Abstract: The method to calculate the vaporization rate of slurry was developed by the group contribution method based on the vapor-liquid equilibrium theory and used to predict the vaporization rates of slurry in the industrial RFCC disengager. The effect of oil vapor temperature and partial pressure of slurry on the bubble point, dew point temperature and vaporization rates of slurry were investigated. Results show that at constant slurry partial pressure the vaporization rate ascend with increasing temperature of the oil vapor. Besides, when the temperature is constant, the bubble point and the dew point decline with slurry partial pressure reduction, while the vaporization rates of the slurry go up. According to the least square method, the correlation of the slurry vaporization rates and operation conditions was established for predicting the vaporization rate of the slurry under different operating conditions. It can provide a simple mathematical model to determine the condensate amount in the disengager.