海水湿法烟气脱硫曝气过程中汞、砷再释放特性实验研究

Experimental study on re-emission characteristics of mercury and arsenic in process of aeration of seawater wet flue gas desulfurization

海水湿法烟气脱硫装置排放的脱硫废水在曝气过程中,由于脱硫废水中存在部分还原性离子(SO_(3)^(2–)、Fe^(2+)、Mn^(2+)等),会将脱硫过程中捕集的汞、砷离子还原为气态汞和气态砷再次释放到大气中,降低湿法脱硫系统的汞、砷脱除效率。采用曝气反应器,通过模拟实际脱硫废水的曝气过程,重点考察了温度、Cl^(–)质量浓度、SO_(3)^(2–)浓度、SO_(4)^(2–)质量浓度及曝气流量对汞、砷再释放特性的影响。结果表明:随着温度的提高和曝气流量的增大,会加速汞、砷离子的还原,促进汞、砷的再释放;随着SO_(3)^(2–)浓度的提高,会显著抑制汞的再释放,但对砷的再释放影响较弱;汞、砷的再释放率呈现先增大后减小的趋势;Cl^(–)和SO_(4)^(2–)可与溶液中的汞离子形成性质稳定的络合物,也可与砷离子以更稳定的化合态相结合,从而有效抑制汞、砷的再释放,并且Cl^(–)的抑制作用比SO_(4)^(2–)更显著。

During the aeration process of the desulfurization wastewater discharged from the seawater wet flue gas desulfurization unit,some reducing ions(SO_(3)^(2-),Fe^(2+),Mn^(2+),etc.)are present in the desulfurization wastewater,which will reduce the mercury and arsenic ions captured during the desulfurization process to gaseous mercury and gaseous arsenic to be released to the atmosphere again,reducing the mercury and arsenic removal efficiency of the wet desulfurization system.An aeration reactor is used to simulate the actual aeration process of desulfurization wastewater,the effects of temperature,Cl^(-) concentration,SO_(3)^(2-)concentration,SO_(4)^(2-)concentration and aeration flow rate on the re-emission characteristics of mercury and arsenicare investigated in detail.The results show that,as the temperature and aeration flow increase,the reduction of mercury and arsenic ions will be accelerated,and the re-emission of mercury and arsenic will be promoted.The increase ofthe concentration of SO_(3)^(2-)will significantly promote the re-emission of mercury,but has a weak effect on re-emission of arsenic.The re-emission rate of mercury and arsenic shows a trend of first increasing and then decreasing.Cl^(-) and SO_(4)^(2-)can form stable complexes with mercury ions in the solution,and can also be combined with arsenic ions in a more stable chemical state,thereby effectively inhibiting the re-emission of mercury and arsenic,and the inhibitory effect of Cl^(-) is more significant than SO_(4)^(2-).