1.On a mass basis a mixed gas stream consists of 3%nitricoxide,4%sulfurdioxide,3
ID: 701687 • Letter: 1
Question
1.On a mass basis a mixed gas stream consists of 3%nitricoxide,4%sulfurdioxide,39% carbon dioxide,and the balance nitrogen.Determine the molar composition and the ideal gas heat capacity of this mixed stream. 2.The mixed gas stream of problem 1is fed to a waste heat boiler. In the boiler, heat is transferred from this gas stream to a water stream, which is fed to the boiler at a saturated liquid at 25°C. The gas is fed at a rate of 2200 liters at STP per minute, and it exits the waste heat boiler at 75°C. The water, which is fed at a ratio of 0.215moles of water per mole hot gas, is heated by the gas such that it creates saturated steam at 5.0 bar. Assuming that the boiler is well insulated, determine the inlet temperature of the mixed gas stream.(You are likely to need a solver to find your answer). 3. What assumption concerning a heat effect did you invoke when you calculated the change inenthalpy of the mixed gas stream in problem 2? 4.n-Butaneis combusted completely in a furnace, and a stream of air is used as the oxygen source.a)What is the minimum air/fuel (n-butane)molar ratio required for the complete combustion of n-butane?b)What is that ratio when expressed on a mass basis?c)Calculate the standard heat of reaction,Hrxn,for the complete combustion of n-butane.
Explanation / Answer
Ans 4
Complete combustion reaction of n-butane
C4H10 (g) + (13/2)(O2 + 3.76 N2) (g) = 4CO2(g) + 5H2O(g)
Part a
From the stoichiometry of the reaction
1 mol of C4H10 require = (13/2)*(1+3.76) = 30.94 mol of air
minimum air/fuel (n-butane)molar ratio required for the complete combustion of n-butane
= 30.94/1 = 30.94 mol air/mol fuel
Part b
minimum air/fuel (n-butane) mass ratio required for the complete combustion of n-butane
= (30.94 mol air x 29 g/mol) /(1 mol fuel x 58g/mol)
= 15.5 g air/g fuel
= 15.5 kg air / kg fuel
Part C
Heat of reaction = sum of heat of formation of products - sum of heat of formation of reactants
= (5* Hf H2O) + (4* Hf CO2) - (0) - (1* Hf C4H10)
= 5*(-241.8) + 4*(-393.5) - 0 - (-126.2)
H rxn = - 2656.8 kJ/mol
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