Towards ideal NOx control technology using a plasma-chemical hybrid process

The plasma-chemical hybrid process developed was extremely effective and economical in comparison with the conventional selective catalytic reduction (SCR) system and other technologies for NO_x removal from flue gas emissions. A series of experiments was performed to quantify all the reaction by-products such as N₂O, CO, HNO₂, HNO₃, and NO₃ ^- and to evaluate NO_x removal efficiency. The optimum plasma reactor and its operating characteristics were investigated with regard to reaction by-products and NO_x removal efficiency using the ordinary ferroelectric packed-bed plasma reactor and the barrier-type packed-bed plasma reactor. The oxidation from NO to NO₂ without decreasing NO_x concentration (i.e., minimum reaction by-products) and with least power consumption is the key for the optimum reactor operating condition. The produced NO₂ was totally converted to N₂ and Na ₂SO₄ with Na₂SO₃ scrubbing. The barrier-type packed-bed plasma reactor having 1.5 mm diameter electrode and 3 mm diameter BaTiO₃ pellets showed the superior NO oxidation without producing the by-products over the conventional packed-bed reactor. The barrier-type packed-bed plasma reactor followed by the chemical reactor showed extremely low operating costs (less than 1/6 of the SCR process) and achieved nearly 100% NO_x removal with less than 6 ppm of N₂O and 5 ppm of CO