Simultaneous absorption of NOx and SO₂ in oxidant‐enhanced limestone slurry

Abstract

In this article, a study of simultaneous absorption kinetics of NOx and SO2 in oxidant‐enhanced limestone slurry using sodium chlorite as additives is presented. The laboratory‐scale experiments were performed in a double‐stirred tank reactor, and the effect of inorganic ions and operating parameters on absorption rates was investigated. The results indicate that NOx absorption rate shows a positive order with respect to NO (0.573), SO2 (0.278), and NaClO2 (0.194), whereas SO2 absorption rate shows a first order with respect to SO2 and zero order for both NO and NaClO2 under a typical limestone wet flue gas desulfurization operating condition. Higher pH leads to a decrease of NOx absorption rate but has no significant influence on SO2 absorption. The SO2 absorption rate decreases with the increase of temperature, whereas the NOx absorption rate remains nearly constant. S(IV) in the slurry reduces the NOx absorption rate dramatically and suppresses the SO2 absorption, whereas the presence of nitrate ions can increase the absorption rate of both SO2 and NOx. High concentration of Cl− has a positive effect on the SO2 absorption, whereas it has a negative effect on NOx absorption rate. Additionally, Mg2+ and F− have no impact on SO2 and NOx absorption rates. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1171–1179, 2014

Reaction performance study on denitration in aqueous solution of the dual oxidant (H2O2/S2)

“…Learn from the existing research, the apparent activation energies of NO removal by using NaClO 2 solution and H 2 O 2 /NaOH solution were 42.5 kJ mol 21 and 27.8 kJ mol 21 [24,25]. Apparently, the apparent activation energies of NO removal by using NaClO 2 solution and H 2 O 2 /NaOH solution were higher than that the dual oxidant (H 2 O 2 /S 2 O 22 8 ) solution studied in this paper, which was because the molecular kinetic energy were greatly enlarged by highly reactive free radicals in the dual oxidant (H 2 O 2 / S 2 O 22 8 ) system, thereby reducing the reaction barrier.…”

“…The proposed mechanism could be that in the dual oxidant (H 2 may almost translate into OH• by OH -, OH• was the dominant active radical at the inflexion point. In the slow-reaction zone, the quenching reactions of these free radicals in the dual oxidant (H 2 O 2 /S 2 O 22 8 ) system may become significant, leading to a decrease in NO reaction rate.…”

“…adding the oxidants into the aqueous solution. So far, the possible liquid oxidants, such as NaClO 2 , NaClO , CaClO 2 , KMnO 4 , H 2 O 2 , Fenton , and Na 2 S 2 O 8 have been used to study their denitration performance by using wet scrubbing. These oxidants can oxidize the insoluble NO into the soluble nitrogen‐containing compound, which can be removed by using wet scrubbing, but these problems of the generation of toxic by‐products such as ClO 2 and MnO 2 , the difficult regeneration of Fe 2+ and the high cost of the oxidizing agents restrict their industrial application.…”

Optimizing the characteristics of calcium sulfate dihydrate in the flue gas desulfurization process: Investigation of the impurities in slurry-Cl-, Fe3+, Mn2+

“…The limestone's components change with the producing area. The major impurities of limestone were MgCO 3 , SiO 2 , Al 2 O 3 and Fe 2 O 3 [4,[17][18][19]. The data in Figure 2 The investigation of the four types of limestone indicated that limestone components had significant effects on the moisture content of DH products and moderate effects on desulfurization efficiency (relevant data is shown in Figure 3a).…”

“…An absorber is costly and time-consuming. Thus, bubbling reactors are often used in lab-scale experiments for FGD studies [4]. In the bubbling reactor, flue gases bubble through the slurry, and SO 2 is absorbed by the slurry.…”