Enter the excess concentration of CO2 (ΔCO2, ppmv) and the excess concentration of CO (ΔCO, ppmv) into the calculator to determine the Modified Combustion Efficiency (MCE).
Note: MCE is a combustion completeness metric based on CO and CO2. It is not the same as the thermal combustion efficiency used for boilers/furnaces (which is based on useful heat output versus fuel energy input).
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Modified Combustion Efficiency (MCE) Formula
The following formula is used to calculate the Modified Combustion Efficiency (MCE).
MCE = \Delta CO_2 / (\Delta CO_2 + \Delta CO) \times 100
- Where MCE is the Modified Combustion Efficiency (%)
- ΔCO2 is the excess concentration of CO2 (ppmv) above background
- ΔCO is the excess concentration of CO (ppmv) above background
To calculate MCE, divide ΔCO2 by the sum of ΔCO2 and ΔCO, then multiply by 100. (If you are sampling a diluted plume or ambient air, subtract background concentrations first to obtain ΔCO2 and ΔCO. If you are sampling undiluted exhaust, background is often negligible.)
How to Calculate Modified Combustion Efficiency (MCE)?
The following example problem outlines how to calculate MCE.
Example Problem #1:
- First, determine ΔCO2 (ppmv). In this example, ΔCO2 is 10,000 ppmv.
- Next, determine ΔCO (ppmv). For this problem, ΔCO is 500 ppmv.
- Finally, calculate MCE using the equation above:
MCE = ΔCO2 / (ΔCO2 + ΔCO) × 100
Inserting the values from above and solving the equation:
MCE = 10,000 / (10,000 + 500) × 100 = 95.24 (%)
FAQ
What factors can affect modified combustion efficiency (MCE)?
MCE is primarily affected by how completely carbon in the fuel is oxidized to CO2 instead of CO. Factors that commonly influence MCE include oxygen availability (air/fuel mixing), flame temperature, residence time, turbulence/mixing, fuel moisture, and whether combustion is flaming versus smoldering.
Why is it important to measure MCE?
MCE is often used as an indicator of combustion completeness. Higher MCE generally corresponds to a larger fraction of carbon emitted as CO2 (and less as CO), which can be useful for comparing combustion conditions and estimating emission characteristics. It does not, by itself, provide thermal/energy efficiency.
How can MCE be improved?
To increase MCE (reduce incomplete combustion), typical approaches include improving air delivery and mixing, maintaining adequate combustion temperature and residence time, and keeping burners/equipment properly tuned and maintained. In many systems, avoiding oxygen-starved zones and improving turbulence/mixing helps reduce CO formation.
