南师大锅炉原理课件3-3 锅炉热平衡的组成及锅炉效率

2025/6/2213.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率锅炉热平衡是研究燃料的热量在锅炉中利用的情况，有多少被有效利用，有多少变成了热量损失，这些损失又表现在哪些方面以及它们产生的原因。热平衡目的是为了有效地提高锅炉热效率。锅炉热效率是锅炉的重要技术经济指标，它表明锅炉设备的完善程度和运行管理的水平。提高锅炉热效率以节约燃料，是锅炉运行管理的一个重要方面。锅炉的热平衡(或热效率)试验是为了全面评定锅炉的工作状况。通过测试分析影响锅炉热效率的因素，得出较先进的运行经验数据，作为设计锅炉和改进运行的可靠依据。2025/6/222Boilerefficiencyistheratioofenergyoutputtoenergyinputandisusuallyexpressedasapercentage.Theoutputtermforasteamgeneratoristheenergyabsorbedbytheworkingfluidthatisnotrecoveredwithinthesteamgeneratorenvelope.Itincludestheenergyaddedtothefeedwateranddesuperheatingwatertoproducesaturated/superheatedsteam,reheatsteam,auxiliarysteamandblowdown.

Itdoesnotincludetheenergysuppliedtopreheattheenteringairsuchasairpreheatercoilsteamsuppliedbythesteamgenerator.Theenergyinputtermisthemaximumenergyavailablewhenthefueliscompletelyburned,i.e.,themassflowrateoffuel,MRF,multipliedbythehigherheatingvalueofthefuel.Thisisconventionallyexpressedas:3.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率(p10-17)2025/6/223IntheU.S.,itiscustomarytoexpresssteamgeneratorefficiencyonahigherheatingvaluebasis.Steamgeneratorefficiencymayalsobeexpressedonalowerheatingvaluebasis(commoninEurope).Forthesamemassflowrateoffuel,theLHVefficiencymaybe3to10percentagepointshigherthantheHHVefficiency,dependingupontheamountofH2andH2Ointhefuel.Whencomparingsteamgeneratorefficiencyand/orplantheatrate,theymustbeonthesamebasis,i.e.,HHVorLHV.Efficiencymaybedeterminedbymeasuringthemassflowrateoffuelandsteamgeneratoroutput,whichisreferredtoastheinput-outputmethod(正平衡)theenergybalancemethod

(反平衡).Theenergybalancemethodisgenerallythepreferredmethod.Itisusuallymoreaccuratethantheinput-outputmethod.3.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率(p10-17)2025/6/224Accordingtothelawofconservationofenergy,forsteady-stateconditions,theenergybalanceonthesteamgeneratorenvelopecanbeexpressedas:QRFistheinputfromfuel,Btu/h,QROisthesteamgeneratoroutput,Btu/h,QHBistheenergyrequiredbyheatbalanceforclosure,Btu/h.Theheatbalanceenergyassociatedwiththestreamsenteringthesteamgeneratorenvelopeandtheenergyaddedfromauxiliaryequipmentpowerarecommonlyreferredtoasheatcredits,QRB(Btu/h).Theheatbalanceenergyassociatedwithstreamsleavingthesteamgeneratorandtheheatlosttotheenvironmentarecommonlyreferredtoasheatlosses,QRL(Btu/h).Thissteamgeneratorenergybalancemaybewrittenas:3.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率(p10-17)2025/6/225Thissteamgeneratorenergybalancemaybewrittenas:Whenlossesandcreditsareexpressedasafunctionofpercentinputfromfuel,QPLandQPB,theefficiencymaybecalculatedfrom:3.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率(p10-17)2025/6/2263.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率1.

Constituentsofboilerheatbalance

锅炉热平衡的组成以1kg固体燃料或液体燃料(气体燃料以1Nm3)为单位组成的热量平衡。(图3-1)1)Heatbalanceequation

锅炉热量平衡方程(单位kg燃料)Heatbalanceequation锅炉热量平衡方程百分数形式Q1QrQ2Q6Q3Q4Q5kJ/kg%2025/6/2273.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率1.

Constituentsofboilerheatbalance

锅炉热平衡的组成Qr:Heatinputbyanunitfuel

单位燃料带入锅炉的热量,kJ/kgQ1:Boilereffectiveheat

锅炉有效利用热量,kJ/kg；Q2:Heatlossduetoexhaustgas

排出烟气带走的热量,排烟热损失，kJ/kgQ3:Heatlossduetounburnedgas

未燃尽可燃气体所带走的热量，为气体不完全燃烧热损失,kJ/kg；Q4:Heatlossduetounburnedcarboninrefuse

未燃完的固体燃料所带走的热量，称为固体不完全燃烧热损失;Q5:Heatlossduetoradiation

锅炉散热损失，kJ/kg；Q6:Otherheatlosses

灰渣物理热损失及其他热损失，kJ/kg。2025/6/2283.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率1.

Constituentsofboilerheatbalance

锅炉热平衡的组成2)Heatinputbycombustionfuel

燃料带入锅炉的热量Qr2500:approximateenthalpyofsteaminfluegas,kJ/kga)Sensibleheatoffuel燃料的物理显热ir

(1)固体燃料应用基比热：

(2)液体燃料应用基比热b)heatinputbysteamatomization,Qzq

蒸汽带入热c)外来热量Qwlexternalheatspecificheat2025/6/2293.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率2.

Boilerefficiency

锅炉热效率1)Boilerefficiencybypositivebalance

锅炉正平衡热效率Boilereffectiveheatutilization锅炉有效利用热量Qgl，kJ/hB:fuelconsumption,燃料消耗量，kg/hkJ/kg2025/6/22103.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率2.

Boilerefficiency

锅炉热效率1)Boilerefficiencybypositivebalance

锅炉正平衡热效率Boilereffectiveheatutilizationperhour锅炉每小时有效利用热量QglkJ/h；W:watercontentinsaturatedsteam,%r:latentheatofsteam,kJ/kgI’’:enthalpyofsaturatedsteam2025/6/22113.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率2.

Boilerefficiency

锅炉热效率1)Boilerefficiencybypositivebalance

锅炉正平衡热效率Boilereffectiveheatutilizationperhour锅炉每小时有效利用热量QglkJ/s；2025/6/22123.3Boilerheatbalanceandboilerefficiency

§3-3锅炉热平衡的组成及锅炉效率2.

Boilerefficiency

锅炉热效率2)Boilerefficiencybynegativebalance

锅炉反平衡热效率Calculatetheheatlossesofboiler通过计算各项损失热效率BoilergrossefficiencyBoilernetefficiency2025/6/22133.3Boilerheatbalanceandboilereff