Low-temperature Experiments Of Sintering Flue Gas Desulfurization And Denitrification In A Bubble Column

Nitrogen oxides?NO_x?and sulfur dioxide?SO₂?produced by the steel sintering process are the major air pollutants emitted by the iron and steel enterprises.Different from the coal-fired flue gas,the sintering flue gas-has-the-characteristics of large change in gas volume,wide temperature fluctuation and low NO_x content.Therefore,the existing desulphurization and denitrification technologies of coal-fired power plant cannot be directly applied to sintering flue gas.At present,the desulfurization technologies of sintering flue gas are relatively mature,while the researches of corresponding denitrification technologies were carried out less.With the gradual improvement of environmental requirements,the denitrification of sintering flue gas has been put on the agenda.Due to the high cost of new denitrification equipment,the work of emission reduction moves slowly.To this end,the low-temperature experimental study of sintering flue gas desulfurization and denitrification was carried out in a Bubble Column.By adding a new type of composite oxidant to the lime slurry and adjusting the operating conditions to achieve the purpose of not reducing the original desulfurization efficiency and removing the nitrogen oxides partially.Finally,the export sintered flue gas meets the national emission standards.According to the reduction potential of the nitrogen oxides and their acid ions,the condition under which NO could be oxidized was determined.Combined with the existing research results,the range of effective oxidants was defined.And the tests were carried out on a small test platform which constructed with the 2x220m² sintering flue gas desulfurization tower at Nanjing Iron&Steel Co.,Ltd,.On the basis of the technical and economical evaluation for different oxidants,the oxidizing agents of NaClO₂ and NaClO were chosen for the main research objects.Based on the thermodynamics and kinetic principle of chemical reaction,it was theoretically proved that NO and SO₂ could be removed effectively by NaClO₂/NaClO/CaCO₃,and the desulfurization and denitrification reaction could be carried out spontaneously with a deep limit?A further experimental study on the desulfurization and denitrification reaction of NaClO₂/NaClO/CaCO₃ solution was carried out.The thermodynamic parameters such as Gaussian free energy change function,equilibrium constant and gas equilibrium pressure are calculated by using the thermodynamics of the reaction.The influence of gas concentration on the absorption rate was analyzed by reaction kinetics.The effects of various operating parameters such as NaClO₂ concentration?m_a?,NaClO concentration?m_b?,molar ratio of NaClO₂ and NaClO?M?,solution temperature?T_R?,initial solution pH,gas flow?V_g?and inlet concentration of SO₂?C_s?and NO?C_N?on the removal efficiencies of SO₂ and NO were discussed.In addition,the compound oxidizer mixed solution and reaction products were quantitatively and qualitatively analyzed.It was revealed that the optimal experimental conditions were M=1.3?m_a=4mmol/L?m_b=3mmol/L?,m_c=20g/L,pH=5,T_R=55?,V_g=1m³/h,C_N=400mg/m³,C_s= 1100mg/m³,under which the average efficiencies of desulfurization and denitrification could reach 98.1%and 56.9%,respectively.NaClO₂ and NaClO could react under acidic conditions and the strong oxidizing gas ClO₂ and Cl₂ were produced,which improved the oxidation performance of the solution.During the reaction process,SO₂ and NO in the flue gas were completely removed in the form of CaSO₄ and NO₃^-.When M=1.3,each consumption of 1g of NaClO₂/NaClO,to the solution and gypsum in the introduction of the contents of Cl were 420.6439mg,0.5465mg,did not cause corrosion of equipment.Based on the above research results,the engineering experiments were carried out on the 2x220m² sintering flue gas desulfurization system.The results indicated that NO_x in sintering flue gas can be partially removed by using NaClO₂/NaClO/CaCO₃ solution,and the original desulfurization efficiency of the system will not be reduced.The treated flue gas could meet the national emission standard and the processes had no adverse effect on the system.The new cost of the technology is only 563,000 yuan per year,with high economic efficiency.