic. When vaporized, it burns in concentrations of 5% to 15% on being mixed with air. LNG or its vapor is not explosive in an unconfined space.
Gas is typically cooled by successive cycles of refrigeration using giant compressors and heat exchangers. The liquefaction process removes the oxygen, carbon dioxide, sulfur compounds, and water. In its liquid form, natural gas is stored more efficiently and is economical to transport in dedicated LNG carriers to the receiving terminals. Indeed, converting natural gas into LNG is the only viable way to transport natural gas to places that are beyond the reach of pipeline systems. When LNG reaches its destination, it is returned to a gaseous state at regasification facilities. It is then piped to homes, businesses and industries.
Natural gas liquefaction dates back to the 19th century when the first practical compressor and refrigeration machine was built in Germany in 1873. Although the first LNG plant began operation in 1917 in the USA, significant commercialization did not get underway before 1941, when the first commercial liquefaction plant was built.
A naturally occurring mixture of Hydrocarbon based gases found in geological formations beneath the earth’s surface, often in association with oil, constitutes Natural Gas. Natural gas is composed primarily of methane (typically, at least 90%), but may also contain ethane, propane and heavier hydrocarbons. Small quantities of nitrogen, oxygen, carbon dioxide, sulfur compounds, and water may also be found. The liquefaction process removes the oxygen, carbon dioxide, sulfur compounds and water.
CNG is natural gas made by compressing natural gas to less than 1% of its volume at standard atmospheric pressure. CNG is odorless, colorless and tasteless. Due to its low density, it is compressed to a pressure of 200-250 kg/sq. cm to enhance the vehicle on-board storage capacity. Thus, this compressed form of Natural Gas is used as a fuel for transportation purposes.
PNG is natural gas piped to the homes and establishments for the kitchen and home heating like geysers etc. PNG installation inside the premises contains only a limited quantity of Natural Gas at low pressure at around 21milibar (mbar) and is much safer compared to LPG which is stored in a liquefied form in a cylinder.
LPG is a mixture of 60% butane and 40% propane. It is derived from the distillation of crude oil in the refining process, in the same manner that other fuels like kerosene, gasoline and diesel are extracted.
Natural Gas Liquids are the hydrocarbons in natural gas that are separated from the gas as liquids through the process of absorption, condensation, adsorption, or other methods in gas processing or cycling plants. Natural Gas Liquids includes ethane, propane, butane, and sulfur, which are derivatives of natural gas, extracted during gas refining.
Gas to liquids is a refinery process to convert natural gas or other gaseous hydrocarbons into longer-chain hydrocarbons such as gasoline or diesel fuel. Methane-rich gases are converted into liquid synthetic fuels either via direct conversion or via syngas as an intermediate.