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CO2 Emission

01/06/2010 2:06 AM

How to stipulate and calculate the CO2 emission from flaring system? Is there any engineering practice and simple formula for reference?

Thanks

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#1

Re: CO2 emission

01/06/2010 3:34 AM

This is a matter of balancing a chemical reaction equation. X molecules of flared fuel + y molecules of O2 ---> z molecules of H2O + w molecules of CO2. Fiddle with this until the total atoms of each element equalize. Compare molecular weights × number of molecules of each compound. Whatever other units you are using (pounds, kilograms, tons, etc.) will be in the same proportions.

For instance, let's burn some propane:

x C4H10 + y O2 ---> z H2O + w CO2.

By trial-and-error, oxidation/reduction, simultaneous equations, or whatever hook-or-crook means, eventually you get:

2 C4H10 + 13 O2 ---> 10 H2O + 8 CO2 (8 C, 20 H, 26 O on each side)

For atomic weights, H = 1, C = 6, O = 8 (ignoring the fractions).

Plugging in molecular weights, we have:

2 (34) + 13 (16) ---> 10 (10) + 8 (22); hence

68 propane + 208 oxygen ---> 100 water + 176 carbon dioxide.

Thus, burning 68 mass units of propane gives 176 mass units of carbon dioxide.

[In general, longer-chain hydrocarbons produce proportionately more CO2.]

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#2

Re: CO2 emission

01/06/2010 3:40 AM
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#3

Re: CO2 emission

01/06/2010 5:14 AM

To all, I apologize for some errors in my previous post. Instead of using atomic weights, I used atomic numbers in part of the explanation. (That'll teach me to write too late in the evening!).

The specifics will need to be corrected, which I will do, but the main idea will be about the same. Now it is even later (and I sleepier); see ya tomorrow.

Thanks to Kyzine for catching this.

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#4

Re: CO2 Emission

01/06/2010 10:15 PM

Correcting My earlier post #1 by using atomic/molecular weights:

H = 1, C = 12, O = 16 (ignoring the fractions).

Plugging in molecular weights, we have:

2 (58) + 13 (32) ---> 10 (18) + 8 (44); hence

116 propane + 416 oxygen ---> 180 water + 352 carbon dioxide.

Thus, burning 116 mass units of propane gives 352 mass units of carbon dioxide.

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#5
In reply to #4

Re: CO2 Emission

01/07/2010 6:36 AM

Not bad! only thing now is C4H10 is butane, not propane. Propane is C3H8.

Cheers.......Codey

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#6

Re: CO2 Emission

01/07/2010 9:37 PM

Dear friend

We can simplified the combustion reaction by assuming

1. The hydrocarbon flared gas is paraffinic

2. hydrogen gas is negligible

With above assumption, the kg/h of CO2 released can be approximated by equation below:

W = [(MW - 2)/14] x [44/22.414] x Q

where

MW is the gas mixture molecular weight

Q is the flared gas flowrate in NM3/h

W is the flowrate of CO2 in kg/h

I purposely left the original numbers intact so that you can figure out what the numbers stand for.

Hope the above is what you are looking for.

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