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微藻规模培养补碳与混合强化研究
其他题名Carbon dioxide supply and mixing intensification technics in mass culture of micro-alga
苏贞峰
学位类型博士
导师丛威
2009-05-26
学位授予单位中国科学院过程工程研究所
学位授予地点过程工程研究所
学位专业生物化工
关键词微藻培养 补碳 气液传质 光生物反应器 培养液混合 闪光效应
摘要微藻利用阳光和CO2合成有机物质并放出氧气,在人类食品、保健、医药、环保和生物炼制领域具有广阔的应用前景。目前,微藻大规模培养技术的开发成为研究热点。降低微藻培养成本、提高微藻产量是规模化培养技术的重点。本文针对目前微藻培养过程中存在成本高、藻细胞光能利用率低的问题,主要从以下两个方面展开研究:通过对二氧化碳在碱性溶液中的吸收特性的考察,设计出了一种气液传递装置,该装置可以大大提高二氧化碳吸收率、从而降低培养成本,该装置兼具对培养液中抑制微藻细胞生长的过高浓度的溶解氧脱除功能;实验考察了培养液混合强度对微藻产量的影响,利用计算流体力学的方法对培养液混合强化技术进行研究,对设计的两种平板结构进行流动混合模拟。在上述两方面研究的基础上构建了微藻平板式光生物反应器规模化培养系统,并对其进行了相应的评价。 首先进行了二氧化碳气体在弱碱性溶液中的吸收特性研究,实验考察了常温下液面高度、气体浓度、Na2CO3溶液浓度、气体流量对二氧化碳吸收速率和吸收率的影响。发现整个吸收过程中吸收阻力基本恒定;液面高度、气体流量对二氧化碳吸收影响较大:液面高度升高,吸收速率下降而吸收率增加,气体流量增加,吸收速率会提高,但是吸收率会降低。 在实验基础上设计出了一种新型补碳装置,考察了补碳装置的气液传递性能,对装置的二氧化碳吸收体积传质系数、溶解氧脱除体积传质系数分别进行了测定;测定以及计算结果表明该补碳装置具有良好的气液传质性能,能够有效地向培养系统中补加碳源,并能将培养液中抑制藻细胞生长的溶解氧及时排除。 在平板式光生物反应器中进行螺旋藻培养,考察了平板光生物反应器厚度、培养液混合强度对螺旋藻生长的影响。实验结果表明:混合强度的增加有助于提高微藻产量,户外高密度培养时,培养液混合强度对微藻产量的影响较室内光限制条件下培养更加明显,面积产量可以提高60%以上;而且,户外培养时混合强度的改变会造成藻细胞生理特性一定程度的改变;理想混合条件下,藻细胞产量与平板光生物反应器厚度无关,厚度1-3 cm为平板光生物反应器的较佳设计参数;平板光生物反应器的厚度越薄,越需要强化培养液的混合以获得较高的产量。 基于强化平板式光生物反应器培养液混合的目的,设计出了圆柱扰流、挡板漩涡两种平板结构,利用FLUENT商业软件对两种平板结构的流体混合、粒子运动轨迹进行了模拟计算。结果表明:圆柱扰流平板结构可以在低流速下实现培养液垂直方向上的混合,强化传质的同时,提高了藻细胞受到的平均光强,有助于产量提高;挡板漩涡平板结构促使培养液在平板表面作漩涡运动,藻细胞随漩涡上下作圆周运动,利于发挥“闪光效应”,提高光能利用率与产量。 以挡板漩涡平板结构作为基本构件设计具有“闪光效应”特点的新型光合反应单元,以设计的补碳装置作为气液交换单元,构建了一封闭式微藻培养系统,相关理论计算表明:补碳装置的传质能力是决定培养规模放大的关键因素,当面积产量为1.6.g.m-2 .h-1,单台补碳装置能够满足24m2培养规模的补碳与脱氧需求,该培养系统的主要优势在于能够发挥藻细胞的“闪光效应”。
其他摘要Micro-alga is capable of utilizing sun light and carbon dioxide to synthesize organic substances, and oxygen is produced at the same time. For potential applications in food, medicine, environment and bio-energy fields, micro-alga culture has attracted increasing attention these years. The emphasis in micro-alga large-scale cultivation technology is to reduce the manufactory cost and improve the productivity. High production cost and low light utilization restrict its development. In this thesis, research was focused on two aspects: A gas-liquid transfer device was designed to enhance carbon dioxide absorption and supply to micro-algae culture. The transfer characteristics of carbon dioxide in the alkaline solution were studied. Another advantage of this device was that it could remove the excessive dissolved oxygen in the culture broth efficiently. In addition, the influence of liquid mixing on alga growth was studied in a set of flat plate photobioreactors, and flow field in designed mix-intensifying structures was simulated with GAMBIT/FLUENT version 6.3. A large-scale culture system of flat plate photobioreactor was designed and evaluated. Firstly, the influences of liquid depth, CO2 concentration, Na2CO3 concentration and gas flow rate on the carbon dioxide absorbing rate and absorptivity were studied. The results showed that mass transfer resistance kept almost constant throughout the absorbing process, and the absorptivity was mostly affected by the liquid depth and gas flow rate. With the increase of liquid depth, the absorbing rate decreased, and the absorptivity increased. The absorbing rate increased and the absorptivity decreased at high gas flow rate. A gas-liquid transfer device with high carbon dioxide absorptivity was designed and its mass transfer ability was investigated. The experimental and calculated results showed that the device mass transfer ability could meet the requirement of carbon dioxide supply and oxygen removal in microalga culture. Spirulina sp. was cultured in a set of flat plate photobioreactors. The influence of flat plate width, liquid mixing intensity on alga growth were studied. The results showed that the alga productivity was enhanced with increased mixing intensity both outdoors and indoors, however, the influence of the mixing intensity on the alga growth in high cell density culture outdoors was more markedly than that in light limited culture indoors, and the increment of 60% was obtained at aeration rate of 0.7vvm compared with that at 0.2vvm in flat plate reactor outdoors. Alga productivity was independent of the flat plate width under the condition of ideal mixing, and flat plate width ranged from 1cm to 3 cm was appropriate for large-scale flat plate photobioreactor. Based on the intensification of liquid mixing in the photobioreactor, two flat plate configurations of column destabilizing structure and baffle swirl structure were designed. The simulated calculations of liquid flow mixing and particle flow field in the two type of flat plate structures were carried out with the software GAMBIT/FLUENT Version 6.3 from ANSYS, Inc., USA. Calculations showed that the destabilizing structure effectively intensified the liquid mixing in vertical direction at low velocity, increased the average light intensity received by alga cell; the baffle swirl structure produced liquid swirls on the surface of the flat plate, resulting in the up and down cycle flow of alga cells, which conduced to “flashing light” effect and helped the alga cells improve light utilization. A flat plate alga culture system was constructed, in which the flat plate photobioreactor unit of baffle swirl structure was designed with the carbon supplying device as gas-liquid mass transfer unit. Calculation results showed that the mass transfer ability of carbon supplying device was the limiting factor for culture scale-up. One carbon supplying device could meet the requirement of carbon supply and dissolved oxygen removal for 24m2 alga culture with 1.6g.m-2.h-1 area productivity. Key words: Micro-alga culture, Carbon supplying, Gas-liquid mass transfer, Flat plate photobioreactor, Culture liquor mixing, “Flashing light” effect.
页数151
语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/1253
专题研究所(批量导入)
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苏贞峰. 微藻规模培养补碳与混合强化研究[D]. 过程工程研究所. 中国科学院过程工程研究所,2009.
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