(155e) PEMFC System Using Metallic Hydride Cycles to Purify the Hydrogen
Energy production trough hydrogen utilization has gained attention in the last decades. Reformer reactors are used to produce hydrogen rich streams departing from hydrocarbons and alcohols. The specifications of hydrogen needed depend on the device used to produce energy. Hydrogen containing low CO concentrations is required for proton exchange membrane fuel cells (PEMFC). Different purification processes were considered to achieve this aim. This work presents a system involving a reforming process and a PEMFC device coupled to pressure swing absorption (PSAb) purification reactor. Then, the PEMFC system has the following components: reformer reactor, PSAb reactor, PEMFC, heat exchangers, auxiliary units and post combustion system.
The study case used in this work considers ethanol as a fuel. A steam reformer reactor is adopted. So, the inputs at reformer reactor are water and ethanol in an operative molar relation to be optimized. The energy necessary in the reforming reactor is provided by a post combustion system. The output stream in this reactor contains water, carbon oxides and hydrogen. This stream feeds the PSAb reactor. This reactor has solid hydride material that absorbs the hydrogen and allows the impurities separation via venting. Here two PSAb reactors working in parallel are proposed to give a constant flux of pure hydrogen to the PEMFC. A cyclic scheduling of PSAb reactors is presented. The three steps involved in each reactor are: absorption, venting and desorption. The venting impurities are burn in the post combustion system. The PEMFC device produces the usable energy of the system and exhaust gases. These gases are also used by the post combustion system. This system is used to close the energy balance of the entire system.
A mathematical model of energy production system via PEMFC is developed in GAMS. The model calculates and optimizes the efficiency of the system. This allows gaining insight about the optimal values of the operative variables in each device of the system.