Modelling And Design Of Multitubular Fixed Bed Reactors

Multitubular fixed bed reactors (MTR) are important equipments in the chemical and petrochemical industries, which commonly used for highly exothermic reactions. The conventional approach to model MTR is based on a single tube which is considered as a good representation of the multitubular unit. As a consequence, the coolant flow and temperature distributions along the reactor are ignored, but this cannot be acceptable except for pure parallel flow reactors.In this work, a two-dimensional cell model was adopted to determine the shell side flow distribution in a multitubular reactor. The method is adopted to the widespread type of industrial reactors, the reactors fitted with disk-and-doughnut baffles and reactors fitted with segmental baffles. Flow is assumed to be perpendicular to the bundle and parallel to the tubes and leaks through the tube to baffle annular holes are also considered. The model enables the evaluation of the effect of shell-side hydrodynamics upon the operation of a MTR processing an highly exothermic reaction of o-xylene to phthalic anhydride.The model enables the evaluation of the effect of operating parameters and shell hydrodynamics upon the MTR. It shows that small tube diameter, large tube pitch, small baffle window, and small clearance of tube-and-baffle will improve coolant distribution. In addition, it shows that the MTR fitted with disk-and-doughnut baffles are far advantageous than the MTR with segmental baffles.