13.5 TECHNOLOGY

13.5 TECHNOLOGY

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TECHNOLOGY
High Efficiency Power Generation from Victorian Brown Coal at CSIRO
Dr Chris Munnings
Senior Research Scientist

Dr Sarb Giddey
Research Team Leader

by Dr Chris Munnings, Senior Research Scientist and Dr Sarb Giddey, Research Team Leader, CSIRO

Direct carbon fuel cells (DCFC) are a promising technology that offer the potential to generate power from coal at double the best current electric efficiencies (i.e. to 65%–70%), and half the CO2 emissions compared to today’s coal fired power plants.

The exhaust gas from the DCFC reactor is almost pure carbon dioxide, requiring no or minimal gas separation and processing for sequestration. Therefore, the energy and cost penalties to capture the CO2 will be significantly less than for other technologies. No other technology can offer such a high efficiency for power generation. The technology is at an early stage of development, but early indications show that it is best suited to low ash highly reactive fuels such as Victorian brown coal with untreated brown coal chars offering the highest power output of any fuel tested at CSIRO as part of its DCFC program.
Chart 1: DCFC with capture – a zero emission technology.

BCIA and CSIRO are currently working together, looking at how best to move this technology towards the market and what would be the most effective way of using brown coal. The project includes experimental work to investigate the optimum way to take advantage of brown coal’s high reactivity, catalytic ionic species, good electric conductivity and low ash content. The results of this study should lead to a greater understanding of the benefits and technical challenges in the development of DCFC for brown coal utilisation.

CSIRO has been developing direct carbon fuel cell technology since 2008, and has established state of the art facilities and collaborations with other institutes (Monash University, St Andrews University, Imperial College London, Australian Synchrotron and BCIA) to investigate the range of issues relating to the development of this technology, including fuel (coal) characterisation and preparation, fuel feed mechanisms, fabrication of scalable geometry of the cells, system design, DCFC reactors, operating and electrochemical diagnostic techniques, and post-mortem analysis (in-house and at Australian Synchrotron) for materials development.

The support we have received from BCIA in this project is allowing us to move from the very early fundamental investigations into the use of brown coal via a previously funded collaborative partnership between Monash and CSIRO (funded by BCIA through a PhD scholarship) to more applied work utilising tubular fuel cells and modified reactors capable of simulating both direct reaction and gasification processes.

Tubular fuel cells can be used within chemical reactors and are employed to investigate the performance of the scaled up version of the direct carbon fuel cell in 'direct contact of carbon (packed bed of carbon)’ and in 'carbon gasification‘ modes. This allows for the investigation of more system-related phenomena such as current collection and gas distribution. These factors can have a dramatic effect on performance with optimisation of electrode materials and trialling of different modes of operation increasing the power density by almost a factor of 2 during this project.

Fuel cells can be operated in several different modes. From early studies on synthetic carbon we have found that in the gasification mode of operation, where carbon was not in direct contact with the anode, the power densities were around 20% lower than direct contact (packed bed) mode. The higher performance in direct contact DCFC seems to be due to the better current collection in the packed bed of carbon compared to gasification only mode.

The next steps for our work on DCFC and Victorian brown coal are to trial our new setup on brown coal char, to tune the electrode for higher performance and to operate for longer periods. This work could conceivably push CSIRO’s DCFC technology well beyond the 100 mW/cm
2 limit seen by many as the minimum commercial operating power density of a fuel cell. If this can be achieved on a realistic fuel composition for a significant operating time, it would push DCFC from the shadows of fundamental research into the more applied R&D mainstream.
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Chart 2: Power density obtained from a scalable DCFC.




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