Exercise 1 Text Adiabatic flmae temperature

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1 Department of Energy Politecnico di Milano Via Lambruschini 4 - 20156 MILANO Exercises of “Fundamentals of Chemical Processes” Prof. Gianpiero Groppi EXERCISE 1 Adiabatic flame temperature for the combustion of propane The c ombustion of propane with air is carried out in an adiabatic reactor: C3H8 + 5 O2 → 3 CO2 + 4 H2O Considering the data given below, calculate the temperat ure of the exhaust gas stream at the outlet of the reactor (TOUT) in the following cases: 1) stoichiometric feed of the reactants 2) 30% excess air 3) with reference to the case with 30% excess air , assume that, due to ill-combustion, CO is present amon g the exh aust gases with a selectivity of 10% with respect to the moles of C converted. Data: C3H8 stream: T = 25°C P = 1 atm ∆H°C C3H8 (25°C) = -2043 kJ/mol Air stream: T = 25°C P = 1 atm R.H. = 60% P SAT H2O(25°C) = 3.169 kPa Stream #2: T OUT = ? P = 1 atm ∆H°C CO (25°C) = -283 kJ/mol Hypothesis: Adiabatic reactor 2 Species a b C N2 3.280 5.930E-04 -4.000E+03 CO2 5.457 1.045E-03 -1.157E+05 H2O 3.470 1.450E-03 1.210E+04 O2 3.639 5.060E-04 -2.270E+04 CO 3.376 5.570E-04 -3.100E+03 K T inK mol J T cT b a R Ci i i gas i P          2, CP,i equation and parameters taken from J.M. Smith, H.C. Van Ness, M. M. Abbott, Introduction to Chemical Engineering Thermodynamics, 7th edition, McGraw Hill (2005). Solution Case 1 First, the material balance is written for each of the sp ecies involved in the reaction. Then, a basis is set for the calculation. The basis can be chosen arbitrarily. In this case, it is reasonable to choose 1 mol/s inlet propane as the basis. The amount of inlet O 2 is estimated from the reaction stoichiometry and is equal to 5 mol/s. The amount of inlet N 2 going in the reactor together with air (0.21% O 2 and 0.79% N 2…