液态高铅渣还原过程炉渣熔化温度的研究

Melting Point of Molten High-Lead Slag in Direct Reduction Process

以PbO-FeO-CaO-SiO2-ZnO为基本渣系,探讨了液态高铅渣和实际还原过程中,当Pb含量范围在2.5%～50.0%,ZnO含量范围在13%～6%时,渣组分变化对炉渣熔化性能的影响。利用热力学计算软件FactSage 6.2计算分析了该五元渣系的低熔点区域及特定组分的熔点,并结合半球法实验室测定结果对其进行了验证。研究表明,当w(FeO)/w(SiO2)在1.5～2.2,w(CaO)/w(SiO2)在0.4～1.0之间时,炉渣的熔点随FeO/SiO2比的增大而升高,同时随还原过程中Pb含量不断减少而升高;渣含Pb及ZnO量固定,w(FeO)/w(SiO2)在1.6～2.0范围内,w(CaO)从10%增加到22%时,炉渣的熔点随CaO含量增大而降低;渣中Pb含量从50%减小到2.5%,w(CaO)/w(SiO2)为0.35～0.54,w(FeO)/w(SiO2)为1.2～1.8时,炉渣熔点均低于1150℃;TG-DSC和XRD分析显示,1500℃时高铅渣、中铅渣和低铅渣失重率分别为38.69%,21.62%和3.95%。PbO的挥发导致高铅渣和中铅渣的大量失重,生成Fe3O4和Ca2SiO4等高熔点物相,这是导致FactSage理论计算熔点值与半球法实验熔化温度测定值之间存在-40～150℃偏差的主要原因。

Based on PbO-FeO-CaO-SiO2-ZnO slag in system, the influence of slag composition changes on slag melting performance for the molten high-lead slag direct reduction process were investigated, in the Pb content range of 2.5% to 50.0%, ZnO contentrange of 13% to 6%. To begin with, low melting point regions of the PbO-FeO-CaO-SiO2-ZnO five-component system were drawn and melting point values of some component slag were calculated using FactSage 6.2, which were verified by hemisphere method experimental results. It was shown that the melting point of the five-component slag, if w（ FeO）/w（ SiO2 ） ratio was defined between 1.5 and 2.2, w（ CaO）/w（ Si02 ） ratio between 0. 4 and 1. 0, increased with the increase of w（ FeO）/w（ SiO2 ） ratio and the decrease of the Pbcontent decreasing; in addition, the slag melting point dropped with the increase of w（CaO） from 10% to 22% when the w（ FeO）/ w （ SiO2 ） ratio were changed from 1.6 to 2. O, Pb and ZnO content in the slag fixed in certain value. Besides, the slag melting pointswere always lower than 1150 ℃ while w （CaO）/w （ SiO2 ） ratio were set between 0.35 and 0.54, w （FeO）/w （ SiO2 ） ratio between 1. 2 and 1.8, no matter what content of Pb was 50. 0% or 2.5%. Analysis of TG-DSC and XRD indicated that the weight loss rate ofhigh-lead slag, middle-lead slag and low-lead slag was 38.69% , 21.62% and 3.95% respectively at 1500 ℃. The volatility of PbO resulted in the weight loss of high-lead slag and middle-lead slag, producing Fe304 and CasSiO4 phase, which led to the deviation ofmelting temperature values of about -40 ℃ to 150 ℃ for calculated results by FactSage and experimental results subsequently.