小桐子油制备生物柴油的研究

【作者】 苏有勇；

【导师】 王华；

【作者基本信息】 昆明理工大学 ， 冶金能源工程， 2015， 博士

【摘要】 在全球能源危机不断加剧的情况下,生物能源作为一种理想的可再生能源,越来越受到世界各国的关注。生物柴油是一种对环境友好的“绿色能源”,是石化柴油理想的替代品,对缓解全球面临的能源短缺和环境污染两大问题具有十分重要的战略意义。论文对小桐子油制备生物柴油过程中的相关问题进行研究,重点对制备体系的工艺条件优化、热力学和动力学等进行了深入研究,并在此综合分析的基础上设计了年产300～500吨生物柴油中试生产装置开展中试研究,为小桐子油以及其他原料规模化生产生物柴油奠定基础。(1)针对小桐子油制备生物柴油反应体系缺乏基础热力学数据,开展相关的物性数据估算,建立了基于基团贡献法的物性估算方法和VB编程的物性数据查询系统,为小桐子生物柴油制备体系的热力学、工艺优化以及中试装置设计等方面的研究提供基础数据。(2)采用中心组合旋转设计试验方案并运用响应面分析法优化高酸值小桐子油精馏分水连续气相酯化降酸工艺,获得最优工艺条件,在优化条件下验证试验的相对误差为0.66%,说明利用响应面分析法优化得到的高酸值小桐子油精馏分水连续气相酯化降酸工艺条件是可靠的和准确的在小桐子油和脂肪酸甲酯存在下的甲醇-水二元体系的汽液平衡性质研究结果表明,随着添加在甲醇-水溶液体系中的小桐子油酸值的增加,体系的沸点呈上升趋势,液相中甲醇的摩尔分数也随之增大,而汽相中甲醇的摩尔分数却降低。利用Wilson方程关联不同酸值小桐子油存在下的甲醇-水的温度平均偏差为0.12%、汽相组成的平均偏差为0.16%,说明Wilson模型的推算结果与实验数据吻合良好。经理论计算,在50℃～100℃温度范围内小桐子油混合脂肪酸与甲醇发生酯化反应的△Hθ小于零,标准吉布斯自由能小于零,表明该酯化反应在上述温度范围内自发进行。在此温度范围内的平衡常数基本不变,表明酯化反应基本上是热平衡的,温度对平衡的影响不大。热力学研究结果对高酸值小桐子油进行精馏分水气相酯化降酸工艺提出以下进一步优化建议：在反应物料酸值较高时可适当提高反应温度,随着酯化反应进行可逐步降低反应温度,从而实现提高降酸效率和节约能耗的目的。动力学研究结果表明,在甲醇蒸气通入速率为5.94 L·min-1和催化剂对甲苯磺酸用量为5.0%的优化条件下,高酸值小桐子油精馏分水连续气相酯化降酸反应的动力学方程为：(3)开展超声波强化加压连续酯交换制备生物柴油的反应机理、热力学和动力的研究,得到最优工艺条件：醇油物质的量之比为6.71：1、反应温度为55.7℃、催化剂用量为1.36%、超声波功率密度为0.26W·cm-2和压力0.35MPa,在此优化条件下验证试验的相对误差为-0.52%,说明利用响应面分析法优化得到的超声波强化加压连续酯交换制备小桐子生物柴油的工艺条件是可靠的和准确的。热力学研究结果表明,小桐子油生物柴油和甲醇、甘油和甲醇是完全互溶的,而甘油和小桐子油生物柴油部分互溶,同时小桐子油生物柴油在甘油中的溶解度稍大于甘油在小桐子油生物柴油中的溶解度。采用Aspen Plus模拟软件,用NRTL模型以及UNIQUAC模型关联实验数据,获得不同体系不同温度下的模型参数,调整NRTL及UNIQUAC模型参数后,使用Aspen Plus对小桐子油-小桐子油生物柴油-甲醇-甘油四元体系的相平衡进行预测,结果表明,使用调整后的NRTL模型参数可以很好的预测四元体系相平衡。热力学研究结果表明,在反应初期为了使两相间发生的酯交换快速进行,必须对反应物料进行充分搅拌,这为利用超声波在加压连续酯交换制备生物柴油中的强化作用提供了理论依据。动力学研究结果表明,在醇油比为6.71：1、催化剂用量为1.36%、超声波功率密度为0.26W·cm-2和压力0.35MPa的较优条件下,在40～60℃范围内超声波强化加压连续酯交换制备小桐子生物柴油的反应动力学方程为(4)根据饱和蒸气压的Riedel方程估算了小桐子油生物柴油主要的八种脂肪酸甲酯在不同温度下的饱和蒸气压,各种脂肪酸甲酯的饱和蒸气压随着温度的升高需增加,且在相同温度下随着饱和脂肪酸碳链的增加,饱和蒸气压下降,脂肪酸甲酯中的不饱和碳越多,饱和蒸气压越大,这为生物柴油的载气蒸气精制提供了理论依据。循环载气蒸馏精制小桐子油生物柴油的研究结果表明,在本试验条件下,N2载气流量为5 L·min-1较为合适,在1 60℃～260℃范围内采用分段变温方式操作,可得到纯度达到99%以上的生物柴油产品。(6)小桐子油制备生物柴油的中试生产研究表明,本中试装置可实现生物柴油的连续化生产和甲醇的连续回收利用,原料转化率可达98%左右。生物柴油产品的指标,除氧化安定性外都达到BD100国家标准。从能源消耗来看,本中试装置生物柴油制备的能源消耗较低(电能消耗80-90k·h/吨),但生物柴油精制的能耗偏高(电能消耗700～750kW.h/吨),因此在后续研究中,有必要对精制工艺开展进一步的改进研究。论文的研究成果可为小桐子油规模化生产生物柴油的工艺设计和生产系统设计奠定坚实的基础。更多还原

【Abstract】 With the increasing of acute crisis of global energy, bioenergy as an ideal renewable energy, more and more attention is paid around the world. Biodiesel is an environment-friendly "green energy", an ideal alternative to petroleum diesel, which has great strategic significance for relieving two major problems of energy shortage and environmental pollution that the world is facing. The theoretical and experimental research was carried out about the reaction system of biodiesel produed from Jatropha oil. The optimization of technical condition, thermodynamics and dynamics of system were studied deeply. At the basis of analysis by synthesis, the equipment of pilot-scale production of 300-500t/y of biodiesel was designed and the research of pilot-scale production was carried out. The foundation of production of large-scale is layed for biodiesel from Jatropha Curcas oil and other materials.1) For the lack of basic thermodynamic data of producing biodiesel from Jatropha oil in reaction system. The estimation methods of physical properties is established which based on group bond contribution, as well as, the query system of physical property data based on VB programming is established. The essential data is provided for the research of thermodynamics, the optimization of technical condition of preparing system of biodiesel from Jatropha Curcas oil, as well as the design of the equipment of pilot-scale production.2) The central composite rotating was used to design experiment and response surface methodology was used to optimizing technolgy of reducing acid continuous gas-phase esterification reaction for Jatropha Curcas oil of high acid values. The relative error of verification test is 0.66%in the condition of optimization. The result demonstrates that it is reliable and accurate, the process conditions of continuous reducing acid by gas-phase esterification reaction for Jatropha Curcas oil of high acid values optimized by response surface method.The equilibrium properties of liquid-vapor which was composed of methanol and water in the presence of Jatropha Curcas oil fatty acid methyl ester shows that, the boiling point of the system is rising along with increasing acid value of Jatropha Curcas oil in liquid-liquid system of methanol and water. The mole fraction of methanol in the liquid phase is also increasing in liquid phase but the mole fraction of methanol in the gas phase is decreasing. The average deviation of temperature for methanol-water in the presence of different acid value of jatropha Curcas oil is 0.12%associated with Wilson equation, as well as, the average deviation of the vapor phase composition is 0.16%. These result sated the calculation results of Wilson model is in good agree with the experimental data. Through theoretical calculations, the AHθof esterification reaction is less than zero between methanol with mixed fatty acids from jatropha Curcas oil at a temperature in the range of 50 ℃ to 100 ℃, the standard Gibbs free energy is less than zero indicates that the esterification reaction within the above temperature range may occur spontaneously. In this temperature range the equilibrium constant is substantially constant, it indicates that the esterification reaction is essentially thermal equilibrium, as well as the temperature had little effect on the equilibrium.The suggestion on optimization about the continuous reducing acid by gas-phase esterification reaction for Jatropha Curcas oil of high acid values is followed:the reaction temperature need is increased when the acid values is verry higher of reaction material, and it may is reduced step by step along with the achieve of esterification reaction. Thus it is realized for the purpose of improving of the efficiency of drop acid and economy of energy consumption.The reaearch of kinetic shows that, under optimal technical conditions of the rate of methanol vapor is 5.94L-min-1and the amount of p-toluenesulfonic acid catalyst is 5.0%, the kinetic equation of reducing acid continuous gas-phase esterification reaction for Jatropha Curcas oil of3) The optimization of technical condition, thermodynamics and dynamics of preparing biodiese by continuous transesterification under ultrasonic assistant and pressure were studied in the paper, the optimal technical conditions is followed:6.71:1 ratio of methnol to oil,55.7 ℃ of temperature,1.36%of catalyst dosage,0.26Wcm-2 of power density of ultrasonic and 0.35MPa of pressure. The relative error of verification test is-0.53%in this condition of optimization. The result demonstrates that it is reliable and accurate, the process conditions of preparing biodiese by continuous transesterification under ultrasonic assistant and pressure optimized by response surface method.The result of thermodynamic show that biodiesel and methanol, glycerol and methanol are completely miscible respectively, while glycerin and biodiesel Jatropha Curcas oil are partially miscible. And biodiesel is slightly greater solubility in glycerol than glycerol in biodiesel. With Aspen Plus simulation software, experimental data is correlated by NRTL model and UNIQUAC model. The model parameters could be obtained at different temperatures under different systems. After the model parameters of NRTL and UNIQUAC was adjusted, the quaternary system of Jatropha Curcas oil-biodiesel-methanol-glycerine equilibrium was predicted through using AspenPlus soft. The results shows, the adjusted NRTL model parameters could be used to predict the quaternary system equilibrium.The result of thermodynamic indicates that the reaction material must be fully mixed in the beginning of the reaction, in order to make the speed of transesterification conduction rapidly in two phases. Thus the theoretical foundation could be provided that the invigorating effect of ultrasonic assistant in continuous transesterification under pressure.The reaearch of kinetic shows that, under the optimal process conditions of 6.71:1 ratio of methnol to oil,55.7 ℃ of temperature,1.36%of catalyst dosage,0.26Wcm-2 of power density of ultrasonic and 0.35MPa of pressure, the kinetic equation of preparing biodiese by continuous transesterification under ultrasonic assistant and pressure in the range of 40 ℃ to 60 ℃ is followed:4) The saturated vapor pressure of eight major fatty acid methyl esters in biodiesel from Jatropha Curcas oil was estimated according to riedel equation. The saturated of various vapor pressure fatty acid methyl esters is increased with increasing of temperature. At the same temperature, the saturated vapor pressure is decreased with increasing of saturated fatty acid carbon chain, at the same time, the unsaturated carbon of the fatty acid methyl ester is more, and the saturated vapor pressure is higher. This result provides a theoretical basis for the rectification of boidiesel through distillation methyl esters by cyclic gas. The experiment results show that 5 L-min"1 of the flow rate of N2 would be more appropriate way in this experimental condition. The purity of biodiesel product could be over 99% through operation of egmented heterotherm in the range of 160 ℃ to 260 ℃.5) The pilot-scale production of biodiesel from Jatropha Curcas oil shows that this system could realize achieved continuous production and continuous recycling of methanol, the conversion rate of raw materials is up to about 98%. The trait of production has all reached the national standards of BD100except for oxidation stability. From the point of view of energy consumption, the energy consumption is lower in the phase of the preparation of biodiesel (power consumption is 80 to 90kW·h/t), but the high energy consumption of biodiesel is existed in purification (power consumption is 700 to 750kW·h/t). It is necessary to carry out further improvements of refining process.The research results of this paper can provide a reliable theoretical basis for the design of technology and production system in large-scale production of biodiesel from Jatropha Curcas oil.更多还原