Preliminary Evaluation of Methods for Continuous Carbon Removal from a Molten Catalyst Bubbling Methane Pyrolysis Reactor

Abstract

Methane pyrolysis in molten catalyst bubble (MCB) column reactors is an emerging technology that enables the simultaneous production of hydrogen and solid carbon, together with a mechanism for separating the two coproducts. In this process, methane is dispersed as bubbles into a high temperature molten catalyst bath producing hydrogen and low-density carbon, which floats to the surface of the bath from providing a means for them to be separated. However, the removal of carbon particulates from a bubbling column reactor is technically challenging due to the corrosive nature of the molten catalysts, contamination of the product carbon with the molten catalysts, high temperatures and lack of understanding of the technology options. Four potential concepts for the removal of carbon particulate from a methane pyrolysis molten metal bubble column reactor are presented, based on the pneumatic removal of the particles or their overflow from the reactor. The concepts are evaluated using a cold prototype reactor model. To simulate the operation of a high-temperature reactor at low temperatures, the dominant dimensionless numbers are identified and matched between a reference high-temperature reactor and the developed cold prototype using water, air and hollow glass microsphere particles as the representatives of the molten catalyst, gaseous phases and solid carbon particulates, respectively. The concepts are tested in the cold prototype. High rates of particle removal are achieved, but with different tradeoffs. The applicability of each method together with their advantages and disadvantages are discussed.