Environment | Air Emissions
Sulphur dioxide
Xstrata’s principal emission to air is sulphur dioxide (SO2). The majority of sulphur dioxide emissions are from the Mount Isa complex which comprises copper, zinc and lead operations.
Overall Xstrata’s SO2 emissions (excluding Falconbridge) increased by 14,324 tonnes or 6% compared with 2005 to 252,888 tonnes. SO2 emissions at Mount Isa copper-zinc-lead complex increased by 14,726 tonnes or 6.6% compared with 2005 to 238,393 tonnes. This performance comprises a 23% increase in SO2 emissions from the copper smelter and an 8% decrease in SO2 emissions from the lead smelter. Emission levels are broadly in line with changes in production levels year-on-year.
Overall the Mount Isa copper smelter has decreased SO2 emissions by 400,985 tonnes per annum or 76% over the 2000 baseline level, following the installation of SO2 capture technology at the smelter. The SO2 is converted into sulphuric acid at the adjacent third-party managed acid plant. Xstrata Copper is targeting an increase from 80% to 95% capture and treatment of SO2 emissions from the copper smelter against the baseline established in 2000.
In 2006 our emission reduction programme included the start of progressive hood installations to the four copper smelter converters, and pressure balances to identify leaks in the ducting and ventilation system. These efforts have contributed significantly to reducing fugitive emissions of SO2 to the atmosphere. The programme has produced improved coordination between the acid plant and copper smelter, as well as enhanced process control and acid plant efficiency.
The lead smelter at Mount Isa has achieved a reduction of 23,279 tonnes per annum (18%) in SO2 emissions since 2000. In 2006, a new cooling water system was installed to allow improved process control in the furnace. Improvements to the quality of feeds for the lead smelter also further reduced emission levels, with improved coke quality during 2006 leading to improvements in the furnace performance and smelting reactions. A feasibility study is being undertaken to assess the viability of implementing Xstrata Technology’s ISASMELT technology at the zinc-lead smelter at Mount Isa, to achieve further reductions in emissions.
The former Falconbridge operations emitted a total of 130,700 tonnes of SO2 in 2006. The Altonorte smelter in Chile and the Sudbury Smelter in Canada are the most significant sources of sulphur dioxide emissions from the acquired operations.
An environmental upgrade project will commence at the Altonorte smelter in Chile in 2007 to improve performance. This will include the installation of a double-absorption contact process in the new acid plant, secondary hoods to catch fugitive gases and a dust-leaching plant to process stockpiled dust at the site as well as new dust resulting from continuing operations. Production of sulphuric acid will rise to 1.2 million tonnes a year from 775,000 tonnes, with emissions capture reaching 95% compared to 93.5% previously.
In 2006, Sudbury Smelter initiated an emissions dispersion modelling site assessment for ambient air and noise and is targeting further reductions in SO2 emissions to less than 25,000 tonnes per annum by 2015, a reduction of almost 40% over 2006 levels.
*acquired operations
Oxides of Nitrogen
Oxides of nitrogen (NOx) are by-products of burning fossil fuels, primarily in vehicles and generators with diesel fuelled engines and are emitted from the exhaust. Xstrata consumed 13.9 million tonnes of diesel in its operations in 2006, an increase of 1.6 million tonnes (12.7%) compared with 2005. Stack emissions of oxides of nitrogen remained at a similar level to the previous year at 1,193 tonnes comparedto 1,112 tonnes in 2005.
Xstrata Copper Kidd Creek mine in winter snow, Canada
Taking a dust sample at McArthur River Mine, Australia