Reactor Design Improvements for a Propane Autothermal Reformer by Simulation of Momentum Flow

Abstract: The paper presents a two-dimensional model to describe the gas flow in a propane autothermal reactor, developed at the CNR-ITAE Institute, and aimed to design a βeta 5 kWe hydrogen generator, named HYGen II, to be used with Polymer Electrolyte Fuel Cells (PEFCs) for residential applications. The main aim of the mathematical model was to optimize the reactor geometrical key parameters (diameter and length of catalyst bed, diameter and shape of the catalyst, etc,) by parametric analysis. The distribution of the linear velocity in different sections of the reactor were evaluated, in order to identify the best location to place the catalyst bed. Based upon the above considerations, a mathematical model, based on momentum balances, has been developed. Keywords: Comsol Multiphysics 3.2, Porous and Free Media Flow Coupling, Reactor Design Optimization, Hydrogen Generator. 1. Introduction During the last few years, research activity on autothermal reforming for small scale applications has been focused on simulation studies to optimize system design and maximize hydrogen production, to gain insight into the factors that limit performance in each component of a fuel processor. Nevertheless, the aspects related to system integration were not studied in depth. In this paper an innovate design of a 5 kWe hydrogen generator, (operating with methane, propane, LPG, butane), based on the experimental results obtained on a laboratory scale [1] and on our previous HYGen I system [2, 3, 4], is reported. The results of these experiments made it possible to identify the reaction conditions and the catalyst formulations in order to assure high activity, good thermal, mechanical and chemical stability for prolonged start-up and shut-down cycles in a compact (low volume and weight) reactor, and to validate heat and mass balance, indicating the system’s drawbacks. Extensive efforts were made to analyze link parameters that allowed us to put the autothermal reformer and the intermediate shift reactor into a single unit, eliminating the need for an intermediate heat exchanger. A new approach for system optimization, in order to maximize the integration of the catalytic processes, was based on a comprehensive investigation of gas flow in the integrated reactor, using a two dimensional simulation model.