Study On The Preparation Of Needle Coke By High Quality Carbonization Of FCC Decant Oil

FCC decant oil is rich in 3-5 polycyclic rings with less impurity,which is a high-quality feedstock for preparing needle coke.The general process methods do not have competitive advantages in terms of quality and yield of needle coke in the face of gradual release of domestic needle coke production capacity.Therefore,it is of great significance to study a new method of preparing needle coke by high quality carbonization.In order to provide technical support and theoretical guidance for quality carbonization of FCC decant oil,the influence of feedstock on needle coke products under the conditions of variable temperature carbonization,decompressing carbonization and recycle of hydrogen donor carbonization was studied in this paper.In this paper,three fractions of a FCC decant oil were used as feedstocks.First,the feedstocks were analyzed by combining the basic properties and composition.The effect of feedtsocks composition on the properties of needle coke was studied by characterizing the carbonization products.In addition,the effect of decompressing airflow on the needle coke product was studied,and the order degree of needle coke（ODN）of the product was characterized by polarizing microscope for the first time.Finally,based on the evaluation of hydrogen supply capacity by chemical probe method,the relationship between recycle of hydrogen doner carbonization and efficient carbonization of needle coke was studied by strong hydrogen supply and tetrahydronaphthalene.The results show that FCC#2（400-450℃）can be used to produce needle coke with the best microstructure,the lowest thermal expansion coefficient and high yield（46%）due to its high aromatics and suitable naphthenes content（aromatics/naphthenes=1.61）.In the first stage of variable temperature carbonization,the temperature T₁ affected the development of the mesopase,and the temperature being too high or too low would easily cause the mosaic structure.In the second stage,the temperature T₂ mainly affected the solidification of the mesopase,and the solid could not be carried out completely if the temperature was too low.The optimal temperature conditions of variable temperature carbonization were T₁=420℃and T₂=500℃.In the solidification stage of carbonization process,decompression can enhance gasflowing-induced coke fibration and increase the order degree of coke generate suitable,but too low decompression pressure will cause the disorder of coke structure.When the decompression pressure is 0.5 MPa,the best order degree and performance of needle coke can be obtained.Hydrogen-donor recycling is beneficial for high quality carbonization to prepare needle coke.The higher the content of active hydrogen supplied to the feedstock,the longer the development time of mesopase,and the better the structure of coke.When the cycle ratio is 0.2,the coke yield can be increased by 17%.