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چكيده انگليسي :

Enhancement of Hydrogen Production from Rice Straw using Combined Chemical Pretreatment Marjan Nassirpour m nassirpour@ce iut ac ir September 17 2013 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language PersianSupervisor Hamid Zilouei hzilouei@cc iut ac irAbstractLignocellulose a widespread biopolymer in the world is considered as one of the most importantcarbon sources especially for bioenergy production because it can be converted into variouschemical compounds by biological processes Rice straw is one of the largest quantities oflignocellulosic crop residues in the world especially in Asian countries and Iran The problem withusing rice straw like other lignocellulosic materials is its high resistance to enzymatic andbacterial attacks which shows the importance of pretreatment step before fermentation In thisstudy the potential of biological conversion of rice straw to hydrogen through anaerobic digestion AD process was investigated The modified municipal anaerobic sludge was used as inoculum Heat treatment of the sludge at 85 C for 45 min was employed to modify sludge and preparemicrobial inoculum through inactivation of non spore forming hydrogen consumingmicroorganisms and selection for hydrogen producing spore forming bacteria Experiments werecarried out in 118 ml serum bottles in batch mode The mesophilic anaerobic digestions wereperformed and produced gases were analyzed by gas chromatography with thermal conductivitydetector The pretreatment process of rice straw in order to increase its biological conversion tohydrogen included two chemical steps First step was the heating of rice straw in 10 w w ammonia solution for 30 and 60 min at 90 120 and 150 C to remove lignin The best result wasobserved at 120 C for 60 min 33 1 lignin removal The second step was hemicellulosehydrolysis and cellulose crystallinity reduction using dilute phosphoric acid 0 5 and 3 at121 C for 60 min Increasing the acid concentration leaded to increase the sugar content of liquidfraction from combined pretreatment that was easily fermentable carbon source for the initialgrowth of the bacteria in H2 production Experimental results indicated that the combinedpretreatment process significantly enhanced the digestibility of rice straw for anaerobic digestion toH2 production than the pretreatment methods using only ammonia solution Combined and one steppretreatments improved the hydrogen production yield up to 82 2 and 52 4 respectively compared to that of untreated one Scanning Electron Microscopy SEM was used to study themorphological changes of the fiber structure of alkaline and combined pretreated rice straw Thesmooth rigid and highly ordered structure of untreated rice straw which is one of the maincharacteristics of the lignocelluloses was disrupted after the alkali pretreatment After the acidicpretreatment the surface of the straw became very unsmooth and wrinkled which is a sign that thecrystal structure of the straw has been more destroyed Moreover FTIR spectroscopy was used todemonstrate the physical structure and changes in the functional groups of rice straw after alkalineand combined pretreatments The Crystallinity Index CI of the samples was calculated usingFTIR spectra It was 0 48 0 42 and 0 4 for untreated alkali pretreated and combined pretreatedrice straw respectively The data showed that both treatments reduced the CI of the strawcompared to untreated one that might be an important factor to improve the hydrogen yield Keywords Rice straw biohydrogen lignocellulose pretreatment anaerobic digestion

نصيرپور، مرجان

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