Study On The Law Of Synergetic Treatment Of SO₂ And NO_x In Iron Ore Sintering Process Based On The Adjustment Of Iron Ore Sintering Materials

The paper started from the source and taken SO2 and NOx as research objects.It regarded the thought of sintering materials adjustment as guidance that was to the synergetic treatment of sintering flue gas pollutants.The research started from sintering raw materials(iron ore,fuel,fluxes and recycle materials)and established reasonable sintering materials adjustment project which based on analysing the formation mechanism of SO2 and NOx and combining the existed relevant technologies.The influence law of different projects on the emission of S02 and NOx and sinter quality was investigated,as it tries to realize the synergetic treatment of SO2 and NO,on the premise of ensuring sinter quality.The iron ore was classified into two parts,"High Sulphur" iron ore and "Low Sulphur"iron ore,which based on the difference of sulphur contents of iron ore and their adding ratio.The sulphur distribution in the pellet was changed and the compactness of the pellet was increased with the project that adopted the pre-granulation method to put the "High Sulphur" iron ore inside the pellet.Hence,the contact between oxygen and sulphur was reduced,and the sulphur fixation effect of CaO was improved as the temperature difference between inside and outside of the pellet.The sinter-pot test results showed that the emissions of SO2 were reduced by 41.02%.Meanwhile,the project had little effect on the emissions of NOx and the sinter quality.In the pellet with two layers structure that the iron ore distribution was uniform,the distribution pattern got a better effect on the comprehensive emission reduction of SO2 and NOx that put the fuel outside the pellet,and meanwhile put the fluxes outside or inside the pellet.The emissions of S02 and NOx were reduced by 11%and 8.48%,respectively,and the tumbler strength was increased by 1.65%through the project that put the fuel and the fluxes outside the pellet simultaneously.The combustion of fuel was improved and the reductive atmosphere of sinter bed was enhanced when the fuel was put outside the pellet.The sulphur fixation effect of CaO was improved when the fluxes was put outside the pellet,while it would help to the development of calcium ferrite when the fluxes was put inside the pellet.The 3-layers sintering raw materials structure that focused on NOx was developed based on the effect of the distribution of fuel and fluxes in the pellet on the formation of SO2 and NOx.The main characteristic of the structure was that the fuel was coated the outside of the pellet as outer layer,the middle layer was composed by fluxes and 50%iron ore and the inner layer was composed by the rest of 50%iron ore.The structure was helpful to increase the reductive atmosphere of sinter bed.Meanwhile,it promoted the further development of calcium ferrite.The sinter-pot test results showed that the emissions of NOx were reduced by 19.93%and the tumbler strength was increased by 2.68%,while the emissions of SO2 were increased by 17.7%.By the calculation of the accumulation heat effect of the three units of sinter bed,the results showed that the available accumulation heat rate(?avl,%)increased from 33.1%in the 2nd unit to 42.3%in the 3rd unit,while the coke powder addition ratio in raw materials decreased from 7.0%in the 1st unit to 5.5%in the 3rd unit.The sinter-pot test results showed that the fuel consumption,the emissions of SO2,NOx reduced by 7.5kg/t,57.7%and 18.4%,respectively.Meanwhile,the sinter quality was improved.In the sinter-pot test,which added the sintering recycle materials,the emissions of SO2 and NO,were increased by 2.76%,26%,13.1%and 21.9%respectively,with 3%of blast furnace gravity precipitator dust and sintering dust.The emissions of SO2 were increased by 11.4%and 12.6%while the NO,was reduced by 1.40%and 11.5%,respectively,with 3%of steel tail slag and mill scale.Meanwhile,the sintering raw materials with 3%recycle materials had little effect on the sinter quality.Through comprehensive analysis of the effect of recyle materials on the sintering flue gas pollutants and sinter quality,the paper suggested to control the adding ratio of blast furnace gravity precipitator dust was 1%?3%,steel tail slag was 3%?4%,mill scale was 2%?5%,the sintering dust from the 1st and 2nd electric dust collector was 2%?3%and stopped adding the sintering dust from the 3rd and 4th electric dust collector.It is instructive to the establishment of the sintering materials adjustment project that is helpful to the synergetic treatment of SO2 and NOx in iron ore sintering process through the source control measures,such as adjusting the distribution of iron ore,fuel or fluxes in the pellet,reducing the fuel consumption and controlling the use of sintering recycle materials.