Environmental Engineering Reference
In-Depth Information
1. Boiler flue; 2. Heat exchanger; 3. SO 2 scrubber; 4. Ozone generator; 5. Liquid buffer
tank; 6. Caustic circulation pump; 7. Lye spray stable volt; 8. Process water; 9. Liquid
tank; 10. Crystallizing system; 11. NO x scrubber; 12. Liquid buffer tank; 13. Caustic
circulation pump; 14. Lye spray stable volt; 15. Crystallizing (collect) system
Fig. 4.16 Schematic process of desulfurization and denitrification through ozone oxidization
combined with two-tower scrubbing [27]
4.8 Summary
In this chapter, the removal performance of dissoluble high-valence NO x
(specifically NO 2 ) via an alkali liquid scrubbing method was investigated, in
addition to (i) interactions between NO x and SO 2 in adsorption reactions and (ii)
the changing trends of the adsorption product species and concentration.
Accordingly, effects of various factors such as the pH value, reductive
tetravalent-S existence and its concentration, NO 2 initial concentration, ozone
injection dosage, and interactions of NO 2 and SO 2 were experimentally evaluated
so as to determine favorable NO x and SO 2 removal conditions. Important results
are summarized as below.
(1) The NO 2 absorption is not obviously affected by the pH value. The NO 2
removal efficiency is strongly dependent on the NO 2 hydrolysis reaction and
solubility coefficient. Accordingly, nitric acid and nitrous acid are the main
absorption products. Exceptionally, the NO 2 removal efficiency decreases a little
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