DEVELOPMENT OF A TUBULAR-FLAME BURNER FOR A FUEL PROCESSING SYSTEM IN FUEL CELL SYSTEMS
Sustainable process-product development & green chemistry
Sustainable & Clean Technologies - IIb: Energy Production (T1-5b)
Keywords: tubular flame, fuel cell, fuel processing, burner, power generation
As one of the power generation systems that can contribute to decrease emission of carbon dioxide (a greenhouse gas), polymer electrolyte fuel cell (PEFC) has been highlighted in Japan. We have been developing 1kW-50kW power generation systems using our PEFC and fuel processing system (FPS) [1], which generates hydrogen from various fuels: kerosene, liquefied petroleum gas (LPG), city gas, dimethyl ether (DME) and so forth. The FPS consists of three catalytic processes: steam reforming reaction of hydrocarbon (Fuel+H2O→CO+3H2), CO shift reaction (CO+H2O→CO2+H2), and CO preferential oxidation (CO+0.5O2→CO2). Each process needs to be controlled by a burner at an appropriate temperature that corresponds to its target equilibrium state with permissible variation. In this study, combustion technology in the FPS is focused and a new-concept burner of kerosene using tubular flame is introduced. The tubular flame has shown a possibility to provide breakthroughs with the practical burners.
Tubular flame formed in a rotating flow field is located at the interface between an inner region of hot burned gas and an outer region of cold unburned gas. Due to centrifugal force in the swirl-type burner, the flame is aerodynamically stabilized and negative pressure inside the flame induces recirculation effect of the burned gas, which may benefit NOX emission. For these characteristics, the tubular-flame burner has been widely recognized as the next-generation combustion technology [2]. In addition, axial symmetry of the flame leads to axisymmetric heating of inner surface of cylindrical FPS, which differentiates this burner from the conventional burners.
The tubular flame was applied to a burner of the FPS. Fuels adopted in this study are kerosene and city gas. The performance was optimized by experiment using Taguchi method, which is one of the experimental design methods. It is generally believed that there are trade-offs between emission of NOX and CO and between stability and emission of NOX. Nevertheless Taguchi method clarified effect of each design factor on concentration of NOX and CO and made it possible to decrease the emissions simultaneously. With the developed 10kW burner of kerosene, the extremely low emission of NOX was attained with CO emission less than 10ppm for a wide range of equivalent ratio. Additionally, circumferential dispersion of the burned gas temperature is less than 50 [K], which verifies axisymmetric heating characteristics of the developed burner.
To summarize, the burner of kerosene is dramatically developed by eliciting potential of tubular flame. The application of the tubular flame is successfully conducted because it is verified that the developed burner is more stable, low emissive and axisymmetric than conventional burners. It can be expected that tubular flame is a promising combustion technology in various industrial areas as well as fuel cell systems.
([1] Yagi, K. et al., The 6th KSME-JSME Thermal & Fluids Engineering Conference, Jeju, Korea, JJ. 02 (CD-ROM), 2005-3. [2] Ishizuka, S. et al., Transactions of JSME 65, pp.3845-3452, 1999. This research is financially supported by the New Energy and Industrial Technology Development Organization (NEDO)).
Presented Wednesday 19, 11:40 to 12:00, in session Sustainable & Clean Technologies - IIb: Energy Production (T1-5b).
