(204b) A New Model for Liquid Bridges in Wet Particles in Fluidisation

Addition of liquid into a fluidised bed of gas-solid flow is a common operation in industry. For instance, in fluidised catalytic cracking reactors the sprayed droplets introduced through atomisers may spread on the surface of hot catalyst particles and vaporise to enhance the cracking efficiency. The addition of liquid can give rise to strong cohesion between particles with the formation of liquid bridges that strongly affect the fluidisation.

In this paper we present a new model framework for liquid-bridge force is proposed to improve CFD-DEM simulation of wet particle fluidization. We integrated a temporal-scale criterion into the original spatial-scale threshold for liquid bridge force. Thus, a liquid bridge is allowed to form and remains stable when the normal relative velocity of two particles is lower than a critical value, in addition to the critical distance criterion. We show that the comparison between the predicted bubble behaviour and the measurements strongly indicates that there exists a critical particle velocity to impact lifetime of liquid bridge. If the relative velocity of particles is greater than the critical velocity of approach, the bridge might not experience a complete lifecycle. With the new model, the prediction of bubble properties including bubble centre, shape, and volume agrees well with the measurements in literature.