Fuel-cell based electricity generators produce no NOx and particulates owing to the absence of high temperature gas combustion. As opposed to electric batteries, fuel cells do not run down or necessitate recharging. They produce continuous electricity provided hydrogen along with an oxidizer is supplied to the cell continuously. Unfortunately, presently there exists no hydrogen infrastructure to implement wide spread application of fuel-cell generators. An alternative solution to this would be to take advantage of an efficient fuel reformer to generate hydrogen. This can benefit from the natural gas supply in several countries.
Indirect heat supply from catalytic combustion of methane can be realized in a catalytic plate reactor. A catalytic plate reactor design is composed of a number of thin metal plates with both sides coated with suitable catalyst for the endothermic as well as exothermic reactions and organized in a stacked configuration.
Mayur Mundhwa and Christopher Thurgood at the Royal Military College of Canada in collaboration with Rajesh Parmar at Queen’s University developed two separate 2-dimensional steady state computational models of the catalytic plate reactor for a parametric study with various combustion-catalyst coating configurations. One of the models simulated methane steam reforming on one side of a thin plate over a continuous layer of nickel/alumina catalyst and a catalytic methane combustion on the other side of the plate over platinum/alumina catalyst layers. Their research work is published in Journal of Power Sources.
The authors performed a parametric study between conventional continuous and segmented layer configurations of the coated combustion-catalyst in a bid to assess their effects on the operation of methane steam reforming for the production of hydrogen in a catalytic plate reactor. They simulated methane steam reforming on one side of the plate over a continuous nickel/alumina catalyst layer by using an experimentally validated surface microkinetic model. Thermal energy needed for the methane steam reforming was supplied through the simulation of catalytic methane combustion on the opposite side of the plate over continuous and segmented platinum-alumina catalyst layer through the implementation of the power law rate model.
Catalytic plate reactor designed with segmented layer of combustion-catalyst and co-flow posted superior performance with regards to high methane conversion as well as high hydrogen production. This reactor was also superior in minimizing the maximum reactor plate temperature, thermal hot-pots and thermal gradients. This improved performance was reference to the continuous supply of heat to the reforming side from the side of combustion via the spacing between the active catalyst segments. This reactor also indicated about 7-8% less combustion feed flow requirement, and approximately 70% less combustion-catalyst to yield to necessary hydrogen flow as compared to a catalytic plate reactor designed with continuous layer of combustion catalyst.
The authors observed that increasing the reforming catalyst thickness by a factor did not improve the reforming side methane conversion by the same factor. This was reference to low heat transfer via the thick catalyst layers and an increase in the internal mass-transfer resistance.
Mayur Mundhwa, Rajesh D. Parmar, Christopher P. Thurgood. A comparative parametric study of a catalytic plate methane reformer coated with segmented and continuous layers of combustion catalyst for hydrogen production. Journal of Power Sources, volume 344 (2017), pages 85-102.Go To Journal of Power Sources