A hydrogen generator coupled to a hydrogen heater for small scale portable applications

This study aims to build and test a small scale portable device able to couple a hydrogen generation system (based on a NaBH4 solution as liquid H2 carrier) to a hydrogen heater (based on the exothermic catalytic combustion of the released H2). The hydrogen generating system is based on the hydrolysis of stabilized solutions of NaBH4 (fuel solutions) which are pumped into the hydrolysis reactor. The generated H2 feeds the catalytic combustor. Two catalysts have been developed for the H2 generation and the combustion reactions able to operate at room temperature without need of additional energy supply. For the NaBH4 hydrolysis a Co-B catalyst was supported on a perforated and surface treated stainless steel (SS316) home-made monolith. For the flameless H2 catalytic combustion a Pt catalyst was prepared on a commercial SiC foam. The device was automatized and tested for the on-demand production of heat at temperatures up to 100ºC. In steady state conditions the NaBH4 solution flow is controlling the H2 flux and therefore the heater temperature. Once the steady-state is reached the system responds in a few minutes to up and down temperature demands from 80 to 100 ºC. The catalysts have shown no deactivation during the tests carried out in several days.

Design and Empirical Inquisition of Catalytic Combustor for Methanol Steam Reformer in HT-PEM Fuel Cell Systems

Steam reforming of methanol is a basic endothermic reaction. For which, a separate external system is required for generation of heat. The reaction speeds are controlled by operating temperature and heat transfer rate to the reactor. This operating temperature has a very narrow window of operation. It is therefore extremely important to have a system that generates controlled combustion based stable heat for providing required heat to reformer. A design of catalytic combustor was developed and analyzed for methanol steam reformer. The packed bed of combustion catalyst provides active sites for combustion of the methanol water mixture during start-up and later for combustion of anode exhaust gas (AEG) during normal operation. The combustion reactions and their thermodynamics were studied for commercial catalyst. System design was simulated using Engineering Equation Solver (EES) software for determining the quantity of air required for combustion of fuel as well as for dilution of gases to maintain a temperature of 573 K. The design was analyzed using ANSYS DISCOVERY LIVE for understanding the different operating condition(s) inside the combustor. It was also used to generate design of experiments to evaluate, build and demonstrate a catalytic combustor for on-board reformer for HT-PEM fuel cell system.

Investigation of Catalytic Combustion in the Rotary Regenerator Type Catalytic Combustor at Different Inlet Velocities

Ultra low calorific value gas (ULCVG) is hard to be realized by the conventional combustion technology. Most of them are discarded into atmosphere directly, causing the inadvertent waste and serous pollution. Currently, a new type gas turbine with catalytic combustion and rotary regenerator can be used to utilize these fuels and mitigate pollution. Differing from the conventional gas turbine, the chamber and regenerator of the new gas turbine is combined into one component, which is named rotary recuperative type catalytic chamber (RRTCC). The catalytic combustion is applied for RRTCC. The catalytic combustion characteristic of RRTCC is studied using the computational fluid dynamics (CFD). The results indicate that when the inlet velocity is 20 m/s, the methane conversion rate is 90%∼95%, and the corresponding outlet gas temperature is 1030∼1200K. When there is a variation of ±25% in the inlet velocity, the variation of methane conversation rate is −15% and 5% respectively, and the variation of outlet gas temperature is −6% and 2% respectively. Additionally, it is found that the hotspot temperature of combustor wall decreases with the increase of inlet velocity. The lowest value of hotspot temperature is about 1000K, which is higher than the ignition temperature of CH4. Therefore, the existence of hotspot temperature is useful for the catalytic ignition. The temperature distribution on the combustion side exhibits a smoking-pipe-like shape, as well as the recuperative side. The results can provide data reference for RRTCC design.