NO{sub x} control technologies applicable to municipal waste combustion

Nitrogen oxides (NO{sub x}) are of environmental significance because of their role as a criteria pollutant, acid gas, and ozone precursor. The current New Source Performance Standards (NSPS) for municipal waste combustors (MWCS) limit NO{sub x} emissions to a daily average of 180 parts per million (ppM) at 7% oxygen, dry basis. By comparison, typical NO{sub x} emissions from modern mass burn waterwall (MB/WW) MWCs range from 220 to 320 ppM. To comply with the NSPS, most recently built MWCs have used a combination of combustion controls to limit NO{sub x} formation and selective non-catalytic reduction (SNCR) to convert NO{sub x} to molecular nitrogen. Because of pressure to achieve even lower emission levels, questions have been raised regarding the potential for advancement in NO{sub x} control technologies. To respond to these questions, the Air and Energy Engineering Research Laboratory and the National Renewable Energy Laboratory initiated this assessment of three alternative NO{sub x} control technologies: natural gas injection (NGI), SNCR, and selective catalytic reduction (SCR). The objectives of this assessment were to (1) document the key design and operating parameters, commercial status, demonstrated performance, and cost of each technology, and (2) identify technology research and development needs