Key Technology Research Of The Hydrogen Source System Based On MgH₂Hydrolysis Reaction

The method of acquiring hydrogen by the reaction between hydrogenatedmagnesium-based composite and water at low temperature, can not only fully make useof the property of magnesium to store hydrogen in large capacity, but also make thehydrogen atoms release from water in the form of hydrogen, and the final theoreticalcapacity of storing hydrogen can reach up to15.31%in weight if the water is cyclicallyutilized. In this paper, the key technologies of MgH₂hydrolysis reaction performanceand the hydrogen source system are studied, including the MgH₂hydrolysis reactionperformance at the condition of different additives, different pH values and differentpressures and the design of hydrogen source system based on the hydrolysis reaction ofMgH₂, and its property is examined for the first time.The Mg-Mn composite is prepared using the method of ball milling in hydrogenand its hydrolysis property conducted by using the self-designed apparatus at differentfactors is analyzed, and the resultant micromorphologies are observed and characterizedby using scanning electron microscope（SEM） and X-ray diffraction（XRD）.The results indicate that the phosphate additives have significant effect onimproving the rate of generating hydrogen in the hydrolysis reaction of MgH₂andresultant’s morphology with relatively small size and large amount of lamellar structurewas beneficial to the reaction of MgH₂. It can be concluded that, the change of pH valuein the solution has no obvious improvement to the performance of MgH₂hydrolysisreaction, with the increasing of pH value, the reaction degree gradually decreased; andthe SEM photograph of reaction products also show that: the gathering phenomenonwas more obvious with the increasing of pH value, this phenomenon proved aboveconclusion further. When the pressure of hydrolysis reaction is changed, the final degreedecrease with the pressure value raising, this decrease is little when the pressure value islow, and in the next experiments, the H₂pressure has better been controlled under8.361kgf/cm2; the SEM and XRD results show: much particle of resultant presentirregularly lamellar polygonal with the grain size from10.7nm to20.8nm.In the research of the hydrolysis reaction mechanism about changing the pH valueand reaction pressure in the hydrolysis reaction, it could be discovered that the value oftransient Avrami exponent n increase firstly and then decrease with the reactionproceeding. It can be predicted that the crystal nucleus is precipitated and grow at theinitial stage of reaction, then the crystal nucleus continue to grow further.The self-design hydrogen source system consist of a reaction vessel, the reactionvessel heating sleeve, a tank, a transition vessel and ancillary equipment such as acontrol box, a vacuum pump, a air compressor and the hydrogen pressurized machine and so on. The trial experiment of MgH₂hydrolysis reaction is carried out on the system,and the results demonstrate that the reaction rate is large from0min to7.5min, then therate decreased from7.5min to20min, after20min it almost reduce to zero, thehydrolysis degree can be improved by continuous experiments.