| The production of industrial by-products such as sulfuric acid and ammonium sulfate from sulfur dioxide containing flue gas is an important link in the non-ferrous metal smelting industry to achieve comprehensive recovery of sulfur resources and environmental protection to meet the emission standards,which has great advantages in terms of economic and social benefits.This thesis addresses the problems of incomplete removal of pollutants and poor quality improvement in the existing quality improvement process,and takes the unqualified products of black sulfuric acid and yellow ammonium sulfate from flue gas desulfurization of a non-ferrous smelting enterprise in Yunnan as the research object,and proposes a new technology of ultrasonic synergistic ozone for quality improvement of smelting flue gas desulfurization products,which provides a new idea for quality improvement and efficiency of flue gas desulfurization products.The main research contents of this thesis are as follows:（1）The causes of chromaticity abnormalities of black sulfuric acid and yellow ammonium sulfate were investigated by modern analytical detection methods:it was clarified that the main cause of black industrial sulfuric acid was organic pollutants;it was clarified that the presence of sulfur was the cause of yellow ammonium sulfate,and it was revealed that thiosulfate impurities in the absorbent mother liquor were the main cause of sulfur production under the action of concentrated sulfuric acid.（2）A study on the effect of ultrasonic synergistic ozone on the quality improvement of smelting flue gas desulfurization products was carried out,and it was found that ultrasonic synergistic ozone could efficiently remove organic pollutants in industrial sulfuric acid as well as absorb thiosulfate and subsalt impurities in the mother liquor,and the quality improvement of sulfuric acid and ammonium sulfate products after treatment was remarkable.The experimental results showed that after 2 h of treatment under the conditions of black sulfuric acid treatment volume of 3 L,ultrasonic power density of 200 W·L-1,temperature of 60℃,ozone gas flow rate of 1.8L/h and stirring rate of 800 rpm,the transparency of sulfuric acid products increased from 40 mm to 70 mm,the decolorization rate reached 74.07%,the chromaticity was lighter than the standard chromaticity,the mass fraction of H2SO4was 98.04%,and the product quality met the requirements of the first-class product in GB/T 534-2014 of Industrial Sulfuric Acid.After 2.5 h of treatment under the conditions of 500 m L of absorption mother liquor,400 W·L-1ultrasonic power density,40℃,0.8 L/h ozone gas flow rate and 800 rpm stirring rate,the removal rate of thiosulfate impurities in the absorption mother liquor was 91.39%,and the removal rate of sulfite was 90.83%,and the ammonium sulfate product was white after evaporation and crystallization.The quality of the product met the requirements of the first grade in Compound Fertilizer GB/T 535-2020.（3）By comparing the quality improvement effects of ozone alone,ultrasound alone and ultrasonic co-ozone,the mechanism of ultrasonic co-ozone on the quality improvement of smelting flue gas desulfurization products was revealed by combining EPR analytical test means and experimental results of adding free radical shielding agent.The experimental results show that the introduction of ultrasonic waves can promote the generation of free radicals（·OH,1O2,·O2-）in the reaction system and strengthen the oxidation performance of ozone,thus making the oxidation effect of ultrasonic co-ozone better than that of ozone alone.Compared with the ozone oxidation technology alone,the ultrasonic co-ozone technology can reduce the treatment time by more than 30 min.The effect of ultrasonic co-ozone on sulfuric acid and ammonium sulfate upgrading of desulfurization products mainly relies on the direct oxidation of ozone molecules,while the indirect oxidation of free radicals is less,and the degree of action of each oxidation component is O3>·OH>1O2>·O2-. |
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