Experimental And Theoretical Research On Hydrogenation Of Bio-oil Based On The Technology Of Gas-Liquid Two Phase Discharge

Biomass pyrolysis liquefaction technology has the advantages of simple process,fast reaction,high conversion rate,low cost and so on.It is considered to be one of the most potential technologies of biomass utilization.However,the liquid product of biomass pyrolysis liquefaction,which is known as bio-oil,is a kind of complex organic mixtures,with low calorific value and poor thermal stability,it is difficult to use directly as engine fuel and therefore it needs to be upgraded.As the catalytic hydrogenation can significantly reduce the oxygen content and increase the H/C ratio of bio-oil,the unsaturated components of bio-oil were saturated,so the energy density,stability and volatile of bio-oil significantly increased,and the quality and yield of refined bio-oil are relatively high.Therefore,the catalytic hydrogenation is considered to be the most effective bio-oil deoxidation refining and upgrading method.It has been widely used in the field of refined bio-oil,and has become the focus of the research of refined bio-oil in recent decades.In this research,the current bio-oil catalytic hydrogenation process has the following technical problems,such as equipment and catalyst cost is high,the operation process is complex,the catalyst carbonization coking and the crafting process is not continuous.In order to upgrade bio-oil through hydrotreatment under atmospheric pressure,relatively low temperature and catalyst-free operating conditions,the technical scheme of gas-liquid two phase discharge non-thermal plasma was proposed.Therefore,based on the working principle of dielectric barrier discharge(Dielectric Barrier Discharge,DBD),a set of gas-liquid two phase discharge reactor was designed,the working characteristics of it was also studied,and the influence factors and evolution law of electron density of the gas-liquid two phase discharge were studied by means of emission spectrum diagnostic technique.On this basis,the experiment of hydrorefining bio-oil was carried out by the technology of gas-liquid two phase discharge non-thermal plasma.According to the results of FT-IR and GC-MS,the mechanism of hydrogenation chemical reaction under the condition of gas-liquid two phase discharge was studied.The main work and contents are summarized as follows:(1)The study on design and working characteristics of gas-liquid two phase discharge reactor.Based on the principle of dielectric barrier discharge,a set of gas-liquid two phasedischarge reactor was designed,and the influence of liquid type,liquid height,air gap distance,gas flow rate and operating voltage on the load characteristics of gas-liquid two phase discharge were investigated.Research results indicate that the gas-liquid two phase discharge is similar to the change trend of load characteristics of pure gas discharge.Under the same operating voltage,the equivalent capacitance of dielectric(Cd)of the gas-liquid two phase discharge decreases with the increase of the liquid height and the air gap distance,increases with the increase of the dielectric constant of the liquid,and increases first and then decreases with the increase of the gas flow rate;the equivalent capacitance of discharge gap(Cg)decreases with the increase of dielectric constant and air gap distance,and Cg increases first and then decreases with the increase of liquid height and gas flow rate;the discharge power(P)increases with the increase of the dielectric constant of the liquid,and decreases with the increase of the liquid height,air gap distance and gas flow rate.(2)Hydrogen plasma spectroscopic diagnosis of gas-liquid two phase discharge system.Through the emission spectrum diagnostic technique and Stark broadening calculation method,the impact of operating voltage,gas flow rate and liquid height on the emission spectrum and electron density of the gas-liquid two phase discharge were investigated.Results revealed that when He-H2 mixture and liquid bio-oil two phase discharged,the intensity of emission spectrum characteristic lines of hydrogen H? reached highest,the hydrogen emission spectrum of ? peak intensity and electron density increased with the increase of the operating voltage,and decreased with the increase of gas flow rate and liquid height.(3)Experimental study on gas-liquid two phase discharge hydrofining bio-oil.The effects of operating voltage,gas flow rate and reaction time on the hydrodeoxygenation rate and high heating value of bio-oil were studied systematically by gas-liquid two phase discharge non-thermal plasma technology.The results showed that the deoxidation rate and the high heating value of bio-oil increase first and then decrease with the increase of operating voltage and gas flow rate,and increase first and then stable equilibrium with the increase of reaction time.The deoxidation rate of bio-oil was regarded as evaluation index,operating voltage,gas flow,reaction time were selected as variables,response surface methodology was adopted to optimize upgrading processing parameters,and the optimized parameters of the gas-liquid two phase discharge hydrofining bio-oil were obtained.(4)Research on the chemical reaction mechanism of gas-liquid two phase discharge hydrofining bio-oil.The component and composition of bio-oil and hydrorefining bio-oil were compared and analyzed by means of FT-IR and GC-MS.The results showed that the contents of alcohols,aldehydes,ketones,acids,esters and phenols of bio-oil were decreased,the contents of hydrocarbons were significantly increased,and the high heating value of bio-oil was greatly improved,the oxygen content was decreased,and the physicochemical properties were improved remarkably.