Removal of $\hbox{NO}_{x}$, $\hbox{SO}_{2}$, and Hg From Simulated Flue Gas by Plasma - Absorption Hybrid System

The simultaneous removal of NO
x
, SO
₂
, and Hg from simulated flue gas by a plasma-absorption hybrid system was investigated. In the nonthermal plasma reactor, NO could be effectively oxidized to NO
₂
. However, Hg
⁰
oxidation was significantly restrained since NO concentration and its reactivity with O
₃
are much higher than those of Hg
⁰
. In the absorber, SO
₂
and NO
₂
were absorbed by (NH
₄
)
₂
SO
₃
solution, in which the S(IV) ions (SO
₃
^2-
and HSO
₃
^-
) were found to be dominant for NO
₂
absorption. The S(IV) ions were significantly oxidized during the absorption, causing an increase in NO
₂
concentration with operating time. However, the addition of S
₂
O
₃
^2-
inhibited the S(IV) oxidation and promoted the removal of NO
₂
. With a followed electric mist eliminator, the NH
₃
slipped from the absorber can be captured, and Hg
⁰
was efficiently oxidized, which can be further removed by water absorption.