Laboratory Experiments on Electroosmotic Dewatering of Vegetable Sludge and Mine Tailings

ABSTRACT

Vegetable wastes in the food industry are costly lo handle because of their high moisture content. while mill plant tailings in the mining industry contain large quantities of ultralines which are difficult io dewater.This paper describes the results of small scale electmosmotic dewatering (EOD) and combined field dewatering (CFD) measurements with model vegetable sludges and mine tailings.     

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.     

氮化硅粉体水基悬浮液电动特性的研究

通过测量氮化硅粉体在水溶液中的Zeta电位和颗粒大小j研究了不同条件下氮化硅水基悬浮液的电动特性。结果表明,溶液的pH值以及引入的聚合电解质不同均会使氮化硅颗粒表面的荷电状态发生变化,进而导致粉体在水溶液中的分散状况发生改变．在碱性条件下添加适量的阴离子聚电解质有利于氮化硅水基悬浮液的稳定分散。     

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.     

大气电场的几种测量方法

本文介绍了在不同的气象条件下,采用不同的方法对大气电场的测量。     

电场对汽液平衡的影响

利用电场的极化效应对物质分子间力的影响 ,研究了电场对乙醇 水、丙醇 水、醋酸 水体系汽液平衡的影响。结果表明 ,外加电场对这三个体系的汽液平衡均有影响 ,但不能明显改变共沸物系的共沸温度和共沸组成 ,即不能明显使共沸点漂移。电场使体系中介电常数大的组分在汽相中的含量增大 ,介电常数小的组分在汽相中的含量则减小。介电常数相差越大 ,越有利于电场的极化分离     

高压脉冲电场中乳化油最佳破乳电场参数

合理的电场参数是确保高压脉冲电场实现乳化油液高效破乳脱水的重要前提,目前关于电场参数的理论研究鲜有报道。通过建立乳化油液滴在高压脉冲电场中的振动动力学模型,研究液滴振动幅频特性,得到液滴共振频率及共振振幅。在此基础上,根据乳化油系统物性参数,结合液滴最大稳态拉伸变形条件,利用作图法可计算出乳化油最佳破乳电场频率与电场强度的值。实验结果表明,计算得到的最佳破乳电场参数能够实现乳化液滴高效结聚。因此,利用非线性振动动力学确定的乳化油最佳破乳电场参数是合理可靠的。     

电场作用下动态超滤分离鲨软骨粘多糖的研究

研究了电场作用下动态超滤分离鲨软骨粘多糖的操作工艺;考察了不同电场强度下操作压力、温度、进料浓度和流速对膜通量的影响。结果表明,电场可以提高膜通量和膜截留率,强化超滤鲨软骨粘多糖的分离过程。     

Effects of pores on dielectric breakdown of alumina ceramics under AC electric field

The relationship between pores and dielectric breakdown strength of alumina ceramics has been investigated. Alumina specimens with different internal pores in size and quantity were obtained with polyvinyl alcohol (PVA) granules additives being removed after sintering. Pores inside the ceramic samples were characterized by density measurement and micro computed tomography (Micro CT) analysis. We tested the breakdown strength of different alumina sheets under AC electric field, with the same electrodes and voltage loading methods being adopted. The experimental results indicated that the dielectric breakdown strength of alumina specimens decreased with the increment of their thickness. Interestingly, a great deal of large pores influences the breakdown strength significantly. And the breakdown channel passes through the large hole when there is a large hole in the sample. Small pores have little effects on the insulating properties. Further discussion and analysis reveal that the measured results of breakdown strength conform to the Weibull distribution. In addition, the experimental results can be well explained by space charge injection models and electric field simulation.     

Effect of Operating Parameters on the Effectiveness of Electric Field-Enhanced Separations

The purpose of this work is to summarize our latest research results about constant-current electroosmotic dewatering (EOD). The Terzaghi-Voigt combined model is used for the analysis of EOD of various solid-liquid systems by considering the creep deformation of the material. Bentonite clay, KC-flock, zinc oxide, and some of their mixtures are used as experimental materials. It is assumed that the electroosmotic pressure gradient E _pg and modified consolidation coefficient C _e of the materials are constant. The relation between the ratio of creep deformation to total deformation B and the modified consolidation coefficient C _e is determined and compared with previous observations for the case of mechanical expression. The effectiveness of dewatering is described depending on operating parameters such as preconsolidation pressure, material composition, electric current density, and total solid volume per unit cross-sectional area. The model is verified by comparing the calculations with experimental data.     

生物除磷的电场强化作用及其规律研究

本课题通过对比试验对生物除磷的电场强化作用及其规律进行了初步研究,结果表明,在试验条件下(电流密度:i=0．04-0．08mA／cm2),无论那个反应时段(厌氧段、好氧段)施加电场,对提高、稳定生物除磷效率都有积极的作用;对比研究发现,在相同的电流密度下,好氧段电场强化对除磷效果的促进作用更明显,在最佳工况(好氧段强化,i=0．08mA／cm2),电场强化反应器TP平均去除率高达92％,比对照组普通生物反应器高出15％。另外,试验分析了剩余污泥的含磷量,数据显示,电场强化生物反应器剩余污泥含磷率达5．04％(干重),比对照组普通生物反应器高0．68％,进一步表明了电场可强化活性污泥的超量吸磷能力。     

电场增强等离子体作用下甲烷转化动力学研究

Methane conversion was studied with electric field enhanced plasma (EFEP) technique at the atmosphere pressure and low temperature ranging from 323 K to 373 K. The conversion of methane is up to 60%-80%. The kinetics of methane conversion was studied using naicroreactor. The reaction model of power function type was obtained as: r = 90.99exp (-26980/RT)C0226A(mol·m-3·s-1). The global kinetics parameters were calculated by the variable simple-pure shape method. The calculating results are in good agreement with experimental data.     

Dual Electric Field Induced Alignment of Electrospun Nanofibers

A dual‐field method is described to produce aligned fibers by electrospinning. By applying a secondary electric field perpendicular to the primary field, control over the orientation of the fibers on the collector is obtained. The dual‐field approach is used in conjunction with dual electrodes and a rotating collector. Both approaches were used to electrospin poly(lactic acid) fibers under conditions intended to produce fibers with a diameter greater then 400 nm to aid observation by optical microscopy and digital photography. Digital photography was used to visualize a large area of aligned fiber and image analysis software was used to quantify the degree of alignment. Fibers aligned with the aid of a dual field showed better alignment than those from a single electric field under otherwise identical conditions.

     

Multichannel Flow Electrophoresis in an Alternating Electric Field

Abstract

Investigation on the mass transfer behavior of multichannel flow electrophoresis (MFE) has confirmed the existence of concentration polarization in the separation process, which is characterized by a reduction of the relative protein migration flux corresponding to an increase in the protein concentration in the feed. The mobility of bovine serum albumin (BSA) in a gel membrane, as interpreted from its elution curve, was about one-sixth of its mobility in solution as determined by high capillary electrophoresis. This indicates that accumulation of charged protein onto the membrane surface occurs in MFE. An alternating electric field was applied instead of the steady one in MFE. The negative part of the alternating electric field reduced the polarization layer periodically. The effectiveness of this method was demonstrated by an over 40% increase of BSA migration flux at pH 6.9 in an optimized alternating electric field. The separation outputs of BSA and hemoglobin bovine blood conducted in an optimized alternating electric field at pH 6.0 were about 26 and 32% higher than their respective outputs obtained in a steady electric field. Because of its proven efficiency for reducing concentration polarization and its ease of operation, the use of an alternating electric field is a promising application in other membrane separation processes.     

生物除磷的电场强化作用研究及动力学初探

本课题通过对比试验对生物除磷的电场强化作用及其动力学进行了初步研究,结果表明,在试验条件下(电流密度:i=0．04～0．08mA／cm2),无论哪个反应时段(厌氧段、好氧段)施加电场,对提高、稳定生物除磷效率都有积极的作用;且厌氧放磷反应及好氧吸磷反应都近似地符合一级动力学规律,电场可增大厌氧放磷及好氧吸磷速率常数,从而提高、稳定生物除磷效率。     

Drying Kinetics of Apple Tissue Treated by Pulsed Electric Field

The aim of this work was to study the influence of pulsed electric field (PEF) on the drying kinetics of apple tissue. Therefore, mathematical models that are commonly used in the literature were applied to describe the process. PEF treatment of the samples was carried out at an intensity of E = 5–10 kV/cm and 10–50 pulse numbers. Subsequently, the apples were convectively dried at 70°C and air velocity of 2 m/s. Based on electrical conductivity measurement, the cell disintegration index Z _p was computed. Midilli et al.'s(Drying Technology, Vol. 20, pp. 1503–1513, 2001) model was evaluated as the most adequate to describe the moisture transfer in PEF-treated and intact samples. PEF pretreatment induced a reduction in drying time of up to 12% when 10 kV/cm and 50 pulses were applied. For instance, after 60 min of drying, the dimensionless moisture ratio for PEF-treated (10 kV/cm, 50 pulses) samples was 0.18 compared to 0.26 for the untreated apples. The effective moisture diffusivity, calculated on the basis of the Fick's second law, was 1.04 × 10^?9 m/s for intact samples and from 1.09 × 10^?9 to 1.25 × 10^?9 m²/s for PEF-treated samples at 10 pulses at 5 kV/cm and 50 pulses at 10 kV/cm, respectively.     

脉冲电场对Fe-C-P系合金熔体凝固过程的影响研究

在Fe-C-P系合金熔体的凝固过程中加入脉冲电场能有效减轻晶界偏聚,改善凝固组织,同时也引起了元素的迁移和重新分布,C元素与P元素呈现出相似的迁移规律,随着电压的增加,P元素偏析标准偏差从1.67降到1.26,C元素也由1.03降到0.65. 处理后的熔体凝固组织中夹杂物主要分布在中心区域,凝固组织中未观察到含磷夹杂物,存在少量MnS和Al2O3夹杂物.     

电场对水树老化XLPE电缆修复效果的影响

为提高水树老化交联聚乙烯(XLPE)电缆注入式修复效果,研究了在施加不同电场时,水树老化XLPE电缆的注入式修复效果,以获得较好的修复方式。将水树老化后的电缆样本分别在不施加电压、施加直流正极性电压、直流负极性电压以及施加工频交流电压的情况下进行注入式绝缘修复。注入式修复期间,测量4组电缆样本的泄漏电流并对电缆样品切片后进行扫描电子显微镜观测。结果表明,注入式修复时施加电压明显提高了电缆的修复效果,而施加直流正极性电压时,修复液与水反应后的生成物颗粒团聚小,在水树区域分布均匀,注入修复液后4 h水树老化XLPE电缆的泄露电流下降至10μA,修复效果在4组样本中最优。     

Synthesis of Oil-Swelling Material and Evaluation of Its Self-Healing Effect in Cement Paste

This study adopted a synthetic oil-swelling material (OSM) as a novel additive in oil well self-healing cement paste (SHCP) to achieve self-healing effect initiated by oil phase when cracks already formed. The OSM with oil absorption rate of 12.78 g/g in kerosene. The mechanical properties of uniaxial tensile fracture elongation up to 208.8% and tensile fracture toughness up to 25.7 kPa, uniaxial compressive fracture toughness up to 1.956 MPa. The results indicated that permeability of SHCP gradually alleviated due to swelling of OSM, and compressive strength obviously increased under the optimal dosage compared to the blank specimen.