加压下规整填料塔内气液两相流返混的实验研究:气相返混系数

规整填料因具有生产能力大、分离效率高、压降低、操作弹性大、持液量低等诸多优点 ,目前已被广泛应用于精馏、吸收及萃取等多种化工单元操作中 .通常只在常压或减压条件下操作 ,而在高压或大液相负荷下 ,因流体物性的变化及流动状态的改变 ,使塔内产生严重的返混 ,塔效率显著降低 .因此 ,研究加压下规整填料塔内流体的流动状态具有重要意义 .对于加压下填料塔内气相返混的研究 ,中国台湾的ＴａｎＣｈｕｎｇ -Ｓｕｎｇ[1] 在低实验气速 (0 .0 0 2～ 0 .1ｃｍ·ｓ- 1)下做过初步的研究 ,其实验填料为散堆填料 .Ｋｕｒｔｚ[2 ] 在这方面的研究…     

规整填料在加压精馏中的传质性能

高压精馏是现代过程工业中十分重要的分离过程 ,例如炼油工业中轻烃的分离 ,石油化工中乙烯、丙烯等低碳烃类的分离 ,都是经过高压精馏完成的 .高压精馏效率一般较在常压下有所降低 ,其中填料塔较板式塔下降更明显 ,故通常认为采用板式塔比较好 .但规整填料由于其大通量、低压降等优点 ,已经开始涉及高压领域 ,因此对规整填料在高压下的性能需进行测定和研究 .目前 ,对规整填料在高压下传质性能的研究 ,国外ＦＲＩ[1] 近年已开始进行 ,但其实验数据较少 ,在国内目前还属空白 .本文在国家重点精馏分离实验室高压热模精馏实验塔上进行了一系列…     

填料塔高压蒸馏研究进展

介绍了填料塔高压蒸馏领域的最新研究成果,并从压力对体系物理化学性质、流体流动及分布的影响出发,分析了压力对填料塔高压蒸馏的影响。结合最新的试验结果,分析了规整填料高压蒸馏下“效率驼峰”的形成原因。对目前规整填料传质模型进行了评价。     

汽—液—液三相与汽—液两相塔板效率比较

本文通过小型精馏塔及600×150 mm~2矩形模拟塔的实验,对比研究了气(汽)-液两相和气(汽)-液-液三相的塔板效率。并就物系性质(表面张力梯度、液体粘度或分散粘度),两液相体积比,气速及操作工况对传质的影响进行了研究。提出三相传质和两相传质差异的主要因素,得出估算三相精馏塔板效率的关联式。     

液相流动方式对波纹规整填料性能的影响

根据液相在波纹规整填料片上呈现渗流、膜状流等不同的流动方式,选择5种不同的波纹规整填料对其流体力学和传质性能进行研究,以探究液相在波纹片上的流动方式对波纹规整填料性能的影响.研究结果表明,液相呈渗流流动的泡沫碳化硅波纹规整填料(SCFP型)有利于液体横向扩散和液膜均匀分布,当液相喷淋密度和气相F因子均较小时,其压降最低,传质效率最高;液相主要呈渗流流动、兼有膜状流动的双层错孔丝网填料(DMⅢ型)有利于波纹片两侧液体交换,强化液体在流动过程中的扰动,其压降及传质性能略逊于SCFP型填料;液相主要呈膜状流动的BX型、DMⅠ型及DMⅡ型填料波纹片表面液膜较厚,横向扩散能力差,其传质效率低于SCFP型和DMⅢ型填料.研究揭示了依靠渗流作用的波纹规整填料具有较好的应用性能,为波纹规整填料的进一步发展开拓了新思路.     

复合规整填料塔中的液相混合

引　言复合规整填料是由两种比表面积相差较大的规整填料复合而成 ,与普通规整填料相比 ,具有操作弹性大的优点 ,特别适用于气液通量大的操作场合 ,如原油减压蒸馏等 .复合规整填料内液相混合行为复杂 ,对传质过程有重要影响 .但到目前为止 ,人们仅对散堆填料塔中液相混合有较多的研究[1～ 6] ,而且不很成熟 ;对规整填料塔及复合型规整填料塔的研究就更不足 .为了促进复合型规整填料的开发和应用 ,本文对复合规整填料Ｍｅｌｌａｐａｋ(12 5Ｘ +2 5 0Ｙ)中的液相混合进行了研究 .1　模　型目前常用的描述填料塔中液相混合行为的模型是扩散型…     

以AMP分离二氧化碳时用的高效规整填料

研究了以２氨基２甲基１丙醇（ＡＭＰ）分离二氧化碳过程中采用高效规整填料的可行性。在二氧化碳分压～１０ｋＰａ、气体流率０．２９～０．６１ｍ３／（ｍ２·ｓ）、液体流率４．８７～１４．１８ｍ３／（ｍ２·ｈ）和液相浓度１．１～２．０ｋｍｏｌ／ｍ３条件下，通过二氧化碳吸收于氢氧化钠和ＡＭＰ水溶液中的总传质系数评价了填料的性能。试验结果表明规整填料所提供的总传质系数为通用散堆填料的１０～３３倍。     

规整填料塔的设计计算模型

针对规整填料塔的特点和近年来的研究进展 ,分析了规整填料内的流体力学和相间传质行为 ,并对规整填料塔内压力降、液泛及气液传质设计计算模型进行比较 ,同时指出了高压填料塔设计计算中应注意的问题。     

真空填料精馏塔的性能

在四种不同结构的塔中,采用两种小型散堆填料和三种回流比,在(5～50)×1.333×10~2Pa的塔压范围内,针对操作压力、空塔汽速、回流比、填料类型和塔的结构对传质效率的影响进行了真空精馏研究。实验研究表明,真空填料精馏过程中存在一个最佳的塔压值和一个最佳的回流比值。改进后的塔型对提高传质效率有利。     

波纹板规整填料塔液体分布

将填料单元处理成立体节点网,根据节点网内网线液流和节点液流各自的运动方式建立了填料单元的液体分布模型.通过将填料与塔壁间的液体交换规范成填料节点网与塔壁节点网间的液量传递建立了填料单元对应塔壁区的流体分布模型.提出了规整填料塔液体分布问题的边界条件.2个描述填料单元及其对应塔壁区液体分布的数学模型与2类边界条件共同构成了波纹板规整填料塔的液体分布模型.采用单纯形法对3个模型参数进行了估计.模型计算结果与实验数据一致,表明模型能合理地描述波纹板规整填料塔的液体分布性能.     

在高压下规整填料中的流动实验研究

Both distillation performance and hydrodynamic study for backmixing by tracer technique were carried out in a high-pressure packed column with 0.15 m inner diameter over a wide range of operating conditions. Isobutane and n-pentane are employed as test mixture in the distillation experiment and air/water is used for the hydrodynamic study. The column is installed with Mellapak 350Y structured packing and the total packing height is 2.0 m. With the increasing operating pressure, the separation efficiency increases slightly while the F-factor corresponding to the maximum efficiency at each pressure is descending. It is noted that, at all operating pressures, with the increase of F-factor, the packing efficiency is slightly higher up to the flooding point. The application of SRP model to high-pressure distillation gives much lower values of HTUOG than those obtained experimentally. An additional term, the height of mixing unit, is introduced to correct the SRP model and improve its accuracy at high pressure. From the tracer experiments, the height of mixing unit for gas phase was found to be larger than that for the liquid phase. From this viewpoint, it is believed that the gas phase backmixing gives more unfavorable influence on the separation efficiency in comparison with liquid phase.     

Mechanical properties of high‐density polyethylene/scrap rubber powder composites modified with ethylene–propylene–diene terpolymer,dicumyl peroxide,and silicone oil

The effect of ethylene–propylene–diene terpolymer (EPDM), dicumyl peroxide (DCP), and dimethyl silicone oil on the mechanical properties of high‐density polyethylene (HDPE) composites filled with 60 mesh cryogenically scrap rubber powder (SRP) was studied. The addition of 10 wt % EPDM, 0.2 wt % DCP, and 4 wt % dimethyl silicone oil significantly increased both the impact strength and elongation at break of the HDPE/SRP composites. After the modification, the impact strength increased by 160%, and the elongation at break increased by 150% for the composites containing 40 wt % SRP. The impact load–time curves showed that the increase of impact energy for the modified composites was attributed to the increase of the maximum force at yield point and the ductile deformation after yielding. The rheological behavior, dynamic mechanical properties, and morphology observation suggested that an enhanced adhesion between SRP and polymer matrix formed in the modified HDPE/SRP composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2020–2027, 2003     

空分填料塔设计中的流体力学特性

空分精馏主要在-200℃左右的深冷条件下进行,填料塔内流体力学特性参数难以由试验直接获取,如何将常压常温状态(简称常态)下空气-水物系的流体力学测试结果转换适用于空分设计变得尤为关键。通过Bain-Hougen公式及SRP(Ⅱ)模型结合Sp iegel持液量计算推导出泛点及压降关联式以预测填料的流体力学特性。对空分中常用的750Y型金属孔板波纹填料进行常态下流体力学特性测试,结果表明:采用的方法可用于填料流体力学特性的预测。对空分状态下的泛点与压降结果预测表明,空分设计中采用常态下的流体力学数据进行设计偏于保守。     

新型高效规整填料的性能研究

为了获得可靠的设计依据,实验在不同回流比条件下,用环己烷-庚烷和庚烷-甲苯2种二元测试物系对CDG1700Y和CDG2500Y型金属丝网规整填料的流体力学性能和传质性能进行了考察。实验结果表明,这2种填料的压降随着液体流量的增大而增大,单位填料层高度的HETP变化趋势则相反;CDG1700Y和CDG2500Y型填料具有较高的理论板数,且CDG1700Y型填料具有较大的操作弹性。在SRP(II)模型的基础上,获得了实验室条件下传质单元高度的经验关联式,其计算值与实验结果吻合较好,可以为化学交换法分离硼同位素的工业化提供理论指导。     

PREDICTION OF PRESSURE BUILD UP IN A MICRO CAPILLARY DUE TO PARTICLE RETENTION

A single capillary model is proposed to predict the increase in pressure drop due to the particle deposition. The model is based on mass balance and trajectory analysis considering physical force (London—Van der Waals), hydrodynamic force (gravity and drag) and electrokinetic force (double layer). The validity of the model was tested experimentally by simulating a micro-capillary of radius 34.37 μm and circulating bentonite suspension at different flow rates and concentrations. The model is valid for predicting the pressure build up due to smooth deposition of particles with minimal surface energy.     

Thermoplastic Elastomers Derived from Scrap Rubber Powder/LLDPE Blend with LLDPE‐graft‐(Epoxidized Natural Rubber) Dual Compatibilizer

Summary: Attempts were made to prepare thermoplastic elastomers (TPE) from scrap rubber powder (SRP) and linear low‐density polyethylene (LLDPE) as thermoplastic polymer matrix. The solid‐phase grafted copolymer of LLDPE (LLDPE‐g‐VM) and epoxidized natural rubber (ENR) were used as dual compatibilizers to improve the interfacial adhesion between SRP and LLDPE. The compatibilized SRP/LLDPE blends had obviously improved the interfacial properties between SRP particles and LLDPE. Using this method, thermoplastic elastomer was prepared successfully. The mechanical properties especially elongation at break was improved significantly. SEM and TEM studies showed that the ENR/LLDPE‐g‐VM dual compatibilizer improved the distribution state of SRP particles in LLDPE and the adhesion between SRP and LLDPE. DSC results showed a distinct glass transition at 74 °C of the interfacial region. The improvement in mechanical properties was attributed to the enhanced interfacial properties of the blend.

Surface of SRP particles of the composites compatibilized by the dual compatibilizer.     

PERFORMANCE CHARACTERISTICS OF A CERAMIC MEMBRANE SYSTEM FOR MICROFILTRATION OF CORN STARCH HYDROLYSATE

A ceramic microfiltration membrane was used for the clarification of corn starch hydrolysate, having a dextrose equivalence of 95, to study the effect of process variables (transmembrane pressure, cross-flow velocity, and feed concentration) on permeate flux. Flux increased with increased cross-flow velocity for all transmembrane pressures and feed concentrations up to a volume concentration ratio of 100. Flux became asymptotic at pressures of 200-375kPa, indicating that microfiltration performance was limited by concentration-polarization. The optimum transmembrane pressure was higher at higher cross-flow velocities. A process model based on the resistances-in-series concept adequately described the observed variation of permeate flux with process variables such as transmembrane pressure, cross-flow velocity and feed concentration. Resistance due to concentration polarization decreased linearly with increase in cross-flow velocities for all feed concentrations, while fouling resistance increased linearly with increase in feed concentration.     

The Effect of Ozone Gas on IL-1β and IL-10 Levels of Gingival Crevicular Fluid in Aggressive Periodontitis Patients

ABSTRACT

Although the use of ozone therapy in dentistry has become widespread, the number of controlled clinical trials evaluating its effectiveness in periodontal therapy is limited. The aim of this study was to evaluate the efficacy of ozone treatment, that is used in concert with scaling and root planning (SRP), on clinical periodontal parameters and to analyze its effect on cytokine levels of GCF in aggressive periodontitis patients. Totally, 27 patients with aggressive periodontitis were randomly selected into groups of treatment with either subgingival SRP followed by application of ozone with a periodontal probe (SRP+ozone) or subgingival SRP followed by irrigation with serum irrigation (SRP-control). The following parameters were evaluated at baseline (T0), and 6 weeks (T1): plaque index (PI); gingival index (GI); probing pocket depth (PPD), clinical attachment loss (CAL), GCF volume, GCF Interleukin-1β (IL-1β), and GCF Interleukin-10 (IL-10) cytokine levels. There was a significant difference in terms of clinical periodontal parameters before and after treatment in both groups. When comparing between groups, there was no significant difference between the treatment methods after 6 weeks with respect to the PI, PPD, CAL, and GCF IL-10 levels. In contrast, GI, GCF volume, and GCF IL-1β levels were statistically significantly different between the two groups at the 6th week after treatment. Application of ozone as an adjunctive therapy to SRP was shown to provide a statistically significant improvement in treatment results compared to SRP plus serum irrigation.     

加压喷动床中细颗粒喷动特性

在内径分别为 186mm和 80mm的加压喷动床中 ,以空气为喷动介质 ,在 10 1～ 70 0kPa的压力范围内考察了几种不同粒度的细颗粒在加压下的喷动特性 .研究结果表明在不同的Re_t 内压力对最小喷动速度的影响不同 .实验还发现 ,随着压力的升高 ,喷动区直径增大 ,稳定操作区域增大 ,加压可明显改善喷动床的操作稳定性     

废胶粉的改性及其在砂浆中的应用

通过表面接枝改性制备了改性胶粉SRP。利用高分辨裂解气相色谱－质谱联用仪（PyGC-MS）和FTIR对SRP的结构进行了分析,测试结果表明,SRP已接枝上磺酸基团。对改性胶粉/砂浆的工作性能和力学性能进行了研究。通过流动度及流动度损失的测定,找出了胶粉（RP）和改性剂的最佳用量比;同时结果表明,改性胶粉SRP可以有效改善砂浆的流动性,并减小流动度损失;在力学性能方面,RP/砂浆复合材料的抗压和抗折强度都大幅下降,而对SRP/砂浆复合材料在保证其抗压强度的同时,实现了抗折强度的提高,材料表现出一定的韧性。胶粉改性方法简单,有利于工业生产。