Abstract:
Use of simulation software like COMSOL multiphysics is the economic way to study the coupled reaction rate, heat transfer, mass transfer and fluid flow of reaction. The esterification reaction is kinetic limited with 65% conversion with homogenous catalysis. One of the methods is to shift the equilibrium is to prevail non-homogenous conditions in reaction, which could be obtained by feeding ethanol using microbubbles. The simulation model is developed for esterification reaction occurring at the skin of the bubbles. The larger surface area to volume ratio of microbubbles is an important parameter in the production of ethyl acetate. The surface to volume ratio is inversely proportional to coalescence diameter. The microbubbles of ethanol are used to increases the reaction rate and yield. Different reaction rates models are studied with different catalyst including new experimental model. Bubble diameter is varied and effect on rising velocity, bubble shape, Reynolds number, heat transfer and mass transfer is studied. Bubble coalescence is important factor in the mass transport in the reactor. The borosilicate glass disk with 90-micron pore size created the perfect sphere bubble shape with small interaction with other bubbles. The path followed by bubbles at low Re is straight path. The mass transport coefficient is inversely proportional to diameter of bubble. The internal circulations in the bubble is recommended for enhance mass transport and satisfies the experimental results. The 50 and 100-micron bubble will act as solid sphere with no internal circulations, while180-micron bubble with internal circulation is recommended, which is obtained by Tausge correlation. The bed height must be kept as high as possible so that the bubbles may get proper hold up inside the reactor to complete the reaction. The heat transport will take place from bulk acetic acid to the inside of ethanol bubble. For the smaller bubble the heat transfer will take place much quicker. In the chemical reaction engineering simulation, the time of reaction is about 13 minutes and the experimental results shows the time of 30 minutes. For esterification H2SO4 model, the time obtained from the simulation is same as that of experimental results of 2hrs. The simulation study of air lift loop system of reactor showed the enhanced mass transport with no wetting with walls of reactor.
