Photochemical Removal of NO, NO2, and N2O by 146 nm Kr2 Excimer Lamp in N2 at Atmospheric Pressure

Abstract

The photochemical removal of NO, NO2, and N2O was investigated in N2 using a 146 nm Kr2 (25 mW cm−2) excimer lamp. The results obtained were compared with those obtained using 172 nm Xe2 (50 or 300 mW cm−2) excimer lamps. The removal rates of NO and NO2 at 146 nm were 11 and 36% slower than those at 172 nm, respectively. On the other hand, the removal rate of N2O at 146 nm was 21 times faster than that at 172 nm. The differences in the removal rates are discussed in terms of the absorption coefficient at each wavelength and effects of photoabsorption by N2 at 146 nm. By the addition of a small amount of O2 into an N2O/N2 mixture, the removal rate of N2O at 146 nm decreased greatly. On the basis of these facts, it was concluded that the 146 nm excimer lamp is especially useful for the N2O removal in N2 at atmospheric pressure.

Novel Process of Simultaneous Removal of Nitric Oxide and Sulfur Dioxide Using a Vacuum Ultraviolet (VUV)-Activated O2/H2O/H2O2 System in A Wet VUV–Spraying Reactor

“…The byproducts NO 2 – and SO 3 2– were not found in reaction solution. Besides, according to the results of Ye et al and Tsuji et al − and the present results about SO 2 direct photolysis (as shown in Figure b), some elemental sulfur may be also produced in the reaction solution. However, it is difficult to determine its content because of its very low yield in the liquid phase and the complexity of the reaction solution.…”

“…According to the results of Tsuji’s studies − and Ye et al, NO and SO 2 may be also directly decomposed by VUV light radiation according to following eqs –. …”

“…Light-induced advanced oxidation processes have demonstrated good development prospects in the area of emission reduction of NO x and SO 2 from flue gas. ,,,,,− Several semiconductor-based photocatalytic oxidation processes have been developed for removal of NO x and SO 2 from flue gas and have exhibited good removal performance for NO x and SO 2 . ,− However, some drawbacks, such as instability and low activity of photocatalyst, low penetration of UV light in solids, and restriction of low concentrations of pollutants (photocatalytic oxidation processes can be only used for the treatment of pollutants with low concentration), hinder their industrial applications. , In recent years, several photochemical oxidation processes, such as dry VUV radiation, ,− wet UV–H 2 O 2 ,, and wet UV–Fenton­(-like) processes, ,, have been developed to remove NO x and SO 2 from flue gas. Tsuji et al − successfully used 172 nm Xe 2 and 146 nm Kr 2 excimer lamps as VUV sources to remove SO 2 , NO, and NO 2 in N 2 and air without using any expensive catalysts, which shows that VUV is an effective light source for the removal of SO 2 , NO, and NO 2 . However, Tsuji’s studies − did not consider the effect of VUV irradiation in the simultaneous presence of O 2 and H 2 O, which are the two main components of actual flue gases.…”

“…Tsuji et al − successfully used 172 nm Xe 2 and 146 nm Kr 2 excimer lamps as VUV sources to remove SO 2 , NO, and NO 2 in N 2 and air without using any expensive catalysts, which shows that VUV is an effective light source for the removal of SO 2 , NO, and NO 2 . However, Tsuji’s studies − did not consider the effect of VUV irradiation in the simultaneous presence of O 2 and H 2 O, which are the two main components of actual flue gases. Ye et al determined for the first time the key reactive oxygen species that are generated by VUV radiation in simulated flue gas (N 2 , O 2 , CO 2 , and H 2 O) and evaluated the key parameters that affect the yield of the oxidants.…”

Effects of experimental parameters on simultaneous removal of SO2 and NO by VUV/H2O2 advanced oxidation process in a pilot‐scale photochemical spraying tower

“…Some researchers have inferred that VUV light irradiation may directly decompose SO 2 and NO by oxidation removal reactions . This assumption was verified by the experimental results of Tsuji, where they found the deposition of sulfur powders on the walls of the reaction chamber after photolysis of SO 2 in N 2 under VUV irradiation.…”