基于Aspen Plus模拟湿法FGD对脱汞效率的影响

Study on the Removing Hg Performance of Wet Flue Gas Desulfurization System by Aspen Plus

烟气中的汞分为单质汞(Hg^0)、氧化态汞(Hg^(2+))和颗粒态汞(Hg_p)三种形态,其中Hg_p可以被除尘装置捕集,Hg^(2+)易溶于水,易被湿法脱硫装置(WFGD)吸收,而Hg^0很难用常规方法有效脱除,是烟气中汞污染控制的难点。湿法脱硫系统捕集下来的Hg^(2+)会被浆液中的SO_3^(2-)还原生成Hg^0,导致WFGD脱汞效率下降。通过Aspen Plus模拟了WFGD的工艺流程,并建立了Hg-S-Cl体系的反应动力学模型,以此分析温度、SO2浓度、氯离子浓度和pH等参数对WFGD脱汞性能的影响。

Mercury in the flue gas occurs primarily in three forms： elemental （Hg0）, oxi- dized mercury （Hg2＋ ） and particle bound mercury （Hgp） , Hgp can be easily captured by par- ticulate matter control devices （PMCDs）. Wet flue gas desulfurization （WFGD） can remove most of Hg2＋ due to its water-soluble property. However, parts of Hg2＋ would be reduced to Hg0by sulfite in desulfurization process, increasing the re-emission of mercury, which de- crease the removing mercury efficiency of WFGD. The simulation process of WFGD is estab- lished through the Aspen plus software, and a chemical kinetics model has been developed to describe the aqueous mercury sulfite-chloride-thiosulfate system and takes into account the simultaneous occurrence of a number of reaction steps. This work predicts the effects of tem- perature, reactant concentrations, pH, chloride, and thiosulfate on the rates of these reac- tions, and thus on the re-emission of Hg from WFGD systems.