富氧气氛下改性生物质焦脱汞的氧化机理

doi:10.16085/j.issn.1000-6613.2020-0790

摘要/Abstract

摘要：

富氧燃烧作为新型燃烧方式可以有效减少CO₂排放，提高燃烧效率，与传统燃烧方式相比，烟气组分也产生较大的变化。玉米秸秆焦可以作为吸附剂在燃烧后阶段对汞进行脱除。本文采用1% NH₄Cl溶液浸渍的玉米秸秆焦为吸附剂，在富氧气氛下探究NO及O₂对汞氧化脱除机理。文中指出玉米秸秆焦经浸渍改性处理后，其表面孔隙结构更加丰富，比表面积以及总孔容积增大。同时，改性后表面官能团的数量大大增加，尤其是含氧的官能团，对汞的吸附起着重要作用。富氧气氛下NO与生物质焦表面的O₂和含氧基团反应生成具有氧化作用的NO₂，与零价汞反应促进汞的去除。NO和O₂共存时对零价汞的氧化有更明显的促进作用。O₂含量的增加也会促进生物质焦对汞的吸附，这主要是由于O₂的强氧化作用导致，与零价汞发生非均相氧化反应生成HgO。此外，含氧官能团化学键的断裂也为汞的氧化提供了氧自由基团。

关键词: 汞, 富氧燃烧, 生物质, 改性, 吸附, 氧化

Abstract:

Corn straw char impregnated with 1% NH₄Cl solution was used as adsorbent to explore the mechanism of NO and O₂ oxidation on removal of mercury in oxygen enriched atmosphere. Compared with the traditional combustion mode, the composition of oxy-fuel flue gas also changed greatly. In this experiment, corn straw char impregnated with 1% NH₄Cl solution was used as adsorbent to explore the mechanism of oxidation with NO and O₂ on removal of mercury in oxy-fuel combustion atmosphere. The results showed that the surface pore structure of corn straw char was enriched after impregnation, with more mesoporous structure and increased total pore volume. At the same time, the results of Fourier transform infrared spectrometer showed that the number of functional groups on the surface was greatly increased, especially the oxygen-containing functional groups, which played an important role in the adsorption of mercury. NO could react with O₂ and oxygen-containing groups on the surface of biomass char to form NO₂ with oxidation effect, which reacted with zero valent mercury to promote the removal of mercury. The co-existence of NO and O₂ had more obvious effect on the oxidation of zero valent mercury. The increase of O₂ content could also promote the adsorption of mercury on biomass char, which was mainly due to the strong oxidation of O₂, i.e., O₂ made heterogeneous oxidation with zero valent mercury. In addition, the breaking of chemical bond of oxygen-containing functional group could also provide support for the oxidation of mercury.

Key words: mercury, oxy-fuel, biomass, modification, adsorption, oxidation

中图分类号:

X511

沈昊天, 王卉, 沈畅, 吴建飞. 富氧气氛下改性生物质焦脱汞的氧化机理[J]. 化工进展, 2020, 39(11): 4734-4741.

Haotian SHEN, Hui WANG, Chang SHEN, Jianfei WU. Oxidation mechanism of mercury removal by modified biomass char under oxy-fuel condition[J]. Chemical Industry and Engineering Progress, 2020, 39(11): 4734-4741.

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