Study On Influence Of Coal Blending And Additives On Sintering Characteristics And Alkali Metals Evaporation And Condensation Of Zhundong Coal Ash

Zhundong coal has a high alkali metal content,which brings severe slagging in furnace and affects the safe and stable operation of the boiler.Coal blending and adding additives are beneficial to reduce the release of alkali metals,thereby slowing down the fouling and slagging of the power plant.At the same time,these two methods can regulate the melting characteristics of coal ash and effectively solve the problem of slagging of Zhundong coal ash.Therefore,this paper studies the effects of coal blending and adding additives on the sintering characteristics of Zhundong coal ash and the evaporation and condensation characteristics of alkali metals.The experimental results were processed and analyzed using digital image processing technology,XRD(X-Ray Diffraction)and SEM-EDX(Scanning Electron Microscopy with Energy Dispersive X-ray).On the one hand,the effects of coal blending and adding additives on the sintering characteristics of coal ash in a horizontal furnace equipped with a CCD(Charge Coupled Device)camera detection system were tested.The experimental results show that the cross-sections of all sintered samples have a three-layer layered structure.Beitashan coal,Wudong coal,and kaolin have effects of preventing sintering and melting,and magnesium-based compounds have no obvious effects.At the final moment,the area and height of the sintered sample after blending coal and adding additives were reduced,and the shrinkage decreased as the proportion increased.XRD analysis results show that the type and proportion of blended coals and additives have an important effect on the formation and change of minerals.The SEM analysis shows that the outermost layer of the sintered ash was severely sintered and contained a lot of pore-like structures.EDX analysis shows that the content of Na and K elements in the surface of the sintered ash generally decreased from the inner layer to the outer,while Ca,Al,and Si elements increased.The trend is that the alkali metal element evaporation decreased after blending coal and adding additives.On the other hand,an air-cooled Fe-Cr-Ni alloy condensation probe wasdesigned to collect evaporated alkali metals and other substances.The effects of coal blending and adding additives on the evaporation and condensation characteristics of alkali metals in Zhundong coal ash were studied.The main conclusions of the experiment are as follows: According to SEM-EDX analysis,it can be seen that a large amount of cubic crystal particles were scattered on the probe after evaporation of the pure Zhundong coal ash sample,and the particles were KCl and NaCl crystals.After coal blending,larger agglomerates were gradually formed,and aluminosilicate deposits were present on the probe.With the increase of coal blending ratio,the evaporation and condensation of Na and K elements decreased.After the additives were added,the addition of kaolin inhibited the evaporation and condensation of Na and K elements,and the inhibition effect of magnesium-based compounds on the evaporation of alkali metals was not obvious.XRD analysis shows that as the proportion of blended coals and additives increased,the intensity of the diffraction peak of wollastonite decreased,the intensity of the diffraction peak of quartz increased,and the background peak became smoother.Beitashan coal,Wudong coal and kaolin can suppress the sintering and melting process,and they are suitable choices for preventing slagging of Zhundong coal ash.