Details

Title:

Hydrogen Generation from the Pyrolysis-Catalytic Gasification of Solid Wastes and Biomass Using Different Nickel-based Catalysts

Author(s):

Blanco, P.H., Efika, C., Wu, C., Onwudili, J.A., Williams, P.T.

Document(s):

Abstract:

The potential of hydrogen as a fuel source has been increasing as it involves clean combustion compared with the greenhouse gases emissions from the combustion of fossil fuels; additionally hydrogen can be used as fuel in fuel cells or hydrogen powered turbines. The current hydrogen production processes involve the use of fossil fuels by natural gas steam reforming and partial oxidation of coal or heavy hydrocarbons; however there have been investigations into more sustainable sources for hydrogen such as solid wastes. The combination of thermochemical processes such as pyrolysis and catalytic gasification have been suggested as a convenient route to obtain a gas mixture rich in hydrogen. Nickel based catalysts have been proven to be effective to increase the hydrogen content in the syngas during the processing of solid wastes; however their performance is highly influenced by catalyst properties such as the type of support, surface area, metal dispersion, among others; for this reason the preparation method of the selected catalysts is a crucial factor. In this work a two-stage fixed-bed reactor has been used to promote tar cracking in a downdraft gasifier, using municipal solid waste in the form of refuse derived fuel (RDF) as raw material. The pyrolysis of RDF was carried out at 600 °C, and then the pyrolysis gases were catalytically reformed within the second gasification stage at 800 °C. Investigation of the two-stage pyrolysis-gasification system was extended to a continuous operation process using a first stage screw kiln pyrolysis reactor (500 °C) with a second stage fixed bed catalytic steam reforming (760 °C) for the gasification of biomass in the form of wood waste. The reactor design combines the high heat and mass transfer characteristics of a screw-kiln reactor and the high gas-solid interaction (for catalysis) of a fixed bed reactor. A series of Ni-based catalysts were prepared by different methods and using different nickel loadings to determine their effectiveness in converting the RDF and biomass into syngas, particularly hydrogen. The produced gases were analysed using gas chromatography while the fresh and reacted catalyst were characterised by scanning electron microscopy (SEM), thermogravimetric analysis (TPO-TGA), transmission electron microscopy with energy dispersive X-ray and X-ray photoelectron spectroscopy. The experimental results showed that in the presence of NiO/SiO2 catalysts there was a significant increase in the yield of syngas, particularly hydrogen concentration for both types of reactor. Higher gas yields of about 56wt.% and 49.8wt.% were attained for RDF and wood respectively and hydrogen yield was increased in the presence of the catalysts. Different types of carbon deposited over the reacted catalysts were identified by thermogravimetry analysis as amorphous and filamentous carbon.

Keywords:

biomass, gasification, hydrogen, pyrolysis, waste, catalyst

Topic:

R&D on Biomass Conversion Technologies for Heating, Electricity and Chemicals

Subtopic:

Gasification for synthesis gas production

Event:

21st European Biomass Conference and Exhibition

Session:

2AO.4.1

Pages:

425 - 429

ISBN:

978-88-89407-53-0

Paper DOI:

10.5071/21stEUBCE2013-2AO.4.1

Price:

FREE