燃煤过程中不同烟气组分对汞形态转化的影响

Effect of various flue gas compositions on mercury speciation transformation during coal combustion

通过化学热力学平衡模拟,研究了在不同烟气温度下汞从元素态汞转化为二价汞的规律,并与小型实验结果进行了比较.数值模拟了不同的烟气组分如O2、HCl、NO、SO2对汞形态转化的影响.结果表明,O2、HCl有助于汞的转化,HCl的活性远远大于O2的活性;随着O2和HCl体积分数的增大,汞转化的起始温度和截止温度升高;SO2有助于汞的转化,尤其是在低温环境下,SO2的体积分数越大,汞的转化温度越高;NO对汞转化几乎不产生影响.利用二价汞易溶水的特点,通过将元素态汞转化为二价汞,可以利用湿法脱硫装置将其除去,从而实现汞排放的有效控制.

Mercury speciation has significant effect on mercury control in coal-fired flue gas. The chemical thermal equilibrium was used to investigate the transformation law of elemental mercury （Hg^0）, which was oxidized into divalent mercury （Hg^2＋） at different flue gas temperature, and the results were compared with the experimental results. The model＇s feasibility was demonstrated. Simulations were carried out to study the effects of different compositions, such as O2, HCl, NO and SO2 on the mercury transformation. Chemical thermal equilibrium simulation results show that O2 and HCl can greatly promote the mercury oxidization, and that HCl appears much more active than O2 during the mercury transformation. The start-temperature and end-temperature for mercury transformation are higher with increasing O2 and HCl fraction. SO2 is helpful for mercury transformation especially at lower temperature. Mercury is transformed into Hg^2＋ at much higher temperature with increasing SO2 fraction. NO has little impact on the mercury transformation. Due to the characteristic of water solubility of Hg^2＋ , Hg^2＋ is prone to be absorbed by the scrubber or wet flue gas desulfurization, so mercury can be controlled effectively.