【作者】 郭成龙；

【导师】 朱恂；

【作者基本信息】 重庆大学 ， 动力工程及工程热物理， 2013， 博士

【摘要】 氢能具有燃烧性能好，清洁，高效等优势，被认为是理想的能源载体之一。光合细菌能利用水和简单的有机物作为底物将太阳能转换成氢能，减少了二氧化碳的排放并实现了废物的处理，是一门新兴的生物能源技术。然而，利用光合细菌产氢过程中存在产氢速率慢与光能转化效率低等问题，因此，该技术现在还处于实验室研究阶段，与工业规模化生产还有很大的差距。为了提高光合细菌的产氢性能，将生物膜技术与光合细菌制氢技术相结合便成为了一条有效的途径。在利用光合细菌生物膜降解有机物制取氢气的过程中，培养液中的有机底物需先从溶液的主流区通过扩散作用进入到生物膜内，之后，有机底物被光合细菌生物膜代谢降解，最终生成的氢气和二氧化碳等代谢产物逆方向传输到溶液的主流区。由此可见，生物膜内的传质过程对光合细菌生物膜产氢性能有着十分显著的影响。本课题将以光合细菌生物膜制氢技术为背景，针对光合细菌生物膜复杂的结构形态特性，通过构建的板式光合细菌生物膜反应器产氢系统，研究了不同生长时期、流速和底物浓度等操作条件对光合细菌生物膜形成的影响，应用激光共聚焦显微镜及三维重构技术获取了生物膜的结构形态。通过对由激光共聚焦显微镜技术获取的生物膜孔隙及活性细胞的分布情况，建立了光合细菌生物膜反应器内含有生化反应的底物传输及降解模型，预测了不同操作条件下的生物膜内底物分布情况及反应器的底物降解特性。此外，为提高光合细菌生物膜的产氢性能，本文通过光纤技术的引入，光纤复合粗糙表面的构建及非饱和挂膜方式的应用，对光合细菌生物膜反应器内光分布特性，生物持有量和成膜特性进行了强化研究。主要获得以下结论：①采用激光共聚焦显微镜及三维立体重构技术，研究了光合细菌生物膜在成膜过程中结构形态的变化，探讨了底物浓度和流速对光合细菌生物膜结构形态的影响。实验结果发现：随着挂膜启动时间的增加，光合细菌生物膜的孔隙率不断降低，生物膜的结构越发致密。同时，过低的底物浓度会限制光合细菌生物膜的生长，降低生物膜的生物量浓度；而过高的底物浓度则导致光合细菌生物膜的结构更为疏松。此外，由于剪切力的作用，光合细菌生物膜在高流速下更易产生局部脱落的现象。②采用由激光共聚焦显微镜技术获取的生物膜孔隙及活性细胞的分布情况，建立了光合细菌生物膜反应器内含有生化反应的底物传输及降解模型，获得了不同操作条件下反应器内的底物分布和降解特性。实验结果表明：模型计算结果与实验值有较好的吻合性。在pH值为7，光照强度为6000lx，温度为30C的条件下，光合细菌生物膜活性最高，底物降解性能最好，此时，生物膜内的底物浓度最低，氢浓度最高。③提出了弥散光纤束光合细菌生物膜反应器，应用光纤材料作为光导管，强化反应器内光分布的均匀性，进而提高反应器的产氢性能。实验结果表明：弥散光纤束光合细菌生物膜反应器的产氢性能均随水力停留时间与进口底物浓度的增大呈现出先升高后降低的趋势。在水力停留时间为12h，进口底物浓度为50mmol/L的工况下，反应器的产氢速率和光能转化效率达到最大值，分别为12.1mmol/m~2/h和23.3%。④构建了弥散光纤复合粗糙表面，通过反应器比表面积的增加，提升了反应器单位体积的生物持有量。实验结果表明：复合粗糙表面的构建强化了光合细菌生物膜反应器的产氢性能。同时，20天的连续运行实验还证实了带有弥散光纤复合粗糙表面的光合细菌生物膜反应器产氢系统具有良好的稳定运行性。此外，在进口底物浓度为60mmol/L，流量为30mL/h，进口溶液的pH值为7.0，温度为30℃的最适工况下，反应器的产氢速率，底物降解速率，底物降解效率和光能转化效率分别达到1.75mmol/L/h,10.8mmol/L/h,75.0%和9.3%。⑤利用液相区内微生物迁移到达固体基质表面的概率与液相区厚度成反比的概念，提出了在非饱和液相条件下光合细菌成膜，以期强化成膜特性，缩短成膜时间。实验结果表明：光合细菌在非饱和液相条件下形成光合细菌生物膜是可行的、有效的。同时，与饱和液相中形成的光合细菌生物膜相比，非饱和液相条件下形成的生物膜的结构更为致密，成膜所需的时间更短。在饱和液相条件下进行产氢性能实验时，非饱和液相中形成的光合细菌生物膜由于结构相对致密，产物(氢、二氧化碳和挥发性有机酸等)和底物的传输阻力均相对较大，产氢性能较差；在非饱和液相条件下进行产氢性能实验时，由于饱和液相条件下形成的光合细菌生物膜的结构疏松，使得生物量浓度较低，产氢性能较差。更多还原

【Abstract】 Hydrogen is one of the ideal energy carriers because it has numerous advantages ofexcellent combustion performance, cleanness and high efficiency. Photosyntheticbacteria can convert solar energy into hydrogen using water and simple organiccompounds as the hydrogen sources, and enable carbon dioxide reduction and wastetreatment, therefore, the technology of hydrogen production by photosynthetic bacteriaas an emerging bio-energy technology. At present, however, this technique is still in thestage of laboratory research and lags behind the industrial scale due to the slowerhydrogen production rate and lower light energy conversion efficiency. In order toimprove the performance of hydrogen production by photosynthetic bacteria, thecombination of biofilm technique and hydrogen production by photosynthetic bacteriais an effective way. In the process of the degradation of organic matter to producehydrogen by biofilm with photosynthetic bacteria, firstly, the organic substrate in theculture solution diffuses into the biofilm from the bulk liquid, and then, the organicsubstrate are degraded by biofilm with photosynthetic bacteria, at last, the generatedmetabolites, such as hydrogen and carbon dioxide, are is transmitted back to the bulkliquid. Thus, the process of mass transfer within the biofilm has a very significant effecton the hydrogen production performance of the biofilm with photosynthetic bacteria.In this study, focusing on the technology of hydrogen production by biofilm withphotosynthetic bacteria, the effect of different operational conditions including growthstages, flow rate and substrate concentration on the substrate distribution andmorphology characteristics of biofilm with photosynthetic bacteria were investigatedthrough the developed system with flat plate biofilm photobioreactor for hydrogenproduction. Base on the process of mass transfer in flat plate biofilm photobioreactor,the distribution of the pores and the cells were obtained through the treatment ofmicrostructure images of biofilm with photosynthetic bacteria obtained by the confocallaser scanning microscopy, and then the mass transfer and biochemical reaction kinetictheory were utilized for the development of the transport model of the flat plate biofilmphotobioreactor to predict the characteristics of the substrate degradation of thephotobioreactor and the substrate distribution within the biofilm under differentoperational conditions. In addition, in order to improve the hydrogen production performance of the biofilm with photosynthetic bacteria, in this work, the lightdistribution characteristics, biomass concentration and the biofilm formation propertieswere enhanced through the introduction of optical fiber technology, the development ofcomposite surface and the applications of biofilm formation under the nonsaturatedliquid phase. The main results were summarized as follows:①The change of morphology of biofilm with photosynthetic bacteria wasinvestigated in the biofilm formation stage, and the effect of the operational conditionsincluding the substrate concentration and flow rate on the morphology of biofilm withphotosynthetic bacteria was explored. The experimental results showed that: with theincrease of start-up time, the porosity in the biofilm with photosynthetic bacteriareduced and the structure of biofilm became denser. Moreover, the undersizeconcentration of the substrate limited the growth of biofilm with photosyntheticbacterial, reducing the biomass concentration of the biofilm; the oversize concentrationof the substrate led to looser structure of the biofilm. In addition, due to the influence ofthe shear force, biofilm with photosynthetic bacteria is easy to partial loss inhigh flowvelocity②Based on the process of mass transfer in the flat-panel biofilm photobioreactor,the distribution of pores and cells in the biofilm were found out by the treatment ofmicrostructure images of biofilm with photosynthetic bacteria obtained using confocallaser scanning microscopy, thereby the effects of operational conditions including lightintensity, temperature and pH on the transport and degradation characteristics ofsubstrate in flat-panel biofilm photobioreactor were analyzed using the transport modelof flat-panel biofilm photobioreactor constructed based on theory of mass transfer andbiochemical kinetics. Results showed that the modeling consequence could fitexperimental value well. The biofilm activity of photosynthetic bacterial was the highestand the degradation performance was the best at pH of7, illumination intensity of6000lx and temperature of30℃, at which condition, the substrate concentration wasminimum and hydrogen concentration was maximum.③An optical fiber bundle biofilm photobioreactor was developed. In this design,the optical fiber was used as the light conduit to increase the uniformity of light in thephotobioreactor, enhancing the hydrogen production performance of photobioreactor.The experimental results revealed that the hydrogen production performance of theoptical fiber bundle biofilm photobioreactor first increased and then decreased with the increases of hydraulic retention time and substrate concentration. At the hydraulicretention time of12h and the substrate concentration of50mmol/L, the maximumhydrogen production rate and the light conversion efficiency were12.1mmol/m~2/h and23.3%, respectively.④An optical fiber with additional rough surface was developed to enhance thespecific surface area of photobioreactor, enhancing the biomass per unit volume of thephotobioreactor. The experimental results revealed that the development of additionalrough surface enhanced the performance of hydrogen production of biofilmphotobioreactor with photosynthetic bacteria. Moreover, it was also confirmed that thedevelopment of the additional rough surface in the hydrogen production system causedan excellent stable operation of by the continuous operation experiments. In addition,when the substrate concentration was maintained at60mmol/L，flow rate was at30mL/h，the pH value was at7.0，and the temperature was30℃, the maximum hydrogenproduction rate, substrate degradation rate, substrate degradation efficiency and lightconversion efficiency were1.75mmol/L/h,10.8mmol/L/h,75.0%and9.3%,respectively.⑤The biofilm with photosynthetic bacterial formed in an unsaturated liquidphase condition was proposed to enhance the characteristics of biofilm formation andshorten the time of biofilm formation using the notion that the probability of themicroorganism migration from liquid region to the surface of solid matrix is inverselyproportional to the thickness of the liquid region. The experimental results verified thatthe biofilm with photosynthetic bacteria formed in the unsaturated liquid phasecondition was feasible and effective. In addition, compared with the biofilm withphotosynthetic bacterial formed in the saturated liquid phase condition, the biofilmformed in the unsaturated liquid phase condition possessed the more dense structure andthe relatively short time required for the biofilm formation. When the performance testwas performed in saturated liquid phase conditions, due to the relatively dense structure,the transfer resistance of the substrate and products (hydrogen, carbon dioxide andvolatile organic acids) in the biofilm formed in the unsaturated liquid phase condition islarger, lowering the performance of hydrogen production, however, when theperformance test was performed in unsaturated liquid phase conditions, the relativelyporous structure of the substrate in the biofilm formed in the saturated liquid phasecondition led to the lower biomass concentration, lowering the performance of hydrogen production.更多还原