Experimental And Modeling Study On Hydrogen Production System Of Aluminum/Sodium Borohydride-water Reaction At Medium And High Temperatures

Hydrogen production by aluminum-water reaction and hydrogen hydrolysis by sodium borohydride are two research hotspots in the field of hydrogen production.However,in the application process,the reaction temperature of the aluminum water in the solution is low,so the reaction heat can not be effectively utilized.The aluminum water reaction at high temperature lacks the civil basis due to the high reaction initiation temperature;sodium borohydride is in the aqueous solution.The catalytic hydrolysis does not reach its theoretical maximum hydrogen storage rate,and it is usually necessary to add a catalyst.Therefore,the experiments of this paper are designed to investigate the coupling characteristics of the aluminum/sodium borohydride/water reaction,and to study the hydrogen production system of aluminum/borohydride/water reaction at medium and high temperatures through various detection and analysis methods.Firstly,the thermodynamic properties of aluminum/aluminum-lithium alloy/sodium borohydride reacted with water were studied by thermodynamic calculation software.It is found that initiation temperature of the reaction and form of the reaction water have a great influence on the enthalpy change and the Gibbs free energy change of the aluminum/aluminum-lithium alloy/sodium borohydride reaction with water,but pressure has less impact on the enthalpy change and the Gibbs free energy change.In particular,the ratio of aluminum/sodium borohydride has a great influence on the product composition and thermodynamic properties of the the coupling reaction with water.In the experimental study of the reaction of elemental aluminum with water,it was found that nano aluminum powder reacted significantly with water at 460?,while micron aluminum powder showed no obvious reaction even at 560?.In the experimental study of the reaction of aluminum-lithium alloy with water,the product analysis results indicate that there is likely a coupling reaction between aluminum and lithium.In the experimental study of the reaction of sodium borohydride with water,it was found that sodium borohydride could undergo a quite complete hydrolysis reaction with water at the initiation temperature of 260?.Based on the above experimental phenomena and analytical test results,coupling reaction experiments between Al and NaBH₄ were carried out.The experimental results show that the addition of sodium borohydride increases the temperature and hydrogen production rate of the reaction zone.The analysis of the product shows that the addition of sodium borohydride also improves the reaction efficiency of the nano aluminum powder.The coupling product of aluminum and sodium borohydride was detected in the experimental product,indicating that in addition to heat transfer and water vapor sharing,there is a coupling reaction relationship between aluminum powder and sodium borohydride.A heat and electric cogeneration system based on aluminum-sodium borohydride coupling reaction was designed,and the Al-NaBH₄ coupling reaction was used as the energy source for the energy system.After calculation,the system energy utilization efficiency can reach up to 60%,which overcomes the shortcomings of the aluminum energy system that mainly utilizing thermal energy and the sodium borohydride energy system that mainly utilizing electric energy.The modeling and calculation of the reaction and heat transfer process in the Al-NaBH₄ coupling reactor were carried out.The reaction and heat transfer process were coupled by micro-element iteration and the data exchange between two program modules.The calculation software was then compiled.The software can be used to investigate the effects of adjustable parameter,such as the mass flow of reaction inlet and the mass flow of cooling water,on the temperature field in the coupled reactor.Finally,the reactor nozzle structure of the Al-NaBH₄ coupling reaction was designed and simulated by the Fluent software.Cold state simulations of 2D/3D were carried out on different arrangements of nozzles,and the hot state simulation of the dynamic temperature field in the reactor was carried out.