(575y) Analysis of the Multitubular Reactor for Formaldehyde Production by One-Dimensional Models

In this article the composition and temperature profiles were determined for the reaction of the oxidation of methanol to formaldehyde in an industrial packed bed reactor by means of one-dimensional pseudohomogeneous and one-dimensional heterogeneous models. The results were analyzed obtaining better fits with the heterogeneous model. In order to obtain the numerical solution corresponding to the system of differential equations that describe the system the numerical method of Runge Kutta of 4th order was implemented. A detailed analysis is made about the mechanisms of reaction postulated in the literature for the oxidation of methanol, the formation of sub-products and intermediaries in parallel and consecutive reactions, as well as an analysis of the factibility of the mechanisms proposed by Cozzolino et al (2007) with a generated algorithm that details the Gibbs free energy for the Temperature interval of operation. The kinetics studied correspond to Cozzolino et al (2007) and Windes et al (1989) resulting on an identified hot spot in the range of 620-650 K and 15-30 cm from the entrance of the reactor for the latter, and a difference of 10 K for the first author. The same procedure was developed for the kinetic model of Tesser et al (2003) finding no satisfactory results that describe the system. The shooting numerical method was also developed, in order to accomplish a parametric sensibility analysis by solving a boundary value problem; with this, the three possible disposition of the coolant (cocurrent, countercurrent, constant temperature) were studied to analyze its effect on the hot spot dimension and position along the reactor as well as its changes with the entrance conditions of the reactant mixture finding that the parallel disposition of the coolant is the best alternative in terms of hot spot control.

Keywords: One-dimensional models, Formaldehyde, Methanol, Shooting.