Results are presented showing 30 to 50% NOx reduction relative to high-quality first generation LNBs. This represents over 80% NOx reduction relative to uncontrolled sources with conventional burners. Unburned combustibles tend to increase with combustion modifications which reduce NOx.
However, the new systems minimize this problem, without resorting to pulverizer upgrades. When pulverizer upgrades were simultaneously implemented, unburned combustibles were cut 80% along with major NOx reductions. Results are presented for 600 MW class units, substantiating the performance for a variety of coals, and verifying previous large-scale development work.
B&W has developed a wide range of combustion systems to reduce NOx emissions from power plants. Investigations began over 40 years ago with pioneering work in the use of air staging systems.
The company's first generation low NOx coal burner, the original Dual Register Burner(DRB).
B&W developed its second generation low NOx burner, the DRB-XCL burner, in the mid-late 80s to address NOx control needs for existing (and new) boilers. Existing units not equipped with low NOx burners were facing NOx control regulations. These units needed an effective, rugged design that was adaptable to the diverse population of B&W boilers and those of other suppliers. The development and results with the DRB-XCL burner have been well documented
elsewhere and are only briefly considered here.
A prototype burner was designed, constructed, and refined through an extensive program of large scale combustion tests in the CEDF. Ultimately the new burner, named the DRB-4Z™, reduced NOx 25 to 40+% beyond B&W's most advanced dual air zone burner.
Coal continues to be the dominant fossil fuel for electrical power generation in the U.S., and its usage could grow in response to energy demands. B&W’s dedication to advancing low NOx combustion is attested to by over 100,000 MW of generating capacity, which cover the gamut of combustion systems – single wall, opposed wall, and roof fired; tangentially fired; and cyclones.
Some of the first and second generation low NOx burners proved fairly effective in NOx control,but often at the expense of higher unburned carbon. Advanced low NOx systems have proven even more effective at reducing NOx, and can simultaneously minimize unburned carbon. These systems can provide significant reductions when retrofitted in place of first generation systems, and may offer an alternative to SCR systems.
