Thermal decomposition reaction and kinetic analysis of ammonium jarosite residues
To meet the demand of process stability control in side-blowing smelting for treating ammonium jarosite residues,the thermal decomposition and kinetic characteristics of the ammonium jarosites were investigated by means of TG-DSC-MS combined with XRD and SEM-EDS analysis.The results show that the main phases discovered in the researched slag are those of ammonium jarosite(NH4)Fe3(SO4)2(OH)6,spinel(Zn,Fe)Fe2O4,sulfates of PbSO4 and CaSO4(H2O)2.During thermal decomposition,the dehydroxylation and deamination reaction occur at about 380℃,resulting in various sulfates,the mechanism function of the dehydroxylation-deamination reaction is the decelerating α-t curve.In addition,the decomposition of Fe2(SO4)3 occurs at about 610℃,with a corresponding activation energy of 153.07 kJ/mol,which means strengthening the diffusion of gaseous product may contribute to the reaction.And the decomposition of PbSO4 occurs at about 1080℃with a high activation energy of 555.90 kJ/mol,whose reaction kinetic mechanism follows the three-dimensional diffusion.The main limiting factor of PbSO4 decomposition depends upon the diffusion of PbO product in the slag,which can be promoted by reducing the melting temperature and viscosity of the slag system.
jarosite residuethermal decompositionreaction mechanismkinetic characteristicsapparent activation energy
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