Study On Removal Characteristics Of Mercury Of SCR Catalyst And Biomass Ash In Coal-fired Flue Gas

In recent years, concerns about mercury emission and its control in coal-fired flue gas haverisen greatly because of extreme toxicity, persistence, and bioaccumulation of methyl mercurytransformed from emitted mercury. The primary objective of mercury abatement in coal-firedpower plants is to remove elemental mercury.With coal-fired power plant equipped with flue gasdesulphurization gradual (FGD), selective catalytic reduction (SCR) DeNOx system, bag filtersystem (FF), the use of SCR catalysts to remove elemental mercury has become a verycompetitive mercury emission control method. Sorbent injection is another major commerciallyavailable technologies for mercury control from coal-fired power plants. These two methodsapplied to coal-fired flue gas mercury control, the material (catalyst/sorbent) plays a decisive role.Based on the very promising SCR catalyst and novel biomass ash, this paper exploratory study theeffect and mechanism of Hg0pollutants removal from flue gas of,the main results are as follows.We investigated commercial SCR catalyst oxidation and properties of Hg0removal throughfixed bed mercury removal system experiments, emphasis on the effect factors of reactiontemperature, reaction time, and other flue gas constituents on the mercury removal performance ofSCR catalyst. Nitrogen adsorption analyzer (BET) analys is, X-ray diffraction (XRD), X-rayphotoelectron spectroscopy (XPS) and other testing methods were used to characterize SCRcatalysts and to preliminary explore the mechanism of SCR catalyst mercury removal reactions.The result showed that business SCR catalyst had a BET specific surface for44.7m2/g, a totalpore volume for0.182cc/g, an average pore diameter for16.3nm. The pores in SCR catalyst weremainly mesoporous, the pore size distribution most concentrates in18nm. The TiO2was in theform of anatase crystal. The main atom types were C1s, O1s, Si2p3, Ti2p3, V2p3. Under pureN2phenomenon,75%Hg0oxidation was achieved65min after the start of the reaction at100°C, and the time at200°C is35min. At100°C, the catalyst ‘s oxidation activity increased from40.46%to87%as NO concentration increased up to200ppm. At200°C, the catalyst ‘s oxidation activityincreased from34.07%to63.51%as NO concentration increased up to200ppm. With thepresence of300ppm NO, the catalyst ‘s oxidation activity decreased from83.22%to42.13%asHCl concentration increased up to50ppm at100°C, also decreased from76.59%%to32.01%asHCl concentration increased up to50ppm at200°C. With the presence of300ppm NO, thecatalyst ‘s oxidation activity decreased from83.22%to19.83%as SO2concentration increased upto400ppm at100°C, also decreased from76.59%%to2.75%as HCl concentration increased upto400ppm at200°C. At the presence of4%O2in flue gas, the mercury oxidation efficiency ofthe SCR catalyst increased up to95%, and the Hg0removal efficiency under several simulated realflue gas conditions also can reach more than95%.We investigated the Hg0adsorption of biomass ash through fixed bed mercury removalsystem experiments, emphasis on the effect factors of reaction temperature, reaction time, andother flue gas constituents on the Hg0removal performance of biomass ash. Nitrogen adsorptionanalyzer (BET) analys is, X-ray photoelectron spectroscopy (XPS) and other testing methods towere used to characterize biomass ash and preliminary explore the mechanism of biomass ashmercury removal reactions. The results showed that Wood ash (WA) and New ash (SP) had largerBET specific surface area for121.4m2/g and125.8m2/g, respectively. After brominated or sulfurimpregnation, the BET specific surface area decreased, the BET specific surface area forBrominated wood ash was only20.9m2/g. The average pore diameter of brominated new ash was11.6nm, and other5samples were all about6nm.There were mesoporous structure in the6samples, the mesoporous in the Wood ash is similar to the slit pores generated by the lamellarstructure, and the mesoporous in the New ash is considered as the slit hole formed by the lamellarparticles.The main atomic type in biomass ashes were C1s, O1s, Ca2p3, Mg2p, Si2p3. At100°C, the penetration rate of SP and WA reached80%after the adsorption of about25min.. LowBromine Wood Ash on Sulfur (D2SRA2) after the start of the adsorption in10min reached85%penetration, then the penetration rate has remained stable; Brominated Wood Ash (BA10B) at15min after the start of the adsorption reached75%penetration, then the penetration rate hasremained stable; Wood Ash reached80%penetration in25min adsorption, subsequent thepenetration rate has remained stable; the penetration rate Sulfur on wood ash SRA reached97% penetration in the adsorption100min, then keep reached stable for a long time. After theadsorption of30min, the penetration rate of SP was78%, and the penetration rate of Brominatednew ash (SP10) was68%. At200°C, the penetration rate of SP was lower than the penetration rateof WA at80%when adsorbed the35min. The penetration rate of the BA10B reached the stabletime after the adsorption, and the penetration rate of the45min was78%. The penetration rate ofthe D2SRA2time to reach the stable after the adsorption started95min. the penetration rate is, thepenetration rate of SRA reach96%after105min adsorbed. At this time, the penetration rate was89%. After the adsorption of40min, the penetration rate of SP reached80%, while thepenetration rate was70%when SP10reached the stability. Under100°C, the adsorption capacityof WA, BA10B, SRA, D2SRA2, SP, SP10were10.03μg/g,3.70μg/g,23.86μg/g,37.1μg/g,13.96μg/g,16.76μg/g, respectively; Under200°C, the adsorption capacity of WA, BA10B, SRA,D2SRA2, SP, SP10were8.44μg/g,28.02μg/g,19.93μg/g,24.10μg/g,18.80μg/g,26.76μg/g,respectively. As the HCl concentration from0ppm to10ppm, the Hg0adsorption efficiency ofWA, BA10B, SRA, D2SRA2, SP, SP10were increased from41.3%,45.26%,49.22%,41.13%and25.98%and58.17%to58.34%,62.13%and61.96%,83.99%,80.37%and66.95%,respectively. The O2concentration flue gas increased from0to4%, and CO2concentrationincreased from0to12%, the Hg0adsorption efficiency of WA, BA10B, SRA, D2SRA2, SP, SP10were changed from48.36%,44.57%and39.46%,41.13%,33.73%,43.37%to41.3%,45.26%,49.22%,41.13%and25.98%and58.17%, respectively. After adding400ppm SO2into the fluegas, the adsorption efficiency of the biomass ash adsorbent on the Hg0was not significantlychanged.300ppm NO added to the flue gas cause the Hg0adsorption efficiency of WA, BA10B,SRA, D2SRA2, SP, SP10change from51.1%,5.886,44.57%,47.67%,53.35,57.48%to48.36%,44.57%,39.46%,41.13%,33.73%,43.37%.