Simultaneous removal of NO/sub x/ and SO/sub x/ in flue gas emission using plasma-chemical hybrid process

Abstract

In the previous studies, we confirmed that the plasma-chemical combined hybrid process for controlling NO/sub x/ flue gas emission was extremely effective and economical in comparison with the conventional selective catalytic reduction (SCR) system and other technologies. In the present study, we carried out the experiments on the simultaneous removal of NO/sub x/ and SO/sub x/ at elevated temperature using the plasma-chemical hybrid process. A series of experiments were performed to quantify all the reaction byproducts such as N/sub 2/O, CO, HNO/sub 2/, HNO/sub 3/, NO/sub 3//sup -/ and SO/sub 4//sup -/ to evaluate the simultaneous NO/sub x/ and SO/sub x/ removal efficiency. The oxidation from NO to NO/sub 2/ without decreasing NO/sub x/ concentration (i.e., minimum reaction byproducts) 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/ or Na/sub 2/S with and without NaOH using the barrier-type packed-bed plasma reactor followed by the packed column chemical reactor. The NO/sub 2/ reduction was more effective for Na/sub 2/S than Na/sub 2/SO/sub 3/ and at least 5 times of stoichiometric amount of chemicals are required for complete N/sub 2/ reduction. The hybrid process showed nearly 100% NO/sub x/ and SO/sub x/ simultaneous removal which was achieved with less than 5 ppm of N/sub 2/O and CO, and the operating cost was less than 1/10 of the SCR process. The additional SO/sub 2/ treatment system can be eliminated.