Reator cilíndrico-elíptico de leito fixo. Avaliações fenomenológica e geométrica transientes.

Abstract

Fixed bed tubular reactors are widely used equipment in the industry, in operations such as absorption, adsorption, catalysis of highly endothermic or exothermic chemical reactions, among others, in order to generate products of highly aggregated commercial value. Its conception consists of an arrangement of porous particles established in a fixed manner along its bed, where a fluid (or combination of more than one) is drawn, which percolates the arrangement of particles of the bed by performing the necessary exchanges of heat and mass between the fluid and solid species (particles) involved. Its design is usually marked by difficulties in the knowledge of the nature of thermal parameters, and research are often limited to conventional cylindrical-circular geometry and steady-state operation, with constant thermophysical properties throughout the domain, as well as the uni or two-dimensional approach. In this sense, this work studied the transient three-dimensional heat transfer in a fixed-bed cylindrical-elliptical reactor by numerical simulation using the finite volume method, with variable thermophysical properties, a curvilinear temperature profile at the reactor inlet and a variable porosity model with the position of the bed. The results confirm that: 1) By varying the geometric aspect ratio (L2/L1) practically does not change the operational conditions of the reactor; 2) As the velocity of air at the reactor inlet increases, the faster the permanent regime is reached; 3) A variable temperature profile with the position at the reactor inlet, compared to a flat profile of the same average temperature, greatly changes the temperature field of the reactor; 4) A constant porosity profile obtained from the mean of the variable porosity profile does not significantly alter the temperature distribution; 5) With a first-order chemical reaction term in the modeling, the temperature field only undergoes significant changes at high reagent concentrations or with increasing reagent temperature at the reactor inlet.