A Research on Energy-Saving and Environmental Impacts of Primary Magnesium and Magnesium Alloy Production in China

Abstract

China is the largest primary magnesium producer in the world, because of nearly 80% of the global market share. In the present paper, an approach of life cycle assessment (LCA) was applied to build an inventory of air emissions and to analyze the environmental impact of the global warming potential (GWP) and the acidification potential (AP) related to the production of AZ91D magnesium alloy. A summary of environmental impacts of primary magnesium and primary aluminum production with various studies was made to show the influence of uncertainties on the impacts. The results showed that the cumulative GWP and the acidification potential (AP) of AZ91D Mg-alloy are 33.4 t CO2eq/t ingot and 139 kg SO2eq/t ingot, with the range of 29.5-36.3 t CO2eq/t ingot and 104-152 kg SO2eq/t ingot, respectively. The GWP and AP of primary magnesium account for 90% and 77% of the cumulative environmental impact of AZ91D Mg-alloy. Under the grand background of advancing the development strategy of energy-saving and emission-reducing, China magnesium smelting and manufacture industry has made rapid progress in the structure optimization, energy efficiency improvement, and environment protection. The calculated data show that the improvement measures, e.g. reduction of dolomite consumption and energy consumption, in Chinese Pidgeon process led to 23% decrease of the GWP for the primary magnesium production in 2009 compared with 2005. The global warming reduction potential for 1 ton AZ91D alloy ingots produced in China was estimated of substituting HFC-134a for SF6as a cover gas.