Toward NOx/SOx and Nanoparticle Control Technology Using a Single-Stage Wet-Type Nonthermal Plasma Reactor

Nitrogen oxides ( NO
_x
), sulfur oxides ( SO
_x
), and particulate matter (PM) emitted by diesel engines, thermal power generation plants, and various industrial establishments have had unfavorable effects on the environment globally. Therefore, it is necessary to install aftertreatment systems on such combustors because the emissions cannot be treated for combustion improvement only. To establish NO
_x
/SO
_x
, and nanoparticle control technologies, herein, we propose a single-stage wet-type nonthermal plasma (NTP) reactor. To evaluate the performance of the proposed system, we conducted a laboratory-scale experiment with a mixture of NO
_x
, SO
_x
, and polystyrene particles. In this system, PM is collected in a water film by the electrostatic effect, NO is oxidized to NO
₂
by NTP, and NO
₂
and SO
₂
are absorbed into a water film on the inner wall of the reactor. We achieved almost complete and simultaneous removal of the pollutants, with a partial collection efficiency of more than 98% for the nanoparticles (diameter = 22-334 nm), removal efficiency of 98% for NO
_x
, and removal efficiency of 99% for SO
_x
. Furthermore, we proposed a method to treat the chemical components left in the water film to enable a self-sustaining technique. The technology allows for conserving in space and investment costs in exhaust gas aftertreatment facilities.