Chemical Process Analysis - Mole Flow Rate

In summary: However, the professor calculated 1020/1.7 = 1020.3 moles of O2 per minute. The difference is due to the 15% of the reactions that use the oxygen supplied in excess.
  • #1
nobodyuknow
64
0

Homework Statement



120 mol/min of Propane (C3H8) is burned in the presence of air (21% O2 and 79% N2) in a furnace, two reactions occur:
Complete Combustion: 67%, propane is burned to CO2 and H2O
Incomplete Combustion: 18%, propane is burned to CO and H2O

Oxygen is supplied at 70% excess.

Homework Equations



%Excess = (In - Req'd *100%)/Req'd

Complete Combustion: 2C3H8 + 10O2 -> 6O2 + 8H2O
Incomplete Combustion: 2C3H8 + 7O2 -> 6O + 8H2O

The Attempt at a Solution



So for the complete combustion...
120 Moles C3H8 * 5 Required Moles of O2 * 67% Required for Complete Combustion = 402 Moles
So for the incomplete combustion...
120 Moles C3H8 * 3.5 Required Moles of O2 * 18% Required for Complete Combustion = 75.6 Moles

Total of 477.6 Moles required
Using %Excess Formula, you get, In = 477.6 * 0.7 + 477.6 = 811.92 Moles...

HOWEVER, my lecturer simply had:

120moles/min * 1.7 * 5/1 = 1020 moles of O2.

I'm extremely clueless to as how he got that.

Thanks
 
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  • #2
1. State what is "Kauzmann Paradox" and provide your own explanation (or solution) for the paradox and derive a unique explanation using different approaches.

2. If you observe a phase transition phenomenon in your own experiment, how to determine the whether the transition is binodal or spinodal?

3. Explain the origin of the friction when an elastic rubber ball is bouncing on a ground made of a crystalline material using an entropy analysis.

Thanks in Advance
Mallinath
 
  • #3
nobodyuknow said:

Homework Statement



120 mol/min of Propane (C3H8) is burned in the presence of air (21% O2 and 79% N2) in a furnace, two reactions occur:
Complete Combustion: 67%, propane is burned to CO2 and H2O
Incomplete Combustion: 18%, propane is burned to CO and H2O

Oxygen is supplied at 70% excess.

Homework Equations



%Excess = (In - Req'd *100%)/Req'd

Complete Combustion: 2C3H8 + 10O2 -> 6O2 + 8H2O
Incomplete Combustion: 2C3H8 + 7O2 -> 6O + 8H2O

The Attempt at a Solution



So for the complete combustion...
120 Moles C3H8 * 5 Required Moles of O2 * 67% Required for Complete Combustion = 402 Moles
So for the incomplete combustion...
120 Moles C3H8 * 3.5 Required Moles of O2 * 18% Required for Complete Combustion = 75.6 Moles

Total of 477.6 Moles required
Using %Excess Formula, you get, In = 477.6 * 0.7 + 477.6 = 811.92 Moles...

HOWEVER, my lecturer simply had:

120moles/min * 1.7 * 5/1 = 1020 moles of O2.

I'm extremely clueless to as how he got that.

Thanks

I think that you missed a very important bit of information.

Complete Combustion: 67%, propane is burned to CO2 and H2O
Incomplete Combustion: 18%, propane is burned to CO and H2O

This only accounts for 85% of the propane, so your calculations exclude the oxygen used in 15% of the reactions.

The professor took the flow rate of the propane, multiplied by the 70% excess (1.7) and then by the molar ratio (from the balanced chemical equation for complete combustion) (5 moles of O2 over 1 mole of propane).

The answer should be 1020 moles of O2 per minute.
 

Related to Chemical Process Analysis - Mole Flow Rate

1. What is Mole Flow Rate?

Mole flow rate is a measurement of the number of moles of a substance that flow through a given point in a system per unit time. It is typically denoted as ṅ and has units of mol/s or mol/min.

2. How is Mole Flow Rate calculated?

Mole flow rate can be calculated by multiplying the volumetric flow rate (in m3/s) by the molar concentration (in mol/m3) of the substance in the system. Alternatively, it can also be calculated by dividing the mass flow rate (in kg/s) by the molar mass (in kg/mol) of the substance.

3. What is the importance of Mole Flow Rate in Chemical Process Analysis?

Mole flow rate is an important parameter in chemical process analysis because it provides information about the rate at which reactants and products are being consumed and produced, respectively. It is also used to determine the efficiency of a chemical reaction and to design and optimize chemical processes.

4. What factors can affect Mole Flow Rate?

Mole flow rate can be affected by factors such as changes in temperature, pressure, and composition of the system. It can also be influenced by the presence of catalysts or inhibitors, and the type of reaction being studied.

5. How is Mole Flow Rate different from Mass Flow Rate?

Mole flow rate measures the number of moles of a substance flowing through a point in a system per unit time, while mass flow rate measures the mass of a substance flowing through a point in a system per unit time. They are related by the molar mass of the substance, but they provide different information about the system and are used for different purposes in chemical process analysis.

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