【作者】 陈春香；

【导师】 马晓茜；

【作者基本信息】 华南理工大学 ， 电站系统及其控制， 2012， 博士

【摘要】 地球上生物质资源相当丰富，开发和利用生物质能不仅可以缓解由于经济发展所产生的能源危机问题，还可以缓解环境问题。然而，第一代生物燃料，主要来自于食用农作物和油料作物，由于生物产量较小、占用耕地，且随着天气变化越来越严重以及经济的快速增长对能源的需求越来越多，促使更多的专家和学者把精力集中到第二代生物燃料—微藻上。与传统生物燃料相比，藻类生物燃料具有油脂含量高、生长速度快、生长周期短、环境适应性强、不占用耕地、具有二氧化碳减排效应等优点，被公认为是在众多生物质资源中最有潜力替代化石燃料的生物质资源。目前世界各国都在致力于微藻能源化利用的研究。本文利用自行改进的干燥箱、以及热重分析仪和微波炉等实验设备对绿色淡水藻的一种—小球藻的特性进行实验研究和理论分析；利用生命周期评价方法，对燃煤电厂采用两种二氧化碳减排技术进行分析和评价，并对回收的二氧化碳用于微藻的培养进行探讨，从中得到多项具有重要意义的结论。通过对小球藻的含水率、干燥厚度以及干燥温度的研究，得出小球藻在不同干燥条件下的干燥规律；十种常用的薄层干燥模型中，Two term model模型的拟合效果最好；小球藻的有效湿份扩散系数为3.36×10^-9～2.23×10^-8m²/s，随着温度的增大，其有效湿分扩散系数增大；小球藻扩散活化能的值为E_a=34.12kJ/mol，指前因子D0=5.30×10^-4m²/s。通过研究微波功率、反应气氛、微波吸收剂、活性炭添加量、固体残渣添加量和原料用量6种因素对小球藻微波热解的影响，得出：在氮气气氛下，产油量最大且单位功率下的失重量也最大的功率为1500W，产气量最大的功率为2250W，残渣产量最大的功率为750W；无微波吸收剂的小球藻热解后产生的生物油产量最大，而添加微波吸收剂后，以活性炭的催化效果最好，氧化钙次之，碳化硅和残渣的催化效果接近；产油量最多的是添加3%活性炭，残渣量最大的是添加10%活性炭，产气量最大且失重量也最大的是添加5%活性炭；热解过程平均升温速率最大且热解产生的生物气的量也最大的是添加5%固体残渣，生物油产量最大的是无固体残渣的纯样，失重量最大的是添加20%固体残渣；产气量最大的小球藻用量为25g；残渣产量最小的小球藻用量为35g，残渣产量最大的小球藻用量为20g，失重量最大的小球藻用量为35g，单位物料固、液、气产量都是最大的小球藻用量为15g。在二氧化碳气氛下，固、液和气产量最大的功率为750W，添加5%碳化硅的产油量和残渣量都最大，无微波吸收剂的产气量最大。通过热重分析仪对纯小球藻与煤的混合热解特性的研究，得出：小球藻与煤的混合物的主要热解区域为172⁶00℃，接近纯小球藻的热解区域，但与煤的不同；小球藻与煤在固固相的混合热解中不存在协同作用，且当温度高于550℃时小球藻阻碍煤的热解；主要热解区域的平均反应速率、最终的残留物产量和混合物中小球藻的含量近似直线关系；采用KAS方法和FWO方法得到混合物活化能的范围分别为320.77～416.01kJ/mol和312.89⁴21.19kJ/mol，其中混合比为5:5时活化能最小。利用热重分析仪，研究小球藻在不同富氧气氛下的燃烧特性，得出：第二阶段是小球藻的主要燃烧段；燃烧的DTG曲线有三个明显的峰，第一个峰的失重速率最大；小球藻主要矿物质含量为硫、钾、磷、氯、镁和钙，矿物质含量对失重速率的影响较小；随着氧气浓度的增加，点燃温度、燃尽温度以及残渣产量都有减小的趋势，而最大失重速率却增大；随着升温速率的增加，点燃温度、峰值点所对应的升温速率以及残留物产量有增大的趋势；在氧气浓度为20vol.%～80vol.%时，小球藻的活化能为134.28～241.69kJ mol-1；小球藻燃烧的最佳氧气浓度为25vol～35vol.%。利用生命周期评价方法，通过对燃煤机组采用富氧燃烧技术与采用燃烧后回收CO₂技术进行发电的能源消耗和污染物排放进行比较和分析，并对回收的CO₂用于微藻的培养进行探讨，得出：采用富氧燃烧技术比燃烧后回收CO₂技术每发电1kWh的生命周期中多消耗0.065MJ的能量，系统的发电效率下降了0.17%；采用富氧燃烧技术发电1kWh的环境影响负荷为9.06382mPET2000，比采用燃烧后回收CO₂技术的负荷减小了4.61%；300MW富氧燃煤发电机组收集的CO₂用于微藻的培养，则每天可生产出1728.99吨的微藻。更多还原

【Abstract】 There is an abundant of biomass resources on the earth. Exploiting and using biomassresources cannot only ease the energy crisis arising as a result of economic development, butalso mitigate environmental problems. The first generation biofuels, which are generated fromfood and oil crops, have some shortcoming, such as small biological yield, the occupation ofcultivated land. Besides, the weather is seriously than before and the rapid economic growthdemand more energy. All above mentioned promotes more experts and scholars to focus onsecond generation biofuels—microalgae.Compared with traditional biofuels, microalgae have high fat content, fast growth andshort growth cycle, a strong environmental adaptability, no occupation of cultivated land andreduction of carbon dioxide emission, etc. Thus, microalgae are recognized as the mostpotential alternative to fossil fuels. Many countries in the world are dedicated to study thetechnology of microalgae biomass.This paper studied the characteristics of a green freshwater microalgae—Chlorellavulgaris by an improved drying oven, thermal gravimetric analysis and microwave heatingequipment, etc. The two types of coal-fired power generation system with CO₂capturetechnology are analysis and evaluation by a life cycle assessment method, and using capturedCO₂captured to cultivate microalgae was explored. Many useful conclusions can be obtainedfrom this paper.Drying characteristics of Chlorella vulgaris under different moisture content, drythickness and the drying temperature were studied. The fitting results of ten common thin-layerdrying model showed that “Two term model” is the best one. The effective moisture diffusioncoefficient of Chlorella vulgaris is3.36×10^-9-2.23×10^-8m²/s. With the increase of temperature,the effective moisture diffusion coefficient is increased. The values of activation energy andpre-exponential factor of Chlorella vulgaris are E_a=34.12kJ/mol and D0=5.30×10^-4m²/s,respectively.The impact of microwave power, reaction atmosphere, microwave absorber, activatedcarbon addition, the solid residue addition and the amount of raw materials on the microwavepyrolysis of Chlorella vulgaris are studied. The results showed that, in N2atmosphere, themaximum oil production and weight loss per unit microwave power were obtained under thepower of1500W; The maximum gas production and residues production were obtained underthe power of2250W and750W, respectively; Without microwave absorbent, the bio-oil production was maximum, after adding microwave absorber, the best catalytic effect wasactivated carbon, followed by calcium oxide; The catalytic effect of the silicon carbide wasclose to the effect of solid residues; Oil production was maximum by adding3%activatedcarbon, residue production is maximum by adding10%activated carbon, the maximum gasproduction and weight loss is obtained by adding5%activated carbon; The maximum averagetemperature rising rate and the bio-gas production is obtained by adding5%solid residues, thelargest bio-oil production is obtained from pure samples, the maximum weight loss is obtainedby adding20%solid residue; The maximum gas production, the smallest residues production,the largest residue production and the maximum weight loss were obtained when using dosagesof Chlorella vulgaris sample were25g,35g,20g and35g, respectively; When the dosages ofChlorella vulgaris sample was15g, the unit solid, liquid and gas production was maximum. InCO₂atmosphere, maximum yield of solid, liquid and gas was at power of750W. Themaximum oil and residues productions were obtained by adding5%silicon carbide, themaximum gas production was obtained with no microwave absorber.Co-pyrolysis characteristics of Chlorella vulgaris and coal were studied by thermalgravimetric analysis. The results showed that the main pyrolysis zone of blends was172-600°C,which close to that of pure Chlorella vulgaris, but different from coal; Chlorella vulgaris andcoal did not exist synergy in the solid-solid phase during their co-pyrolysis. When thetemperature was higher than550°C, Chlorella vulgaris can hinder pyrolysis of coal; Theaverage reaction rate of the main pyrolysis stage and the final residue yield were approximatelystraight line relationship with the content of Chlorella vulgaris in the blend; The activationenergy of blends calculated by KAS method was in the range of320.77-416.01kJ/mol, and byFWO method,312.89-421.19kJ/mol. The activation energy of50%Chlorella vulgaris/50%coal is minimum.The combustion characteristics of Chlorella vulgaris under different oxygenconcentrations were studied by thermal gravimetric analyzer. The results showed that thesecond stage was the main de-volatilization and combustion stage; The DTG curves ofChlorella vulgaris had three obvious peaks, and the weight loss rate was maximum at the firstpeak; The main elemental constituents of Chlorella vulgaris minerals were sulfur, potassium,phosphorus, chlorine, magnesium and calcium, the influence of mineral matter content on theweight loss of Chlorella vulgaris is small; As the oxygen concentration increased, the ignitiontemperature, the final combustion temperature and the residue mass of Chlorella vulgaristended to decrease, while the maximum reaction rates increased; With the increase of theheating rate, the ignition temperature, the weight loss rate of the peaks and the residual mass of Chlorella vulgaris combustion tended to increase; When the oxygen concentrations rangingfrom20vol.%to80vol.%, the activation energy were134.28-241.69kJ mol-1; The optimaloxygen concentration for oxygen-enriched combustion of Chlorella vulgaris was25-35vol.%.Two CO₂capture technologies, oxy-fuel combustion technology and post combustioncapture technology used in the300MW coal-fired power generation units were studied by a lifecycle assessment method. The energy consumption and pollutant emissions of the powergeneration system with oxy-fuel capture technology in a life cycle were carried out, and theresults compared with post combustion capture technology. The CO₂captured from the powergeneration system with oxy-fuel capture technology used to culture microalgae was discussed.The results showed that the oxy-fuel combustion system to generate1kWh of electricity in alife cycle consumed more energy （0.065MJ） than post combustion capture system, and theefficiency of the system was less0.17%than post combustion capture system; Environmentalimpact load of oxy-fuel combustion system to generate1kWh of electricity was9.06382mPET2000, which was less4.61%than post combustion capture system; When CO₂capturedfrom300MW oxy-fuel combustion power generation system was used to cultivate microalgae,the production of microalgae was1728.99t/d.更多还原