球磨时间对机械化学法NaBr改性飞灰脱汞性能的影响

doi:10.16085/j.issn.1000-6613.2020-0241

摘要/Abstract

摘要：

采用全方位行星式球磨机对燃煤飞灰进行机械化学改性。在固定床反应装置上探究了球磨时间对改性飞灰脱汞性能的影响，并对飞灰改性前后的理化特性和脱汞机理进行了分析。结果表明，在单一机械球磨改性条件下，飞灰的脱汞效率随着球磨时间的增加出现先升高后降低的趋势。这是由于球磨过程中飞灰粒径变小，非晶相程度增加，Hg⁰与飞灰样品接触面积增加，有利于Hg⁰的脱除；但过长的球磨时间会造成飞灰孔隙结构的破坏并发生细微颗粒的团聚，使比表面积降低，不利于Hg⁰的脱除。机械球磨条件下添加改性剂NaBr后，飞灰的脱汞效率显著提升，并随着球磨时间的增加而单调增加，这是由于在机械球磨与NaBr的共同作用下，在飞灰表面产生了较多的羰基、羧基/酯基等活性官能团，同时生成C-Br共价基团，促进Hg⁰的吸附脱除。原始飞灰和单一机械化学改性飞灰对Hg⁰的脱除主要以吸附为主，氧化作用占比较少，约为吸附作用的1/3。机械化学NaBr改性飞灰对Hg⁰的吸附能力和氧化能力均显著提升，且吸附作用和氧化作用占比相当。

关键词: 机械化学, 固定床, 制备, 吸附剂, 汞脱除

Abstract:

The coal-fired fly ash was mechanical-chemically modified by omnidirectional planetary ball mill. The effect of ball milling time on mercury removal performance of the modified fly ash was investigated in a fixed-bed reactor, and physicochemical properties and mercury-removal mechanism of fly ash before and after modification were analyzed. The results showed that the mercury removal efficiency of fly ash first increased and then decreased with the increase of ball milling time without the addition of NaBr. It was because the particle size of the fly ash becomed smaller, the degree of amorphous phase increased, and the contact area between Hg⁰ and fly ash rose, which was conducive to remove Hg⁰. Excessive ball milling time caused destruction of the fly ash pore structure and induced agglomeration to reduce the specific surface area, which was not conducive to the removal of Hg⁰. After adding NaBr, the mercury removal efficiency of fly ash was improved significantly, as a result of rising with the longer ball milling time. The reasons were that under the combined action of mechanical ball milling and NaBr, the content of carbonyl and carboxyl/ester groups on the surface of fly ash increased and C-Br covalent groups formed, which promoted the adsorption removal of Hg⁰. The removal characteristics of fly ash on Hg⁰ showed that the removal of Hg⁰ by the raw fly ash and NaBr-free modified fly ash was mainly adsorption, and the oxidation was relatively less, only about 1/3 of the adsorption. The removal of Hg⁰ by adsorption and oxidation was enhanced by both mechanical-chemical action and NaBr modification at the same part.

Key words: mechanical-chemical, fixed-bed, preparation, adsorbents, mercury removal

中图分类号:

X511

胡纪伟, 段钰锋, 耿新泽, 赵炜萌, 熊再立, 张子茜, 梁积鑫, 胡轩宇, 孙冠勋. 球磨时间对机械化学法NaBr改性飞灰脱汞性能的影响[J]. 化工进展, 2020, 39(11): 4717-4725.

Jiwei HU, Yufeng DUAN, Xinze GENG, Weimeng ZHAO, Zaili XIONG, Ziqian ZHANG, Jixin LIANG, Xuanyu HU, Guanxun SUN. Effect of ball milling time on mercury removal by mechanical-chemical NaBr modified fly ash[J]. Chemical Industry and Engineering Progress, 2020, 39(11): 4717-4725.

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