Modelling the minimally fluidized state under reduced pressure

Several aspects of numerically modelling a minimally fluidized gas–solid system have been investigated in this work. The numerical results show that voidage and the resulting pressure drop are not a function of the fluidizing cycle. More interestingly, the pressure drop was not impacted by introducing the lateral axis of gas and solid flow in the 3D models. Under a reduced pressure environment, none of the well-known drag models could capture the effect of the slip flow. A relatively new but not well-known slip flow drag model showed the ability to capture the impact of the slip flow regime. However, improvements in its overall accuracy are desirable. To this extent, the Ergun pressure drop equation was modified to introduce the effect of the slip flow regime. The losses in the slip flow regime were captured by deriving a new correlation using experimental work that predicted a linear relationship between the laminar coefficient and the Knudsen number. The modified Ergun equation showed notable improvement in its pressure drop accuracy. Furthermore, the modified Ergun equation was implemented as a modified Gidaspow drag model. It showed better accuracy in predicting pressure drop and minimum fluidization velocity at reduced pressure for various alumina particle sizes.