Study On Chlorine-mediated Electrochemical Treatment Of Sintering Desulphurization Wastewater

The iron and steel industry will produce a large amount of desulfurization wastewater during the process of using wet desulfurization process to treat sintering flue gas.The wastewater has a complex composition and contains a large amount of suspended matter,refractory organic matter,ammonia nitrogen,nitrite,nitrate,sulfite,heavy metals,chloride ions,and fluoride ion,etc.,the treatment is difficult.The existing sintered flue gas desulfurization wastewater treatment system of a large steel plant in Guangdong is mainly for the treatment of heavy metals thallium,lead,cadmium,etc.,and the treatment effect of ammonia nitrogen and COD in wastewater is limited,which affects the company's total effluent water quality to a certain extent.And the quality of reclaimed water is urgently in need of improvement.In the investigation and analysis of this paper,it is found that the choice of chlorine dielectric chemical method for the treatment of the actual wastewater of the plant's sintering flue gas desulfurization has obvious advantages.Specifically,the influencing factors of the method for the treatment of desulfurization wastewater,the removal mechanism of pollutants,and the process feasibility demonstration were systematically carried out study,get the following conclusions:?1?Using Ti/RuO₂-IrO₂ as the anode and graphite as the cathode,the effects of current density,chloride ion concentration,plate spacing,and aeration on the removal efficiency of COD and ammonia nitrogen in desulfurization wastewater were investigated.Through single factor experiments,the most ideal treatment conditions are:the distance between the plates is 2 cm,the current density is 30 m A/cm²,and the chloride ion concentration is 2.4 g/L.After 60 minutes of electrolysis time under this condition,the removal rates of ammonia nitrogen and COD in the desulfurization wastewater reached 91.9%and 89.6%,respectively.Through aeration experiment research,it was found that during the electrochemical oxidation process dominated by chloride ions,aeration will destroy the migration process of chloride ions in the wastewater to the anode,and destroy the concentration polarization interface layer of active chlorine near the anode,reducing the oxidation efficiency of ammonia nitrogen.?2?The response surface?RSM?experiment is used to optimize the design of the parameters of the chlorine-dielectric conductive chemical treatment of desulfurization wastewater.The set variables are current density,chloride ion concentration,and electrolysis time,and the response value is the ammonia nitrogen removal rate.The best operating conditions are as follows:electrolysis time is 50 min,current density is 40m A/cm²,chloride ion concentration is 3 mg/L,and the corresponding ammonia nitrogen removal rate is 95.56%.Three verification experiments were conducted according to the conditions,and the results showed that the removal rates of ammonia nitrogen were 96.23%,94.38%,and 97.46%,which were close to the predicted values of the model.This also shows that the response surface experiment is reliable for the simulation process of chlorine-mediated treatment of sintered flue gas desulfurization wastewater.?3?Through mechanism research,it was found that in the process of desulfurization wastewater treatment by chlorine-conducting chemical method,the contribution rate of ammonia nitrogen by the direct oxidation of the electrode surface and the hydroxyl radical-mediated oxidation is very low,which mainly depends on the indirect oxidation of active chlorine.The removal of COD is a combination of direct and indirect oxidation.Chlorine dielectric chemical method also has a good removal effect on nitrate and nitrite in desulfurization wastewater,the removal rate is 85.6%and100%,which mainly depends on the coupling effect of cathode reduction and indirect oxidation.?4?It can be obtained through enlarged experimental research that the chlorine dielectric conductivity chemical method can effectively and stably remove ammonia nitrogen and COD in sintering flue gas desulfurization wastewater,and the removal rates are 98.6%and 87.8%.Compared with other treatment methods,this method has simple operation,stable removal effect and almost no sludge.