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。     

塑料异型矩鞍填料的流体力学及传质性能研究

在内径300 mm塔中,以空气-氨-水为物系,对开发出的一种新型塑料散装填料———异型矩鞍填料的流体力学及传质性能进行了研究。获得了该填料的几何特性、流体力学性能及传质性能数据,并通过对实验数据的回归分析,得出了填料层压降Δp/Z、泛点填料因子F及气相总传质单元高度HOG的关联式。研究结果表明,塑料异型矩鞍填料具有通量大、压降低、气液分布均匀及传质性能优良等优点。     

A new equation for estimating the height of the mass transfer unit in extraction columns

In this study, a new equation for estimating the height of the mass transfer unit, H_oxp, for mutually insoluble extraction systems was developed. The equation's accuracy and robustness were tested by comparing the predicted results with experimental data in the literature. With the same apparent interfacial tension, the mass transfer unit height decreased hyperbolically with the increase of the overall interphase volume mass transfer coefficient, despite the differences of column dimensions, experimental systems and operating conditions.     

新型网架规整填料的传质性能

对一种新型网架规整填料用于萃取时的传质效率进行了实验研究。在Φ50mm的填料萃取塔中,选用煤油–苯甲酸–水和30%TBP(煤油)–乙酸–水两种不同界面张力的物系,测定了该填料和Φ10mm的鲍尔环填料在不同操作条件下的表观传质单元高度。扣去影响因素,网架填料的表观传质单元高度至少会比鲍尔环填料低25%,而网架填料的堆积密度仅为鲍尔环的38%。同时对影响传质的因素进行了分析,并针对该填料的特点,提出了优化设计原则。     

新型均流填料塔的传质性能研究

提出了一种新型均流填料塔设备,在Φ600 mm的圆形冷模实验塔中,以空气-水-CO2为工质进行了CO2解吸试验,利用滴定法测定了多种气液负荷下新型均流填料塔的传质性能,并在相同工况下与鲍尔环填料塔进行了对比研究。试验结果表明:在试验喷淋密度下,新型均流填料塔与鲍尔环填料塔相比,液相传质单元高度降低了19%以上;随着喷淋密度的降低,液相传质单元高度降低更加显著。在正常操作范围内,新型均流填料塔的传质效率远高于鲍尔环填料塔,是一种传质性能优良的新型填料塔设备。     

海水脱硫散堆填料塔的数值模拟及传质计算

采用体积平均法建立了描述散堆填料塔内气、液两相的流动模型;在双膜理论的基础上建立了平均体积传质模型。通过数值计算,获取了在不同液气比下塔内流体速度、孔隙率分布、压力分布及脱硫效率,并就压力损失和脱硫效率与实验值进行了对比,预测值与实验值吻合较好,趋势完全一致。分析填料塔内海水的速度分布矢量图和填料塔中间高度断面上的速度分布图发现,靠近壁面处存在着显著的壁流现象,并在沿流方向上液体有向壁区积聚的趋势,壁流现象变得更严重。由3种填料径向孔隙率分布图可看出,近壁面处的孔隙率明显高于中间区域,表明这是形成壁流的原因所在。     

Trickle flow liquid–solid mass transfer and wetting efficiency in small diameter columns

A novel method to simultaneously measure liquid solid mass transfer and external wetting efficiency was employed at column to particle ratios of 10, 6 and 3. Two prewetting procedures representing the upper (Kan) and lower (Levec) hysteresis branches were used. For a multipoint distributor on a Kan prewetted bed wetting efficiency and the specific mass transfer coefficient were almost unaffected by column diameter. The multipoint distributor on a Levec prewetted bed exhibited a decrease in specific mass transfer with decreasing column diameter. Point source experiments resulted in significantly lower wetting and mass transfer measurements with an increasing trend with respect to decreasing column diameter. The results indicate that with proper distribution and prewetting, the effect of column diameter on averaged wetting and liquid–solid mass transfer is almost negligible, a powerful result considering the importance of these parameters on reaction experiments. © 2012 Canadian Society for Chemical Engineering     

泡沫陶瓷环形填料的流体力学和传质性能

填料是化工气液传质设备中的核心组成部分,其作用主要是为气液或液液两相提供充分的接触面,强化两相间的传质或传热过程．填料的结构和性能对填料塔的技术经济指标具有决定性的影响．陶瓷填料具有耐腐蚀、价格低廉、润湿性与热稳定性好等特点．但其加工性能差,只能做成简单形状,与其他材质的填料相比,比表面积和空隙率都比较小,流动阻力大,传质性能较差,使其应用受到了一定的限制．     

Particle-liquid mass transfer in three phase sparged reactor

Particle-liquid mass transfer in a three phase sparged reactor has been studied over a wide range of particle sizes, for the chum-turbulent regime. The particle-liquid Sherwood number has been correlated in the usual form with the Reynolds and Schmidt numbers. Use of the hindered particle settling velocity in the Reynolds number yields good agreement (±20%) with the present as well as most of the literature data. The proposed correlation also holds for power law non-Newtonian liquids when the effective viscosity is used.     

第二液相对气液二相体系传质的影响

以CO2气体-K2CO3/KHCO3水溶液吸收过程为研究体系,用酸解法测量气体被吸收的速率,通过对比试验考察了加入第2液相(有机相)对体系传质速率的影响。经过试验研究证明,第2液相的加入对气液传质过程的影响程度与加入的物质有关,在试验条件下甲苯对体系强化作用高于异辛醇和庚烷对体系的强化作用。当第2液相加入量较小时,随加入量的增加,其对气液传质过程的促进作用增强,但当第2液相加入量较大时,这种作用则不明显。同时第2液相对传质作用的影响与流动场有关,增加流动场的搅动有助于强化气液传质作用。     

Texture influence on liquid-side mass transfer

The impact on different packing material textures to liquid-side controlled mass transfer for the CO₂ absorption into silicone oil is analyzed experimentally. Typical industrially applied textures with bidirectional pyramidal and unidirectional wavy topographies are investigated for a wide range of liquid loads and viscosities. It is found that the texture design has a significant influence on the mass transfer efficiency, e.g. mass transfer intensification up to 80% can be performed by a textured surface compared with a flat inclined plate. Additionally, counter current gas flow affects the mass transfer positively as expected, but the texture impact is significantly higher. Silicone oil is widely used for fluid dynamic analysis. Here, fundamental data and procedures for mass transfer determination are provided for the first time in order to characterize present textures of column internals.     

Hydrodynamic and mass transfer efficiency of ceramic foam packing applied to distillation

In addition to a high void volume and specific area, solid foams possess other properties (low density, good thermal, mechanical, electrical, and acoustical behaviour) that make them attractive for applications such as heat exchangers and reformers. Applications using foams as catalysts or structured catalyst supports have demonstrated higher performance than classical catalysts. Several studies have explored the hydrodynamic behaviour of foams in monophasic and countercurrent systems and have reported very low pressure drops. This paper describes the application of ceramic foam to distillation. The β-SiC foam contains 5 pores per inch (PPI) with a 91% void volume and a surface area of 640 m²/m³. Performance parameters including pressure drop for the dry and wet packing, flooding behaviour, and dynamic liquid hold-up were measured in a column of 150 mm internal diameter. The mass transfer efficiency in terms of the height equivalent to theoretical plate (HETP) was determined by total reflux experiments using a mixture of n-heptane and cyclohexane at atmospheric pressure. The experimental results were used to develop a set of correlations describing pressure drop and liquid hold-up in terms of a dimensionless number. The hydrodynamic performance and mass transfer efficiency were compared with classical packing materials used in distillation.     

第二液相的加入对气液传质系数的影响

以搅拌罐中的水吸收CO2为研究体系,分别采用异戊醇、苯和正己烷为第2液相,通过实验考察了第2液相的加入对气液传质的影响.实验结果表明:第2液相的加入对气液体积传质系数KLa有很大的影响,且不同的第2液相的影响程度也不同.在一定的操作条件下,KLa均随搅拌速度和第2液相体积分数的增加呈先增大后减小的趋势,随表观气速(在一...     

组合环单体填料的流体力学和传质性能

本文介绍了新近研制的组合环单体填料对于汽液接触过程的流体力学与传质性能。实验表明,这种填料具有比矩鞍环填料阻力小、传质效率高的优点,可以代替鲍尔环、矩鞍环等常用填料,以取得良好经济效益。     

气-液-液萃取传质效率的研究

在液-液萃取过程中,提高分散相的表面更新速率可有效提高萃取的传质效率.研究发现,在萃取过程中使用气体搅拌可以增加液液之间的接触面积,促进液相内的湍动和循环.据此,本文在气-液-液萃取条件下对不同填料的传质性能进行了测定.实验表明,通入气相后分散相液滴呈现稳定的“油包气”空心状态,这种结构大大降低了分散相液滴的传质层厚度,减小了传质距离,极大地强化传质效率.在适宜气速下,气-液-液萃取效率较传统萃取效率提高20％～40％.通过与散装填料对比,发现规整填料更利于强化萃取效果,传质效率提高约50％.     

A tool for mass transfer evaluation in packed-bed columns for chemical engineering students

This paper presents a Microsoft Excel tool to calculate liquid-gas mass transfer coefficients in packed towers to support numerical design activities in the courses of Unit Operations for Industrial Process and Sustainable Process Design for the Master’s degree in Chemical Engineering of the University of Naples Federico II (Italy).The Mass Transfer Solver Tool (MT Solver Tool) uses several available models to estimate, separately, the values of liquid and gas mass-transfer coefficients and the wet surface area for 144 random and structured packings of interest for absorption/stripping and distillation processes. In addition, a separate spreadsheet can be used in a user-defined mode, to evaluate the mass transfer coefficients with new packing types or to interpret experimental data when the geometrical and physical characteristics of the packing are known. Eventually, the tool is supplied with a data library, where packing geometry and model fitting parameters can be retrieved.The software is aimed to support students and educators in the Unit Operations for Industrial Process and Sustainable Process Design courses. In particular, this is meant to be an example on how the accuracy of design algorithms adopted in unit operation processes is affected by the use of the underpinning correlations for mass transfer rate or pressure drops. Besides, this is aimed to encourage comparison of different correlations when exact field data are not available. Besides, chemical engineers and researchers interested in packed columns design and modelling data may also benefit from the utilization of the software. The MT Solver Tool was introduced to students in a dedicated tutorial lesson after lecturers on packed column design algorithms for distillation, absorption and stripping. Most of the students of the course participated to a group training aimed to simulate the design of an absorption column supported by the MT Solver Tool providing feedback on its application.After the training, an anonymous survey was proposed to the students to monitor the approval rating of the proposed activity and the use of the MT Solver Tool software to support numerical calculations.     

Experimental and numerical study of mass transfer efficiency in new wire gauze with high capacity structured packing

ABSTRACT

Experimental and numerical studies were conducted on the mass transfer efficiency of new wire gauze structured packing. For serving this purpose, various operational conditions were studied to assess the optimal parameters such as HETP of PACK-2100 in the distillation column. The results indicate that the HETP values are enhanced in comparison to conventional ones. In addition, the HETP slowly increases from 4 to 6 cm as mass flow rates of air and liquid flow are increased. The numerical simulations were also performed to describe the performance of the PACK-2100. The Eulerian-Eulerian multiphase approach is applied to calculate the value of HETP and pressure drop. The computational results confirmed that our experimental results. The average relative error between CFD predictions and the experimental data for the prediction of mass transfer efficiency is 20.45%.     

Enzyme mass transfer coefficient in aqueous two phase system using a packed extraction column

Fractional dispersed phase hold-up and dispersed side mass transfer coefficients for amyloglucosidase were measured in a 56 mm i.d. packed extraction column using a sodium sulphate-polyethylene glycol 4000 system. Raschig rings (3 to 13.3 mm), Berl saddles (12 mm), Pall rings (12.6 mm), glass spheres (5.2 mm) and structured wire gauze were used as packings. The effect of packing size was investigated in the case of ceramic Raschig rings. The effect of phase composition of the aqueous phase system also was studied. Correlations have been developed for fractional dispersed phase hold-up and volumetric mass transfer coefficient with packing voidage, dry surface area of packings, superficial dispersed phase velocity and the liquid phase physical properties.