(621bd) Kinetic and Thermodynamic Modelling of Methane Reforming Technologies: Comparison of Conventional Technologies with Dry Reforming

The need for effective utilization and conversion of the two greenhouse gases, carbon dioxide and methane emphasizes the interest in dry reforming of methane (DRM) reaction. DRM is a process in which CO₂ and CH₄ react to form synthesis gas, a mixture of CO and H₂, which can in turn be converted into liquid fuels and valuable chemicals via Fischer Tropsch Synthesis (FTS).

CH₄ + CO₂ ⇆ 2CO + 2H₂      ΔH°₂₉₈  = 247.3 kJ/mol

DRM process is plagued by a host of major drawbacks including its high energy intensity,  high rate of catalyst deactivation due to coke formation and low-quality syngas ratio(H₂:CO=1:1). These challenges have posed severe obstruction towards widespread commercialization of this technology [1]. The objective of this research is to simulate the behavior of different methane reforming technologies and to compare them with the DRM both in the thermodynamic and kinetic regimes. This process is the first stage of designing an effective DRM method and reactor configuration. The study also covers a novel process known as the tri-reforming of methane (TRM) that synergistically combines the endothermic processes of steam reforming of methane (SRM) and DRM with exothermic oxidation of methane that has been recently proposed in the literature[2, 3]. In the first stage of this study, various methane reforming processes such as SRM, DRM and TRM have been simulated thermodynamically using  Gibbs free energy minimization method similar to the technique used by Noureldin et al. [4]. The role of various process conditions such as the feed temperatures and pressures have been evaluated. The reults so far indicate that in terms of the energy requirements, TRM behaves at an optimum temperature of 840 K at 1 bar of operating conditions with a negligible amount of coke deposition under equi-molar feed conditions. Whereas the Noureldin et al[4] study assumed an ideal gas system, a unique feature of this work is to incorporate the influence of non ideality in the gas phase by using different equations of state (EOS) (i.e. Peng Robinson (PR), Redlich Kwong (RK) and Soave Redlich Kwong EOS) in the thermodynamic simulation of this system. This work is further continued to include the kinetics aspects of various reforming processes and their comparison with DRM. Different Langmuir-Hinshelwood Hougen-Watson (LHHW) kinetic rate expressions proposed in the literature will be tested to evaluate their feasibility in a reactor model for reforming process. This approach to carrying out both thermodynamic and reaction engineering analysis is advantageous in understanding the reforming process in a broader view and also help setting base for further experiments. The ultimate goal of this research campaign is to design novel catalysts and reactor system for the DRM that could protect the catalyst from the coke deposition, which is the major problem for such technology.

References

1.     Pakhare, D. and J. Spivey, A review of dry (CO2) reforming of methane over noble metal catalysts. Chemical Society Reviews, 2014. 43(22): p. 7813-7837

2.     Song, C., Tri-reforming: a new process for reducing CO₂ emissions. Chemical Innovation, 2001. 31: p. 21-26

3.     Jiang H, Li H, Zhang Y., Tri-reforming of methane to syngas over Ni/Al₂O₃—thermal distribution in the catalyst bed. Journal of Fuel Chemistry and Technology 2007. 35: p. 72–78

4.     Noureldin, M.M.B., N.O. Elbashir, and M.M. El-Halwagi, Optimization and Selection of Reforming Approaches for Syngas Generation from Natural/Shale Gas. Industrial & Engineering Chemistry Research, 2014. 53(5): p. 1841-1855