【作者】 李刚；

【导师】 董仁杰；

【作者基本信息】 中国农业大学 ， 农业生物环境与能源工程， 2014， 博士

【摘要】 微藻作为一种新型生物燃料原料的重要来源,具有分布广泛、适应能力强、生长迅速及油脂含量高等优点。利用厌氧发酵液培养微藻,在处理废液的同时还可有效降低微藻生产成本。热裂解是生物质气化和燃料燃烧过程中必不可少的一个阶段,可以将生物质转化为液体燃料或其它高附加值产品。本文优化了厌氧发酵液培养链带藻的高生物量累积工艺；采用热裂解-气相色谱-质谱联用技术,在不同温度下测定了不同培养条件下链带藻的热裂解产物组分变化；对链带藻热裂解过程进行生命周期评价；并对提取油脂后的链带藻残渣的能源化应用潜力进行了研究。本文采用二次正交旋转组合试验设计,建立了链带藻生物量累积与各影响因素间的回归模型。厌氧发酵液培养链带藻的高生物量累积最佳工艺参数组合为：柠檬酸铁铵添加量为0.0348g/L、K2HPO4添加量为0.1584g/L、MgSO4·7H2O添加量为0.489g/L。在该条件下,试验获得的生物量累积为0.777g/L,接近于模型的预测值0.782g/L。分别选择BG11培养基、厌氧发酵液和厌氧发酵液-添加营养元素培养的链带藻为原料(BG11/8-10、ZY/8-10和W/8-10)进行热裂解研究,对一系列总离子流色谱图进行分析的结果表明：三种原料的热裂解产物主要包括脂肪族烃类、芳香族烃类、脂肪酸类、含氮化合物、酚类、多环芳香烃类、酮类、醇类、醛类和呋喃类化合物等。但是较高温度容易导致含氮化合物、多环芳香烃等污染物的大量生成。因此如果利用以上三种原料制备生物油,则其最佳热裂解温度分别是700℃C、600℃C和300℃C。本文利用生命周期评价方法,以1kg链带藻为功能单位,选取能效分析和环境潜在影响为考察指标,分别综合评估了最适温度下1kg BG11/8-10、ZY/8-10和W/8-10的热裂解过程。结果表明,能量转换效率η均大于1,说明三个过程均是有利的；且W/8-10热裂解过程能源转化效率最高,为6.21。三个过程的生命周期环境影响分别为1347.63、1165.67和838.52mPET2000,其中W/8-10热裂解过程对环境影响最低。因此,W/8-10热裂解过程为最佳选择。本文还研究了链带藻提取油脂后残渣的能源化潜力。通过分析其热裂解产物组分及含量发现：产物中不仅含有脂肪族烃类、芳香族烃类和脂肪酸类等潜在能源物质,还包括一些含氮、含氯化合物类、多环芳烃类和极少量含硫化合物等污染物。相比700℃C下热裂解产生生物油的含量(29.3%),8000C时热裂解产生的生物油含量最高,为36.6%。但是800℃C较700℃C多产生了21.4%的污染物。基于较低污染物排放水平和较高生物油产率,链带藻提取油脂后残渣的最适热裂解温度为700℃C左右。更多还原

【Abstract】 Microalgae, which are known as the new source of biofuel production, have such features as extensive distribution, widely adaptability, rapid growth and high in lipid content, etc. By conducting anaerobic digested wastewater (ADW) to cultivate microalgae, not only it is beneficial to the wastewater disposal but also can lower the cost of the algae production effectively. During the process of biomass gasification, liquefaction and combustion, biomass pyrolysis technology is an indispensable procedure, which can convert the biomass to liquid fuel or other valuable chemical products. Current thesis primarily focus on the following four aspects:the optimization of biomass accumulation of Desmodesmus sp. cultivation in ADW; the yield and chemical composition of pyrolysis products of Desmodesmus sp. by Py-GC/MS; the analysis of pyrolysis process of Desmodesmus sp. based on life cycle assessment (LCA); potential energy application of lipid-extracted Desmodesmus sp.Response surface methodology (RSM) was applied to optimize the biomass accumulation of Desmodesmus sp. cultivation in ADW. The optimal biomass accumulation conditions were the additive volume of Ammonium ferric citrate (0.0348g/L), K2HPO4(0.1584g/L), and MgSO4·7H2O (0.489g/L). Under such conditions, the experimental biomass accumulation of Desmodesmus sp. was0.777g/L, which was close to the predicted value (0.782g/L).The pyrolysis-gas chromatographic mass spectrometry (Py-GC/MS) was investigated to determine yield and chemical composition of pyrolysis products of Desmodesmus sp. cultivation in BG11medium, ADW, and ADW-added nutrient elements, respectively (BG11/8-10, ZY/8-10and W/8-10). It was comcluded that the chemical compounds from pyrolysis products of Desmodesmus sp. cultivation in three conditions, which were mentioned above, mainly consisted of aliphatic hydrocarbons, aromatic hydrocarbons, acids, nitrogen compounds, phenols, polycyclic aromatic hydrocarbons (PAHs), alcohols, aldehydes, and furans. However, higher temperature would easily lead to mass generation of nitrogen compounds and PAHs. Therefore,700℃,600℃and300℃were found to be favorable for producing biofuel from BG11/8-10, ZY/8-10and W/8-10.The whole pyrolysis process of1kg BG11/8-10, ZY/8-10and W/8-10under the optimal temperature were evaluated by using the method of LCA, respectively. The environment emissions and energy efficiency were under considerable for the corresponding parametric study. The functional unit was1kg microalgae. It was concluded that the energy conversion efficiency for the three processes were larger than1, which indicated that all the three processes are profitable. In addition, the energy conversion efficiency, which was6.21, of W/8-10was found to be the largest. The environmental impact of the three processes were515.61,449.78and323.68mPET2ooo, among which the pyrolysis process of W/8-10has the lowest environmental impacts. Thus, the pyrolysis process of W/8-10was the optimal selection.It was found that, among the pyrolysis products of lipid-extracted Desmodesmus sp., aliphatic hydrocarbons, aromatic hydrocarbons, and acids can be used as in the potential energy materials; nitrogen compounds, chlorine-containing compounds, and PAHs, and small amount of sulfur-containing compounds functioned in pollutants. Pyrolysis of lipid-extracted Desmodesmus sp. at800℃produced36.61%(the maximum yield) of pyrolysis products, compared to that of29.34%at700℃, but more pollutants (21.42%) were produced in the meanwhile. Under such consideration, a reasonably high yield and minimum release of pollutants temperature (700℃) was found to be optimum for producing bio-oil from lipid-extracted Desmodesmus sp.更多还原