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Three Steps of Mixing Process in an Agitated Vessel and Optimum Operational Condition and Design of an Agitated Vessel

搅拌容器混合过程的三步及搅拌容器的最佳操作条件和设计

基本信息

批准号：
08455353
负责人：
OGAWA Kohei
金额：
$ 3.97万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

Though there many investigations on the mixing phenomena in an agitated vessel, the detail of mixing mechanism has not been made clear. In the multi-phase mixing in an agitated vessel which is very significant in the industry, there remain many unsolved problems, especially the mixing mechanism of gas-liquid in an agitated vessel has not been clarified at all.It has been known that there remains concentration distribution of absorbed gas in liquid even after enough time lapsed. There is possibility that this concentration distribution leads the decrease of quality of product. In order to except this concentration distribution, it is indispensable to obtain enough information about mixing process in an agitated vessel. From the experimental restrict the experiment based on impulse response method that the tracer is injected into liquid or the gas is changed step wisely by the tracer gas has been done. However, even the effect of circulation flow or fluctuating flow on the mixing phenomena has not been made clear.In this investigation, at first, the mixing process in an agitated vessel with aeration is paid attention. The mixing process in an agitated vessel with aeration was investigated experimentally by injecting the injecting nitrogen gas by the tracer gas carbon dioxide gas impulsively into the vessel under normal steady operational condition. On the basis of the change in concentration of absorbed tracer gas in water with time, which is measured by using an electrode conductivity probe, the change in the mixedness based on the information entropy with time was calculated. Based on the results it is clarified that the mixing process consists of three steps ; the first step is associated with rise of gas from the nozzle to the impeller, the second step is associated with one circulation of discharge flow from the impeller, and the third step is associated with the circulation flow and fluctuating flow.

虽然对搅拌容器内的混合现象进行了许多研究，但对混合机理的详细研究还不清楚。在工业上具有重要意义的搅拌容器内的多相混合中，存在着许多尚未解决的问题，特别是气液在搅拌容器内的混合机理还没有完全弄清楚。众所周知，即使经过足够的时间，吸收气体在液体中的浓度分布仍然存在。这种浓度分布有可能导致产品质量下降。为了消除这种浓度分布，必须充分了解搅拌容器内的混合过程。从实验限制出发，进行了基于脉冲响应法的示踪剂注入液体或示踪剂气体逐步改变气体的实验。然而，即使是循环流动或波动流动对混合现象的影响也不清楚。在本研究中，首先对掺气搅拌容器中的混合过程进行了研究。在正常稳定运行条件下，用示踪气体二氧化碳气体脉冲注入注入氮气，对充气搅拌容器内的混合过程进行了实验研究。利用电极电导率探头测量水中吸收的示踪气体浓度随时间的变化，计算基于信息熵的混浊度随时间的变化。结果表明，混合过程包括三个步骤；第一步与从喷嘴到叶轮的气体上升有关，第二步与叶轮排出流的一次循环有关，第三步与循环流和波动流有关。