Study On Absorption Characteristics Of As₂O₃ In Flue Gas By Ammonia Method In Spray-and-bubble Column

In addition to SO₂,NO_X,PM,etc.,coal-fired power plants emit a large amount of trace elements to cause great pollution to the environment.Among them,As is one of the most common and harmful elements of carcinogenicity.At present,the environmental protection departments at home and abroad have gradually taken into account the emission control of flue gas arsenic.China has also proposed to support the coordinated removal of pollutants including flue gas arsenic.There are many methods for controlling arsenic in coal combustion,and the control of arsenic in flue gas from coal-fired power stations is relatively weak.The use of existing pollutant control units to control flue gas arsenic is a technical route that can achieve coordinated control of pollutants and save investment costs.Spray-and-bubble technology is a new type of desulfurization technology.In this paper,the gas phase As₂O₃ generating device is added on the basis of the spray-and-bubble column.Taking air and SO₂ as the simulated flue gas,The influence of key operating parameters such as ammonia water concentration,SO₂ mass concentration,liquid-gas ratio and bubbling pipe depth on the absorption efficiency of ammonia water vapor phase As₂O₃was investigated by the control variable method.The results show that the concentration of ammonia water increases,the efficiency of arsenic removal and the total amount of arsenic removal increase first and then decrease,and the efficiency at 0.07%mass concentration can be stabilized at about 82%.The introduction of SO₂ can promote the absorption of gas phase As₂O₃ by ammonia.The promotion effect is firstly increased and then decreased with the increase of SO₂ mass concentration.When the concentration of SO₂ in the flue gas is 1500ppm,the efficiency reaches the maximum value.With the increase of liquid-gas ratio,the absorption efficiency of As₂O₃ by ammonia water and total arsenic removal The amount first increases and then stabilizes;bubbling pipe depth is negatively correlated with the arsenic removal efficiency of ammonia.Considering the energy consumption of the experimental system and equipment maintenance,10L/m³ and5cm were taken as the best liquid-gas ratio and bubbling pipe depth respectively in this experiment.Due to the actual engineering application,the flue gas contains not only SO₂ but also NO_X.Although the efficiency of independent desulfurization and denitrification is very high,the combined desulfurization and denitrification technology has become a hot spot at home and abroad due to its own shortcomings.In this paper,O₃,NO,air and SO₂ will be used as simulated flue gas.Based on the ozone pre-oxidation method,combined with the new spray-and-bubble technology,simultaneous desulfurization and denitrification can simultaneously remove As₂O₃ from flue gas,and explore the key operating parameters such as the O₃/NO molar ratio and ammonia water mass concentration,SO₂ inlet mass concentration,liquid-gas ratio,and bubbling pipe depth have an effect on the removal of As₂O₃ from ammonia.The results show that the efficiency of ammonia absorption of As₂O₃and the total amount of arsenic removal in the flue gas under the spray bubbling technology increase sharply and the subsequent increase decreases with the increase of the O₃/NO molar ratio.The average efficiency of ammonia absorption of As₂O₃ and the total amount of arsenic removal first increases and then decreases with the increase of the concentration of ammonia water,when the mass concentration of ammonia water is 0.05%,the arsenic removal efficiency reaches the maximum value of 70.8%;The introduction of SO₂ can promote the absorption of As₂O₃ by ammonia water;the liquid-gas ratio increases,The efficiency of ammonia absorption of As₂O₃ and the total amount of arsenic removal increased first and then gradually became flat;The greater bubbling pipe depth,the lower efficiency of the absorption of As₂O₃ by ammonia water,the efficiency is 70.8%when the depth of the immersion is 5cm,and the efficiency is reduced to 32.6%when the immersion depth is increased to 14cm.