Hydrogen Generation from Plasmatron Reforming Ethanol

第28卷专辑Ⅱ武汉理工大学学报Vol.28 Suppl.Ⅱl2006年11月JOURNAL OF WUHAN UNIVERSITY OF TECHNOLOGYNov.2006Hydrogen Generation from PlasmatronReforming EthanolYOU Fu-bing, HU You-ping, LI Ge-sheng, GA0 Xiao-hong( School of Energy and Power Engineering, Wuhan University of Technology, Wuhan 430063, ChinaAbstract: Hydrogen generation through plasmatron reforming of ethanol has been carried out in a dielectric barrier discharge(DBD) reactor. The reforming of pure ethanol and mixtures of ethanol-water have been studied. The gas chro-matography (GC)analysis has shown that in all conditions the reforming yield was H2, CO, CH and Co2 as the mainproducts, and with little C. The hydrogen-rich gas can be used as fuel for gasoline engine and other applicationsKey words: hydrogen; plasreform: ethanolCLC number: TQ 116.2Document code: A Article ID: 1671-4431(2006)Suppl. I1-0064-05The increasing concern in environmental and pollution problems and energy shortage crisis implied alarge amount of efforts in the scientific world to develop alternative and renewable sources for decreasing useof fossil fuels, higher overall efficiencies and reducing emissions of harmful chemicals. These changes arelikely to be accompanied by a shift in fuel infrastructure away from gasoline and diesel towards alcohols andhydrogen-rich gases, which are more versatile and cleaner than todays common fuels. Fuel reforming, thechemical conversion of one type of fuel molecule into others, may be an extremely important part of futureenergy and power systems; reforming is also certain to be a key technology for the transitional period between current and future fuel infrastructures. The development of compact, efficient reformers that can bedirectly integrated into fuel supply systems has several possible advantages1) Power devices that have intrinsic fuel restrictions, such as fuel cells, can be brought into use withinthe current fuel infrastructure2)The effect of changes in fuel supply composition on existing vehicles and power plants can be miti-3)Both existing and future power plants can be operated with greater fuel flexibility, allowing for po-ntial emissions reductions at a slight cost in efficiency and complexity4)Hydrogen-rich gases can be supplied as fuel not only for fuel cells, but forfoundatdate:2006-08-23中国煤化工m: The Science and Technology Bureau of Wuhan(20061gty: YOU Fubing(1971-), male, candidate doctor. E-mail: youfb@HCNMHG第28卷专辑ⅡYOU Fu-bing, et al: Hydrogen Generation from Plasmatron Reforming Ethanol65Compared to the developed hydrogen storage technologies, the use of ethanol as an effective storage ofhydrogen is much safer and cheaper. The hydrogen generation technologies from ethanol include steam re-forming, partial oxidation, oxidation steam reforming and ethanol decomposition. The decomposition ofthanol provides a better alternative for the hydrogen production. However, there are some drawbacks withthe catalytic hydrogen production from ethanol: 1) The present ethanol reformers are mostly the packedbed reactors that suffer from problems such as the occurrence of hot and cold spots; 2) There are someproblems during the cold start-up and transients; 3) The catalytic activity and stability still need to be improved)Whereas plasma reforming can provide advantages of rapid response, relaxation or elimination of catalyst requirements. The purpose of this paper is to study on hydrogen generation from plasma reformingethanol1 Characteristics of Non-thermal Plasma TechnologyRecently, there have been investigations on ethanol decomposition using non-thermal plasma. The aimof the plasma is to play a catalytic role by creating reactive species needed for the chemical reaction. Severaldifferent plasma reactors have already been developed in different research groups to reform hydrocarbons bypartial oxidation or auto-thermal reforming 2-4. Only few plasma reactors have however been developed forsteam reforming of hydrocarbons (5.81. Among the different plasma characteristics, we can distinguish twomain categories: thermal plasma and non-thermal plasmaFor thermal plasma, the electrical power injected in the discharge is high and the neutral species andthe electrons have then the same temperature (around 5 000-10 000 K). The temperature in the reactorand the energy consumption are thus very high and the cooling of the electrodes is generally useful to reducetheir thermal erosion. The use of this technology is therefore not relevant in fuel cell application for an efficient production of hydrogen in terms of energy consumptionFor non-thermal plasma, the electrical power is very low(few hundreds watts): the temperature ofneutral species does not change whereas the temperature of electrons is very high(up to 5 000 K). In thiscase, the role of the plasma is not to provide energy to the system but to generate radical and excited speciesallowing initiating and enhancing the chemical reactions. The advantages of using non-thermal plasma areelated to the lower temperature that will result in lower energy consumption and lower electrode erosionsince the cooling of the electrodes is generally not necessary. In addition, thetht of the non-thermal plasma reactors are relatively low, which is very attractive for mobile applicaton-thermal plasma technologies include the corona discharge, the microwave plasma, the gliding arcand the dielectric barrier discharge. The microwave plasma and the gliding arc use a dynamic dischargehich is pushed by the gas flow along the reactor, in contrast, the corona discharge and the dielectric barrier discharge use a static discharge2 Dielectric Barrier Discharge(DBD)中国煤化工CNMHGWe will briefly review old discharges to better place ine dielectric barrier discharge(DBD)section. It is customary to divide plasmas into groups depending on the I-v region of operation, the dor武汉理工大学学报2006年11月nant excitation mechanism, their operating pressure, or the electrode geometry. Energy extracted from anapplied electric field, E, by a charged particle of mass M is proportional to:E121Hence, free electrons will carry the majority of the energy in a plasma compared to ions since the massof ion is further larger than it of electron. When free electrons collide with the molecules of ethanol, themolecules are split into other radical species such as CH3, CH, OH,H,etc.3 Experimental Set-upThe plasma reformer presented in this paper has been designed and developed to work in non-thermalsteam reforming conditions for pressures up to about 60 mmHg and temperature up to about 373 K. The fuel to be reformed is ethanol or the mixture of ethanol and water which is ready before entering the reactorA scheme of the experimental setup is presented in Fig 1. A special non-thermal plasma power is usedwhich voltage and frequency are variable. The voltage can vary from 0 kv to 20 kv, and the frequencyfrom 7 kHz to 20 kHz. The compositions concentration of the reformate gas is analyzed by GC-TCD(GC7900啊@@PasmMOOactor归Fig 1 Schematic of plasma reforming syster4 Results and discussionThe reformat gas is analyzed by GC- TCD. Figure 2 and Figure 3 respectively show the recorded chromatogram corresponding to the two vapor compositions: ethanol and ethanol-water. Table 1 has shown theolume concentration of the compositions in the corresponding reformate gas. The gas chromatography(GC) analysis indicates that in all conditions the reforming yield is H2, Co, CH4 and CO2 as the main products, and with little C2. Moreover, there are some solid C on the inner face of the reformer when the vaporis pure ethanol, but in the mixture ethanol-water the formation of solid C was decreased. According to thedata in Table 1, and disregarding the minority products, the global plasma reactions for pure ethanol andthe ethanol-water can be described according中国煤化工CH3CH2OH→C+CCNMHGCH3CH2OH H2O2C0+4H第28卷专辑ⅡYOU Fu-bing, et al: Hydrogen generation from Plasmatron Reforming Ethanol46420364208642mN81012141618202224262830ig 2 The chromatogram of ethanol reformate gas64208012116182022242628Fig 3 The chromatogram of ethanol and water reformateTable 1 Concentration of ethanol reformed gas compositionCompositionCOCHAChO中国煤化工p(ethanol- watcr )/%58.3723.346.53CNMHG1.36In addition, comparing to the concentration of CO2 in the different reformate gas, the formation of武汉理工大学学报2006年11月CO2 in the mixture of ethanol-water is greatly more I.than it in pure ethanol. Fig 4 has shown the difference Iof the concentration of CO between pure ethanol and sure of ethanol-water. The reason is the water 0.6molecule takes atom O which increases the mole frac- 0.4tion of atom O in the inlet vapor. So the C/O rate inthe mixture of ethanol-water is close to equilibriumFig 4 Comparison of cowhich reduces the formation of solid C in the same time5 ConclusionThis work shows that non-thermal plasma steam reforming of the ethanol at atmospheric pressure is apromising technique for H productionChemical analysis of the outlet gas has been studied. We quantified the reformate gas compositionThus, several species had been quantified: H2, CO, CO2, CH4, C2H2, C2H4, C2H. The mole fractions ofCO2 and the formation of solid C depend on the inlet composition while H2 and CO concentrations remainedconstant. These results show that the optimization of the process is important to keep the balance betweenatom C and O in the inlet vapor, which is our next step work. also a laboratory scaie reactor is a determinant element that should arouse the interest of industries concerned in order to continue investigations onthe possible applications of this technologyReferences[1 Sun Jie, Qiu Xinping, Wu Feng. Research on Catalysts for Ethanol Steam Reforming[J]. Energy&Fuels, 200014(46):11951199[2] Cohn D R, Rabinovitch A, Titus C H, et al. Near-term Possibilities for Extremely Low Emission Vehicles Using OnboardPlasmatron Generation of Hydrogen[J]. Int J Hydrogen Energy, 1997, 22(7): 715-723[3] Sobacchi M G, Saveliev A V, Fridman AA, et al. Experimental Assessment of a Combined Plasma/ Catalytic System forHydrogen Production via Partial Oxidation of Hydrocarbon Fuels[J]. Int J Hydrogen Energy, 2002, 27(6): 635-642[4] Bromberg L, Cohn D R, Rabinovich A, et al. 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