The mass of flue gas generated in
boilers can be calculated using the principles of stoichiometry and the
knowledge of the fuel composition and combustion process. Here are the steps to
calculate the mass of flue gas:
1-Determine the Fuel
Composition:
You need to know the composition of the
fuel being used in the boiler. Typically, this includes information about the
types and proportions of elements in the fuel, such as carbon (C), hydrogen
(H), sulfur (S), oxygen (O), and other impurities. This information is usually
provided in the fuel's specifications.
2-Write the Combustion
Equation:
Write the balanced chemical equation
for the combustion of the fuel. For example, if you're burning natural gas
(CH4) in air (which contains oxygen), the combustion equation would be:
CH4 + 2O2 → CO2 +
2H2O
3-Calculate the
Stoichiometric Air-Fuel Ratio:
Calculate the stoichiometric air-fuel
ratio, which is the theoretical amount of air required for complete combustion.
This ratio depends on the chemical composition of the fuel and the combustion
equation. For the example above, one mole of methane requires two moles of
oxygen for complete combustion.
4-Determine the Actual
Air-Fuel Ratio:
In real-world situations, the actual
air-fuel ratio is usually not exactly stoichiometric due to factors like
incomplete combustion, excess air, and variations in combustion efficiency. You
may need to measure or estimate the actual air-fuel ratio in your specific
boiler operation.
5-Calculate the Mass of
Fuel:
Determine the mass of fuel being burned
in the boiler. This is typically measured or known based on the flow rate and
properties of the fuel being supplied to the boiler.
6-Calculate the Mass of
Air:
Using the actual air-fuel ratio and the
mass of fuel burned, calculate the mass of air required for combustion. You can
do this by multiplying the mass of fuel by the actual air-fuel ratio.
Read more>>>>How to calculate quantity of SO2 generation
in flue gas
7-Calculate the Mass of
Flue Gas:
The mass of flue gas is equal to the
mass of the combustion products, which includes the mass of the carbon dioxide
(CO2), water vapor (H2O), and any other combustion products produced in the
combustion process. Use the balanced combustion equation to calculate the
masses of these products.
For example, in the combustion of
methane (CH4) from step 2, you can calculate the mass of CO2 and H2O produced
based on the moles of CH4 burned and their molar masses.
8-Sum Up the Masses:
Add up the masses of all the combustion
products to find the total mass of flue gas generated in the boiler.
Keep in mind that this is a simplified
calculation, and real-world combustion processes can be more complex due to
factors like incomplete combustion, impurities in the fuel, and variations in
combustion efficiency.
Therefore, it's important to consider
these factors for a more accurate estimation of flue gas mass in a specific
boiler system. Additionally, measuring instruments and gas analyzers can
provide real-time data on flue gas composition and mass flow rates in practical
applications.
Flue Gas Mass Calculator (per batch of fuel)
Enter fuel mass (kg) and elemental composition (mass %). Optionally give dry flue gas O₂ (%) to compute actual excess air; otherwise the calculator gives theoretical (stoichiometric) flue gas.
