Studies On Hydrodynamic Characteristics Of Novel Spouted Beds

Spouted bed is one of a new-style dryer which will be applied widely because of its higher thermal-efficiency,simple structure and capability of dealing with heat-sensitive materials and so on. Draft tube spouted bed, a new improved dryer, is more effective, because of its enlargement of bed height. But it has some limitations of geometry structure, so scaling up the draft tube spouted bed is an urgent task.The gas distribution and hydrodynamic characteristic of particle at the outlet of draft tube is deduced and differential equations were set up. The set of equations were solved.Then, experiments, which is used to test the percentage of wheat falling back to the draft tube and the distribution of wheat falling to the annular, is carried out through in a draft tube spouted bed. The theoretic value and the experimental value are similar to each other, and both of them all show that, along with the enlargement of diameter of draft tube, the percentage of wheat falling back to the draft tube is consequently increased, but the distribution of wheat in the annular doesn't change. The equation ,which represents relationship between percentage of material falling back, draft tube diameter and velocity of gas is set up.Experiments with wheat is carried out through in a two-dimension draft plate spouted bed which is made of glass to study its hydrodynamic characteristics and the movement of wheat in the spouted bed.To reduce the percentage of particles falling back and asymmetric distribution in annual, a novel rotating draft tube is presented. It's hydrodynamic characteristic is studied, and equation to represent particle movement and pressure drop are set up.Hydrodynamic experiments are carried out in a rotating draft tube spouted bed. The results show that the rotating draft tube can improve the movement of particles and change the distribution of particle in the annular. Also with the distance between inlet and draft tube changed gradually, the maximal pressure drop can be avoided.Drying mechanism in a rotating draft tube spouted bed is analyzed.The model of heat and mass transfer coefficient are set up. A drying experiment for wheat is carried out in the bed to study drying rate,the temperature and humidity of exit air.