生产无机盐的主要过程及设备——过滤(概述)

<正>过滤是一种分离悬浮在液体或气体中的固体颗粒的操作,现仅讨论悬浮液的过滤。悬浮液称为滤浆,滤浆中的固体颗粒称为滤渣,积聚在过滤介质上的滤渣称为滤饼,透过滤饼和过滤介质的澄清液体称为滤液。评价过滤操作优异的标志之一是过滤速度,影响过滤速度的因素主要有压力差、过滤面积、滤饼的阻力、滤液的黏度、过滤介质和最初滤饼层的     

等压滤饼过滤过程中过滤介质阻力定量变化规律的探讨

正液固过滤基本分为滤饼过滤与澄清过滤两大类。滤饼过滤通常比澄清过滤更难、更复杂。传统的过滤理论认为在整个滤饼过滤过程中其过滤介质的阻力是不变化的。各种过滤文献与传统的过滤教科书中,都认为过滤介质阻力是常数。如果液体料浆中固体颗粒的大小均大于过滤过滤介质的毛细孔径,颗粒尺寸较均匀,颗粒的刚度较大,在过滤过程中不易被挤压变形,或挤成局部碎裂,     

管式压滤机的实验研究

采用不同结构的过滤元件和不同的过滤介质 ,在不同的压力条件下进行交叉过滤实验 ,从中得出管式过滤机的基本规律 :纯净液渗透率公式和悬浮液渗透率公式以及各种情况下的阻力表达式。对不同结构的过滤元件在过滤过程中对操作的影响进行了实验分析。结果表明 ,不同的过滤元件有不同的优点 :簧管式过滤元件能形成稳定的滤饼层 ;支杆式过滤元件则对滤饼有自清作用     

污泥机械脱水——加压过滤的设计计算

本文推导了污泥脱水的加压过滤方程,得出不可压缩滤饼及可压缩滤饼污泥在恒压,恒流率和变压,变流率情况下的计算公式,举例说明板框压滤机进行污泥脱水的设计计算方法,此法的基本原理同样适用于微孔管板及叶片式加压过滤机械。在污泥机械脱水的设计,运行中,实践证明不同类型污泥或同一类型污泥在不同工作条件(温度、压差)下的滤饼比阻均不同;而不同过滤介质或同一过滤介质在不同的工作条件(污泥性质、过滤压差……)下的介质阻抗也不同。因此,一定要通过模拟试验测定并计算它们,然后再按具体的脱水工况计算脱水机械的参数(过滤面积、压差,一个过滤周期的历时……)。与此同时还可对需脱水的污泥按不同介质,不同工况做多方案比较从中择优选用。以下介绍部分压滤机的模拟试验装置及加压过滤进行污泥脱水的设计计算方法。     

滤饼结构的分形研究

概括地介绍了分形理论在滤饼结构研究中的应用 ,并采用电子扫描与计算机图象处理技术 ,并根据分形理论对以平板陶瓷膜为过滤介质的十字流微滤稳态阶段的滤饼结构进行了理论及实验研究。     

气液固三相浆态搅拌反应器中管式内过滤器的过滤特性研究

探讨了在气液固三相浆态搅拌反应器中设置管式内过滤器，以实现气液固三相分离及浆态反应器的连续化。冷模研究表明：在强烈搅拌下，存在一种动态平衡过滤。即在滤饼沉积速率及剥离速率达到平衡条件下，可实现液相进料及滤液排料的连续化。在确定适宜过滤元件结构及过滤介质后研究了搅拌速度 、固含率、体系性质等因素对气液固三相浆态搅拌釜中管式中管式内过滤器的过滤速率的影响。气相按一定比例随液相通过过滤介质 ，其比例大小取决于过滤器的压降大小。实验表明：对颗粒平均直径在（0.8-1.0)10^-4m的α一氧化铝及硅铝氧化物细粒可获得较满意的分离效果。     

过滤和脱水装置的选型

同沉降分离一样,过滤和脱水也是借助机械手段进行固液分离的单元操作。过滤分离是机械分离法的代表,按照过滤机不同可分成两类:一类称为滤饼过滤或表面过滤,即在过滤刚开始的一段时间里,首先由滤布等过滤介质捕捉固体粒子,待滤饼形成后,便由滤饼起过滤介质的作用,并以其表面来捕捉固体粒子;另一类称为介质过滤,也称闭塞过滤或者澄清过滤,即当滤浆的固体浓度低于0.1％(体积)或者粒子非常细小时,是以闭塞过滤介质孔隙的入口处或者孔隙的内部来捕捉固体     

微米级高分子精密过滤技术及其在精细化工、水处理与环保领域的应用

微米级高分子精密过滤既能澄清过滤 ,也能滤饼过滤 ,还能卸干滤饼 ,过滤介质能高效再生 ,耐化学性能好 ,是一种使用寿命长的新型过滤技术。主要介绍了该技术的组成特点及其在精细化工、水处理及环保领域的主要应用。     

熔融结晶洗涤塔内过滤过程的研究

针对熔融结晶洗涤塔的过滤操作模式,根据表面过滤原理分析了洗涤塔内过滤段的物理模型和数学模型,建立了过滤微分方程和相关边界条件;通过过滤方程的求解,建立了过滤段滤饼过滤的压力分布公式以及滤液体积流率与滤饼变化厚度的关系式,并对相关主要影响因素进行了分析。结果表明,洗涤塔过滤段滤液体积流率与压力降、比滤阻、过滤介质阻力、滤...     

滤饼孔隙率的模拟研究

采用计算机模拟方法,对滤饼中颗粒的凝聚机理进行简化,将所过滤的物料外形形态简化为球形颗粒,进行计算机程序设计,模拟物料在纤维过滤介质中过滤形成滤饼的过程,模拟得出滤饼结构,并进行孔隙率计算,在简化模型的基础上,分析滤饼孔隙率,滤饼厚度以及固体颗粒粒径的相关关系,探索滤饼结构研究的新方法及新途径。     

基于自然高差△h的甩车场设计方法

为了研究双道起坡甩车场斜面线路和竖曲线连接的设计方法,通过剖析自然高差△h及△L的成因以及它们对甩车场设计的影响,指出《采矿工程设计手册》中双道起坡甩车场设计存在的问题,并得出基于自然高差△h的双道起坡甩车场设计的图形标示及计算公式。并对双道起坡甩车场一点落平法进行了分析和探讨。     

Experimental investigation on bubbling behavior in anode channel of passive DMFC

将被动式DMFC阳极通道内气泡形成过程简化为CO₂气体注入充满静态甲醇溶液中形成气泡的过程。利用可视化实验研究了气体垂直注入静态甲醇溶液中形成气泡以及气泡脱离的过程,考察了气体流量、液层高度、孔径大小、甲醇浓度对气泡形成及长大脱离过程的影响。结果表明：在气泡的生长过程中,接触角先是快速下降后又迅速上升,然后趋于稳定值直到脱离。随着气体流量的增加,脱离时气泡的直径变化甚微,脱离时间先下降较快后趋于稳定。随着液层高度的增加,气泡的脱离直径变小,产生的频率加快,脱离时间先是减小后趋于稳定;气体流量在此条件下对脱离时间的影响减弱。随着孔径的增加,气泡的脱离直径增加,产生气泡的频率减慢,气泡的脱离时间减小。随着甲醇浓度的增加,气泡的脱离直径变小且波动明显,气泡产生的频率变快,脱离时间先是减小后趋于稳定,对低浓度的溶液影响较为明显。     

A Novel Technique for Evaluating the Work of Adhesion

One of the basic problems which one encounters in bonding dissimilar materials such as glass and polymers is the development of internal stresses. These stresses arise primarily as a result of the difference in their thermal coefficients of expansion. Other stresses may also occur due to the processing history of the polymer, swelling of the polymer due to the absorption of gases in the environment or internal reaction products, and/or the loss of absorption of solvent from the adhesive. As a result, it is obvious that techniques designed to evaluate adhesion must evaluate the effects of these intrinsic stresses without modification by the external imposed stresses of the test. For example, Ahagon and Gent evaluate a work of detachment from the time average of the 180° peel force per unit width of the detaching layer.¹ However, Gent and Hamed have recently shown that this mode of peeling involves deformation of the detaching layer due to bending.² Similar problems are encountered in other techniques used to measure adhesion.     

Peel Mechanics

Published treatments of peel mechanics are shown to yield inconsistent relations for the dependence of peel force upon the angle of peel. The paradox is resolved by limiting the stress analyses to small bending deformations of the detaching strip in the still-attached region. This condition holds when the moment arm of the applied peel force is much larger than the length of the high-stress region in the bond, which must therefore be considered a prerequisite for use of the published bond stress distributions.

Failure of some experimental results to conform to the theoretical dependence of peel force upon peel angle are ascribed to inelastic deformation or stretching of the detaching strip.     

Tensile,Knot, and Detaching from Needle Performances of Atraumatic Surgical Sutures

In this study, atraumatic surgical sutures were used to investigate the effects of different structural parameters on tensile properties of unknotted and knotted (one, two, and three) sutures. Besides tensile properties, an important and crucial property namely detaching from needle property of the sutures were examined. Atraumatic surgical sutures having different lifetime in the body (nonabsorbable and absorbable), different raw materials (polypropylene [PP], silk, polydioxanone [PDS], polyglactin 910 [PGA]), different yarn structures (monofilament and braided), and different size numbers (2/0, 3/0, and 4/0 USP) were tested and variance analyses were used to examine the effects of structural parameters on test results. Tensile test results revealed that the presence of knot causes noticeable reduction in the breaking load values. However, the knotted sutures with varying throw number of knots were determined to have similar breaking properties. In addition, breaking load and detaching force from needle decrease with increasing size number of the sutures. In the case of the same size number and the same throw number of knot, absorbable sutures have higher breaking load results than non-absorbable sutures and braided sutures are stronger than monofilament sutures used in the study.     

The isolation and characterisation of grafts from glass surfaces and their immiscibility with homopolymer

A procedure for photochemically detaching, isolating and characterising grafts (produced by a method developed previously by the authors) from glass surfaces is described. Preliminary results indicate that the molecular weights and molecular weight distributions can be varied through control of the kinetics of graft formation; our previous studies are seen to have produced a high surface coverage of grafts of high molecular weight. A thermodynamic argument is developed to explain the immiscibility of grafts with free homopolymer for high surface coverage by grafts from which it is seen that the immiscibility is entropy-driven. Comparisons are drawn between our previous studies and relevant studies by other workers and apparent anomolies are explained.     

Particle adhesion and removal in electrophotography

Particle adhesion and removal is often controlled by the interplay of electrostatic forces, related to electrical charges on the particles, and electrodynamic forces, such as those arising from van der Waals interactions. In addition, when electrostatically detaching a charged particle from a substrate, the manner in which the electric field is applied can alter the charge on the particle, thus changing both the attractive and detachment forces. The effects are clearly illustrated in the transfer of a toned image from the photoconductor in an electrophotographic engine. This paper reviews present day understanding of the interplay between electrostatic and electrodynamic interactions, as they occur within the electrophotographic process, and presents the results of previous studies in a unified manner.     

真空膜蒸馏海水淡化技术研究进展分析

真空膜蒸馏海水淡化运行压力低、截留率高、设备简单,可充分利用舰船动力系统冷却海水余热,有望用于新型舰船海水淡化装置研制.文中总结了真空膜蒸馏海水淡化主要特征、过程机理,分析真空膜蒸馏海水淡化过程的影响因素:膜疏水性与结构参数、海水温度与流速、操作真空度及膜污染,并在此基础上展望膜蒸馏海水淡化技术的未来研究方向.     

涤/锦复合超细纤维结构与性能的关系

分别用酸性处理剂GS和碱性处理剂GJ对莲花瓣型和桔瓣型PET/PA6复合纤维(织物的纬纱)进行化学处理,并得出最佳工艺条件。分析了化学处理方法对纤维的作用机理及处理前后复合丝力学性能的变化,用显微镜对纤维截面和表面进行观察并照相,分析其剥离效果。     

Free-Standing TiO2 Nanotube Arrays for Front-Side Illuminated CdS Quantum Dots Sensitized Solar Cells

Front-side illuminated CdS quantum dots (QDs) sensitized solar cells (QDSSCs) based on TiO₂ nanotube arrays (TNTAs) were fabricated. The free-standing TNTAs (f-TNTAs) membranes were obtained from anodic oxidized Ti foils by self-detaching technique and then transferred to FTO glass substrates to form photoanodes. CdS QDs were loaded on TNTAs by sequential chemical bath deposition approach. Scanning electron microscope (SEM) results indicated that the morphology and structure of TNTAs membranes did not change in detaching and transferring process. Power conversion efficiency of the devices from the front-side illumination mode is 1.47 %, which is much higher than that (0.34 %) of the back-side illumination mode owing to the markedly improved light absorption.