Removal Of SO₂ From The Calcined Flue Gas Of Petroleum Coke With Red Mud Enhanced By Additives

Petroleum coke is an important industrial intermediate material,which is produced when the delayed coking process produces light oil.It can be used in metallurgical,chemical industry as electrode or raw material to produce chemical products.When petroleum coke is used in the production of steel-making graphite electrode and aluminum anode,it needs a calcination process to meet the production requirements.The calcination process can remove volatiles,moisture and part of sulfur in petroleum coke,increase density and strength,improve electrical conductivity and oxidation resistance.During the calcination process,part of the sulfur in the petroleum coke is discharged,resulting in a large amount of SO₂in the calcination flue gas,whose concentration is 1000?5300 mg/m³.However,the national emission standard is becoming stricter,and the calcination flue gas needs to be efficiently desulfurized to be discharged.Red mud is an alkaline solid waste from alumina plants.At present,its main disposal method is stockpiling,which brings serious environmental problems.Studies have shown that red mud has a small particle size and high alkalinity,and can be used for flue gas desulfurization.In this paper,based on the current situation of SO₂pollution from the petroleum coke calcination flue gas and the large amount of red mud discharged from the alumina plant,the removal of SO₂from the flue gas of petroleum coke calcination by using red mud is studied.First of all,the pilot test of red mud flue gas desulfurization was carried out to investigate the effect of red mud desulfurization after scale-up.At the same time,the bubble reactor was used to study the additives to enhance the desulfurization of red mud,and the mechanism of desulfurization enhancement was discussed to achieve using waste to treat waste,energy saving and emission reduction.The pilot test of red mud desulfurization shows that red mud has a good effect of removing SO₂.When the desulfurization slurry is weakly acidic,it can maintain a good desulfurization efficiency.Its desulfurization efficiency is over 80%.In addition,iron is dissolved in the desulfurization process.Adipic acid,oxalic acid and citric acid as organic additives for red mud desulfurization,three kinds of organic acids have strengthening effect on red mud flue gas desulfurization,but the overall effect is not obvious and unstable.Sodium citrate was selected to enhance the red mud desulfurization,which showed that it has a good effect,and the optimum reaction conditions are as follows:addition amount of sodium citrate is 10 mmol/L,reaction temperature is 25?,and slurry concentration is15%.KI?Mn O₂?Mg SO₄?Fe(NO₃)₃were used as inorganic additives in red mud slurry.The four kinds of inorganic additives have a strengthening effect on SO₂removal,in which Mn O₂has the best effect,followed by KI,and Mg SO₄and Fe(NO₃)₃have less strengthening effect.The optimum reaction conditions of red mud desulfurization enhanced by Mn O₂are as follows:addition amount of Mn O₂is 15 mmol/L,reaction temperature is 60?,flue gas SO₂concentration is 1000 mg/m³,oxygen content in flue gas is 20%.The characterization results show that the main minerals in red mud are hematite,cancrinite,hydrogrossular and other mineral components,the main minerals of the desulfurization residue after desulfurization are hematite and dihydrate gypsum,cancrinite and hydrogrossular dissolve and participate in the desulfurization reaction.Dihydrate gypsum is the product of SO₂in flue gas and Ca²⁺in red mud.The addition of Mn O₂to the red mud slurry promotes the red mud mineral dissolution and absorption of SO₂.The desulfuration curves show that the SO₂concentration at the outlet of red mud desulfuration and Mn O₂enhanced red mud desulfuration both show a trend of first rising,then falling,and finally rising with the increase of desulfurization time.In the early stage of desulfurization,Mn O₂has a good strengthening effect on red mud desulfurization,but there is no strengthening effect in the later stage.The p H value of the two slurries decrease with the increase of desulfurization time,but the p H value of the Mn O₂enhanced red mud desulfurization slurry is lower than the p H value of the red mud desulfurization slurry after a period of time,and continue until the end of the desulfurization.The saturated sulfur capacity of red mud desulfurization is1119.8mg/g,the saturated sulfur capacity of Mn O₂enhanced red mud desulfurization is 1214.1mg/g,and the saturated sulfur capacity is increased by 8.4%.The mechanism of Mn O₂enhanced red mud desulfurization is the redox reaction between Mn O₂and SO₂,and the liquid phase catalytic oxidation of SO₂by manganese ions and iron manganese ions,Thus,the desulfurization efficiency of red mud slurry is improved.