Partitioning And Migration Of Trace Elements In Coal Combustion Byproducts Of Certain Coal-Fired Power Plants In Hefei

China is the largest coal productor and comsumer aroung the world.The steam coal is mainly used to thermally generate the power in coal-fired power plants.Fossil fuels’ combustion,especially coals,is one main contributor to carbon emissions of China.Therefore,coal-fired power plants are important targets for the implementation of the carbon peaking and carbon neutrality strategy.With an output of clean electric power,coal-fired power plants also produce large mounts of coal combustion byproducts,i.e.,fly ash.Trace elements in coal migrate and redistribute during coal combustion,resulting in an accumulation of some harzardous elements on particle surface of coal combustion byproducts and posing a certain impact on both the environment and human health.However,some combustion byproducts are important potential resources.Certain critical strategic metals are enriched in byproducts and can be comprehensively extracted,examplifing by rare earth elements in fly ashes.Thus,a clean and comprehensive utilization of coal resources is one important way to achieve the goal of "dual carbon" currently.Anhui is the major coal-based energy supplier for the Yangtze River Delta Economic Zone in China.Hefei City,the provincial capital of Anhui,locating at the center of Anhui,is an important industrial city in this region.It is located in a subtropical monsoon humid climate region with a sensitive and vulenerable environment due to intensive human activities.It is of both scientific and practical significance to investigate the distribution and migration of trace elements in the byproducts from coal-fired power plants in this region.It provides a scientific basis for the regional geochemical cycle of trace elements and the scientific data for the environmental assessment of hazardous substances from coal-fired power plants.To investigate the partitioning and distribution of trace elements in coal combustion byproducts from two coal-fired power plants,to analyze potential environmental impacts of harmful substances,and to evaluate the recovery potential of REY from coal combustion by-products,a total of 28 samples,including feed coal,slag,limestone,FGD gypsum,and ashes of different partied size from the WN and TY coal-fired power plants were collected.Proximate analyses,particle size measurement,and determination of trace elements by ICP-MS were conducted to characterize trace elements in feed coal and coal byproducts,to discuss the migration of trace elements during coal combustion,to study the influence of particle size,flue gas desulfurization,coal ash deposition and storage on the distribution and migration of trace elements,and to evaluate the recovery potential of REY from coal combustion byproducts.Results indicate that(1)ash yields of feed coals from the WN and TY power plants were 12.46% and 12.23%,respectively.The averaging volatile matter of feed coal were36.38% and 31.52%,respectively,indicating a high volatile bituminous coal rank.The total sulfur contents of these two feed coals were 0.61% and 0.57%,respectively.(2)Compared to common Chinese coals,V,Cr,Se,In,Sb,and Pb in the feed coals were slightly enriched in the feed raw coal of WN power plant,while V,Cr,Ga,and Se were slightly enriched in the raw feed coal of TY power plant.Compared to world hard coals,Li,V,Cr,Cu,Ga,Se,Zr,Ag,in,Sn,Sb,Hf,Ta,Pb,and Th were slightly enriched in the feed coal of WN power plant;Sc,V,Cr,Ga,Zr,Ag,Hf,and Th were enriched in the feed coal of TY power plant,and Se was significantly enriched.(3)Most elements in coal ash were more enriched than that of world hard coal ash,and Ta and Ag were highly enriched.All trace elements in old ash were at normal levels.The short-time storage of fly ash did not influence the concentration of trace elements.(4)Most trace elements were concentrated in fly ash,such as Cu,Zn,Mo,Tl,Bi,Sb,Sn,and W.Gallium,Ge,As,Mo,In,Sn,Sb,W,Tl,Pb,and Bi,which were volatile during coal combustion,were prone to enrich in fine fly ash particles.Scadium,Cr,Rb,and Ba were enriched in the slag.The smaller the particle size,the more trace elements enriched.(5)The REY in feed coals of the WN and TY power plants were featured by an H-type enrichment with positive Gd and Yb anomalies,negative Eu,Ce,and Ho anomalies.And(6)the outlook coefficients of coal combustion by-products for the WN and TY power plants were calculated,and they were found to be promising for REY recovery.However,as per the evaluation diagram of cut-off grade and Coutl values,all feed coal and its by-products from these two coal-fired power plants are projected to be ‘unpromising’.Therefore,the coal combustion by-products from the WN and TY coal-fired power plants were not candidates for REY recovery.Figure [12] Table [11] Reference [127]...