Hydrodynamic design of multiphase bubble column reactors: An experimental and theoretical study

An understanding of three phase flow hydrodynamics and flow pattern are necessary for the design and scaleup of bubble column reactors. Gas phase residence time is an important parameter that depends on superficial gas velocity and gas holdup in the bubble column. There was no study reported in the literature on residence time in multiphase bubble columns. Since residence time can be easily determined from gas holdup measurements, and can be visualized in terms of the variables of the bubble column reactor, it will give a better understanding of reactor hydrodynamics. The study of porous plate gas distributors is important because of their improved hydrodynamic performance.; This work emphasized the study of three phase flow hydrodynamics including flow patterns and holdup of three phases and gas phase residence time. The effects of solid particle size, solid concentration, density of solids, viscosity of slurry, gas distributor and column diameter and height on hydrodynamics were studied.; The key findings of the effect of solids on gas holdup is that gas holdup increases with increasing solids concentration up to approximately three weight percent. As solid concentration increases further gas holdup steadily decreases. The residence time distribution using solids showed the same shape as in two phase flow for solid concentrations up to ten weight percent. Beyond ten weight percent, the shape of the residence time curve using a porous plate gas distributor is similar to that of sieve plate due to rapid coalescence of gas bubbles right at the gas distributor.; Both linear and non linear regression analysis were performed on gas holdup and residence time as a function of superficial gas velocity and other variables in all three flow patterns. In our region of interest gas velocity, gas distributor and solid concentration are the most important variables.; The outcome of this research will yield a better understanding of residence time, interfacial area, and the transition from one flow pattern to another in the operating region of interest to direct coal liquefaction reactors. Improved design techniques will allow more accurate prediction of the height and diameter of coal liquefaction bubble column reactors.