材料热力学习题答案1

b?H??CPdT??a?bTdT?[aT?T2]T2982ba(700?298)?(7002?2982)?121132ba(1000?298)?(10002?2982)?228032Solution a?35.62

b??0.011CP?35.62?0.011TT?H298?35.62(T?298)?0.0055(T2?2982)

9.A fuel gas containing 40% CO, 10% CO2, and the rest N2 (by volume) is burnt completely with air in a furnace. The incoming and ongoing temperatures of the gases in the furnace are 773K and 1250K,respectively. Calculate (a) the maximum flame temperature and (b) heat supplied to the furnace per cu. ft of exhaust gas (1.9)

?Hf,298,CO??110458J/mol?H0f,298,CO20??393296J/mol

CP,CO?28.45?3.97?10?3T?0.42?105T?2(J/molK)CP,CO2?44.35?9.20?10?3T?8.37?105T?2(J/molK)CP,O2?19.92?4.10?10T?1.67?10T(J/molK)CP,N2?29.03?4.184?10?3T(J/molK)

Solution

?35?2

2CO?O2?2CO2when1molefuelneed1moleair(N2/O2?4)thenreationCO?20%CO2?5%N2?65%O2?10%productionCO2?27.8%N2?72.2%?Hi,298???Hf,298,rni???Hf,298,pni?393296?110458?282838(J/mol)00(a)Cp,r??Cp,p,ini?0.2CP,CO?0.05CP,CO2?0.65CP,N2?0.1CP,O2?28.77?4.38?10?3T?0.67?105T?2(J/molK)Cp,r??Cp,p,ini?0.278CP,CO2?0.722CP,N2?33.28?5.58?10?3T?0.19?105T?2(J/molK)?H???Hi,298ni??(?Cp,p,ini??Cp,r,ini)dT?282838?0.2??TT298(33.28?5.58?10?3T?0.19?105T?2)?0.9dT??28.77?4.38?10?3T?0.67?105T?2dT733?28283.8?2?(28.77T?2.19?10?3T2?0.67?105T?1)733298?(1.18T?0.321T2?0.499T?1)T298?0T??

?H???Hi,298ni??(?Cp,p,ini??Cp,r,ini)dT?282838?0.2??TT298(33.28?5.58?10?3T?0.19?105T?2)?0.9dT?1250?35?228.77?4.38?10T?0.67?10TdT??28283.8?2?(28.77T?2.19?10?3T2?0.67?105T?1)1250298?(1.18T?0.321T2?0.499T?1)T298?0T?(b)1250Q298??282838?0.2??1250Q298??282838?0.2??12502981250

(33.28?5.58?10?3T?0.19?105T?2)?0.9dT(33.28?5.58?10?3T?0.19?105T?2)?0.9dT298

10. (a) for the reaction CO?1O2?CO2,what is the enthalpy of reaction (?H0) at 298 K ? 2(b) a fuel gas, with composition 50% CO, 50% N2 is burned using the stoichiometric amount of air. What is the composition of the flue gas?

(c) If the fuel gas and the air enter there burner at 298 K, what is the highest temperature the

flame may attain (adiabatic flame temperature)? DATA :standard heats of formation ?Hf at 298 K (1.10)

CO??110000(J/mol)CO2??393000(J/mol)

Heat capacities [J/(mol K)] to be used for this problem N2=33, O2=33, CO=34, CO2=57 Solution

(a)?H0???Hf,298,rni???Hf,298,Pni??110000?393000?283000(J/mol)000.5?22.2%,N2%?66.6%,O2%?11.1%1?0.25/0.222.2productCO2%??25%,N2%?75%,100?11.1(C)Cp,P??Ci,p,PXi?33?0.666?33?0.222?34?0.111?33(J/mol?K)(b)fuelCO%?Cr,P??Ci,r,PXi?57?0.25?33?0.75?39(J/mol?K)?H??H0??npCp,PdT?0283000?0.222?(0.889?39)(T?298)?0T?2110(K)

11.a particular blast furnace gas has the following composition by (volume): N2=60%, H2=4, CO=12%, CO2=24%

(a) if the gas at 298K is burned with the stochiometric amount of dry air at 298 K, what is the composition of the flue gas? What is the adiabatic flame temperature? (b) repeat the calculation for 30% excess combustion air at 298K

(C)what is the adiabatic flame temperature when the blast furnace gas is preheated to 700K (the dry air is at 298K)

(d) suppose the combustion air is not dry ( has partial pressure of water 15 mm Hg and a total pressure of 760 mm Hg) how will the flame temperature be affected? DATA(k J/mol) （1.11）

?Hf(kJ/mol)FOR CO2 CO ?110.523H2O(g)?393.513CO2N2,O2Solution

FORCOCP[J/mol?K]33575034

1(a)CO?O2?CO221H2?O2?H2O212CO%??8.6%,CO2%?17.1%,H2%?2.9%,O2%?5.7%,N2%?65.70?8/0.2?H??xi[?Hi??(?CP,p,ini??CP,r,ini)dT]??CP,iXi0?0.086[393513?110523?(57?34?0.5?33)?T]?0.029[241604?(50?34?0.5?29)?T]??CP,r,ini?T?031343?825(K)38T?1122(K)12(b)CO%??7.9%,CO2%?15.8%,H2%?2.6%,O2%?6.8%,N2%?66.80?1.3?8/0.2?T??H??xi[?Hi??(?CP,p,ini??CP,r,ini)dT]??CP,iXi0?0.079[393513?110523?(57?34?0.5?33)?T]?0.026[241604?(50?34?0.5?29)?T]??CP,r,ini?T?028637?754(K)38T?1052(K)?T?