Catalysis Reduction of NO and HCN/NH₃ during Reburning: a Short Review

Abstract

Reburning is effective to control NO emission. The paper presents a short review on recent research on catalysis reduction of NO and HCN/NH3by some metal and their oxides during reburning. The major difficulties that limit NO reduction efficiency by reburning involve the re-oxidation of the intermediate products during reburning, HCN/NH3and char nitrogen to NO. So far, results showed that Fe2O3could reduce the formation of HCN/NH3after reburning and metallic iron could directly reduce NO to N2. Temperature and co-existing gases influenced the catalysis performance of Fe and its oxides. Detailed mechanism and kinetics of the reactions should be further investigated.

Investigations of the reduction of NO to N2 by reaction with Fe under fuel-rich and oxidative atmosphere

“…The influence of the aforementioned reaction on the NO conversion was intentionally omitted to emphasize the role of iron as an additive that supports the reburning process. The experiments were performed this way because the influence of temperature, reburning fuel type, reburning fuel heat input and other process parameters on the efficiency of NO reduction has already been intensively investigated [30][31][32][33], whereas relatively few studies on the influence of iron on the reburning efficiency have been published [9,14,23,24]. The efficiency of NO x reduction in the presence of iron as a function of the excess air numbers was calculated according to Eq.…”

“…It was recently discussed by Lasek and Gradon [16] and Su et al [14]. Also other researchers confirmed that type of iron oxide (or oxides), created at NO presence, is still open question [12,14,17]. For example, Fennel and Hayhurst [17] concluded that main product of iron oxidation in NO/ N 2 mixture may be magnetite (Fe 3 O 4 ).…”

“…A survey of the literature [12][13][14] suggests that relatively few studies on the reduction of NO x in the presence of iron (or its oxides) have been reported. NO is assumed to be oxidized by metallic iron via the reaction:…”

Pollutant and Corrosion Control Technology and Efficient Coal Combustion

“…The reduction of NO by combustion intermediate, i.e., CO over the surface of oxides of iron, ,,− was validated by the recorded radial and axial profile measurements from the pilot scale 100 kW th furnace combustion tests at 15% excess air for 3.4% by volume addition of the additive. Convincing evidence specifies better results toward de-NO x using iron oxides in conjunction with other commercially available technologies, i.e., reburning, advance reburning, and selective noncatalytic reduction. − The in-flame measurement of CO at the module 1 (port 1) position confirmed higher concentrations with Silanite (Figure A) compared to coal baseline measurement at the same location. However, later at the module 2 (port 2) location, the values were recorded lower than the respective coal baseline measurements.…”

“…Convincing evidence specifies better results towards de-NOx using iron oxides in conjunction with other commercially available technologies i.e. reburning, advance reburning, selective non-catalytic reduction [29][30][31] . The inflame measurement of CO at the module 1 (port 1)…”