概览
Regasification in the oil & gas industry
Converting LNG to natural gas
At the receiving terminal the LNG is stored within very large and extremely well insulated tanks. Custody transfer measurement systems on the delivered LNG and the boil off gas returned to the ship’s tanks to provide accurate accounting data on the received fuel into the terminal. Once the tanker has left, any boil off gas is compressed and re-liquefied in a condenser, or alternatively can be flared off, via a flowmeter.
To supply natural gas into the distribution system, for industrial and domestic use, the LNG must be heated to convert it back to a gas. Typically using the heat available from the sea-water around the terminal, the liquid LNG is evaporated in large heat exchangers fed by seawater. Then the gas frequently has some odour added, as methane has no smell. In the final process the gas is mixed with other gases, such as nitrogen, to adjust the calorific value to suit the local requirement.
On transfer into the high pressure natural gas transmission pipeline grid, the delivery is made via a custody transfer flow measurement skid, where the volume and calorific value again are measured for invoicing purposes.
KROHNE has vast experience with custody transfer and process measurements of natural gas in the gas phase, having provided many such metering installations. For LNG applications, KROHNE developed a series of ultrasonic flowmeters and Coriolis mass meters that can be installed fully insulated when used in cryogenic applications. Other KROHNE flow instrumentation is used in regasification plants to measure process gas flows, heat exchanger seawater flows, nitrogen seal gas flow on compressors, and LNG level control.