Study On Vapor Supply Methods And Diffusion Dynamics In Hydrogen Production Reactor By Al-H₂O Reaction At Medium Temperature

As the fossil energy crisis worsens,accelerating the energy revolution and developing renewable clean energy have gradually reached consensus among all countries.The Al-H2O reaction with its advantages of high hydrogen production efficiency,high heat release,clean and pollution-free,has become one of the hot spots in the field of hydrogen production.This paper was based on the application of hydrothermal co-production system of Al-H2O reaction.By using self-made Al-H2O reaction system,the rapid and efficient hydrogen production and heat production from the reaction of 6g Al-Li alloy and water vapor at medium temperature were realized.The water vapor was suppplied under the liquid.In this paper,the influence of the change of carrier gas flow rate and water supply on the dynamic hydrogen production and exothermic process in the reactor was first studied experimentally.Under the condition of 1.0mL/min water supply,the hydrogen production rate and reaction efficiency had been significantly improved with the increase of carrier gas flow rate.However,the reaction temperature was low,up to only 733℃.By adjusting the rate of water flow,the maximum temperature of the reaction had been effectively increased.With the increase of water supply,the reaction temperature first increased and then decreased.When the carrier gas flow rate was 700ml/min and water flow rate was 1.5mL/min,the maximum temperature in the reactor could reach to 999 ℃.By analyzing the migration rule of the high temperature zone during the reaction process,the migration rule of reaction core zone was obtained.After the water vapor was introduced,the sample near the inlet was the first to react and heat up.With the consumption of the sample and the diffusion of water vapor,the reaction core zone showed upward and downward vertical migration from the inlet.The migration upward was faster than downward.After the reaction was completed,the reaction product was stratified vertically in a cold state and examined by means of SEM,EDS and XRD.The results showed that along the vertical direction,the reaction products had obvious trends in color,composition and degree of oxidation At the inlet,the sample was highly reactive and its crystal form was regular.As the distance between the product and the inlet increased,the degrees of oxidation and crystallinity gradually decreased.Meanwhile,there was a lot of Al and Al-Li detected at the bottom of the reactor.In order to understand the influence of water vapor diffusion on the reaction better and provide a guide for the design of intake-tube,the effects of liquid-on,liquid-in and liquid-bottom methods on the hydrogen production,heat release and diffusion characteristics of the reaction were compared.Compared to the liquid-on and liquid-in methods,the hydrogen production rate and efficiency of aluminum-water reaction had been obviously improved when the vapor was pumped into the bottom.The instantaneous hydrogen production rate could reach to 463.76 mL/(min·g)and the reaction efficiency could reach to 85.9%.It was mainly due to the intake port down,the contact of water vapor with alloy in bottom was promoted,so that the reaction efficiency was improved.At the same time,through the analysis of the temperature change,the upward transfer rate of the reaction was obviously higher than the downward transfer rate when the vapor inlet was at the bottom.This was mainly due to the rising movement of the air stream which promoted the diffusion of water vapor and the mixing of the alloy with water.