LNG is transported between continents in double-hulled ships specifically designed to handle the low temperature of LNG. These LNG ships are up to 1000 feet long, and can carry up to 250,000 mt of LNG and require a minimum water depth of 40 feet when fully loaded. LNG can also be transported in smaller batches of 20 mt by road rail or ship in ISO framed storage vessels, or by truck / trailer barrels.
When LNG is received in the UK, it is transferred into insulated storage tanks that are built to specifically hold LNG. These tanks are fully insulated to keep the liquid at -161˚C and to minimise the amount of boil off generated due to evaporation. The temperature within the tank will remain constant if the pressure is kept constant by controlling the tank pressure via boil off management. The boil off gas is either re-liquefied and returned to the storage tank or heated up to be injected into the gas transmission and distribution systems. When natural gas is required, the LNG is vaporised to natural gas by warming upto 10’C via a regasification processes involving heat exchangers.
LNG can be used in its liquid form typically as an alternative fuel for HGV‘s or more commonly is regassified by heating to return it to compressed natural gas that can be used in households for heating and cooking or for electricity generation and other industrial uses.
Natural gas is the cleanest fossil fuel when burnt, it produces less emissions and pollutants than either coal or oil based hydrocarbons. LNG is more economical to transport across large distances as it occupies only a fraction (1/600) of the volume of natural gas, and therefore takes up less space.
If LNG comes in contact with warm air it becomes a visible vapour cloud, as this continues to get warmer, the vapour cloud becomes lighter than air and rises. When LNG vapour mixes with air it is only flammable if within 5%-15% natural gas in air. Beyond these ranges the fuel / air mixture is ether too rich or to lean for ignition to take place.
LNG is not explosive, LNG vapour will only explode contained and pressurised within an enclosed space. LNG vapour is only explosive if within the flammable range of 5%-15% when mixed with air.