US plant to test use of NZ lignite

Photo / Greg Bowker.

American regulators have approved an experimental North Dakota coal-drying plant which has imported more than 400 tonnes of New Zealand lignite to test in the hope the same process can be used in Southland.

But the processing of the coal has been put back to this month or early next month after delays to construction of the plant by a fierce winter, said a Solid Energy project manager, Greg Visser.

"There have been days of -40C where workers were able to throw a glassful of water in the air and see it freeze before it hit the ground," Visser said.

Ice and snow storms stopped workers getting to the site for four or five days at a time.

GTL Energy USA is building the plant to test a process called beneficiation that removes water and pollutants from low-quality lignite coal - a low-grade brown coal, also plentiful in western North Dakota and Wyoming.

Solid Energy sent its trial shipment of Southland lignite to see whether the process can be used in North Dakota to start exploiting its $100 million worth of land with access to about two billion tonnes of lignite.

The plant's developers say the mechanical technique, which produces chunks of coal the size of charcoal briquettes, decreases the coal's weight, increases its energy value and allows it to burn more cleanly.

The coal is first finely ground, and the process would work regardless of whether the water in it is frozen, Visser said.

Lignite coal contains 30 per cent to 60 per cent water, which degraded its energy value and made it too expensive to ship - unless the water could be removed.

GTL Energy USA, a subsidiary of Australian coal mining company GTL Energy, began building the plant in October 2008.

Solid Energy hopes the process will remove enough water so the low-quality coal can be shipped back to New Zealand as briquettes.

It has a joint venture with GTL Energy to investigate building a briquetting plant at the former paper mill at Mataura, 10km east of its New Vale coal mine in eastern Southland.

The North Dakota plant is expected to produce 280 tonnes of briquettes, said Visser.

Nearly 200 tonnes will be sent back to New Zealand for trials among potential clients. The remainder will be tried in American boilers, which are similar to New Zealand ones.

- NZPA