【作者】 刘振；

【导师】 袁希钢； 曾爱武；

【作者基本信息】 天津大学 ， 化学工程， 2006， 博士

【摘要】 乙醇是用途广、需求量大的化学品之一。随着农业生产的发展及环保的要求,石油资源的枯竭,可再生清洁能源受到了广泛的重视。其中燃料乙醇是当今研究的热点。目前燃料乙醇成本过高还无法与汽油竞争,优化工艺,强化过程是降低成本的重要途径之一。乙醇发酵是典型的产物抑制过程,发酵分离耦合技术,即在发酵过程中同时不断移出产物乙醇,是提高发酵强度的有效手段。为了提高乙醇的在位分离能力,从而提高发酵强度,本文集成闪蒸发酵和汽提发酵两种过程,提出了用于生产乙醇的同步闪蒸汽提发酵过程。实验和理论分析表明,同步闪蒸汽提发酵过程相比汽提发酵和闪蒸发酵,其发酵强度有明显的提高,而且可实现高底物浓度进料,从而节约用水和降低废水处理成本。另外,提高通气量、闪蒸罐进料速度等有关乙醇分离的操作参数,有利于提高发酵强度。实现高温发酵,更有利于显示该过程的优越性。为了实现同步闪蒸汽提发酵过程,本文设计了侧环式反应器,通过增加侧臂,解决闪蒸罐进料液体脱气的问题。本文还对微生物反应动力学进行研究,通过催化反应机理阐述Monod方程的物理意义,并由此引申提出新的细胞生长动力学模型。实验结果表明,新模型与实验值很好的吻合。基于新的动力学模型,建立了同步闪蒸汽提发酵的过程模型,包括对汽提过程的计算进行改进。由实验中发现,通气量的增大对细胞生长呈现先促进后抑制的现象,为此本文提出通气量因子的概念及表达形式,修正存在汽提条件下的细胞生长动力学方程,较好地解决了通气量对过程影响的准确预测问题。本文通过实验,实现了同步闪蒸汽提发酵过程的连续化,利用以上的方法进行计算,模拟预测的结果与连续同步闪蒸汽提发酵的实验值相一致。更多还原

【Abstract】 Ethanol is one of the most widest used and heaviest demanded chemical, which may most possible become the substitute for gasoline. With the development of the agriculture and the requirement of environment protection ,the drying up tendency of gasoline resource, importance has been attached to the regenerate clean energies. Among them, the fuel ethanol is the focus of the research today. Ethanol can’t compete with the gasoline, due to the high production cost, which can be reduced by optimizing the process and intensifying the technology.Ethanol fermentation process is a typical product-inhibiting process. the in-site ethanol separating process processes can efficiently increases the productivity of the fermentation, basing on which a new ethanol fermentation process, coupled with gas stripping and vacuum flash and named as flash-strip fermentation, is proposed in this paper. This process is provided the advantages of both strip-fermentation and flash-fermentation, and improves the ethanol productivity by increasing the in-situ ethanol removal. The experiments and theoretically analysis indicate that the strip-flash fermentation process, comparing with the gas stripping or vacuum flash process, is more effective, and the sugar(substrate) can be fed at high level of concentration, thus the usage of water can be reduced and the cost in liquid waste disposal is cut. In addition, using the thermophilic yeast to raising the fermentation temperature, as well as increasing the gas flux or the rate of feeding to the flash tank can enhance the fermentation efficiency further.To insure that the strip-flash fermentation can work smoothly, a side-looptype bioreactor is designed. By extending side-arms, the problem of deaeration can be resolve.In this paper, the microorganism reaction kinetics is investigated. through using the catalyzed reactivity mechanism to explain the physical meaning of the Monod Equation, a new model of cell growth kinetics was propound. The result in experiments show that the new model inosculate accurately with the experiment value.In this paper, the ethanol fermentation process, which is coupled with gasstripping and vacuum flash, is modeled. Firstly, the method of striping calculation is improved. Secondly, it can be seen that in the experiment, with the increasing of gas flux, the cell growth process will be accelerated at the beginning and restrained later. By seeing the phenomenon, a gas flux factor is put forward and its expression is defined to modify the model of cell growth kinetics under the gas stripping condition. Using the method listed above, the simulation computing result is consistent with the result got in the experiment of the ethanol fermentation process coupled with continuous gas stripping and vacuum flash .更多还原