Ethanol Fuel Processors

Very few fuel processors that utilise ethanol as a fuel have been described in the open literature. However, ethanol is of course very attractive from an environmental and sustainability point of view, because its production and consumption cycle may well be performed with reduced, or even zero, net carbon dioxide emissions. 

MitdieD et cd., at the company Arthur D. little, described early projections for an ethanol fuel processor based upon partial oxidation [475]. The efficiency of the fuel processor was calculated to be 80% and power densities of 1.44 LkW and 1.74kg kW were achieved. 

Natural gas reforming plays a dominant role especially in the domestic sector 75% of the fuel cells existing today that are in the power region below 10 kW are fuelled by natural gas [16]. 

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The removal of small amounts of carbon monoxide present in reformate of hydrocarbon and ethanol fuel processors downstream the WGS reactor is commonly performed by the preferential oxidation with air (PrOx) ... 

A concept for a methanol (or ethanol) fuel processor based upon steam reforming and membrane separation was presented by Gepert et td. [400]. As shown in Figure 5.33, the alcohol/water mixture was evaporated and converted by steam reforming in a fixed-bed catalyst, into which palladium capillary membranes were inserted. The retenate then entered the combustion zone, which was positioned concentrically around the reformer bed at the reactor wall. Air was fed into the combustion zone and residual hydrogen, carbon monoxide and unconverted methanol combusted therein. The sealing of the membranes at the reactor top was an issue solved by air-cooled elastomers. 

Figure 5.49 Effect of the S/C ratio (here expressed as R = S/2C) on the hydrogen yield of an ethanol fuel processor at different operating temperatures, Tref, of the reformer operating temperature of water-gas shift 200°C selectivity of preferential oxidation reaction 90% [440].

Kolb, G., Men, Y., Schelhaas, K.P., Tiemann, D., Zapf, R., and Wilhelm, J. (2010) Development work on a microstructvu-ed 50kW ethanol fuel processor for a small-scale stationary hydrogen supply system. Ind. Eng. Chem. Res., 50 (5), 2554-2561. 

For the calculation of WTW energy requirements and GHG emissions we have made the simplification that the fuel consumption of a vehicle fuelled with ethanol (e.g., E85) is the same as that of a vehicle fuelled with pure gasoline. Methanol is used in fuel cell vehicles with on-board fuel processors. Table 7.2 shows the properties of different transportation fuels. 

Hydrogen is a secondary fuel and, like electricity, is an energy carrier. It is the most electroactive fuel for fuel cells operating at low and intermediate temperatures. Methanol and ethanol are the most electroactive alcohol fuels, and, when they are electro-oxidized directly at the fuel cell anode (instead of being transformed in a hydrogen-rich gas in a fuel processor), the fuel cell is called a DAFC either a DMFC (with methanol) or a DEFC (with ethanol). 

The DEFC transforms directly the Gibbs energy of combustion of ethanol into electricity, without a fuel processor. This greatly simplifies the system, reducing its volume and cost [22, 23]. The important development of DEFCs is due to the use of a proton exchange membrane as electrolyte, instead of a liquid add electrolyte, as done previously. 

Nuvera will design, build, test, and deliver a 15 kilowatt electrical (kWe ) direct current (DC) fuel cell power module that will be specifically designed for stationary power operation using ethanol as a primary fuel. Two PEM fuel cell stacks in parallel will produce 250 amps and 60 volts at rated power. The power module will consist of a fuel processor, carbon monoxide (CO) clean-up, fuel cell, air, fuel, water, and anode exhaust gas management subsystems. A state-of-the-art control system will interface with the power system controller and will control the fuel cell power module under start-up, steady-state, transient, and shutdown operation. Temperature, pressure, and flow sensors will be incorporated in the power module to monitor and control the key system variables under these various operating modes. The power module subsystem will be tested at Nuvera and subsequently be delivered to the Williams Bio-Energy Pekin, Illinois site. 

Nuvera is working with the Department of Energy to develop efficient, low emission, on-board multi-fuel processors for the transportation application. The fuels include gasoline, methanol, ethanol, and natural gas. 

Fuel processor for 5 kW PEM fuel cell unit Combined-cycle power generation Production of low-sulfur diesel fuel Waste-fuel upgrading to acetone and isopropanol Conversion of cheese whey (solid waste) to lactic acid Ethanol for gasoline from com symp... 

Lopez, E., Divins, N.J. and Llorca, J. (2012) Hydrogen production from ethanol over Pd-Rh/Ce02 with a metallic membrane reactor. Catalysis Today, 193, 145-150. Montane, D., Bolshak, E. and Abello, S. (2011) Thermodynamic analysis of fuel processors based on catalytic-wall reactors and membrane systems for ethanol steam reforming. Chemical Engineering Journal, 175, 519-533. 

It is under development for various fuels such as methanol, ethanol, LPG and gasoline. The complete fuel processor was composed of a catalytic autothermal reformer reactor, a heat exchanger for cooling the reformate downstream of the CAR,... 

Figure 5.48 shows that the system efficiency of a methanol fuel processor decreases with increasing S/C ratio [407]. The same behaviour was observed for ethanol processing [440], as shown in Figure 5.49. 

Real-time switching between gasoline and diesel fuel could actually be demonstrated at different load levels without any apparent change to the performance of the system 621). However, low sulfur fuels were utilised exclusively. The fuel processor was tested in combination with an Andromeda fuel cell stack developed by Nuvera. No apparent difference could be observed when operating the combined system with ethanol, gasoline or diesel fuel [621]. However, recent activities of these workers have been directed towards a lOkWd on-board power plant or auxiliary power unit [621]. 

Actually the power level at which the tradeoff is likely to occur changes as processing and storage technology advances. One fuel processor developer has produced a 100 W partial oxidation (POX) methane reactor the size of a coffee can. The unit includes a reforming zone, shift reactors, and all heat exchangers. H2 is 36 percent (assume dry) and the CO level can be reduced to 1 percent. The unit runs on methane, propane, and ethanol (16). Another research project is investigating methanol reformers for sub-watt fuel cell power sources for the Army. 

The liquid fuel reformer that has been worked on at Los Alamos and the Argonne National Labs is a fuel-flexible processor which can reform gasoline, natural gas, methanol, or ethanol at the control of a switch. This would also allow the use of the existing fuel infrastructure, but this... 

This is the most economical process to produce ethanol, but laws prohibit drinking synthetic ethanol so beverages are made much more expensively by fermentation of sugar or carbohydrates. Recent laws also mandate the addition of 10% ethanol in gasoline in cities during the winter, supposedly to reduce pollution. However, grain processors lobbied to require renewable resources so fermentation is required to produce this fuel alcohol. 

A 50 kW multi-fuel partial oxidation processor coupled to an SPFC stack has been presented in October 1997 by Arthur D. Little Inc., USA, and test-operated in the meantime for more than 3000 h. The fuels that can be applied are gasoline, methanol, and ethanol in a later stage, also diesel, oil, methane and propane processing will be possible [27]. In the UK, a bench-scale steam reformer system processing gasoline and diesel was successfully demonstrated for over 50 hours each. The H2 concentration in the reformate was typically... 

Francesconi, J.A., Mussati, M.C., Mato, R.O. and Aguirre, P.A. (2007) Analysis of the energy efficiency of an integrated ethanol processor for PEM fuel cell systems./. Power Sources, 167, 151-161. 

Organic molecules, such as formic acid, methanol, or ethanol, may be used as a fuel at the anode, without a processor. These direct fuel cells also fall into the category of PEMFCs. 

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