Substantial NOₓ reductions at Salten, Norway

The rebuilding of two furnaces at Elkem Salten in Norway has reduced Elkem’s emission of NOₓ with nearly 1,300 tonnes per year. Planned rebuilding of two more furnaces will cut emissions with another 4000 tonnes a year.

Nitrogen oxides (NOₓ) are gases that lead to higher concentrations of tropospheric ozone, acid precipitation and global warming. These emissions can be harmful to ecosystems and vegetation, as well as health. 

The formation of NOₓ takes place in the furnaces at temperatures above 1,500 °C. Understanding the processes behind the formation of NOₓ has made it possible to redesign the furnace hood on Elkem’s smelting furnaces in order to reach a significant reduction of the emissions. Elkem has performed intensive studies together with different research institutions and full-scale testing at Elkem Salten to develop technology that can give substantial reduction in emissions of NOₓ from the smelting process.

With financial support from the Norwegian NOₓ Fund the technology has been rolled out on three furnaces giving a reduction of almost 1,300 metric tons NOₓ per year. Two other furnaces will also be rebuilt in the in the near future giving a total reduction of NOₓ emissions of approximately 1,700 tonnes, which equals the NOₓ emissions of approximately 340,000 cars, based on an average NOₓ emission from a car of about 5 kilograms per year. The total investment in the rebuilding projects exceeds NOK 300 mill.

In addition to furnace design, furnace operation and product type also have an effect on NOₓ emissions. More NOₓ is formed at higher temperatures which are generated when producing silicon with higher purity. As the market demands more speciality products with a higher silicon purity some of the environmental gain may be lost, but Elkem is still working actively to ensure that increases are as low as technical possible.

This article was first published in Elkem’s sustainability report 2016.