Process configurations to lower the temperature of methane pyrolysis in a molten metal bath for hydrogen production

Novel configurations of a process for methane pyrolysis using a molten catalyst bubble column reactor are proposed in this study. These configurations aim to achieve reasonable conversion at temperatures below 1000 degrees C by recycling a fraction of the hot reactor product gas. Three recycling configurations are assessed: the first utilizes an ejector, the second employs a compressor, and the third combines a compressor with a turbo-expander. The performance of these configurations was evaluated using ASPEN HYSYS to compare them against a reference cycle without recycling. The evaluation criteria included methane conversion and the thermal heat requirement of the reactor. The results indicate that recycling can significantly increase methane conversion, with a maximum improvement of 165%. Specifically, when recycling 80% of the hot products in the first pass conversion using the third configuration, methane conversion increased from 17.8% to 47.2%. The other two configurations achieved conversions of 28%, representing a 57% increase from the baseline of 17.8% under the same conditions. Furthermore, it is possible to achieve a configuration with zero net CO2 emissions by employing renewable power and utilising some of the hydrogen product for combustion to meet the process heat demand.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.