Ammonia oxidation at high pressure and intermediate temperatures. (1st October 2016)

• Record Type: Journal Article
• Authors: Song, Yu; Hashemi, Hamid; Christensen, Jakob Munkholt; Zou, Chun; Marshall, Paul; Glarborg, Peter
• Is Part Of: Fuel. Volume 181(2016)
• Page Start: 358
• Page End: 365
• Publication Date: 2016-10-01
• Subjects: NH3 oxidation -- High pressure -- Flow reactor -- H2NO + O2 rate constant -- Kinetic model; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2016.04.100
• Languages: English
• ISSNs: 0016-2361

Abstract

Abstract: Ammonia oxidation experiments were conducted at high pressure (30 bar and 100 bar) under oxidizing and stoichiometric conditions, respectively, and temperatures ranging from 450 to 925 K. The oxidation of ammonia was slow under stoichiometric conditions in the temperature range investigated. Under oxidizing conditions the onset temperature for reaction was 850–875 K at 30 bar, while at 100 bar it was about 800 K, with complete consumption of NH3 at 875 K. The products of reaction were N2 and N2 O, while NO and NO2 concentrations were below the detection limit even under oxidizing conditions. The data were interpreted in terms of a detailed chemical kinetic model. The rate constant for the reaction of the important intermediate H2 NO with O2 was determined from ab initio calculations to be 2.3 × 10 2 T 2.994 exp(−9510 K/T) cm 3 mol −1 s −1 . The agreement between experimental results and model work was satisfactory. The main oxidation path for NH3 at high pressure under oxidizing conditions is NH3 ⟶ + OH NH2 ⟶ + HO 2, NO 2 H2 NO ⟶ + O 2 HNO ⟶ + O 2 NO ⟶ + NH 2 N2 . The modeling predictions are most sensitive to the reactions NH2 + NO = NNH + OH and NH2 + HO2 = H2 NO + OH, which promote the ammonia consumption by forming OH radicals, and to NH2 + NO = N2 + H2 O and NH2 + NO2 = N2 O + H2 O, which are the main chain-terminating steps.