INVESTIGADORES
AGUIRRE Pio Antonio
artículos
Título:
Energy efficiency analysis of an integrated glycerin processor for PEM fuel cells: Comparison with an ethanol-based system
Autor/es:
DIEGO G. OLIVA; JAVIER A FRANCESCONI; MIGUEL C MUSSATI; AGUIRRE PIO
Revista:
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Año: 2010 vol. 35 p. 709 - 724
ISSN:
0360-3199
Resumen:
The aim of this work is to analyze energetically the use of glycerin as the primary hydrogen
source to operate a proton exchange membrane fuel cell. A glycerin processor system
based on its steam reforming is described departing from a previous process model
developed for ethanol processing. Since about 10% w/w of glycerin is produced as
a byproduct when vegetable oils are converted into biodiesel, and due to the later is
increasing its production abruptly, a large glycerin excess is expected to oversaturate the
market. The reformed stream contains mainly H2 but also CO, CO2, H2O and CH4. As CO is
a poison for PEM fuel cell type, a stream purification step is previously required. The
purification subsystem consists of two water gas shift reactors and a CO preferential
oxidation reactor to reduce the CO levels below 10 ppm. The reforming process is governed
by endothermic reactions, requiring thus energy to proceed. Depending on the system
operation point, the energy requirements can be fulfilled by burning an extra glycerin
amount (to be determined), which is the minimal that meets the energy requirements.
In addition a self-sufficient operation region can be distinguished. In this context, the
water/glycerin molar ratio, the glycerin steam reformer temperature, the system pressure,
and the extra glycerin amount to be burned (if necessary) are the main decision variables
subject to analysis. Process variables are calculated simultaneously, updating the
composite curves at each iteration to obtain the best possible energy integration of the
process. The highest net system efficiency value computed is 38.56% based on the lower
heating value, and 34.71% based on the higher heating value. These efficiency values
correspond to a pressure of 2 atm, a water/glycerin molar ratio of 5, a glycerin steam
reformer temperature of 953 K, and an extra glycerin amount burned of 0.27 mol h1. Based
on the main process variables, suitable system operation zones are identified. As in
practice, most PEM fuel cells operate at 3 atm, optimal variable values obtained at this
condition are also reported. Finally, some results and aspects on the system performance
of both glycerin and ethanol processors operated at 3 atm are compared and discussed.2 but also CO, CO2, H2O and CH4. As CO is
a poison for PEM fuel cell type, a stream purification step is previously required. The
purification subsystem consists of two water gas shift reactors and a CO preferential
oxidation reactor to reduce the CO levels below 10 ppm. The reforming process is governed
by endothermic reactions, requiring thus energy to proceed. Depending on the system
operation point, the energy requirements can be fulfilled by burning an extra glycerin
amount (to be determined), which is the minimal that meets the energy requirements.
In addition a self-sufficient operation region can be distinguished. In this context, the
water/glycerin molar ratio, the glycerin steam reformer temperature, the system pressure,
and the extra glycerin amount to be burned (if necessary) are the main decision variables
subject to analysis. Process variables are calculated simultaneously, updating the
composite curves at each iteration to obtain the best possible energy integration of the
process. The highest net system efficiency value computed is 38.56% based on the lower
heating value, and 34.71% based on the higher heating value. These efficiency values
correspond to a pressure of 2 atm, a water/glycerin molar ratio of 5, a glycerin steam
reformer temperature of 953 K, and an extra glycerin amount burned of 0.27 mol h1. Based
on the main process variables, suitable system operation zones are identified. As in
practice, most PEM fuel cells operate at 3 atm, optimal variable values obtained at this
condition are also reported. Finally, some results and aspects on the system performance
of both glycerin and ethanol processors operated at 3 atm are compared and discussed.1. Based
on the main process variables, suitable system operation zones are identified. As in
practice, most PEM fuel cells operate at 3 atm, optimal variable values obtained at this
condition are also reported. Finally, some results and aspects on the system performance
of both glycerin and ethanol processors operated at 3 atm are compared and discussed.