Hydrodynamic studies on circulating fluidized bed (CFB) boiler's loop seal components.

摘要

The three aspects of this study are as follows: The flow of solids through the recycle chamber of a loop seal in a circulating fluidized bed (CFB) was studied. The effect of different parameters on the velocity of solid overflowing the recycle chamber was investigated. The sharp-crested weir theory of free surface water flow was used to analyze the solid flow through the loop seal. The analysis gives a good indication of the validity of the theory for solids overflow over a weir. The results show that the solid flow rate increases with increase in bed height above the weir and the solid size had no effect on the value of the weir coefficient.; The mechanism of solids flow (Gs) through a loop seal was studied to identify how the passage connecting the two chambers of a loop seal affect the solids flow. Experiments performed indicated that the passage length has an effect on the Gs. The results also revealed that the major geometric parameter to be considered here should be the ratio of the passage length to the passage height. Further experiments conducted on different solid particles confirmed the size and shape of particles have effect on the inter-particle frictional forces that reduces the mobility of the solids.; In a CFB boiler, both gas-solid behaviour in the riser and solid circulation rate are strongly dependent upon the pressure at different sections. To obtain the distribution of solids, the pressure balance around the loop is needed. The pressure balance is also required in analysing the flow behaviour. This research investigates the pressure balance along the CFB loop and how the pressure drop at different sections adjusts automatically to changes in solids circulation rate.