Mechanism And Experimental Study On Hydrogen Production From Co-gasification Of Biomass And Glycerin

In order to enhance the hydrogen production rate and concentration in thegaseous production, the co-gasification of biomass and glycerin from the microscopicmechanism, kinetics and the laboratory experimental study were investigated in thispaper. The co-pyrolysis behavior of biomass and glycerin was studied by the thermalgravity （TG） analyzer. Five different heating rates （2.5℃/min,5℃/min,10℃/min,15℃/min,20℃/min） were chosen to carry out the thermo-gravimetric experiment ofglycerin, biomass and glycerin/biomass mixture. The temperature increased fromroom temperature to900℃by heating furnace in experiment apparatus. Thepyrolysis characteristic curves were analyzed and compared. The quality weightingmethod was used to investigate the coupling action between the component during thetotal co-pyrolysis process of biomass and glycerin. Ozawa-Flynn-Wall method wasused to calculate the dynamics parameters of the pyrolysis of biomass and glycerin.The influence of heating rate and particle size on the devolatilization characteristics ofco-pyrolysis of biomass and glycerin were analyzed.In addition, co-gasification of biomass and glycerin with steam as gasificationagent was carried out at atmospheric pressure in a fixed bed reaction system.Orthogonal experimental design of three factors （reaction temperature, steam flow,glycerin/biomass） and three levels was adopted. The effects of the three factors on thegas composition and calorific value, gas yield, liquid yield and solid yield wereinvestigated.The results show that the co-pyrolysis process of biomass and glycerin is mainlydivided into four stages. The temperature interval of the first stage is from roomtemperature to130℃. The main reaction is the biomass dehydration,depolymerization and glass transition process. The addition of glycerin to the mixtureadvances the pyrolysis process. The second phase temperature interval is130³20℃,and the loss of weight is56%. The TG curve of glycerin and biomass mixture issignificantly lower than the TG pyrolysis curve of cob, glycerin alone, which provesthat the co-pyrolysis is not simple superimposition. The function of mutual promotionbetween them leads to the increase of both pyrolysis rate and depth. The temperaturerange of the third stage is320³90℃, TG curve of mixture is located between biomass TG curve and glycerin TG curve. The temperature of the last stage is morethan390℃, which mainly is the decomposition of lignin.There is a strong synergistic relation between biomass and glycerin during theco-pyrolysis process of biomass and glycerin. The interaction between biomass andglycerin is positive for co-pyrolysis which can advance and speed up the pyrolysisprocess. The range of activation energy of biomass and glycerin pyrolysis calculatedby Ozawa-Flynn-Wall is from67.697to276.112kJ·mol^-1.The orthogonal experiment results indicate that the order of factors whichinfluence the H₂yield is reaction temperature> steam flow> glycerin/biomass （G/B）.The optimal combination is: T=750℃, S=2ml/min, G/B=3:8. The H₂volumetriccontent in the gas product is ranging35.8⁶2.0%. If the gaseous product is used to bethe fuel gas, the optimal combination is: T=650℃, S=1.5ml/min, G/B=3:8.