A method for preparing modified fly ash by chemical vapor deposition

Abstract

The invention relates to a flue gas demercuration purifying technology of a coal fired power plant, and concretely relates to a method for preparing modified fly ash through chemical vapor deposition. The method is characterized in that hydrogen iodide and air are adopted as raw materials, an improved chemical vapor deposition apparatus is adopted, full contact and a displacement reaction of the raw materials in a gas phase are carried out in a hot fluid jet mode, and a reaction product iodine deposits on the fly ash surface with a lowest temperature in a whole system in a solid phase extremely-fine powder form to complete iodine modification of the fly ash. The modified fly ash can efficiently oxidize non-polar elemental mercury into polar mercury ions in subsequent fire coal flue gas demercuration application, and adsorb the mercury ions to improve the demercuration efficiency. The modified fly has very high demercuration ability, and especially greatly improves the removal efficiency of elemental mercury difficult to remove by common fly ash.

Description

technical field [0001] The invention relates to flue gas mercury removal and purification technology of coal-fired power stations, in particular to a method for preparing modified fly ash by chemical vapor deposition for flue gas mercury removal. Background technique [0002] Mercury is the only heavy metal pollutant that mainly exists in the atmosphere in the gas phase, and has the characteristics of persistence, easy migration, high bioaccumulation and biomagnification. Since mercury stays in the atmosphere for a long time and can circulate with the atmosphere, the problem of atmospheric mercury pollution with coal burning as the main pollution source has gradually attracted people's attention. Coal is currently the main fuel for power stations in China, and the combustion of pulverized coal will bring serious mercury pollution while providing electricity. The existing activated carbon adsorbent and fly ash adsorbent for mercury removal have their own shortcomings. Activ...

AI Technical Summary

Problems solved by technology

[0003] The Chinese patent application publication with publication number CN102120174A introduces a method of impregnating and modifying fly ash by using halogen salt, but this method needs to dry the impregnated fly ash for 12 hours and dry for 24 hours. In the actual application of the factory, higher operating costs and longer operating cycles are required, which is a common problem of the impregnated fly ash modification method

[0004] In addition, more scientific research still uses activated carbon with high operating costs as an adsorbent, but the average mercury content of coal in my country is 0.58 μg / g, far exceeding the international average standard of 0.13 μg / g (Yang Mingzhen, my country’s non-thermal power flue gas Overview of the development of desulfurization industry. China Environmental Protection Industry, 2012.2(164); 14.), if activated carbon is used as an adsorbent, its cost will be several times higher than that of foreign companies, and activated carbon mixed with fly ash will affect the reuse of fly ash , so it is difficult to popularize in domestic coal-fired enterprises

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