Sulfur injection to remove copper from recycled lead

This work is focussed on lead decopperising by two techniques: conventional top addition of sulfur and injection of sulfur powder. It is found that the first method proceeds under equilibrium conditions and the second one depends on kinetic considerations. Experiments were carried out using 15 kg lead baths at two temperatures, 340 and 380°C. The carrying gas used for the injection trials was nitrogen with flow rates of 6.3 and 18.6 L min^-1. The results show that the decopperising process is more efficient at temperatures close to the melting point of lead for the sulfur top addition process whereas high temperatures produce better copper removal for the injection of sulfur powder. Sulfur injection with the higher nitrogen flow rate (18.6 L min^-1) produced higher decopperising rates. Thermodynamic and kinetic models are used to simulate this lead refining process.