Page 270 - Modeling of Chemical Kinetics and Reactor Design

240 Modeling of Chemical Kinetics and Reactor Design

Figure 4-14. A two-phase tubular flow reactor (e.g., gas-liquid bubble reactor
for oxidation of pollutants in water). (Source: J. M. Smith, Chemical Engineering
Kinetics, 3rd ed., McGraw-Hill, Inc. 1981.)

The effect of physical processes on reactor performance is more
complex than for two-phase systems because both gas-liquid and
liquid-solid interphase transport effects may be coupled with the
intrinsic rate. The most common types of three-phase reactors are the
slurry and trickle-bed reactors. These have found wide applications in
the petroleum industry. A slurry reactor is a multi-phase flow reactor
in which the reactant gas is bubbled through a solution containing solid
catalyst particles. The reactor may operate continuously as a steady
flow system with respect to both gas and liquid phases. Alternatively,
a fixed charge of liquid is initially added to the stirred vessel, and
the gas is continuously added such that the reactor is batch with
respect to the liquid phase. This method is used in some hydrogenation
reactions such as hydrogenation of oils in a slurry of nickel catalyst
particles. Figure 4-15 shows a slurry-type reactor used for poly-
merization of ethylene in a slurry of solid catalyst particles in a solvent
of cyclohexane.