A New Concept of Scallop Screens for Reactors of Refining

Abstract

In a moving bed reactor for catalytic reforming, the catalyst is enclosed inside an annulus constituted by two concentric baskets made of Johnson grid. An innovation introduced by Johnson consists in the replacement of the outer basket by a succession of panels of a new type of scallop, called OptiMiser[TM], set side by side. So, the outer basket of the reactor becomes modular, facilitating the building of the reactor as well as its maintenance, while protecting the efficiency of the process for the gas flow and the pressure drop. Johnson entrusted the technical study of this innovation to IFP. At first, thanks to the theory of the homogenization, a model of elastic anisotropic plate was developed to replace Johnson grids, assembly of wires welded to stiffener bars, named rods. This model was inserted into a finite element method (FEM) code designed for structure calculations (ABAQUS[TM]). The model was first validated thanks to a series of tensile, shear and bending tests performed on grid samples. In a second step, compression and bending tests were run on prototypes of scallop panel. These structure tests were also calculated by using the FEM with the equivalent plate model developed for the Johnson grid. As a conclusion, the model of grids was validated and then approved for further studies of real reactors in operating conditions.