Study On Mercury Emission Reduction And Recovery Technology Of Non-ferrous Metal Smelting Flue Gas

The UN"Convention on Minamata"was been officially approved globally with great effort.Among the major sources of mercury emissions in China,non-ferrous metal smelting has a large proportion.Non-ferrous metal smelting flue gas has the characteristics of high mercury concentration,high concentration of sulfur dioxide and great fluctuation of the production cycle.However,it lacks updated mercury control technology.In order to overcome the difficulties in the existing mercury control technologies,meet the strict mercury emission standard and realize the synergistic absorption of sulfur dioxide,the mercury sulfate system and the iodine system were studied.Based on the hydrogen-sulfur production cycle of sulfur iodine,we studied the elemental mercury absorption effect,and ZnS nanocrystal was synthesized to realize mercury ion selectively adsorption recovery.The main results of this paper are as follows:1.The mercury sulfate system can achieve 96.28%elemental mercury removal efficiency and the absorption process is smoother and more stable than the mercuric chloride system.When the initial mercury concentration was 1.0 mg/m³,the mercury outlet concentration is 0.029 mg/m³.This study found that SO₂ affects the mercury absorption efficiency by reducing Hg²⁺in the system of mercury sulfate and affecting the reaction process of elemental mercury absorption process.2.I₂ is the active component of elemental mercury absorbed by iodine system.Adding KI or HI can promote the dissolution of I₂ and enhance the mercury removal performance of I₂.The initial removal efficiency of I₂+HI system and I₂+KI system are 96.19%and 93.65%.Increasing the concentration of I₂ and KI can improve the removal efficiency;high temperature system,SO₃^2-,H⁺and SO₂ will reduce the absorption of elemental mercury;SO₄^2-and NO₃^-have little effect.3.ZnS nanocrystal is favorable for metal adsorption,and the removal efficiencies of single component of Hg²⁺,Cu²⁺,Pb²⁺and Cd²⁺are 99.9%,99.9%,90.8%and 66.3%,respectively.The adsorption is in accordance with Langmuir adsorption isotherm and pseudo-first order kinetics model.What’s more,Hg²⁺separation coefficients of Cu²⁺,Pb²⁺and Cd²⁺were1329.2,45464.0 and 210910.9,respectively.When the amount of Hg²⁺in the waste acid was sufficient,the final reaction product was HgS due to the smallest K_spp value,and it can achieve Hg²⁺selective removal.