膜蒸馏法分离易挥发溶质水溶液

本文以稀甲醇水溶液为实验物系,研究了易挥发溶质水溶液膜蒸馏过程的传质和传热性能。对比直接接触膜蒸馏和空气隙膜蒸馏的实验结果得出,以提浓易挥发溶质为目的的膜蒸馏,采用空气隙膜蒸馏为宜。影响通量的主要因素是空气隙的传质阻力,影响分离因子的主要因素是膜热侧蒸发表面和冷侧冷凝表面之间的温度差。     

Water Purification by Membrane Distillation Process

Abstract

The demineralization of water by membrane distillation (MD) has been investigated. In the first stage of investigations the tap water or boiled tap water was employed as a feed, and the water recovery coefficient exceeding 75% was achieved. The obtained concentrate was supplied to the second stage of MD installation. The quality of distillate was stable and practically independent of the feed concentration. The produced distillate has the electrical conductivity in the range of 1.4–2.5 µS/cm. The precipitation of salt deposit on the membrane surface was observed during the water demineralisation, especially in the first stage of MD. The membrane morphology and the composition of precipitate layer were studied using scanning electron microscopy coupled with energy dispersion spectrometry. The formed deposit caused clogging of the membrane surface (pores), and resulted in a gradual decline of the module efficiency. Moreover, the formation of the deposit on the membrane surface was the major reason of the partial membrane wettability.     

Analysis of the Start‐up Process for Reactive Distillation

The start‐up procedure of a distillation column is a time‐ and energy‐consuming process. Further, the products during the start‐up time are off specification and cannot easily be recycled as for conventional distillation but must costly be disposed of. In this paper, a process model to simulate the barely analyzed start‐up procedure for a reactive distillation from the cold and empty state to steady state is presented. The start‐up of a reactive distillation column has been modeled with gPROMS. The advantage of a cold and empty start‐up is the consistent and reproducible initialization. Commercial simulators do not give the opportunity to start form a cold and empty state, e.g., a column modeled with Hysys must be shut down from a steady state to be able to model the complete start‐up process, which is not possible, for example, for a batch process. Also, a change in the describing equations and discontinuities in process variables is difficult to handle within the simulation. In this paper, the start‐up strategies normally used for distillation without reaction are examined and applied to reactive distillation. It will be shown that the widely used strategy of total reflux is not suitable for reactive distillation. A simplified model to derive a time constant which describes the influence of parameter setting changes, like heating power, reflux ratio and feed composition on the start‐up time, is introduced and validated.     

有机硅单体合成的气固流化床的三维数值模拟

为了探索有机硅单体合成气固流化床内硅粉颗粒的流化特性,作者利用计算流体力学CFD软件,采用双欧拉气固两相流模型及SIMPLE算法,模拟了三维的气固流化床内硅粉颗粒的流化特性;分析了气泡生成、长大和破裂的过程,及不同床层高度的固体颗粒运动速度矢量图,不同床层高度处横截面颗粒体积分数变化。结果表明:三维模拟能直观的表现颗粒在流化床中的流化状态,为工业生产及应用提供了有效的依据。     

Three Dimensional Simulation of Liquid Flow on Distillation Tray

The liquid flow on a single-pass sieve distillation tray is simulated with a three-dimensional computational fluid dynamics (CFD) program with the K-ε turbulence model. In the model, a source term SMi is formulated in the Navier-Stokes equations to represent the interfacial momentum transfer and another term SC is added to the mass transfer equation as the source of interfacial mass transfer. The simulation provides the detailed information of the three-dimensional distribution of liquid velocity on the tray, the circulation area and the concentration profile along the height of liquid layer.     

搅拌槽内固液两相流的数值模拟及功率计算

使用计算流体动力学的方法对搅拌槽中的流场进行模拟,得到搅拌槽中液体的流动状况和体积分数分布。对流场分布规律、固体颗粒体积分数特点加以分析,进而利用模拟出的数据计算搅拌轴的功率,为搅拌器的设计提供参考。     

直接接触式膜蒸馏的技术方案分析

分别介绍了多效膜蒸馏、太阳能膜蒸馏、热泵膜蒸馏三种典型技术方案的流程、工作原理和基本特点,并以产水量1000 kg/h为例,计算比较了三种技术方案的造水比、设备费用、运行能源费用、膜费用、总运行费用等关键技术经济指标。结果表明,多效膜蒸馏对运行操作温度较高的非热敏料液具有较好的应用优势;太阳能膜蒸馏对不要求连续操作,且太阳能资源丰富的场合较适用;热泵膜蒸馏可用于不同操作温度的料液,尤其是应用于操作温度较低的热敏料液时具有突出的优势。     

搅拌釜内流场三维数值模拟及功率预测

大型搅拌釜,尤其是涉及传热或两相介质搅拌的容器,其搅拌效果和功率往往难以预测。针对大型搅拌釜的搅拌器设计、流场结构模拟和功率预测等问题,采用CFD数值模拟技术,对搅拌釜内部的三维流场进行了数值计算。分析了搅拌釜内的流动结构,计算了不同曝气量时的搅拌功率,获得了详细的流场信息和各项特性参数。     

甲醇精馏工艺模拟计算及分析

利用化工模拟软件PRO/II对甲醇精馏的三塔和双塔两种不同流程进行模拟计算,并从能耗、设备投资等方面对这两种流程作比较分析。     

甲缩醛反应精馏过程模拟

通过实验取得了甲醛和甲醇合成甲缩醛的反应参数;建立了其连续生产工艺的数学模型,利用ASPEN PLUS软件对甲醛和甲醇缩合生成甲缩醛进行了模拟,结果表明反应精馏连续生产甲缩醛的工艺是可行的,转化率高达99%,并得到含甲缩醛99%的产物,同时确定了进料板和反应区.     

膜蒸馏分离聚酯废水中微量乙醛的研究

本文采用膜蒸馏技术分离聚酯废水中的乙醛,通过实验比较了聚四氟乙烯微孔膜和聚偏氟乙烯微孔膜的分离性能,并考察了膜室温度、进料乙醛浓度和冷侧真空度列聚四氟乙烯微孔膜分离性能的影响。     

原油常减压蒸馏塔的流程模拟

常减压蒸馏装置是炼油加工的第一道工序,它的运行状况对后续装置乃至全厂都有着重要影响。针对初馏塔、常压蒸馏塔和减压蒸馏塔的稳态流程模拟,选取适合的蒸馏塔中段循环设定变量和减压塔模拟方法,最终流程模拟结果与实际工艺参数相似度极高,说明常减压蒸馏塔的流程模拟能够如实体现实际工艺状态,可以作为指导工艺生产、操作优化的有效方法。     

Agglomeration in Spray Drying Installations (The EDECAD Project): Stickiness Measurements and Simulation Results

Spray drying is used for the manufacture of many consumer and industrial products such as instant dairy and food products, laundry detergents, pharmaceuticals, ceramics, and agrochemicals. During spray drying, agglomerates of powder particles are formed that determine the instant properties of the powder. Agglomeration during spray drying is considered to be a difficult process to control. The main cause of this is the complex interaction of the process variables: the atomization process, the mixing of spray and hot air, the drying of suspension droplets, and the collision of particles, which might lead to coalescence or agglomeration. As a consequence, agglomeration during spray drying is operated by trial and error. In an EC-sponsored project, named the EDECAD project and coordinated by NIZO food research, an industrially validated computer model, using CFD technology, to predict agglomeration processes in spray drying machines is developed. A Euler-Lagrange approach with appropriate elementary models for drying, collision, coalescence, and agglomeration of the dispersed phase is used. The main result of the EDECAD project is a so-called design tool, which establishes relations between the configuration of the drying installation (geometry, nozzle selection), process conditions, product composition, and final powder properties. The design tool has been validated on pilot plant scale and industrial scale. This article presents the setup and results of dynamic stickiness tests and some CFD simulation and validation results.     

丁醛精馏塔流程模拟与优化

利用Aspen-plus流程模拟软件对丁辛醇装置丁醛精馏塔建立流程模拟模型,比较模拟结果与设计值,通过灵敏度分析,确定最佳操作参数条件.     

Agglomeration in Spray Drying Installations (The EDECAD Project): Stickiness Measurements and Simulation Results

Spray drying is used for the manufacture of many consumer and industrial products such as instant dairy and food products, laundry detergents, pharmaceuticals, ceramics, and agrochemicals. During spray drying, agglomerates of powder particles are formed that determine the instant properties of the powder. Agglomeration during spray drying is considered to be a difficult process to control. The main cause of this is the complex interaction of the process variables: the atomization process, the mixing of spray and hot air, the drying of suspension droplets, and the collision of particles, which might lead to coalescence or agglomeration. As a consequence, agglomeration during spray drying is operated by trial and error. In an EC-sponsored project, named the EDECAD project and coordinated by NIZO food research, an industrially validated computer model, using CFD technology, to predict agglomeration processes in spray drying machines is developed. A Euler-Lagrange approach with appropriate elementary models for drying, collision, coalescence, and agglomeration of the dispersed phase is used. The main result of the EDECAD project is a so-called design tool, which establishes relations between the configuration of the drying installation (geometry, nozzle selection), process conditions, product composition, and final powder properties. The design tool has been validated on pilot plant scale and industrial scale. This article presents the setup and results of dynamic stickiness tests and some CFD simulation and validation results.     

生物反应器的CFD模拟及结构设计

利用计算流体力学（CFD）软件Fluent,以多重参考系法对发酵行业中的发酵罐搅拌流场进行整体数值模拟。基于标准的κ-ε紊流模型模拟了发酵罐内的流场分布,分析了垂直面和水平面上液相流的流场分布及规律,可为搅拌器的结构设计提供参考。     

间歇精馏模拟计算及试验验证

采用模型模拟计算处理间歇精馏过程,模拟计算采用两点隐合法处理积分方程,用改进的θ校正法校正浓度,组分加和平衡和能量平衡分别校正各板的温度和汽相流率,利用UNIFAC方程计算汽液平衡,通过计算得到间歇精馏塔塔内的动态变化数据.用间歇精馏的试验数据验证数学模型的正确性和计算方法的可靠性,并通过模拟优化试验参数.     

醋酸水体系共沸精馏过程的模拟研究

利用PRO/II软件对醋酸-水-醋酸丁酯体系的共沸精馏进行模拟计算,用Hayden-O’Connell方程计算气相逸度系数,用NRTL方程计算液相活度系数。用实验数据验证模拟结果,结果表明,模拟计算所得的沿塔温度和各组分浓度分布曲线与实验数据相吻合,醋酸-水-醋酸丁酯体系的精馏是一个汽-液-液三相共沸精馏,加料口以上为三相区,加料口附近为三相到两相的过渡区,加料口以下为两相区。     

醋酸甲酯水解催化精馏过程的模拟计算

采用非平衡级速率模型对醋酸甲酯水解的催化精馏中试过程进行了模拟计算,考察了回流进料比、进料水酯比和酯进料位置等的变化对醋酸甲酯水解率的影响, 不仅证实了中试实验所得的结论,还获得了难以通过实验取得的结果.