Natural Gas LNG Analysis

Natural Gas LNG Analysis

The UK’s demand for Natural Gas is expected to rise considerably over the next ten years, however our indigenous supply of North Sea oil is in decline. There is currently a market inclination to import Natural Gas in its liquefied form because Liquefied Natural Gas (LNG) occupies 600 times less volume, and this therefore makes economic sense when transporting over long distances. The liquefied gas is transported by ship to LNG terminal facilities. There are currently a number of LNG terminals at various UK locations either being commissioned, under construction or in the planning phase. All of these terminals require analysis of the gas as it undergoes custody transfer.

LNG is stored in its liquid form at -161 degC and as a result the gas must be vaporised in order to determine its quality by analysis. Sampling and vaporising a liquid at such low temperature can be challenging because, apart from the low temperature, each component in LNG has a unique boiling point so care must be taken in the vaporisation process to ensure that fractionation of the gas mixture does not occur. Orbital’s solution to this problem is to use a vacuum insulated sample probe to prevent the sample system from ‘icing’ up and and a  close coupled high volume electric flash vaporiser to prevent fractionation. Orbital supply complete analysis systems for gas quality measurement, an analysis kiosk installed by Orbital on an LNG jetty is shown highlighted in the photograph.

According to international standards, there are two methods for measuring the energy value and quality of LNG entering an import terminal: these being continuous and discontinuous sampling. The discontinuous method relies on capturing a constant representative sample during the unloading period of a ship’s cargo and then analysing the sample as a single analysis. Continuous sampling relies on analysing the sample in real time with an analyser such as a gas chromatograph.

Orbital have installed 30 complete systems at different sites in the UK. We have installed both continuous and discontinuous methods for both import LNG analysis (Jetty), LNG ballasting, storage tank quality and pre/post re-condenser plants.