Experimental Study On Removal Of Chloride Ion In Desulfurization Wastewater By Extraction

The desulfurization wastewater of coal-fired power plants contains a large amount of soluble ions.When the content of chlorine ions is too high,the waste water will corrode the equipment of the desulfurization system,so that the desulfurization wastewater can not be reused in the desulfurization system,nor in the natural system emission.Therefore,it is necessary to remove chloride ions from the wastewater.At present,the removal method of chloride ions from the desulfurization wastewater is carried out by evaporation,electrolysis-electrodialysis,ion exchange,membrane exchange and so on.In this paper,addresses the problem of excessive chloride ion content in desulfurization wastewater.the extraction method was used to study the removal of chloride ions in desulfurization wastewater.The paper uses calcium chloride solution to simulate the desulfurization wastewater of power plant,and explores the optimal conditions for the extraction of chloride ion.The experiment shows that when N235 is used as the extractant and n-octanol is used as the diluent,the dilution ratio is 1:1,The ratio of organic phase to aqueous phase is 3:1,the volume ratio of aqueous phase to CO₂ per minute is 1:1.2,and the extraction reaction time is40 min.The extractant has the best extraction effect on chloride ion.When the chloride ion concentration is 20000 mg/L,the extraction efficiency can reach 80%or more.Under the condition of increasing pressure,the extraction efficiency of chloride ions is further increased.The calcium carbonate produced by the extraction belongs to the nanometer calcium carbonate after the particle size detection,and has high industrial value.In the experiment,an innovative method of continuously dissolving NH₃ in the stripping solution（ammonia water）in the stripping process is used,so that the stripping solution can be recycled for the regeneration of the organic phase.It not only solves the problem of wastewater generated by the stripping process,but also precipitates NH₄Cl crystals of industrial value during the recycling of the stripping solution,Thereby reducing the cost of wastewater treatment.In the stripping process,there is a problem that the organic phase and the stripping solution are not completely separated.After the experiment,it is finally determined that the stripping solution remaining in the organic phase is removed by electrostatic separation or centrifugation.In order to verify the feasibility of extraction method for chloride ion extraction of actual power plant desulfurization wastewater,the desulfurization wastewater of actual Power Plant was studied experimentally.The research shows that chloride ion extraction is carried out under the interference of impurity ions(Na⁺,Mg²⁺,SO₄^2-)in water.The efficiency is greatly reduced compared to the same concentration of calcium chloride solution.After adding an appropriate amount of lime to the wastewater,the Mg²⁺and SO₄^2-in the wastewater can be substantially completely removed,and the chlorine ion removal efficiency of the desulfurization wastewater is greatly improved.Experiments show that when the solution water contains only three ions of Na⁺,Ca²⁺,and Cl^-and the concentration of Cl^-is constant,the higher the Na⁺content,the lower the removal efficiency of Cl^-.Therefore,the large amount of Na⁺in the desulfurization wastewater seriously affects the extraction efficiency of chloride ions in the wastewater.The removal of Na⁺is difficult.After the comparison of the sodium ion removal method,the electrolysis-electrodialysis method is finally selected to remove the sodium ions in the desulfurization wastewater.