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### Topic: Mass & Energy Balance Questions (There are 2)  (Read 4993 times)

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#### zombiemaster

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• Mole Snacks: +0/-0 ##### Mass & Energy Balance Questions (There are 2)
« on: December 12, 2009, 12:32:12 PM »
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 300oC
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 100oC.
Calculate the heat addition rate per 253 mol of the feed gas.
Below are the heat capacity data (KJ/mol-C)
Cp [C2H5OH] = 0.11
Cp [CH3CHO] = 0.08
Cp [ H2] = 0.029
Heat of reaction = 68.95 J

Take Reference Temprature = 25oC

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

#### zombiemaster

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• Mole Snacks: +0/-0 ##### Re: Mass & Energy Balance Questions (There are 2)
« Reply #1 on: December 14, 2009, 11:52:20 AM »
I've sorted out question 1 but I still need help with question 2.
Any help still welcome.

#### zombiemaster

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• Mole Snacks: +0/-0 ##### Re: Mass & Energy Balance Questions (There are 2)
« Reply #2 on: December 16, 2009, 04:04:59 PM »
Help with the language used would also be helpful, thank you

#### eugenedakin

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• Gender: • My desk agrees with the law of entropy ##### Re: Mass & Energy Balance Questions (There are 2)
« Reply #3 on: December 18, 2009, 06:23:28 PM »
Hi zombiemaster,

For the first question, you need to calculate the amount of methane from combustion of 10% excess air.

To start out, please show the reaction stoichiometry, then we will take the next step.

After were finished this question, then we'll start on the next one.

Best wishes,

Eugene

There are 10 kinds of people in this world: Those who understand binary, and those that do not.