PbSO₄ reaction mechanism in oxygen and reduction atmospheres during co-smelting process with primary lead material

At present, lead-containing wastes have increasingly become the raw materials together with primary lead concentrate for lead production to meet the ever-increasing lead demand market. PbSO₄ is the dominant component in the lead-containing wastes, nevertheless, its reaction behavior during lead smelting is not sufficiently investigated. This study investigated PbSO₄ decomposition behaviors and phase transformation mechanisms at oxidizing and reductive atmospheres and various gas flow rates. The investigations reveal that increasing the temperature and decreasing the oxygen partial pressure of the decomposition atmosphere can accelerate PbSO₄ decomposition degree. PbSO₄ decomposition intensity under different atmospheres follows the order of reducing atmosphere > inert atmosphere > oxidizing atmosphere. PbSO₄ decomposition path was identified: at a non-reductive atmosphere, the decomposition of PbSO₄ belongs to a multi-step decomposition process, PbSO₄ gradually decompose into xPbO·PbSO₄ (x = 1, 2, 4 in turn) and finally PbO. At a reductive atmosphere, the multi-step decomposition process was accelerated significantly, at the same time, the reduction decomposition path PbSO₄ → PbS was increasingly dominant with the extension of decomposition time. PbS and Pb were generated successively. Therefore, a suitable reducing atmosphere is suggested to co-smelt PbSO₄-bearing wastes in primary lead smelting furnace.