Flue Gas Mass Flow Rate Calculator
Enter the mass flow of fuel (e.g., kg/hr or lb/hr).
— Select Fuel Type or Enter Custom —
Natural Gas (Methane)
Propane
Light Fuel Oil (Diesel)
Heavy Fuel Oil
Coal (Bituminous)
Wood (Biomass)
Mass of air required to burn 1 unit mass of fuel completely.
Percentage of air supplied above the stoichiometric requirement.
Theoretical Air Flow:
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Actual Air Flow (with Excess):
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Total Flue Gas Mass Flow:
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Understanding Flue Gas Mass Flow Rate
Calculating the mass flow rate of flue gas is a critical step in the design and operation of industrial boilers, furnaces, and combustion systems. It determines the sizing of stacks, ducts, pollution control equipment (like scrubbers or electrostatic precipitators), and heat recovery systems.
Why is this calculation important?
Accurate estimation of flue gas flow allows engineers to:
- Size Exhaust Stacks: Ensuring the stack is wide enough to prevent excessive backpressure but narrow enough to maintain draft.
- Monitor Emissions: Regulatory reporting often requires mass flow data to calculate total pollutant output (e.g., kg of NOx per hour).
- Optimize Heat Recovery: Economizers and air preheaters depend on known mass flow rates for thermal calculations.
The Calculation Logic
The total mass of flue gas leaving the stack is essentially the sum of the fuel mass fed into the burner and the air mass supplied for combustion. While ash removal affects solid fuels, for gaseous and liquid fuels, the mass balance is:
Mflue = Mfuel + Mair_total
To find the Total Air Mass (Mair_total), we use the Stoichiometric Air-to-Fuel Ratio (SAFR) and the percentage of Excess Air.
Mair_total = Mfuel × SAFR × (1 + (Excess Air % / 100))
Input Parameters Explained
- Fuel Consumption Rate: The mass of fuel burned per unit of time (e.g., kg/hr or lb/hr).
- Stoichiometric Ratio (SAFR): The theoretical mass of air required to completely burn one unit mass of fuel. For Natural Gas, this is typically around 17.2; for Fuel Oil, it is around 14.6.
- Excess Air: In real-world combustion, perfect mixing is impossible, so extra air is added to ensure complete combustion and safety. Typical values range from 10% to 20% for gas burners and 20% to 50% for solid fuels.
Note on Units
This calculator is unit-agnostic regarding mass and time. If you input Fuel Flow in kg/hr, the result will be in kg/hr. If you input lb/min, the result will be in lb/min. Ensure the Air-to-Fuel ratio is mass-based (kg air / kg fuel), which is dimensionless.