Method for enriching zinc oxide concentrate by wet treatment of zinc-containing dust in iron and steel plant

Abstract

The invention relates to the field of comprehensive utilization of steel plant solid waste resources, particularly a method for treating steel plant zinciferous smoke dust by a wet process. The method comprises the following steps: a compounding agent water solution using aminoacetate ions as a ligand is utilized to leach steel plant zinciferous smoke dust under weakly alkaline conditions, wherein in the leaching process, iron, carbon, calcium, magnesium and silicon are insoluble and reside in leaching slag, lead and cadmium in the smoke dust enter the leach solution along with the zinc, and the leaching slag is subjected to water washing and returns to an iron and steel system to perform proportioning and sintering; the obtained leach solution is subjected to alkali regulation and zinc precipitation by using CaO or Ca(OH)2, so that the zinc precipitates in the form of zinc oxide, and the lead and cadmium coprecipitate along with the zinc and are enriched in the zinc oxide concentrate; and the zinc precipitation solution is subjected to acid regulation and calcium precipitation by using CO2 gas so as to remove calcium ions introduced in the zinc precipitation process and regenerate the compounding agent, and the regenerated compounding agent solution can return to the leaching process for direct use, wherein an active CaCO3 byproduct can be produced in the calcium precipitation process.

Description

technical field [0001] The invention relates to the field of comprehensive utilization of solid waste resources in iron and steel plants, in particular to a method for wet treatment of zinc-containing smoke and dust in iron and steel plants. Background technique [0002] China's iron and steel industry has a huge production capacity. According to the data from the National Bureau of Statistics, the annual output of crude steel in China in 2014 was 823 million tons, which means that the zinc-containing fume produced in 2014 was at least 8.23 ​​million tons; due to the different raw materials processed, the soot There is also a large difference in the zinc content in the medium. Generally, the zinc content of the dust that has not been enriched by circulation is less than 10%, and some are even lower than 2%, while the dust that has been enriched for many times contains more than 15%. Calculated at 1% zinc grade, in 2014 alone, 82,300 tons of zinc were dispersed in the zinc-co...

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Problems solved by technology

[0004] Acid leaching: leaching zinc-containing fumes from iron and steel plants in an acidic system. The leaching agent is mainly sulfuric acid. Zinc fume will inevitably have a complex process of iron precipitation from the leach solution, so it is not suitable for the treatment of zinc fume with high iron content; in addition, in order to dissolve zinc ferrite in the fume, the acid leaching process often requires enhanced leaching (high temperature , high acid leaching), so the anti-corrosion requirements for equipment are relatively high (see Chinese patent document CN103911518A)

[0005] Ammonia leaching: in alkaline system (103 with Zn 2+ The complex ions are formed to dissolve ZnO in the dust into the solution. During the process, calcium, magnesium, iron, and silicon will not be dissolved in large quantities, and the reagent consumption is small. It has the characteristics of selective zinc leaching; , greater environmental hazards; in addition, the ligand NH used in the ammonia leaching process 3 to Zn 2+ The coordination ability is weak, and the zinc ferrite (ZnFe 2 o 4 ) is insufficient in dissolving capacity, and does not have the ability to remove zinc in iron and steel plant zinc-containing fume, and it is difficult to achieve deep separation of iron and zinc (see Tong Zhifang et al. Ammonia leaching of zinc-containing fume to prepare active zinc oxide[J]. Chemical Industry Environmental Protection, 2009,29(6):534-537)

[0006] Alkali leaching: in a strong alkaline system (pH > 14) to leaching zinc-containing fumes from iron and steel plants, the leaching agent is sodium hydroxide (NaOH), and the ligand OH is used to - with Zn 2+ The formation of complex ions makes ZnO in the dust dissolve into the solution, and the iron is insoluble during the process, which also has the characteristics of selective zinc immersion; however, the operating conditions of the alkali leaching process are strong alkaline systems, which require high anti-corrosion equipment; in addition, the alkaline leaching process uses Ligand OH - to Zn 2+ The ability to cooperate is weak, the ability to dissolve zinc ferrite in smoke is insufficient, and it is also difficult to achieve deep separation of iron and zinc (see Chinese patent document CN200910119189)

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