Fuel cell plant design requires an appropriate integration of components, especially with the fuel processing unit. The integration of a steam reformer for methanol with a polymer electrolyte membrane (PEM) fuel cell plant is examined here. The integration considers the use of the fuel cell anode off gas (AOG) for combustion in order to supply the necessary heat for the reforming reaction. The whole fuel cell plant is considered with simple models for the components that allow sizing of the components and characterisation of their operating conditions. A reformer, based on a plate heat exchanger, is considered with catalytic combustion of the AOG and methanol to supply the required energy. A detailed model for a plate heat exchanger, which considers reactions and heat transfer is used to predict temperature profiles.