Nox Emission Calculator
Compute nox emission using validated scientific equations. See step-by-step derivations, unit analysis, and reference values.
Formula
NOx = Fuel x EF x Hours x (1 - Ctrl/100)
Multiply fuel rate by emission factor and hours then reduce by control efficiency.
Worked Examples
Example 1: Gas Boiler SCR
Problem: 500 m3/hr, EF 0.0022, 2000 hr, 85% ctrl.
Solution: Rate = 500 x 0.0022 = 1.1 kg/hr Total = 1.1 x 2000 = 2200 kg Controlled = 2200 x 0.15 = 330 kg
Result: 330 kg (0.33 metric tons)
Example 2: Coal No Ctrl
Problem: 50 t/hr, EF 8.5, 6000 hr, 0%.
Solution: Rate = 50 x 8.5 = 425 kg/hr Total = 425 x 6000 = 2550000 kg Controlled = 2550000
Result: 2550000 kg (2550 metric tons)
Frequently Asked Questions
What are NOx emissions and why do they matter?
NOx emissions refer to nitrogen oxides, primarily nitric oxide and nitrogen dioxide, released during combustion of fossil fuels. These pollutants are precursors to ground-level ozone and smog, causing respiratory illness and environmental damage. Power plants, vehicles, and industrial boilers are the largest NOx sources. Regulatory agencies worldwide set strict limits on NOx output because of the role in acid rain formation.
How is the NOx emission rate calculated?
The NOx emission rate is calculated by multiplying the fuel consumption rate by a fuel-specific emission factor in kilograms of NOx per unit of fuel burned. The factor depends on combustion technology, fuel type, and operating conditions. This gives the uncontrolled hourly rate before pollution control devices. Total emissions are found by multiplying the hourly rate by operating hours.
What is a NOx emission factor?
A NOx emission factor is a representative value relating the quantity of NOx released per unit of activity, typically fuel combustion. The EPA publishes emission factors in its AP-42 compilation for hundreds of source categories. Factors vary widely depending on fuel type and combustion technology. Accurate emission factors are critical for regulatory compliance and environmental impact assessments.
What pollution control technologies reduce NOx?
Selective Catalytic Reduction achieves 70-90 percent NOx reduction by injecting ammonia or urea over a catalyst bed. Selective Non-Catalytic Reduction achieves 30-50 percent at lower cost by injecting reagent into the furnace. Low-NOx burners reduce peak flame temperatures for 30-60 percent reduction. Exhaust gas recirculation dilutes intake oxygen to suppress thermal NOx formation.
What is the difference between thermal NOx and fuel NOx?
Thermal NOx forms when atmospheric nitrogen and oxygen react at temperatures above 1500 degrees Celsius during combustion. Fuel NOx originates from nitrogen chemically bound in the fuel that oxidizes during burning. For high-nitrogen fuels like coal fuel NOx can be 50-80 percent of total emissions. Natural gas produces mainly thermal NOx since it contains negligible fuel-bound nitrogen.
How does control efficiency affect total NOx output?
Control efficiency is the percentage of pollutant removed by abatement equipment before exhaust reaches the atmosphere. An 80 percent efficiency means only 20 percent of uncontrolled emissions are released to the air. The controlled emission equals uncontrolled emission times one minus the efficiency fraction. Engineers must balance higher-efficiency systems against their greater capital and operating costs.