Flow And Sedimentation Characteristics Of Coke Particles In Slurry Bed Of Heavy Oil Hydrogenation

In the process of heavy oil hydrogenation,the coke generation problem seriously restricts the development of the slurry bed hydrogenation process of heavy oil.It is of great significance to analyze the flow and deposition characteristics of coke particles in the slurry bed to optimize the process.In this paper,a multiphase flow model of slurry bed with inlet distributor is developed based on the coupled TFM-DPM model using numerical simulation,considering the influence of feed distributor on multiphase flow and combining the characteristics of low solid phase concentration(below 3% by volume fraction).Firstly,the model was established and validated by using air-water-glass beads as the simulation medium,and then the model was applied to study the multiphase flow characteristics of hydrogen-residue-coke system to reveal the flow and deposition pattern of coke particles in slurry bed.The results show that the multiphase flow distribution in the slurry bed is more uniform when the feed distributor has a larger opening ratio and a more uniform pore distribution,and that the tubular type has the best performance among the different types of inlet distributors used.The increase of apparent gas velocity will reduce the influence range of feed distributor,speed up the development of gas,liquid and solid phases in the slurry bed,and the velocity of particles moving up and down becomes larger,which intensifies the flow of particles in the bed and effectively alleviates the problems of hanging wall and bottom accumulation of particles,which is conducive to the smooth operation of slurry bed.When increasing the particle concentration,the accumulation of particles at the bottom is aggravated,the uniformity of distribution is reduced,the particle velocity becomes smaller,and the circulation capacity decreases,which is not conducive to the long-term operation of the equipment.Comparing the simulation results of the model system(air-water-glass beads)and the real system(hydrogen-slag oil-coke),it was found that the air-water-glass bead system slowed down the development process of the real system.In the real system,the multiphase flow development in the slurry bed is faster and more stable,and the distribution of gas-liquid-solid phases in the slurry bed is more uniform,revealing the necessity of using real system media for simulation studies.