Simultaneous removal of NOx and SOx in flue gas emission using plasma-chemical hybrid process

In the previous studies, we confirmed that the plasma-chemical combined hybrid process for controlling NO_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_x and SO_x at elevated temperature using the plasma-chemical hybrid process. A series of experiments were performed to quantify all the reaction byproducts such as N₂O, CO, HNO₂, HNO₃, NO₃ ^- and SO₄^- to evaluate the simultaneous NO_x and SO_x removal efficiency. The oxidation from NO to NO₂ without decreasing NO_x concentration (i.e., minimum reaction byproducts) 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 or Na₂ S with and without NaOH using the barrier-type packed-bed plasma reactor followed by the packed column chemical reactor. The NO₂ reduction was more effective for Na₂S than Na₂ SO₃ and at least 5 times of stoichiometric amount of chemicals are required for complete N₂ reduction. The hybrid process showed nearly 100% NO_x and SO_x simultaneous removal which was achieved with less than 5 ppm of N₂ O and CO, and the operating cost was less than 1/10 of the SCR process. The additional SO₂ treatment system can be eliminated