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

Abstract

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 °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.