Proposal and verification of a kinetic mechanism model for NO_x removal with hydrazine hydrate

Abstract

A relatively precise kinetic mechanism of NO x reduction using N 2 H 4 ÁH 2 O in a selective non-catalytic reduction process was proposed and verified by experiment in this study. The dominant radicals and reactions were confirmed, and the proper ranges of key parameters were determined through sensitivity analysis. Both experimental and simulation results show that the effective temperatures exhibit a bimodal distribution with the optimum temperatures being approximately 893 and 1248 K and the lower temperature window falling in the range of 848-973 K. The optimum residence time of the reaction was 0.2-0.35 s under the research conditions, and a longer residence time would lead to the regeneration of NO x . The normalized stoichiometric ratio (NSR) of 3.0 corresponded to the lowest temperature window, and a higher NSR value would make the temperature window shift to a higher temperature range. This kinetic mechanism model for the N 2 H 4 ÁH 2 O-based De-NO x process will serve its precise application. V C 2014 American Institute of Chemical Engineers AIChE J, 61: [904][905][906][907][908][909][910][911][912] 2015

Influences of activation agent impregnated sewage sludge pyrolysis on emission characteristics of volatile combustion and De-NOx performance of activated char

“…When checking the function of the chars as an absorbent, no reducing agent was added and the inlet and outlet NOx concentrations were analyzed to define the difference. When evaluating the catalytic effect of these chars, hydrazine hydrate solution was used as the reducing agent [25]. Hydrazine hydrate solution has been reported to be more active at lower temperatures [26].…”

“…8). The De-NOx reducing agent used here was not a conventional reducing agent such as ammonia or urea, but a more active reducing agent, namely, hydrazine hydrate solution for its activity at low temperatures [25]. The different SC samples were used as either absorbents or catalysts and the De-NOx temperature was controlled at 250°C.…”

Hydrazine-enhanced NO conversion in a pulsed corona discharge plasma (PCDP) reactor: Behaviors and mechanism

“…15,16 The dissociation energy of the N-N bond of hydrazine is 2.6 eV, which is significantly lower than that of O 2 (5.1 eV), H 2 O (4.8 eV) or NH 3 (3.8 eV). 11 Moreover, hydrazine is easily oxidized to N 2 and H 2 O, avoiding secondary pollution of the "ammonia slip.…”

Improved NO removal from flue gas by hydrazine and its mechanism analysis

“…studied the reduction behavior of NO by using N 2 H 4 as a reducing agent in the presence of 12% O 2 at a molar ratio of NH 2 to NO (normalized stoichiometric ratio, NSR) of 4.0 and observed an NO removal ratio of 40–60% at 500–700 °C within the range 450–750 °C. Regarding the mechanism investigation, Hong et al . adopted CHEMKIN‐FLUENT to model the N 2 H 4 –NO–O 2 reaction, revealing a bimodal distribution of the temperature window falling in the ranges 575–700 and 927–1000 °C when the O 2 content was 9.8% and the NSR was 4.0.…”

“…Much effort has been devoted to finding a replacement for NH 3 , urea and CA. Hydrazine (N 2 H 4 ) has been demonstrated to be highly reactive with NO in the presence of excess O 2 in a temperature window about 300 °C lower than that of the pure NH 3 process . On a laboratory scale, Azuhata et al .…”