【作者】 李刚；

【导师】 张全国； Qinglin Wu；

【作者基本信息】 河南农业大学 ， 农业生物环境与能源工程， 2008， 博士

【摘要】 本论文是在国家“863”计划项目“中小型太阳能光合生物制氢系统及生产性运行研究”(项目编号:2006AA05Z119)、国家自然科学基金项目“光合生物制氢体系的热效应及其产氢机理研究”(项目编号:50676029)的资助下完成。化石能源的日渐枯竭及其使用所带来环境污染问题迫使人们开发新的清洁可再生能源以满足社会可持续发展的需要,氢能因能量密度高、燃烧无污染且利用形式多样而被公认为未来主要的能源载体形式,以氢能使用为核心的“氢能经济”和“氢能社会”发展模式是人们对未来能源使用技术的憧憬。生物制氢是利用微生物自身代谢释放氢气的过程,其产氢条件温和,环境友好且原料来源丰富而被认为是未来氢能生产的主要形式。在各类生物制氢技术中,光合细菌制氢不仅有较高的产氢能力,其还可以利用多种有机废弃物作为产氢原料,实现氢能生产和废弃物处理的双重目标而成为制氢技术研究的热点。光合细菌制氢是光合细菌在光照条件下将有机质转化为氢气的生理代谢过程,光合细菌制氢反应器的开发是光合细菌制氢技术研究从实验室向实际生产转化的关键环节。面对日益增长的氢能市场,开发具有连续生产能力的光合细菌制氢反应器成为实现光合细菌制氢产业化生产的基础条件。论文在总结现有光合细菌制氢反应器发展现状的基础,结合光合细菌产氢的基本特性,提出了大型光合细菌连续制氢反应器设计的技术途径,研制出了以太阳能为主光源、LED为辅助光源的太阳能光合细菌连续制氢试验系统,系统的试验运行为光合细菌连续制氢反应器的开发提供了参考和依据。论文的主要研究成果如下:(1)在对现有光合细菌制氢反应器比较研究的基础上提出了内置光源多点分布式的光合细菌制氢反应器的设计方法。内置光源形式可改变采光面作为反应器结构材料所带来的反应器容积受限和保温问题;多点分布的点光源布置形式可以解决反应器容积受限,使反应器的内部得到均匀光照;太阳能作为主光源和辅助人工冷光源的使用可有效降低反应器的运行成本。(2)照明光纤可以实现太阳光远距离向反应器的柔性传播,同时还可以滤除太阳光中对光合细菌生长的有害辐射。在各类照明光纤的比较中,多芯塑料聚合物光纤不仅可以满足复杂路径下光传输的要求,其还能实现反应器内多点布光的要求。在人工冷光源的选择试验中发现,光合细菌在黄色发光LED(Light-Emitting Diode)下的生长和产氢的效果要优于其它对照组,黄色发光LED可以用作光合细菌连续产氢的辅助光源以弥补太阳能因周期性和不稳定性变化所带来的消极影响。(3)反应器顶部空间中不同初始气体成分虽然会对光合细菌的生长和产氢带来一定的影响,但少量空气的存在并不会对光合细菌的产氢产生明显的抑制作用。对于连续运行的光合细菌制氢反应器的设计来说可以不使用惰性气体对顶空气体进行置换,但其顶部空间应小于反应器容积的1/3以上。(4)研制出了太阳能光合细菌连续制氢试验系统,该系统由反应器本体、太阳能集热换热单元、太阳能聚光传输单元、太阳能光伏转换单元、气体收集与储存单元、自动控制单元等6部分组成。反应器采用折流式结构设计不仅可以满足反应器内部不同空间中布光要求,同时实现反应物在流动过程中自搅拌效果。反应器本体由8个结构相同的独立隔室组成,其设计容积5.76m3,有效工作容积为5.18m3;反应器内部共布置228根玻璃布光管,满足了反应器内部均匀布光的需要;试验系统采用太阳能真空管集热器为反应器提供热量维持反应液温度恒定,太阳能真空管集热器面积为6m2,热水箱容积1.3m3;换热器采用不锈钢三角形翅片管式换热器,其基管直径为φ20mm,换热器换热面积为8.6 m2;太阳能聚光器采光面积2.7m2;太阳能电池板容量为120Wp,蓄电池容量为180Ah,满足系统2d的工作要求。(5)不同消泡剂对光合细菌的生长和产氢影响的试验表明:在试验所选择的消泡剂中,菜籽油对光合细菌的生长和产氢不存在抑制现象,且具有较强的消泡能力,其经济添加量为0.05%,过高则会引起产氢量下降。(6)太阳能光合细菌连续制氢试验系统的启动试验表明:当以纯葡萄糖为单一产氢底物时,需要补充(NH4)2SO4、NaCL、KH2PO4等基础营养物质并在进料时追加30%以上的活性菌体才能满足光合制氢反应器连续稳定产氢的要求。(7)以葡萄糖为底物的运行试验表明:底物浓度对反应器的稳定运行和产氢具有明显的影响,在相同试验条件下系统的总产氢量随着浓度的增加而增加,试验在3%的葡萄糖浓度下获得了最大产氢量;当进料浓度超过4%后,由于高浓度葡萄糖的快速降解导致反应器内溶液迅速酸化使产气率下降。(8)不同水力滞留期对光合细菌产氢的影响表明:短的水力滞留期可以减少中间产物对后继反应的抑制,但过短的水力滞留期则导致原料的利用低下降,甚至出现原料不完全降解的现象;长水力滞留期条件下虽然可以提高原料利用率,但代谢产物在局部空间中的长时间停留将会对菌体生长产生抑制,并引起产氢率下降。试验在水力滞留期为36h时获得的最高产氢率为4.225m3/m3·d。(9)利用不同粪便作产氢底物进行的试验表明:在试验所选择的几种畜禽粪便中,牛粪最适宜用作光合细菌产氢的底物,其在黑暗好氧条件下经过5～7d的预处理可以达到最佳产氢效果,试验在其COD为7000mg/L时得到的最大产氢率为0.56 m3/m3·d,过低的粪便浓度由于可转化物质减少导致产氢降低,过高的浓度则因光线在溶液中穿透性较差导致光合细菌无法得到足够光照而引起产氢下降。更多还原

【Abstract】 This paper was supported by National“863”high-tech research projects "Research on small and medium-sized bio-hydrogen systems by photosynthetic bacteria with solar energy and its working characteristics" (NO. 2006AA05Z119) and National Natural Science Foundation“Research on thermo effect of bio-hydrogen systems by photosynthetic bacteria (PSB)and the mechanism of hydrogen production by PSB" (NO. 50676029).With the growing depletion of fossil fuel and environmental pollution caused by fossil fuel, people recognized it is necessary to search for clean renewable energy resources to meet the demands of economic development and social progress. Hydrogen is considered as a clean and efficient energy carrier because it has high energy density, produces only water after combustion and can be used as different forms, (such as combustion directly, fuel cell). It is dreamed to develop "hydrogen economy" and "hydrogen society" under widespread use of hydrogen as main energy source in the future.At present, hydrogen production mainly comes from fossil fuels, which is a high energy consumption process and easily causes environmental pollution. It is inevitable that the depletion of fossil fuel will put it to an end. However, bio-hydrogen production is considered to be the main approach to get hydrogen in the future because as a process of microbial metabolism it can be run in normal temperature and has rich source of raw materials. Among the various technologies for bio-hydrogen production, hydrogen production by PSB becomes a focus due to the use of the organic waste as substrates and high conversion yields, which serves as energy supply and waste treatment.PSB can convert organic matter into molecule hydrogen under anaerobic condition with light. The development of photobioreactor is the key link putting hydrogen production by PSB into market from lab research. What’s more, with the growing market demand, the development of continuous photobioreactor is the basic condition for the industrialization of hydrogen production by PSB.The design idea to develop continuous large-scale photobioreactor by PSB was put forward in the paper based on the survey of literatures. A continuous photo-bioreactor of hydrogen production by PSB was designed successfully, which use sunlight as the main light source and LED as the auxiliary light source.Main research results of the paper are as following:(1) Built-in illumination and multi-point light sources distribution in reactor are applied. Built-in illumination can overcome the limitation of reactor materials and light supply, which makes it easier to have heat preservation for the reactor and provide a large room as much as possible. Multi-point light sources distribution model guarantees all space in the reactor to get enough light. Meanwhile, it is an effective way to decrease the running cost using sunlight as a main light source and artificial cold light source as auxiliary light source.(2) The long-range transfer of sunlight to the internal reactor would be achieved by the illuminating optical fiber, by which harmful radiation to PSB in sunlight would be filtered. Compared with other types of optical fiber, the multi-core plastic polymer optical fiber has many advantages, and it could not only transmit light in complex path, but also help to realize the multi-point light distribution in reactor. It is essential to choose artificial cold light source to make up the shortcomings of solar energy resulting from its cyclical and instability to keep continuous working. From the result of experiment, light-emitting yellow LED (Light-Emitting Diode) was chosen as the auxiliary light because it is better than other treatments for the growth and hydrogen production of PSB.(3) Although the initial gas components in headspace of reactor would affect the growth and hydrogen production of PSB in a certain extent, a small amount of air in headspace of reactor has no significant inhabitation for hydrogen production. Thus, replacement of the air in reactor with inert gas can be ignored in the continuous photo-bioreactor design, which demands the volume of headspace should be less than 1/3 of the reactor volume.(4) A continuous photo-bioreactor of hydrogen production by PSB was developed, which includes the reactor, the solar heat collectors and heat exchanger unit, sunlight focus and transmission unit, solar photovoltaic unit, gas collection and storage unit and automatic control unit.The baffled structural of the photobioreactor can arrange the illumination in different space of the reactor, as well as realize reactant mixed and stirred during its flow. The design volume of reactor is 5.76 m3; and the working volume is 5.18 m3. 228 glass tubes were arranged in proportional spacing in reactor, which were used to keep the optical fiber and LED out of liquid. Solar vacuum tube collector, 6m2, was used to provide heat for the reactor, and the volume of heat water tank is 1.3 m3. Stainless steel finned tube heat exchanger was used in the reactor, the diameter of tube isφ20mm, and the exchange area is 8.6 m2. The surface of sunlight focus equipment is 2.7 m2. In order to provide electricity for 2days need, solar cell capacity was designed for 120Wp and battery capacity for 180Ah.(5) Research showed that rapeseed oil was better than other defoamers, which did not suppress the growth and hydrogen production of PSB, and had a strong anti-foaming capacity. The economy adding amount of rapeseed oil was 0.05 %, which would form a thin layer on the surface in the reactor.(6)The start experiment of the photobioreactor showed it was necessary to add nutrients such as (NH4)2SO4、NaCL、KH2PO4 and only if a supplement more than 30% of inoculums could keep the photo-bioreactor producing hydrogen steadily when only using glucose as a single substrate for hydrogen production.(7) The effect of glucose concentration on hydrogen yields and stable operation of the reactor was significant. Under the same experimental condition, the hydrogen yield increased with the increase of glucose concentration, the highest hydrogen yield was got at 3% glucose. But the phenomenon changed when the glucose concentration was more than 4%, since the rapid degradation of high concentration glucose would lead to acidification of the solution in the reactor, which is harmful to PSB and decreases the activity of Nitrogenase. However, the average content of hydrogen in the production gas was kept in the same levels with different substrate concentration, but it had changed in different apartment in the same concentration.(8) Different HRT tests showed that the short HRT could reduce the inhibition to the following reaction, but too short of HRT will decrease the utilization of raw materials, even cause incomplete degradation. Although extending the HRT is better for improving the utilization, the longer residence of byproduct will decline the hydrogen production rate. In the test, the maximum hydrogen production rate is 4.225m3/m3·d when the HRT was kept at 36h.(9) Different livestock and poultry dejecta were tested as substrates in hydrogen production; the result showed the cattle dejecta with pretreatment is suitable for producing hydrogen than pig dejecta and chicken dejecta. Cattle dejecta treated for 5~ 7days under dark and anaerobic condition can achieve the optimal results. In the test, the maximum production rate of hydrogen was 0.56 m3/m3·d at 7000mg/L COD with treated cattle dejecta. The production of hydrogen reduced when the solution at a lower concentration due to shortage of the material which can be used by PSB as substrate, but too much higher concentration will effect light penetration and prevent PSB from absorbing enough light energy to meet the demand of electron transport process.更多还原