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Aug-2013

As cold as ice, liquefying LNG beyond the arctic circle

Building a low-carbon economy is one of the great challenges of our time. In order to protect the climate, the world needs clean energy and natural gas is an important stepping stone on that journey, bringing us power with a much lower carbon footprint.

Susan Brownlow
Linde Gases Division
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Article Summary
Natural gas, a mixture of primarily hydrocarbon gases, is colourless and odourless in its purified form and is the cleanest fossil fuel with the lowest carbon dioxide emissions when burnt. As well as an important fuel source, it is a major feedstock for fertilizers and petrochemicals. As a raw material, it is almost as versatile as crude oil, yet is significantly kinder to the environment.

Burning methane, the principle component of natural gas, produces around 30% less carbon dioxide (CO2) than crude oil, and almost 45% less CO2 than coal. In addition, it emits significantly fewer pollutants - around 90% less sulphur, approximately 80% fewer nitrogen oxides and no heavy metals or soot particles. Furthermore, natural gas reserves are forecasted to continue to yield for at least another 200 years.

Natural gas is already one of the most important sources of energy today, covering around 25% of global energy requirements and this figure is set to rise. But while it is evident that natural gas stands to play an important role in the energy mix of the future, innovative technologies for exploration, production, processing and transporting it are key factors.

As with oil, most natural gas deposits are located far from the actual point of use. Natural gas can be transported via pipeline or it can be liquefied in order to allow its economic transportation over large distances by ship or truck – particularly to and from remote areas which are not serviced by a pipeline network or where it is uneconomical to use a pipeline.

Traditionally, the vast majority – around 90% – of natural gas is pipelined over long distances to power plants, industrial facilities and homes. However, after about 3,000 km onshore pipeline, after about 1,500 km offshore pipeline or  in case of distribution to diverse, small consumers in remote areas, pipelines become uneconomical, with costs for pipe laying, materials and compressor stations outweighing the benefits. Liquefied natural gas (LNG) can be economically transported many thousands of kilometres and distribution to customers is much more flexible. Around 250 million tons  of LNG – representing about 10% of the natural gas market - are already transported around the globe each year.

After extraction in its natural form directly from the gas field, LNG production involves pre-treatment of the incoming gas, its fractionation into the diverse product fractions (e.g. natural gas, LPG, condensate) and liquefaction by cooling the natural gas down to a temperature of -163°C. This process reduces its volume dramatically to only 1/600th of its normal volume, resulting in an easily and cost-efficiently transported fuel.

LNG plants are typically distinguished by their capacity into small-scale, mid-scale and world-scale plants. The journey of the LNG begins for example at a world-scale LNG plant with capacities between 3 and 10 million tonnes of LNG per year. From the large storage tanks special LNG tankers then transport the LNG to LNG receiving terminals in ports all over the world, where the LNG is typically converted back to gas, fed into national pipeline grids and delivered to consumers.

Linde has a strong history in the LNG industry and a long track record in LNG plant, having designed, built and started up numerous LNG plants from small- to world-scale worldwide since 1967 served from its comprehensive technology portfolio. Linde is responsible for many of the innovative highly efficient processes in operation across the entire LNG value chain - from industrial scale liquefaction plants, over receiving terminals up to fuelling stations for LNG.

Liquefaction in a cold climate
In the inhospitable and icy cold of northern Norway stands the world’s largest liquefied natural gas production facility in arctic climate. Just outside the town of Hammerfest lies the small barren island of Melkøya, where Linde has built one of the world’s major natural gas processing plants – a showcase plant for LNG production, including vital liquefaction technology.

In this stark Norwegian landscape, 600 km north of the Arctic Circle, the project presented a formidable challenge from the outset. No world-scale plant of the size and capacity built on the small Island of Melkøya had been built before, especially not in such an inhospitable arctic climate.

The entire LNG operation is the world’s northernmost world scale LNG plant, located below Norway’s Barents Sea. The Snøhvit LNG project (‘Snøvhit’ - translated as ‘Snow White’) was constructed to exploit the resources of three gas fields in the Barents Sea - Snøhvit, Albatross and Askeladd (250m to 345m deep), which lie about 140km northwest of Hammerfest. The fields, which were first discovered in the 1980s, have estimated reserves of 193 billion cubic metres of LNG, 17.9 million cubic metres of condensate and 5.1 million tonnes of natural gas liquids. Snøhvit and Albatross are already onstream since 2007 and Askeladd is due to come onstream by 2014-15.

The project was led by Norwegian energy group Statoil as part of a consortium of several oil and gas companies including Petoro, Total, GDF Suez, Hess, and RWE Dea. Engineers from Linde and Statoil started first discussions for an LNG plant on Melkøya in the late 1990s. Linde engineers responsible for developing the plant were required to plan for every eventuality, with design of the liquefaction module being the top priority. Storms were simulated, temperatures in which technicians would have to work considered, and even how snow drifted was tracked. Engineers also constructed a test rig which they set up on Melkøya to see how the snow accumulated and whether it affected the rig. Even with today’s sophisticated technology, a liquefaction plant of this scale in such an environment would still be an enormous challenge, which underlines the level of technical expertise which had to be channelled into the Melkøya development process.
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