Research On Mercury Removal Characteristics Of Flue Gas Based On MoS₂ Modified Graphene

The high-efficiency and low-cost solid sorbent mercury removal technology is a hotspot in the field of mercury pollutant control in coal-fired power plants,now.As a pro-mercury element,sulfur itself has a high mercury removal activity,and its transition metal compound has a certain catalytic oxidation effect on mercury.Graphene materials have excellent photoelectrochemical properties and have always played an important role in the field of catalysis.Therefore,exploring the synergistic effect of metal sulfides and graphene materials to the catalytic oxidation characteristics of mercury removal has practical value and theoretical significance.In this paper,the experimental study on the mercury removal characteristics of transition metal sulfide MoS2 modified graphene materials was carried out,and the influence of preparation and flue gas conditions on the mercury removal performance of sorbents was explored,which provided a theoretical basis and guidance for the promotion and applications of mercury removal.The nano MoS2 microspheres were compounded onto industrial multilayer graphene via hydrothermal synthesis.Various characterization methods,such as BET,SEM-EDS,XRD,Raman and XPS were used to investigate the physical and chemical properties of the sorbent.The research shows that:The hydrothermal synthesis was used to reduce the size of MoS2 microsphere from micron to nano,which promoted the dispersion of MoS2 crystal,at the same time,increased the sulfur-molybdenum ratio of MoS2;The main diffraction fronts of the MoS2 microspheres prepared by hydrothermal synthesis method are all open,which refers to the MoS2 with hexagonal crystal system,indicating that the MoS2 with pure phase has been prepared by hydrothermal synthesis method;With the hydrothermal and high-temperature treatment,the surface defect structure of graphene materials will increase,and a certain amount of oxygen-containing functional groups will be generated,which is conducive to the improvement of the adsorbent’s mercury removal efficiency.The influence of preparation temperature of sorbent,addition amount of ionic liquid,load capacity of MoS2 and original sample comparison on the performance of adsorbent was studied.The research results show that:The mercury removal efficiency of sorbents prepared by means of chemical loading is much higher than that of sorbents prepared by means of physical loading.The rise of the preparation temperature,which is beneficial to the formation of MoS2 microspheres,can improve the mercury removal efficiency of the sorbents and the best preparation temperature is 240℃.The ionic liquid as the reaction nucleus of MoS2 microspheres,promote the reaction of molybdenum source and sulfur source in the solution,and improve the yield of MoS2 microspheres.With the increase of MoS2 load,the mercury removal efficiency of the sorbent increases firstly and then decreases.When the MoS2 load is too large,it will lead to the agglomeration growth of the MoS2 microsphere,reduce its dispersion line and make the adsorption effect worse.The effects of reaction temperature,initial mercury concentration,O2 concentration,SO2 concentration and NOx concentration on the mercury removal efficiency of sorbent were studied via using the simulated flue gas fixed bed reaction system.The results show that:With the increase of fixed bed reaction temperature,sorbent of mercury efficiency increased firstly and then decreased.The optimum reaction temperature is 90℃;As the initial mercury concentration increases,the removal efficiency of the sorbent decreases,but the adsorption amount per unit time of the sorbent increases;When the GHSV was 1×105 h-1,the mercury removal efficiency of the sorbent adsorbed for 60min was 97%.With the increase of the air speed the gas processing capacity of the sorbent decreased;The presence of O2 can promote the adsorption effect of the sorbent,but the promotion effect is limited.When the concentration of O2 exceeds 6%,the gain effect of the sorbent reaches saturation.The SO2 has a certain inhibitory effect on the mercury removal efficiency.The SO2 molecules are clustered around MoS2 molecules,which hinders the contact between mercury atoms and MoS2 molecules.The presence of NOx also slightly inhibited the mercury removal effect of the sorbent.According to the experimental data,four kinetic models were used to fit the adsorption process of the sorbent and explore the adsorption mechanism of the sorbent.The results showed that:The adsorption of elemental mercury on the adsorbent surface was dominated by chemical adsorption;The adsorption rate of the sorbent on mercury atoms in the gas phase is mainly affected by the external film mass transfer rate;The adsorption process of sorbent on elemental mercury follows Temkin isothermal equation.