In liquefaction plants, NATURAL GAS (mainly METAN ) is brought to the state of saturated liquid at a temperature of about-161 ° C and ambient pressure, with a volume reduction of more than 600 times; In international trade, LNG ( LPG NATURAL LIQUID) is loaded and transported by sea into the double hull tanks of special vessels, called methane, with a loading capacity of up to 150,000 m3.
The regasification process takes place in special terminals and consists in generating liquid pumping from the vessel tank to the terminal tank, in a subsequent COMPRESSION and heating up to the inlet temperature in the pipeline (Figure - Scheme of the regasification and layout process of a type plant ).
LNG drainage from the ship to the terminal takes place through the submersible pumps in the ship's tanks; the liquid is then sent from the STOCCAGGIO storage tank to the vaporizers by means of delivery pumps (multistage centrifuges), which have the task of ensuring the pressure required by the regasification operations.
The operating pressure of the terminal varies significantly according to the intended use for NATURAL GAS and, in the case of a DISTRIBUTION network , they are normally higher than the critical one (46 BAR for the CH4).
In vaporizers, the LNG passes over heated to a temperature dependent on the heat source.
The two most popular types are: open ranks, using sea water, and submerged flames, which use as a source of heat water heated by an internal burner.
If the required heat is supplied by seawater, this, after being pumped into vaporizers, is discharged into the sea at a temperature below 7 ° C compared to the inlet.
The NATURAL GAS is sucked and pressurized by compressors to then be injected into the network or sent to the user; one part is often used for self-consumption of the plant: in fact, the terminal is normally equipped with an electric power generation system consisting of Diesel or turbocharged engines.
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