Modeling And Simulation Of Ammonia-based Hydrogen Production For PEMFCs

Hydrogen is the most potential energy with strategic value in this century, and fuel cell technology is an important way for hydrogen energy utilization. Therefore, the study on hydrogen production from ammonia decomposition for PEMFCs through mathematical modeling by gPROMS has practical significance. Ammonia-based hydrogen production for fuel cell application is comprised of ammonia decomposition, residual ammonia adsorption, hydrogen-nitrogen membrane separation and PEMFCs. The model of each operation unit was established to investigate its appropriate operating condition. A self-heated ammonia decomposition reactor with shell-and-tube configuration was designed as a compact fuel processor. In the co-current mode, the high concentration of ammonia corresponds with the high heat generation rate of hydrogen combustion, and the reactor is very efficient in terms of the high conversion. The fixed-bed adsorption of ammonia onto activated carbon fibers was simulated to determine the adsorption breakthrough time. The model of H2/N2 gaseous mixture separation in hollow fiber membranes which involves the concentration polarization phenomena was established. Hydrogen partial pressure difference is the driving force for the membrane separator. At the equilibrium state, hydrogen partial pressure on both sides of the membranes are the same. The electrochemical model for proton exchange membrane fuel cells (PEMFCs) was developed. The number of cells depends on the specific work condition. Additionally, a complete system including hydrogen recycling and heat integration was designed. In order to supply the energy for the whole system, part of the hydrogen was recycled to the reactor for combustion. The ammonia decomposition reaction conversion was close to 100%, and the total hydrogen recovery was 84.36%, and the power generation efficiency of proton exchange membrane fuel cells (N= 60) was 67.28%.