Leeds Researchers Working on More Energy-Efficient Steam Reforming Process for Hydrogen from Waste Materials

13 July 2009

Researchers at the University of Leeds (UK) investigating a more energy-efficient steam-reforming process for hydrogen production from waste materials, including vegetable oil and the glycerol by-product from biodiesel production (earlier post), recently reported optimal H₂ production from the steam reforming of glycerol at 500 °C, with in situ CO₂ removal using calcined dolomite as the sorbent. The results appeared in the journal Bioresource Technology.

The system being developed at Leeds—Unmixed and Sorption-Enhanced Steam Reforming—relies on the cyclic oxidation of a bed of nickel-based material and on the simultaneous regeneration of a CO₂-sorbent under airflow to provide the heat necessary for the steam reforming reaction. The latter occurs subsequently under a fuel/steam flow while the airflow is interrupted.

The novelty of the approach is the use of in-situ removal of CO₂ and ex-situ regeneration of CO₂ adsorbent, thus enabling a continuous operation of the reactor, direct delivery of hydrogen at the reactor pressure, the use of relatively low capacity adsorbent, introduction of more physical heat to the reactor, and intensification of heat transfer within the reactor.

The effluent gas of the fuel/steam step is much higher in hydrogen than the single reactor equivalent conventional process, and the oxidized catalyst is regenerated by reduction from exposure to the fuel. Because the carbon produced during the steam reforming step is subsequently burned under the airflow, the process is not sensitive to the gradual loss of conversion efficiency exhibited by the conventional process.

Furthermore, in the unmixed steam reforming process, sulfur in the fuel is claimed to also undergo oxidation under the airflow rather than irreversibly poisoning the reforming catalyst.

When using a suitable CO₂-sorbent in the reformer, the dry hydrogen content in the reformate gas reaches above 80% (90+% when using methane fuel). In this case, most of the produced CO₂ and the N₂ from the airflow effluent leave the reactor separately to the H₂-rich reformate gas, and can potentially be easily filtered and stored.

The work, led by Dr. Valerie DuPont, is based on an earlier Engineering and Physical Sciences Research Council (EPSRC)-funded project showing the sequence via which the various reactions involved in the cycle proceeded. In that project, they found clear evidence of the insensitivity of the process to coking. The improved process under development thus opens up opportunities for the use of a whole range of fuels with coking tendencies and/or sulphur content, such as the combustible liquid mixtures derived from biomass or specific industrial / transportation waste.

The Leeds researchers, led by Dr. Valerie DuPont, claim that this process can be economical at small scale, unlike the conventional steam reforming process, and could thus be used in distributed power generation.

It’s becoming increasingly necessary for scientists devising new technologies to limit the amount of carbon dioxide they release. This project takes us one step closer to these goals—once we have technologies that enable us to produce hydrogen sustainably, the infrastructure to support its use will grow.

We firmly believe that these advanced steam reforming processes have great potential for helping to build the hydrogen economy. Our primary focus now is to ensure the materials we rely on—both to catalyze the desired reaction and to capture the carbon dioxide—can be used over and over again without losing their efficacy

—Valerie DuPont

A grant of more than £400,000 (US$645,000) has been awarded to the University by the EPSRC within a consortium of 12 institutions known as SUPERGEN Sustainable Hydrogen Delivery.

EPSRC and SUPERGEN. The Engineering and Physical Sciences Research Council (EPSRC) is the UK’s main agency for funding research in engineering and the physical sciences. The EPSRC invests more than £800 million a year in research and postgraduate training.

The SUPERGEN initiative is the primary delivery mechanism for sustainable energy research funded by EPSRC as part of the Research Councils’ Energy Programme.

In 2011 the current round of SUPERGEN will begin to come to an end, with the final projects ending in 2013. EPSRC is reviewing the strengths and weaknesses of the current structure, and is consulting with the academic and user community to elicit views on possible structures that could take SUPERGEN to the next phase and to assess the research themes that should be covered by SUPERGEN in the future.

Accordingly, EPSRC is holding two meetings to discuss the future shape and direction of the SUPERGEN program: 27 August 2009 in Manchester and 8 September 2009 in London.

Resources

• EP/D078199/1: Unmixed Steam Reforming of Liquid Fuels From Biomass and Waste for Hydrogen Production

• Binlin Dou, Valerie Dupont, Gavin Rickett, Neil Blakeman, Paul T. Williams, Haisheng Chen, Yulong Ding and Mojtaba Ghadiri (2009) Hydrogen production by sorption-enhanced steam reforming of glycerol. Bioresource Technology 100 (14) Pages 3540-3547 doi: 10.1016/j.biortech.2009.02.036

• EP/F027389/1: Hydrogen generation from biomass derived glycerol using sorption enhanced reaction processes

• GR/R50677/01: Unmixed Reforming of Vegetable Oil for Hydrogen Production