Deactivation and regeneration of a commercial SCR catalyst: Comparison with alkali metals and arsenic

Peng, Yue; Li, Junhua; Si, Wenzhe; Luo, Jinming; Wang, Yu; Fu, Jie; Li, Xiang; Crittenden, John C.; Hao, Jiming

doi:10.1016/j.apcatb.2014.12.005

Cited by 188 publications

(105 citation statements)

References 51 publications

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“…Thus, this method of analysis, using pre-exponential factors instead of rate constants, gives a clearer picture of the deactivating effect. Others [1,2] have also observed similar trends.…”

Section: Discussionsupporting

confidence: 58%

“…However, deactivation of the catalyst by compounds in the fly ash will then become a serious problem. Fly ash contains many potentially poisonous compounds, of which alkali metals are of the greatest concern [2][3][4]. These will cause deactivation of the catalysts, by blocking the Brønsted acid sites, as in the case of the burning forest residues [3,5].…”

Section: Introductionmentioning

confidence: 99%

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Deactivation and Characterization of SCR Catalysts Used in Municipal Waste Incineration Applications

Brandin

Odenbrand

2017

Catal Lett

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changes in surface area (8% decrease in BET surface area over 2311 h) and pore structure were small, while the change in activity was considerable. The apparent pre-exponential factor was 1.63 × 10 5 (1/min) in the most deactivated catalyst, compared to 2.65 × 10 6 (1/min) in the fresh catalyst, i.e. a reduction of 94%. The apparent activation energy for the fresh catalyst was 40 kJ/mol, decreasing to 27 kJ/mol with increasing deactivation. Characterization showed that catalytic poisoning is mainly due to decreased acidity of the catalyst caused due to increasing amounts of Na and K.Abstract Catalysts used for selective catalytic reduction were deactivated for various times in a slipstream from a municipal solid waste incineration plant and then characterized. The activity for NO reduction with NH 3 was measured. The Brunauer-Emmett-Teller surface areas were determined by N 2 adsorption from which the pore size distributions in the mesopore region were obtained. Micropore areas and volumes were also obtained. The composition of fresh and deactivated catalysts as well as fly ash was determined by atomic absorption spectroscopy and scanning electron microscopy with energy dispersive X-ray analysis. The

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“…Thus, this method of analysis, using pre-exponential factors instead of rate constants, gives a clearer picture of the deactivating effect. Others [1,2] have also observed similar trends.…”

Section: Discussionsupporting

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Deactivation and Characterization of SCR Catalysts Used in Municipal Waste Incineration Applications

Brandin

Odenbrand

2017

Catal Lett

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“…6) is an average of the entire catalyst samples, and the alkali analysis shows close to a linear increase versus time on stream. Earlier studies [2,3] have shown a strong correlation between the alkali content and the deactivation rate of SCR catalysts. Especially catalyst used in, alkaline rich, highly dusty environments like in biofuel and waste combustion are subjected to strong deactivation.…”

Section: Discussionmentioning

confidence: 99%

“…Among them alkali metals are of a major concern [2-5]. They cause deactivation of the catalysts, by blocking the Brønsted acid sites, in the same way as for applications burning forest residues [2,6].We have studied SCR catalysts in various applications since the mid 80ies [7,8]. In one paper, we published the effect of lead on the activity [9].…”

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Poisoning of SCR Catalysts used in Municipal Waste Incineration Applications

Brandin

Odenbrand

2017

Top Catal

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mobile applications like marine and automotive diesel engines.During this period, from the 60s till today, a significant change in the feedstock for the stationary boilers has occurred. Due to the concern about greenhouse gases, the use of renewable fuel has increased, in order to reduce the use of fossil fuel. Renewable fuel can be, for instance, woody biomass and forest residues, municipal, industrial or agricultural waste.While the previous use of fossil gas, diesel or oil produced a rather particulate free flue gas, the new fuels contain larger amounts of alkali metals. Thus, they generate a large portion of fly ash. A recent study compares the use of SCR to SNCR for reduction of nitrogen oxides [1]. The authors say that if the NO x level for waste incinerators would be lowered to 100 mg/Nm 3 , it will become necessary to use SCR instead of SNCR. For new installations, the catalyst should be placed after the boiler in a high dust position. This means that fly ash will pass through the catalyst bed via the monoliths channels, resulting in a close contact between the catalyst and the fly ash. There are many potentially poisonous compounds in the fly ash. Among them alkali metals are of a major concern [2-5]. They cause deactivation of the catalysts, by blocking the Brønsted acid sites, in the same way as for applications burning forest residues [2,6].We have studied SCR catalysts in various applications since the mid 80ies [7,8]. In one paper, we published the effect of lead on the activity [9]. Earlier results from deactivation studies on diesel engine driven power plants in Sweden [10] show that there is an activation after about 900 h on stream. In that case, the conversion increased from 85 to 92% at 350 °C. In an earlier study we showed [11] that gas phase sulphating by 500 ppm SO 2 in 500 ppm NO, 4% O 2 and 4-5% H 2 O with He as Abstract A commercial vanadia, tungsta on titania SCR catalyst was poisoned in a side stream in a waste incineration plant. The effect of especially alkali metal poisoning was observed resulting in a decreased activity at long times of exposure. The deactivation after 2311 h was 36% while the decrease in surface area was only 7.6%. Thus the major cause for deactivation was a chemical blocking of acidic sites by alkali metals. The activation-deactivation model showed excellent agreement with experimental data. The model suggests that the original adsorption sites, from the preparation of the catalyst, are rapidly deactivated but are replaced by a new population of adsorption sites due to activation of the catalyst surface by sulphur compounds (SO 2 , SO 3 ) in the flue gas.

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Influence of sodium on deactivation and regeneration of SCR catalyst during utilization of Zhundong coals

Wang

et al. 2016

Asia-Pacific J Chem Eng

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Zhundong coals have a super huge reserve and many excellent characteristics. However, the sodium content in Zhundong coal is extremely high, which can accelerate the deactivation of the V‐W‐TiO2 selective catalytic reduction (SCR) catalysts. In the present work, the solution impregnation method was adopted to investigate the effect of alkali metals deposition on the SCR catalysts, while various approaches were employed to regenerate the poisoned catalysts. Experimental results indicate that sodium deposition significantly deactivates the catalytic performance of SCR catalysts and sodium hydroxide (NaOH) presents the most serious deactivation. The catalytic ability of sodium poisoned catalyst is only slightly recovered by water washing, whereas it could be improved to approach that of the fresh catalyst by acid solution washing. The regeneration effect of sulfation with SO2 is between those of water washing and acidic solution washing. Further characterizations validated that the deactivation is mainly caused by the damage of surface acid sites. Acidic solution can remove more than 75 wt% of the deposited sodium and provide new acid sites on catalyst surface. Therefore, acidic solution washing is a satisfactory method to regenerate poisoned SCR catalysts for power plants firing high‐sodium coals. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.

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Deactivation and regeneration of a commercial SCR catalyst: Comparison with alkali metals and arsenic

Cited by 188 publications

References 51 publications

Deactivation and Characterization of SCR Catalysts Used in Municipal Waste Incineration Applications

Deactivation and Characterization of SCR Catalysts Used in Municipal Waste Incineration Applications

Poisoning of SCR Catalysts used in Municipal Waste Incineration Applications

Influence of sodium on deactivation and regeneration of SCR catalyst during utilization of Zhundong coals

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