Autonomous natural gas reformer for on-demand and on-site hydrogen generation (Technion)
Power generation from hydrogen fuel cells is a well-known environmentally-friendly and efficient method for power generation. However, as with any fuel source, hydrogen must be either produced in situ or distributed through an established distribution network. For hydrogen, distribution involves costly and complex compression, liquefaction, and storage which greatly reduce the efficiency of power production from hydrogen fuel cell stacks. This highly efficient membrane reformer can produce high-purity hydrogen autonomously taking advantage of the existing infrastructure or cost-effective storing and shipping of natural gas. Also, conventional industrial steam reformer units rely on external sources for the intense heat necessary for hydrogen production, while this compact unit uses the methane fuel source to reliably and efficiently generate the heat, as well as the hydrogen for the fuel cell.The autonomous membrane methane reformer is composed of several stainless steel tubes each containing a catalyst. Natural gas and air are supplied to the oxidation tubes which generate heat through catalytic methane combustion and transfer it to the reforming tubes. Then, natural gas and water are supplied to the reforming tubes which produce the hydrogen via catalytic steam reforming. The generated hydrogen is separated by highly selective membranes, resulting in ultra-pure hydrogen that can be directly fed to a fuel cell stack for immediate power generation, while the effluent (off-gas) may be recycled for byproducts combustion. Ideally, the reformer may be operated without recycling as the effluent will contain mostly water and carbon dioxide and the carbon dioxide may be easily separated through water condensation. Alternatively, the reformer can recycle the steam-reforming high-pressure products to the combustion chamber to utilize the energy of un-reacted H2, CO and methane. Thorough analytical analysis of the system resulted in a robust optimization algorithm which effectively predicts reformer efficiency and power output and will most certainly constitute an important tool in subsequent system up-scaling and development.
• Implementation of the membrane reactor concept results in a more compact, single-unit design, as compared to multi-unit non-membrane designs (including several reactors in series plus a separation unit)
• The use of highly-selective, supported metallic thin films membranes allows for direct integration of the reformer to polymer electrolyte fuel cell (PEM) stacks
• The thermally independent design results in a more efficient unit, as compared to conventional designs with external heat sources
• The novel approach of the indirect heat coupling of endothermic and exothermic processes provides additional benefits in terms of compactness and energy conversion efficiency
• On-site production of ultra-pure hydrogen eliminates logistics and costs of fuel storage and transport
• Residential electrical power generation units
• Integration into CHP or micro-CHP (combined heat and power) units
• Fuel for generators in remote installations like cell-phone towers or remote monitoring stations, DER (distributed energy resource) units
• On-site hydrogen production for commercial fleets of electric vehicles
ENE-1167
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