Knowledge Management System Of Institute of process engineering,CAS
|Thesis Advisor||郑诗礼 ; 张洋|
|Place of Conferral||北京|
|Keyword||局部气含率 气液混合 自吸桨 总体气含率|
气液两相混合广泛应用于冶金、化工领域，如湿法冶金，生物发酵，矿物浮选，污水处理，食品工业等。当前尽管有大量与气液两相混合相关的报道，但气液混合局部特性的研究较少，气体的高效利用以及气液混合体系气含率的预测方面仍存在着诸多不足。本文基于当前气液混合体系研究的基本现状，研究了气液两相混合搅拌体系的局部特性，建立了气体高效利用方法，提出了气液混合搅拌体系总体气含率的预测模型，主要研究进展如下： 1.研究了搅拌设备结构及操作条件对气液混合体系局部特性的影响规律。结果表明，气含率径向分布的差别主要集中在近壁和搅拌桨中心轴位置，设备结构及操作条件对中心及近壁位置的气含率有明显影响。 2.设计了一种新型自吸式搅拌桨，并对其性能进行研究，结果表明，与传统自吸式搅拌桨相比，新型自吸式搅拌桨吸气能力提高一倍，吸气临界转速降低50%，能耗降低50%，气体分散能力提高80%，气泡尺寸较传统搅拌桨更小，可达到微米级别。3.建立了搅拌体系总体气含率的物理及数学模型，并得到预测关联式：载气和气体完全分散状态时，εtotal = 6Vs +0.32PV0.56Vs；气泛状态时，εtotal=ε0=6Vs其中常量系数量纲分别为：s/m，m2·s/W；将本模型应用于DT+PDT和PDT+PDT两种组合桨，结果较为合理，其总体气含率表达式为：εtotal=6Vs+χPV0.56Vs，其中χ与搅拌桨类型有关；建立了预测新型自吸式搅拌桨总体气含率的关联式：ε=ε1=77.78Np-1.65 (NP < Npc) 和ε=ε2=0.007535(PV -b) (Np = Npc ,0.007535量纲为m3/W)，在研究范围内，临界功率数Npc= 1.35~1.55，b与搅拌桨类型有关，取值为200W·m-3 和680W·m-3。
Aeration of liquid are widely applied in the chemical industries, such as fermentation, mineral flotation, metallurgy, food processing. Nowdays, there are lots of literatures related with the gas-liquid system, but the researches related with the local property of the gas-liquid systems, the efficient utilization of the gas and the reasonable prediction of the total gas holdup in a gas-liquid stirred vessel are still poorer, and there exists much shortage to be covered. Based on the fact mentioned above, in the present article the reseach is concented on the local property of the gas-liquid system, the efficient utilization of the gas and the prediction of the total gas holdup in a liquid-gas stirred vessel. The contents involved with are as follows:1. The effect of the components constituting a stirred vessel and the operating conditions on the gas dispersion is investigated in the present article . It is concluded that there exists obvious difference in local gas holdup in the center of the stirred vessel and close to the wall of the stirred vessel. The components and operating conditions influences the total gas holdup by means of changing the local gas holdup in the center and close to the wall.2. In the present article, a novel self-inducing impeller is designed. Compared with the traditional self-inducing impellers, the gas-inducing capacity of the novel impeller is one time more than that before, the critical speed decreases to 50% of that before, the energy consumption decreases to 50% of that before and the capacity dispersing the gas in liquid reaches 180% of that before. The novel impeller produces a larger pressure drop in the vicinity of the impeller.3. A model is developed to predict the total gas holdup in a gas-liquid stirred vessel, and a function concerned with the total gas holdup is acquired as follows: (1) εtotal =ε0=6Vs for the flooding condition, (2) εtotal = 6Vs +0.32PV0.56Vs for the loading/completely dispersing conditions. The model is suitable for the impellers of DT+PDT and PDT+PDT, and the expression of the total gas holdup is εtotal=6Vs+χPV0.56Vs, in which χ is a parameter related with the type of the impellers. Besides the total gas holdup in a stirred vessel with a self-inducing impeller is investigated as well and is expressed by ε=ε1=77.78Np-1.65 and ε=ε2=0.007535(PV –b,（the dimension of 0.007535 is m3/W）), which are applied in Np < Npc and Np= Npc respectively. b is a constant dependent on the critical power input. In the present study the critical power number, Npc, is 1.35~1.55, and b is 200W·m-3 and 680W·m-3.
|范兵强. 气液混合搅拌体系气体分散强化及高效利用研究[D]. 北京. 中国科学院研究生院,2016.|
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