Mass & Energy Balance Question Help

zombieguy

I would appretiate help with the following 2 questions, I think I've got must of the first one right (Or went off t a tangent) but I don't now where to start on the second question

1a) Calculate the flue gas composition if 100 kmol h^-1 of a gas whose composition is given below are burnt with 10% excess air.
b) Calculate the mass flowrate of air used
CO-12.6%
CO₂-2.6%
H₂-41.6%
CH₄-26.6%
O₂-1.9%
N₂14.7%

2) Ethanol dehydration reaction is carried out in a reactor with the feed entering at 300^oC
C₂H₅OH --> CH₃CHO + H₂
This is an endothermic reaction. The feed contain 90% mole % ethanol and the balance acetaldehyde. Heat is added to keep the temprature from dropping too rapidly. With a fraction of 30% and outlet temprature of 100^oC.
Calculate the heat addition rate per 253 mol of the feed gas.
Below are the heat capacity data (KJ/mol-C)
C_p [C₂H₅OH] = 0.11
C_p [CH₃CHO] = 0.08
C_p [ H₂] = 0.029
Heat of reaction = 68.95 J

Take Reference Temprature = 25^oC


Here my Working out for question 1:
12.6CO₂+6.3O₂ -> 12.6CO₂
41.6H₂+20.8O₂ -> 41.6H₂O
26.6CH₄+53.2O₂ -> 26.6CO₂+53.2H₂O

Total CO₂= 12.6+2.6+26.6=41.8
Total H₂O=41.6+53.2=94.8
Total O₂=(6.3+20.8+53.2)X1.1+1.9=90.23
Total N₂=((79/21)X88.33)+14.7=346.99

After that i worked out the %'s eg. %CO₂(41.8/573.82)X100=7.3% (I'd put all of my % up but I'm not sure I'm right upto this point at best)

1b) mrXmoles=mass
O2, 32X88.33=2826.56
N2, 28X332.3=9304.04
Total=12130.65

zombieguy

I've sorted out question 1 but I still need help with question 2.
Any help still welcome.

zombieguy

Help with the language used would also be helpful, thank you

lewdtenant

Ethanol dehydration means that H2 is being removed from ethanol, which is stated in the reaction.

So, do you know the difference between an endothermic and an exothermic reaction?
One type of reaction "absorbs heat" and the other "gives off heat," which means that one type of reaction will feel cold and one will feel hot. Which one is which?

Well from the question you can gather that an endothermic reaction will "absorb heat" and so it makes the ambient cool. Every material has some ability to store heat: this is the heat capacity. Here you have been given specific heat capacities (note the units) which is the amount of heat required to raise one mole of substance one degree C. The heat of reaction is the enthalpy change that occurs during the reaction (on a molar basis).

I was planning on continuing, but I'm pretty tired.. hope this helps you.. I didn't check your work for #1 btw.