Study Of The Formation Process Of Soot During Fluid Catalytic Cracking Pyrolysis And Combustion

The formation process of soot in the non-premixed flame of the mixed slurry of fluid catalytic cracking slurry and diesel oil is studied by two-color method,molecular dynamics simulation and computational fluid dynamics(CFD).Based on the two-color method,it is found that the non-premixed combustion flame in an open environment is divided into flame core(oxygen-rich combustion zone),inner flame(oxygen-poor combustion zone),outer flame.The flame core temperature is the highest,the inner flame temperature is the lowest,and the outer flame temperature is between the flame temperature and the inner flame temperature.The flame core and outer flame have a small volume concentration of soot.The inner flame has a large volume concentration of soot.As the molar ratio of oxygen to carbon increases,the volume concentration of soot decreases.As the mass fraction of FCC in the slurry increases,the volume concentration of soot increases.LAMMPS has been adopted to learn the nascent soot particles(NSPs)formation process,in which,decahydronaphthalene,naphthalene,2-methylnaphthalene,and 1-Ethylpyrene are used as the model compound for fluid catalytic cracking(FCC)slurry.The study shows that the formation of the NSPs at 600K is mainly due to the physical aggregation.At the temperature range of 1100K-1700K,model compound molecules are in a dynamic process of gathering and separating.At the temperature above 2100K,the formation of NSPs is mainly due to the chemical nucleation.The carbon-hydrogen bonds of the model compound are broken firstly,then the carbon-carbon bonds are broken into a large number of short carbon chains,and the short carbon chains are bonded and cyclized to form the initial soot particles.At 2500K,water molecules promote the pyrolysis of the model compound molecules to form short carbon chains and react with short carbon chains to form molecules such as carbon monoxide and methane.The formation of hydroxyl radicals by oxygen molecules causes oxidation of the model compound molecules,and the carbon atoms exist as small molecules.Water molecules and oxygen molecules show an inhibitory effect on the formation of NSPs.The soot particles eventually form sphere structure.The CFD is used to calculate the flame of the slurry based on the non-premixed combustion model.It is found that the model is suitable for the flame core and inner flame of the non-premixed combustion of oil slurry and oxygen.The process of pyrolysis of the fuel obtained from the position at which the peak of the molar concentration of the radical and the small molecule occurs is consistent with the conclusion obtained by the process of pyrolysis of the fuel calculated based on the molecular simulation.Based on the experimental data,an empirical model for calculating the soot volume concentration in the non-premixed combustion flame of the catalytic slurry and the diesel mixed slurry is calculated.