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 NOinfinity 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 NOinfinity removal efficiency. The optimum plasma reactor and its operating characteristics were investigated with regard to reaction by-products and NOinfinity 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 NOinfinity 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 N-2 and Na2SO4 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% NOinfinity removal with less than 6 ppm of N2O and 5 ppm of CO.