Application and Economic Analysis of the Multi-Pollutants Removal Technology Incorporated with Ozone Oxidization and Alkali Solution Adsorption - Simultaneous Multi-Pollutants Removal in Flue Gas by Ozone - page 98

owing to a variety of advantages, namely, the most effective approach to achieve
multi-pollutants removal of NO x , SO 2 , Hg, HCl, and HF in a aqueous scrubbers,
more economical, lower retrofit and running cost. As mentioned previously, in
general, above 90% of NO x , more than 95% of SO 2 , and no less than 85% of Hg
can be removed, based on the testing results of some industrial applications. And
the high NO x abatement efficiency is actually attained by the combination of
combustion control in the furnace and ozone oxidation in the flue gas; this
combination strategy can greatly reduce the O 3 consumption, thereby saving
sharply the cost in NO x abatement.
Take a 300 MWe unit with typical operational parameters and multi-pollutants
emission levels, Table 5.3 lists the O 3 requirement and energy consumption for the
proposed multi-pollutants simultaneous removal technology, based on our
calculations. Reducing NO x emissions from 600 to 400 mg/m 3 (at 6% O 2 )
necessitates an O 3 consumption of 257.1 kg/h, which exceeds a little the output of
a 200 kg/h large-scale ozone generator for sale on the current market. Two types
of gas sources, i.e., air and oxygen, can be used in ozone generators. When air is
used, the N 2 in air will consume most of the energy during the discharge process
(6814.29 kW) because of high-energy consumption in the ozone generation, which
can reach up to 26.5 kW per kg ozone. The unit flue gas energy consumption
therefore reaches up to 5.68 W/(Nm 3 ), which accounts for 2.27% of the total
electricity generation. Using oxygen as the gas source, although additional energy
consumption needs in preparing the oxygen source, the energy consumption of
ozone generation significantly reduces to a minimum of 6 kW per kg ozone in the
present market. Consequently, the unit flue gas energy consumption reduces
greatly to 1.91 W/(Nm 3 ), which accounts for only 0.76% of the electric power
generation. This means that 66.5% of the power consumption can be saved by
using oxygen instead of air as a gas source in the ozone generation process.
Obviously, the key factor to reducing the operational cost in practical applications is
to choose oxygen as the gas source and to develop a large-scale ozone generator with
low power consumption.
Obviously, it is a better choice to adopt the ozone oxidation technology
integrated with NO x control strategies during the fuel combustion process (such as
low-NO x burners, air-staging combustion, and fuel reburning) for a reasonable
investment. From Table 5.4 compares various schemes with ozone application for