| Elemental mercury?Hg0?has attracted a great deal of concern due to its toxicity,volatility and bio-accumulation.It will leave bad effect on both human and the environment.The main source of Hg0 is coal combustion.China is the country that exploit and consume a large number of coal every year.It must commit itself to control the mercury pollution immediately.In 2015,China introduced the“Emission standard for Air Pollutants from Thermal Power Plants”that limits mercury and its compound emissions to 0.03 mg/m3.At present,the research on coal-fired mercury pollution control technology mainly focuses on three aspects:mercury removal before combustion,mercury removal during combustion and mercury removal after combustion,among which mercury removal technology after combustion is most prominent.Activated carbon injection?ACI?is considered to be the most important method for removing mercury from flue gas.However,the main problem with ACI is large consumption and low utilization rate,which will greatly increase costs.To develop a catalyst that possesses low cost and high mercury removal efficiency over a wide temperature range,biomass was pyrolyzed to get biomass carbon in this article.After activated by NH4Cl,Cl-BC carrier was obtained.Then CuO-ZrO2 was loaded onto the carrier by impregnation and Cu-Zrx/Cl-BC catalysts were prepared.The effects of catalyst components and loading value of metallic oxide on the mercury removal of the catalyst were investigated at 60-270oC.It was determined that Cu-Zr10/Cl-BC is the best catalyst for this research and its mercury removal efficiency can be achieved 98.87%at 120oC.Next,the effects of O2,NH3,SO2,H2O and stability experiments on Cu-Zr10/Cl-BC were investigated.O2 promotes the removal of mercury,especially at high temperatures,because it can generate lattice oxygen and participate in the mercury removal reaction.NH3,SO2,and H2O have a little inhibitory effect on the mercury removal of the catalyst,which mainly due to the competitive adsorption between them and Hg0.However,Cu-Zr10/Cl-BC exhibits strong stability and resistance to water and sulfur.In addition,it is concluded that the mercury removal of the catalyst mainly depends on the adsorption at low temperatures,and the oxidation will gradually increase at high temperatures.The catalysts were characterized by SEM-EDX,BET,XRD,H2-TPR,XPS and FT-IR.The characterization results indicated that the superior performance of Cu-Zr10/Cl-BC might be ascribed to lower crystallinity,stronger redox ability and better texture properties which resulted from the interaction of CuO and ZrO2.The mechanism for Hg0 removal over Cu-Zr10/Cl-BC was also proposed on the basis of above studies.The mercury removal mechanism is basically divided into three reaction lines,in which the activation of Cl and the change of Cu between two valence states CuO(Cu2+)?Cu2O?Cu+?are the key to mercury removal. |
PDF Full Text Request