【作者】 郑毅；

【导师】 马润宇；

【作者基本信息】 北京化工大学 ， 环境工程， 2003， 硕士

【摘要】 盐藻(Dunaliella Salina)是一种高度耐盐的单细胞绿藻,是食品、医药保健、化工和养殖业中具有独特经济价值的微藻。目前盐藻主要用于生产天然 β-胡萝卜素。在许多国家,盐藻细胞的养殖已经实现大面积培养,形成了较大规模的微藻产业。目前生产上采用开放式跑道池培养,盐藻细胞的培养浓度比较低,通常为(4～5)×105 个/mL,且细胞的形体微小,一般为 14×22μm 左右;藻体密度与水相近,因而细胞的采收较为困难。传统的固液分离手段都具有一定的局限。如絮凝沉淀法会污染产品、过滤法分离效率低等。目前工业上主要采用高速离心法,但它能耗高、并且会导致藻细胞破碎。针对现状,本文详细研究了盐藻细胞在不加化学絮凝剂条件下的批次泡载和气浮采收方法,为工业规模采收提供一定价值的基础数据。在批次泡载采收中,主要研究了载气流率、pH 值、藻液进料浓度、分布板平均孔径、破碎盐藻细胞浓度等 5 个因素对泡载采收性能(包括采收率和浓缩倍数)的影响。结果表明:采收性能随载气流率、pH值、藻液进料浓度、破碎盐藻细胞浓度变化均出现峰值,表现出 Lorentz相关性或 Guass 相关性,而分布板平均孔径对采收性能的影响则表现<WP=4>出指数衰减相关性。依此建立起来的过程数学模型与实验结果吻合的很好。在批次气浮采收中,操作条件如藻液的 pH 值、水料体积比、进水速度、溶气压力、溶气时间等均对气浮采收性能有很大影响。采收性能对如藻液的 pH 值、进水速度有峰值,呈 Lorentz 相关性;对水料体积比、溶气压力、溶气时间等 3 个影响因素呈负指数增长相关性。依此建立起来的过程数学模型与实验结果吻合的很好。本文还研究了 pH 对盐藻细胞的疏水性和 Zeta 电位的影响,初步揭示了 pH 值对盐藻细胞絮凝作用的微观机理。说明利用改变 pH 值的方进行絮凝是可行的。更多还原

【Abstract】 Dunaliella Salina is a unicellular species of green alga noted for itshalotolerance. It’s a valuable mircoalga in many fields, including food,health care, chemical engineering and culture. Currently, it’s mainly usedto produce natural β-carotin for commerce. In many countries, the cultureof it has become a large-scale microalga industry. The culture method isthe open racetrack poor, but the concentration of Dunaliella Salina is verylow, which is usually (4～5)×105cells/mL, under this condition. Also,because its body size is rather small (about 14×22μm) and its density issimilar to water’s, the harvesting of it is difficult. There are someshortcomings in traditional separation methods between solid and liquid.For instance, flocculation-precipitation could pollute the production andthe efficiency of filtration separation would be much too low. Todaycentrifugation is the most frequently adopted method for cells harvestingin the big-scale cultivation of Dunaliella Salina. But the energy cost is<WP=6>rather high and cell broken is inevitable during centrifugation, which isdisbeneficial to the down-stream process. According to actualities,harvesting methods, such as foam separation and dissolved air flotationwithout flocculating agent were studied at length in this paper in order toprovide some valuable basic data for industry. In the experiment of batch foam separation, by determining theenrichment factor and total yield of Dunaliella salina cells, the effects ofdifferent operational conditions, such as gas flow rate, pH, initial cellconcentration, average hole diameter of distributing board andconcentration of cracked cells on the feasibility of foam flotation ofDunaliella salina cells were investigated. The experimental results showedthat correlativity between performances, including total yield andenrichment factor and gas flow rate exhibited peak value, viz. Lorents orGuass equation. The same phenomena existed between the performancesand other influential factors, for example the pH, initial cell concentration,and concentration of cracked cells. Otherwise, the phenomenon betweenperformances and average pore diameter of distributing board showedexponent descending correlativity. In addition, math models matchedexperimental results well. Operation factors, such as the pH, rate of feeding water, volume ratioof saturation water to feeding Dunaliella Salina, saturation time andsaturation pressure have important effects on harvesting performances of<WP=7>batch dissolved air flotation. The curves of performances versus the pH orthe rate of feeding water showed peak value, viz. Lorents equation. Butthe curves of performances versus the ratio of saturation water volume tofeeding volume, saturation time and saturation pressure indicated theminus exponent ascending correlativity. According to these conclusions,math models were set up, which match experimental results well. In addition, the effects of the pH on hydrophobicity and Zetapotential of cells were studied. The experimental results revealedpreliminarily micro mechanism of the influence of the pH on flocculationof Dunaliella Salina cells. And these results indicated that the method ofchanging pH to flocculate the cells was feasible.更多还原