当前位置: X-MOL 学术Fuel › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Catalytic oxidation of NH3 over circulating ash in the selective non-catalytic reduction process during circulating fluidized bed combustion
Fuel ( IF 7.4 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.fuel.2020.117546
Ming-xin Xu , Ya-chang Wu , Hai-bo Wu , Hao-dong Ouyang , Qiang Lu

Abstract Selective non-catalytic reduction (SNCR) with NH3 as the reducing agent is widely used for the denitrification of flue gas in circulating fluidized bed combustion (CFB) process, where the circulating ash can cause the oxidation of NH3. In this study, the behaviors and mechanisms of NH3 catalytic oxidation over circulating ash were systematically investigated. The results revealed that NH3 could be catalytically oxidized to form NO efficiently by circulating ash. Along with the temperature increasing from 550 °C to 950 °C, the formation of NO increased at first and then decreased. Oxygen was crucial to NH3 catalytic oxidation, while its effects on NO formation were slight at high concentrations. Meanwhile, as the initial NH3 concentration increased, the concentration of NO in the flue gas increased while the selectivity of NO decreased because of the enhanced homogeneous reduction between the residual NH3 and NO. Fe2O3 was confirmed to be one of the principal mineral components in circulating ash to catalyze NH3 oxidation. In addition, the mechanisms of NH3 oxidation over circulating ash were also investigated. It was validated that NH2 on Lewis acid sites were the main NH3 adsorbed species (ad-species), and the main oxidation intermediates of NH3 ad-species were bidentate and bridged nitrates in the presence of O2.

中文翻译:

循环流化床燃烧选择性非催化还原过程中循环灰催化氧化NH3

摘要 以NH3为还原剂的选择性非催化还原(SNCR)广泛用于循环流化床燃烧(CFB)工艺中的烟气脱硝,其中循环灰分会引起NH3的氧化。本研究系统地研究了NH3催化氧化在循环灰上的行为和机理。结果表明,通过循环灰分,NH3可以被催化氧化成NO。随着温度从550℃升高到950℃,NO的生成量先增加后减少。氧气对 NH3 催化氧化至关重要,而在高浓度下其对 NO 形成的影响很小。同时,随着初始 NH3 浓度的增加,由于残留的 NH3 和 NO 之间的均匀还原增强,烟气中 NO 的浓度增加,而 NO 的选择性降低。Fe2O3 被证实是循环灰分中催化 NH3 氧化的主要矿物成分之一。此外,还研究了NH3在循环灰上氧化的机制。经验证,路易斯酸位点上的 NH2 是主要的 NH3 吸附物种(ad-species),在 O2 存在下,NH3 ad-species 的主要氧化中间体是双齿和桥连硝酸盐。
更新日期:2020-07-01
down
wechat
bug