Importance of Flue Gas Analysis | Energy Conservation


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Major benefits of flue gas analysis include, determining combustion efficiency, burner tune up requirements, and need for pollutants reduction.

Importance of Flue Gas Analysis | Energy Conservation

Most of fuels used are hydrocarbon compounds. This means that the main products of combustion are CO2 and H2O. If combustion air is not sufficient for complete combustion or the combustion process suffers from insufficient mixing between air and fuel, CO as well as unburned hydrocarbons emission is expected. If the fuel air mixture is too rich or the mixing between air and fuel is too bad smoky flue gases are seen due to the formation of soot. On the contrary if the combustion air is more than that necessary for complete combustion excess oxygen will come out with the flue gases. As a result of combustion and due to the high temperature Nitrogen may react with Oxygen in the combustion air and form NO which leads to the formation of NO2. These emissions are known as NOx. If the fuel has sulfur content SO2 emissions are expected.

Flue gas analyzers usually measure the volumetric concentration of the dry exhaust emissions in percentage (%), part per million (ppm) or mg/Nm³. {mg/Nm³ = ppm*(molecular weight/24.528)}

The factor 24.528 is the volume occupied by one mole at standard pressure and temperature. Since the flue gas analysis concentrations represents the ratio of certain gas in a mixture of gases. These concentrations will be a function in the air to fuel ratio. Therefore, for the sack of comparison between two analyses at different air to fuel ratio concentrations are usually normalized to a certain Oxygen concentration. This is usually considered at 3% Oxygen concentration in the flue gases.

Normalized Concentration = Concentration *Oxygen (%)/3%
Since hydrocarbon emissions are mixture of several hydrocarbons they usually measured as the equivalent concentration of Methane (CH4), Propane (C3H8) or Hexane (C6H14).

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