燃煤烟气污染物控制装置协同脱汞特性研究

采用Ontario Hydro方法对某100MW燃煤机组进行了烟气汞取样测试，获得了选择性催化还原（SCR）脱硝装置、静电除尘器（ESP）和湿法烟气脱硫装置（WFGD）对烟气汞形态转化和脱除特性规律.借助程序升温脱附（TPD）、扫描电子显微镜分析（SEM）和X射线荧光光谱分析（XRF）等方法探究了飞灰对汞的吸附特性及吸附后汞的热稳定性.结果表明，在75% MCR和85% MCR不同的机组负荷下，SCR+ESP+WFGD对烟气总汞（Hg^T）的联合脱除率分别为92.83%、81.66%.SCR对元素汞（Hg⁰）的氧化率与燃煤氯（Cl）含量正相关，Cl含量为500mg/kg时，氧化率高达96.18%.ESP在完全脱除颗粒汞（Hg^P）的同时对Hg⁰和氧化态汞（Hg²⁺）的平均脱除率分别为12.73%和27.79%，ESP飞灰中的未燃尽炭和金属氧化物（Al₂O₃、Fe₂O₃）是吸附气态汞的关键组分，汞在飞灰表面主要以HgCl₂、HgS（红色）和HgO的形态存在，高于190℃时会分解再释放.WFGD对Hg²⁺的平均脱除率为91.10%，并能将部分Hg²⁺还原成Hg⁰，存在明显的汞二次释放问题.

Characteristics of the existing air pollutant control devices on Hg synergistic removal in a coal-fired power plant

The Ontario Hydro Method (OHM) was applied to determine the mercury speciation and concentration in the flue gas emitted from a 100MW boiler system.Mercury speciation transformation and removal characteristics of selective catalytic reduction (SCR) system,electrostatic precipitators (ESP) and wet flue gas desulfurization (WFGD) had been obtained.Temperature programmed decomposition (TPD),Scanning electron microscope (SEM) and X ray fluorescence (XRF) were used to investigate the adsorption characteristic of mercury by fly ashes and thermal stability after adsorption.The results show that the overall mercury (Hg^T) removal efficiencies over SCR + ESP + WFGD combination were 92.83% and 81.66% under 75% MCR and 85% MCR,respectively.The oxidation of element mercury (Hg⁰) by SCR catalyst was greatly promoted by the chlorine (Cl) content in coal and 96.18% Hg⁰ was oxidized to oxidized mercury (Hg²⁺) by SCR when the Cl concentration in burned-coal contained 500mg/kg.Hg^P could be effectively removed by ESP,removal efficiencies with 12.73% of Hg⁰ and 27.79% of Hg²⁺ were observed.Unburned carbon and metal oxides (Al₂O₃,Fe₂O₃) were the main components of ESP fly ash to adsorb gaseous mercury.HgCl₂,HgS (red),and HgO were the main mercury compounds in the ash after adsorption which would decompose when the temperature reached 190 degrees.The average removal efficiencies of Hg²⁺ by WFGD were 91.10%.Meanwhile,the phenomenon of mercury re-emission due to part of Hg²⁺ was reduced to Hg⁰ in WFGD was found.