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 Na₂SO₃ 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 Nm³/h under CNG firing and 675-1330 Nm³/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 Na₂SO₃ 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.