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Researchers Exploring On-Board Exhaust Gas Reforming to Improve Combustion and Recover Waste Heat

Professor Stan Golunski, Deputy Director of the newly established Cardiff Catalysis Institute, in collaboration with engineers at Brunel and Birmingham Universities, is investigating the feasibility of an on-board exhaust gas reforming system to improve combustion and recover waste heat. In the exhaust gas fuel-reforming method, part of the engine exhaust gas reacts with small amounts of engine fuel in a mini-reactor fitted in the exhaust gas recirculation (EGR) loop to produce gaseous fuel named reformed EGR (REGR), which contains H2, CO, CH4, and CO2. The REGR gas is fed back to the engine inlet. (Earlier post.)

The Cardiff-Brunel-Birmingham team will study how the addition of these reformed mixtures affects engine combustion, performance and emissions with the Institute identifying stable catalysts that will perform the reforming reaction. Initially the research will focus on diesel engines but the potential of exhaust gas reforming to achieve benefits in gasoline engines will also be evaluated.

In a 2006 study, Golunski and Dr. Athanasios Tsolakis at the University of Birmingham examined the limited number of design parameters that can maximize the engine-reformer system efficiency while improving vehicle emissions, and concluded that further catalyst design was required to optimize such an exhaust-gas reformer system.

...we examine the limited number of design parameters that can allow us to maximize the engine-reformer system efficiency while improving vehicle emissions. In principle, this balance requires that the endothermic hydrogen-generating reactions (steam reforming and dry reforming) are promoted at the expense of the exothermic reactions (oxidation, water-gas shift and methanation). In practice, an oxidation function is necessary for generating heat to drive the endothermic reactions, particularly at low exhaust gas temperatures. Water-gas shift and methanation respond to changes in size and aspect ratio of the reformer, but the ideal configuration for suppressing these CO-consuming reactions does not favour the efficient endothermic reactions at all operating conditions. Our results imply that the optimum exhaust-gas reformer cannot be achieved through reactor engineering alone, but will require further catalyst design.

—Tsolakis and Golunski

Results from the new study could lead to new advances in engine design which can be used in conjunction with other technologies currently used to improve CO2 emissions, such as weight reduction of vehicles, start-stop fuelling, and the switch to hybrid and diesel cars.

The project is one of the first undertaken by the Cardiff Catalysis Institute, which is part of the University’s School of Chemistry. Officially launched on 13 October, the Institute aims to establish a center of excellence for catalysis within the UK that builds upon the current strengths in research at Cardiff.

Chemistry at Cardiff already has excellence in heterogeneous catalysis, homogeneous catalysis and biocatalysis. The aim is to bring these together within a single institute so that they can grow and provide the focal point for interdisciplinary interactions within Cardiff and externally with academia and industry.

—Professor Graham Hutchings, director of the Institute

Resources

  • P Leung, A Tsolakis, J Rodriguez-Fernandez, S Golunski (2010) Raising the fuel heating value and recovering exhaust heat by on-board oxidative reforming of bioethanol. Energy Environ. Sci., doi: 10.1039/b927199f

  • A Abu-Jrai, A Tsolakis, K Theinnoi, A Megaritis, SE Golunski (2008) Diesel exhaust-gas reforming for H2 addition to an aftertreatment unit. Chem. Eng. J. doi: 10.1016/j.cej.2007.12.028

  • A Tsolakis and SE Golunski (2006) Sensitivity of process efficiency to reaction routes in exhaust-gas reforming of diesel fuel. Chem. Eng. J. 117 doi: 10.1016/j.cej.2005.12.017

Comments

HarveyD

After 100+ years of venting away over 80% of the energy at the exhaust pipe and polluting the atmosphere, somebody will be looking at ways to recover part of the wastes energy. That's good news.

ejj

I can see using waste heat someway / somehow, but recirculating exhaust gas "which contains H2, CO, CH4, and CO2"? If this was beneficial, seems someone would have figured out how to exploit it decades ago.

Engineer-Poet

The exhaust gas doesn't usually contain much of those species other than CO2. Using exhaust gas and exhaust heat to crack fuel into such a mixture is a prospect that has been under investigation for some time; using jacket and exhaust heat to crack methanol to CO + H2 is an idea more than 20 years old.

Peter_XX

Combustion engines have an advantage over PEM fuel cells (PEFC) in this respect that the exhaust temperature is higher. PEFC powertrains do not have this improvement potential.

The combustion efficiency of a heavy-duty diesel engine can be in order of 99.8%. Thus, the potential to burn residual gases is in the order of 0.2% (somewhat higher on light-duty engines).

Dissociation/reforming of methanol or dimethyl ether (DME) have a greater potential than ethanol, gasoline or diesel fuels. Many problems remain and among them:
1) Practical and technical issues
2) Nobody is interested in methanol as an automotive fuel (maybe DME could be an option)

The use of gasoline and diesel in a reformer is so complicated that we are talking about a chemical factory, i.e. an almost similar story as for gasoline fuel cells (proven to be a bad idea). Chemical factories should be built on a concrete foundation, not on four wheels. However, it is good that someone tries so we can find out if is just could be possible…

Treehugger

Peter some 99.8% combustion generates soots that is where most of the potential for reforming is, not in the CO. But I agree that I have hard time to see this implemented on a car, though it is possible on truck and boats, there is already a company who do that by the way.

Peter_XX

Treehugger
If you have specific fuel consumption of 200 g/kWh, HC emissions of 0.1 g/kWh and soot emissions of 0.1 g/kWh (before catalyst and DPF in both cases) it equals a combustion efficiency of 99.9%. Some engines are even better than that. Many European engines are certified at particle levels <0.02 g/kWh without particle filter. I know what I am talking about! Obviously you do not...

HarveyD

Would this be beneficial for large engines used on ships, locomotives, tractors, trucks, buses etc?

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