By combusting fuels for heat and energy, industry emits stack gases to the environment. In perfect combustion, only CO2 and water vapor would result. However, purity of fuels, complex mixing dynamics and process reactions combine to produce pollutants such as oxides of nitrogen (NOX), oxides of sulfur (SOX) and carbon monoxide (CO).
Most industry in North America runs on fuel gases. In most clean fuel gases, no sulfur content exists, so the formation of SOX will not be discussed here. The focus is NOX and CO.
Oxides of nitrogen are formed by a variety of mechanisms or chemical pathways, but most begin with a dissociation of diatomic nitrogen (N2) contained in air. Burner design is the primary method to reduce NOX where air and fuel react to create heat.
Conventional burners produce NOX in the range of 80 ppm to 120 ppm. Note that ppm stands for parts per million. This measurement is volumetric and must be corrected to a standardized dilution level of 3% oxygen equivalent. Low NOX burners reduce NOX to 25 ppm to 50 ppm while ultra-low NOX burners can produce NOX less than 10 ppm.
Low NOX and ultra-low NOX burner designs use a variety of methods like advanced mixing, fuel staging, air staging and flue-gas recirculation to manipulate emissions levels. From the numbers above, you can see that NOX can be reduced as much as 95% over conventional burners with better burner technology. Reducing NOX in industrial processes contains one key step: invest in advanced low NOX or ultra-low NOX burners.
Mitigating CO is somewhat easier than mitigating NOX, because unlike NOX, CO is flammable. Burner design can help to reduce or eliminate CO, but other actions can be taken as well.
To reduce CO, think "hot." If combustion products can be held at higher temperatures for a few fractions of a second longer with available oxygen, CO can be thermally converted to CO2. When you protect burner flames from aggressive crossing process flows, CO levels may be reduced.
A clean, healthy environment is in everyone's best interest including those of manufacturers. Industry can continue to produce profitably without fearing emissions compliance by meeting the challenge with burner technology and advanced controls.
SidebarLow NOXand ultra-low NOXburners can reduce NO
Xlevels by as much as 95% over conventional burners because of their better burner technology. Investing in advanced low NOXor ultra-low NOXburners is one way to lower industrial process energy costs.
In many cases, pollutants aren't created when burners operate at equilibrium conditions. When burners modulate, any error in the dynamic control of fuel/air ratio can create momentary deviations in emissions. Therefore, a critical part of operating a low NOX burner is using an advanced fuel/air ratio control system to ensure precise emissions control, even under dynamic conditions.