COGENERATION OF THERMAL AND ELECTRIC POWER FROM RENEWABLE SOURCES

This project deals with a different use of ethanol deriving from biomass. The aim is to produce hydrogen starting from 2nd generation bioethanol as raw material. H2 is then purified and fed to a PEM fuel-cell. The latter co-generates electrical and thermal energy with a 5kWelectric+ 5kWthermal power size, suitable for de-localized energy production. The goals of this work are different: efficient H2 production by bioethanol steam reforming (SR), H2 purification by high and low temperature water gas shift (HTWGS+LTWGS) and methanation of residue CO (<20ppmv), check of the overall plant efficiency and performance under widely different operating and load conditions. This project is divided in two steps. The former consists in efficiency tests on the above mentioned semi-commercial device (GH2-5000 Energy System provided by Helbio S.A) composed by a PEM fuel-cell integrated in a steam reforming + H2 purification system. The latter step focuses on catalytic tests on new materials in order to find innovative catalysts for the SR of bioethanol. In particular, we aim at finding catalysts active at lowest reaction temperature, to promote the WGS reaction even in the SR step and to lower the energy input of the endothermic SR reaction, due to the exothermicity of the WGS one. A series of Ni catalyst, differently supported, were synthesised and characterised. Three different series of Ni-based catalysts for the steam reforming reaction were synthesised by two different procedures. Al2O3, TiO2 and La2O3 were chosen as supports and the Ni loading was 5-10-15 wt% for each set of samples. Ni supported on Al2O3 was chosen at first, because it is the most common SR catalyst commercially available and it was assumed as reference material. The biggest problem when using alumina as support was coke formation during the SR reaction, depressing selectivity and deactivating the catalyst. For this reason binary supports, such as Al2O3/La2O3, are used to decrease support acidity . In the present work catalysts directly supported on pure La2O3 were also prepared. At last TiO2 - supported samples, rather new for this application, were prepared to achieve lower acidity than alumina, coupled with interesting redox properties of the support, which could enhance surface cleaning. The selected supports were prepared in nano-powder form by flame spray pyrolysis (FP,) and then Ni was added in proper amount by impregnation from a Ni(NO3)2 · 6H2O aqueous solution. A parallel, completely new, preparation procedure was developed by directly adding Ni during the FP synthesis. Some of the catalysts prepared were included in a project financed by Regione Lombardia in collaboration with the Universities of Venice (UniVE) and Genoa (UniGE). This project was focused on catalytic materials for both ethanol (ESR) and glycerol (GSR) steam reforming. Catalysts with different active phases (Ni, Co, Cu) and different supports (TiO2, SiO2, ZrO2) were synthesised. Different strategies have been adopted for the preparation of the samples (UniMI-UniVe), namely flame pyrolysis and metal impregnation over traditionally prepared supports. All the catalysts were characterised by atomic absorption, XPS, XRD, O2-chemisorption, FT-IR,TPR-TPO (UniVE, UniGE, UniMI). Finally, some tests were carried out on the integrated 5 kW plant to set up the analytical procedure. The first tests revealed a number of electrical and set up problems, which were partly solved. Preliminary experiments allowed to monitor the trend of CO concentration , confirming the H2 purity level required to feed the PEMFC (10 ppmv in the reformate). Currently the system was returned to the supplier to allow interfacing with a new type of HT-PEMFC that operates at 160° C and is therefore able to withstand a level of CO equal to 2 vol%.