Improvement in $\hbox{NO}_{\rm x}$ Removal Performance of the Pilot-Scale Boiler Emission Control System Using an Indirect Plasma–Chemical Process

NO
_x
removal from the flue gas of a smoke tube boiler using an ozonizer for NO oxidation and a Na
₂
SO
₃
aqueous solution scrubber (diameter: 0.6 m; height: 3.7 m) was investigated. In this paper, in order to determine the correlation NO
_x
removal performance, the height of the packing material layer in the scrubber was varied from 2.1 to 0 m. The performance tests were carried out using both a compressed natural gas (CNG) and a heavy oil. The flue gas flow rates were in the range of 455-1440 Nm
³
/h under CNG firing and 675-1330 Nm
³
/h under heavy oil firing, and the boiler NO
_x
emission concentrations were approximately 40 and 100 ppm, respectively. A total packing height of 0.75 m resulted in NO
_x
removal efficiencies of 70% and 60% for CNG and heavy oil, respectively. Moreover, the Na
₂
SO
₃
consumption rate at 0.75 m was 10%-20% less than that at 1.2 m, although the NO
_x
removal efficiency was nearly the same. The correlation between the NO
_x
removal performance and the gas retention time in the scrubber was obtained, providing the design information of the scrubber for industrial applications.