8.3 Combustion Heat & Production Heat8.3.2CombustionHeat&Thermo-effectofReactionCombustion Enthalpy:△hThethermo-effectof 1molefuel during completecombustion at standard condition.Its absolute value is heatvalue.C→CO2Gas:LowHeat ValueH→H,Omeans:Liquid:HighHeat ValueS-→SON→N2Metal→Dissociative State
8.3 Combustion Heat & Production Heat 8.3.2 Combustion Heat & Thermo-effect of Reaction Combustion Enthalpy: The thermo-effect of 1 mole fuel during complete combustion at standard condition. Its absolute value is heat value. means: 2 2 2 2 C CO H H O S SO N N Metal Dissociative State → → → → → Gas: Low Heat Value Liquid: High Heat Value 0 c h
= AH°= H- H=n,Ah-n,hRMolarenthalpyatTotal enthalpyofstandardconditionreactandproductatstandard conditionh° = -NhoO,° - En,ah℃ -n,h'1at any temperature, the molar enthalpyh = -△h° +C...dT.017298thermo-effect of chemical reaction:Q, =En,Ah, -En,hDR
0 0 0 0 0 0 p P R i i i i P R Q H H H n h n h = = − = − Total enthalpy of react and product Molar enthalpy at standard condition at standard condition 0 0 c h h = − at any temperature, the molar enthalpy: 0 298 d T c pm h h C T = − + thermo-effect of chemical reaction: p i i i i P R Q n h n h = − 0 0 0 p i ci i ci R P Q n h n h = −
8.3.2 Combustion Heat & Thermo-effect of ReactionExample:PropaneDecomposition△h° = -2220 kJ/kmolC,H.+50,=3CO,+4H,0Aho= -1411 kJ/kmolC,H4 +302 ==2CO, +2H,0(1)△h = -890 kJ/kmolCH +2O,==CO, +2H,0(2)(1)一(2)一(3)(3)C,H,=C,H4 +CH4Ah° = Ah% - h --△h=-2220±1411±890= 81kJ/kmol
8.3.2 Combustion Heat & Thermo-effect of Reaction Example: Propane Decomposition 0 3 8 2 2 2 1 0 2 4 2 2 2 2 0 4 2 2 2 3 C H +5O ==3CO +4H O 2220 kJ/kmol C H +3O ==2CO +2H O 1411 kJ/kmol CH +2O ==CO +2H O 890 kJ/kmol c c c h h h = − = − = − (1) (2) (3) (1)－(2)－(3) C H C H CH 3 8 2 4 4 = + 0 0 0 0 1 2 3 2220 1411 890 81kJ/kmol c c c = − − h h h h = − + + =
8.3.3 Production Heat & Thermo-effect of Reaction2,=AH°= H, -H=n,Ah -n,hPRMolarenthalpy atTotal enthalpyofstandardconditionreact and productThe enthalpy of simple substance at standard condition iszero.Standard Production Enthalpy of Compound △hThe thermo-effect of 1mol compound produced by stablesimple substance at standard condition
8.3.3 Production Heat & Thermo-effect of Reaction 0 0 0 0 0 0 p P R i i i i P R Q H H H n h n h = = − = − Total enthalpy of react and product Molar enthalpy at standard condition The enthalpy of simple substance at standard condition is zero. Standard Production Enthalpy of Compound The thermo-effect of 1mol compound produced by stable simple substance at standard condition. 0 f h