Multi-scale Modeling of Steam Methane Reformer Heated by Electrical Current

• Author / Creator

  Lu, Yi Ran

• The study is dedicated to investigating the possibility of a new type of fixed-bed steam methane reformer heated by an electrical current flowing through the particles.
  The objective of the thesis is to develop multi-scale modeling for the electrically heated reformer made of bi-disperse particles.
  The electrically conductive metal particles act as heating elements,
  providing the heat of reaction for the endothermic reactions, and the catalyst particles provide the active sites for reaction.
  To verify this concept, a new multi-scale 1D-3D Euler-Lagrange model has been developed and validated.

  A single catalyst particle is simulated using 3D CFD software.
  The catalyst is exposed to a stream of reacting gas using LHHW kinetics.
  The full thickness of the boundary layer is resolved. A 0D submodel was developed based on the results of the 3D CFD simulation.
  Excellent agreement was demonstrated. The 0D submodel is contrasted against 1D solutions in a parametric study to verify its usage for various temperatures (650K-1000K), particle size (2mm-25.4mm) and boundary conditions.
  Good agreement was found using the 0D model comparing the 1D results.
  The submodel is assembled in a 1D-3D Euler-Lagrange model to simulate reactions in a steam methane reformer.
  The results from the new model were validated against results from particle-resolved 3D-CFD simulation published in the literature.
  The comparison between our DEM-based model and 3D CFD case demonstrated good agreement.

  The volt-ampere characteristics of a fixed bed heated by the Joule heating were calculated using the node-voltage method by treating the particle centers as nodes and the contact points as resistors.
  An experiment was conducted to validate the method using a cylinder filled with metal spheres.
  Electricity was flown through the bed and the voltage and current were measured.
  Open-source DEM software is used to model the packing of the fixed bed.
  Based on the packing, the electric field distribution is calculated using a new DEM-based model, coupled with heat transfer simulation to account for the temperature dependency of the steel particles' electrical conductivity.
  The results were found to be in good agreement with experimental data.

  The multi-scale model is then used to simulate a steam-methane reformer with electrically heated particles.
  The Joule heating term for each electrically conductive particle was calculated.
  The interparticle heat conduction is calculated based on contact area, particle size and thermal conductivity.
  The most important feature of the multi-stage model is that it retains 3D characteristics of the system in the solid phase,
  such as a strong radial temperature gradient in the wall-heated case, yet demands computational power significantly less than that of a 3D simulation.
  A cylindrical electrically insulated tube filled with 23000 particles was simulated to test the performance of the model and the feasibility of the concept.
  The limit for maximum power and temperature and a correlation between conversion and flowrate was found.

  A larger SMR comprising 1 million particles was simulated in the scale-up study.
  The reformer has a diameter of 0.5 m and a height of 0.88 m and is filled with metal particles and catalyst particles with diameters of 10 mm and 4 mm, respectively.
  The modeled results show that electric current and Joule heating are widespread and well scattered in the fixed bed.
  The main distinguishing feature of the reformer is the relatively uniform temperature distribution in the radial direction regardless of the diameter of the fixed bed.
  Parametric runs have been carried out for different flow rates from 0.04 kg/s to 0.1 kg/s and electrical power from 185 kW to 462 kW.

  The multi-stage model proved to be a useful way to resolve the intricacies of the complex phenomenon inside a reactor, not only for the new electrically heated SMR but also in other
  cases with a strong internal heat source and sink for energy conversion and storage.
  It fills the gap between the continuum model and the particle-resolved model.
  Future steps towards realizing and implementing the new reformer have been laid out in this study.

• Subjects / Keywords

  • Modeling
  • DEM
  • Steam-methane reforming
  • Joule heating
  • Energy storage

• Graduation date

  Fall 2022

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-crmc-a242

• License

  This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.