The engine reformer : syngas production in engines using spark-ignition and metallic foam catalysts

[摘要] An experimental study was performed to assess the feasibility of performing methane (CH4) partial oxidation (POX) in two internal combustion engines: one equipped to perform spark-ignition (the ;;spark-ignited engine;;), and the other containing a catalyst in the engine cylinder (the ;;catalytic engine;;). The exhaust gases were rich in hydrogen- (H 2) and carbon monoxide- (CO), and could be used as synthesis gas (;;syngas;;) for the synthesis of liquid fuels such as methanol. Conventional syngas production techniques are only economical on a large scale and cannot be transported to hard-to-reach gas sources, where gas-to-liquids (GTL) would have the biggest impact on the transportability of that gas. Engines could be deployed at these locations to produce syngas on a small scale and at low cost, as they benefit from the economies of mass production that have been achieved through advanced manufacturing techniques. We call this type of engine an ;;engine reformer;;. This thesis contrasts the results of performing methane POX in two different engine reformers, using atmospheric air as the oxidizer. One of four cylinders in a Yanmar 4TNV84T marine diesel generator was converted to ignite methane POX mixtures using a spark plug. Intake temperatures > 350 °C were required to minimize misfire. Exhaust H2 to CO ratios of 1.4 were achieved with methane-air equivalence ratios (0m) up to 2.0, while ratios of > 2.0 were achieved with hydrocarbon-air equivalence ratios (PHc) up to 2.8 with the assistance of hydrogen (H 2) and ethane (C 2H6). High equivalence ratios °PHC > 2.2 showed reduced CH4 conversion efficiency, therefore PHC = 2.2 (with H2 produced a good tradeoff between syngas quality and CH4 conversion. A single-cylinder Lister-Petter TRl diesel generator was used to perform methane POX using a palladium (Pd) washcoat catalyst deposited on a Fecralloy® disk. With > 150 °C intake temperatures, exhaust H2 to CO ratios of 1.0 were achieved with methane-air equivalence ratios (PM = 4.0 with varying amounts of CO2 to simultaneously perform methane dry reforming. Spark-ignition appeared to provide higher reliability, though tests will continue to be performed on the catalytic engine to optimize performance. A larger engine of a similar design to the spark-ignited Yanmar will be deployed at a demonstration plant in North Carolina to produce syngas at higher flow rates, and will be integrated with a liquids synthesis reactor to produce methanol.

[发布机构] Massachusetts Institute of Technology