Advances in the refining and alloying of low-bismuth lead

A programme has been initiated to improve the performance and eliminate the environmental concerns of the traditional Kroll-Betterton process for bismuth removal from lead. The work has resulted in the development of a new generation of debismuthizing reagents that are comprised of a magnesium-calcium alloy, specially designated at Mag-Cal™. The most common Mag-Cal™ alloy contains 70 wt.% magnesium and 30 wt.% calcium. Extensive testing has revealed that addition of Mag-Cal™ to the vortex at approximately 480–500 °C, followed by mixing for 5–15 min, provides the best results. With Mag-Cal™, bismuth levels of 0.005 wt.% Bi, or less, are readily achieved without the need for supplemental calcium and antimony additions. Calcium-aluminum master alloys (known as CAL-AL™) have been developed which enable battery-grid manufacturers to achieve target calcium and aluminum specifications with consistently high and predictable recoveries. A new process has been developed for alloying calcium and aluminum into lead. The process has been proven in an extensive campaign of pilotscale trials. The process uses pure calcium and aluminum in the form of granules of particulates and offers many advantages that will be of significant benefit to lead-calcium alloy producers.