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MCFC Co-Generation of Power and Hydrogen for Vehicle Fueling from Biogas

Researchers at the Politecnico di Torino, Italy, have investigated the feasibility of a biogas-fueled 250 kW power generation system based on molten carbonate fuel cells (MCFCs) with an efficiency higher than 50%, integrated with a biogas fuel processor for decentralized methane and hydrogen production, especially tailored for a fueling station that is capable of supplying about 20-100 vehicles per day.

Bensaid
Plant process flow diagram. Credit: ACS, Bensaid et al. Click to enlarge.

The hydrogen production should correspond to a minimum production of 750 N m3/day or about 0.4 mol/s pure hydrogen (99.99%). A paper on their work was published online 19 February in the ACS journal Energy & Fuels.

Because MCFCs are highly exothermic and their working temperatures (650 °C) are compatible to steam reforming, the syngas is produced directly inside the vessel containing the fuel cell stack, with the reaction being thermally self-sustained. Moreover, the high-temperature flue gases from the MCFC are expanded in a turbine, thus increasing the total power generated.

Hydrogen is produced through a pressure swing adsorption system, whose feed can be from either the MCFC anode outlet or a split of the reformate before the anode inlet. The overall net power efficiency of the system is similar for both configurations: 56% and 55%, respectively.

A specific issue to be addressed in future technical and economical feasibility assessments of the landfill biogas-based power (and hydrogen) production with MCFCs is the gas purification. Biogas from landfills is a powerful renewable fuel that can be used as a feedstock of fuel cell systems, which are highly efficient and ultra-low-emission power generation systems; however, it has to be cleaned up by removing the sulfur and halogenated species, among others, which are poisons for both fuel cells and reforming catalysts.

At present, the levels of sulfur and halogens that allow for safe operation of the fuel cells are below 0.1 ppm. In addition, the presence of water in the gaseous fuel dramatically reduces the sorbent uptake capacity. All of these features might hinder the widespread exploitation of biogas within this field. This requires a specific research activity on multi-stage sorbents, which is presently being carried out within our group.

—Bensaid et al.

Resources

  • Samir Bensaid, Nunzio Russo and Debora Fino (2010) Power and Hydrogen Co-generation from Biogas. Energy Fuels, Article ASAP doi: 10.1021/ef901260k

Comments

SJC

United Technology ONSI units are MCFCs. They produce lots of heat which could be used in ethanol plants or else where. They are mostly used in banks and hospitals where you need uninterrupted power. They use the heat in a CHP configuration for heating and cooling.

There is a new lower cost SOFC like fuel cell from Bloom Energy that was reported on 60 Minutes this last Sunday.

http://www.cbsnews.com/stories/2010/02/18/60minutes/main6221135.shtml?tag=currentVideoInfo;segmentUtilities

It is lower cost because the electrode layers are coated on instead of vacuum deposited. This could be a real good unit for home use. Put it in the garage and replace the furnace and hot water heater. It is like getting free electricity.
It is also reversible where it can generate hydrogen, which was the original design at NASA.

When generating hydrogen it is endothermic, so it could provide cooling during those times. If it is a fuel cell it is exothermic and runs at more than 1000F. This is high enough temperature to run a two stage absorption chiller to cool your home, create electricity and heat all your water.

sulleny

SJC,

I saw the segment and was impressed to see the number of units in active beta stages. If I recall the guy from Google said they were generating about 15% of their Mountain View energy from the Bloom stacks.

The breakthrough for Bloom is their stack coatings and they're able to burn any kind of gaseous fuel. I imagine that most of the test units are running NG. And if what you indicate is the case a CCHP would produce electricity, hot water and cooling - all from a stream of NG or perhaps biomass syngas one day.

We have been agitating for this for a LONG while. It seems to be nearing reality if the costs can be kept reasonable and the stacks MTBF is long enough. More good stuff happening this decade.

Engineer-Poet

Auto-reforming fuel cells like MCFCs and SOFCs have long been able to burn any kind of gaseous fuel.

The interesting twist in this is the use of FC waste heat to reform fuel to hydrogen for other uses.  That's downright clever.

SJC

I could see using the heat to gasify the biomass to syngas. SOFCs use both the CO and H2 as fuel. Use a gas turbine as an afterburner and then combine cycle with a rankine and you could have something.

Engineer-Poet

SJC, do you mean something like this?

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