Methane pyrolysis: Kinetic studies and mechanical removal of carbon deposits in reactors of different materials

CO2-free hydrogen can be produced by pyrolysis of methane using renewable energy. In a simple tubular reactor, however, carbon formation leads to clogging. The aim of this work is to deliberately coke reactors of different materials in order to investigate and characterize the mechanical removal of carbon. A design of experiments is used to study the influence of temperature, volumetric flow rate and methane mole fraction on the rate of reaction, which was followed by a kinetic fit of the methane pyrolysis process. The investigations show an increase in conversion with an increase in temperature and a decrease in volume flow rate, while methane mole fraction shows no significant influence. Fitting of collision factor, activation energy and reaction order results in deviations <10% between experiment and model. The force required for mechanical carbon removal can be decreased significantly by internally coating the reactor with calcium oxide. Using a simple plunger device, more than 90% of the agglomerated carbon can be removed easily from the reactors.