2-WAVELENGTH PYROMETRY STUDY OF THE COMBUSTION OF SULFIDE MINERALS .2. GALENA AND COMMERCIAL LEAD CONCENTRATES

The combustion of galena and two commercial lead concentrates has been investigated using a specially constructed fast-response, two-wavelen gth pyrometer. The changes in the particle morphology and in the chemi cal composition of the individual particles during combustion were als o investigated through scanning electron microscopy and energy dispers ive X-ray/wavelength dispersive X-ray (EDX/WDX) studies of quenched re action products. The effects of oxygen concentration and particle size on combustion were studied, together with the influence of chemical a nd morphological differences between the different lead concentrates. Increasing gas oxygen content from 10 to 100 pet elevated the particle combustion temperature from about 1600 to over 2000 K. The higher oxy gen content also resulted in a change of mechanism from relatively con stant combustion temperatures in air to much more rapid transient comb ustion pulses in pure oxygen. Thus, it is suggested that lead sulfide vaporization controls the reaction in both air and oxygen. Metallic le ad vaporization may also be important, because both sulfide and metall ic lead phases were identified in the quenched partially reacted parti cles. It is thought that the metallic lead in the particles is produce d through reaction between surface sulfates and unreacted lead sulfide s. The commercial concentrate feeds were found to consist mainly of ag glomerates of many smaller particles, with the chemical and mineral co mposition of the individual particles dictating their combustion behav ior. Increasing quantities of galena in the agglomerates enhance the v aporization reactions and limit reaction temperatures, whereas increas ing quantities of iron sulfides raise the intensity of reaction and co mbustion temperatures. Zinc sulfides act as a thermal load. Reaction m echanisms for both galena and commercial concentrate particles are pro posed.