【作者】 王永忠；

【导师】 廖强；

【作者基本信息】 重庆大学 ， 工程热物理， 2008， 博士

【摘要】 当前能源持续紧张,国际石油价格大幅振荡,不断攀升,能源短缺问题成为困扰社会和经济发展的首要问题,同时化石能源的开采和应用对环境造成了严重破坏,特别是产生的CO2引起的温室效应带来的极端和异常气候变化、氮氧化物和SO2带来的酸雨等问题严重地威胁着地球和人类的可持续发展。我国是一个能源资源相对贫乏的国家,特别是石油、天然气人均资源量仅为世界平均水平的7.7%和7.1%。因此开发可再生的生物能源对于促进可持续社会的发展具有重要意义。在可再生能源中氢能是21世纪的可再生“能源之星”和“最有前景的能源”,并广泛地被认同为化石燃料的潜在替代能源,2007年4月国家颁布能源发展“十一五”规划更明确指出将氢能开发作为我国今后重点的前沿发展技术之一。目前广泛采用的传统制氢方法一方面仍消耗化石能源,另一方面对环境造成破坏,而利用光合细菌将有机废弃物转化为氢能是一种可持续发展的制氢方式。固定化技术是当今生物工程领域中的研究热点,但关于固定化细胞生物制氢反应器中传输特性的研究还极少进行,这方面的研究对于解决固定化细胞技术中的传输限制性问题和光生物制氢中光能利用率低、产氢率低等问题具有重要的理论和实践意义,为固定化技术在生物能源领域的应用奠定一定基础。本课题主要是研究固定化光合细菌在光产氢过程中的底物传输特性及产氢特性。实验创新性地采用双层平板法从长期排放污水的水沟淤泥中筛选、分离纯化出一株具有高产氢特性的沼泽红假单胞菌菌株(Rhodoseudomonas palustris),进行了光波长、光照强度、底物浓度、培养液pH值和培养温度影响下的序批式培养光合细菌产氢动力学实验,根据实验数据拟合得到最大比生长速率关于不同培养条件参数影响的经验关系式,并建立光合细菌生长、底物消耗和产氢动力学模型,模型较好地反映了操作参数对光合细菌生长、底物消耗和产氢动力学的限制性和抑制性影响。实验研究了固定化包埋颗粒产氢和底物消耗特性,建立了固定化包埋颗粒内底物传输与消耗动力学模型,模型预测结果反映了包埋颗粒内底物传输特性,研究结果表明底物主要以扩散方式进入包埋颗粒内,并且沿颗粒半径方向变化底物浓度逐渐减小,包埋颗粒内控制过程主要为生化反应控制过程,提高光合细菌菌种的生化反应速率是提高底物消耗速率的关键。固定化包埋颗粒填充床研究结果表明随进口底物浓度增加,底物在填充床反应器内的代谢逐渐由传输控制转化为生化反应控制的过程,随进口流量增加,传质边界层逐渐减小,外扩散传质阻力逐渐消除,主要由以传输控制为主的过程向生化反应控制的过程转化;随入射光照强度的增加,光能供应逐渐由限制性条件向抑制性条件转变;不同光波长激发光合色素天线系统所引起的激发态不同,产生的光化学效应不同,及最佳产氢速率和底物消耗效率所对应的光照强度不完全相同;随培养液pH值和培养温度升高,填充床反应器产氢和底物消耗行为表现为先增加后抑制现象。固定化生物膜光生物制氢填充床实验研究表明其它条件一定,光照强度较低时,为限制性条件时,光照强度较高时,为抑制性条件。底物浓度为限制性条件时,属于传质控制过程;进口底物浓度为抑制性条件时,为生化反应控制过程。进口流量较低时,主要为传输控制过程;进口流量和进口底物浓度较高时,主要为反应控制过程。本课题在实验研究基础上建立了生物膜光生物制氢中底物传输与消耗动力学模型,分析了影响填充床内质量传递的外界操作因素,模型预测与实验结果取得了较好吻合。同时本课题研究结果表明一定条件下,不同尺度下光合细菌产氢行为表现为以温度为30°C左右或pH值为7.0时产氢速率和底物消耗速率较快,说明温度及pH值主要影响细胞内酶活性。更多还原

【Abstract】 Currently, energy resource remains in strain, and the international price of oil keep on rising, so the primary problem affecting the development of society and economy is shortage of energy resource. Meanwhile, the exploitation and application of fossil fuel bring serious harm to our environment, especially CO2 emitted breeds in the greenhouse effect to induce the extreme change of climate, and the acid rain is ascribed to the emitted NOx and SO2. These pollutants threaten the sustainable development of earth and human being. Nevertheless, in our country falling short of energy resource the amount per capita of oil and natural gas is only 7.7% and 7.1% of word average level. Therefore, the exploitation of renewable bioenergy will hasten the development of sustainable development of society, in which hydrogen named as a promising energy source is a clean and efficient fuel and widely accepted as a potential substitute for fossil fuels by virtue of the fact that it is renewable and does not cause the‘‘greenhouse effect”. And in the 11th Five-Year Plan of energy resource promulgated the exploitation of hydrogen energy will become one of the important and advanced technologies developing. However, hydrogen production by conventional methods needs to consume the fossil energy resource and destroys our living environment, conversely hydrogen production by photosynthetic bacteria (PSB) from organic wastes is renewable. So far, the immobilized cells technology has became hot in biotechnology, but there was little research on the transfer characteristics of immobilized PSB cells in the process of hydrogen production, but the research, which will lay a foundation for application of immobilized cells technology in bioenergy, will favor to solve the problem of limitation in mass transfer of immobilized cell and the problem of low efficiency of light utilization and low rate of hydrogen production.The characteristics of hydrogen production and substrate transfer of immobilized PSB was mainly analyzed in the thesis. First, a strain identified as Rhodoseudomonas palustris with high efficiency of hydrogen production was isolated and purified from sewage sludge. Effect of light wavelength, light intensity, substrate concentration, pH value of culture medium and culture temperature on the kinetics of hydrogen production in batch culture was studied in experiments, And according to experimental data the empiristic formulae on effect of different culture conditions on the maximum specific growth rate were gained. Moreover, kinetic models on biomass growth, substrate consumption and hydrogen production of PSB were respectively established, which reflected the effects of operation parameters in batch culture on the kinetics of growth, substrate concentration and hydrogen production, respectively.The research on characteristics of hydrogen production and substrate consumption in the particle of immobilized PSB was tested, and the mathmatic model on the substrate transfer and consumption in entrapped-particles was studied, which results reflected on effect of parameters in continuous culture on the characteristics of substrate transfe. The research results releaved that substrate was transported into particle by diffusion, and the concentration of substrate in particle decreased with decrease of radius of particle. According to above analyzed the conclusion that the limited process in particles was biochemical reaction was deduced. Therefore, the key of improving biochemical reaction efficiency of the entrapped-particles was to improve the biochemical characteristics of strain of PSB.On the other hand, the results on photo-bio-hydrogen production in packed beds filled with particles of immobilized cells revealed that consumption of substrate in the packed beds would divert to the process limited by biochemical reaction from that controlled by mass transfer of substrate with increasing concentration of substrate or with increasing flux. And light energy became compressed condition from limited condition with light intensity increasing. However, effect of light wavelength on biohydrogen production by PSB was complicated with dealing with light intensity, which indicated that different excited phase of the photosynthetic antennae system was inspired by different light wavelength and that the photo-chemical efficiency changed correspondingly. In addition, the rates of hydrogen production and substrate consumption in packed beds filled with porous medium increased with pH value of culture medium or culture temperature increasing, and then declined with these parameters increasing continuously.Moreover, the research on characteristics of packed-bed with biofilm showed that in certain other parameters, low intensity was limited condition, vice versa, it was impressed condition, and that in limited substrate concentration condition, the metabolism in the pached bed was controlled by mass transfer, conversely by biochemical reaction. Meanwhile, the results revealed that in low flux condition, the metabolic process controlled by mass transfer was obtained, conversely the process controlled by biochemical reaction was gained in high flux and high substrate concentration at inlet. According to experimental results, the model on mass transfer and substrate consumption was founded, in which the operation conditions effecting on mass transfer in biofilm packed-bed were analyzed respectively. And the results predicted by model were accordant with experimental data.Furthermore, the results in the thesis indicated that in all conditions the optimal temperature and the optimal pH value of hydrogen production by PSB was 30°C and 7.0, respectively, which revealed that the culture temperature and pH value affected the activities of enzyme in cells mainly.更多还原