Syngas generation from n-butane with an integrated MEMS assembly for gas processing in micro-solid oxide fuel cell systems

Abstract

An integrated system of a microreformer and a carrier allowing for syngas generation from liquefied petroleum gas (LPG) for micro-SOFC application is discussed. The microreformer with an overall size of 12.7 mm 6 12.7 mm 6 1.9 mm is fabricated with micro-electro-mechanical system (MEMS) technologies. As a catalyst, a special foam-like material made from ceria-zirconia nanoparticles doped with rhodium is used to fill the reformer cavity of 58.5 mm 3 . The microreformer is fixed onto a microfabricated structure with built-in fluidic channels and integrated heaters, the so-called functional carrier. It allows for thermal decoupling of the cold inlet gas and the hot fuel processing zone. Two methods for heating the microreformer are compared in this study: a) heating in an external furnace and b) heating with the two built-in heaters on the functional carrier. With both methods, high butane conversion rates of 74%-85% are obtained at around 550 uC. In addition, high hydrogen and carbon monoxide yields and selectivities are achieved. The results confirm those from classical lab reformers built without MEMS technology (N. Hotz et al., Chem. Eng. Sci., 2008, 63, 5193; N. Hotz et al., Appl. Catal., B, 2007, 73, 336). The material combinations and processing techniques enable syngas production with the present MEMS based microreformer with high performance for temperatures up to 700 uC. The functional carrier is the basis for a new platform, which can integrate the micro-SOFC membranes and the gas processing unit as subsystem of an entire micro-SOFC system.

A thermally self-sustained micro-power plant with integrated micro-solid oxide fuel cells, micro-reformer and functional micro-fluidic carrier

“…In a commercial device, the gas tank would be integrated in the system, which will allow a much denser packaging. Several publications exist on the feasibility of entire system and possible energy sources for the start-up energy [5,6,38], here we focus only on the subsystem -micro-SOFC, micro-reformer and heater gas-supply (functional carrier).…”

“…Micro-solid oxide fuel cells (micro-SOFCs) operate at higher temperatures, and therefore, high-energy density and high specific energy hydrocarbon fuels such as propane or butane can be used. ONEBAT™ is such a micro-SOFC system consisting of electrochemically-active micro-SOFC membranes fabricated on a micro machined chip, a gas processing unit composed of a fuel reformer, an exhaust gas postcombustor and a thermal management system and insulation [4][5][6]. Nectar™, a similar system based on micro-SOFC membranes is announced for commercialization, however, so far the product is not available [7].…”

A review of recent advances in numerical simulations of microscale fuel processor for hydrogen production

“…Therefore fuel processing systems for PEMFC must produce a hydrogen rich gas stream with less than 100 ppm CO, or preferably less than 10 ppm CO [12]. Several higher temperature fuel cells have been proposed for small scale power supplies including phosphoric acid doped polybenzimadole (PBI), which operates at 388-423 K and solid oxide fuel cells (SOFC), which typically operate >973 K [13][14][15]. PBI FC and SOFC both can tolerate CO at higher concentrations (>1% and >10% respectively), making the fuel processing requirements less stringent [13][14][15];…”

“…If water is included in the energy density, methanol actually has a slightly higher energy density than other hydrocarbons, and is only slightly less than that of methane (Table 1). Other fuels of interest include: ammonia [16], methane [17][18][19], butane [14], and ethanol [20][21][22]. Table 1.…”

A low-temperature co-fired ceramic micro-reactor system for high-efficiency on-site hydrogen production

“…For these reasons, we recently proposed ceramic-and glassbased micro-reactors for high-temperature reforming reactions [9,14e16]. Hotz et al [9] developed a disk-shaped micro-reactor made of quartz glass and achieved high selectivity of H 2 (92%) and CO (82%) species via CPOX of butane at 550 C. In a previous work [14,17], we developed an aluminoborosilicate glass-based micro hot plate on which a micro reformer for syngas production was integrated by glass sealing. Its efficient thermal decoupling allowed a thermally self-sustaining CPOX syngas production above 500 C, and served to demonstrate an integrated m-SOFC unit for producing a power density of 50 mW cm À2 at~550 C. However, the utilized glass materials system (especially the sealing glass) was found to be somewhat fragile to thermal shock under operation cycles, which we ascribed to high thermal gradients and resulting mechanical stresses arising from the low thermal conductivity of glass.…”