Study On The Wet Removal Of SO₂and NO In Coal Combustion Flue Gas

SO2and NOx emission of Chine of2012reached2117.6t and2337.8t respectively, of which coal combustion contributed about90%and70%respectively. As a result, the sulfuric-nitric hybrid acid rain pollution caused a huge economic loss of100billion yuan, the total economic loss caused by atmospheric pollution makes3%of GDP. Main flue gas desulfurization technology including calcium method, magnesia method, sodium method and ammonia method, cost resources like limestones, MgO, Na2CO3or liquid ammonia, while denitrification technologies like SCR, SNCR, Irradiation of Electron Beam and active carbon adsorption are all ran under high cost and huge investment, also cause secondary pollutions. In this paper, carbide slag, as a waste of resin industry, was used as a desulfurizer, to solve the waste treatment of carbide slag and desulfurization of flue gas, and use Co2+as the central ion, ethylenediamine as ligand to form complex to adsorb NO out of flue gas.The adsorption of SO2by carbide slag was studied in spray tower under different conditions including adding citric acid, change the concentration of carbide slug, change the concentration of flue gas SO2, L/G, different carbide slag particulate diameter and reaction temperature, and furtherly studied the modification of carbide slug from the mass transfer and reaction process, reaction mechanism and apparemt kinetics. Meanwhile, the adsorption of NO by the complexing liquor of triethylenediamine cobalt (ii) under saturated sodium nitrate system and no sodium nitrate system was studied in the spray bubbling tower.Results showed that, high concentration of carbide slag in slurry, large L/G, high pH value and lower the inlet SO2concentration are positive for SO2removing, the effection of main operation factors to desulfurization was slurry pH> carbide concentration、absorption temperature. The innate character of desulfurization was the hydration of SO2forming H+and HSO3-stable products, there are3mass transfer reaction sections, in the liquid phase, H+and HSO3-transforms to CaSO3·2H2O. A mathematic reaction model was built based on the chemical reaction of desulfurization by carbide slag, the overall reaction order is1.74, the frequency factor is0.349533643(mol/m3)-0.7402·S-1and the activation energy is21749.56173J/mol.The addition of organic acid to low concentrated carbide slug slurry can improve the rapid dissolution of carbide slug and relieve the scaling problem of carbide slug desulfurization. After the addition citric acid, the desulfurization rate of0.1%mixed grain size carbide slug increased by18.36%with citric acid concentrated5mmol/L. The desulfurization rate of citric acid-carbide slug system increased with the raise in slurry pH and decreased with the raise in inlet SO2concentration and reaction temperature.The kinetic of reactions is the first-level reaction kinetics, total order of reaction is1.1403, the frequency factor is13.8278min-1, response activation energy is14.514kJ/mol.The complex adsorption rate of NO by triethylenediamine cobalt (ii) increased with the raise of triethylenediamine cobalt (ii) concentration and pH and decreased with the raise of inlet NO concentration and temperature, and firstly raise and then dropped with the increase on the ratio of C (Co2+)/C (En) with a best ratio of1:4. The effect of the exist formation of Co2+ion on NO removal rate was:CoEn32+>CoEn22+>CoEn2+>Co2+Under saturated sodium nitrate condition, the removal rate of NO firstly increase and then dropped. The removal rate of NO increased by10.53%when reaction temperature raised form30℃to70℃and dropped by14.94%when raised from70℃to90℃.