Study On The Effect Of Amorphous Formation During Coal Combustion

Circulating fluidized bed?CFB?has been widely used because of its many advantages,such as high efficiency and low pollution.In practical applications,medium temperature combustion in a CFB results in a generally higher carbon content of fly ash,resulting in energy waste and environmental pollution.Many literatures have studied the problem of carbon content in fly ash from macroscopic perspective,and the literature on the reasons why the microstructure of the internal carbon of the fly ash is difficult to burn is rarely reported.Therefore,starting from the microstructure of fly ash,this article looks for ways to suppress the non-crystal formation on the fly ash surface,so as to achieve the effect of promoting the internal carbon combustion of fly ash.In this thesis,the problem of high carbon content in fly ash collected from a power plant is analyzed.First,fly ash is divided into different particle sizes and different density sections.The carbon content and microstructure characteristics of different density section of fly ash in the same size section are studied.It is found that the content of residual carbon in fly ash has a certain regularity with the density change.The carbon content of fly ash increases first and then decreases with the increase of density.The residue carbon content reached the maximum in the fly ash with density ranging from1.85×10³ kg/m³ to 2.15×10³ kg/m³.The difference in carbon content between small-density fly ash and large-density fly ash is significant.The content of crystalline minerals in fly ash is very few and even distributed in fly ash of all density segments,while the amorphous glass phase is present in a large amount in the fly ash.Because amorphous glass phase is wrapped on residual carbon,it hinders the further combustion of residual carbon.Next,starting from the formation of amorphous glassy phases,the content of amorphous glassy in the burn-out ash formed after combustion of coal is studied by density to study the formation of amorphous glassy in coal combustion.In addition,the method of adding different proportions of kaolin to demineralized coal was used to study the formation of non-crystals in the burn-out ash.The results show that with the proportion of kaolin in coal samples increased,increasing the amount of amorphous glassy formation of coal burn-out ash.Finally,because of the complex and changeable conditions in the CFB,the influence of temperature,oxygen content,Ca O ratio in the coal sample and SO₂ concentration in flue gas on the amorphous glass in fly ash was studied by orthogonal experiment.The results showed that the temperature and oxygen content in CFB had no significant effect on the formation of amorphous glass in fly ash.The addition ratio of CaO and the concentration of SO₂ affect the formation of amorphous glass phase in burnout ash.The addition of CaO inhibits the formation of non-crystals in burnout ash.During coal combustion,the reaction between CaO and amorphous glass and the desulfurization reaction were simultaneous.