Fast Pyrolysis of Biomass in a Spout-fluidized Bed Reactor--Analysis of Composition and Combustion C

第6卷第2期过程工程学报Vol.6 No.2.2006年4月The Chinese Joumal of Process EngineeringApr. 2006Fast Pyrolysis of Biomass in a Spout-fluidized Bed Reactor-Analysis of Composition and Combustion Characteristicsof Liquid Product from BiomassCHEN Ming-qiang(陈明强), WANG Jun(王君)', WANG Xin yun(王新运), ZHANG Xue-ca(张学),ZHANG Su-ping(张素平)}, REN Zheng-wei(任铮伟}, YAN Yong_-ie(颜涌捷)(1. Dept. Chemical Engineering, Anhui University of Science and Technology, Huainan, Anhui 232001, China;2. Dept Chem Eng. Energy Recourses, East China Univ Sci. & Technol, Shanghai 200237, China)Abstract: In order to gain insight into the fast pyrolysis mechanism of biomass and the relationship between bio-oilcomposition and pyrolysis reaction conditions, to assess the possibility for the raw bio-oil to be used as fuel, and to evaluatethe concept of spout-fuidized bed reactor as the reactor for fast pyrolysis of biomass to prepare fuel oil, the composition andcombustion characteristics of bio-oil prepared in a spout-fluidized bed reactor with a designed maxinum capacity 5 kg/h ofsawdust as feeding material, were investigated by GC -MS and thermogravimetry. 14 aromatic series chemicals wereidentified. The thermogravimetric analysis indicated that the bio-oil was liable to combustion, the combustion temperatureincreased with the heating rate, and only minute ash was generated when it bumed. The kinetics of the combustion reactionwas studied and the kinetic parameters were calculated by both Ozawa Flynn-Wall and Popsecu methods. The results agreewell with each other. The most probable combustion mechanism functions determined by Popescu method are f(x)=k(1-a)2(400-406 "C).f(c)=1/2k(1-a)3 (406~416 C) andf(c)= 2k(1-a32 (416-~430 "C) respectively.Keywords: biomass; pyrolysis; spout-fluidized bed; liquid product; combustion characteristicsCLC No: TQ051.13Document Code: AArticle ID: 1009 -606X(2006)02 0192- -051 INTRODUCTIONfurther investigation.Biomass is a kind of widely distributive and2 PRODUCTION OF LIQUIDenvironmentally friendly resource and the onlyPRODUCT FROM BIOMASSrenewable energy source that can be converted intoliquid fuel. It is becoming a hot topic in the research of2.1 Experimental Apparatusseeking alternative energy source to convert low qualityIn general, pyrolysis of biomass involves threeand low volumetric energy density biomass resource toessential factors of high heating rate, medium reactionhigh quality and high volumetric energy density liquidtemperature (about 500C) and short residence time offuel by developing appropriate liquefying methodl-3) Itthe formed products. A set of experimental apparatusis generally agreed that utilizing the biomass energy forwith a spout-fluidized bed reactor was established basedpreparing liquid fuel through fast pyrolysis is anon the cold flow experiments for the production ofeffective way. Liquid product yield of the pyrolysis ofliquid product from biomass. Its structural parametersthe biomass in a spout-fluidized bed reactor can beand flow sheet are featured of a cylindrical shell withobviously increased, compared with the ordinary150 mm inner diameter, 1 000 mm height of the spacefluidized bed reactorl+. However, the liquid product isover the distributor plate, a 045 mmx3 mm draft tube asvery complex due to the complexity of biomass ina conduit inside the bed, and the shell end is a conicalcomposition andstructure and the complicatedheader (conical angle 90°).pyrolyzing process'sl. In this work, the analysis 0The experimental tests indicated that the concept ofcomposition and combustion characteristics of liquidspout fluidized bed and the designed laboratoryproduct prepared in a spout-fluidized bed reactor wereinsta中国煤化inents for pyolysis ofconducted in order to provide the fundamental data forbionYHCNMHGReceived date: 205-10-11; Accepted date: 2005-12-11Foundation item: National Key Fundamental Research Program (No.2004CCA07300; National Natural Science Foundation of China (No.201 76017); NationalHi-tech Research and Development Program (No.AA514020-02); Anhui Excellent Youth Science and Technology Foundation (No.04044059)Biography: CHEN Ming-qiang(1964-), male, Huainan City, Anhui Province, Ph.D., Professor, research in chemical engineering for energy conversion.第2期CHEN Ming-qiang et al: Fast Pyolysis of Biomass in a Spou-luidized Bed Reactor- Aalysis of Compositio and Combustio Characteristics of Liquid Product from Biomass_gas1. Bunker2. Spiral feerecold watpr3. Spout-fuidized bed不4. Distributor5. Cyclone,6.Ash hopper白、liquid7.8. Condenser,9. Nz clinder,10.11. CO2 cyinderM: Flow meter,脚明T: ThermocoupleP: Pressure gauge910 11V: ValveFig.1 Flow sheet of experimental intallation2.2 Characteristics of Liquid Productdehydration. The total ion flow chromatography isThe product is featured with the followingshown in Fig.2, and 14 organic compounds identifiedcharacters: acidic, dark brown in color, good fluidityareshown in Table 2Theymostlyand homogeneous, viscosity 40 CP (at 40"C), densityoxygen-containing aromatic compounds such as phenol,1.24 g/cm', pH value 2.5, water content in the liquidalcohol, fluorene, aldehyde and ketone.product up to 30%. Table 1 lists the further analyticalresults. Ca, Hs, O。and N(S)d refer to the weight6000percentages of carbon, hydrogen, oxygen and total5000amount of nitrogen and sulfur on dry basis respectively,among which Os was calculated by difference. HHVd,stands for high heating value on dry basis.3000Table 1 Ultimate analysis of the liquid productC.(%) H(%)_ 0(%) N(S)d(%)HHV4 MIkg)200046.20 二6.97 46.070.2620.0110003 COMPOSITION OF LIQUID”1234567891011121314t(min)PRODUCT FROM BIOMASSFig.2 Total ion chromatogram of bio-oilThe liquid product was analyzed by GC -MS afterTable 2 Organic chemicals in the bio-oillo._Molecular formulaMolecular weight___ Residence time (3)___ Content (%)_19-bis[4(<4 nitropbenoxy)pbenyl] fluorineCzHzN2O64.12.772 1.2 benzenediolCcH+O2105.7587.7526-dimethoxy-phenolCaHioO3387.710.54VanillinCyH2Oz528.33.89687.394' byroxy-3'methoxy-acetpenoneCgHnO3669.5582.674,7-dimethyl--decyne 4,7-diolC7H22O29810.073.711.23-rimetboxy-metby-benzeneCnHyzO38210.13.44Butylated bhydroxytolueneCisH2O中国煤化工6.7102,6-dimethoxy-4-(2-propenyl)-phenolCnHI4O33.734-hydroxy-3,5-dimethoxy-benzaldehydeCgHnO4MYHCNMHG4.772 2.6 dimethoxy-4+(2 propeny)-phenolCuHlaO33.6634'-hydroxy-3',S'-dimethoxy-acetophenoneC1oH2O,9612.5584.59_1-(2.4.6-tribydroxypheay)-2-pentanoneCuHh2O。21012.975 _3.54194过程工程学报第6卷4 ANALYSIS ON THERMALslightly lower than that in N2 atmosphere whenCHARACTERISTICS OF THEtemperature is between 200 and 400C. This might bebecause some O2 was combined with the biomass,BIO-OILwhich slowed down the devolatilization process. In thisA thermal analyzer (STD 2960, V3.0F, TA Co.,phase, weight loss was about 25%~30%. WhenAmerica) was used to analyse the thermaltemperature exceeded 400C, the sample weight in O2.characteristics of the bio-oil. The results obtained underatmosphere was quickly reduced to almost zero withinthe following operation conditions are shown inabout 3 min while that in N2 atmosphere was onlyFig.3~6:decreased smoothly and about 13% coke remained(1) N2 atmosphere, 50 mL/min flow rate, and 10when the pyrolysis terminated at 600C. It is apparentK/min heating rate.that in this phase the bio-oil was almost completely(2) O2 atmosphere, 50 mL/min flow rate, 5, 10, 20burned in O2 atmosphere with minute ash lef!-), whileand 30 K/min heating rates respectively.charring took pace in N2 atmosphere. From Fig.4~6 weFigure 3 ilustrates the different behaviors of the bio-oilcan find that peak temperature corresponding to thewhen subjected to heating in N2 atmosphere and O2maximum weight loss rate rises in sequence of 409.55,atmosphere separately. Below 200C TG curves are419.55, 442.37 and 445.71 C as heating rate rises in theoverlapped. This is because in this phase oxidation hasorder of 5, 10, 20 and 30 K/min. The peak temperaturenot occurred and the process is dominated bcorresponding to the maximum exothermal peaks risesvaporization of low boiling point compounds. Bothin the sequence of 426.59, 441.17, 472.29 and 478.26 Ccurves show about 50% weight loss. This indicates thatas heating rate rises in the same order as mentionedhe bio-oil contains considerable amount of easilyabove.volatile components. Weight loss in O2 atmosphere is10025 r8(20 fHeating rate (K/min)15 t...... 1060--2010 t4020300400500600200500 600Temperature (C)Fig.3 TG ofbio-oil (10 K/min)Fig.4 DTA of bio-oil at various heating rate0F90Heatingte (Kmin)800t----10----- 10.70.... 20030望60--- 30.40 F5030 t重403(言202CoF0 100 200 300 400 500 600中国煤化工400500 600MYHCNMHG(C)Fig.5 TG of bio-oil at various heating ratesFig.6 DTG of bio-oil at various heating rates第2期CHEN Migqiag et al: Fast Prolysis of Biomass in a spou fudired Bed Reactor Aoalyis of Copston and Cabusio Carseritis ofigid Podut from Biomas 1955 PYROLYSIS AND COMBUSTIONTable 5 The most probable mechanism functionswith Popescu methodKINETICS OF PYROLYZEDReaction Differential functionBIO-OILscope (C)orderexpression400-4062(1-a)2Both Ozawa Flynn- _Wall methodand Popescu406-4163(12)01-0)416-4302_2(1-0)5methodlol were employed to calculate the pyrolysis andcombustion kinetic parameters and the most probableand thus it makes the presupposition of these twomechanism functions for describing the combustionmethods no longer tenable. The most probablereaction in the temperature scope of 400~430C weremechanism functions chosen with Popescu method foralso selected from the 22 kinetic functions as listed indescribing the combustion at 400~430C are shown inliterature'"".Table 5 which indicates that the combustion is aThe calculated activation energy, E, from bothchemical reaction control process, but reaction order ismethods agrees well with each other and on the wholedifferent in different temperature ranges.the value rises along with conversion ratio increasing(see Tables 3 and 4). When the conversion ratio is less6 CONCLUSIONSthan 0.3, the process is dominated by vaporization of(1) 14 main organic compounds in the liquidlow boiling point compounds, which thus results in lowproduct from fast pyrolysis of biomass at 480C wereactivation value (less than 100 kJ/mol). When theidentifiedbyGC-MS.Theymostlyconversion ratio is up from 0.4 to 0.5, the activationoxygen-containing aromatic compounds such as phenol,energy is about 150 kJ/mol, which corresponds to thealcohol, fluorene, aldehyde and ketone.pyrolysis of some bio oil components. When the(2) Thermal analysis of the liquid product indicatedconversion ratio is from 0.7 to 0.9, the activation energythat it was easy to vaporize and bumn, and the residue ofvalue is also about 150 kJ/mol, which corresponds to theits combustion was minute.combustion of the bio-oil. Surprisingly, when the(3) Thermal kinetics analysis indicated thatconversion ratio is from 0.6 to 0.7, the calculatedactivation energy is either negative or incrediblecalculated activation energy valuesby using(extremely low correlation coefficient). This might beOzawa- -Flynn _Wall method and Popescu method areconsistent with each other. The most probabledue to the multi-type reaction mechanisms co-existingmechanism functions for describing combustion atin this transition phase (from pyrolysis to combustion)400~430C were also selected from 22 kinetic functionsTable 3 Activation energy E calculated withwhich indicated that the combustion was a chemicalOzawa-Flynn-Wall methodreaction control process.__a_E (kJ/mol)0.55.99-0.9945REFERENCE:0.264.56-0.9949[1] Chen M Q. Preparation of Liquid Fuel through Pyrolysis of Biomass-0.9523in a Conduit spouing Fluidized Reactor. (D]. Shangha: East China122.11-0.9246University of Science and Technology, 2003.2-10 (in Chinese).0.5189.95-0.9118-180.1109111[2] Chen MQ, Yan Y J, REN z W, et al. Preparation of Liquid Fuel164.8-0.5136through Fast Pyrolysis of Biomass in a Spuf-luidized Reactor with a182.73-0.9905Draft Tube 0. J. East China University of Science and Technology,155.55-0.99322004, 30(2): 143-147 (in Chinese),[3] Bridgwater A V. 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