平板式微藻光反应器的流场优化及闪光效应

针对微藻闪光效应的特点,开发一种内置交叉导流横向隔板的平板气升环流式微藻光反应器.研究藻液中光衰减规律和通气流量对微藻生长的影响,通过流场数值模拟剖析闪光效应特点,实验对比不同反应器的生物质产量.得到微拟球藻液的光衰减公式,每升藻液的最佳通气流量为05 L·min-1.反应器增加交叉导流横向隔板后,形成一个顺时针和逆时针旋转的交替更迭的大涡流动,加强气液混合和物质传递,在水平光程方向上藻液速度提高到15~22倍,藻液光暗循环周期显著降低到无横向隔板时的1/19.结果表明,快速闪光效应能够明显促进微藻光合生长,最终使微藻生物质产量提高了25%.

Flow field optimization and flashing light effect of flat plate photobioreactor for microalgae growth

According to the properties of the flashing light effect, a novel flat plate airlift loop photobioreactor with inner cross-diversion transverse baffles was developed for microalgae growth. The light attenuation characteristics in microalgae medium and airlift flow effects on microalgae growth were studied. The flashing light effect was analyzed through numerical simulation of flow field and microalgae biomass yields in two photobioreactors were compared by experiments. The light attenuation formula of Nannochloropsis sp. medium was calculated and optimal airlift flow rate of 05 L·min-1 per liter was obtained. When cross-diversion transverses baffles were placed in a flat plate airlift loop photobioreactor, a turbulent flow field with many large eddies that clockwise vortices alternated with anticlockwise vortices was formed in the airlift procedure, which improved gas-liquid mixing and nutrients mass transfer. The horizontal flow velocity of microalgae medium increased to 15~22 times and light-dark cycle period markedly reduced to 1/19 compared to those in the photobioreactor without cross-diversion transverse baffles. The results show that the high-frequence flashing light effect improved microalgae growth and increased biomass yield by 25%．