“FORWARD MIXING” MODEL: APPLICATION TO PULSED PLATE EXTRACTION COLUMN OPERATION IN THE EMULSION REGION

The “Forward Mixing” model has been applied to data obtained from a 22 cm diameter pulsed plate extraction column. Measurements of drop size distributions, dispersed phase hold-up and concentration profiles for two systems (toluene-acetone-water and n-butanol-succinic acid-water) of quite different properties were made with the column operating in the emulsion region. Generated drop size distribution function parameters, size-dependent slip velocities and mass transfer coefficients, and continuous phase axial dispersion coefficients were accurate in predicting dispersed phase hold-up and extraction efficiencies (or the related plug flow number of transfer units). These parameters were correlated with phase superficial velocities and pulse velocities. The influence of continuous phase axial dispersion was much greater than the influence of drop size variation, and was not accurately predicted by most previous tracer-based correlations. An inlet dispersed phase distributor was beneficial to the performance with the high interfacial tension system.     

Determination of holdup by air purge in φ50 mm discs and doughnuts pulsed extraction column

在柱径为50 mm的折流板脉冲萃取柱中,首先利用吹气法研究了硝酸水溶液和30％TRPO-煤油水溶液体系的单相流时均摩擦压降Δp_f特性.实验结果表明当A′ω≠0,且u_c＝0时,Δp_f可以忽略;而当Aω＝0时,Δp_f与u_c满足Noh模型的线性关系.在Noh模型的基础上,给出了计算Aω≠0时单相流时均摩擦压降的模型,实验结果与模型预测相一致.在单相流摩擦压降的基础上,又研究了连续相分别为硝酸溶液和30％TRPO-煤油溶液体系的两相流时均摩擦压降Δp_f特征.实验结果表明：两相流时均摩擦压降Δp_f可用于计算分散相存留分数,其近似由连续相所对应的Noh单相流模型求得,并可用于折流板脉冲萃取柱分散相存留分数的确定.     

旋转式微通道内液液萃取的流型及传质

利用高速摄影仪观测了2-乙基己基磷酸单2-乙基己基酯（油相）与硝酸铬水溶液（水相）在旋转式微通道（RME）内部的液-液两相流流型，主要观察到了滴状流型（上油下水片状流、滴状片状流、滴状带状流）、带状流型（带状流、紊乱流）、上水下油流型（上水下油滴状流、上水下油片状环状流、上水下油带状流、上水下油丝状流），共3类，9种。考察了微通道设备的尺寸、内筒转速以及进料流速对流型的影响。发现了随着流速和转速的增加，RME内部的流型从滴状流型到带状流型再到上水下油流型的一个转变。进一步利用水油两相的韦伯数将微通道内部的惯性力和黏性力相关联，绘制了流型图，发现了RME内部惯性、黏性力的线性变化关系。最后在9种不同的流型下进行铬的萃取实验，找到了可实现较高萃取级效率的流型。该旋转式微通道内部流型的研究可以为后期的实验和设备的应用奠定基础。     

微通道内伴有化学吸收气液两相流的空隙率与压力降

微通道内气液两相流空隙率与压力降对微反应器的热质传递性能有显著影响,是微反应器的重要设计参数。采用高速摄像仪和压力测量系统分别对矩形微通道内单乙醇胺水溶液化学吸收CO₂过程的空隙率和压力降进行了研究,考察了弹状流下气液两相流量与化学反应速率对空隙率及压力降的影响。结果表明:当液相流量一定时,微通道内空隙率和压力降均随着气相流量的增大而增大,空隙率随化学反应速率的增大而减小,压力降随化学反应速率的增大而增大;当气相流量一定时,随着液相流量和化学反应速率的上升,微通道内空隙率下降,而压力降上升。提出了微通道内伴有化学吸收的空隙率和压力降的半理论预测模型,模型平均误差分别为15.79%和11.12%,显示了良好的预测性能。     

Hydrodynamic and mass transfer parameter correlations for the rotating disc contactor

The normal, fragmented manner in which various model hydrodynamic and mass transfer parameters are measured and correlated separately, in the vain hope that accurate predictions of extraction column performance will be eventually possible, is avoided here. The ‘forward mixing’ model parameters are all determined simultaneously, in experiments with two sizes of rotating disc contactor where all required measurements, including drop size distributions and continuous phase profile compositions, are made during solute transfer between phases. Accurate predictions from the derived correlations of dispersed phase hold-up fraction, drop size distributions and extraction efficiency are the result.     

超临界二氧化碳干气密封相态分布规律与密封性能研究

以超临界二氧化碳干气密封为研究对象，分别以维里方程、Lucas方程描述二氧化碳真实气体效应、黏度的变化，在考虑阻塞流效应的同时，采用有限差分法对考虑离心惯性力效应的Reynolds方程与能量控制方程进行耦合求解，分析讨论了工况参数与槽形结构参数对其相态分布规律与密封性能的影响。研究表明：S-CO₂从密封端面进口至出口的流动过程中，如果工况参数设置合理，将由超临界态逐渐转变为气态，并不会出现液态；较低的进口压力、进口温度以及转速，均会容易导致潜在的凝结流动发生；相比于工况参数对相态分布的影响，槽形参数对相态分布的影响较小，近乎可以忽略；开启力除了随进口温度的升高而减小外，均随进口压力、转速、槽深、螺旋角的增大而增大；泄漏率随进口温度和转速的增大而减小，但其随进口压力、槽深、螺旋角的增大而增大。这些结果为进一步研究超临界二氧化碳干气密封提供了一定的支撑。     

Characterization of hydrodynamic parameters in a multistage column contactor

Accurate knowledge of hydrodynamic parameters is of major importance for the performance study of liquid-liquid column extractors. The effects of operating parameters on dispersed phase holdup profiles, drop size distributions, and axial mixing in both phases were investigated in a 127 mm diameter multistage contactor of pilot plant scale for the toluene-water physically equilibrated system. Correlations for the mean holdup, the mean drop size, and the continuous phase backmixing were obtained. A stronger dependence of holdup and drop size on the operating conditions and especially on the agitation speed was observed as compared to previous investigations for the same type of contactor. The axial mixing for the single phase flow was found to follow adequately an existing correlation, while the continuous-phase axial mixing in two-phase flows showed some deviations from other existing correlations. Also, flooding criteria, important for the control of the extraction process, were determined based on the shape of the holdup profiles.     

转盘塔内甲基异丁基酮萃取湿法磷酸实验研究

溶剂萃取法是一种经济有效的湿法磷酸净化方法。在转盘塔中,以甲基异丁基酮（MIBK）为萃取剂,开展了净化湿法磷酸的实验研究。考察了搅拌转速、相比对磷酸萃取率、杂质离子选择性、洗涤效果和反萃效果的影响。研究结果表明：萃取过程适宜的相比（溶剂与磷酸的体积比）为4,搅拌转速为200~400 r/min,在此条件下磷酸萃取率为85%;洗涤过程的搅拌转速不应大于100 r/min,适宜的洗涤酸用量为溶剂相体积的10%~15%,在此条件下铁离子（Ⅲ）和镁离子脱除率均在90%以上、铝离子脱除率大于70%、硫酸根脱除率为50%~60%;反萃过程搅拌转速不应大于200 r/min,适宜的反萃水用量为溶剂相体积的9%~15%。MIBK对阳离子的脱除效果较好,但是对阴离子的脱除效果不佳。经过萃取、洗涤和反萃3个过程,磷酸收率为57.8%~70.3%,磷酸中铁离子（Ⅲ）含量可以达到工业级磷酸标准,但是硫酸根的含量无法达标,需要结合其他方法进一步脱除。     

φ50 mm折流板脉冲萃取柱吹气法测量存留分数

在柱径为50 mm的折流板脉冲萃取柱中,首先利用吹气法研究了硝酸水溶液和30％TRPO-煤油水溶液体系的单相流时均摩擦压降Δp_f特性.实验结果表明当A′ω≠0,且u_c＝0时,Δp_f可以忽略;而当Aω＝0时,Δp_f与u_c满足Noh模型的线性关系.在Noh模型的基础上,给出了计算Aω≠0时单相流时均摩擦压降的模型,实验结果与模型预测相一致.在单相流摩擦压降的基础上,又研究了连续相分别为硝酸溶液和30％TRPO-煤油溶液体系的两相流时均摩擦压降Δp_f特征.实验结果表明：两相流时均摩擦压降Δp_f可用于计算分散相存留分数,其近似由连续相所对应的Noh单相流模型求得,并可用于折流板脉冲萃取柱分散相存留分数的确定.     

Droplet break-up by in-line Silverson rotor–stator mixer

Silverson high shear in-line rotor–stator mixers are widely applied in industry for the manufacture of emulsion-based products but the current understanding of droplet breakage and coalescence in these devices is limited. The aim of this paper is to increase the understanding of droplet break-up mechanisms and to identify appropriate literature correlations for in-line rotor–stator mixers. Silicone oils with viscosities ranging from 9.4 to 969 mPa s were emulsified with surfactant in an in-line Silverson at rotor speeds up to 11,000 rpm and flow rates up to 5 tonnes/h. The effect of rotor speed, flow rate, dispersed phase fraction up to 50 wt%, inlet drop size and viscosity ratio on droplet size was investigated. It was found that rotor speed and dispersed phase viscosity have a significant effect on the droplet size, while flow rate, inlet droplet size, viscosity ratio and dispersed phase volume have a lesser effect. The results indicate that low viscosity droplets are broken by turbulent inertial stresses, while droplets smaller than the Kolmogorov length scale are broken by a combination of inertial and viscous stresses. It also appears that the weak dependence of drop size on flow rate enables the energy efficiency of an in-line high shear Silverson to be significantly improved by operating at as high a flow rate as possible.     

Removal of SO2 using ammonium bicarbonate aqueous solution as absorbent in a bubble column reactor

In this work, the removal of SO₂ from gas mixture with air and SO₂ by ammonium bicarbonate aqueous solution as absorbent was investigated experimentally in a bubble column reactor. The effects of the concentration of ammonium bicarbonate, the SO₂ inlet concentration of gas phase and the gas flow rate on the removal rate of SO₂ were studied. The results showed that the higher the SO₂ inlet concentration and the gas flow rate, the shorter the lasting time of SO₂ completely removed in gas outlet, and then the faster the decrease in the removal rate of SO₂. The lasting time of SO₂ completely removed in gas outlet increased with increasing ammonium bicarbonate concentration. During the process of SO₂ absorption, there was a critical pH of solution. When the solution pH was less than the critical pH, it would sharply fall, resulting in a rapid decrease of the SO₂ removal rate. A theoretical model for predicting the SO₂ removal rate has been developed by taking the chemical enhancement and the sulfite concentration in the liquid phase into account simultaneously.     

氯盐体系硝酸/盐酸脉冲萃取分离装置水力学研究

硝酸-氯化钾直接法可低成本制备熔盐级硝酸钾,溶剂萃取分离氯盐溶液中的硝酸和盐酸是关键步骤之一。研究了处理H⁺/K⁺/Cl^-/H₂O-磷酸三丁酯/磺化煤油体系脉冲筛板萃取塔的水力学性能,结果表明分散相液滴直径随脉冲强度的增大而减小,与两相表观流速无关;存留分数随脉冲强度的增大呈现先减小后增大的趋势,随两相表观流速的增大而增大。拟合得到了液滴直径与存留分数的Kumar-Hartland关联式,两者计算值和实验值的平均相对偏差（AARD）分别为4.74%与5.60%。     

酸团中微量正己烷的离心萃取分离研究

采用离心萃取分离技术,回收己内酰胺水解反应产生的酸性溶液(酸团)中的正己烷;建立工业侧线实验装置,考察了离心萃取机的转速、进料口流量及正己烷含量对分离性能的影响。结果表明:离心萃取分离性能随进料口正己烷含量的增加而增强;进料口流量越大,分离性能越差;设备转速为1 500 r/min时,分离效果最佳;转速为1 500 r/min,进料口流量为0.6 m3/h时,平均分离效率可达40%,分离效果好。     

膜萃取防止溶剂污染的优势

本文以３％ＴＢＰ／苯酚／水为实验体系在不同的膜器中对膜萃取过程中料液对萃取剂的夹带,即溶剂的二次污染进行了研究。在保持膜两侧压降不变的情况下对进口和出口处料液的ＣＯＤ值进行了测定,并与传统的溶剂萃取方法相比较。结果表明,膜萃取中料液中溶剂只有少量的夹带,并且夹带量与操作条件和膜构件基本无关。     

New Predictive Correlations for the Drop Size in a Rotating Disc Contactor Liquid‐Liquid Extraction Column

Sauter mean drop sizes (d₃₂) generated from a hole distributor in liquid extraction RDC columns were studied under various conditions. Experiments were designed to generate data required to determine the main variables that control the drop sizes in RDCs. Two precise correlations were proposed for predicting d₃₂ in a RDC extraction column. The first was based on operating variables, hole‐distributor diameter, disc speed, column geometry, and system physical properties. The second one considered the same variables, except the column geometry. This model can be used for design purposes. The two correlations are the first of their type to consider the distributor hole inlet diameter in a RDC column. This diameter has been neglected by previous investigators. The maximum standard deviation for all data is 0.75 %, with a maximum absolute error of 6.8 %.     

大型萃取塔液体分布器性能和设计方法的研究

本文用界面张力极低的丁醇-水体系研究了管式液体分布器孔径和喷口流速对分散相液滴直径分布和液滴平均直径的影响。对适宜喷口速度的选择进行了定量的研究。在此基础上,编制了调整孔径和孔分布以保证分散相沿塔截面均匀分布的计算机程序,可用于石油化工系统大型萃取塔管式分布器的优化设计。     

Droplet velocity,size, and local holdup measurements in an extraction column by tri‐sensor optical probe

The tri‐sensor optical probe was applied to study the hydrodynamic characteristic in a pulsed sieve plate extraction column. Two immiscible liquids consisting of the dispersed phase (kerosene) and continuous phase (water) were introduced in countercurrent operation. Local parameters such as droplet velocity, drop size, and holdup of the dispersed phase were obtained. It was found that the tri‐sensor optical probe could be used as an efficient and convenient technique for measuring local hydrodynamic parameters inside the pulsed sieve plate extraction column. Furthermore, the results indicated that pulsation intensity imposed more influence on these hydrodynamic parameters than two‐phase superficial flow rates in the investigated ranges. Experimental results were found to be in good agreement with the empirical correlations reported in literature. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3958–3963, 2015     

预分散溶剂萃取平衡与传质特性

预分散溶剂萃取(predispersed solvent extraction,简称PDSE）是一种新型的液-液萃取方法.该过程首先将溶剂制成胶质液体泡沫(colloidal liquid aphron ,简称CLA),同时借助胶质气体泡沫(colloidal gas aphron,简称CGA)实现溶质的分离.本文以磷酸三丁酯（TBP）-煤油为溶剂,以十二烷基苯磺酸钠（SDBS）为水相表面活性剂,以TWEEN 80为油相表面活性剂制备了胶质液体泡沫（CLA）. 用十六烷基三甲基溴化胺（HTAB）为水相表面活性剂制备了胶质气体泡沫（CGA）. 利用半间歇式PDSE过程萃取苯酚溶液.研究了pH值、表面活性剂浓度、相比等对萃取率和平衡分配系数的影响.实验发现,PDSE过程更适用于小相比（油相∶水相为1∶1000或更小）和极稀溶液的萃取.实验还发现, PDSE过程的萃取率随着CLA中TBP浓度的增加而增加, 随相比的增加而提高.利用刚性球模型计算了CLA的传质系数,并与传统的液滴进行了比较.在相同的粒径下,CLA比传统的液滴具有更高的分散相总传质系数;与传统萃取塔中存在的液滴相比,CLA也具有一定的优势.此外,对于两者K_da的比较,更体现了CLA的优越性.     

Modelling of liquid-liquid extraction columns: Use of published model correlations in design

Design of several liquid-liquid extraction columns — packed, pulsed-packed, pulsed-plate, Oldshue-Rushton columns and the rotating disc contactor — was attempted utilizing available correlations for drop size, holdup of dispersed phase, flooding velocities, mass transfer coefficients and axial mixing coefficients. Correlations in many cases were vaguely defined and often based on very limited data. Results indicated that for given flow rates and extraction efficiency, the height of a packed or Oldshue-Rushton column must be considerably greater than the predicted minimum heights of the other three columns, which were comparable considering the limited data utilized in the developed correlations. A critical evaluation of the correlations should be carried out to guide the further experimental effort required to confirm the utility of the axial dispersion model in liquid-liquid extraction column design. Extension of the theory to include drop size variation is highly desirable.     

预分散溶剂萃取分离苯酚溶液的研究

Predispersed solvent extraction (PDSE) is a new method for separating solutes from aqueous solution by solvent extraction and one which has shown promise for extraction from extremely dilute solution very efficient and very quick. The use of colloidal liquid aphrons in predispersed solvent extraction may ameliorate the problems such as emulsion formation, reduction of interracial mass transfer and low interfacial mass transfer areas in solvent extraction process. In present paper, colloidal liquid aphrons are successfully generated using kerosene as a solvent,tributyl phosphate(TBP) as an extractant, sodium dodecyl benzene sulphate(SDBS) as surfactant in aqueous phase and Tween-80 in oil phase. Extraction of phenol from dilute solution was studied by using colloidal liquid aphrons and colloidal gas aphrons in a semi-batch extraction column. It has been found that the PDSE process is more suitable for extraction of dilute solutions. It has also been discovered that the PDSE process has a great advantage over traditional single-stage extraction process.