Enhancement of gas holdup and oxygen transfer was investigated in the riser of a three-phase circulating fluidized bed, with a diameter of 0.102 m (ID) and a height of 3.5 m, by means of liquid swirling flow. Effects of gas (0.01-0.07 m/s) and liquid (0.17-0.44 m/s) velocities, fluidized solid particle size (1.0, 1.7, 2.1, 3.0 mm), solid circulation rate (2-8 kg/(m 2 s)) and swirling liquid ratio (0-0.5) on the gas holdup and volumetric oxygen transfer coefficient in the riser were examined. The gas holdup and oxygen transfer coefficient could be increased up to 25-30% and 20-25% respectively, by means of liquid swirling flow in the riser. The values of gas holdup and volumetric oxygen transfer coefficients were well correlated in terms of dimensionless groups as well as operation variables within these experimental conditions.

No abstract

Flow properties of gas phase reactants such as size, rising velocity and frequency were investigated in simulated three-phase slurry bubble column reactors. Effects of gas velocity, reactor pressure, liquid viscosity, solid content in the slurry phase and column diameter on the flow properties of a gas reactant were determined. The multiple effects of operating variables on the bubble properties were well visualized by means of contour maps. The effects of operating variables on the flow properties of bubbles changed with changing column diameter of the reactor. The size, rising velocity and frequency of reactant gas bubbles were well correlated in terms of operating variables including column diameter of the reactor.

No abstract

Characteristics of heat transfer were investigated in pressurized slurry bubble column reactors whose diameter was either 0.051, 0.076, 0.102 or 0.152 m (ID) and 1.5 m in height, respectively. Effects of gas velocity (U G ), solid contents (S C ), pressure (P), liquid viscosity (µ L ) and column diameter (D) on the heat transfer coefficient (h) between the immersed vertical heater and the column were determined. Multiple effects such as U G and D, P and D, µ L and D, and S C and D on the value of heat transfer coefficient were discussed. Temperature fluctuations were also measured and analyzed by adapting chaos theory, which was used to explain the effects of operating variables on the heat transfer in the column. The heat transfer coefficient increased with increasing gas velocity, pressure or solid content in the slurry phase, but decreased with increasing liquid viscosity or column diameter. The decrease trend of h with increasing column diameter was somewhat sensitive when the gas velocity was relatively high (U G ≥12 cm/s). The effects of column diameter on the h value became almost linear when the operating pressure (P=4-10 kg f /cm 2 ), liquid viscosity (µ L =20-38 mPa·s) or solid content in the slurry phase (S C =10-20 wt%) was relatively high and gas velocity was relatively low, within these experimental conditions. The heat transfer coefficient was well correlated in terms of dimensionless groups as well as operating variables.