Design of slurry bubble column reactor and its application to Fischer-Tropsch synthesis

Abstract

Bubble column reactors have a wide range of applications in industry including fermentation and coal liquefaction, owing to their intrinsic advantages, such as high heat and mass-transfer rates, low operating and maintenance costs, lack of moving parts, simple construction, operation versatility, and large interfacial area. However, the hydrodynamics of these reactors is quite complex. Moreover, despite the extensive research in this field, elucidation of the design and scale-up of such reactors is far from complete. In this thesis, individual design elements (such as reactor dimension, gas distributor, redistributor, and gas recycling system) within bubble column were studied identifying their influences on the hydrodynamic behavior of bubbles. Those design elements were applied to pilot-scaled slurry bubble column for Fischer-Tropsch synthesis (FTS). Firstly, the possible events during bubble formation on an orifice were investigated using a rectangular bubble column. At the high gas flow rate, the bubble formation process was complicated by diverse events, such as wake effect, channeling, and orifice-induced turbulent flow. The detachment period could be used to discern the bubble formation steps because it was strongly affected by the above events. The bubble size distribution around the orifice was also analyzed to gain a clearer understanding of the bubble formation process. Above the rate of 3.0 dm3/min through a single orifice, the detachment period converged to a value of 25 msec irrespective of the orifice diameter. The bubble size distribution also showed little difference in this range of gas flow rate. This could be explained by the development of turbulent flow around the orifice. A 0.15-m in-diameter bubble column was tested to investigate the effect of orifice-induced turbulent flow on the regime transition in which the homogeneous flow regime is converted into the heterogeneous flow regime in the column. Obvious distinction between the orifice...