The reduction of the nitrogen oxides NO and N2O to molecular nitrogen in the presence of iron, its oxides, and carbon monoxide in a hot fluidized bed

Hayhurst, A.N.; Lawrence, A.D.

doi:10.1016/s0010-2180(97)00085-0

Cited by 77 publications

(63 citation statements)

References 11 publications

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“…Lissianski et al [9,23,30], who used a pilotscale combustion chamber, and Su et al [24], who used a laboratory-scale facility, both focused on the use of iron or iron oxide in pulverized coal combustion chambers. Fennel et al [12,17], who used the TGA method, Hayhurst and Lawrence [19], who used a laboratory-scale FB reactor, and Hayhurst and Ninomiya [15], who used a laboratoryscale FB reactor, suggested the use of iron as a de-NO x agent in fluidized-bed combustors. Although some necessary model simplifications have been adopted, the results obtained in this work can be assumed to be useful for the application of iron as the active species for NO x removal from grate combustion chambers.…”

Section: Application Of Iron In the De-nox Process: A Brief Analysismentioning

confidence: 99%

“…Moreover, wustite (Fe x O) formation is also possible because this phase is not stable at temperature below 572°C and can be next decomposed into magnetite and iron [7]. Hayhurst and Lawrence speculated that the iron oxide is mainly FeO, with a small amount of Fe 2 O 3 [19]. Su et al [20,21] found that iron oxides content depended on temperature range.…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, the kinetic coefficients of the chemical reaction between NO and Fe have been determined as a function of temperature [9,13,15,17,19,23]. Recently, Fennell et al [12] reported a study of the latter stages of reaction (1), when the process has been controlled by the diffusion of iron ions through an oxide layer around the iron particle.…”

Section: Introductionmentioning

confidence: 99%

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

Lasek

2014

Heat Mass Transfer

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The limitation of nitrogen oxides (NO x ) emissions from stationary combustion chambers is still an important issue in the field of the natural environment protection. This paper describes the reduction of NO x in the presence of iron. A few new aspects of research describing the utilization of iron as an additive that influences NO x reduction at high temperatures are presented. In particular, the influence of the excess air number (k) on the NO x removal efficiency in the presence of Armco iron was determined. A [50 % increase in the efficiency was achieved at k = 0.6. The research was conducted using N 2 / NO mixed with a flue gas from carbon monoxide combustion. In addition, a correction factor (Arrhenius-type empirical equation) was determined, which enabled the calculation of the oxygen influence on the inhibition of the de-NO x reaction in the presence of iron. The NO x reduction was also tested using bearing steel samples. Finally, the use of iron in de-NO x processes under different combustion conditions is briefly reviewed and analyzed.

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Section: Application Of Iron In the De-nox Process: A Brief Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Lasek

2014

Heat Mass Transfer

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“…10 From the vacancy diffusion theory, more vacancy would occur because of more atom migration at higher temperature, resulting in more ZVI atom diffused to react with NO. Table 1 presents the breakthrough time and volume (as BV) for different temperatures for a flow rate of 0.1 L/min, BV of 0.170 cm 3 , and EBCT of 0.0679 sec. These numbers can be used as a reference to estimate the operational time when scaled up.…”

Section: Resultsmentioning

confidence: 99%

“…[3][4][5][6][7][8] Hayhurst and Lawrence 3 studied the kinetics for NO x (NO and N 2 O) removal at temperatures of 973 and 1173 K in a fluidized bed using a 139 -400 m ZVI particle for influent NO concentration of 1350 -1470 ppm. They pointed out that the ZVI and NO interaction is a redox reaction with the following possibilities:…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of NO_x Removal from Flue Gas by Zero Valent Iron

Chen

Cheng

Chang

et al. 2006

Journal of the Air & Waste Management Association

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Chemical reaction between nitric oxide (NO) and zero valent iron (ZVI) was studied in a packed-bed column process with high temperatures based on ZVI strong reducing abilities. For six controlled temperatures of 523-773 K and 400 ppm of NO (typical flue gas temperature and concentration), under short empty bed contact time ([EBCT] 0.0226 -0.0679 sec), NO was completely removed for temperature of 573-773 K but not for 523 K. Breakthrough curves were conducted for the five working temperatures, and the results indicated that NO reductions by ZVI were varied from 2 to 26.7 mg NO/g ZVI. Higher temperature and longer EBCT achieved better NO removal efficiency. X-ray diffraction (XRD) and electron spectroscopy for chemical analysis (ESCA) were conducted to analyze the crystal structure and oxidation state of the reacted ZVI. Three layers of iron species were detected by XRD: ZVI, Fe 3 O 4 , and Fe 2 O 3 . ZVI was the most prevalent species, and Fe 3 O 4 and Fe 2 O 3 were less from the XRD analysis. By ESCA, the oxidation state on the reacted ZVI surface was determined, and the species was identified as Fe 2 O 3 , which is the most oxidizing species for iron. Therefore, three layers from the ZVI core to the ZVI surface can be identified: ZVI, Fe 3 O 4 , and Fe 2 O 3 . Combining the results from XRD and ESCA, the mechanisms for ZVI and NO can be proposed as two consecutive reactions from lower oxidation state (ZVI) in the core to higher oxidation state on the iron surface (Fe 2 O 3 ):andBecause there was only Ͻ5% ZVI used to remove NO comparing to theoretical ZVI used based on the proposed stoichiometry, it can be concluded that the heterogeneous reaction only occurred on the ZVI surface instead of on bulk of the ZVI.

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Tribochemische Aktivierung von Eisenoxid für die Reduktion von NO mit CO: Wie Gitterbaufehler die katalytische Aktivität beeinflussen können

et al. 2000

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Die Spaltung der NO x -Moleküle in ihre Elemente ist eine wichtige Aufgabe der Umweltkatalyse. [1] Massive Metalloxide sind prinzipiell eine geeignete Substanzklasse [2] und daher schon seit langem als mögliche Katalysatoren in der Diskussion, [3] waren aber weder genug aktiv noch hinreichend stabil gegenüber Reduktion.Das nichttoxische Eisenoxid chemisorbiert NO sehr gut [4] und ist daher ein aussichtsreiches Material, sofern die aktiven Zentren durch ein Reduktionsmittel wie CO regeneriert werden können. [5] Eisenoxid-Nanoteilchen werden derzeit intensiv bei NO-Reduktionsprozessen untersucht. [6] Nichtstationäre kinetische Messungen [7] ergaben, dass Hämatit (a-Fe 2 O 3 ) NO an Defekten des Sauerstoffteilgitters adsorbiert und aktiviert. [8] Über einen intermediären Schritt zu N 2 O wird schlieûlich N 2 gebildet. Die Regeneration des aktiven Zentrums erfolgt durch Reaktion von CO mit Sauerstoff. Eisenoxid weist gegenüber vielen anderen Katalysatoren eine hohe Selektivität zugunsten von N 2 , aber nicht von N 2 O auf, [6,9] was für die Anwendung als Umweltschutzkatalysator von groûer Bedeutung ist.Wird die Reaktion von CO nicht auf die aktiven Zentren der Oberfläche beschränkt, so läuft die Chemie der Hochofenreduktion von Eisenoxid ab und der Katalysator wird schnell desaktiviert. Dieser Reaktionszweig erfordert eine Diffusion von Eisen aus dem Volumen an die Oberfläche. [10] Somit ist es erforderlich, einerseits die Zahl der aktiven Zentren zu maximieren, aber auch die Volumendiffusion von Eisen zu kontrollieren.Die tribochemische (d. h. durch Zerreiben hervorgerufene) Aktivierung von käuflichem Hämatit führte zu einer deutlichen Verbesserung der Materialeigenschaften als Katalysator. Das Umsatz-Temperatur-Profil (Abbildung 1) zeigt eine erhebliche Erhöhung der katalytischen Aktivität nach dem Mahlen. Bei der Einsatztemperatur des nichtaktivierten Oxids weist die aktivierte Probe bereits ihre maximale Aktivität auf. Relativ zu geträgerten Oxidpartikeln, [7] die zu aktiven Katalysatoren mit einer inneren Oberfläche von 302 m 2 g À1 führen, ist der hier vorgestellte Katalysator mit einer inneren Oberfläche von nur 8.2 m 2 g À1 erheblich aktiver, wie der Vergleich der Messwerte bei 50 % Umsatz (hier 482 K, geträgerte Probe 578 K) und bei 80 % Umsatz (hier 532 K, geträgerte Probe 615 K) ausweist. Der Vergleich der nahezu gleichartig verlaufenden NO-Umsatz-und CO 2 -Ausbeutekurven in Abbildung 1 macht die ausgezeichnete Selektivität [11] des Katalysators zugunsten von N 2 deutlich, die hier auch ohne Trägerung auf hoch oberflächenreicher Aktivkohle Abbildung 1. Umsatz-Temperatur-Profil der NO-CO-Reaktion an reinen, nichtaktivierten (A) und aktivierten Eisenoxiden (B). (Bei B/CO 2 handelt es sich nicht um die Umsatz-, sondern die Ausbeutekurve.) Durch die Aktivierung wurde die Brunauer-Emmett-Teller(BET)-Oberfläche nicht messbar gegenüber dem Ausgangswert verändert. Die modifizierte Verweilzeit [7] betrug in allen Fällen 100 kg s mol À1 .

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The reduction of the nitrogen oxides NO and N2O to molecular nitrogen in the presence of iron, its oxides, and carbon monoxide in a hot fluidized bed

Cited by 77 publications

References 11 publications

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

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

Mechanisms of NO_x Removal from Flue Gas by Zero Valent Iron

Tribochemische Aktivierung von Eisenoxid für die Reduktion von NO mit CO: Wie Gitterbaufehler die katalytische Aktivität beeinflussen können

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The reduction of the nitrogen oxides NO and N2O to molecular nitrogen in the presence of iron, its oxides, and carbon monoxide in a hot fluidized bed

Cited by 77 publications

References 11 publications

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

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

Mechanisms of NOx Removal from Flue Gas by Zero Valent Iron

Tribochemische Aktivierung von Eisenoxid für die Reduktion von NO mit CO: Wie Gitterbaufehler die katalytische Aktivität beeinflussen können

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Mechanisms of NO_x Removal from Flue Gas by Zero Valent Iron