Abstract
Fuel cells (FCs) are used in co-generation plants as an environmentally benign and cost effective alternative for the production of heat and electricity. Currently hydrogen is produced via methane steam reforming followed by a Water Gas Shift reactor where CO is converted to CO2 and then is fed to a Pressure Swing Adsorption (PSA) process for purification. PSA systems are complex to run and energy intensive and therefore the use of other separation technologies would be attractive.
Compared to normal Polymer Electrolyte Membrane FCs (PEM FC), HT-PEM FC are able to withstand lower H2 purity in the feed and therefore they allow the investigation of less energy intensive and complex separation technologies after the water gas shift reactor. One promising option, is a membrane process using CO2-selective membranes and in particular Facilitated Transport Membranes (FTMs). FTMs show enhanced CO2 separation performances and selectivity compared to conventional solution-diffusion membranes due to the facilitation mechanism; the fixed carriers present in the membrane, typically amine groups, react with CO2 in the presence of water creating an additional specific pathway for the transport of carbon dioxide. The efficiency of the separation is therefore heavily affected not only by the intrinsic properties of the material but also by the management of water in the membrane module and by the operating conditions.
The integration of FTMs with HT-PEM FCs is investigated in detail in order to establish the effect of the membrane characteristics on the efficiency of the HT-PEM FC. The influence of various materials and design parameters is evaluated including effective permeance, water content, sweep configuration and operating temperature and pressure. The results are compared to the use of Pd-based H2-selective membranes in the process that has been investigated in the literature.
Compared to normal Polymer Electrolyte Membrane FCs (PEM FC), HT-PEM FC are able to withstand lower H2 purity in the feed and therefore they allow the investigation of less energy intensive and complex separation technologies after the water gas shift reactor. One promising option, is a membrane process using CO2-selective membranes and in particular Facilitated Transport Membranes (FTMs). FTMs show enhanced CO2 separation performances and selectivity compared to conventional solution-diffusion membranes due to the facilitation mechanism; the fixed carriers present in the membrane, typically amine groups, react with CO2 in the presence of water creating an additional specific pathway for the transport of carbon dioxide. The efficiency of the separation is therefore heavily affected not only by the intrinsic properties of the material but also by the management of water in the membrane module and by the operating conditions.
The integration of FTMs with HT-PEM FCs is investigated in detail in order to establish the effect of the membrane characteristics on the efficiency of the HT-PEM FC. The influence of various materials and design parameters is evaluated including effective permeance, water content, sweep configuration and operating temperature and pressure. The results are compared to the use of Pd-based H2-selective membranes in the process that has been investigated in the literature.