Modelling continuous foam fractionation with reflux

An equilibrium stage approach is taken to modelling the performance of a continuous foam fractionation column with reflux. Such an approach has been facilitated by recent developments in the understanding of pneumatic columns of foam that allow liquid rates within the rising column of foam to be predicted with confidence. It is shown that the recovery of surfactant into the product stream increases monotonically with increasing reflux ratio but this is at the expense of reduced product rate.     

Élements de calcul des colonnes de fractionnement par moussage continu

Foam fractionation is considered as a unit operation. A theory based upon dimensional analysis is used for calculating continuous fractionation columns. Internal reflux ratio resulting from foam instability was taken into consideration and a numerical value is given. The concepts of specific productivity of the column P* and specific energy consumption E* are introduced. A formula is given for the correlation between P* and the parameters characterizing the column geometry (column diameter, foam height) and operating conditions (gas rate, external reflux ratio, feed concentration, feed rate, feed level).     

泡沫分离除去水溶液中微量硫酸根离子

以十六烷基三甲基氢氧化铵为表面活性物质,采用泡沫分离技术对去除水溶液中微量硫酸根离子进行了研究,重点考察了溶液的pH、鼓泡气体流量、表面活性剂浓度及泡沫塔装液量的影响. 结果表明,十六烷基三甲基氢氧化铵具有良好的起泡性能,对水溶液中硫酸根离子的去除效果比较理想,在溶液pH 10、气体流量0.036 m3/h、装液量900 mL、表面活性剂浓度0.13 g/L的条件下,溶液中的SO42-能很好分离(富集比为22.4,去除率为94.1%). 与其他阳离子表面活性剂相比,十六烷基三甲基氢氧化铵在泡沫分离结束后不会在水溶液中引入新的酸根离子,为进一步探索脱盐新方法提供了依据.     

Foam separation of colloidal particulates

The foam-separation process may be utilised for the separation of hydrophobic (and hydrophilic) colloidal particulates of a flocculent nature from aqueous suspension by the addition of a surfactant with opposite charge and by gas dispersion through the suspension. Process operation and the significant independent and dependent variables are discussed. A model is presented that divides the process into a basic separation step in which the oleophilic particles are adsorbed at the gas/suspension interfaces of the bubbles and an entrainment step in which bulk solution is physically carried into the foam. The model is used to interpret experimental results for the ferric oxide-dodecyl sodium sulphate system, from consideration of residual ferric oxide concentrations, foam volumes, and removal ratios. A parameter, relative fractionation, is used to compare quantities of surfactant and particulates in the foam and in the bulk solution. Results are used to contrast the effects of surfactants on the foam separation of various particulates of opposite charge, including Escherichia coli, stannic oxide and kaolin clay, with particular emphasis on effects on foaming ability.     

内循环式泡沫浮选塔处理含铬废水

采用自制的内循环泡沫浮选塔处理含铬废水,考察pH值、Fe(NO3)3浓度、十二烷基硫酸钠(SDS)浓度、气体流量、分离时间等因素对分离效率的影响,并与常规泡沫塔比较. 结果表明,在12~35 min内,内循环式浮选塔分离效率更高,35 min时塔内铬离子浓度为0.6 mg/L,常规泡沫塔内铬离子浓度为10 mg/L. 内循环浮选塔最佳分离工艺条件为,对初始铬浓度为20 mg/L的废水,在pH 5.5、SDS 100 mg/L、Fe(NO3)3 60 mg/L、气体流量800 mL/min条件下处理效果最好,泡沫夹带率约为10%,Cr(III)脱除率可达97%以上.     

螺旋构件强化排液的泡沫分离塔用于牛血清蛋白分离

引言 泡沫分离技术又称泡沫吸附分离技术[1],是以气泡作为分离介质,利用被分离组分在气液两相界面吸附性质的差异进行浓缩溶液中表面活性组分.在泡沫分离过程中,通过空气分布器在泡沫塔液相中产生气泡,气泡沿着轴向向上流动,被分离表面活性组分吸附在气泡的气液两相界面上,当吸附接近平衡后,气泡离开液相,在液相上方形成泡沫相.     

Feasible separation regions for distillation I: Structure

A feasible separation region is determined for only four special combinations of a saturated vapor/liquid feed and total/partial condenser or reboiler. This work addresses the construction of a feasible separation region for a general case where the feed is a mixture of vapor and liquid in equilibrium and where the column is equipped with a partial/total condenser and reboiler. The analysis reveals that the product composition sets (which are defined for various reflux and reboil ratios and a fixed number of stages in each column section) are the main elements of the feasible separation region. The application of the geometric model of the column in combination with the shape of the distillation line led to the conclusion that the feasible separation region is the union of two product composition sets for both enriching and stripping columns both with an infinite number of stages. The boundary of the feasible separation region consists of several curves related to specific types of operating modes in the column. Some of these curves create a well‐known product composition multitude, whereas other curves form a generalized distillation limit. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

精密精馏填料塔的稳态特性

本文第一部分探讨精密精馏填料塔的最佳回流比。文中提出一个关联式来估算在一定回流比下的传质单元数,并由此导出最佳回流比图。精密精馏最佳回流比的最大值约为1.4R_m。 本文第二部分探讨最佳的塔径与填料尺寸比。实验是在内径分别为20、28、32、44mm,填料层高从1020到1475mm四个填料塔中用2.5×2.5mm三角螺旋填料以正庚烷-甲基环己烷系统进行。根据实验求得的全塔浓度分布曲线,在除去塔顶及塔底两端的端效应后,得出填料层的真实分离效率（即传质单元高度或每米填料高的传质单元数）。以真实分离效率与塔径及填料尺寸比作图,所有恒气速下的曲线都呈现出最佳点,并且其比值几乎相同。对于这种填料,最佳塔径与填料尺寸比约为13—14,此值与普通填料或工业填料大致相似。     

Pilot-scale experimental studies on ethanol purification by cyclic stripping

Cyclic distillation is a proven process intensification method for enhanced separation of various mixtures. It uses an alternative operating mode based on separate phase movement which leads to important practical advantages (vs conventional mode) such as increased column throughput, lower equipment cost (using much less trays at the same reflux ratio) and reduced energy requirements by 20–35% (smaller reflux ratio at the same number of stages), and better separation performance (up to three times). However, if the impurities to be separated are in very low amounts in the feed then distillation is not favorable from an energy use viewpoint. This article is the first to report the practical performance of a continuous process for ethanol purification by air stripping using a cyclic mode of operation, a novel process that avoids the costs of distillation. The purification of ethanol food grade (96.4 vol%) from volatile impurities (0.5 vol%) such as esters, aldehydes, and alcohols, is carried out in a hydro-selective column with five stages. The lightweight impurities are removed from a stream that is the head fraction of a distillation column. This is usually a waste stream amounting to 3–6% of the plant production rate. By concentrating the stream with impurities, more ethanol is produced such that the losses are reduced to only 1–1.5% of the plant capacity. Based on the experimental results presented in this work, a process consisting of two air stripping columns using cyclic operation is proposed for industrial implementation.     

Cocurrent vacuum de-aeration of water for injection into oil reservoirs

Conventional vacuum stripping to reduce the oxygen content of injection water for secondary recovery of oil is carried out in packed columns with the released gases and water flowing countercurrently; hence large column diameters (normal liquid load circa 100 m³/(m²h)) and foaming that requires the addition of defoaming agents. Measurements with cocurrent and countercurrent flow at the same flow rate produced practically identical mass transfer coefficients. With flooding excluded in cocurrent flow, columns can be operated with higher liquid loads than in countercurrent flow. In addition, nitrogen released in the top part of the packing is better utilized as stripping gas, and foam is withdrawn as soon as it increases the pressure drop.     

Kolonnenschäumen I: The Technique of Laminae Column Foaming

Abstract

Laminae column foaming is a special type of column foaming (foam separation). The foam is degraded to fast-moving, nearly planar laminae, which are rinsed by reflux. The method is distinguished by a simple technique, quick establishment of the steady state, and the possibility of working even with low-foaming solutions and handling small quantities of substances. The uncomplicated surface formation and laminae/wall system enable the principles of foam separation to be studied. The phenomena of laminae column foaming are described, as are types of laminae producers, countercurrent columns, and laminae destroyers, and a complete apparatus with circulating gas. Column foaming is compared with column distillation and column crystallization, and its place in the system of column separation methods is discussed.     

间歇式泡沫分离法回收海水中硼的研究

采用间歇式泡沫分离法研究了海水中硼的回收工艺。主要考察了表面活性剂种类及用量、溶液pH、气体流量等因素对海水中硼的分离性能的影响。实验结果表明：十二烷基三甲基氯化铵（DTAC）、十四烷基三甲基氯化铵（TTAC）、十六烷基三甲基氯化铵（CTAC）以及十八烷基三甲基氯化铵（OTAC） 4种表面活性剂中CTAC对海水中硼的分离效果最好;随溶液pH的增加,硼的回收率和富集比均先增大后减小;随CTAC用量的增加,硼的回收率逐渐增大并趋于稳定,而富集比先增大后减小;随气体流量的增加,硼的回收率先增大后减小,而富集比则逐渐减小。在实验条件范围内,当CTAC质量浓度为0.2 g/L、溶液pH为9、气体流量为200 mL/min时,硼的回收率达到90%,富集比达到8。     

Surfactant Recovery from Water Using Foam Fractionation

Abstract

The purpose of this study was to investigate the use of foam fractionation to recover surfactant from water. A simple continuous mode foam fractionation was used and three surfactants were studied (two anionic and one cationic). The effects of air flow rate, foam height, liquid height, liquid feed surfactant concentration, and sparger porosity were studied. This technique was shown to be effective in either surfactant recovery or the reduction of surfactant concentration in water to acceptable levels. As an example of the effectiveness of this technique, the cetylpyridinium chloride concentration in water can be reduced by 90% in one stage with a liquid residence time of 375 minutes. The surfactant concentration in the collapsed foam is 21.5 times the feed concentration. This cationic surfactant was easier to remove from water by foam fractionation than the anionic surfactants studied.     

连续复合精馏提取裂解C_9芳烃中三甲苯

对乙烯生产过程中的主要副产物裂解C9芳烃的用途简要概括;提出采用连续复合精馏法提取裂解C9芳烃中的三甲苯馏分,为生产二甲苯歧化反应提供原料,建立连续复合精馏装置,精馏段采用θ环填料结构,提馏段采用泡罩板式结构,研究进料体积流量、塔板数、出料体积流量及回流体积比对分离过程的影响,并采用气质联用色谱分析实验结果。在优化条件下,可以将三甲苯的质量分数由原料中的8.28%提高至22.33%,收率94.37%。同时采用ASPEN PLUS软件对实验进行模拟,实验值与模拟值最大相对平均误差为-0.46%。为进一步放大实验及萃取精馏提取高纯度三甲苯馏分提供依据。     

泡沫分离技术的实验研究——回收废液中的金

<正>泡沫分离是一种新的分离技术,在国外研究工作已取得了不少成果.Jorne和Rubin在研究金属离子泡沫分离的基础上,提出的Goug chapman扩散双电层理论,阐述了利用相反电荷的金属离子与表面活性剂离子之间的静电吸引作用,达到金属离子的泡沫分离.Rubin和Lapp、Charewicz和Grives等人通过对泡沫分离金属离子的研究表明:pH值是一个重要的影响因素.同时,离子强度可以改变表面活性剂的选择性.Bruner和Stephan采用泡沫分离方法脱除洗涤剂厂排放的一级及二级污水中的表面活性剂,试验结果表明:塔式泡沫分离装置比槽式装置有更高的脱除率.     

Liquid overflow from vertical co-current foam columns

A new criterion to predict the liquid overflow rate from vertical co-current foam column has been suggested. This criterion is combined with a recent model for liquid holdup in semi-batch foams to generate an analysis for co-current foam columns.The paper also presents experimental investigations on liquid overflow rate in the hitherto unexplored ranges of parameters. The variables studied areThe suggested model is compared with both the published as well as present experimental data on the liquid overflow rate. The agreement between the two     

Recovery of Co2+ Ions from Aqueous Solutions by Froth Flotation

ABSTRACT

The recovery of Co(II) ions from aqueous solutions under acidic conditions (pH 5) was investigated in flotation columns with inside diameters of 4.0 and 8.0 cm. Three surfactants, dodecylamine, cetyl pyridinium chloride, and sodium dodecyl sulfate, were used as collectors. Sodium dodecyl sulfate was found to be the most efficient; all three, however, produced hydrated froths, leading to rather low recoveries and separation efficiencies. The volumetric gas flow rate was found to affect the process in relation to the amount of surfactant added and the column diameter. The scale-up of the column should be done in terms of the same superficial gas velocity in order to maintain similar levels of metal ion recovery.     

连续泡沫分离塔回收水溶液中钼(Ⅵ)的研究

以十六烷基三甲基氯化铵为表面活性剂,在连续稳态操作条件下,研究了泡沫塔和填料泡沫塔回收水溶液中微量Mo(Ⅵ)的分离性能。结果表明:随鼓泡区高度的增加,泡沫塔的富集率逐渐增加,回收率逐渐减小;随填料层高度的增加,填料泡沫塔的回收率增加,富集率减小;随泡沫层高度的增加,两种塔的富集率均逐渐增加,回收率均逐渐减小。泡沫塔内的浓度分布基本一致,表明泡沫塔存在较大的液相返混,填料泡沫塔内浓度分布随填料层高度的增加而增大,表明填料泡沫塔的液相返混程度较泡沫塔小。填料的加入有效增大了气液传质面积,提高了气液传质速率。填料泡沫塔的回收率远高于泡沫塔,但富集比略有下降。在实验条件范围内,填料泡沫塔中Mo(Ⅵ)的回收率可达99.8%,富集率可达12.2。     

泡沫分离回收水中低浓度磷酸三丁酯

以吐温系列表面活性剂采用泡沫法回收水中的微量磷酸三丁酯．实验结果表明，在本实验条件下，泡沫法可以回收水中的磷酸三丁酯，磷酸三丁酯的提浓率与残留率与起始磷酸三丁酯浓度、起始表面活性剂浓度和表面活性剂种类有关。     

鼓泡塔反应器的多级回流模型

对鼓泡塔反应器提出:气相用多级串连混合器模型,对其液相用带回流的多级混合器模型.中间各级液相中气体组分浓度假定为前后两级的平均值.从而可以逐级计算气、液浓度和气量沿塔高的分布.模型应用的范围可包括非一级反应及气体压强、气体量和气体组成沿塔高变化的情况.用所提出的模型验算了两个小型鼓泡反应塔的热模试验情况,所得结果与所观察到的现象相符.