What are floating regasifiers and how does the regasification process work?

The floating regasifiers or FSRUs, Floating Storage and Regasification Units, those that could soon be installed in Piombino and Ravenna, are terminals capable of storing and regasifying natural gas. These are ships located near a port area, on the quay or offshore, which receive liquefied natural gas (LNG) at a temperature of -160 ° C from other LNG carriers and regasify it (i.e. bring it to a gaseous state) to be able to introduce it into the national gas transport network. Natural gas can be imported in the gaseous state, through the network of methane pipelines, or in the liquid state (LNG) by means of methane tankers. These ships receive the liquid gas from special gas liquefaction plants located in the exporting countries and take it to the regasification plants of the importing countries. Liquefied natural gas has a volume of about 600 times less than that in the gaseous state.Once near the FSRU, the LNG carrier ship that transports LNG at -160 degrees transfers the liquid gas to the terminal’s tanks. The transfer takes place via the steel unloading arms installed on the FSRU. The arms extend and hook onto the LNG carrier flanges. At that point the liquid gas is poured into the tanks and stored. Subsequently, according to market needs, the liquid gas is regasified. The regasification process is obtained by introducing the methane in the liquid state into a heat exchanger in which a warmer liquid flows, usually sea water, whose natural temperature is sufficient to restore the gas to the gaseous state. So LNG and sea water exchange energy (LNG yields cold, sea water yields heat), even though they never come into contact with each other. The heat exchanger consists of a steel coil (in which the LNG flows) immersed in a tank that contains water at room temperature, which is continuously recirculated to prevent it from cooling. The temperature at which the water is returned to the sea is constantly controlled and must be within the authorized limits. The gas at room temperature obtained from the regasification process is then compressed and injected into a gas pipeline that starts from the FSRU and reaches the national transport network. The floating regasifiers are managed so as not to hinder the normal economic and tourist activity of the ports concerned. On average, based on market conditions, the arrival frequency of LNG carriers is about one per week. The docking, mooring and unmooring operations last about two hours each and are carried out in accordance with the provisions of the maritime authorities in order to minimize any possible interference. Also in terms of safety, the studies carried out highlight the compatibility of the FSRU with other port activities.