Characteristics And Mechanism Of Hydrogen Produced By Pulsed Discharge Plasma In Liquid

Situ hydrogen production is an important development direction in the field of hydrogen production,which can be used in the ships or automobiles.Plasma technology is suitable for situ hydrogen production owing to its instantaneity and high-efficiency.Discharge plasma in liquid has been researched for several years,however,discharge plasma in liquid for hydrogen production is still in the initial stage.The problems existed in discharge plasma in liquid for hydrogen production contain:how to decrease the energy consumption of hydrogen production to fit the industrial applications,to find the economic and applicable raw materials for hydrogen production,to clarify the mechanism of hydrogen produced by discharge plasma in liquid.Considering the current problems,this work researches hydrogen produced by pulsed spark discharge plasma in alcohols.The characteristics and mechanism of hydrogen production,the selections of raw materials,and the methods of increasing hydrogen production efficiency are studied in great detail.The main achievements are as below:(1)Combined the characteristics of pulsed discharge in liquid,the effects of the electrode structures,the power supply parameters,the status of alcohol solutions,the electric field effects and the thermal effects on hydrogen production are studied.Meanwhile,the pathways of hydrogen produced by pulsed discharge in alcohols are also analyzed.The results are as follows:In connection to the electrode structures,the needle-12 needles,needle-balls configurations have great performance on hydrogen production,the needle-plate configuration is fit for basic researches,and the needle-net configuration is more suitable for practical applications and mechanism analysis because the produced gas can be directly exported through the net electrode to prevent being consumed;In the aspect of the power supply parameters,the increase of injected energy or discharge frequency can increase hydrogen yield,but injected energy is the more important influence factor;In terms of the status of alcohol solutions,the pathways of hydrogen production can be directly affected by the initial concentration of ethanol solution that hydrogen yield is highest with the initial ethanol concentration of 45%.While the volume of ethanol solution can influence the discharge characteristics thereby affecting the hydrogen yield that hydrogen yield is higher with the solution volume of 500mL;the electric field effects have little impact on hydrogen production,and the enhancement of thermal effects can decrease the hydrogen efficiency of hydrogen production.In regard to mechanism analysis,the main productions contain hydrogen,carbon monoxide and methanol when the discharge is initiated in 50%ethanol solution.(2)The metals with low electrons work function are applied in hydrogen production from alcohols by pulsed discharge.The reactor is optimized and the energy efficiency of hydrogen production is further increased.The results are as follows:The injected energy could be increased when the metal with low electrons work function is used as plate electrode.Then,electron temperature and density can be enhanced leading to the increase of ·H,so hydrogen yield is certainly increased.In addition,electron temperature and density are also calculated in this paper,which can provide reference to further researches.The electron temperature and density can reach 24000K,7.5 X 1018cm-3 respectively.(3)Pulsed discharge in alcohols combined with photocatalysis is also studied that the light emitted by discharge can be effectively used and the hydrogen yield can be further increased.The results are as follows:The use of TiO2 photocatalysts can increase the hydrogen yield and decrease the energy consumption.Hydrogen yield and energy consumption are 1.55L/min,0.45kWh/m3 respectively when TiO2 coated non-metal is used in the discharge process.The increase of hydrogen yield attributes to the larger specific surface area of the catalysts.While with TiO2 coated Ag,percentage concentration of hydrogen is higher,which can reach 78%owing to the high work function of Ag.Meanwhile,energy conversion efficiency is over 100%,which confirms the method is feasible.In addition,this work proves that the increase of ·H is the main reason of hydrogen yield increasement.(4)Hydrogen production from alcohol distillery wastewater by pulsed discharge is investigated.It aims to find suitable raw materials for hydrogen production.The results are as below:Pulsed discharge in liquid can realize the resourceful treatment of alcohol distillery wastewater and hydrogen production.In terms of organic removal,COD removal can be achieved over 40%in 15min treatment and the biodegradability of the wastewater can be also increased.As for hydrogen production,the flow rate,the percentage concentration,the yield of hydrogen can reach 80mL/min,49%,146 mL/gCODremaved respectively in 30min treatment.Meanwhile,the flow rate of hydrogen is increased about 4 times compared with the ethanol solution with the same ethanol concentration.These phenomena show its advantage compared with other work.In addition,the mechanism of hydrogen produced from alcohol distillery wastewater by pulsed discharge is also studied.The results illustrate that the mechanism of hydrogen production and organics removal are different in different region of the reactor.