多级进气多节隔板平板式光生物反应器数值模拟研究

发布时间：2018-05-15 12:36

本文选题：多级进气 + 光生物反应器　；参考：《中国海洋大学》2015年硕士论文

【摘要】：微藻在生物能源、环境保护、食品、保健品及医药等领域具有巨大的潜在应用价值。然而微藻培养的反应器性能不佳一直制约着微藻规模化发展。传统光生物反应器的优化设计及放大方法研发周期长,成本大,不能全面研究反应器内部的流场特性。近年利用计算流体力学(CFD)进行微藻培养光生物反应器研究尽管有很多弥补传统方法的优点,但因刚刚兴起仍存在大量空白。本文针对微藻培养领域主流的平板式光生物反应器,在前人基础上提出了多级进气多节隔板反应器的结构设想,并利用CFD技术对该新型反应器的混合、传质和传光特性进行了相对系统研究,具体结果如下。首先,采用ANSYS Fluent商业软件,构建了多级进气多节隔板平板式反应器计算模型,采用Eulerian-Eulerian多相流模型和PBM模型进行耦合模拟计算,模拟结果与实验测量结果对比验证了本文所建立模拟模型的可行性与可靠性。多级进气反应器上段和中段隔板局部气含率、局部液相矢量速度受通气率的影响较大,其下段性能参数受通气率的影响较小：其湍动能在升液区呈双峰结构分布,在降液区湍动能分布较为平缓。而后,通过CFD模拟计算对比了普通(A)、多节隔板(B)、多级进气多节隔板(C)三种反应器的流场流动与传质特性。结果表明,在一定的通气率下多级进气反应器在气含率、液体平均速度、湍动能、液相传质系数等性能评价参数较前两种反应器分别有很大提高,其中通气率在0.8 vvm时,反应器C中的气含率较反应器A、B分别提升52.63%和39.11%,通气率在0.4 vvm和0.6 vvm时,反应器C的kLa值较反应器B分别提高36.16%和11.27%。进而,利用多相流模型和PBM模型耦合的方法,对影响该新型反应器混合传动、传质性能的气泡特性进行了进一步的研究。反应器气泡直径分布等气泡特性参数结果表明,在反应器高度390 mm上,反应器C的Bin-0体积分数较反应器B降低了32.79%：反应器B内大于6 mm气泡直径体积占总体积分数为8.58%,而反应器C为0.54%。上述结果表明反应器C能有效降低气泡聚并,其中气泡分布良好,这将有利于相间传质。结合CFD模拟计算结果与藻类传光规律,本文对比分析了三种反应器的传光特性。结果表明,反应器C较反应器B增加了反应器内光照方向径向混合强度,反应器C较反应器B在光区的径向速度提高了28.25%,在光区平均停留的时间有所缩短,光暗循环的周期也相对比反应器B缩短了]9.63%,加快反应器内微藻的在光区和暗区的光暗循环频率,加快了微藻闪光效应,有助于微藻生长。最后,通过CFD模拟对反应器C的内部结构参数(隔板的位置(Ar/Ad)、隔板上沿距液面的距离(h0)和隔板间隙的长度(D))进行了优化分析。结果表明,液相体积传质系数和光区的径向速度随Ar/Ad值的增大而降低,整体混合情况在Ar/Ad为0.5时效果较好；整体的混合性能和光区的径向速度随h0增加而增加,当ho为40 mm时反应器的传质性能较好；随着隔板间隙的距离增加,ATK和光区径向速度逐渐增加,而反应器的传质性能在隔板间隙为15mm时达到最大。综上所述,反应器C较其他两种反应器在混合、传动和传质性能上有很大的提升,降低反应器内气泡的聚并现象,优化气泡分布,提高闪光效应。反应器内部结构参数对混合、传质、传光的影响分析结构,为平板生物反应器的设计及优化提供新思路和方向。
[Abstract]:Microalgae have great potential application value in the fields of biological energy, environmental protection, food, health care products and medicine. However, the poor performance of microalgae has been restricting the development of microalgae. The optimization design and enlargement of the traditional photo bioreactor have long period and high cost, and can not fully study the internal reaction inside the reactor. In recent years, the study of microalgae culture photo bioreactor using computational fluid dynamics (CFD) has many advantages to make up the traditional methods, but there are still a lot of blanks due to the rising of the traditional method. In this paper, a multilevel intake multi section baffle reaction is proposed on the basis of the mainstream plate type bioreactor in the field of microalgae culture. The structure of the device is envisaged, and the CFD technology is used to study the mixing, mass transfer and transmission characteristics of the new type reactor. The specific results are as follows. First, the multi intake multi section baffle plate reactor calculation model is constructed with the ANSYS Fluent commercial software, and the Eulerian-Eulerian multiphase flow model and the PBM model are used for coupling. The simulation results compare with the experimental results to verify the feasibility and reliability of the simulation model established in this paper. The local gas holdup in the upper and middle section of the multistage inlet reactor is greatly influenced by the ventilation rate, and its lower performance parameters are less affected by the ventilation rate: its turbulent kinetic energy is in the lift. The distribution of the region is in Shuangfeng, and the turbulent kinetic energy distribution in the drop zone is relatively slow. Then, the flow flow and mass transfer characteristics of three kinds of reactors are compared by CFD simulation. The results show that the gas holdup, the mean velocity and turbulence of the multistage intake reactor at a certain ventilation rate are at a certain rate of ventilation. The performance evaluation parameters such as the mass transfer coefficient of liquid phase are greatly improved than those of the first two reactors. When the ventilation rate is 0.8 VVM, the gas holdup in the reactor C is 52.63% and 39.11% higher than that of the reactor A, B respectively. When the ventilation rate is 0.4 VVM and 0.6 VVM, the kLa value of the reactor C is increased by 36.16% and 11.27%., respectively than the counter reactor B, and the multiphase flow is used. The coupling method of the model and PBM model is used to further study the bubble characteristics that affect the mass transfer performance of the new reactor. The bubble diameter distribution and other bubble characteristic parameters show that the Bin-0 body integral of the reactor C is 32.79% lower than that of the reactor B at the reactor height of 390: the reactor B is more than 6 within the reactor B. The total volume fraction of the MM bubble diameter is 8.58%, and the C of the reactor is 0.54%.. The result shows that the reactor C can effectively reduce the bubble aggregation and the bubble distribution is good. This will be beneficial to the mass transfer. The light transmission characteristics of the three reactors are compared and analyzed in this paper. The results show that the reaction is a reaction. The results show that the reaction is a reaction. The radial mixing intensity in the light direction in the reactor is increased by the device C than the reactor B, the radial velocity of the reactor C is increased by 28.25% compared with the reactor B in the light region. The time of the average stay in the light region is shortened, and the period of the light dark cycle is also shorter than the B of the reactor B, and the light dark circulation frequency of microalgae in the light and dark areas of the reactor is accelerated. At last, the internal structure parameters (Ar/Ad) of the reactor C (Ar/Ad), the distance from the liquid surface (H0) and the length of the gap between the separators (D) were optimized through the simulation of the internal structure parameters of the reactor. The results showed that the mass transfer coefficient of the liquid phase and the radial velocity of the light region increased with the Ar/Ad value. The overall mixing situation is better when Ar/Ad is 0.5. The overall mixing performance and the radial velocity of the light region increase with the increase of H0. When the ho is 40 mm, the mass transfer performance is better. With the gap gap increasing, the radial velocity of ATK and the light region increases gradually, while the mass transfer performance of the reactor is 15mm when the gap gap is 15mm. To sum up, the reactor C is better than the other two kinds of reactors in mixing, transmission and mass transfer performance is greatly improved, reducing the coalescence of bubbles in the reactor, optimizing the bubble distribution and improving the flash effect. The structure parameters of the reactor internal structure are analyzed for the influence of mixing, mass transfer and transmission, and the design of the plate bioreactor and the design of the reactor. The optimization provides new ideas and directions.

【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：Q949.2

【参考文献】