Removal And Solidification Of Gaseous Arsenic By Metal Oxides From Flue Gas Under A Wide Temperature Range

Coal burning,metallurgy,waste incineration and other industrial processes will emit a large amount of arsenic containing flue gas,which is not only easy to cause"arsenic poisoning"in flue gas treatment facilities,but also pose a great threat to people’s health.In order to achieve the goal of carbon peaking and carbon neutrality,the flue gas from metallurgical and industrial boilers will need to be further treated.At the same time,the incineration treatment facilities for solid waste such as domestic waste will gradually increase,and the resulting arsenic containing flue gas also needs to be treated.At present,gaseous arsenic removal technology mainly includes two ways:collaborative removal by existing equipment and forced removal.With the increasingly strict emission standards of heavy metals in flue gas all over the world,it will be more and more difficult to meet the emission requirements simply by using the existing equipment for collaborative removal,at the same time,the gaseous arsenic removal is usually before the denitration unit（SCR）,and the flue gas has a high temperature,Therefore,it is necessary to develop forced removal technology with good selectivity and economy,which is suitable for high temperature environment.Metal oxides are cheap and easily available.They can adsorb and react with gaseous arsenic compounds at high temperature,and have potential adsorption and solidification ability for arsenic in flue gas.In addition,some metal oxides are also components of SCR catalyst.Therefore,a systematic study on the adsorption and removal of gaseous arsenic in flue gas by different metal oxides will have important theoretical value and practical significance for developing effective flue gas arsenic control technology,reducing"arsenic poisoning"of SCR catalyst,prolonging the service life of catalyst and reducing the secondary pollution of arsenic release from waste catalyst.In this research,a series of metal oxides were selected as studying object based on the SCR catalysts and fly ash,includingγ-Al₂O₃,CaO,Fe₂O₃,MgO,TiO₂,WO₃,MoO₃,V₂O₅,ZrO₂,CeO₂,Fe₃O₄,MnO₂,Cuo,ZnO,Mn-Fe binary metal oxides（Mn/Fe-O）.Through fixed bed adsorption experiments,the removal performance of different metal oxides for gaseous arsenic in flue gas was systematically studied under the conditions of N₂/O₂ atmosphere and simulated flue gas.Further,the toxicity characteristic leaching procedure（TCLP）was used to evaluate the solidification ability of metal oxides to arsenic and the environmental risk of release arsenic.The results demostrated that when the adsorption temperature was 600℃-900℃,CaO,γ-Al₂O₃,ZnO,MgO,CeO₂ and Mn/Fe-O binary metal oxides show strong removal and solidification ability for gaseous arsenic.Except CaO,all metal oxides displayed characteristic to resistant simulated flue gas.At 900℃,the leaching rate of arsenic in TCLP meets the standard（5 mg/L）in GB 5085.3-2007,except for Mn/Fe-O binary metal oxide.XRD and SEM characterization results show that the crystal structure and micro morphology of ZnO,MgO and CeO₂ change little after the adsorption experiment at 900℃for 30 minutes,indicating that the three metal oxides have excellent high temperature resistance.XPS characterization further showed that arsenic compounds mainly existed As（Ⅴ）on the surface of ZnO and MgO and As（Ⅲ）on the surface of CeO₂.