Problem 4) Combustion For some cogeneration systems, the fuel is "liquid petroleum gas" (LPG). This fuel is a mixture of several gases, but typically is composed mostly of propane (C3H8) and butane (C4H10). For this problem, assume that the "LPG" consists (by volume) of 25% propane and 75% butane. Use these LHVs: propane is 46.28 MJ/kg and butane is 45.27 MJ/kg. a) Determine the average molecular formula, CxHy. Determine the average lower heating value (MJ/kg). (Hint: you need mole fractions for the molecular formula, and you need mass fractions for the average LHV.) b) For 12% excess air (by volume) with this fuel, determine the balanced reaction statement, the air-fuel mass ratio, and the equivalence ratio. Confirm that your work is correct by determining and comparing the reactant and product masses. How do these numbers compare to pure propane and pure butane? (Hint: you need to determine the stoichiometric case first.) c) For part "b," for 12% excess air, determine the "dry" and "wet" mole fractions of all product species (excluding H₂O).
Problem 4) Combustion For some cogeneration systems, the fuel is "liquid petroleum gas" (LPG). This fuel is a mixture of several gases, but typically is composed mostly of propane (C3H8) and butane (C4H10). For this problem, assume that the "LPG" consists (by volume) of 25% propane and 75% butane. Use these LHVs: propane is 46.28 MJ/kg and butane is 45.27 MJ/kg. a) Determine the average molecular formula, CxHy. Determine the average lower heating value (MJ/kg). (Hint: you need mole fractions for the molecular formula, and you need mass fractions for the average LHV.) b) For 12% excess air (by volume) with this fuel, determine the balanced reaction statement, the air-fuel mass ratio, and the equivalence ratio. Confirm that your work is correct by determining and comparing the reactant and product masses. How do these numbers compare to pure propane and pure butane? (Hint: you need to determine the stoichiometric case first.) c) For part "b," for 12% excess air, determine the "dry" and "wet" mole fractions of all product species (excluding H₂O).
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Transcribed Image Text:Problem 4) Combustion
For some cogeneration systems, the fuel is "liquid petroleum gas" (LPG). This fuel is a mixture of several gases,
but typically is composed mostly of propane (C3Hs) and butane (C4H10). For this problem, assume that the "LPG"
consists (by volume) of 25% propane and 75% butane. Use these LHVs: propane is 46.28 MJ/kg and butane is
45.27 MJ/kg.
a) Determine the average molecular formula, CxHy. Determine the average lower heating value (MJ/kg).
(Hint: you need mole fractions for the molecular formula, and you need mass fractions for the average
LHV.)
b) For 12% excess air (by volume) with this fuel, determine the balanced reaction statement, the air-fuel
mass ratio, and the equivalence ratio. Confirm that your work is correct by determining and comparing
the reactant and product masses. How do these numbers compare to pure propane and pure butane? (Hint:
you need to determine the stoichiometric case first.)
c)
For part "b," for 12% excess air, determine the "dry" and "wet" mole fractions of all product species
(excluding H₂O).
d) For this fuel in another situation, the products yielded "dry" mole fractions: yco2 = 3.1%, yco = 13.8%,
and yH2 = 6.9%. Determine the balanced reaction statement, the air-fuel mass ratio, and the equivalence
ratio.
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