9 replies to this topic

[aditya9]

Please help me in finding flow rate of flue gas whose flue gas composition is O₂₌13.9%,CO=0.002% &
CO₂=4.68%
please do the hurry........
aditya

[fallah]

Please help me in finding flow rate of flue gas whose flue gas composition is O₂₌13.9%,CO=0.002% &
CO₂=4.68%
please do the hurry........
aditya

From which stack? Which fuel combustion?...?....?

Edited by fallah, 20 December 2011 - 07:34 AM.

[Absolute Zero]

Aditya9 it is not possible to calculate the flow rate of any gas with only having the composition,

[sheiko]

Aditya9,

Flue gas flowrate = Air flowrate + Fuel flowrate

Edited by sheiko, 20 December 2011 - 01:32 PM.

[fallah]

Aditya9,

Flue gas flowrate = Air flowrate + Fuel flowrate

sheiko,

At least you could say; Flue gas flowrate={Excess air+Gaseous mixture (resulting from combustion)+not combusted fuel (gaseous)} flowrate

Fallah

Edited by fallah, 21 December 2011 - 05:08 AM.

[sheiko]

sheiko,

At least you could say; Flue gas flowrate={Excess air+Gaseous mixture (resulting from combustion)+not combusted fuel (gaseous)} flowrate

Fallah

Fallah, I believe my MASS balance is correct in first approximation, except that I could have added atomising steam (if Fuel is liquid).

Moreover I disagree with yours as "not combusted" fuel cannot remain after a complete combustion, revealed by the presence of excess air (as you have written).

Regards.

[fallah]

Fallah,I believe my MASS balance is correct in first approximation, except that I could have added atomising steam (if Fuel is liquid). Moreover I disagree with yours as "not combusted" fuel cannot remain after a complete combustion, revealed by the presence of excess air (as you have written). Regards.

sheiko,

Thoretically/ideally and provided that complete atomizing would be done for liquid (in real world doesn't occur) and for 100% complete combustion your mass balance could be right.
Again, complete combustion without excess air is an ideal phenomena and in real world we may have unburned fuel in its reaction with stochiometric value of the air due to some reasons such as the temperature be lower than needed, presence of impurities in fuel, uncomplete atomizing,.....

Fallah

Edited by fallah, 21 December 2011 - 06:39 AM.

[kkala]

A. I think sheiko is right concerning mass balance, irrespectively of introduced air quantity (stoiciometric or not). Mass of resulting flue gases will be mass of fuel+air (OK, add atomizing steam, though negligible).
fallah is right in the way to estimate flue gas composition, which is useful in calculating volumetric flow rate at certain flue gas temperature. The value O2=13.9% (v/v? on dry basis?) indicates excess air, so complete combustion. CO=0.002% is a small quantity (25 mg/Nm3) that could be created even at excess air. Typical CO content in flue gases is 100 ppm = 0.01% v/v, and typical O2 content 2% - 6% v/v http://www.keison.co...isfluegas.shtml , so 13.9% looks high.
B. Suppose that fuel complete composition(%C, H, S, etc, w/w) is known, as well as its mass flow to burners:
1. If excess air is given, flue gas composition and molar flow rates* can be estimated
2. If flue gas (precise) full composition is given, excess air and molar flow rates* can be estimated.
In both above options unburnt fuel is assumed as 0, sustained by the excess air.
Examples can be found searching the forum, e.g. http://www.cheresour...ue-gas-quantity,

*from molar flow rate of each component, total mass flow rate of flue gas and total volumetric flow rate at a specific temperature can be estimated.

Edited by kkala, 21 December 2011 - 12:18 PM.

[sheiko]

Fallah, I agree that other molecules than water, carbon dioxide and nitrogen will probably flow in the stack, but I wonder what is the relevancy of this fact in the perspective of quickly estimate the flue gas flowrate? I mean, could you please tell us how to simply quantify the amount of unburnt material from a combustion reaction?

Regarding the supposed excess oxygen content of 13.9%, it rather looks like the excess air content, which value is around 5 (= 100/21) times the % O2.

Edited by sheiko, 25 December 2011 - 05:30 PM.

[hayyimubarok]

Please help me in finding flow rate of flue gas whose flue gas composition is O₂₌13.9%,CO=0.002% &
CO₂=4.68%
please do the hurry........
aditya

Dear Aditya,

It couldn't be calculated, because the data only for mol/ volume fraction. there is no partial rate that must be identified.