铅银渣熔化-烟化过程中银物相演化规律的研究

Phase Evolution of Silver in Lead-Silver Slag During Melting-Fuming Process

针对铅银渣中银元素在熔化-烟化过程中物相演化规律开展研究。通过热力学计算分析,研究铅银渣中银物相挥发的热力学机制,并基于热力学理论,开展单因素实验,研究反应温度、配碳比和保温时间对银回收率的影响,得出最佳工艺参数。接着通过观察微观组织形貌,结合理论计算与实验结果,明确铅银渣中银物相在熔化-烟化过程中的演化规律。热力学分析结果表明,铅银渣中的Ag_(2)O会优先挥发到烟尘中;渣中的AgCl不发生氧化反应、还原反应和分解反应,会挥发到烟尘中;渣中的Ag_(2)S不挥发也不发生还原反应,会被氧化成Ag_(2)SO_(4);在低温时渣中的Ag_(2)SO_(4)会被还原为单质银,单质银与铅、锌形成合金被携带进入烟尘;在高温时,Ag_(2)SO_(4)的蒸气压急剧增大,会挥发到烟尘中。银扩大配渣实验结果表明,烟尘中物相为Ag_(2)O、AgCl、Ag_(2)SO_(4)和单质银,这与热力学分析结果一致。单因素实验表明,回收铅银渣中银的最佳工艺参数为反应温度1 300℃、配碳比16.30%、保温时间150 min;在此条件下,银回收率为80.26%。

The phase evolution of silver in lead-silver slag during melting-fuming process was studied.The thermodynamic mechanism of silver phase volatilization in lead-silver slag was analyzed by thermodynamic calculation and analysis.Based on the thermodynamic theory calculation,the influence of single factor(reaction temperature,carbon proportion and holding time) on silver recovery rate was studied,and the optimum process parameters were obtained.Then,by observing the microstructure morphology,combined with theoretical calculation and experimental results,the evolution law of silver phase in lead-silver slag during melting-fuming process was clarified.The thermodynamic analysis results show that Ag_(2O) in the lead-silver slag is preferentially volatilized into the soot.AgCl in the slag does not undergo oxidation reaction,reduction reaction and decomposition reaction,and will volatilize into the dust.Ag_(2S) in lead-silver slag does not volatilize or undergo reduction reaction,and will be oxidized to Ag_2SO_4.At low temperature,Ag_2SO_(4) will be reduced to elemental silver,and elemental silver will form an alloy with lead and zinc,which will be carried into the soot.At high temperatures,the vapor pressure of Ag_2SO_(4) increases sharply and Ag_2SO_(4) volatilizes into the dust.The experimental results of silver slag show that the phases in the dust are Ag_2O,AgCl,Ag_2SO_(4) and elemental silver,which is consistent with the results of thermodynamic analysis.The single factor experiment showed that the optimum process parameters for silver recovery from lead-silver slag were reaction temperature of 1 300 ℃,carbon proportion of 16.30%,holding time of 150 min.Under these conditions,the silver recovery rate was 80.26%.