Towards ideal NOx control technology using 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 thermal power plant flue gas emissions. A series of experiments were performed to quantify all the reaction byproducts 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 in regard to reaction byproducts 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 byproducts) and with the least power consumption is the key for the optimum reactor design. The produced NO₂ was totally converted to N₂ and Na₂SO₄ with Na₂SO₃ scrubbing. The barrier-type packed-bed plasma reactor having a 1.5 mm diameter electrode and 3 mm diameter BaTiO₃ pellets followed by the chemical reactor showed the superior results: extremely low operating cost (less than 1/15 of the SCR process) and nearly 100% NO_x removal with less than 6 ppm of N₂O and 5 ppm of CO