Dewatering of spontaneous-coagulation-cast alumina ceramic gel by filtrating with low pressure

Water removal in colloidal processing is a tough and crucial problem because deformation and cracking of the wet body easily happen during the drying process. Inspired by conventional pressure filtration (PF), we combined spontaneous coagulation casting (SCC) with PF to partially remove water from the gelled sample before drying for the purpose of lessening the risk of cracking and shortening the drying period. The effect of pressure, holding time, and solid loading on the particle packing ratio of wet samples, the drying process, and the bulk density and homogeneity of green and sintered bodies was surveyed systemically. The PF process of 0.4 MPa for 2 h was optimized based on dewatering ratio from ceramic slurries. The particle packing ratio of the pressure-filtrated samples increased with the solid loading of ceramic slurries, and 61 vol% was obtained for the slurry with 56 vol% solid loading. The drying time of the pressure-filtrated samples was shortened by as much as 42%–53% compared with that of the gelled samples, and the linear shrinkage for the pressure-filtrated samples during drying was only approximately 0.5%, much smaller than that of the gelled samples (2.4%–4.6%). Furthermore, the bulk density of the pressure-filtrated green bodies was more than 2% higher than that of the gelled green bodies, and more homogeneous green bodies were obtained by PF than by SCC. The alumina ceramic with 98.8% relative density and a homogenous density distribution was obtained after being sintered at 1550 °C for 2 h.     

细颗粒杂质旋流脱水油田现场试验研究

针对大庆油田现场实际情况 ,在原有室内实验研究的基础上 ,采用水力旋流器对细颗粒杂质的分离处理做了试验研究。试验结果表明 ,随流量的加大脱水率有增加的趋势 ,最高可达 90 %左右 ,但并非流量越高越好 ;分流比为 8.75 %以下时效果较为理想 ,但分流比过小时 ,旋流器底流管路中出现明显堵塞现象 ;5°锥角旋流器的分离效果要优于 8°锥角旋流器 ,且压力损失相对较低。初步试验研究表明 ,采用水力旋流器对油田污水中的细颗粒杂质进行处理是可行的     

Compression Dewatering of Particulate Suspensions and Sludge: Effect of Shear

Experiments were carried out at the lab-scale to study the effect of a shearing action in a compression dewatering process. The impact of different process parameters, such as shear rate, filter-cake thickness, and pressure, on the final dry solid fraction was analyzed. Also, materials with different degrees of compressibility have been used. For slightly and moderately compressible materials (talc and kaolin, respectively), significantly higher final dry solid fractions (up to 0.79 wt/wt with talc and 0.75 wt/wt with kaolin) were obtained in the presence of a torsion shear. This behavior may mainly be explained by a rearrangement of the solid particles within the cake induced by the radial forces. A low shear rate (around 0.7 s^?1) was generally sufficient to cause a quite significant increase in the cake dryness (a 12.8% increase was observed with 11-mm-thick talc cakes). A further increase in the shear did not lead to noticeable changes in the final dry solid fraction in the cakes. Otherwise, reducing the filter-cake thickness was beneficial for the dewatering. For talc cakes, the dry solid fraction was increased by 21% for a 3 mm thickness against 7% for a 25 mm thickness. With a highly compressible material, such as activated sludge, the filter-cake dryness did not change with the application of a shearing action. This behavior may be mainly attributed to the fact that biological sludge dewatering is markedly influenced by a low permeability skin at the cake/medium interface, which is very thin and not perturbed by shear forces, due to the cake thickness. The low rigidity of the solid matter in this particular case may also limit the reorientation of the particles.     

高效脱水的进展

在查阅大量文献资料的基础上 ,分析了国内外高效脱水技术与设备的发展动态 ,分析了今后的发展趋势。     

用于细颗粒分离的水力旋流器的压力特性研究

对用于细颗粒分离的水力旋流器的压力特性 (压力降及压降比 )与流量、分流比、旋数、溢流口和底流口直径及气液比等主要参数之间的关系进行了深入的研究与分析。研究发现 ,水力旋流器内部压力降分别随流量、分流比、旋数及气液比的提高而加大 ,压降比则分别随流量、分流比、旋数的提高而降低。随着溢流口直径的加大 ,水力旋流器的溢流压力降减小 ,而压降比也随之降低 ;随着底流口直径的加大 ,底流压力降减小 ,压降比随之升高。分析可知 ,减少旋流器能耗的有效方法是降低旋数 ,或者减少混合介质中的气液比     

A Mean Phi Model for Pressure Filtration of Fine and Colloidal Suspensions

A working model for engineering analysis of pressure filtration is presented. Based on the filtration characteristics of fine and colloidal suspensions, the process was divided into two stages. A time‐invariant spatially uniform volume fraction of solids approximation is invoked in the growing filter cake stage (stage 1). A time‐dependent spatially uniform volume fraction of solids assumption is made in the cake consolidation stage (stage 2). The two models, named collectively as Mean Phi (M‐P) model, have a common physical basis, seamless continuity between the stages and internal consistency. The M‐P model has only three parameters: terminal or equilibrium volume fraction of solids in the filter cake that is related to its compressive yield stress, critical volume fraction of solids, which joins stage 1 and stage 2, and a permeability factor, which is common to stages 1 and 2. The model is validated with a large number of colloidal suspensions filtered under highly diverse physical‐chemical process conditions. A Pareto profile is identified that relates the timescale of filtration and the extent of dewatering achieved, the two most important performance indices of the process.     

Influence of Electric Field Application with Decreasing One Sided Area of Electrodes on Electro-Osmotic Dewatering

Electro-osmotic dewatering is typically operated under an electric field of direct current condition. In the process of electro-osmotic dewatering, water content in part of the material near the electrode opposite to the drainage surface is locally reduced, resulting in an increase of electrical contact resistance between the electrode and the material being dewatered. Then the efficiency of the electro-osmotic dewatering process is reduced remarkably.

In order to improve the performance of electro-osmotic dewatering, it is supposed that a porous plate-type electrode used generally opposite to the drainage surface may be replaced to several rod-type electrodes, which are inserted into the material with dewatering. Using rod-type electrodes, the area of those electrodes becomes smaller than the plate-type electrode.

From this point of view, electro-osmotic dewatering was experimentally investigated by decreasing one-sided area of electrodes, namely the area of the plate-type electrode opposite to the drainage surface, and the influence of such an electric field application on improvement of the dewatering process is discussed in this article.     

我国细粒煤脱水技术与设备研究现状

搞好细粒煤分选是生产洁净煤的重要途径,选煤厂出厂产品水分的高低直接受细粒煤水分高低的影响。本文就加强细粒煤脱水的重要性进行论述,并介绍了近期研制成功的应用于工业生产的细粒煤脱水技术与设备     

Modeling of Differential Pressure Buildup during Flow through Beds of Fibrous Materials

Modeling of the pressure drop buildup across beds of fibrous materials at strainers is reported. Special attention is drawn to the compressibility of the fibrous filter cake. The influence of the penetration depth of sludge particles to the overall pressure drop in conjunction with the thin‐bed effect has been investigated. Numerical results are compared with pressure drop measurements.     

Effect of Operating Parameters on the Dewatering Performance of Press Filters: A Sensitivity Analysis

To optimize the press filters commonly used to dewater residual sludge, the impact of the operating parameters must be better understood. The objectives of this article are (1) to identify the impact of the operating parameters on press filter performances and (2) to classify the operating parameters regarding their impact on dewatering performances. Experiments were performed with conditioned activated sludge in a tangential filtration cell, and a sensitivity analysis of the process was performed. This study emphasizes that cake thickness and filtration pressure have the most significant impacts on dewatering efficiency. These results suggest a promising outlook for press-filter optimization.     

恒压过滤介质阻力分析

A mathematical model for constant pressure filtration is established. The distribution of hydraulic pressure within the cake and the medium resistance are measured. The medium resistance Rm is calculated from the suppositional filtration time Ore. It is demonstrated that Rm is nearly a constant for a given filter cloth.     

Online Particle Size Measurement in Microgel Particle Suspensions: Principles and Data Analysis

If a gelled system is subjected to shearing or the concentration of reactive components is low, microgel particles are formed. Since labile microgel particles with high water capacities can often be found in food systems, and as they are important for the textural properties, particle size measurement is relevant for fundamental research and control of industrial processes. A chord length measurement system was tested for online particle sizing.     

氧化精矿压滤脱水实践

介绍了一种氧化精矿压滤脱水方法 ,能使氧化精矿压滤脱水水份低 ,产量大 ,效率高。     

SD型静态混合器压力降的特性分析

借助计算流体力学软件FLUENT5/6,对含有3个流道的螺旋式静态混合器在不同的长宽比和雷诺数下的流动特性进行了数值模拟。模拟结果表明,当螺旋片长宽比为4∶1时该混合器压力降与雷诺数的1.715次方成正比;当雷诺数一定时,压力降与混合元件单元数在双对数坐标下成线性分布规律;压力降随着螺旋叶片长宽比的减小而增大;该混合器的压力降与对应结构的SK型静态混合器基本相同,大约是相同直径和管长的光滑空管压力降的10倍。     

液力过滤与液力压密脱水的理论(Ⅱ)

将滤室固定不变的板框或箱式压滤机的操作过程分成滤饼过滤阶段和液力压密脱水阶段两个过程来研究。在滤饼过滤阶段 ,应用表面过滤机理 ,采用传统的鲁思过滤基本方程和平均过滤比阻的理论进行研究。在液力压密脱水阶段 ,应用达西定律建立了液力压密基本微分方程 ,根据研究得出滤饼渗透系数与孔隙率在压密脱水阶段的线性取代关系的结论 ;滤室固定的限制条件和物料平衡条件 ,推导出液力压密的脱水方程式。分析了影响液力压密脱水的时间因素和液力压密速率的各操作参数。建立了完整的液力过滤和压密脱水理论 ,为自动压滤机的设计提供了理论指导     

粉煤灰及生物质对污泥脱水性能的影响试验研究

在自制的压滤装置上,通过添加改性粉煤灰、木屑和不同粒径秸秆,研究不同辅料及其添加量对污泥深度脱水的影响。研究结果表明,改性粉煤灰对污泥脱水效果最好,在添加量为4%时,污泥含水率降为53.6%;木屑效果次之,在添加量为10%时,污泥含水率为58.09%;粒径相对较大的麦秆对污泥脱水促进效果不明显。     

3种被动式微混合器的性能对比及压损分析

通过数值模拟的方法对3种不同结构的被动式微混合器进行了研究,同时对3种被动式微混合器的混合性能进行了对比,并进一步研究了微混合器的压力损失。结果显示,内肋形微混合器在5种速度条件下的混合性能要优于其他两种微混合器,而且随着流量越来越大,其压力损失也越来越大;内肋形微混合器的压力损失最大,Z形微混合器的次之,Y形微混合器的最小。     

原油脱盐脱水技术评述

综述了各种非电脱盐技术方法 ,主要包括离心法、直流电型旋流分离、过滤法、旋流分离、声化学法、磁处理及微波辐射等。同时指出 ,旋流分离技术在原油脱盐脱水领域具有很好的经济效益和广阔的应用前景。