硫酸钠在亚熔盐介质中的过饱和性

Supersaturation of sodium sulfate in sub-molten salt

采用激光浊度法对亚熔盐法粉煤灰提铝清洁工艺中硫酸钠在亚熔盐介质中的过饱和性进行了研究。结果表明:对亚熔盐介质进行真空蒸发时,其中的硫酸钠达到平衡浓度时即从体系中结晶析出,表明硫酸钠在亚熔盐介质中几乎无过饱和性。此外,杂质二氧化硅与碳酸钠对硫酸钠在铝酸钠溶液中的过饱和性具有一定影响,二氧化硅杂质会使硫酸钠析晶点碱浓度提高到20 g/L左右;碳酸钠会使硫酸钠析晶点碱浓度降低至15 g/L左右。同时,对析出晶体的物相分析表明:杂质二氧化硅的存在会使析出晶体向钠硅渣转变,而杂质碳酸钠的存在会使析出晶体向碳钠矾复盐转变。

The supersaturation of sodium sulfate in sub-molten salt during the process of extracting alumina from fly ash by sub-molten method was investigated by laser-turbidity method. The results show that during the process of vaporization, when the concentration of sodium sulfate in sub-molten salt exceeds the limit of solubility, it will be deposited out in solid form. There is not an obvious supersaturation phenomenon for the sodium sulfate in vaporization process. The impurities of silica and sodium carbonate have certain influences on the supersaturation of sodium sulfate in sub-molten salt. The silicon impurity increases the crystallization alkali concentration of sodium sulfate by 20 g/L. On the other hand, the sodium carbonate decreases the crystallization alkali concentration of sodium sulfate by 15 g/L. Meanwhile, the results of X ray diffraction analyses indicates that the SiO2 changes the crystal from crystalline precipitated to sodium-silicon residue,while the addition of Na2CO3 changes crystals to the burkeite.