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Liquefied natural gas (LNG)
Demand for natural gas – the cleanest fossil fuel – continues to grow. But with many large gas fields located far from where it is needed, making sure vast resources of natural gas are not left behind in the ground means coming up with ways to cost-effectively and safely transport them. LNG has proved to be an answer.
LNG tanker
LNG is natural gas that has been cooled to -162°C ( 260°F). At this temperature, it turns into a clear, colourless, non-toxic liquid that is 600 times smaller in volume than in its gaseous state, making it much easier to transport.
The change made to the gas is physical rather than chemical, meaning it can revert to its previous form. Once at its destination, the LNG is returned to a gaseous state at a re-gasification plant which brings it back to ambient temperature before it is distributed onward through conventional pipeline networks.
Shell helped pioneer the LNG sector, through its involvement in constructing the world’s first plant designed to export LNG at Arzew, Algeria, in 1964. Since then we have continued to improve the technology behind LNG.
The liquefying process involves several cooling stages. Current designs use a mix of refrigerants in the first cooling stage rather than just the one, as was previously the norm. This mix has helped us build the first LNG plant in extremely cold climates such as at the plant on Russia’s Sakhalin island. Varying the concentrations of the refrigerants at the plant means we can compensate for very high fluctuations in outside air temperature over the seasons, maximising LNG production.
Shell is now developing the next generation of LNG technology. In one of our new designs, gas flows through two simultaneous, parallel cooling cycles, rather than the usual series of three successive cycles. This parallel set-up boosts the maximum capacity of a single production unit to 8 million tonnes per year, compared to the typical 5 million of a conventional design. It also improves reliability, as production can continue at 60 per cent capacity if one of the parallel cycles shuts down.Our technology in this area is growing quickly as we head into our fifth decade of producing and transporting LNG to where it’s needed.
