Local drop size variation in an agitated vessel

The local droplet diameters were measured at two positions inside the circulation region of a stirred tank. The Sauter mean diameter near the top of the vessel was always 1.4 times greater than the one just outside the impeller region for rotational speeds of 250, 300, 350 and 400 rpm and for hold-up fractions of 0.01, 0.025 and 0.05. The drop size distributions at a hold-up fraction 0.01 had one mode for all impeller speeds studied and at both positions. At higher hold-up fractions the distributions usually were bimodal.     

搅拌槽内多层组合桨对液-液分散特性的影响

以水-煤油及水-环己烷为体系,研究Rushton涡轮桨(RT),半椭圆管涡轮(HEDT)及翼形轴流式桨(CBY)的6种不同组合桨的液-液分散特性。测定了不同输入功率时分散相体积分率沿轴向及径向的分布。结果表明:当搅拌槽内液位与槽径之比达1.5,在相同输入功率时,三层桨的液液分散性能优于两层桨,功率准数较低的CBY组合桨在输入功率0.8kW/m~3时,槽内的轴向及径向分散相体积分率达到稳定的均匀分布。而功率准数较大的RT组合桨需要在输入功率1.8kW/m~3才能达到槽内分散相的均匀分布。     

搅拌槽内的液-液临界分散

在φ391mm搅拌槽中,分别采用双层Brumagin桨、双层三叶后掠式桨和双层A310桨与7种内构件相组合,在无乳化剂下对油水比(质量比)分别为1∶1.5,1∶2.0的煤油-水体系的液-液临界分散进行了研究。从工业实用的角度出发,对前两种桨找到了一种可替代“轻液挡板”的小挡板及其安装方法:内冷管上均布4块小挡板,B/D=0.08,插入液面深度为0.2D。在φ188mm搅拌槽中,于全挡板条件下,以歧化松香皂为乳化剂,分别采用3种不同几何参数的双层Brumagin桨对油水质量比为1∶1.5的煤油-水体系的临界分散进行了研究。结果表明,与无乳化剂情况相比,液-液临界分散转速(N_c)下降30％～40％,临界分散功耗(P_(cv))下降53％～66％;桨径减小会使N_c和P_(cv)增加。     

Types of dispersion in agitated liquid-liquid systems

This paper describes phase inversion phenomena in stirred vessels. In particular, the effects of mechanical operating-parameters on dispersion types were investigated. It was found that when the impeller stirring speed was lower than 400 rpm, the aqueous phase became continuous, while when it was higher than 1050 rpm, the phase which had the higher viscosity became dispersed. Surface active agents have strong effects on phase inversion phenomena.     

轴流式搅拌桨搅拌槽内混合时间的数值模拟

利用计算流体力学软件FLUENT 6.0程序计算了单层CBY搅拌槽内流体混合过程的速度场和浓度场,讨论了加料点位置和监测点位置对混合时间的影响。结果表明,拌槽内物料的混合过程主要由槽内的流体流动所控制;混合时间与加料点位置有关,在桨叶附近区域加料时混合时间比在液体表面加料时的混合时间短,应尽量在搅拌反应器的桨叶尖端处加料;不同的监测点位置对混合时间有很大的影响,在靠近槽底部进行监测所得到的混合时间最短。     

搅拌槽中非稳态温度场分布的研究

在对称装有4组垂直加热列管、直径为500mm的搅拌槽中使用长薄叶(CBY)桨进行搅拌,采用液晶(LC)测温技术测量搅拌槽内温度场的分布。分别研究了搅拌槽中轴向温度分布随加热时间、叶轮雷诺数以及桨的安装高度不同而变化的情况。结果表明,列管加热时间的长短对槽内温度分布的趋势没有影响,温度分布的趋势主要取决于所用搅拌桨产生的流型;随着叶轮雷诺数的增加,槽内温度分布相对趋于均匀;搅拌桨的安装高度对温度场的分布影响也很显著。     

Onset of gas self-induction and power consumption after gas induction in an agitated tank

The behavior of inducted gas from liquid surface and the; power requirements in an agitated tank using a mechanical agitator are studied in order to increase the amount of gas self-induction and the gas retention time for gas absorption. A 45° six-blade downward impeller turbine was utilized in this study. Air and water, air and 40 wt% 60 wt%, and 80 wt% of glycerin water, and air and 106 cP silicon oil were employed as gas and liquid phases. Variables which were studied included geometrical factors (immersed depth of impeller, baffle with and diameter of impeller) and the physical properties of the liquid (viscosity, density, and surface tension). The correlations for the onset speed of impeller and power consumption after gas induction in the agitated tank are established from our experimental results. The amount of gas self-induction from the liquid surface in the agitated tank increases with increasing impeller diameter and speed and decreases with increasing baffle width, depth of impeller and viscosity of liquid.     

搅拌罐（釜）的工程放大方法和经济分析

介绍了搅拌罐（釜）的工程放大原理和方法，并通过实例进行了经济分析。     

Determination and correlation of axial-mixing parameters in an agitated liquid-liquid extraction column

Dispersion coefficients were measured in a pilot-plant sized agitated liquid-liquid extraction column of the Kuhni type. Available techniques were considered, and the axial mixing in both phases obtained over a broad range of operating conditions, both with and without mass transfer and with two sets of stator plates. Earlier correlations for backmixing in the continuous phase were checked and improved, the final equation being successfully tested on available published data.     

Onset of gas induction and power consumption in an agitated tank having shortened narrower baffles

The onset speed of gas induction and the power consumption after gas induction were studied in a gas-induced type agitated tank. In such an agitated tank, four unique baffles which were shorter and narrower than the conventional ones were adopted. Two 45° downward pitched blade turbines (PBT) in series were used as impellers. Gas induction could be formed by the dual impellers operated above the onset impeller speed. Several geometric factors and operation parameters were considered by theoretical aspects and the dimensionless analysis to study the onset of gas induction and the power consumption. In all experiments, air and tap water were used as working fluids. Results revealed that a lower agitation speed and less power consumption were needed for the present tank than a narrower full-length baffled agitated tank. In the present tank, the least specific power consumption was found when the liquid level was about 1·9 times the tank diameter. Two correlation equations were obtained to predict, respectively, the onset speed of gas induction and the power consumption after gas induction. Comparison between the present type and various other gas-inducing type agitated tanks were also discussed. © 1998 SCI