湿法烟气脱硫系统中Hg0再释放特性及离子液体脱汞研究

Study on the characteristics of Hg0 re-emission and mercury removal by ionic liquid in WFGD systems

为进一步提高湿法烟气脱硫(WFGD)系统中的脱汞效率,对低浓度SO32-工况下Hg0再释放特性以及不同离子液体的脱汞性能进行了研究。基于鼓泡塔反应器,在N2气氛下研究了SO32-和金属离子(Fe2+,Fe3+和Cu2+)对WFGD系统中Hg0再释放特性的影响,同时考察了3种离子液体(HMIM[PF6],BMIM[PF6],BMIMCl)的脱汞性能,筛选出表现最佳的添加剂和其最优运行工况。结果表明,当脱硫液中SO32-浓度处于较低水平时,增加SO32-浓度可促进Hg2+的还原;而当SO32-过量时,Hg0再释放行为将被明显抑制。Fe2+,Fe3+和Cu2+等金属离子浓度的增加均能促进Hg0的再释放。上述3种离子液体添加剂抑制效果为BMIMCl>BMIM[PF6]>HMIM[PF6]。对脱汞性能较好的添加剂BMIMCl进行进一步试验,获得其抑制Hg0再释放的最佳工况,即添加质量浓度为10 g/L、较低脱硫液pH值以及50℃脱硫液温度。

To further improve the mercury removal efficiency of wet flue gas desulfurization(WFGD)systems,the characteristics of Hg0 re-emission and the mercury removal performances of different ionic liquids were studied at low SO32-concentrations.Based on a bubble reactor,the effects of SO32-and metal ions(Fe2+,Fe3+and Cu2+)on the characteristics of Hg0 re-emission in WFGD systems were investigated under N2 atmosphere.The mercury removal performances of three ionic liquid additives(HMIM[PF6],BMIM[PF6]and BMIMCl)were also studied,and the optimal operating conditions for the best-performing additives were obtained.The results indicate that increasing SO32-concentration at a relatively low level can intensify the reduction of Hg2+,whereas Hg0 re-emission is significantly inhibited with excess concentration of SO32-.It is also found that Fe2+,Fe3+and Cu2+can facilitate Hg0 re-emission.The three ionic liquid additives above show effective inhibitions on Hg0 re-emission in the order of BMIMCl>BMIM[PF6]>HMIM[PF6].Further experiments were carried out on BMIMCl to obtain its optimal condition for inhibiting Hg0 re-emission.The optimal condition for BMIMCl is at a mass concentration of 10 g/L,a lower pH value and a desulfurization liquid temperature at 50℃.