11 replies to this topic

[hashbal]

Hi Dear,
Please i need help in a flue gas analysis for gas power plants..i want to know how to calculate the percentage composition of CO2, N2,O2, and H2O vapor in the flue gas.. Assuming complete combustion and using air as oxidant..is their a specific amount of excess air to be used?i know many combustion calculators online but i need to show the working..

Thank You

[sheiko]

Hi Dear,
Please i need help in a flue gas analysis for gas power plants..i want to know how to calculate the percentage composition of CO2, N2,O2, and H2O vapor in the flue gas.. Assuming complete combustion and using air as oxidant..is their a specific amount of excess air to be used?i know many combustion calculators online but i need to show the working..

Thank You

Hi,

There is a procedure in the attached article, that is applicable when using fuel gas as combustible.

Attached Files

•  SyncrudeReprint.pdf   281.44KB   307 downloads

Edited by sheiko, 28 July 2011 - 07:43 PM.

[Padmakar Katre]

Hi,

This is a simple process calculation. You need to have the fuel details (liquid and gaseous) such as the C, H and S content. Based on the reactions involved (stiochiometric) you can calculate the composition of the flue gas. Excess air if any, used should be considered. Find herewith an attached handy calculations procedure. If you have further doubts please do let me know.

Attached Files

•  Combustion Calculations.pdf   354.94KB   348 downloads

[hashbal]

thanks alot

[hashbal]

Padmakar S Katre:

I appreciate, thank you

[kkala]

In addition to previous useful posts, as an example of stoichiometry combustion calculation, you can look at http://www.cheresour...h__1#entry35836, attached "Gascomb.xls". Either case A or case B can make an example of burning gas at a given excess of air. Same procedure can be applied for liquid fuels.

[hashbal]

Thanks alot

In addition to previous useful posts, as an example of stoichiometry combustion calculation, you can look at http://www.cheresour...h__1#entry35836, attached "Gascomb.xls". Either case A or case B can make an example of burning gas at a given excess of air. Same procedure can be applied for liquid fuels.

[Skyline]

Dear all,

Sorry for intruding into this topic. I want to know how do i calculate flue gas composition of fuel oil firing if i don't have the composition of C and H content of the oil? I only have the laboratory analysis such as: heating value, viscosity, sulphur content, CCR, and distillation (assay) because it's refinery fuel oil. Is there any way to convert those data into C and H composition? Thank you very much for your help.

Best regards,


EY

[Padmakar Katre]

Dear all,

Sorry for intruding into this topic. I want to know how do i calculate flue gas composition of fuel oil firing if i don't have the composition of C and H content of the oil? I only have the laboratory analysis such as: heating value, viscosity, sulphur content, CCR, and distillation (assay) because it's refinery fuel oil. Is there any way to convert those data into C and H composition? Thank you very much for your help.

Best regards,


EY

Hi,
Google with the "Elemental analysis of Crude" or "Elemental analysis of fuel oil".

[kkala]

..how do i calculate flue gas composition of fuel oil firing if i don't have the composition of C and H content of the oil? I only have the laboratory analysis such as: heating value, viscosity, sulphur content, CCR, and distillation (assay) because it's refinery fuel oil. Is there any way to convert those data into C and H composition?

You can measure fuel oil specific gravity (sg), then use correlations relating sg or heating value to composition for an approximate composition result. For instance, following could be useful.
1. Perry (Chemical Engineers' handbook, 7th ed, 1997) reports %H=26-15*sg, or more accurate correlations depending on sg (sg=oil density/water density). I had applied it once on the fuel oil part, after subtracting water & sediment, ash, O, organic N (interpretation); having found %H, %C=100-%H on mentioned fuel oil part. But this correlation holds for fuels free of S; found %C could be reduced by known %S (interpretation).
2. Table 27-6 of Perry has analysis of several fuel oils, that can be used as a rough guide in combination with the above.
3. Seeing that LHV is known, formulas can be used to verify fuel composition and making some corrections, if needed. One such formula (used in 1997) was rather precise compared to published data, but I cannot find it. Following http://chestofbooks....ific-Value.html, LHV (kcal/kg) = %C*8080+(%H-%O/8)*34460+%S*2217, where the term of S has been added (standard heat of SO2 formation=-70.94 kcal/kgmol).
Terms of these formulas differ somehow, probably in an effort to represent experimental values better. Based on Perry (Heats of formation, Table 2-220), previous formula becomes LHV (kcal/kg) = %C*7800+%H*28900+%S*2217, while formula is also a bit different in http://www.eng-tips....d=301699&page=1.
4. So one has to consider all available data and formulas, together with some engineering judgment, to arrive at a fuel composition as precise as possible; oxygen and organic nitrogen content in fuel oil cannot be estimated by formulas (to my knowledge), these had better be directly measured by analysis. Client had given organic nitrogen once (by analysis or estimate??), but not oxygen content of fuel oil. I wonder why an analysis for fuel oil composition is so hard to be realized by refinery laboratory (there will be variations from sample to sample, but still one analysis would be useful).
Note: 15% excess air is usual for fuel oil burning at nominal capacity of boiler. Excess air increase for lower capacities.

Edited by kkala, 30 July 2011 - 02:18 AM.

[Skyline]

..how do i calculate flue gas composition of fuel oil firing if i don't have the composition of C and H content of the oil? I only have the laboratory analysis such as: heating value, viscosity, sulphur content, CCR, and distillation (assay) because it's refinery fuel oil. Is there any way to convert those data into C and H composition?

You can measure fuel oil specific gravity (sg), then use correlations relating sg or heating value to composition for an approximate composition result. For instance, following could be useful.
1. Perry (Chemical Engineers' handbook, 7th ed, 1997) reports %H=26-15*sg, or more accurate correlations depending on sg (sg=oil density/water density). I had applied it once on the fuel oil part, after subtracting water & sediment, ash, O, organic N (interpretation); having found %H, %C=100-%H on mentioned fuel oil part. But this correlation holds for fuels free of S; found %C could be reduced by known %S (interpretation).
2. Table 27-6 of Perry has analysis of several fuel oils, that can be used as a rough guide in combination with the above.
3. Seeing that LHV is known, formulas can be used to verify fuel composition and making some corrections, if needed. One such formula (used in 1997) was rather precise compared to published data, but I cannot find it. Following http://chestofbooks....ific-Value.html, LHV (kcal/kg) = %C*8080+(%H-%O/8)*34460+%S*2217, where the term of S has been added (standard heat of SO2 formation=-70.94 kcal/kgmol).
Terms of these formulas differ somehow, probably in an effort to represent experimental values better. Based on Perry (Heats of formation, Table 2-220), previous formula becomes LHV (kcal/kg) = %C*7800+%H*28900+%S*2217, while formula is also a bit different in http://www.eng-tips....d=301699&page=1.
4. So one has to consider all available data and formulas, together with some engineering judgment, to arrive at a fuel composition as precise as possible; oxygen and organic nitrogen content in fuel oil cannot be estimated by formulas (to my knowledge), these had better be directly measured by analysis. Client had given organic nitrogen once (by analysis or estimate??), but not oxygen content of fuel oil. I wonder why an analysis for fuel oil composition is so hard to be realized by refinery laboratory (there will be variations from sample to sample, but still one analysis would be useful).
Note: 15% excess air is usual for fuel oil burning at nominal capacity of boiler. Excess air increase for lower capacities.

Thank you very much kkala, a very thorough explanation I think. It really helps.

[kkala]

Concerning LHV from elementary analysis, presented in kkala's post of 30 Jul 2011, a correction should be pointed out: %H in the formulas should be replaced by %H-%O/8, where %H or %O are considered w/w. This because O is assumed already combined with H (8 grams O with 1 gram H), so the corresponding H cannot be burnt further to produce heat.
Therefore formula LHV (kcal/kg) = %C*7800+%H*28900+%S*2217 should be corrected to
LHV (kcal/kg) = %C*7800+(%H-%O)*28900+%S*2217.