Combustion
Environmental Engineering · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- Combustible Substance Reaction Mols lb (kg)*
- *Substitute the molecular weights in the reaction equation to secure lb (kg). The lb (kg) on each side of the equation must balance.
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
combustion of municipal solid waste in a waste-to-energy facility Given heat released (Q_fuel) = 326,400 kJ; mass of fuel burned (m_fuel) = 312.0 kg, determine the higher heating value (HHV) in kJ/kg.
Given
Find
higher heating value (HHV), in kJ/kg
Start with the thinking
- The governing relation printed in this handbook section is Combustion.
- Everything except HHV is given, so isolate HHV symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for HHV:
Step 3 — List the givens: heat released (Q_fuel) = 326,400 kJ, mass of fuel burned (m_fuel) = 312.0 kg.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning HHV = 1,046 kJ/kg to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 2,092 — kept a factor of two that cancels in the correct rearrangement.
- 523.1 — dropped that same factor in the other direction.
- 1,151 — rounded an intermediate value before the final step.
Reference: FE Handbook — Combustion
combustion heating value calculation for a fuel sample Given mass of fuel burned (m_fuel) = 901.0 kg; higher heating value (HHV) = 37,990 kJ/kg, determine the heat released (Q_fuel) in kJ.
Given
Find
heat released (Q_fuel), in kJ
Start with the thinking
- The governing relation printed in this handbook section is Combustion.
- Everything except Q_fuel is given, so isolate Q_fuel symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Q_fuel:
Step 3 — List the givens: mass of fuel burned (m_fuel) = 901.0 kg, higher heating value (HHV) = 37,990 kJ/kg.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Q_fuel = 34,228,990 kJ to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 68,457,980 — kept a factor of two that cancels in the correct rearrangement.
- 17,114,495 — dropped that same factor in the other direction.
- 37,651,889 — rounded an intermediate value before the final step.
Reference: FE Handbook — Combustion
combustion energy release computed from fuel mass and heating value Given heat released (Q_fuel) = 1,994,400 kJ; higher heating value (HHV) = 25,450 kJ/kg, determine the mass of fuel burned (m_fuel) in kg.
Given
Find
mass of fuel burned (m_fuel), in kg
Start with the thinking
- The governing relation printed in this handbook section is Combustion.
- Everything except m_fuel is given, so isolate m_fuel symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for m_fuel:
Step 3 — List the givens: heat released (Q_fuel) = 1,994,400 kJ, higher heating value (HHV) = 25,450 kJ/kg.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning m_fuel = 78.3654 kg to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 156.7 — kept a factor of two that cancels in the correct rearrangement.
- 39.1827 — dropped that same factor in the other direction.
- 86.2020 — rounded an intermediate value before the final step.
Reference: FE Handbook — Combustion
combustion of municipal solid waste in a waste-to-energy facility Given heat released (Q_fuel) = 3,555,600 kJ; mass of fuel burned (m_fuel) = 646.0 kg, determine the higher heating value (HHV) in kJ/kg.
Given
Find
higher heating value (HHV), in kJ/kg
Start with the thinking
- The governing relation printed in this handbook section is Combustion.
- Everything except HHV is given, so isolate HHV symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for HHV:
Step 3 — List the givens: heat released (Q_fuel) = 3,555,600 kJ, mass of fuel burned (m_fuel) = 646.0 kg.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning HHV = 5,504 kJ/kg to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 11,008 — kept a factor of two that cancels in the correct rearrangement.
- 2,752 — dropped that same factor in the other direction.
- 6,054 — rounded an intermediate value before the final step.
Reference: FE Handbook — Combustion
combustion heating value calculation for a fuel sample Given mass of fuel burned (m_fuel) = 710.0 kg; higher heating value (HHV) = 28,590 kJ/kg, determine the heat released (Q_fuel) in kJ.
Given
Find
heat released (Q_fuel), in kJ
Start with the thinking
- The governing relation printed in this handbook section is Combustion.
- Everything except Q_fuel is given, so isolate Q_fuel symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Q_fuel:
Step 3 — List the givens: mass of fuel burned (m_fuel) = 710.0 kg, higher heating value (HHV) = 28,590 kJ/kg.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Q_fuel = 20,298,900 kJ to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 40,597,800 — kept a factor of two that cancels in the correct rearrangement.
- 10,149,450 — dropped that same factor in the other direction.
- 22,328,790 — rounded an intermediate value before the final step.
Reference: FE Handbook — Combustion
combustion energy release computed from fuel mass and heating value Given heat released (Q_fuel) = 4,998,000 kJ; higher heating value (HHV) = 41,070 kJ/kg, determine the mass of fuel burned (m_fuel) in kg.
Given
Find
mass of fuel burned (m_fuel), in kg
Start with the thinking
- The governing relation printed in this handbook section is Combustion.
- Everything except m_fuel is given, so isolate m_fuel symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for m_fuel:
Step 3 — List the givens: heat released (Q_fuel) = 4,998,000 kJ, higher heating value (HHV) = 41,070 kJ/kg.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning m_fuel = 121.7 kg to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 243.4 — kept a factor of two that cancels in the correct rearrangement.
- 60.8473 — dropped that same factor in the other direction.
- 133.9 — rounded an intermediate value before the final step.
Reference: FE Handbook — Combustion
combustion of municipal solid waste in a waste-to-energy facility Given heat released (Q_fuel) = 3,857,700 kJ; mass of fuel burned (m_fuel) = 500.0 kg, determine the higher heating value (HHV) in kJ/kg.
Given
Find
higher heating value (HHV), in kJ/kg
Start with the thinking
- The governing relation printed in this handbook section is Combustion.
- Everything except HHV is given, so isolate HHV symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for HHV:
Step 3 — List the givens: heat released (Q_fuel) = 3,857,700 kJ, mass of fuel burned (m_fuel) = 500.0 kg.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning HHV = 7,715 kJ/kg to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 15,431 — kept a factor of two that cancels in the correct rearrangement.
- 3,858 — dropped that same factor in the other direction.
- 8,487 — rounded an intermediate value before the final step.
Reference: FE Handbook — Combustion
combustion heating value calculation for a fuel sample Given mass of fuel burned (m_fuel) = 527.0 kg; higher heating value (HHV) = 44,840 kJ/kg, determine the heat released (Q_fuel) in kJ.
Given
Find
heat released (Q_fuel), in kJ
Start with the thinking
- The governing relation printed in this handbook section is Combustion.
- Everything except Q_fuel is given, so isolate Q_fuel symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Q_fuel:
Step 3 — List the givens: mass of fuel burned (m_fuel) = 527.0 kg, higher heating value (HHV) = 44,840 kJ/kg.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning Q_fuel = 23,630,680 kJ to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 47,261,360 — kept a factor of two that cancels in the correct rearrangement.
- 11,815,340 — dropped that same factor in the other direction.
- 25,993,748 — rounded an intermediate value before the final step.
Reference: FE Handbook — Combustion
combustion energy release computed from fuel mass and heating value Given heat released (Q_fuel) = 567,200 kJ; higher heating value (HHV) = 10,220 kJ/kg, determine the mass of fuel burned (m_fuel) in kg.
Given
Find
mass of fuel burned (m_fuel), in kg
Start with the thinking
- The governing relation printed in this handbook section is Combustion.
- Everything except m_fuel is given, so isolate m_fuel symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for m_fuel:
Step 3 — List the givens: heat released (Q_fuel) = 567,200 kJ, higher heating value (HHV) = 10,220 kJ/kg.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning m_fuel = 55.4990 kg to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 111.0 — kept a factor of two that cancels in the correct rearrangement.
- 27.7495 — dropped that same factor in the other direction.
- 61.0489 — rounded an intermediate value before the final step.
Reference: FE Handbook — Combustion
combustion of municipal solid waste in a waste-to-energy facility Given heat released (Q_fuel) = 2,621,300 kJ; mass of fuel burned (m_fuel) = 971.0 kg, determine the higher heating value (HHV) in kJ/kg.
Given
Find
higher heating value (HHV), in kJ/kg
Start with the thinking
- The governing relation printed in this handbook section is Combustion.
- Everything except HHV is given, so isolate HHV symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for HHV:
Step 3 — List the givens: heat released (Q_fuel) = 2,621,300 kJ, mass of fuel burned (m_fuel) = 971.0 kg.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning HHV = 2,700 kJ/kg to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 5,399 — kept a factor of two that cancels in the correct rearrangement.
- 1,350 — dropped that same factor in the other direction.
- 2,970 — rounded an intermediate value before the final step.
Reference: FE Handbook — Combustion