(223g) Electrical Capacitance Volume Tomography Studies of Characteristics of Gas-Solid Slugging Fluidization with Geldart Group D Particles Under Elevated Temperatures

Slugging which occurs in a fluidized bed with a large height-to-diameter ratio is a major gas-solid fluidization regime. The slugging regime is commonly examined under the ambient condition. With the development of the electrical capacitance volume tomography (ECVT) sensors and measurement technique, the slugging phenomena can now be examined under elevated temperature conditions in a greater detail. The 3-dimensional images from the ECVT sensor can provide the slugging properties such as shape, size, volume fraction and velocity, thereby providing overall understanding of the slugging behavior in a fluidized bed at elevated temperatures. In this study, the ECVT sensor is applied to a slugging fluidized bed with a 0.075 m diameter with solids particles of 1.5 mm diameter and 2500 kg/m3 density. Square-nosed slugs are observed in the bed. It is found that the time intervals between two slugs decreases with the increase in the gas velocity and reaches a steady value at about 1s per slug when the gas velocity is about 1.7 m/s above the minimum fluidization velocity. Under the ambient temperature, when the gas velocity is lower, the bed fluctuates with a high frequency mainly due to bubbles. However, under elevated temperatures, this phenomenon is not observed. The slug rising velocity increases linearly with the gas velocity. However, its value is lower than that of the round-nosed slugs as calculated from previously proposed equations based on the two-phase theory.