LF脱硫废渣水热浸出多组分溶解行为

Dissolution of multicomponents during hydrothermal leaching of LF desulfurization slag

针对LF脱硫废渣浸出过程多组分溶解平衡问题,热力学计算并绘制浸出体系多组分溶解平衡曲线,考察废渣中Ca、Al、S等主要组分溶解平衡间的相互作用及对浸出去硫的影响,同时进行废渣浸出试验并分析浸出环境pH及浸出液中主要组分浓度变化。结果表明：CaS（s）易溶解,pH〉11.4时CaS（s）会溶解生成Ca（OH）2（s）,理论上浸出去硫可行。CaSO4（s）溶解度小于CaS（s）且难溶解,废渣被氧化而不利于硫的浸出,但控制pH〉12.3,CaSO4（s）会逐渐溶解转化为Ca（OH）2（s）;Al2（SO4）3（s）易溶解,体系中Al很难与浸出液中硫形成沉淀。浸出液pH随时间增加而上升并稳定在12左右,浸出液Ca含量很高而Al含量很低,S含量呈上升趋势,废渣中Al含量对硫的浸出影响不大,水热法浸出去硫具有较好的效果。

In light of the multicomponent dissolution equilibrium during the hydrothermal leaching of LF desulfurization slag,thermodynamic calculations were made and the dissolution equilibrium curves of calcium,aluminum and sulfur were plotted to analyze the interactions between these components and their influence on sulfur leaching. Furthermore,slag leaching experiments were conducted to investigate variation of pH and concentration of major components in the leaching solution. The results show that CaS（s） is easily soluble in water,and when pH 11.4,CaS（ s） dissolves to form Ca（OH）_2（ s）. Use of hydrothermal leaching for sulfur removal from LF desulfurization slag is theoretically feasible. CaSO_4（ s） is difficult to dissolve and its solubility is always lower than that of CaS（ s）; therefore,slag oxidation affects negatively sulfur leaching. However,when the p H of the leaching environment is controlled to be above 12. 3,CaSO_4（ s） is gradually transformed into Ca（OH）_2（s）. Al_2（SO_4）_3（ s） is easily soluble,and it is unlikely that Al will react with sulfur in the solution to form a precipitate. The p H of the leaching solution rises with time and remains at about 12. Calcium concentration in the leaching solution is high,while Al concentration is low. Sulfur concentration in the solution increases with time,and Al in the slag has little effect on sulfur leaching. It is thus concluded that hydrothermal leaching is effective in removing sulfur from LF desulfurization slag.