Research has focused on dry reforming because it offers a sink for CO2 and relative to steam
methane reforming produces a more desirable ratio of H2 to CO for feed to a Fischer−Tropsch
synthesis process. To form synthesis gas by dry reforming in a rapid, environmentally benign
manner, a fluid-wall aerosol flow reactor powered by concentrated sunlight has been designed.
Operating with residence times on the order of 10 ms and temperatures of approximately 2000
K, CH4 and CO2 conversions of 70% and 65%, respectively, have been achieved in the absence
of any added catalysts. Methane to carbon dioxide feed ratios greater than unity were fed in
order to prevent reaction of CO2 with the graphite tube. The carbon black particles formed by
reaction were amorphous carbon black with a primary particle size of approximately 20−40
nm.
High temperature biomass gasification has been performed in a prototype concentrated solar reactor. Gasification of biomass at high temperatures has many advantages compared with historical methods of producing fuels. Enhancements in overall conversion, product composition ratios, and tar reduction are achievable at temperatures greater than 1000°C. Furthermore, the utilization of concentrated solar energy to drive these reactions eliminates the need to consume a portion of the product stream for heating and some of the solar energy is stored as chemical energy in the product stream. Experiments to determine the effects of temperature, gas flow rate, and feed type were conducted at the high flux solar furnace at the National Renewable Energy Laboratory, Golden, CO. These experiments were conducted in a reflective cavity multitube prototype reactor. Biomass type was found to be the only significant factor within a 95% confidence interval. Biomass conversion as high as 68% was achieved on sun. Construction and design considerations of the prototype reactor are discussed as well as initial performance results.
A graphite fluid-wall aerosol flow reactor heated with concentrated sunlight has been developed over the past five years for the solar-thermal decarbonization of methane. The fluid-wall is provided by an inert or compatible gas that prevents contact of reactants and products of reaction with a graphite reaction tube. The reactor provides for a low thermal mass that is compatible with intermittent sunlight and the graphite construction allows rapid heating/cooling rates and ultrahigh temperatures. The decarbonization of methane has been demonstrated at over 90% for residence times on the order of 10 milliseconds at a reactor wall temperature near 2000 K. The carbon black resulting from the dissociation of methane is nanosized, amorphous, and ash-free and can be used for industrial rubber production. The hydrogen can be supplied to a pipeline and used for chemical processing or to supply fuel cell vehicles.
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