Dynamic Modeling and Control Issues on a Methanol Reforming Unit for Hydrogen Production and Use in a PEM Fuel Cell

摘要

The presented research work focuses on the mathematical description and control analysis of an integrated power unit that uses hydrogen produced by methanol autothermal reforming. The unit consists of a reformer reactor where methanol, air and water are co-fed to produce a hydrogen rich stream through a series of reactions. The hydrogen main stream is fed to a preferential oxidation reactor (PROX) for the reduction of CO at levels below 50ppm with the use of air. In the end, the PROX outlet stream enters the anode of a PEM fuel cell where power production takes places to serve a load demand. The operation of the two reactors is described by a combination of partial differential equations (mass and energy balances) and non-linear equations (kinetic expressions of the reactions), while the power production in the fuel cell is based on the inlet hydrogen flow and on operational characteristics. A simple case sceanrio is employed when a step change on methanol flowrate is imposed. Main target is to identify and analyze the changes occuring in the main variables of concern (H2, CO and temperature levels) that affect the overall system operation. Based on the results, an insight on the challenging control scheme will be applied in order to identify possible ways of setting up a reliable and robust control structure according to the developed mathematical model.