Research On The Ammonium Chloride Deposition In Coal-fired Power Plant And The Melting Characteristics Of High-iron Coal

Using coal resources cleanly and efficiently is significant to China's social and economic development.In this work,the effects of ammonium chloride deposition during NOx removal by Selective Catalytic Reduction?SCR?and the influence of different combustion atmosphere conditions on the melting characteristics of Zhundong Coal were studied.Firstly,the deposition behavior of fly ash and NH₄Cl was studied by a charge-coupled device?CCD?camera in a drop tube furnace?DTF?under the condition of the NH₄Cl atmosphere.To investigate the effect of surface temperature on the deposition characteristics,setting the surface temperature at 363 K,373 K,and 383 K,respectively.Collected deposit samples were analyzed by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,and energy dispersive spectrometer?EDS?.The results showed that the lower surface temperature was more conducive to the growth of the deposition.The primary substance of the deposited sediments was salammoniac?NH₄Cl?.The crystal granules of NH₄Cl in the deposited sediments had no visible adhesion with fly ash at the micro-scale.The sedimentary material was hard,non-sticky,and easy to be cracked.The deposited layer of greater thickness could cause a severer declination in the heat transfer efficiency of the surface.Secondly,use a new visualization experimental device to study the melting characteristics of Zhundong coal under different oxygen-enriched,water-oxygen,and carbon dioxide atmosphere conditions:a CCD camera recorded the process of the Zhundong coal powder deformation on the hot stage.Use the digital image technology to analyze and calculate the area change of pulverized coal samples at different temperatures.The melting temperature of the pulverized coal corresponding to the characteristic points of the area change,then compare the melting characteristics of Zhundong coal under different oxygen-enriched,water-oxygen,and carbon dioxide atmosphere conditions.The results have shown that as the oxygen concentration increases,the temperature at which pulverized coal begins to melt decreases.As the water vapor concentration decreases,the temperature at which pulverized coal begins to melt increases.Water vapor and an oxygen-rich atmosphere can promote the melting behavior of Zhundong pulverized coal.In an atmosphere containing carbon dioxide,the melting process of Zhundong coal powder may occur in multiple stages.Finally,use FeS₂ as an additive to study the effect of iron minerals on the melting characteristics of Zhundong coal under different atmospheres.Use the digital image technology to analyze and calculate the area change of the pulverized coal sample at different temperatures.Then the melting temperatures of the pulverized coal corresponding to the characteristic point of the area change were obtained.XRD analysis was performed on the molten coal powder under the effect of the additive.The results showed that the additive FeS₂ could reduce the melting temperature of Zhundong coal.Moreover,when Zhundong coal starts to melt,the types of glass phase Fe-containing minerals detected are related to atmospheric conditions.As the temperature rises,some Fe²⁺-containing minerals are oxidized to Fe₂O₃.