Pilot-Scale $\hbox {NO}_{\rm x}$ and $\hbox {SO}_{\rm x}$ Removal From Boiler Emission Usin

Pilot-scale simultaneous NO_x and SO_x removal from boiler emission was performed using an indirect-plasma and chemical hybrid process. The flue-gas flow rate was in the range of 450-1470 Nm³/h, the gas temperature was 280??C, the NO_x concentration was 30 ppm for city-gas firing, and both NO_x and SO_x concentrations were 70 and 35 ppm for heavy-oil firing, respectively. Radical injection by an indirect plasma was demonstrated to be extremely effective for NO oxidation, particularly when the flue-gas temperature is in the range of 300??C where NO_x is generated at this temperature. The produced NO₂ was further reduced to N₂ and nontoxic and water-soluble Na₂SO₄ by a Na₂SO₃ chemical scrubber. For the case of oil-firing boiler, SO₂ was simultaneously adsorbed by NaOH solution. The NO_x removal efficiency for gas firing exceeds 90%, but the NO_x removal efficiency for oil firing was in the range of 60% due to the lack of ozone concentration with the present pulse power supply. The removal efficiency of SO₂ was in the range of 85%-90%. The NO_x removal efficiency was evaluated by the ratio of the radical flow rate to the primary flue-gas flow rate, specific energy density, Na₂SO₃ concentration and chemical flow rate. Finally, the quality of disposed water was also investigated and proved to be disposable.