2025/6/2212.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響1.Heatingvalue發(fā)熱量Gross(higher)heatingvalue(HHV)isdefinedastheheatreleasedfromcombustionofaunitfuelquantity(mass),withtheproductsintheformofash,gaseousCO2,SO2,nitrogenandliquidwater,exclusiveofanywateraddedasvapor. 高位發(fā)熱量(Qgr)：單位質(zhì)量的煤完全燃燒時(shí)所放出的熱量，包括產(chǎn)生的水蒸汽汽化潛熱的發(fā)熱量(kJ/kg)。Thenet(lower)heatingvalue(LHV)iscalculatedfromtheHHV.Itistheheatproducedbyaunitquantityoffuelwhenallwaterintheproductsremainsasvapor. 低位發(fā)熱量(Qnet)：單位質(zhì)量的煤完全燃燒時(shí)所放出的熱量，不包括水蒸汽的汽化潛熱后的發(fā)熱量(kJ/kg)

。2025/6/2221.Heatingvalue發(fā)熱量Watercomesfrom:

thereactionofhydrogenandoxygenH與氧的反應(yīng)moisture(Mar)inthefuel燃料中的含水量MarTherelationshipofHHVandLHVbasedonthedifferentanalysisbases.各成分分析基準(zhǔn)的高位/低位發(fā)熱量間的關(guān)系2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/223Basisconversionofheatingvalue發(fā)熱量基準(zhǔn)轉(zhuǎn)換對(duì)高位發(fā)熱量而言，水分只是占據(jù)了質(zhì)量的一定份額，而使發(fā)熱量降低；采用表2-1的換算系數(shù)進(jìn)行換算。對(duì)低位發(fā)熱量而言，水分不僅占據(jù)了質(zhì)量的一定份額，而且還要吸收汽化潛熱，必須考慮汽化潛熱的影響，采用表2-2換算關(guān)系，(推導(dǎo)過程自學(xué))低位發(fā)熱量先轉(zhuǎn)換成同基的高位發(fā)熱量；通過換算系數(shù)進(jìn)行不同基高位發(fā)熱量換算；再換回要求的同基的低位發(fā)熱量。發(fā)熱量測(cè)定：一般用氧彈法(adiabaticbombcalorimeter)測(cè)定，測(cè)出的為定容發(fā)熱量。定容發(fā)熱量減去硫酸和硝酸的溶于水的放熱量，為定壓發(fā)熱量。鍋爐計(jì)算一般用定壓發(fā)熱量。2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/224Approximatecalculationofheatingvalue近似計(jì)算

Accordingtotheultimateanalysis根據(jù)元素分析Mendeleevformula門捷列夫公式ChinaCoalResearchInstituteformula煤科院公式Theerrorbetweencalculationandmeasurement計(jì)算值與實(shí)測(cè)值的誤差當(dāng)Ad≤

25%時(shí)，Qnet,ar≤600kJ/kg當(dāng)Ad>25%時(shí),Qnet,ar≤800kJ/kg2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/2251.Heatingvalue發(fā)熱量Standardcoalequivalent

標(biāo)準(zhǔn)煤的發(fā)熱量(煤當(dāng)量)Standardcoal:aspecifiedcoalwhosenetheatingvalueaccordingtotheasreceivedbasisis7000kcal/kgor29308kJ/kg.Standardcoal標(biāo)準(zhǔn)煤:

一種假想的煤，規(guī)定收到基低位發(fā)熱量為7000kcal/kg(29308kJ/kg)，國際上法定的能量折算單位。Standardcoalconsumption

標(biāo)準(zhǔn)煤消耗量：

2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響

kg/h2025/6/2261.Heatingvalue發(fā)熱量Convertedcomposition折算水分、折算灰分和折算硫分在討論雜質(zhì)(水分、灰分)對(duì)鍋爐工作的影響時(shí)，使用其折算值更合理。燃料燃燒每放出單位熱量（常取1000kcal或1兆焦）所對(duì)應(yīng)的水份、灰份、硫份的量稱為煤的折算水份、折算灰份和折算硫分。1）折算水分：煤低位收到基發(fā)熱量中每4186.8kJ熱量所對(duì)應(yīng)的水分。

%；大于8％為高水分燃料2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/2271.Heatingvalue發(fā)熱量Convertedashandsulfur折算灰分和折算硫分2）折算灰分：煤低位收到基發(fā)熱量中每4186.8kJ熱量所對(duì)應(yīng)的灰分。 %；＞4％為高灰分燃料3）折算硫分：煤低位收到基發(fā)熱量中每4186.8kJ熱量所對(duì)應(yīng)的硫分。 %；＞0.2%為高硫分燃料2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/2282.Volatilematter揮發(fā)分Component組成

Hydrocarbon碳?xì)浠衔飄ydrogen氫氣COH2SO2N2

氮?dú)釩O2等2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/2292.Volatilematter揮發(fā)分Characteristics特點(diǎn)VMdecreaseswithincreasingofcoalification,suchas:VMoflignite>40%,anthracite≤8%. 揮發(fā)分含量隨煤化程度加深而減少;ReleasetemperatureofVMincreaseswithcoalification.

煤的揮發(fā)分析出溫度隨煤化程度加深而升高，如依次為lignite褐煤、bituminouscoal煙煤、leancoal貧煤、anthracite無煙煤；FastIgnition,stablycombustionofcoalshavinghighVM.揮發(fā)分含量高，著火迅速，燃燒穩(wěn)定；VMwillaffectfurnacestructureandoperationofboiler.揮發(fā)分大小影響鍋爐爐膛結(jié)構(gòu)和運(yùn)行方法；Animportantindicatorofcoalclassification,作為煤的重要分類依據(jù)。

2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/2210Coalrank煤種VdafVMreleaseTemp逸出溫度(℃)IgnitionTemp著火溫度(℃)lignite褐煤>40130~170250~450Bituminouscoal煙煤20~40170~320400~500Leancoal貧煤10~20370~390600~700anthracite無煙煤<10380~400>7002.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響Therelationshipoftemperatureswithcoalrank2025/6/22113.

Cokecohesiveness

煤的焦(粘)結(jié)性煤的焦(粘)結(jié)性對(duì)層燃爐運(yùn)行影響較大。2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/22124.Ashfusibility灰的熔融性(pp20;pp21-5)Ashfusibilityhassignificanteffectsonboilersafeoperatingandboilerefficiency. 灰的熔融性對(duì)鍋爐運(yùn)行的經(jīng)濟(jì)性和安全性有很大影響1)定義：灰在加熱時(shí)，由固態(tài)逐漸向液態(tài)的轉(zhuǎn)化特性。Thecharacteristicsofsolidashconvertingtoliquidashwhenashisheated.Themeasurementofashfusibilitytemperaturesisbyfarthemostwidelyusedmethodforpredictingashbehavioratelevatedtemperature.2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/22134.Ashfusibility灰的熔融性2)Measurementmethod測(cè)定方法Anashsample(dp<0.2mm)ispreparedbyburningcoalunderoxidizedconditionsattemperatureof799to899C.Theashispressedinamoldtoformatriangularpyramid(cone)20mminheightwitha7mmtriangularbase. 取粒度小于0.2mm的空氣干燥樣，按GB212-1991規(guī)定完全灰化，然后研磨至0.1mm以下，制成三角錐。Theconeisheatedinafurnaceatcontrolledratetoprovideatemperatureincreaseof8oCperminute.Theatmosphereinthefurnaceisregulatedtoprovideeitheroxidizingorreducingcondition.2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/22142.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響4.Ashfusibility灰的熔融性(pp20;pp21-6)Whenthesampleisheated,fourdeformationtemperaturesarereportedasfollows:Initialdeformationtemperature,DT變形溫度Softeningtemperature,ST軟化溫度Hemisphericaltemperature,HT半球溫度Fluidtemperature,FT流動(dòng)溫度STHT一般使用ST作為表征灰的熔融性的溫度。在鍋爐設(shè)計(jì)時(shí)，為避免爐膛出口結(jié)渣，要求出口煙溫應(yīng)比ST低100℃。2025/6/22153)Furnacedesignforashremoval(p21-2)Historically,twodistinctlydifferenttypesoffurnacedesignwereusedtohandletheashfromcoalfiringinlargeutilityboilers.Thesearecommonlyreferredtoas:Thedry-ashordry-bottomfurnace.固態(tài)排渣爐Theslag-taporwet-bottomfurnace.液態(tài)排渣爐Inadry-bottomunitmostoftheash,typically70to80%,isentrainedinthefluegasandcarriedoutofthefurnace.Thisportionoftheashiscommonlyknownasflyash.2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/22163)Furnacedesignforashremoval(p21-2)Someoftheflyashiscollectedinhoppersarrangedundertheeconomizerandairheaters,wherecoarseparticlesdropoutofsuspensionwhengasflowdirectionchanges.Thefinerashparticlesremaininsuspensionandarecarriedoutoftheunitforcollectionbyparticulatecontrolequipment.Theremaining20to30%oftheashthatsettlesinthefurnace,orisdislodgedfromthefurnacewalls,iscollectedinahopperformedbythefrontwallandrearwalltubepanelsatthebottomofthefurnace.Thisbottomashisdischargedthrougha3to4ft(0.9to1.2m)wideopeningthatspanstheentirewidthofthehopper.2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/22173)Furnacedesignforashremoval(p21-2)Theslag-taporwet-bottomfurnace,whichwereoriginallydevelopedtoresolveashdepositionandremovalproblemswhenfiringcoalswithlowashfusiontemperaturesindry-bottomfurnaces.Theseunitsareintentionallydesignedtomaintainashinafluidstateinthelowerfurnace.Moltenashiscollectedonthefurnacewallsandothersurfacesinthelowerfurnaceanddrainedcontinuouslytoopeningscalledslag-tapsinthefurnacefloor.Watertankspositionedbeneaththeslag-tapssolidifytheliquidashfordisposal.2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/22183)Furnacedesignforashremoval(p21-2)Theapplicationofslag-tapunitsforpulverizedcoalfiringbegantodecline(減少)inthelate1940s,primarilyduetodesignimprovementsindry-bottomunitsthatminimizedashdepositionproblems.Slag-tapunitsequippedwithCyclonefurnacescontinuedtobeapplieduntiltheearly1970swhenthefederalCleanAirActmandatedcontrolofnitrogenoxides(NOx)emissions.Thehighfurnacetemperaturesrequiredforwet-bottomoperationwerehighlyconducive(有利于)toNOformation.Allmodernpulverizedcoal-firedboilersusethedry-bottomarrangement.2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/2219Fig.1:Thecoal-firedboilerBottomash:20~30%flyash:70-80%2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/2220Ashdeposition(pp21-3)Regardlessofthefiringmethod,whencoalisburned,arelativelysmallportionoftheashwillcausedepositionproblems.Ashpassingthroughtheboilerissubjecttovariouschemicalreactionsandphysicalforceswhichleadtodepositiononheatabsorbingsurface.Theprocessofdepositionandthestructureofdepositsarevariableduetoanumberoffactors.Particlecomposition,particlesizeandshape,particleandsurfacetemperatures,gasvelocity,flowpatternandotherfactorsinfluencetheextentandnatureofashdeposition.Dueprimarilytothedifferencesindepositionmechanismsinvolved,twogeneraltypesofhightemperatureashdepositionhavebeendefinedasslaggingandfouling.

2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/2221Ashdeposition(pp21-3)Slagging(結(jié)渣)istheformationofmolten,partiallyfusedorresolidifieddepositsonfurnacewallsandothersurfacesexposedtoradiantheat.Slaggingcanalsoextendintoconvectivesurfaceifgastemperaturesarenotsufficientlyreduced.Fouling(污垢、積灰)

isdefinedastheformationofhightemperaturebondeddepositsonconvectionheatabsorbingsurfaces,suchassuperheatersandreheaters,thatarenotexposedtoradiantheat.Ingeneral,foulingiscausedbythevaporizationofvolatileinorganicelementsinthecoalduringcombustion.Asheatisabsorbedandtemperaturesareloweredintheconvectivesectionoftheboiler,compoundsformedbytheseelementscondenseonashparticlesandheatingsurface,formingagluewhichinitiatesdeposition.2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/2222Ashdeposition(pp21-3)AreaswhereslaggingandfoulingcanoccurareshowninFig.2Figs.3and4showheavilyslaggedandfouledsurfaces.2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/22234)Influencingfactorsonashfusibility影響因素分析(pp21-4)MineralogicalcompositionTherearenostandardizedmethodsthatareusedroutinelyfordeterminingthespecificmineralconstituentsofcoal.Mineralogicalanalysisrequirestheuseofalowtemperatureashingtechniquetoseparatethemineralmatterfromtheorganicportionofthecoal.Standardhightemperatureashingprocedureswouldsignificantlyalterthemineralforms.However,anumberofresearchers,usingavarietyoflowtemperatureashingmethodsandsophisticatedanalyticaltechniques,haveidentifiedanenormousvarietyofmineralspeciesincoal,encompassingtheentirespectrumofthesemineralsfallintooneofseveralgroups:clayminerals(aluminosilicates),sulfides/sulfates,carbonates,chlorides,silica/silicatesandoxides.SomeofthemorecommonmineralsinthesegroupsareshowninTable2.2.3Coalcombustioncharacteristics

§2-3煤的特性及其對(duì)鍋爐工作的影響2025/6/2224clayminerals(aluminosilicates),sulfides/sulfates,carbonates,chlorides,silica/silicatesoxides.2025/6/2225ChemicalcompositionBecausebothquantitativeandqualitativeevaluationofmineralmatterformsareextremelydifficult,relativelysimplechemicalanalysesarecommonlyusedtodeterminethepercentagesofthemajorelementsintheash.ElementalashanalysisisperformedonacoalashsampleproducedinaccordancewiththeASTM3174ashingprocedure.Pulverizedcoalisburnedinafurnacewithanoxidizingatmosphereat1292to1382F(700to750C).Theelementspresentintheasharequantitativelymeasuredusingacombinationofemissionspectroscopyandflamephotometryandarereportedasweightpercentsoftheiroxides.Coalashconsistentlyfoundtobecomposedmainlyofsilicon,aluminum,iron,

andcalciumwithsmalleramountsofmagnesium,titanium,sodiumandpotassium.TheelementalanalysisalsoidentifiesphosphorusasP2O5andsulfurassulfurtrioxide(SO3).SulfurisreportedasSO3becauseitisnormallypresentasth