Enhanced hydrogen production from biomass when coupled with carbon dioxide capture using CaO
Sustainable process-product development & green chemistry
Sustainable & Clean Technologies - IIb: Energy Production (T1-5b)
Keywords: biomass, calcium oxide, carbon dioxide capture, gasification, hydrogen
The steam gasification of biomass and non-recyclable combustible wastes, coupled with in situ carbon dioxide (CO2) capture is a promising process for the production of hydrogen (H2). The fundamental idea is to selectively produce a H2-rich gas via the thermochemical conversion of biomass with steam. The H2 output is maximised with the manipulation of the equilibrium composition of the product gas, by removing CO2 as soon as it is formed. Calcium oxide (CaO) is well known to be an effective CO2 sorbent, capable of scavenging CO2 to very low concentrations, as well as being cheap and abundant [1]. The production of a highly pure stream of CO2, when the sorbent is regenerated, is a significant advantage of this process.
Recent research efforts based on this general concept of an integrated H2 production process, coupled with capture and storage of CO2, have focused on the utilisation of coal in the context of ‘zero emission coal’ power stations [2]. However, there are significant advantages in using biomass fuels, which represent a renewable, diverse and potentially ‘carbon neutral’ resource for the production of H2. Furthermore, there are inherent advantages in utilising biomass fuels due to the different chemistry of biomass gasification, when compared with coal. Fundamental research of the steam gasification of biomass fuels, in the presence of CaO, is needed in order to realise such benefits and to obtain data necessary for the design of novel biomass conversion reactors.
Pyrolysis and gasification experiments were carried out using a modified thermogravimetric analyser, coupled with a mass spectrometer (TGA-MS). Pure cellulose was used as a model biomass fuel. A comparison of the rate of weight loss with the mass spectrometric data was used to elucidate the different mechanistic pathways in this complex reaction process, when CaO was present. In addition the significance of the temperature, heating rate and residence time were investigated, providing critical insights for the design of biomass conversion reactors.
[1] Abanades JC, Rubin ES, Anthony EJ, Sorbent cost and performance in CO2 capture systems. Industrial and Engineering Chemistry Research 2004; 43: 3462-3466.
[2] The United States Department of Energy, FutureGen initiative to develop an integrated H2 production and CO2 sequestration process based on coal gasification, viewed on the 10th of October 2006 <http://www.fossil.energy.gov/programs/powersystems/futuregen/>
Nicholas Florin*
Laboratory for Sustainable Technology,
School of Chemical and Biomolecular Engineering,
University of Sydney, NSW 2006, AUSTRALIA
Phone: +61 2 9036 6244
Fax: +61 2 9351 2854
E-mail: nflorin@chem.eng.usyd.edu.au
Dr. Andrew Harris
Phone: +61 2 9351 2926
Fax: +61 2 9351 2854
E-mail:aharris@chem.eng.usyd.edu.au
* Author for all correspondence.
Presented Wednesday 19, 11:20 to 11:40, in session Sustainable & Clean Technologies - IIb: Energy Production (T1-5b).
