Study On The Formation Mechanism Of Dendritic Carbon During Combustion Of Single-Particle Slime

The study of coal slurry combustion process is closely related to its efficient utilization and application scenario expansion.An interesting phenomenon was found in the study:when single particle coal slurry is burned to generate a flame,the carbon soot particles produced will coalesce on the surface of single particle coal slurry and form flocs of a certain shape,and then the flocs will gradually disappear as the flame disappears due to the oxidation reaction of carbon soot particles in the air.To investigate this phenomenon,not only determined the basic composition and physicochemical properties of flocs,but also explained the growth process of flocs in detail.In this dissertation,firstly,selected the experimental conditions with oxygen content of 20%,flow rate of 0.5L/min,single particle slurry diameter of 10mm,water content of 30%and furnace chamber temperature of 1000℃ through horizontal tube furnace system,and filmed the flocculent generation process by high-speed camera,and took samples to study the flocculent.According to the results of microscopy,Scanning Electron Microscope and Transmission Electron Microscope,the flocs were found to be composed of a large number of carbon soot particles with uniform granularity,and the external appearance resembled a dendrite,among which the carbon soot particles were composed of multiple concentric carbon layers,which were consistent with the characteristics of nano-onion carbon structure.X-ray Diffraction and Raman spectroscopy were used to determine the properties of carbon soot particles,and it was found that the carbon soot particles were onion carbon with low crystallinity and graphitization;under the comprehensive consideration,called the flocculent produced during the combustion of single-particle coal slurry as dendritic carbon.On this basis,further explored the growth of dendritic carbon under different working conditions and the thermal stability of dendritic carbon,and found that a stable flame on the surface of single particle slurry is a necessary condition for dendritic carbon generation,and 400℃ is a critical temperature for dendritic carbon to maintain stability.Then use the experimental phenomena and characterization results as the basis to theoretically analyze the process of single particle slurry combustion to generate dendritic carbon into four stages:firstly,the volatile fraction from single particle slurry is thermally resolved to form carbon soot particles with uniform particle size and low graphitization through secondary chemical reaction;then the carbon soot nanoparticles generated by the reaction are confined within the flame interface of volatile fraction combustion by thermophoretic force,and through Brownian motion and Then,through Brownian motion and thermal migration,the soot particles collide with each other to form a more complex cohesion,forming a specific morphology of dendritic carbon;after that,under the dominant role of soot particle generation,the dendritic carbon grows slowly within the flame interface,and a laminar structure is formed in some areas;finally,as the precipitated volatile fraction decreases,the flame gradually disappears,and the soot particles are oxidized,and the dendritic carbon also gradually disappears.Finally,simulate the agglomeration process of carbon soot particles according to the DLA fractal growth model,which verifies the correctness of the theoretical analysis from the side.