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(compared with HCl) has been experimentally confirmed by Gao et al . [3] . When
O 3 exists, the reaction paths in Fig. 3.7 suggest that mercury oxidation dominantly
depends on O 3 , weakly dependent on Cl. Similarly, the reaction between O 3 and
Hg is facilitated by the medium NO 3 . And the NO 3 generation needs excessive O 3
from the previous analysis. Fortunately, the concentration of mercury is far lower
than that of NO x in the real-furnace flue gas. When injecting O 3 into flue gas for
the NO x oxidation, NO 3 can be spontaneously generated and only a little of the
generated NO 3 can complete the mercury oxidation. Consequently, NO x , SO 2 , and
mercury oxides are simultaneously removed through WFGD or alkaline scrubbers.
3.3 Oxidation Experimental Results
3.3.1 Experimental Setup
Although much crucial chemical kinetics information between O 3 and
NO x /SO 2 /Hg has been essentially elaborated above, further experimental
investigations on oxidation reactions between them are still needed, so as to
uncover the oxidation mechanisms more clearly. Accordingly, an ozone oxidation
experimental system was established and shown in Fig. 3.8, which includes an
ozone generator, mercury generator, quartz flow reactor, glass-made alkaline
washing tower, and online gas analysis system. Ozone was generated by a DBD
device with 3.7 - 4.0 kV AC voltage and 5 kHz frequency. The O 3 output
concentration was continuously monitored by an ozone analyzer with a measuring
range of 0 - 10000 ppm and precision of 1 ppm.
The simulated flue gas was prepared through N 2 , along with a small amount of
NO (0.6 vol.%) and SO 2 (1.5 vol.%). Oxygen was present in the main flow of the
current test. Given that ozone was generated from an air source, oxygen was
inevitably present in the reaction system. The gas flow rate was controlled by a
mass flow controller (Qixing Huangchuang Co., China). The elemental mercury
was generated from a mercury osmotic tube (VICI Metronics Co., USA), which
was heated in a thermostatic water bath with 300 mL/min N 2 as the carrier gas.
The mixture of NO, SO 2 , Hg, and N 2 reacted with O 3 in the quartz flow reactor,
which was located in an electrically heated horizontal furnace with a heating
length of approximately 600 mm. The quartz flow reactor, with its configuration
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