In situ regeneration of commercial NH3-SCR catalysts with high-temperature water vapor

Shi, Yao; Zhang, Pei; Fang, Tuo-tuo; Gao, Erhao; Xi, Fujuan; Shou, Tianyu; Tao, Mengna; Wu, Shi; Bernards, Matthew T.; He, Yi; Pan, Hua

doi:10.1016/j.catcom.2018.08.009

Cited by 30 publications

(7 citation statements)

References 30 publications

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“…This indicates that there is almost no sulfate on the fresh catalyst surface, while the sulfate content on the deactivated catalyst surface increases significantly after a period of field operation. 19 The dry ice blasting regeneration has a certain removal effect on sulfate. This is consistent with the results in Figure 7e.…”

Section: Xrdmentioning

confidence: 99%

“…Compared to the off-line regeneration technology, the studies on the online regeneration methods of the deactivated commercial SCR catalyst are few. Shi et al 19 found that water vapor on-line regeneration at 300−350 °C for 336 h could effectively remove the potassium, arsenic, and sulfate deposits on the catalyst surface and increase the surface active oxygen and specific surface area of the commercial deactivated SCR catalyst (V 2 O 5 −WO 3 /TiO 2 ) used in the coal-fired power plant. The deNOx efficiency of the regenerated SCR catalyst could reach 91.4%.…”

Section: Introductionmentioning

confidence: 99%

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DeNOx Characteristics of Commercial SCR Catalyst Regenerated On-Line by Dry Ice Blasting in a Coal-Fired Power Plant

Xie

Peng

Zhao

et al. 2022

Ind. Eng. Chem. Res.

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The emissions of nitrogen oxides (NOx) from coal-fired power plants have attracted worldwide attention. Under the harsh working environments, a large number of selective catalytic reduction (SCR) catalysts will face deactivation and replacement. The current mainstream regeneration technologies (including solution regeneration and thermal regeneration) have complicated procedures and long regeneration times, which limit their wide application. In this work, the dry ice blasting on-line regeneration technology was adopted to treat a commercial V2O5–WO3/TiO2 SCR catalyst used for 5 years (defined as D-SCR) in a 660 MW coal-fired power plant. The effects of temperature and SO2 concentration on the deNOx performance of the fresh, deactivated, and regenerated catalysts (denoted as F-SCR, D-SCR, and R-SCR) were evaluated in laboratory-scale experiments. BET, SEM, XRF, XRD, XPS, NH3-TPD, and FTIR analyses were used to characterize the physicochemical properties of some typical samples. The results show that instantaneous NOx conversion efficiency of the three catalysts is greater than 90% with the optimum deNOx temperature of 320 °C. The deposition or chemical reaction of fly ash, alkali metals, SO2, and so on in the flue gas on catalyst surface will result in deterioration of pore structure, loss of active components V2O5 and MoO3, and the increasing contents of sulfate, SiO2, Al2O3, As2O3, and other compounds on catalyst surface, which leads to deactivation of the catalyst. The dry ice blasting on-line regeneration technology can improve pore structure, remove sulfate, and increase the number of surface Lewis and Brønsted acid sites, in turn improving the deNOx activity of catalyst. The inhibitory effect of the deposited sulfate on the catalytic activity is stronger than the promotion effect of the acid site generation with the existence of SO2. Thus, increasing the SO2 concentration reduces the deNOx activity of the catalyst. The dry ice blasting on-line regeneration technology is a good commercial SCR catalyst regeneration technology and has broad engineering application prospects.

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Section: Xrdmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

DeNOx Characteristics of Commercial SCR Catalyst Regenerated On-Line by Dry Ice Blasting in a Coal-Fired Power Plant

Xie

Peng

Zhao

et al. 2022

Ind. Eng. Chem. Res.

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“…Catalyst composition and structure design are optimized to guarantee high DeNO x and Hg-oxidation activity, low SO 2 oxidation activity, and high mechanical resistance in harsh high-dust operation. However, during time on stream, monoliths and plates are subject to structural, morphological, and chemical transformations caused by interaction with the flue gases (typically contaminated by particulate matter, fly ash, organic and inorganic pollutants); , the catalytic activity and the reactor performance decline, and after 2–4 years, the replacement of deactivated catalyst and/or fresh catalyst addition becomes necessary. This has a tremendous economic impact, considering the huge catalyst inventory of SCR reactors (about 1 m 3 catalyst per MW of generated power). − Comprehension of the mechanism and kinetics of catalyst deactivation is thus an important field of investigation in the area of applied catalysis, with potential implications on the optimization of the replacement strategies, the identification of rejuvenation procedures, and the development of improved formulations and geometries.…”

Section: Introductionmentioning

confidence: 99%

Kinetic and Mass Transfer Effects of Fly Ash Deposition on the Performance of SCR Monoliths: A Study in Microslab Reactor

Lanza

Usberti

Forzatti

et al. 2021

Ind. Eng. Chem. Res.

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Selective Catalytic Reduction (SCR) reactors with ternary vanadium-based catalysts are the state-of-the-art technology for the multipollutant abatement in cofired biomass and coal power plants. During time of stream, the catalyst performance declines due to the deposition of fly ashes and inorganics from the flue gas. Understanding the phenomena behind the deactivation is a key factor to identify optimal strategies for catalyst replacement or rejuvenation. In this work, samples of spent commercial monoliths, unloaded from a full scale SCR reactor after 1500 h (Sample A = start of run) and 35 000 h (Sample B = end of run), were examined and compared with the fresh monolith. SEM-EDX measurements across the walls of the aged monoliths showed radial concentration profiles of inorganic elements and, in the case of Sample B, also the growth of a layer of ashes. NH3-SCR tests over the powdered catalysts gave nonconclusive evidence of deactivation, likely due to the averaging effect of grinding; instead, by testing slabs cut from the monoliths, the integrity of the honeycomb wall was preserved, and effects of aging were observed. The design of the microslab reactor is optimized to capture the process from the chemical regime (below 200 °C) to the intraporous-mass transfer controlled regime (>250 °C); in fact, the impact of gas–solid mass transfer is negligible, due to a high Sherwood number (close to 5) and a small hydraulic diameter (3 mm). The evidence of a full external diffusion regime over the long-term aged catalyst was thus easily associated with the presence of the dense layer of ash deposit that behaved as a diffusion barrier; a modeling analysis was performed and allowed to quantify the mass transfer resistance of the deposit and estimate that the intrinsic activity of the two aged samples was comparable. Indeed, by scratching the surface layer of the microslab from Sample B, a remarkable recovery of the DeNO x performance was obtained, matching the activity of the slab from Sample A. The deposition of fly ashes over the honeycomb walls was thus recognized as the major cause of performance loss, via a gas-phase mass transfer resistance.

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“…Diesel particulate filter (DPF) to reduce soot emissions together with Urea-SCR to reduce NOx. The Urea-SCR systems have been shown to be both very efficient and durable in vehicle applications, so the heavy-duty diesel engines manufacturers prefer Urea-SCR for reducing NOx [4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Influence of Steam and Sulfide on High Temperature Selective Catalytic Reduction

Zhang¹,

Wang²,

Zhang³

et al. 2020

Fluid Dynamics &Amp; Materials Processing

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The influences of steam and sulfide on the efficiency of NOx reduction using ammonia (NH 3 ) over the nanometer-class V-W/Ti catalyst in conditions of high temperature is experimentally investigated using a steady-flow reactor. The results showed that selective catalytic reduction (SCR) is inhibited by H 2 O at low temperature, but higher NO conversion efficiency is achieved at high temperature since the reaction of NH 3 oxidized by O 2 to NOx is inhibited by H 2 O. The activity of SCR is promoted by SO 2 in the temperature range of 200~500°C , the NO conversion efficiency was improved to 98% from 94% by adding SO 2 . SCR would be improved at 350~500°C when H 2 O and SO 2 exist at the same time. Furthermore, the positive influence to the NOx conversion was proved in the presence of H 2 O and SO 2 as a result of the European Stationary Cycle test.

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In situ regeneration of commercial NH3-SCR catalysts with high-temperature water vapor

Cited by 30 publications

References 30 publications

DeNOx Characteristics of Commercial SCR Catalyst Regenerated On-Line by Dry Ice Blasting in a Coal-Fired Power Plant

DeNOx Characteristics of Commercial SCR Catalyst Regenerated On-Line by Dry Ice Blasting in a Coal-Fired Power Plant

Kinetic and Mass Transfer Effects of Fly Ash Deposition on the Performance of SCR Monoliths: A Study in Microslab Reactor

Influence of Steam and Sulfide on High Temperature Selective Catalytic Reduction

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