Towards ideal NO/sub x/ control technology using a plasma-chemical hybrid process

Abstract

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/sub x/ removal from flue gas emissions. A series of experiments was performed to quantify all the reaction by-products such as N/sub 2/O, CO, HNO/sub 2/, HNO/sub 3/, and NO/sub 3//sup -/ and to evaluate NO/sub x/ removal efficiency. The optimum plasma reactor and its operating characteristics were investigated with regard to reaction by-products and NO/sub x/ removal efficiency using the ordinary ferroelectric packed-bed plasma reactor and the barrier-type packed-bed plasma reactor. The oxidation from NO to NO/sub 2/ without decreasing NO/sub x/ concentration (i.e., minimum reaction by-products) and with least power consumption is the key for the optimum reactor operating condition. The produced NO/sub 2/ was totally converted to N/sub 2/ and Na/sub 2/SO/sub 4/ with Na/sub 2/SO/sub 3/ scrubbing. The barrier-type packed-bed plasma reactor having 1.5 mm diameter electrode and 3 mm diameter BaTiO/sub 3/ 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/sub x/ removal with less than 6 ppm of N/sub 2/O and 5 ppm of CO.