This document provides information about the composition and combustion analysis of various fuels including coal, natural gas, and ethanol. It gives the ultimate and proximate analyses, on different bases, of different coal and fuel samples. It also provides calculations for determining theoretical air requirements, excess air, heating values, combustion product compositions and volumes.

1. 1. An ultimate analysisof asample of coal as-receivedshowsthe followingresults:
C = 80.5% N2 = 1.5% W = 4.4%
H2 = 4.1% S = 1.2%
O2 = 3.0% A = 5.3%
a. Calculate the analysisonadry basisinpercent.
b. Calculate the analysisonacombustible basisin percent.
Constituent Coal “as-received” Coal “as dry” Coal “as combustible”
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
Ash
Moisture
80.50
4.10
3.00
1.50
1.20
5.30
4.40
84.21
4.29
3.13
1.57
1.26
5.54
xxxx
89.15
4.54
3.32
1.66
1.33
xxxx
xxxx
Total 100.00 100.00 100.00
2. The percentby massof the constituentsof coal as-receivedisgivenbythe followingultimate
analysis:
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
Ash
77.37
5.43
9.76
1.83
1.22
4.39
Total 100.00
From the proximate analysis,the moisture (W) is3.10%.
a. Convertthe ultimate analysisonadry basisin percent.
b. Convertthe ultimate analysisonacombustible basisinpercent.
c. Usingthe Dulong’sformula,calculatethe higherheatingvalue (HHV) of coal on(1) as-firedbasis
and (2) dry basisbasedon correctedultimate analysisof coal inkj/KG.
Constituent Coal “as-received” Coal “as dry” Coal “as combustible”
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
Ash
Moisture
77.37
5.09
7.00
1.83
1.22
4.39
3.10
79.85
5.25
7.22
1.89
1.26
4.53
xxxx
83.63
5.50
7.57
1.98
1.32
xxxx
xxxx
Total 100.00 100.00 100.00

2. 𝐻𝐻𝑉 = 33830𝐶 + 144270 ( 𝐻 −
𝑂
8
) + 9420𝑆
𝑘𝐽
𝑘𝑔
For as-firedbasis:
𝐻𝐻𝑉 = 33830𝐶 + 144270 ( 𝐻 −
𝑂
8
) + 9420𝑆
For dry basis:
𝐻𝐻𝑉 = 33830𝐶 + 144270 ( 𝐻 −
𝑂
8
) + 9420𝑆
3. The percentage bymass of carbon inhydrocarbonfuel, propane (C3H8),isnearlyequal to
a. 78.59%
b. 80.06%
c. 84.25%
d. 81.82%
4. Calculate the massof CO formedwhen175 kg of pure carbon are burned in300 kgof oxygen.
a. 292.0 kg
b. 286.3 kg
c. 289.6 kg
d. 295.6 kg
5. The theoretical amountof airrequiredtoburn1 kg of pure carbon to produce equal massesof
CO and CO2 isnearlyequal to
a. 7.95 kg
b. 6.84 kg
c. 8.41 kg
d. 6.22 kg
6. Pure carbon reactswithall the oxygenin60% of ideal air.Findthe massof carbon dioxide
formedper100 kg of air supplied.
a. 11.52 kg
b. 9.73 kg
c. 10.68 kg
d. 12.04 kg

3. 7. One kilogramof carbon isburnedsothat ½ kg of C goesintoCO2 and½ kg intoCO.Determine
the volume of thisairat 20o
C and101.325 kPa
a. 8.35 m3
b. 7.12 m3
c. 6.92 m3
d. 7.38 m3
8. Two molesof COare burnedin4.76 molesof air. Findthe air-fuel ratioinkgair/kgfuel.
a. 3.76
b. 2.46
c. 4.76
d. 2.38
9. The gravimetriccompositionof ahydrocarbonfuel is85% carbonand 15% hydrogen.Usingthe
formCxHy, whatisthe molecularformulaof the fuel expressedinwhole numbers?
a. C8H17
b. C6H10
c. C8H18
d. C3H8
10. A gas has the followinggravimetricanalysis:
CH4 = 85% H2 = 6% C2H4 = 9%
1. Findthe volumetricanalysisof thisgas.
Constituent GravimetricPercent
(kg)
MolecularWeight
(kg/kgmol)
VolumetricPercent
CH4 85 16 61.53
H2 6 2 34.75
C2H4 9 28 3.72
Total 100 100.00
CH4 = 85% H2 = 6% C2H4 = 9%

4. 2. Findthe approximate average heatingvalue of thisgasinkJ/m3
.
a. 32,150
b. 30,060
c. 31,850
d. 30,210
11. A natural gas has the followingvolumetricanalysis:CH4 =78.5%; C2H2 = 9.3%; H2 = 3.1%; CO2 =
1.4%; CO = 2.9%; O2 = 0.3%; and N2 = 45%. A volumetricanalysisof the dryflue gasresulting
fromthe combustionof thisgasshowsCO2 = 10%; O2 = 2.6%; CO = 0.9%; and N2 = 86.5%. Find
the percentage of excessairsupplied,assumingthe aircontains23.3% oxygenbymass.
a. 18%
b. 11%
c. 8%
d. 14%
12. A blast-furnace gasiscomposedof 0.2% CH4, 4% H2, 25.5% CO, 13.3% CO2, and57% N2 by
volume.Assumingaircontains23.3% oxygenbymass,calculate the theoretical massof air
requiredforthe complete combustioninkgair/kgfuel.
a. 0.716
b. 0.904
c. 0.773
d. 0.827
13. A coal as-receivedcontains3%moisture and8% ash The heatingvalue f the combustible portion
is32600 kJ/kg.Find:
1. The heatingvalue of kJ/kgdrycoal.
a. 29 910
b. 29 150
c. 30 230
d. 28 720
2. The heatingvalue inkJ/kg coal as-fired.

5. a. 30 230
b. 29 150
c. 29 014
d. 28 720
14. An anthracite coal has the followingultimate analysisbyweightC= 78.85%, H2 = 2.14%, N2 =
0.77%, O2 = 2.82%, N2 = 0.77%, S = 0.46%, ash = 11.53%, andmoisture 3.43%. Assume air
contains23.3% oxygenbymass.Determine:
1. The volumetricand gravimetricanalysesof the productsof combustionwhensupplied
withtheoretical air.
Volumetric Analysis
CO2 = 19.15%
H2O = 3.67%
SO2 = 0.04%
N2 = 77.14%
Gravimetric Analysis
CO2 = 27.44%
H2O = 2.15%
SO2 = 0.08%
N2 = 70.33%
2. The volumetricandgravimetricanalysesof the productsof combustionwhensupplied
with60% excessair.
Volumetric Analysis
CO2 = 12.08%
H2O = 2.32%
SO2 = 7.76%
N2 = 77.82%
Gravimetric Analysis
CO2 = 17.71%
H2O = 1.39%
SO2 = 0.04%
N2 = 72.59%
15. A hydrocarbonfuel,CnHxn,requiresequalmassesof oxygenforcomplete combustionof its
carbon and hydrogencomponents.Determinethe valuesof x andn of the fuel onmole basis.
1. x = 1 n = 4
2. x = 6 n = 2
3. x = 4 n = 1
4. x = 10 n = 4
16. The exhaustgasesfroman automotive engine operatingonoctane,C8H18,showedthe following
analysis:CO2 = 11.255, O2 = 4.55%, CO = 0.05%, N2 = 84.15% by volume.Aircontains23.2%
oxygenbymass.Find:
1. The actual mass of air usedperkilogramof fuel.
a. 15.2 kg
b. 17.0 kg
c. 19.0 kg
d. 22.5 kg
2. The percentage of excessairsupplied.

6. a. 26%
b. 28%
c. 24%
d. 30%
17. The products of combustionof a hydrocarbonfuel of unknowncompositionhave the following
volumetricanalysisinpercent,asmeasuredonadry basis:
CO2 CO O2 N2 Total
8.0 0.9 8.8 82.3 100.00
Assume aircontains23.3% oxygenbymass.Calculate:
1. The air-fuel ratioinkgair/kg fuel
a. 26
b. 24
c. 22
d. 28
2. The compositionof the fuel ona massbasis
a. C = 84% H = 16%
b. C = 86.1% H = 13.9%
c. C = 85.7% H = 14.3%
d. C = 85.2% H = 14.8%
3. The percenttheoretical airrequiredona massbasis
a. 164%
b. 162%
c. 160%
d. 166%
18. The exhaustgas froma spark-ignitionengine hasthe followingcomposition byvolumein
percent.
CO2 O2 CO H2 CH4 N2 Total
8.7 0.3 8.9 3.7 0.3 78.1 100.00
Determine the actual massof air suppliedtoburncompletelythe fuel(C8H17) inkgair/kgfuel.
Assume aircontains23.3% oxygenbymass.
a. 11.28
b. 10.58
c. 14.16
d. 12.02

7. 19. A fuel oil consistingof 84% carbon and16% hydrogenbymassis burnedinair containing23%
oxygenbymassat atmosphericpressure.Determine:
1. The stoichiometricairrequiredforthe completecombustionof thisfuel inkg/kgfuel
a. 17.15
b. 12.81
c. 15.30
d. 12.02
2. The percentage compositionof the productsof combustionbymassif 40% excessairis
supplied.
CO2 = 13.7% H2O = 6.4%
O2 = 6.3% N2 = 73.6%
20. The ultimate gravimetricanalysisof abituminouscoal as-receivedis70.85% C, 4.48% H2, 2.11%
S, 6.36% O2,1.38% N2,2.52% H2O,and 12.3% ash.During the actual combustion,the following
volumetricanalysisof the stackgaseswas obtained: 11.8% CO2,0.20% CO, 7.8% O2, and80.2%
N2.Refuse pitanalysisbymassshowed18% C and 82% ash.Assume aircontains23.3% oxygen
by mass.Determine:
1. The stoichiometricairrequiredforcomplete combustionof 1kg of coal.
a. 12.28 kg
b. 10.79 kg
c. 8.36 kg
d. 14.68 kg
2. The mass of actual air suppliedperkilogramof coal as-firedduringcombustion.
a. 16.61 kg
b. 17.63 kg
c. 14.73 kg
d. 19.25 kg
3. The percentage excessairsupplied.
a. 54.8%
b. 53.9%
c. 52.3%
d. 55.2%
4. The mass of dryproducts perkilogramof coal as-fired.
a. 17.83%
b. 16.94%
c. 15.06%
d. 13.98%
5. The mass of unburnedcarboninthe ashpitperkilogramof coal.
a. 0.027 kg
b. 0.092 kg
c. 0.015 kg
d. 0.045 kg
21. A certaincrude oil showsthe followingultimate gravimetricanalysis:C= 87.1% and H = 12.9%.
The volumetricanalysisof the dryflue gasresultingfromthe combustionof thisoil showsCO2 =

8. 12%, O2 = 4.6%, CO = 0%, and N2 = 83.4%. Compute the percentage of excessairsupplied.
Assume aircontains23.1% oxygenbymass.
a. 29%
b. 27%
c. 22%
d. 25%
22. The gravimetriccompositionof asample of coal isas follows:carbon,85%; hydrogen,3%;
oxygen,2%;and ash,10%. Calculate the minimumamountof airrequiredforthe complete
combustion of 1 kg of coal,assumingaircontains23.1% oxygenbymass.
a. 9.83 kg
b. 12.35 kg
c. 10.77 kg
d. 12.03 kg
23. The gravimetriccompositionof afuel oil isasfollows:carbon,80%;and hydrogen,20%.
Calculate the theoretical amountof airrequiredforthe complete combustionof 1kg of fuel oil,
assumingaircontains23.3% oxygenbymass.
a. 15.68 kg
b. 16.02 kg
c. 14.78 kg
d. 17.53 kg
24. The volumetriccompositionof producergasisas follows:H2 = 27%; O2 = 18%; CO = 12.5%; CH4 =
2.5%; and N2 = 40%. Findthe theoretical volume of airrequiredtoburncompletely1m3
of
producergas, assumingaircontains21% oxygenbyvolume.
a. 1.179 m3
b. 1.251 m3
c. 1.082 m3
d. 1.136 m3
25. A natural gas iscomposedof 22.6% C2H6 and77.4% of CH4 by volume.Findthe theoretical
amountof air requiredforthe complete combustionof 1 kg of gas, assumingaircontains23.1%
oxygenbymass.
a. 19 kg
b. 17 kg
c. 15 kg
d. 12 kg
26. One hundredkilogramperhourof ethyl alcohol,C2H6O,iscompletelyburnedinthe theoretical
amountof air.Assume aircontains23.3% O2 by mass.Find:
1. The volume of air neededforthe combustionof the fuel,measuredat100 kPa and 20o
C
inm3
/min
a. 13.29
b. 20.74
c. 19.13
d. 17.92
2. The volume of the exhaustgases,measuredat100 kPaand 150o
C in m3
/min
a. 15%

9. b. 18%
c. 12%
d. 20%
27. A dry coal withan ultimate gravimetricanalysisof 80% C, 4.5% H2, 1.5% S, 4.0% O2, 1.7% N2,and
8.3% ash is usedina steampowerplantwith an overall efficiencyof 40%.The net power
producedis1000 MW. Calculate:
1. The tons of coal requiredperday.
a. 7189
b. 7210
c. 7235
d. 7202
2. The tons of carbon dioxide (CO2) producedperday.
a. 21 189
b. 21 126
c. 20 850
d. 21 090
3. The tons of sulfurdioxide (SO2) releasedperdayif the cleaningprocessonthe stack
removed95% of the sulfurdioxide fromthe combustiongases.
a. 12
b. 14
c. 11
d. 9
28. The exhaustof a gasoline engine hasthe followingcompositionbyvolume:CO2 = 9.8%, O2 = 2%,
CO = 2.6%, CH4 = 1%, and N2 = 84.6%. The fuel containsonlycarbonandhydrogen.Assume air
contains23.1% oxygenbymass.Determine:
1. The kilogramof air actuallysuppliedperkilogramof fuel
a. 16.08
b. 14.92
c. 15.87
d. 15.30
2. The mass of carbonper kilogramof dryproducts.
a. 0.0545 kg
b. 0.0615 kg
c. 0.0602 kg
d. 0.0587 kg
3. The mass of oxygeninthe dryproductsper kilogramof fuel.
a. 0.2835 kg
b. 0.3018 kg
c. 0.3181 kg
d. 0.3217 kg
29. A gaseousdodecane fuel,C12H26,isburnedwithstoichiometricaircontaining23.3% oxygenby
mass.Determine:
1. The air-fuel ratioonmole basis.
a. 87.51

10. b. 88.06
c. 90.23
d. 88.96
2. The stoichiometricairrequiredforfuel combustioninkgair/kgfuel.
a. 14.94
b. 12.58
c. 15.08
d. 19.21
3. The molecularweightof the reactantsinkg/kgmol.
a. 31.08
b. 30.85
c. 30.42
d. 31.67
4. The molecularweightof the productsof combustioninkg/kgmol.
a. 28.65
b. 29.18
c. 27.86
d. 28.92
5. The ratio of the molesof reactantsto molesof productsof combustion.
a. 0.907
b. 0.894
c. 0.976
d. 0.942
6. The dewpointof the productsof combustionat1 atmosphere.
a. 54o
C
b. 52 o
C
c. 50 o
C
d. 56 o
C
30. Octane gasoline,C8H18(g) isburnedwithastoichiometricaircontaining23.1% oxygenbymass.
Determine:
1. The theoretical air-fuel ratioona massbasis.
a. 16.05
b. 15.21
c. 14.96
d. 15.72
2. The molecularweightof the reactantsinkg/kgmol.
a. 30.23
b. 29.53
c. 28.16
d. 31.05
3. The mass of dryflue gas perkilogramof fuel.
a. 14.79 kg
b. 15.06 kg
c. 14.11 kg

11. d. 15.25 kg
4. The dewpointof the productsof combustionat101 kPa.
a. 54.02o
C
b. 52.45o
C
c. 50.16o
C
d. 51.28o
C
5. The actual air-fuel ratioona massbasiswhenthe fuel isburnedwith 100% excessair.
a. 29.92
b. 31.44
c. 32.15
d. 30.42
6. The ratio of molesof reactantsto molesof productsof combustionwhenthe fuel is
burnedwith100% excessair.
a. 1.05
b. 0.97
c. 0.93
d. 1.14
7. The mass of dryflue gas perkilogramof fuel whenthe fuel isburnedwith100% excess
air.
a. 30.8 kg
b. 29.5 kg
c. 30 kg
d. 31.5 kg
8. The volumetric(molal)analysisof the productsof combustionwhenthe fuel isburned
with100% excessair.