Simulation of a 2 MW PEM Fuel Cell Plant for Hydrogen Recovery from Chlor-Alkali Industry

Abstract

Some chemical processes, like the chlor-alkali production, generate significant amount of hydrogen as byproduct whose recovery within the chemical plant is not always possible. An efficient and attractive use of hydrogen is obtained installing a PEM fuel cell-based cogeneration unit, whose electricity and heat production covers part of plant consumptions. Practical application of this concept requires scaling up the fuel cell plant up to the multi-MW scale, an ongoing process with many open challenges where the development of dedicated modeling tools allows evaluating the plant expected performances and optimizing its operational strategies. This work presents the results of a the simulation activity modeling of an innovative 2 MW PEM fuel cell power plant, developed within the European project DEMCOPEM-2MW. Simulations are performed with ASPEN Plus®, including a specifically developed lumped model for the stacks in order to investigate their behavior as function of inlet streams conditions and of power set point. The BOP is modeled with particular attention to component expected operating conditions, efficiency, auxiliary consumption, pressure drops. The model is calibrated and validated on data from PEM stacks operated by Nedstack and MTSA in previous installations. Stacks model performs lumped energy and mass balances according to regressed polarization curves; cells decay is modeled through simplified assumptions aiming at evidencing the impact on auxiliaries operation and on global efficiency. Comparison with a different arrangement where excess hydrogen exiting the fuel cell anode is oxidized in a combustor, instead of being recirculated to the fuel cell, is also set up evidencing the possibility to increase the heat to electricity ratio and allow high temperature heat production. The model also allows assessing and optimizing the plant operational strategies (e.g. minimizing the power production and efficiency losses vs. lifetime), evaluating the deviations of real plant behavior from theoretical conditions.