Study on the flow behavior in spout-fluid bed with a draft tube of sub-millimeter grade silicon particles

• Cylindrical spout-fluid bed with a draft tube investigates at cold bed conditions.
• The effect of fluidizing gas and geometrical parameters of flow behavior are examined.
• A new correlation is proposed to predict minimum spout-fluidizing velocity.
• The regime map based the measured data is presented.
• The introduction of sub-millimeter grade silicon particles lays a basis for potential applications.

An experimental study on gas-particle flow behavior in a spout-fluid bed with a draft tube was performed in a 182 mm diameter cylindrical column with a flat distributor. Sub-millimeter grade silicon particles with wide particle size distribution were used as bed materials to investigate the effect of operating conditions and geometrical parameters on the flow behavior. The pressure drop and its standard deviation were recorded using a capacitive differential pressure transducer, which can be applied to evaluate the hydrodynamic properties. The effects of fluidizing gas and geometrical parameters of the bed on the hydrodynamic characteristics were analyzed. The results show that the minimum spout-fluidizing velocity increases with increasing the length of entrainment zone and the draft tube diameter, but it decreases with the increasing of fluidizing gas flow rate and static bed height. Furthermore, a correlation on the minimum spout-fluidizing velocity which has practical value is proposed based on the present experimental data, and the calculated data is in good agreement with the experimental results. In addition, seven flow regions can also be observed in different spouting and fluidizing gas velocity, and a new flow regime map for a spout-fluid bed is established with the consideration of the influence of flow regime on geometrical parameters. Such results mentioned above can provide important information on the flow behavior in the spout-fluid bed with a draft tube for process design.