磷酸三丁酯萃取硝酸的动力学

在改进的恒界面池内研究了磷酸三丁酯（ＴＢＰ）－正庚烷（ｎＣ７Ｈ１６）萃取硝酸的宏观动力学。采用热力学方法处理实验数据，计算了两相内组份的传质系数及传质阻力。研究结果表明，萃取过程的传质阻力主要在有机相内。根据动力学研究实验结果，进而分析了磷酸三丁酯萃取硝酸过程的机理，并以被萃组份的活度差为传质推动力作为计算基准建立了萃取速率的数学模型：模型计算结果与实验结果的平均相对偏差为２．５％。实验结果和理论分析表明，此萃取过程为有机相内的扩散控制机制，扩散阻力主要来自有机相内ＴＢＰ和萃合物ＨＮＯ３·ＴＢＰ分子的扩散。     

周期性机械激励液液体系相界面层的传质特性

在改装的恒界面池中采用微分传质系数研究了无机酸和金属盐液液萃取 (反萃 )体系动态相界面的传质速度对可控界面机械激励的响应 .作用于液液体系相界面区域的机械激励不仅显著影响相间区域的扩散渗透性 ,而且明显稳定了液液体系相间区域的传质条件 ,减小了实验误差 .微多相层的形成和发展决定相间动量与物质的传输特性 .用微多相层的概念解释了对相界面区域的激励有助于引发Marangoni表面对流及其他实验现象 .     

转盘塔的纵向混合

<正> 一个成功的逆流萃取塔应该满足生产能力大、界面传质速率高、纵向混合低三个要求,而这三个因素又是和塔型、生产规模和有无外加机械能的输入有关的。本文研究的转盘塔是一种有外加机械能输入的微分型萃取装置。该器有回转平盘与在萃取操作中两逆流液相之间紧密接触。故而,通常界面传质速率主要与液相在塔内的回转速度有关。调节此独立变数会增大两相界面积,从而有利于界面传质速率。但却会因降低轴向浓度梯度的纵向混合程度的显     

往复振动筛板塔对低界面张力体系萃取过程的强化

对低界面张力体系正丁醇-丁二酸-水在往复振动筛板塔中的萃取性能进行研究,体系中水为萃取剂,萃取正丁醇中的丁二酸。实验考察了两相流速、相比、传质方向和筛板振动速率对流体力学性能和传质性能的影响,并且与相同操作条件下固定筛板萃取塔的性能作对比。结果表明,筛板振动速率不高于3.5 cm/s的情况下体系没有发生乳化现象,相比增大到2.8时接近液泛点,实验稳定性较差。流速和相比增大能够获得更好的液滴分布和更大的体积传质系数,但增大的幅度要综合考虑设备的最大通量和两相在塔内的停留时间。分散相到连续相的传质方向传质相界面积大,更有利于提高传质效率。相同操作条件下,连续相中的轴向混合远大于分散相的轴向混合。与固定筛板塔的萃取性能相比,振动筛板改善液滴分布、增大处理能力和强化传质的作用都很明显。     

反胶团萃取磷酸溶液中镁的动力学

采用恒界面池研究了二壬基萘磺酸(DNNSA)-煤油-磷酸体系萃取镁离子的动力学.考察了搅拌转速和传质界面积对萃取速率的影响,实验结果表明:磷酸中镁离子的萃取速率在200 r·min~(-1)时出现与搅拌强度无关的化学反应动力学"坪区",此时萃取速率正比于两相接触面积,说明萃取过程为界面化学反应控制过程.在动力学"坪区",镁离子萃取速率正比于萃取剂浓度和水相镁离子浓度,随着温度升高萃取速率增加;萃取反应活化能为70.01 kJ·mol~(-1),并得到了DNNSA萃取磷酸中镁离子的萃取动力学方程.     

三烷基胺萃取丙酸的动力学特性

为研究胺类萃取剂萃取有机酸的动力学行为 ,以丙酸稀溶液为分离溶质 ,三烷基胺 ( 730 1)为萃取剂 ,正辛醇和煤油的混合物为稀释剂 ,采用恒界面池法考察了萃取剂和溶质浓度、搅拌速率、两相接触面积、温度等操作参数对丙酸萃取动力学的影响。结果表明 :730 1萃取丙酸为准一级反应萃取过程 ;且萃取发生在相界面 ,即界面反应萃取机制 ;表观活化能为 2 8.5kJ/mol,萃取速率受温度的影响不显著 ;经计算 ,在一般的萃取塔操作条件下 ,该体系的萃取过程为反应和传质过程的混合控制。     

固定膜界面萃取的研究

固定膜界面萃取是一种新型分离方法。与有机溶剂直接和水溶液混合接触的通常萃取过程不同,溶剂与水溶液的接触是在膜孔界面上进行的。谈过程没有两相的聚结和澄清。本文(?)50%TBP(煤油(?)—HAC—H_2O和30%P204(煤油)—ZnSO_4H_2O为体系研究丁这一技术,求取了基于有机相的总传质系数。尽管膜传质阻力可能减缓传质速率,然而,微孔中空(?)膜器提供了比通常萃取器大得多的比表面积,体积萃取速率将会明显加快     

复合填料萃取塔操作性能研究

在内径为０．１ｍ，高度为１．０ｍ的玻璃萃取塔中，对四种不同填料用低界面张力体系（正丁醇－丁二酸－水）研究了填料塔的流体力学和传质性能，实验结果表明，用其中的两种填料组合的复合填料萃取塔具有较大的通量和较高的传质效率，可望在工业装置中得到推广应用。     

液-液微尺度混合体系的传质模型

针对微尺度液-液混合体系,考察了流量对膜分散萃取过程的影响,并根据传质过程方程,计算了各种条件下的传质系数和传质速率;采用现有的传质模型分别计算分散相和连续相的分传质系数,然后根据传质阻力的加合性得到总传质系数;应用理论传质系数计算传质效率,与实验值进行了比较.研究结果表明,在微尺度混合条件下,直接影响传质系数的因素是停留时间和液滴直径,传质系数随着停留时间的减小而增大.膜分散萃取的传质系数可以达到1.2×10^-4m&#8226;s^-1,比传统的萃取方式大10～100倍;不能像塔式萃取设备一样,用简单地忽略某一相的传质阻力或用总体平均的简化计算公式来计算微尺度混合的传质性能;考虑滴内滴外传质系数,并考虑时间的影响,利用现有公式分别计算滴内滴外传质系数,并采用阻力加合,可以较为准确地计算微混合条件下的总传质系数,计算值与实验值符合很好.     

萃取串级的新排列——萃反交替多级逆流萃取过程

本文从萃取传质过程的基本关系式出发,提出了采用萃取级和反萃级交替排列、以增大传质推动力,从而提高萃取传质速率、减少萃取级数的新的逐级萃取方式,具体交替排列方式视具体萃取工艺体系之不同而有所不同.从理论分析出发,采用了N,N-二(1-甲庚基)乙酰胺(N_(503))萃取铁和二丁基亚砜(DBSO)萃取磷酸两个萃取体系进行串级计算,并对前—萃取体系进行了实验验证.结果表明,采用萃、反交替排列的多级逆流萃取方式较之通用的多级逆流萃取方式确可收到提高萃取传质速率、减少萃取级数的效果.用小型萃取设备进行的连续流动实验还表明,实现萃、反交替的排列方式以采用逐级式萃取设备(如混合澄清槽或单台单级式的离心萃取器)为宜,在设备设计和布置方面不存在任何困难.     

Influence of acid treatment on the surface activity and mass transfer inhibition of a splittable surfactant

A splittable surfactant, Triton SP‐190, was used to evaluate the effects of acid treatment on the mass transfer rate of an extraction process and on the interfacial tension‐lowering activity of a system containing this surfactant. Equilibrium and dynamic interfacial tensions at the interface of CCl₄ and the aqueous phase containing surfactant were measured by using pendent drop tensiometry enhanced by video digitization. A single‐drop extraction apparatus was used to obtain the extraction percentage of acetic acid from the dispersed CCl₄ droplets to the aqueous phase. The results indicate that the inorganic acid treatment can inhibit the dynamic and equilibrium interfacial tension‐lowering activity of Triton SP‐190. The mass transfer resistance induced by the addition of Triton SP‐190 can also be reduced by the pre‐treatment of acid. The effectiveness of acid treatment on both properties was greater at low pH values, lower surfactant concentrations, and longer treatment times. With HCl treatment, the equilibrium interfacial tension was not able to increase to the value of a surfactant‐free system, but approached a maximum value which was independent of the pH value, but dependent on surfactant concentration. On the contrary, the extraction percentage, which has decreased due to the presence of surfactant, can be recovered completely to that of a surfactant‐free system by acid treatment. The acid‐treatment time required to achieve a significant recovery of mass transfer rate was much longer than that required to recover the interfacial tension. The present results also demonstrate that the constituents contained in an acid‐treatment system had different effectiveness in affecting the interfacial tension and mass transfer rate due to the different mechanisms involved. Copyright © 2004 Society of Chemical Industry     

Absorption of nitric oxide in dilute nitric acid

This paper presents laboratory-scale measurements on the absorption of nitric oxide in dilute nitric acid. The NO concentration in the gas feed varied from 250 to 10 000 ppm. Nitrogen was used as carrier gas. The concentration of nitric acid was between 30 and 60 mass-%. Temperature during the measurements was set at 25 °C. In order to determine mass flow rates, experiments were performed in a double-stirred cell. This type of absorber has a defined gas/liquid interface as the mass transfer area. The liquid phase is introduced periodically and the gas phase continuously. A well-known model was used to describe the phenomenon of NO absorption. Several balance equations were established and solved. The calculated mass transfer rates were compared with those obtained experimentally. The empirical and theoretical data are in satisfactory agreement.     

泡沫金属复合PCM微结构传热储热过程模拟

以石蜡作为相变材料（PCM）,采用六面通圆孔三维结构模型,对泡沫金属复合PCM内相变熔化过程进行了数值模拟。研究了不同材料（Cu、Al、Ni、Fe）泡沫金属孔密度和孔隙率对复合PCM传热和储热性能的影响。结果表明,泡沫金属复合PCM传热过程受热传导和自然对流作用综合影响;随孔密度增加,复合PCM完全熔化时间缩短幅度逐渐减小,且泡沫金属热导率越高,孔密度对传热速率影响越大;泡沫金属复合PCM内存在非热平衡现象,孔密度和孔隙率增加均可减小最大平均温差,但对最终平衡时间的影响却截然不同;此外,泡沫金属复合PCM单位质量储热密度随孔隙率增大而增大,相比泡沫Cu、Ni、Fe复合PCM,泡沫Al复合PCM的单位质量储热密度较大,增加速率也较大。     

硝酸分解磷矿过程中碘的迁移分布规律

硝酸分解磷矿是硝酸磷肥生产过程中重要的操作单元。研究了酸解时间为30~240 min、酸解温度为40~90 ℃、硝酸初始质量分数为40%~65%及酸矿质量比为1.15:1~1.35:1对磷矿中碘在气、液、固三相中迁移分布的影响。结果表明：硝酸分解磷矿过程中,碘以单质的形式迁移至气相中。随着酸解时间、酸解温度、硝酸初始浓度的增加,碘在气相中的分布率增大。然而,随着酸矿质量比的增加,气相中的碘呈现出先增加后减小的趋势。酸解时间和酸解温度对碘在气相中分布率的影响最大。当工艺参数控制在酸解温度为60 ℃、硝酸初始质量分数为55%、酸矿质量比为1.25:1、酸解时间为120 min时,碘在气、液、固三相中分布率分别为65.21%、26.89%、7.91%。     

多组分相际传质近界面浓度场的测定

<正> 1 引言 多组分相际传质的理论研究进展缓慢,由于实验技术的限制,现有的传质理论尚未得到验证,其微观机理尚不清楚,而深入研究多组分相际传质的关键问题是选择合适的浓度测量方法.目前,激光测温已普遍应用于各学科研究领域,但浓度场的测定尚限于浓度变化大且变化区域大的体系,文献报道最多的是扩散系数的测定.苗容生等利用显微激光全息干涉技术,成功地测出了湍流场中二元气液传质液相侧边界层内的浓度场变化.对于三元系统的测量,迄今未见文献报道,本文利用双波长激光显微全息干涉技术,对三元气液传质液相侧边界层内的浓度分布进行测量.     

新型组合式规整填料在液液萃取中的传质性能

采用质量分数30%磷酸三丁酯-煤油-醋酸-水物系,对一种新型萃取用组合式规整填料的传质性能进行了测定,考察了连续相流速和分散相流速对其传质效率的影响。实验结果表明:在相同的二相流速下,组合式规整填料的表观传质单元高度比16 mm鲍尔环平均低约54%。固定连续相流速,随着分散相流速的增加,填料的表观传质单元高度降低,传质效率提高;固定分散相流速,随着连续相流速的增加,填料的表观传质单元高度增大,传质效率降低。     

The influence of the interfacial resistance on the liquid—liquid mass transfer of carboxylic acids

The instantaneous solute concentration in freely suspended single droplets were measured as function of the exchange time by means of a radionuclide technique with and without chemical reaction in liquid—liquid systems in several drop sizes covering the range of Reynolds numbers 114–443.The transfer rates of benzoic acid and/or caprylic acid from toluene drop into water as well as of caprylic acid into aq. NaOH solution were investigated. Benzoic and caprylic acids prevail in the toluene phase as dimers and in the water phase as monomers. In case of the mass transfer of the benzoic acid the chemical reaction of the dimer to the monomer causes an interfacial resistance which has the same order of magnitude as the mass transfer resistance in the continuous phase.In case of the mass transfer of the caprylic acid the solute forms a monolayer at the interface. The rate determining step is the desorption of the solute from this monolayer.In case of the mass transfer of the caprylic acid to aq. NaOH solution the mass transfer resistance of the continuous phase can be neglected due to the enhancement of the mass transfer by the instantaneous reaction in this phase. The mass transfer rate is very high at the beginning of the mass exchange due to the interfacial turbulence caused by the chemical reaction. Also at longer contact times the mass exchange rate is high probably due to the reduction of the free desorption energy (increase of the desorption constant) caused by electrically charged monolayer.     

Extraction of Uranium Nitrate with 30% (v/v) Tributyl Phosphate in Kerosene in a Pilot Annular Pulsed Disc-and-Doughnut Column—Part II: Axial Mixing and Mass Transfer Performance

Mass transfer experiments were carried out in an annular pulsed disc-and-doughnut column (APDDC) using 30% (v/v) TBP-kerosene + uranium nitrate + nitric acid + water system (uranium nitrate system) for both extraction and stripping processes. Parameters in the axial dispersion model (ADM) and plug-flow model (PFM), namely, the axial dispersion coefficient of the continuous phase and the number of mass transfer units, were regressed by correlating the respective model with the experimental concentration profile. The mass transfer coef?cient is calculated, and new correlations are developed to predict the axial mixing coefficient of the continuous phase and the volumetric mass transfer coefficient. The height of a transfer unit is also calculated. The influence of axial mixing on mass transfer performance for the uranium nitrate system is discussed.     

Mass transfer enhancement of acetic acid across a plane kerosene/water interface by an electric field

The intensification of mass transfer of acetic acid from kerosene into water across a plane interface by the application of an electric field normal to the interface is investigated. The application of an electric field affects mainly mass transport through the bulk of the organic phase rather than the interface. In the range (5–30) × 10⁴ V/m the mass transfer coefficient changes from 8 × 10^?6 to 2 × 10^?5 m/s. A model based on the movement of electric charges in the organic phase indicates that a Sherwood-Grashof correlation for free convection only is also suitable for the electrically driven process if the Grashof number is modified to take into account the effect of the electric field on the movement of the electric charges.