Methane Cracking for Carbon Production

A series of models, focusing on various aspects and spatial scales, have been developed for simulation studies of methane pyrolysis, also called cracking, for carbon production in a laboratory scale test crucible. The background for the use of methane cracking is to capture carbon dioxide emmissions in the production of silicon by carbon looping and in this way reduce the impact on the climate. Partial differential equations have been used to model fluid flow, heat transfer and heat consumption in the pyrolysis. In the process carbon powder is produced and the interaction between powder particles and fluid flow is studied by simulations including heat transport. Both microscale as well as macroscale approaches have been used. A macroscale model for heat transport in a packed fluid bed of carbon powder, including chemical reactions, has been derived, and numerical results presented for a crucible with cylindrical symmetry. Homogenization has been applied in the study of the porous fluid bed of carbon, including methane reactions and heat transport to upscale a microscale model to determine the effective macroscale behaviour. A two fluid model consisting of the methane gas phase and a fluidised carbon phase has been derived also. Computational fluid dynamics simulations have been used to investigate various geometries for the design of the methane gas inlets and provided more desirable inflow geometries of the inlet. Simulation results has been presented for a simple lumped model of the methane cracking reaction, including the effect of heating, inlet and outlet flow from the crucible. The lumped model provides an overall picture in a simple and easy fashion.