Experimental Studies On Hydrodynamics And Key Models In An Ebullated-Bed Reactor At High Solid Holdups

Ebullated-Bed Reactor (EBR) has been widely used in petrochemical, bio-chemical, waste water treatment, coal liquefaction, et al. It offers many advantages such as simple construction, perfect heat transfer performance, easy to control temperature and low operation costs. It has important scientific value and industrial applications in further research on EBR.In this paper, we combined the industrial equipment and condition of residue hydrotreating reactor, and established a cold flow installation with diameter of 0.3 m and height of 7.2 m. In order to approach the real flow in the commercial scale EBR, we used air-water-spherical alumina to simulate the hydrodynamics of gas-liquid-solid phase. We got a large number of experimental data, including the key model parameters such as total gas holdup, rise velocity of large and small bubble, gas-liquid mass transfer coefficient, circulation velocity of liquid and solid, axial solid concentration distribution. Moreover, the effects of superficial gas velocity (0.025～0.232 m·s-1), super liquid velocity (0～0.0219 m·s-1), liquid viscosity (1.2～210.4 mPa-s) and solid holdup (0-60vol%) on these hydrodynamics were discussed. The results showed that the total gas holdup, bubble rise velocity, gas-liquid mass transfer coefficient and solid circulation velocity increased with an increase of superficial gas velocity. The liquid velocity had no significant influence on the hydrodynamics. It would decrease small bubble holdup, total gas holdup and bubble rise velocity with the increasing of liquid viscosity. Additionally, the viscous system would unify the axial solid distribution. The solid holdup affected the hydrodynamics as the same as liquid viscosity, i.e. viscosity would increased with an increase of solid holdup.By using drift flux model and fitting the experimental data with model parameters, we obtained the empirical correlation of gas holdup and bubble rise velocity under the condition of high solid holdup (60vol%). We modified one-dimensional sedimentation-dispersion model parameters, and got a new model which can be applicable to a wider range.