Study On Simultaneous Absorption Of Hg⁰-SO₂ From Non-Ferrous Metal Smelting Flue Gas Based On Iodine Cyle

Mercury is one of the main pollutants in industry.Mercury emissions in China come from coal-fire flue gas as well as non-ferrous metal smelting flue gas.The“Minamata Mercury Convention”,which is signed by all members of UN in year 2013,was approved by The National People's Congress of China in year 2016.China suffers from mercury pollution more seriously than any other countries and we are facing huge obstacles to meet the criteria of mercury emissions.The smelting flue gas of non-ferrous metal contains high amount of Hg⁰ as well as SO₂,and the SO₂ will react with Hg²⁺in the solution thus reducing the removal efficiency.In order to optimize the current mercury removal technique,the iodine solution was introduced in this study.It provides novel ways to remove and recycle mercury from the non-ferrous smelting flue gas while removing SO₂ at the same time.Through grounded researches and experiments,a few conclusions have been made:?1?SO₂ could be removed efficiently in I₂/HI absorption system.The SO₂removal efficiency of I₂/HI absorption system is over 98.8%and close to that of the traditional limestone FGD process or sodium alkali scrubbing process.There is no obvious effect on SO₂ by the main coal-fired flue gas components.The main FGD byproducts are H₂SO₄ and HI,which could be separated by distillation.The energy needed in distillation could be provided by the waste heat from the coal combustion,which will save the running cost greatly.?2?I₂ can effectively absorb Hg⁰ in the flue gas,and the Hg⁰ absorption efficiency is 99%.A certain amount of I^-concentration is favorable for the absorption of Hg⁰ while an excessive I^-concentration is disadvantageous.SO₂ has negligible effect on Hg⁰ absorption and it will not influence the Hg²⁺absorbed by solution.Hence,using I₂/KI solution to absorb Hg⁰ has a promising prospective.?3?The co-absorption of SO₂ and Hg⁰ in the HI/I₂/H₂O solution takes place at the same time.The absorption performance of the two gases restricts each other.The increase of I₂ concentration or Hg⁰ concentration,the decrease of SO₂ concentration are all beneficial to the Hg⁰ absorption.?4?The products of the reaction are of great value.The whole technique is more efficient and less toxic than the existing techniques.The technique can achieve recycling through different forms of product separation.The whole system managed to achieve the simultaneous absorption of SO₂ based on the absorption of Hg⁰.The study provides new ideas for the FGD method in coal-fire industry and SO₂-Hg⁰ removal method in non-ferrous metal smelting industry.