SO_2、NO对汞在湿法电除尘器中脱除的影响
|
摘要
湿法电除尘器(WESP)作为一种控制烟气中超细颗粒物的有效手段被应用于燃煤电厂的超低排放改造中,然而烟气中的Hg~0受电场、水膜、烟气组分等因素的影响在WESP中的协同脱除机理尚不明确。为了深入了解该机理,探讨了WESP电场和水膜对Hg~0的控制机理,并进一步研究了烟气中SO_2、NO对Hg~0在WESP中脱除的影响。结果表明:电场静电作用对烟气中Hg~0脱除贡献较小,O_2电离产物?O对Hg~0的氧化作用是O_2促进Hg~0脱除的主要途径,水蒸气通过电离产生?OH促进Hg~0氧化以及通过黏附作用促进Hg~0脱除;水膜的裹挟作用对WESP系统Hg~0的脱除贡献较小,溶于水中的汞不稳定且容易再释放;SO_2、NO均通过在电场中电离产生?O促进Hg~0氧化脱除,其中,SO_2及其电离产物溶于水膜后可以与Hg~(2+)形成稳定配合物抑制汞的再释放,而NO的电离产物在水膜中对汞再释放的抑制作用较小。
As an effective measure of control ultrafine particles of flue gas, wet electrostatic precipitator(WESP) is applied to ultra-low emission modification of coal-fired power plant. However, the effects of electricfield, water film and gas components on mercury in flue gas, and its synergistic mechanism in WESP, stillremain unclear. Thus, the control mechanisms of WESP electric field and water film on Hg~0 were investigated,and the effects of SO_2 and NO on mercury removal by WESP were also assessed. The results indicated thatelectrostatic had a slight effect on Hg~0 removal, while Hg~0 oxidation with ·O, a type of product from O_2 ionizationin electric field, was the main route for O_2 promoting Hg~0 removal. Water vapor could promote Hg~0 removal byadhesion effect and generating ·OH in electric field. The coerced effect of water film had a slight contribution tomercury removal and the mercury dissolved in water film was unstable and easy to release again. SO_2 and NOcould produce ·O by ionization and promote mercury oxidation removal, of which SO_2 and its ionization productsdissolved in water film and could form mercury stable complexes, which could inhibit re-emission of mercury,while NO ionization products dissolved in water film had slight effect on such inhibiting effect. This studypresent the synergistic mechanism of mercury removal influenced by SO_2 and NO in WESP.
As an effective measure of control ultrafine particles of flue gas, wet electrostatic precipitator(WESP) is applied to ultra-low emission modification of coal-fired power plant. However, the effects of electricfield, water film and gas components on mercury in flue gas, and its synergistic mechanism in WESP, stillremain unclear. Thus, the control mechanisms of WESP electric field and water film on Hg~0 were investigated,and the effects of SO_2 and NO on mercury removal by WESP were also assessed. The results indicated thatelectrostatic had a slight effect on Hg~0 removal, while Hg~0 oxidation with ·O, a type of product from O_2 ionizationin electric field, was the main route for O_2 promoting Hg~0 removal. Water vapor could promote Hg~0 removal byadhesion effect and generating ·OH in electric field. The coerced effect of water film had a slight contribution tomercury removal and the mercury dissolved in water film was unstable and easy to release again. SO_2 and NOcould produce ·O by ionization and promote mercury oxidation removal, of which SO_2 and its ionization productsdissolved in water film and could form mercury stable complexes, which could inhibit re-emission of mercury,while NO ionization products dissolved in water film had slight effect on such inhibiting effect. This studypresent the synergistic mechanism of mercury removal influenced by SO_2 and NO in WESP.
引文
[1] HUANG Y, HAN P, GUO X, et al. Experimental study on the stability of the mercuric complexes in wet flue gas desulfurization wastewater[C]//Springer Singapore. Clean Coal Technology and Sustainable Development. Singapore, 2016:467-473.
[2] WO J, ZHANG M, CHENG X, et al. Hg2+reduction and re-emission from simulated wet flue gas desulfurization liquors[J].Journal of Hazardous Materials, 2009, 172(2/3):1106-1110.
[3] LIU Y, ADEWUYI Y G. A review on removal of elemental mercury from flue gas using advanced oxidation process:Chemistry and process[J]. Chemical Engineering Research and Design, 2016, 112:199-250.
[4] RODRíGUEZ-PéREZ J, LóPEZ-ANTóN M A, DíAZ-SOMOANO M, et al. Regenerable sorbents for mercury capture in simulated coal combustion flue gas[J]. Journal of Hazardous Materials, 2013, 260(Complete):869-877.
[5] ZHAO S, DUAN Y, YAO T, et al. Study on the mercury emission and transformation in an ultra-low emission coal-fired power plant[J]. Fuel, 2017, 199:653-661.
[6] BAYLESS D J, SHI L, KREMER G, et al. Membrane-based wet electrostatic precipitation[J]. Journal of the Air&Waste Management Association, 2005, 55(6):784-791.
[7] JING H, WANG X, WANG W, et al. Elemental mercury oxidation in an electrostatic precipitator enhanced with in situ soft X-ray irradiation[J]. Journal of the Air&Waste Management Association, 2015, 65(4):455-465.
[8] NIU Q, LUO J, SUN S, et al. Effects of flue gas components on the oxidation of gaseous Hg0by dielectric barrier discharge plasma[J]. Fuel, 2015, 150:619-624.
[9] HUANG Y, YIN Z, CHEN Y, et al. Experimental study on gaseous elemental mercury removal by wet electrostatic precipitators[J]. Fuel, 2018, 234:1337-1345.
[10] BHASAVANICH D, ASHBY S, DEENEY C, et al. Flue gas irradiation using pulsed corona and pulsed electron beam technology[C]//Institute of Electrical and Electronics Engineers. Ninth IEEE International Pulsed Power Conference.Albuquerque, 1993:441-450.
[11]吴彦,占部武生.脉冲放电法消除汞蒸气的实验研究[J].环境科学学报, 1996, 16(2):221-225.
[12] CALVERT J, LINDBERG S. Mechanisms of mercury removal by O and OH in the atmosphere[J]. Atmospheric Environment,2005, 39(18):3355-3367.
[13] CHANG M B, BALBACH J H, ROOD M J, et al. Removal of SO2from gas streams using a dielectric barrier discharge and combined plasma photolysis[J]. Journal of Applied Physics, 1991, 69(8):4409-4417.
[14] BLYTHE G M, CURRIE J, DEBERRY D. Bench-scale kinetics study of mercury reactions in FGD liquors[R/OL].[2018-11-20]. https://www.osti.gov/scitech/servlets/purl/950472/.
[15] KOSSYI I A. Kinetic scheme of the non-equilibrium discharge in nitrogen-oxygen mixtures[J]. Plasma Sources, Science and Technology, 1992, 1(3):207-220.
[16] OCHOA-GONZáLEZ R, DíAZ-SOMOANO M, MARTíNEZ-TARAZONA M R. Effect of anion concentrations on Hg2+reduction from simulated desulphurization aqueous solutions[J]. Chemical Engineering Journal, 2013, 214(4):165-171.
[2] WO J, ZHANG M, CHENG X, et al. Hg2+reduction and re-emission from simulated wet flue gas desulfurization liquors[J].Journal of Hazardous Materials, 2009, 172(2/3):1106-1110.
[3] LIU Y, ADEWUYI Y G. A review on removal of elemental mercury from flue gas using advanced oxidation process:Chemistry and process[J]. Chemical Engineering Research and Design, 2016, 112:199-250.
[4] RODRíGUEZ-PéREZ J, LóPEZ-ANTóN M A, DíAZ-SOMOANO M, et al. Regenerable sorbents for mercury capture in simulated coal combustion flue gas[J]. Journal of Hazardous Materials, 2013, 260(Complete):869-877.
[5] ZHAO S, DUAN Y, YAO T, et al. Study on the mercury emission and transformation in an ultra-low emission coal-fired power plant[J]. Fuel, 2017, 199:653-661.
[6] BAYLESS D J, SHI L, KREMER G, et al. Membrane-based wet electrostatic precipitation[J]. Journal of the Air&Waste Management Association, 2005, 55(6):784-791.
[7] JING H, WANG X, WANG W, et al. Elemental mercury oxidation in an electrostatic precipitator enhanced with in situ soft X-ray irradiation[J]. Journal of the Air&Waste Management Association, 2015, 65(4):455-465.
[8] NIU Q, LUO J, SUN S, et al. Effects of flue gas components on the oxidation of gaseous Hg0by dielectric barrier discharge plasma[J]. Fuel, 2015, 150:619-624.
[9] HUANG Y, YIN Z, CHEN Y, et al. Experimental study on gaseous elemental mercury removal by wet electrostatic precipitators[J]. Fuel, 2018, 234:1337-1345.
[10] BHASAVANICH D, ASHBY S, DEENEY C, et al. Flue gas irradiation using pulsed corona and pulsed electron beam technology[C]//Institute of Electrical and Electronics Engineers. Ninth IEEE International Pulsed Power Conference.Albuquerque, 1993:441-450.
[11]吴彦,占部武生.脉冲放电法消除汞蒸气的实验研究[J].环境科学学报, 1996, 16(2):221-225.
[12] CALVERT J, LINDBERG S. Mechanisms of mercury removal by O and OH in the atmosphere[J]. Atmospheric Environment,2005, 39(18):3355-3367.
[13] CHANG M B, BALBACH J H, ROOD M J, et al. Removal of SO2from gas streams using a dielectric barrier discharge and combined plasma photolysis[J]. Journal of Applied Physics, 1991, 69(8):4409-4417.
[14] BLYTHE G M, CURRIE J, DEBERRY D. Bench-scale kinetics study of mercury reactions in FGD liquors[R/OL].[2018-11-20]. https://www.osti.gov/scitech/servlets/purl/950472/.
[15] KOSSYI I A. Kinetic scheme of the non-equilibrium discharge in nitrogen-oxygen mixtures[J]. Plasma Sources, Science and Technology, 1992, 1(3):207-220.
[16] OCHOA-GONZáLEZ R, DíAZ-SOMOANO M, MARTíNEZ-TARAZONA M R. Effect of anion concentrations on Hg2+reduction from simulated desulphurization aqueous solutions[J]. Chemical Engineering Journal, 2013, 214(4):165-171.