The Experimental Study Of The Heat And Mass Transfer Between Gas And Particles In Circulating Fluidized Beds Using Naphthalene Sublimation Technique

Circulating fluidized beds (CFB) Boiler is an efficient and clean combustion facility. Its application is of great significance to China for the reasons of economical and environmental benefits. Great progress has been made in the theory of CFB in these years. However, the theory is far from perfect up to now. In the study of heat transfer in CFB, most researchers focus on the heat transfer between the bed and the wall, few people attach importance to the gas-solid interfacial heat transfer. For better design and use CFB, a model CFB test facility was established, in which the momentum , heat and mass transfer tests were done using naphthalene sublimation technique for the first time.In the CFB experiments, the influence of primary airflow, particle size, and particle circulation rate was investigated, and in the fluidized bed tests, influence of superficial gas velocity, particle size, and weight of bed was discussed. The experimental results showed that the average gas-solid interfacial heat transfer coefficient becomes larger when the fluidized airflow velocity was increased or the particle size becomes smaller. In fluidized bed experiments, the pressure drop of the bed will increase and the Nu between gas and particle will decrease when the bed weight become heavier, in the same time, the bed weight has little effect on minimum fluidization velocity. The CFB experiments also show that with the increase of the particle circulation rate, the voidage decreases and the particle concentration will become larger, the heat and mass transfer between gas and particles were enhanced.