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浅层跑道池培养微藻的驱动和混合强化
Alternative TitleDriving and Mixing Enhancement in Shallow Raceway Pond for Microalgae Cultivation
李岩溪
Subtype硕士
Thesis Advisor丛威  ;  张庆华
2014-05
Degree Grantor中国科学院研究生院
Degree Discipline生物化工
Keyword微藻培养   跑道池   搅拌功耗   实验流体力学(Efd)   粒子图像测速技术(Piv)
Abstract开放式跑道池广泛应用于螺旋藻、盐藻等微藻的工业化生产中,具有技术简单、投资低廉等特点。然而,目前开放跑道池用于微藻培养仍存在搅拌功耗高和微藻产率低的问题。本文针对浅层跑道池流体驱动功耗高的问题,研究明轮桨桨型对搅拌功耗和液体流速的影响,优选不同条件下的桨型;针对浅层跑道池培养微藻面积产率低的问题,用PIV研究安装斜30°垂直挡板和下压形挡板的开放跑道池流场特性,优选池底结构,并用小球藻对池底结构改造的效果进行热模培养验证。 本文首先在2.2 m2小型开放跑道池中分别考察了平叶桨、锯齿型桨、前弯型桨、后弯型桨的桨型对净轴功率、流道内流体流速和桨效率的影响。实验结果表明平叶桨是桨效率最高的桨型。当桨叶没有完全没入流体中,装液深度增加,流速、净轴功率和桨效率都随之增加。当装液深度(5 cm,7.5 cm,10 cm, 12.5 cm,15 cm)和搅拌转速(7、9、11、13、15 r/min)都相同时,净轴功率值从大到小依次为:锯齿形、平叶桨、前弯形桨和后弯形桨。装液深度深为5 cm时,锯齿型桨的净轴功率最大;装液深度高于5 cm时,平叶桨和前弯桨的净轴功率较大。装液深度15cm、转速11 r/min可得最大桨效率为0.5且由平叶桨产生。推导出操作参数和桨型尺寸相关的无因次数群组成的经验公式并可用于之后工业放大。 为了提高浅层跑道池微藻培养的面积产率,在池底安装了不同结构的挡板(斜30°垂直挡板和下压形挡板)。利用PIV进行了不同挡板结构浅层跑道池内流体力学特性的研究。实验结果表明,下压形挡板的流场中可以形成顺时针涡流,涡流范围较大,纵向(光径方向)混合较好。斜30°垂直挡板流场中没有涡流和较大的纵向流动,其对流体的上下混合没有明显的促进作用。未安装挡板的流场没有涡流,只存在随机的纵向上下流动。挡板可以有效减小湍流动能,在流体与挡板碰撞区可产生高的湍动能。未安装挡板高湍流动能区范围比安装挡板的大。下压形挡板可以明显增大流动过程中的纵向流速,其纵向流速大于0.1 m/s的区域最大时是无挡板流场的4倍(12 r/min),1.55倍(15 /min)和1.7倍(17 r/min)。 微藻培养要求藻细胞有良好的纵向混合,下压形挡板和斜30°垂直挡板都可以不同程度地增大流场的纵向流动速度。以小球藻为模型藻种,考察了不同池底结构开放跑道池内小球藻生长状况。在相同条件下培养小球藻,与无挡板池相比,斜30°垂直挡板和下压形挡板都能提高小球藻面积产率。同期对比两种挡板的培养效果,下压形挡板所对应的小球藻面积产率比斜30°挡板平均提高3.76%,说明下压形挡板比斜30°挡板能更好地促进藻液在开放跑道池内的混合。
Other AbstractRaceway ponds are widely adopted in microalgae cultivation, such as the commercial production of Dunaliella Salina and Spirulina Platensis. There are technical superiorities of convenient operation and inexpensive investment for the raceway ponds. However, the high rotational power consumption and low yield productivity still impede the development and application of open raceway pond. Considering the high driving power consumption, the effects of blade configurations on driving power consumption were investigated. Different configurations of blades were applied to select power saving configurations. Considering the low productivity of microalgae in raceway ponds, the hydrodynamics of raceway pond were investigated by particle image velocimetry with and without 30-degree and downward baffles on the bottom. Moreover, the mixing enhancement effects were validated by the cultivation of Chlorella sp. Paddlewheels consume the most part of power during the process of cultivation in open raceway ponds. The configuration of blades directly determines power consumption for paddle wheels. In this work, the effects of blade configurations (flat, zigzagged, forward-curved and back curved) were investigated on the net shaft power consumption, the flow velocity and the paddle wheel efficiency in a bench-scale open raceway pond of 2.2 m2. The effects of blade configurations, the influence of liquid depth from 5 to 15 cm and rotational speeds from 7 to 15 r?min-1 on shaft power consumption (PS), fluid velocity (v) and paddle wheel efficiency (η) were investigated. Results showed that flat blades were the most efficient configuration. Higher liquid depth led to larger v, more PS and larger η, especially when blades were not totally immerged in water. Under the same liquid depth and rotational speed, the value of Ps decreases in the order: zigzagged, flat, forward-curved and back-curved, respectively. The zigzagged blades led to a larger v at the liquid depth of 5 cm, while flat and forward-curved blades drove a larger v when liquid depth was higher than 5 cm. The maximum value of η was 0.50 with flat blades at 11 r?min-1 and 15 cm of liquid depth. Empirical correlations of non-dimensional numbers related to operation parameters and blades geometry for four paddle wheel blades were also proposed. These empirical correlations were well validated by the experimental data and could be employed in the future industrial application. The 30-degree and downward baffles were separately installed on the bottom of 2.2 m2 open raceway ponds. Then flow characteristics with and without baffles on the bottom of open raceway ponds were investigated by the Particle Image Velocimetry (PIV). The PIV results showed that some clockwise eddies were produced by downward baffles. The width of eddies by downward baffles ranged in a high vertical velocity profiles. By contrast, there were no eddies and severe vertical flow in the flow field produced by 30-degree inclined baffles. There were random vertical velocity profiles only in the flow field without any baffles. The two kind of baffles could effectively reduce the turbulence energy. The collision between baffles and flow can enhance the turbulence files. Ranges of velocity profiles above 0.1 m/s for ponds with downward baffles were the largest and were 4 times (12 r/min), 1.55 times (15 r/min) and 1.7 times (17 r/min) of the 0.1 m/s velocity profiles in the traditional pond without any baffles. The Chlorella sp. was applied to testify the effect of downward and 30 degree baffles on the microalgae cultivation. Compared with the empty pond, under the same cultivated conditions, the productivity of Chlorella sp. could be evidently improved both with 30 degree baffles and with downward baffles when the baffles were respectively installed on the bottom of open ponds. Meanwhile, the productivity with downward baffles was improved by 3.76% more than that with 30-degree inclined baffles. The mixing enhancement of downwa
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/15561
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
李岩溪. 浅层跑道池培养微藻的驱动和混合强化[D]. 中国科学院研究生院,2014.
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