Removal of low-concentration formaldehyde in air by DC corona discharge plasma

The effects of discharge polarity, discharge electrode configuration, gas composition and downstream catalyst on the removal of low-concentration HCHO in air were systematically investigated in a link tooth wheel-cylinder plasma reactor energized by a DC power. Experimental results show that the positive DC corona discharge is much more effective in removing HCHO as compared to the negative one. The discharge electrode configuration significantly influences the energy input to the plasma reactor. For a given specific energy density (SED), longer reaction zone favors the HCHO conversion; however, the HCHO conversion is almost constant in spite of the different discharge electrode configurations within a fixed reaction zone. The conversion of HCHO increases with the increase of gas humidity, and decreases with increasing coexisting toluene in the gas stream. On the other hand, introduction of MnO_x/Al₂O₃ catalyst downstream the plasma reactor significantly enhances the HCHO conversion and reduces the O₃ emission.