Using Magnesium Calcium Alloy (MAG-CAL™) enables lead refineries to operate more efficiently and create a safe environment for workers. Our recommended debismuthizing process is based on the traditional Kroll-Betterton technique, employing our MAG-CAL alloy ingots.
The typical MAG-CAL mixture employs 70% magnesium and 30% calcium (70/30). By adding the ingot during the dibismuthizing process, refineries will save time and yield better results.
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The final stage of lead refining is typically the removal of bismuth by either electrolytic refining or by the Kroll-Betterton (KB) process. In the KB process, calcium and magnesium metals are added to molten lead in a continuous stream or in batches to react with bismuth. There are difficulties with this traditional process due primarily to the reactivity of calcium metal. At normal operating temperatures, calcium readily oxidizes, giving rise to bright flaring, excessive fume generation and an inherent loss of reagent. This translates directly into lower recoveries, reduced efficiency, higher processing costs, unpredictable final bismuth levels and environmental concerns.
Addition of MAG-CAL to the lead bath under agitation is the most effective and consistent technique. MAG-CAL is simply added to the vortex of the melt. A bath temperature of 480°C to 500°C (895°F – 930°F) produces complete dissolution of the alloy, with calcium recoveries of 90% or better.
Control of the process temperature is important for the successful addition of MAG-CAL. The process temperature ranges up to 520°C (970°F), however, the possibility of oxidation losses increases as process temperatures rise.
This technique eliminates the plunging cage and provides a homogeneous reaction environment. With MAG-CAL usage, bismuth levels as low as 0.003% have been achieved.
MAG-CAL is available in standard 10-kg (22 lb) ingot bundles, specially suited for vortex conditions. All THM magnesium/calcium products are packaged to meet IATA, UN and CTC regulations. A Material Safety Data Sheet accompanies each TH Magnesium shipment.