Study On The SO₃ Formation Characteristics Of High Sulfur Coal

At present,there are few studies on the formation of SO3.When the boiler is running,the SO3 will generate at the high temperature region,and the fly ash in the flue gas will also have a significant impact on the generation of SO3.Therefore,it is important to study the influence of fly ash on the generation of SO3.Especially in the case of burning the high sulfur coal,the SO3 concentration was high in flue gas.And the problem of the boiler equipment corrosion and air preheater clogging is very serious.In this paper,six kinds of pulverized coal with different sulfur content were selected.The characteristics and sulfur release characteristics of different kinds of pulverized coal were studied by using industrial analysis,elemental analysis,ash composition analysis,XRD research and sulfur analyzer.The theoretical SO2 concentration produced by each kind of coal was determined by the correlation calculation.The SO2-SO3 transformation experiment was carried.The SO3 formation of different fly ash and the effect of sulfate component on the formation of SO3 were studied.According to the result of sulfur measurement,0-500? is the main temperature range of the sulfur release,and the release of sulfur at 900-1200? was higher than 500-900?.Through the result of XRD,the most obvious difference between 900? fly ash and 500? fly ash was that the peak of Na2SO4 at 20=25.5°disappeared.Therefore,some sulfates may react with some material in fly ash to form complex sulfate at the high temperature.Through the SO3 generation experiment,the SO3 concentration of each fly ash increased with the increase of temperature.And it was closely related to the SO2 estimated concentration of each coal.The SO2 and O2 concentration had effect on the SO3 formation.It was found that the SO3 concentration increased and the rate of SO3 formation decreased with the increase of SO2 concentration.When the O2 content was below 5%,the O2 concentration had great influence on the SO3 generation rate.When the oxygen content was higher than 5%,the change of O2 concentration had little effect on the SO3 generation rate.Therefore,the reduction of O2 has an important inhibitory effect on the formation of SO3.The formation concentration of SO3 decreased slightly after feeding the MgSO4 and CaSO4 in fly ash.MgSO4 and CaSO4 can react with Fe2O3 to form complex inorganic minerals.The content of iron oxides reduced,resulting in the decrease of the SO3 concentration.After adding K2SO4,Na2SOa,the SO3 concentration increased.It may be that at the high temperature range,K2SO4 and Na2SO4 combine with some material in fly ash to form complex sulfate.After adding composite sulfate of NaFe(SO4)2 and KFe(SO4)2,the SO3 concentration of changed obviously.