Characteristics By Liquid Phase Pinhole Discharge And Its Research In Hydrogen Production From Acetic Acid

The global warming caused by carbon dioxide emissions has seriously affected the sustainable development of human society.In September 2020,my country clearly put forward the goals of"carbon peaking"in 2030 and"carbon neutrality"in 2060.The development of new energy,energy conservation and emission reduction are important means to achieve the dual carbon goal.As a renewable resource,biomass energy has incomparable advantages over traditional fossil energy.Using biomass energy to produce hydrogen is economically feasible and environmentally friendly.In this thesis,acetic acid,an aqueous phase component of bio-oil,was selected as the model compound,and the liquid phase discharge plasma technology was used to produce hydrogen.The results of the study are as follows:（1）To explore the characteristics of liquid phase pinhole discharge,through a series of conditional experiments,the solution conductivity,discharge power and the number of insulating holes on the concentration of active substances（H₂O₂,O₃,NO₂^-and NO₃^-）generated by discharge in water were studied.The research found:When the conductivity of the solution is lower,the discharge is more favorable,resulting in a higher concentration of active substances.That is,when the conductivity of the solution is 50μS/cm,the concentrations of hydrogen peroxide,ozone,nitrite and nitrate are the highest;the greater the discharge power,the higher the concentration of hydrogen peroxide and ozone;when the number of insulating pores is porous,When the discharge is discontinuous and the number of insulating holes is single,it is more conducive to the generation of active substances.At this time,the concentration of hydrogen peroxide,ozone and nitrite is the highest.Secondly,to explore the spatiotemporal characteristics induced by plasma,and use a CCD camera to photograph the discharge process of plasma in water,confirming that the plasma is generated in the bubble,which is in line with the bubble breakdown theory.Finally,the emission spectrum characteristics of pinhole discharge in water were analyzed,and the formation of radicals such as·OH,·H,·O was found,and the lower the solution conductivity,the higher the spectral intensity.（2）According to the characteristics of liquid-phase pinhole discharge,the law and reaction mechanism of hydrogen production by acetic acid decomposition under this discharge form were studied.The results show that:with the increase of the volume fraction of acetic acid,the conductivity of the solution decreases,the volume fractions of H₂ and CO₂ in the gas production components decrease,and the volume fractions of CH₄,CO and other gases increase.With the increase of discharge power,the flow rate of hydrogen production increases,and the energy consumption for hydrogen production decreases greatly.When the electrode spacing is 5 mm,the discharge frequency is 3300 Hz,the number of insulating holes is single,the volume fraction of acetic acid is 65%,and the discharge power is 262 W,the hydrogen production flow rate is1100 m L/min,and the hydrogen production energy consumption is 3.97 k Wh/m³H₂.The greater the discharge power,the higher the energy obtained by the system,which is more conducive to the discharge.With the increase of the discharge distance,the action volume of the plasma becomes larger,but the electric field strength between the two electrodes at the same voltage is weakened,and the energy of the electrons is reduced,making it difficult to decompose the acetic acid molecule to produce hydrogen.Therefore,the gas flow and hydrogen Flow is reduced.Then the emission spectrum of acetic acid discharge and the characteristics of free radicals were analyzed.The results showed that various free radicals,such as·OH,·CH and·C₂,were generated during the discharge of acetic acid.Through the·OH quenching experiment and excluding the influence of the conductivity of the added quencher,it was found that the hydrogen production effect decreased after·OH quenching.It is speculated that·OH radical plays a key role in the decomposition of acetic acid molecules to produce hydrogen.Finally,the reaction path of acetic acid hydrogen production can be divided into:acetic acid,water molecules and high-energy electrons collide with the process of generating free radicals and intermediate products,and then intermediate products and free radicals react to generate gas products,such as H₂,CO,CO₂ and hydrocarbons.This study innovatively proposes the application of liquid-phase pinhole discharge plasma to acetic acid for hydrogen production,and there is no relevant research at home and abroad.The liquid-phase pinhole discharge adopts a plate-hole-plate reaction structure,which effectively separates the power supply and discharge areas and avoids metal electrode ablation.Moreover,the structure can realize discharge in a liquid with higher conductivity,and is suitable for discharging hydrogen in a low-concentration acid solution.As one of the main components of the bio-oil water phase,acetic acid has the characteristics of being rich in water,bio-renewable and environmentally friendly.The use of acetic acid discharge to produce clean energy hydrogen energy is in line with the concept of circular economy,and a good hydrogen production effect is obtained.The research of this thesis provides theoretical support for the application of liquid discharge plasma in hydrogen production from acetic acid.