Geochemistry of Permian Coal and Its Combustion Residues in Huainan Coalfield, China

Printed in Chniversity of Geosciences, Vol. 12, No. 4, p 283-290, December 2001ISSN002-0705Geochemistry of Permian Coal and Its CombustionResidues in Huainan Coalfield, ChinaP5Department of Energy Resources and Geology, China University of Geosciences, Beijing 100083Peng SupinDepartment of Geology and Engineering, China University of Mining and Technology, Beijing 100083Department of Resources and Environment, Huainan Institute of Technology, Huainan 232001INAA (instrumental neutron activation analysis)was used to determine the contents of trace ele-ts in coal samples from Il workable Permian coal seams in Huainan coalfield. with XRFS(X-rayPower Plant and Luohe Power Plant was analyzed. In addition, the electron microprobe was employedto study the chemical composition of some ny ashes and bottom ashes, Compared with those of the coalstrace elements of the Huainan coalLike most coals worldwide. the elements Se, S, As, Sb, Br, U and Cl are enriched in Huainan coal according to Clarks value, while the other elements tend to be diluted, The large fluctuation in the con-tents of trace elements in this kind of coaltrates great differences in coal seams. On the othercontents of these elements are very similar in diferent bottom and fy ash samples. The ele-organic altinity tend to concentrate in ny and bottom ash than in coal, especialelements associated with Fe, However. the elements with strong organic affinity tend to be volatile dur-ing the combustion. Moreover, the abundance of the elements in fly ash and bottom ash changes withdifferent densities and with different particle sizes. The bottom and ny ashes consist of glass, limmullite,coal residues and ferrite minerals. Some residual chars contain higher contents of volatile ele-ments. such as S, P, Cl and As, indicating that the ash containing more residual chars has a strong ad-sorption of some hazardous elements, suggesting a possible utilization of power plant ash in the field ofwater cleaning.KEY WORDS coal, trace element, combustion resides, geochemistry, INAA, China.INTRODUCTIONovic, 1983). For example, when coal wastes are used for landMany environmental problems may arise during coal min- reclamation, the harmful elements in them may pollute watering and utilization. Among these problems, much attention has soil and crops. The solid combustion residues may pollute wabeen paid to SO and NO, emission during coal combustion. ter and soil during their storage and utilization, The harmfulBut the environmental effects produced by hazardous elements materials thus produced during coal combustion and coal theduring coal mining and utilization are also important and de- mal decomposition may also affect the atmosphere and waterserve to be studied(Goodazi, 1995: Finkelman, 1993; Valk- But, little research has been developed on this topic in ChinaThe combustion residues reach nearly 0. 1 billion tons while thes This paper is supported by the National Natural Science Foundation Chinacoal production reaches approximate 1. 3 billion tons in 1998 in-· land reclamationand by the 973"中国煤化工roject(G199902220101)ruction. addiforCNMHGwater source areaManuscriThus, drinKing wnd crops may be dete-Manuscript accepted October 20, 2001riorated by hazardous materials. It is necessary to determineHuang Wenhui, Yang Qi. Peng Suping and Zhao Zhigenhazardous elements in coal and its combustion residues in order raw coal. the sulfur contents of coal seams in Shanxi Formaevaluate its negative effects on the environment during coal tion are higher due to the seawater effect during coal formautilization,to guide the utilization of both coal mining wastes tion. The content of phosphorus is very low, often 0. 006and combustion residues and to predict potential environmental 0.035 %(Zhao, 1991)effects(Goodarzi, 1995). In this paper, INAA(instrumentalneutron activation analysis)and XRF(X- ray fluorescence spec- EXPERIMENTStrometry)are used to deThe coal samples are collected from 10 workable coalin different coal samples from workable Permian coal seams in seams of Shanxi Formation, Xiashihezi Formation and ShangHuainan coalfield and in different combustion samples from shihezi Formation, as shown in Table 1. Afler being channellTianjiaan Power Plant and Luohe Power Plant whose major fu- ed from all coal seams, the samples are ground and mixed inel is Huainan coal. The electron microprobe is used to deter- the laboratory. The contents of trace elements in coal samplesmine the chemical composition of fly ash particles, and the ex. are determined with INAA. HK is determined with cold vaporperimental data are employed to study the distribution and seg- atomic absorption spectrometry. The combustion residues ofregation of trace elements, This study will further our under- coal are systematically collected from the power plants residue-standing of the distribution of trace elements. the transforma. storage pool. The XRF at the Geology and Mineral Researchtion mechanism of minerals in coal, and the geochemistry of Institute of Nuremberg University in Germany was used to decombustion residues. In this sense. the present research offers termine the geochemical composition of combustion residueus the basic information on different kinds of benefits including The electron microprobe at China University of Geosciencesthe rational use of coal, the proper disposition of solid combus- was employed to study the chemical composition of fly ashestion residues, and the utilization of combustion residues as a The experimental condition and precision are the same as thoseresource and environmental protection.in the published paper(Huang et al., 2000: Huang and Yang1999)GENERAL INFORMATION ON STUDY AREA AND COALSEAMSRESULTS AND DISCUSSIONHuainan coalfield, located in southeast margin of North Composition of Coal AshChina platform, is one of the main coal mines in the center of The composition of coal ash is often used as a geochemicalAnhui Province. The coal seams are mainly developed in indicator of the coal-forming environment. In the 1950s,re-Shanxi Formation, Xiashihezi Formation and Shangshihezi For- searchers in the former USSK used the index of coal ash com-mation of Permian strata. There are more than 30 coal seams, position(ICAC) to distinguish between reducibilities of differand the total thickness of coal seams is 31 m. The workable ent coal seams when they studied the geochemistry of Donbasscoal seams are mainly concentrated in the lower part of the coal. The ICAC was defined as w( Fe: O Cao t Mgocoal-bearing strata( Yang and Han, 1979).w(SiO,+Al,,). Zhao(1991)suggested three coal reducibleShanxi formation in the early stage of the Lower Permian genetic types(relatively strong reductibility, moderate reductwas formed under a lower delta scenario, developed in a bay. ibility, relatively weak reductibility )in a study of coalXiashihezi Formation in the late stage of the Lower Permian Taiyuan Formation and Shanxi Formation of Late Paleozoic inwas deposited between upper and lower delta plains. The North China. Based on this study, was proposed the geneticShangshihezi Formation of Upper Permian also occurred in the model of "the sedimentary environment type of coal-formingdelta plain environment, but it was close to continental source characteristics of coal quality"(Zhao, 1991). This paper alsoshows that it is a decisive factor for the determination of coalThe macro lithotype of coal seams in Huainan coalfield is whether the peat swamp was invaded by seawater or not duringmainly characterized by semi-dull coal and semi-bright coal. coal formation. The invasion of seawater affected not only coalVitrinite is over 50 % while fusinite is around 20 % Exinite type, content of sulfur, index of coal ash composition (ICAC)mainly consists of megaspore, microspore, resinite, suberinite but also the mineral matter of coal, types and contents of asso-and cutinite, and the contents of exinite increase in the coal ciated trace elements in the coal. It is more important to make aseams of the upper part of coal-bearing strata. Clay minerals study of the trace element associations in different coal formingare a main inorganic component, while sulphides, quartz, car types than to determine the contents of trace elements in differoates are scarce(Zhao, 1991)Most coals in Huainan coalfield belong to gas coal. The of different constituents in the same coal seam are slightcommon volatile matter yield is 30. 63 %-40. 79 % and the ferent中国煤化工 nts of different cvolatile matter yield decreases with the increase of burial depth formie, the decisive factorof coal seams. Coal ash of different coal seams often ranges be- is defiHCN MH GI type) instead of astween 15 %, and decreases to 12 after being the"carrier"(constituent).washed.The averaged content of total sulfur is 0. 33%-1.63 The chemical composition of coal ash in the studied coal%. Organic sulfur exceeds sulfide sulfur in most coal seams, seams is shown in Table 1. From the table, the acid and alkahigher content of sulfur for cleansed coal than for line compositions change regularly from the lower co.Geochemistry of Permian Coal and Its Combustion Residues in Huainan Coalfield, ChinaTABLE 1 CHEMICAL COMP(SITION OF COAL ASH FROM COAL SEAMS IN HUAINAN COALFIELDcoal seam formation w(SiO) w(Al: ())w( Fer 0)w(Cao) w(MgO) w(TiOh)w(K2 O) w( Na: 0)w(SO)) ICAC55.0529.311,0355.1330.454.641.9Ⅱ52.7930.024.563.741.531.5332,804.191,391.490.980.67704.971.216.671.471.38604b29029.085,123648.9028,602.020.9253.7824.057.094711.12mean value53.67128.2625,6063.0231.4391.3471.0180.7372.09414.51Note: ICAC means index of coal ash composition. I. Shangshihezi Formation: l. Xiashihezi Formation: B. Shanxi Formationhe upper coal seams, The chemical composition of coal ash is reflects the natural feature of inhomogeneity of the coat itselfdependent on the mineral matter in coal, and the mineral com. Thus, in order to reflect truthfully and affirmatively the distriposition in coal is controlled by the continental clastics and sed- bution of trace elements in coal, more samples are needed,Theimentary basin. In general, the supply of continental clastics is contents of some elements are extremely low, less than 1 xplentiful, and the invasion of seawater is weak because of the 10". Therefore, the significant deviation of experiment re-shortage of pyrite. Therefore the composition of the mineral sults may occur due to minute errors of detection and slightmatter reflects mainly the origin of the continental clasticontaminations of samples. In this sense, in order to guaranteeSiO,. Al O and TiO, acid components in coal ash, the reliability ofmainly reflect the feature of continental clastics. The w(SiO2)perimental conditions and experimental method must be srandand u(Al, O,)in coal ash are high, above 53 and 28%, re- ardized. In addition, caution is needed when different coalspectively. Fe:, O,, CaO, MgO, Na:O, alkaline components, seams are correlated with very low contents of elements, Furreflect partially the geochemical feature of sedimentary basin thermore, the coal samples with the same ash have been usedluring the coal formation. Usually, the percentage of alkaline for a better comparison because contents of many elements arecomponents is high for the coal seams formed in strongly sea- correlated with contents of mineral matter in coal. These ele-water-invaded swamp environment, which is indicated by high ments with positive correlation with coal ash in the same coalu (Fe2 O,), w(CaO)and w(MgO)and higher index of coal ash seam come mainly from continental clastics. On the contrary,composition for coals in Shanxi Formation. Just like other those elements without any correlation with coal ash may havecoalfields in North China platform, the effect of seawater strong organic affinity, or may originate from epigenetic miner-changed from strong to weak during the whole period of coal alization.orationDifferent elements are correlated with each other in differ-ent degrees. The result of cluster analysis is shown in Fig. 1DistribatHom Character of Trace Elements in CoulThe elements including Si, AL. K, Rb. Cr, Ba, Ti, Fe andTable 2 shows the contents of 37 elements in ll workable REe are grouped together when their correlation coefficientcoal seams of Huainan coalfield. L a, Ce, Nd, Sm, Eu, (d, reaches 0. 6, and these elements belong to continental clastics-Tb, Yb and Lu were analyzed by INAA. the contents of un derived element groups. however, elements including Ni, codetermined rare earth elements( Pr, Dy, Ho, Er and Tm) Sr, Ca, Br and As are connected with sedimentary basis andwere extrapolated from chondrite-normalized plots Wang et diagenesis instead of with continental origin, and elements ofaL., 1989). According to Clark value, elements including Se, this group have high contents in the Shanxi Formation coalS. As, Sb, Br and U are enriched. The contents of the most seams influenced strongly by seawaterrace elements in coal vary within a moderate range, while that The groups are divided according to the mode of occurof Zn varies up to 100 times. These elements whose variation rence of the elements in the coal. First, group elements havelies within a relatively wide range are sensitive to the effect of an organic affinity, and the occurrence can be organic comdiagenesis and are commonly used to reflect the features of sed- pound, complex compound, chelate or adsorption mode. thisimentary basin and diagenesis. The contents of some other ele- groupnents in different coal seams such as K, Ti, U, Ag, Rb. Zr, Y, Mo中国煤化工x0 mpound withSc. Ba and REE vary within a relatively small range and are organicCNMHG, such as St, Al.mainly controlled by coal ash. The small variation of these ele- REE. K, Rb and Ti, exist in the form of mineral matter inmainly reflects the origin of continental clastics and is coal. and these elements may have a continental origin or authi-tal clastics in this papergenic mineral origin. Usually, those elements in the first groupthe wide range of trace elements in coal with a strong affinity with organic matter or combined in pyriteHuang Wenhui, Yang Qi, Peng Suping and Zhao ZhigeTABLE 2 MASS FRACTIONS OF TRACE ELEMENTS IN HUAINAN COALSsample coalfield coalCaK Na 'Ii Cr Co Ni U Th w Mo ZnH-13aHuainan CIa1.070.840.312090167072141553.513.73.12.216H-11b Huainan Bll b2.530.560.0789001290269811.715.82.06,H9 b Huainan B9b0.830,800,715301040238611.41.91.04.93Huainan B9 a1.480.490.2397012003810342.99.21.05.11lHuaina3.350.200.097204403120343.112.52.4Huainan B72.900,4819723.99.20.90.75H-6Huainan B5260,073215711.98.02.44.21022.930.320.086501003413461.56.80.7.470.990.160.0210331.23.71.23.821Huainan Al2.31430520162161.43.60.0.090.160.02430100112161.23.60.23.351.120.718900167072301553.915.83.17.41021.720.5l0.181580461.300.188008006142.13.21.03,353warld coal ( mean)200500105151.0Au Ag As Sb Hg Rh CszrHH-13a280.43.90.163251.51.11914.619.71982500.0916.30.6280.61.70.2173121.00.61895.311.437910.0111.66.2350.30.80.334202.50.9273.424.91416.21230.51.90.7831.20.51012.29.5131840.0110.20.5H-9a290.21.80.365201.10.81373.213.31011380.02120.91.30.280.71.02444,115.41121000.0813.24.962.00.211340.8982,915.3601280.088.711081070.036,71.5150.31.10.27991.10.83.910.5109370.057.81.5350.419.47,15760.30.31171.12.953780.068.01.120.20.80.1141.02.937370.011.60.5350.919.47.1173252.51.12445.324.91982500.1416.312mean1.10.71343,212.61051100.0610.32.95.0500500ree La Ceu Gd Tb Dy Ho ErTmH-13a21651.3996.4910.0534.105.291.073.740.684.731.063.150.49H-1lb13733.3710.967.6026.564.250.772.550.483.450.802.2.65.42H1019943.3786.649.2932.495,241.123.800.735.371.273.990.664.510.8119.5738.114.3115.902.45033H-ga23151.5499.011.0940.496.721.224.510.755.311.213.650.583.810.6617535.2077.088.0327.244.851.043.870.745.401.273.960.654.400.7916235.1270.107.2024.074631.023.790.715.081.183.590.573,840.6011824.3551.375.5719.682.730.682.770.513.590.812.430.382.520.5118338.3485.538.7329.014,350.963.290.614.330.992.990.473.150.53050.28n0aRR0.140.680.12中国煤化工591,050.04CNMHG I4 0.680max23151.5499.011.0940.496.721.22328766.797.0624.353.920.812.980.55Amerca coal1.900.351.000.150.950.l4world coal204,701.600.701.600.300.300.60Ca, Fe.K is % unit of Au is 10, that of ot hers is 10Geochemistry of Permian Coal and Its Combustion Residues in huainan Coalfield, Chinaare mainly concentrated in the slag and bottom ash. the traceelements with moderate volatility are partly transformed intosolid mode and congregated in fly ash after their gasificationand partly dispersed into atmosphere. And, the trace elementsREEwith strong volatility are mainly dispersed into atmosphereHuang et aL., 1999: Xu, 1991). The combustion residuesG腿from the huainan coal employed by Tianjiaan Power Plant andLuohe Power Plant were analyzed with XRF. The experimentalesults are listed in tables 3 and 4. The combustion residuesmainly consisted of bottoom ash aand fly ash.The results show that compared with the contents in coalthe contents of oxides of Si and Ai are close, and those of oxides of Ti as well as K and Na are slightly higher, while thoseof oxides of Fe and Mg are obviously higher. The loss of K. Caind Na in fly asver water. Fe isdifficult to be leached and to be transformed into gaseous statethus the Fe oxide content is higher in general. Fe, O), in someFigure 1. Cluster analysts of elements in Huainan coal, samples of fly ash are up to 20 % because of gravitationalwashing of fly ash, which gives us a clue that different kinds ofare prone to be dispersed to the atmosphere or stick to the sur- components with different utilizations may be separated withface of fine fly ash during coal combustion( Mukhopadhyay et gravitational washing method. Furthermore, the alkalinity ofal.1996),while the second group elements with an affinity fly ash (0. 18)is slightly higher than that of coal ash (0.14)with clastic mineral matter tend to be enriched in the bottom so that the fly ash is more basic.ash( huang and Yang, 1999; Sun and Jervis, 1986). w(rEE)Unlike those of major elements, the mass fractions ofin coal lie between 52 10-and 216 x 10-. In addition, the trace elements in different bottom and fly ash samples arew(rEE)are closely related to the continental elements, but close. The amount of samples are not enough to analyze syspart of ree has been transformed in organic constituent tematically their correlation arnong different elements, but( Huang et al., 2000, Seredin, 1996). Compared with Ameri- many correlations with contents of Fe are derived from the datacan coal(Finkelman, 1994, 1993, 1982), elements including in this paper. The calculation shows that the elements withCa, Na, Cr, Co, Ni, Th, Zr, Hf. Sc, Se and REE have high- positive correlation with Fe include Mn(0. 99), Mg(0. 95)er mass fractions in Huainan coal but the other elements have Mo(0. 94),Ni(O. 94),Co(0. 92),Ca(0. 70), Cu(0. 67)w(.54)and Zr(0. 52), while those with negative correlationK(-0.93),Al(-0.91),Rb89Chemical Composition of Coal Combustion Residuessi(-0.87),Ti(-0.77),Nb(-0.71),1a(-0.71)The organic matter in coal is transformed in heat and gases Ga(-0. 71), Th(-0. 67), Pb(-0. 66), Ce(-055)andduring combustion(Xu, 1991; Sun et al.. 1986). Therefore, As(-0 30). Some elements such as Ni, Mo, Co and Cu withhe character of coal ash is dependent on the composition and positive correlation with Fe are potentially harmful metallic ele-distribution of mineral matter in coal. The combustion prod. ments and exist mainly in the mode of sulfide in coal. anducts are transformed into slag, bottom ash, fly ash and gases. transformed into oxides of Fe in bottom and fly ash, while sulThe differentiation between elements is significant. Thus, con- fur is turned mainly into gases and released after combustion.tents of elements in different combustion products will be help- It is noteworthy that the contents of some harmful traceful to understand the transformation mechanism of trace ele- elements in bottom and fly ashes increase from several times toments and to guide the proper utilization of combustion resi- about ten times, The elements with strong volatility such aduesHg, B and Cl, etc. are released to the atmosphere or con-Trace elements occur in coal as such minerals as chelate densed on the surface of fine fly ash particles, but these eletend to be differentiated and transformed during the combus- ments are prone to be released by leaching. The elements withtion until coal particles in a furnace chamber are entirely ther- large atomic weight occur mainly in solid phase of combustionmally decomposed and burned. After this complex chemical and residue( Sun and Jervis, 1986). Those data are helpful tophysical process, all kinds of trace elements are transformed guide resalthough it is dif-and redistributed in slag, bottom ash, fly ash and gases. This ficult to中国煤化工with the contentsredistribution process is connected not only with distribution of elemeCN MH Giver water.Howmode of elements in coal, physical and chemical character of el. ever. the potential harmful elements including Cr, Ni, U, Th,ements,total amount of organic matter in coal and contents of w, Mo, Zn and As are enriched in bottom and fly ash. There-silicate minerals but also with condition of combustion. Like fore, it is worthwhile to make a further research to produce amajor elements in coal, the trace elements with low volatility better evaluation.Huang Wenhui, Yang QI, Peng Suping and Zhao ZhigenTABLE 3 MAIN ELEMENT OXIDES OF BOTTOM AND FlY ASH FROM POWER PLANTS(FTIANJIAA、 AND LUOHEsample SiOz TiO: AlgO FezO Mn( MgO Cao Na?0 K,O P2O ($O3) (CI) (F) lol sum IC(L052.200.8925.0813.660.070,803.020.320.830.17<0.010.01<0.012.7099.4824L3555,021.1331.035.300.030.611.700.370.950.19<0.010.00<0.013.3199.5713L4043.890.8523.5324.320.130.912.970.260.720,170.100.00<0.t11.9599.4313L4552.090.9426.9612.380.070.762.500.310.860,170.l10.01<0.02.5899.1121L5554.371.2732.414.250.020.591.580.381.000.23<0.010.01<0.013.4899.5309L6548.900.8624.6318,380,090.812.890.270.800.170.030.01<0.1.9399.4931T-150,571.1030.844,800.040.582.220.200.960.170.050.01<0.018.0999.5811T554.670.8726,338,190.050,733.340.281.020.120.150.0<0.04.0099.6217T-1055.990.929.645.350.030.581.630.370.970.15<0.010.00<0.013.979.5810T2954.06L.1330.604.180.030.521,760.320.940,19<0.010.01“0.015.889.5809mean52.181.0028.1110.080.050.692.360.310.910.170.090.01<0.03.799.5418Index of coal ash composition=w( Fe2 O+Cao+MgO)/w(Si(+Al (),TABLE 4 TRACE ELEMENT MASS FRACTIONS OF BOTTOM AND FLY ASH FROM POWERPLANTS OF TIANJIAAN AND LUOHEsample As Ba Bi Ce Co Cr Cu Ga Hf L a Mo Nb Ni Pb Rb Sr Ta Th U V w Y Zn Z12694<31493986842798520731834367171122314:739347<3157289489406853244939414396232728L4015686<313250g211225680272010122323595191720911561234913649<31403592673369823653037376319132310584232u19724<31742495675271162255260435407241427787167315L6512642<3129427971229721919731334349517132101657363613587<315712652722697195794522l6191219|12183445102600<31482289653581004234434413743201127010561325T2921548<3156238764438101324474742514425132531616930214624<3145318772347958225932394135213125849316TABLE5 TRANSFORMATION SCHEME OF PRIMARY MINERALS IN COAL TO NEO-FORMEDMINERALS IN COMBUSTION RESIDUEStransformation products in fly ash and bottom ashphyllosilicatesglass, mullite(Als Si O13) and quartzpyrite(FeS2), siderite(FecO,hematite(Fe: ()), magnetite(Fe304)errite spinel(Fe( with solid substitution of Al. Mg, T1)calcite (CaCO3)lime( caollime(CaO), periclase( Mg()gypsum( CasO4 2H2 0)anhydrite( CasO.)ankerite [CaMg Fec -,)(CO))alcium ferrite (CaFe? 04), periclase(Mgo)Chemical Composition of Fly Ash Particlesoften large, up to 100 Am, and the residual char are similar toThe aluminosilicate. quartz, pyrite, hematite, carbonate, the fusinite of raw coal with good preservation of cell cavitysulfate, phosphate, halide in raw coal were transformed into The common particles including silicate solid sphere, glass hodifferent crystal minerals and glassy components during high- low sphere, glass foam sphere, heterolite sphere and structuretemperature combustion after many complex thermal and chem- residual char are detected by electron microprobe whose resultsical reactions and after deformation, breakage, melt, and are中国煤化工esults of electron mi-spherulitization(Table 5)Through observation of fly ash particles by microscope. kindsyHC N MH GS uSually have obvithe inorganic components consist mainly of glass sphere, glass ous regularly-arranged surface veins, which have their origin infoam, heterolite sphere, mullite and quartz with diameters the transformation of Fe sulfides. Cracks are produced whenranging from 0. 05 um to 80 Hm. The organic components are the particles are melted and a large amount of gaseous sulfur ismainly residual char and coal particles. The residual char are released at a high temperatureeochemistry of Permian Coal and Iis Combustion Residues in Huainan Coalfield. China289TAHL.E5 ANAL YSIS RESULTS (F ELECTRONIC MICROPROBE FOR SOME FLY ASH PAR'TECLESype of particles SiO: TiO Al2 O Cr O)a Feo MnO Mgo Ca() Co() Nio) K:0 Na20)P, (; Zn() Aso)heterolite sphere 0.320.270.2095,110.700.370.090.120.160.67,n7251.37U.480.061.33heterolite sphere 4, 31 0. 08 0. 54 0. 22 90.140.251.37480.061.33.382.0836-83.562.173,751,620.010.08Fe, Sirich sphere I2.880.092,400.0461.801.893.5910.800.0.100.030.98silicate sphere 25. 78 0.352.1624.900.270.021.87hollow sphere45.650.1226.540.0815.460.070.650.130.310.41ollow sphere 44, 37 0. 23 25. 4914.670.011.240.100.050.021.850.020.31residual char. 0.31- 0.470,150.080.060.040.150.131.051.34sidual char0.070.060.0.220.010.010,l0.052.670.92-0.260.61077,33glass foam sphere 61.58 0 23 14. 36920.203.600.030.420.010.010.05glass foam sphere27.851.3548.810.252.21-1.07.88glass;“*, structureThe content of Fe oxide is high in particles and Fe-affinity riched at a high percentage. Some harmful eiements withand S-affinity elements are associated in particles while the con strong volatility are prone to be decomposed or diffused to wa-lenIs of Si, Al oxides are very low, The silicate solid spheres ter through leaching, resulting in more serious potential hazcome mainly from clay minerals in coal, and the contents of Si, ardAl oxides are high, while some other alkaline-earth metal ele (4)Fly ash particles are mainly formed from higb-temperments oxides are associated in particles. The glass hollow ature transformation of mineral in coal. And. ny ash particlesspheres mainly consist of Si, Al, Fe oxides, but the glass foam mainly consist of glass spheres and minerals with rich Si andspheres mainly consist of Si, Al oxides, The structural residual rich- Al oxides, minerals with rich-Fe oxides and residual charhar adsorbs more S, Cl and Asadsorbed with Cl, s and AsCONCLUSIONSACKNOWLEDGMENTSThe research into the distribution of trace elementsThe project is supported by the National Natural ScienceHuainan coal. in terms of the chemical composition of coal ash Foundation of China(Nos. 49872054 and 49632090) and byand coal combustion residues, and the composition of fly ash the 973"project (G1999022212-01 01). The authors wish toparticles with electronic probe, shows the following prelimina. express thanks to the Institute of High Energy Physics of Chiry conclusions.Academia Sinica and the Geology and Mineral Research In(1) Huainan coal is formed in the delta plain environment, stitute of Nuremberg University in Germany for their kindThe trace elements can be divided into two groups. The first-Thanks are also given to the Huainan Coalmine Admin-group elements are supplied mainly by continental clastics, and istration Bureau for their assistance. We are grateful to Drontrolled largely by the characteristic of the continental ori. Robert B Finkelman, Dr C-L Chou. Dr X Qucrol and Prof Agin. The contents of elements in the first group vary within a Zhang for their reviews of the manuscript and constructivenarrow range, but tend to rise from the lower to the upper commentscoal-bearing strata. 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