5 KW_E + 5 KW_T PEM-FC GENERATOR FROM BIOETHANOL: FUEL PROCESSOR AND DEVELOPMENT OF NEW REFORMING CATALYSTS

摘要

A power unit constituted by a reformer, a H_2 purification section and a fuel cell is being tested c/o the Dept. of Physical Chemistry and Electrochemistry of Universita degli Studi di Milano, on the basis of a collaboration with Helbio S.A. Hydrogen and Energy Production Systems (supplier of the unit) and some sponsors (Linea Energia S.p.A., Parco Tecnologico Padano and Provincia di Lodi). The system size allows to cogenerate 5 kW_e (a.c.) + 5 kW_t (hot water at 65°C) as peak output. Bioethanol, obtainable by different non-food competitive biomass is transformed into syngas by a pre-reforming and a reforming stage and the reformate is purified from CO to a concentration below 20 ppmv, suitable to feed the proton exchange membrane fuel cells (PEMFC) stack integrated in the fuel processor. This result is achieved by feeding the reformate to two water gas shift reactors, connected in series and operating at high and low temperature, respectively. CO concentration in the outcoming gas is ca. 0.7 vol% and the final CO removal to meet the specifications is accomplished by two methanation stages in series. The second methanation step acts as a guard since ca. 15 ppmv of CO are obtained even after the first reactor. The purified H_2 is suitable for feeding a 5 kW_e PEMFC stack, which should have an expected overall efficiency higher than 80% (including thermal output). The main goal of the present project is to check system performance under different operating conditions, to verify the effectiveness of the proposed technology and to suggest adequate improvements. In particular, the system will be tested under different load, to check for the readyness of response. Another point will be the effect of bioethanol origin, purity and concentration, so to open the way to separation processes different from distillation. Due to the demonstrative character of the project the main part of the experimentation focuses on the accumulation of a suitable amount of hours-on-stream to validate the system feasibility. A parallel investigation is active on the development of alternative nanostructured catalysts for the present application. In particular, Ni, Co and Cu-based catalysts, supported over La_2O_3, TiO_2 and SiO_2 were tested at 500, 625 and 750°C. At the moment no perfect candidate has been found to operate the steam reforming at the lowest temperature, due to unsatisfactory material balances and by-products formation at 500°C with most catalysts. Good H_2 productivity, with 100% C balance has been achieved at higher temperature (≥ 625°C).