Experiment and Model of Wet Sludge Pellet Drying in a Bubbling Fluidized Bed
湿污泥颗粒的流化床干燥实验及模型

Drying characteristics of single municipal sludge pellet in a bubbling fluidized bed where river sand is taken as drying medium are studied for designing bubbling fluidized bed sludge dryers. The effects of drying conditions, such as bed temperature, size of sludge pellet and fluidization velocity, on drying rate are investigated. The results show that the bed temperature and size of sludge pellet affect the drying rates exponentially. The drying rate is larger with higher sludge moisture. When the bed is fluidized at the higher velocities, which are more than 2 times the minimum fluidization velocities, increasing of fluidization velocities (from 2 to 5 times fluidization velocities) can not affect the drying rate. Based on the experimental data, a semi-theoretical model of sludge drying in a bubbling fluidized bed is proposed. The research results can be reference for the design of bubbling fluidized bed sludge dryers.