Concept for the Reduction of SF6 Emissions in Magnesium Foundries

The “concept for the reduction of SF6 emissions in magnesium foundries” from Solvay Fluor und Derivates is a possibility for magnesium foundries to be included in the SF6 ReUse Concept. It describes the efforts that have to be taken to switch to sulphur dioxide (SO2), but how to keep the door open for continuous operating with SF6. This four-step process allows the magnesium foundry to decide on a fundamental database what will be their “tailor made” solution for reducing the SF6 emissions. These four steps are: determining the leaks and the quantities; installations of adequate gas suction systems; installation of an SF6 recovering system including filters for decomposition products; and giving the concentrated exhausted gases back to Solvay Fluor und Derivate. Solvay Fluor und Derivate will decide if the gas quality can be reclaimed or has to be destroyed through incineration. Introduction Solvay Fluor started producing SF6 in the 1960s and has since become a leading global supplier. Already at the beginning of 1990, Solvay developed the ReUse Concept for SF6; this was primarily designed for products coming from electrical equipment, where most of the worldwide SF6 production is used. In the years since then, the ReUse Concept has been widely adopted by the industry and is today an established procedure for minimising SF6 emissions from electrical equipment. Solvay has now developed a concept to include the magnesium industry in this already existing SF6 ReUse procedure and is currently introducing it to magnesium producers. A less favourable characteristic of SF6 is namely a comparatively high global warming potential due to its persistence in the atmosphere. There is e.g. for magnesium cross car beam production, which is mainly induced by SF6 and, to a smaller extent by CO2 emissions from the magnesium alloy production; it is not possible to reach a break even within a reasonable mileage of less than 200.000 km. Without SF6 emissions, as a further result of improved magnesium production and processing, the break even would then be in the range of 67.000 km to 109.000 km, depending on the fuel-saving factor [1]. This makes it essential to keep SF6 in closed cycles as far as possible in order to minimise emissions by utilising recycling and reuse potential. Concept To Reduce SF6 Emissions There is a big difference in the application of SF6 used in electrical equipment and magnesium foundries. In electrical equipment, pure SF6 concentrations are used compared to 0,04 vol% to 0,4 vol.% SF6 in the magnesium industry [2]. These low concentrations make it obligatory to concentrate the SF6 first and transport these gas mixtures from foundries to reclaiming companies afterwards.