概览
Drying, filtering and liquefaction in the oil & gas industry
Quality and composition based measurement of liquefaction
After well-head processing, natural gas is collected and typically delivered to the liquefaction plant by pipeline. The delivered quantity is measured in a custody transfer metering skid, and analyzer instrumentation determines the composition and quality. Before the main liquefaction processes, various filters and scrubbers complete the drying, and remove impurities such as mercury, H2S and CO2.
The major component of LNG is methane, which liquefies at -162°C. Cooling is achieved in one or more liquefaction trains. In this process, various constituents found in natural gas (propane, ethane, and methane) are typically used as refrigerants, either individually or as a mixture. During the cooling processes, ethane, propane and butane are extracted at various stages, as ‘natural gas liquids’ (NGLs), and are measured and recovered as by-products.
Once liquefied, the LNG product is stored in large, well insulated tanks, awaiting onward transport. These tanks are fitted with cryogenic level switches to control high and low levels, but the LNG is not actively cooled - so the liquefied gas inside the tank boils. The boil off gas (BOG) is returned to the liquefaction train, where it can be re-processed.
KROHNE supplies the custody transfer metering systems for natural gas entering the LNG plant, and for the cryogenic LNG product, as well as other cryogenic measurement instrumentation for use on the plant. Amadas (analyzer management) software systems from KROHNE guarantee the performance of the analyzers used to determine the quality of the natural gas and LNG. KROHNE ultrasonic and Coriolis mass flowmeters are suitable for all LNG production or distribution measurement solutions.