Hydrodynamic parameters from the Michaels and Bolger method

For different initial heights and solids concentration of flocculated calcium carbonate suspensions in the compression range, the variations of the subsidence rates are discussed in accordance with the Michaels and Bolger method. A mathematical model based on the consolidation theory has been applied to generalize the Michaels and Bolger method, and to discuss the relationships between the permeability, the effective pressure and the solids concentration. In accordance with this model and the experimental results, it is deduced that the relationship between the effective pressure and the solids concentration differs considerably from that obtained by other methods, whereas the values of permeability for different solids concentration are close to those deduced by different methods.     

Compression and permeability relationships in high water content clays

Storing contaminant soils, such as dredge materials, sludge and mine tailings, and reclaiming contaminant soil storage areas back into the economy has arisen as an important economical and environmental problem in today's world. The scientific studies in the last thirty years have revealed critical new information regarding the deformation behavior of high water content soils.In this article relationships between material properties used in constitutive models for self-weight and/or surcharge loaded high water content (slurry) clays and their index properties are investigated. For this purpose three different kinds of clays in a slurry consistency are subjected to seepage induced consolidation in an experimental setup. Information obtained from these experiments, together with information already in literature, is used to investigate the relationships between the index properties and the consolidation constitutive model parameters. The relationships obtained from the experiments are then utilized to predict the self-weight consolidation of Halic (Golden Horn) dredge materials. These predictions are then compared with the results of numerical analysis and found to be in good agreement.     

Kinetics of droplets’ sedimentation in a continuous gravity settler

Extraction experiments of phosphoric and chloric acids from isoamyl alcohol by water were conducted in an impinging-stream reactor with thin films (Berman & Tamir (AIChE J. 46 (2000) 769; Can. J. Chem. Eng. 79 (2001) 305)). Phase separation was achieved in a regular gravity settler shown in Fig. 1.Extraction efficiency of about 100% was achieved, and mass transfer coefficients were higher by comparison to regular devices by a factor of 100-200. The limiting zone in the settler was the “sedimentation zone”, typical to the present chemical system as well as similar ones.A model was established for the “sedimentation zone”. It is based on known theories of droplets’ motion in a liquid, on a special method which was developed here to determine the fractions of the dispersion phase moving upwards and downwards, as well as on a new approach to determine the droplets diameters. Experimental results substantiated the validity of the suggested model.     

Local solidosity of microcrystalline cellulose during dead-end filtration and sedimentation

Solid–liquid separation by filtration and sedimentation are important operations used in a wide range of industries. One important characteristic of both the filtration and sedimentation processes is the solidosity of the filter cake/sediment that is formed, affecting the efficiency and design of the separation. In this study local solidosity was investigated using a γ-attenuation method during both filtration and sedimentation experiments for microcrystalline cellulose, a highly crystalline cellulose with particles of about 2–80 μm in diameter. Constitutive relationships for the solidosity were investigated using both filtration (i.e. cake build-up and expression) and sedimentation data for experiments at different pH and suspension concentrations. The sedimentation behaviour under these different conditions was also investigated. It was found that a three parameter empirical model could be used to describe the constitutive relationship between local solidosity and local solid compressible pressure for the sediment formed and the filter cake after both cake build-up and expression. This correlation worked well for the material investigated even at low solid compressible pressures.     

优化盐泥压滤工艺 降低氯碱盐泥含盐量

通过采取调整泥水比、用蒸汽预热洗泥水、完善操作规程、加强管理等措施,优化盐泥压滤工艺,盐泥含盐质量浓度由原来的60g／L下降到15g／L左右,取得了较好的环境和经济效益。     

How to elutriate particles according to their density

It is well known that particles settle at a velocity dependent on both their size and density. This dependence makes it difficult to efficiently concentrate valuable minerals of a given density, unless the density range between the valuable and gangue particles is sufficient to overcome the segregation arising from the particle size range. Here we reveal a method for suppressing the effects of particle size so that particles can be routinely elutriated on the basis of their density. The particles are suspended by fluidizing with water, and then conveyed into channels inclined at 70° to the horizontal, closely spaced with a gap of 1.77 mm. Through the application of these conditions, a fortuitous coincidence arises. Firstly, a high shear rate is produced, sufficient to achieve inertial lift and hence promote the transport of the particles along the inclined surfaces, free of significant lubrication and mechanical friction forces. Secondly, the flow through the channels is laminar, with an almost linear variation in the local velocity with distance from the inclined surface. Hence a given particle resident near an inclined surface experiences a local elutriation velocity proportional to its diameter. These conditions suppress particle size segregation thus allowing the imposed hydraulic velocity to convey particles on the basis of their density.     

Compression-dependent permeability measurement for random soft porous media and its implications to lift generation

In the past decade, foundations have been laid for understanding the lift generation in a soft porous medium under rapid compaction (Feng and Weinbaum, 2000. Journal of Fluid Mechanics 422, 282–317; Wu et al., 2005b. Journal of Fluid Mechanics 542, 281–304; Wu et al., 2004a. Physical Review Letters 93(19), 194501; Barabadi et al., 2009. Journal of Heat Transfer 131(10), 101006-1–101006-12; Al-Chidiac et al., 2009. Journal of Porous Media 12(11), 1019–1035). One of the key parameters that affects the lift generation is the variation of the Darcy permeability as a function of compression. This critical problem is investigated in the current study using a novel experimental setup, namely a permeameter. Three different, soft, synthetic, fibrous, porous materials were chosen for the study. Their microstructures were characterized using a scanning electron microscope and a stereomicroscope. Their porosities were precisely measured using a water displacement method. By carefully controlling the air flow through the materials contained in a long Plexiglas tube of the permeameter, one obtained consistent results for the Darcy permeability of the tested material as a function of its porosity. Fluffing the porous materials caused disturbance of their microstructures thus variations in the permeability, especially in the high porosity range. The experimental data was curve-fitted and compared to established expressions. It showed that the Nogai Expression (Nogai and Ihara, 1978. Journal of Textile Machinery Society of Japan 31(12), T166–T170) provided the best fit for the change of permeability as a function of compression for the fibrous materials studied herein. The Carman–Kozeny equation, however, is only applicable for one of the fibrous materials. This finding is consistent with the theoretical predictions by Barabadi et al. (2009).     

液力过滤与液力压密脱水的理论(一)

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     

絮凝技术在化工污水处理中的应用

对不同种类的絮凝剂在不同试验条件下得到的絮凝现象进行观察,絮凝后的污水通过带式压榨过滤机过滤,根据过滤前后污泥性质的变化选择出最佳的絮凝剂及使用条件。     

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     

次毫米过滤组件分区高含量污泥试验研究

采用次毫米过滤(SMF)组件实现高含量污泥(MLSS)分区(A区和B区),为膜生物反应器(B区)的稳定高效运行提供适宜的污泥质量浓度(5.0～10.0 g.L-1)。研究了回流体积比≥2.0条件下SMF组件(孔径0.47 mm)分离高含量污泥的运行特征及分区效果,对比分析了两区微生物实测与理论含量的差异,并考察了SMF组件耦合A区对营养物的去除效果。结果表明,在分离高含量污泥时,目标B区的污泥的质量浓度为2.0～10.0 g.L-1,对膜生物反应器是适用的;对应A区的污泥的质量浓度在15.5～33.5 g.L-1。SMF组件滤出液MLSS的质量浓度在1.4～4.2g.L-1,平均通量可达192 L.m-.2h-1。此外,SMF组件耦合A区对COD的去除率在82%以上。     

THE INFLUENCE OF COMPRESSION WOOD ON THE DRYING CURVES OF PINUS RADIATA DRIED IN DEHUMIDIFIER CONDITIONS

Measurements of drying rate of Pinus radiata at 55°C and 30% RH are presented. The data, which has been used to establish empirical models for P. radiata under dehumidifier drying conditions, was obtained in four drying runs in a drying tunnel, each yielding detailed drying curves for twelve sample sapwood boards of size 350 × 100 × 50 mm. Compression wood was found to have a significant effect on the drying rate curve, giving lower drying rates at 40-100% MC. This effect is interpreted through the use of a numerical multiple-mechanism two-zone model and quantified by using best-fit diffusion parameters from an isothermal diffusion model. A positive correlation was discovered between the moisture diffusion coefficient and initial moisture content, a strong indicator for the presence of compression wood. In the two-zone model, the compression wood effect was replicated by using a tenfold decrease in permeability to liquid flow. Attributes of compression wood that could cause reduced permeability include an increased proportion of latewood, narrower lumen, and a scarcity of bordered pits on the radial walls of longitudinal tracheids.     

高效固液分离设备的设计和试验

简介一种新型高效固液分离设备的构造、原理、设计、特点,探讨了设备试验过程中的现象,提出了设备的工艺设计参数。     

THE INFLUENCE OF COMPRESSION WOOD ON THE DRYING CURVES OF PINUS RADIATA DRIED IN DEHUMIDIFIER CONDITIONS

ABSTRACT

Measurements of drying rate of Pinus radiata at 55°C and 30% RH are presented. The data, which has been used to establish empirical models for P. radiata under dehumidifier drying conditions, was obtained in four drying runs in a drying tunnel, each yielding detailed drying curves for twelve sample sapwood boards of size 350 × 100 × 50 mm. Compression wood was found to have a significant effect on the drying rate curve, giving lower drying rates at 40–100% MC. This effect is interpreted through the use of a numerical multiple-mechanism two-zone model and quantified by using best-fit diffusion parameters from an isothermal diffusion model. A positive correlation was discovered between the moisture diffusion coefficient and initial moisture content, a strong indicator for the presence of compression wood. In the two-zone model, the compression wood effect was replicated by using a tenfold decrease in permeability to liquid flow. Attributes of compression wood that could cause reduced permeability include an increased proportion of latewood, narrower lumen, and a scarcity of bordered pits on the radial walls of longitudinal tracheids.     

Suspension concentration profiles during rapid gravity filter backwashing

Rapid gravity, granular media filters are widely used in the water and wastewater treatment industries. Regular backwashing to clean the filters is a vital part of their efficient operation. Experimental data on the development of suspension concentration profiles through laboratory scale filter beds during the backwash process were obtained. Previous attempts to obtain and record backwash profiles of this type have been unsuccessful due to the limited range of existing turbidimeters. The results have been used to validate a new model developed by the authors.     

CFD技术在膜过滤过程中的应用

计算流体动力学(Computational Fluid Dynamics,CFD)模拟应用于膜过滤过程是近年新发展起来的一种膜过滤研究方法.综述了CFD模拟在膜过滤过程中的应用,从膜组件过滤特性和反应容器水力特性2个角度概述了CFD模拟膜内部浓差极化、质量传递系数等流态特性,膜面压力、渗透速率等流体特性参数,膜组件优化和反应器内流场分布,为膜过滤过程的评价提供了理论依据,对于实际应用具有极其重要的意义.     

鄱阳湖国家湿地公园旅游综合服务区供水工程研究

本文为东鄱阳湖南岸半岛规划区的供水工程研究,经过水量预测,水厂建设规模近期5000m^3／d,远期10000m^3／d。水源为鄱阳湖内珠湖水,经过工艺比选,选择网格反应斜管沉淀、无阀滤池的净水工艺。     

PAC与铁盐对污泥深度脱水性能的对比研究

在工业废水和生活污水的处理过程中,会产生大量的污泥。污泥中水分含量达到95%~99%,只要将其中的水分去除.就会大大缩小污泥的体积,以便于进一步处理。文章还通过试验从污泥比阻和泥饼含水率两个方面比较四种加药方案(PAC、PFC、FC和PFS)的脱水效果,四种加药方案各有优点。FC、PFC的脱水效果最佳,在投药量为干污泥的21%以上时,泥饼含水率可降至60%以下;PFS和PAC的效果次之。     

Experimental study of the hydro-mechanical behaviour of the Callovo-Oxfordian argillite

Various laboratory experiments were carried out in the framework of the MODEX-REP project on the Callovo-Oxfordian argillite core samples taken from the Meuse/Haute-Marne Underground Research Laboratory (MHM-URL) in Eastern France to provide basic data for modelling the hydro-mechanical response of the argillite to shaft sinking. The short-term mechanical behaviour of the argillite was investigated by means of uniaxial and triaxial compression tests, whereas the long-term behaviour was studied by uniaxial creep and relaxation tests. Some influence factors such as material anisotropy, scale effect, water content and sample origin were examined. Permeability of the argillite was determined on wet and dry specimens parallel and perpendicular to the bedding plane by using gas under different confining pressures. With regard to the short-term mechanical behaviour, scale and anisotropy effects were observed. The compressive strength and the failure strain of the air-dried specimens are about two times higher than those of the saturated ones. No lower creep limit, no significant scale effect and no significant anisotropy effect on the pure creep behaviour for the argillite were found. The long-term mechanical behaviour of the investigated region of the argillaceous formation is relatively homogeneous. The gas permeability parallel to the bedding plane is about one order of magnitude higher than that perpendicular to the bedding and decreases with increasing confining pressure and water content.