When smaller may be bigger

April 11, 2011
Early in the last decade, an LNG train could produce on average about 2.5 million tonnes/year (tpy).

Warren R. True
Chief Technology Editor-LNG/Gas Processing

In the LNG industry, size matters.

Early in the last decade, an LNG train could produce on average about 2.5 million tonnes/year (tpy). By decade's end, Qatar celebrated reaching its long-announced goal of 77 million tpy in LNG production capacity, based upon trains of 7.8 million tpy each, the world's largest.

Elsewhere, Algeria is replacing several smaller trains, damaged in a 2004 explosion, with a single much larger one.

And there's the scale of production capacity being installed off Australia's western and northwestern coasts and in its northeast Queensland state. By about 2025, current projects under construction or planned will push the country's LNG production capacity to more than double that of Qatar's.

Then there are the LNG megavessels in the last several years, with Q-Max carriers bringing shipments of 260,000 cu m or so into those ports able to accommodate them. Their size nearly doubles the world's average, and one makes an impressive sight being edged up to a loading dock.

But, while these advances are dramatic and eye-catching, another trend is afoot in the LNG world in the opposite direction. And that trend was much the talk recently at Gastech in Amsterdam and PennWell's Offshore Asia 2011 in Singapore.

Land and sea

An article of faith throughout the LNG world has been that scale—i.e., big—is necessary. This has been driven by the expense of producing and handling a cryogenic liquid. But, technology has responded.

The catch-all term for what we now see happening is "small-scale LNG." It has come to apply broadly to any liquefying of methane in order to store and transport it to be later revaporized for a specific and narrow (i.e., small scale) use.

Think of a garbage truck in California equipped with a tank capable of holding LNG for use by a small onboard vaporizer, then to feed natural gas to an engine.

Natural gas as a vehicle fuel has been around for some time. Onboard storage, however, has often presented problems. Compressed natural gas (CNG) makes some think—unfairly—of a bomb just waiting for a puncturing agent. The same holds for methane's cousin, propane.

Since LNG is not under pressure, that element can be taken out of the equation.

LNG has also seen early use, especially in remote regions of China, as a means of storing and moving relatively small volumes of natural gas for later injection into small electricity-generation systems.

Indeed, at Offshore Asia 2011, several LNG speakers noted how LNG in small quantities is allowing much cleaner-burning natural gas to replace highly polluting fuel oil and coal in small, remote villages and towns.

Electricity is key to most remote locations' economic growth, but it often comes at the high price of environmental damage. Burning natural gas to generate the needed electricity appears to many to be the optimum solution, at least until development connects the demand to a wider electricity grid.

Growth and promise

Although not strictly speaking small in scale—except compared with a 7.8-million tpy LNG train, use of LNG aboard ocean-going vessels promises to address one of the major global sources of greenhouse gas emissions—vessels burning bunker fuel.

Last year, Finland's Wartsila, which provides propulsion systems for ocean-going vessels, contracted with Sweden's Tarbit Shipping to convert the 25,000-dwt product tanker Bit Viking from heavy fuel oil to LNG propulsion. Statoil operates the tanker along the Norwegian coastline.

Specifically, the conversion involves changing to six-cylinder in-line Wartsila 50DF dual-fuel engines that will run on LNG, according to the supplier.

Scale, then, continues to be critical to the growth of LNG. But now it's scale in both directions that yields flexibility and underpins the promise that human activity, widely blamed for the planet's warming, will help to slow and perhaps reverse that warming.

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