离心过滤中滤饼含液量影响因素的研究

本文对离心过滤中影响滤饼含液量的主要因素进行分析。选择细粒级的五种物料，在三足式过滤离心机上做脱液实验，获得的脱水和动力学试验数据，经因次分析，计算机处理，得到实验条件下滤饼含液量Ｗｔ的准数方程：研究结果表明：影响滤饼含液量的因素，首先是物料的物理性质：固体密度ρｓ，颗粒表面积体积平均粒径ｄｓｖ和悬浮液粘度μｓｕｓｐ；其次是操作参数：转鼓角速度ω，脱液时间ｔ和滤饼厚度ｈ。实验条件：Ｆｒ＝１０４８～１５１０，ｄｓｖ＝１．２９～２４．８μｍ，μｓｕｓｐ＝１～１０ｍＰａ·ｓ     

Newtonian and Non‐Newtonian Low Re Number Flow Through Bead Packings

The results of measurements of velocity distributions of Newtonian and non‐Newtonian fluids flowing through porous media are described in this contribution. The porous matrix was modeled by glass beads of different diameters forming a random bead packing confined by a circular tube. These packings were passed through by aqueous solutions of glucose and xanthane gum. Nuclear magnetic resonance (NMR) methods were applied to investigate the flow field in the packing. Spatially resolved and integral displacement distribution measurements were reported.     

颗粒沉积量对细颗粒层清灰力和清灰效率的影响

采用中径3.31 mm的细颗粒在PPS普通滤料和涤纶覆膜滤料表面形成不同沉积量的颗粒层,用缓慢增加反吹气流和低压脉冲清灰的方法进行清灰测试. 随着颗粒层沉积量增加,颗粒层低压脉冲清灰的效率均提高,缓慢反吹的清灰力也呈减小趋势. 涤纶覆膜滤料表面颗粒层沉积量从200 g/m2增长到401 g/m2时,平均清灰应力从350 N/m2降到100 N/m2,比PPS滤料低90 N/m2以上. PPS滤料上低压脉冲清灰效率随颗粒层沉积量的增加线性增加,涤纶覆膜滤料上颗粒层沉积量超过200 g/m2时非线性快速增加,缓慢反吹产生的颗粒层碎片均随着颗粒层沉积量增加而增大.     

Energy Dissipation Rates of Newtonian and Non‐Newtonian Fluids in a Stirred Vessel

Energy dissipation rates of water and glycerol as Newtonian fluids and carboxyl methyl carbonate solution as non‐Newtonian fluid in a stirred vessel are investigated by 2D particle image velocimetry and compared. Mean velocity profiles reflect the Reynolds (Re) number similarity of two flow fields with different rheological properties, but the root mean square velocity profiles differ in rheology at the same Re‐number. Energy dissipation rates are estimated by direct calculation of fluctuating velocity gradients. The varying energy dissipation rates of Newtonian and non‐Newtonian fluids result from the difference in fluid rheology and apparent viscosity distribution which decides largely the flow pattern, circulation intensity, and rate of turbulence generation.     

Bubble Volume and Aspect Ratio Generated in Non‐Newtonian Fluids

Bubble formation from an orifice submerged in quiescent polyacrylamide aqueous solution was investigated numerically with a sharp‐interface coupled level‐set/volume‐of‐fluid method based on the rheological characteristics of the fluid. In both non‐Newtonian fluids and Newtonian fluids, the numerical approach was able to capture accurately the deformation of the bubble surface, validated by comparison with experimental results. The effects of orifice diameter, solution mass concentration, and gas flow rate on bubble volume and aspect ratio were evaluated. Both the instantaneous and detached volume decrease with the orifice diameter but increase with mass concentration and gas flow rate. The aspect ratio at the departing point tends to rise with the orifice diameter and mass concentration and falls with the gas flow rate.     

Predicting Power for a Scaled‐up Non‐Newtonian Biomass Slurry

High‐solids biomass slurries exhibit non‐Newtonian behavior with a yield stress and require high power input for mixing. The goals were to determine the effect of scale and geometry on power number P₀, and estimate the power for mixing a pretreated biomass slurry in a 3.8 million L hydrolysis reactor of conventional design. A lab‐scale computational fluid dynamics model was validated against experimental data and then scaled up. A pitched‐blade turbine and A310 hydrofoil were tested for various geometric arrangements. Flow was transitional; laminar and turbulence models resulted in equivalent P₀ which increased with scale. The ratio of impeller diameter to tank diameter affected P₀ for both impellers, but impeller clearance to tank diameter affected P₀ only for the A310. At least 2 MW is required to operate at this scale.     

Characterization of Bubble Shapes in Non‐Newtonian Fluids by Parametric Equations

Based on experiments with single air bubbles rising in stagnant non‐Newtonian fluids, an innovative model containing the aspect ratio (E) and two parameters (α, β) was proposed and proved to be capable of characterizing the bubble shape from spherical/ellipsoidal to prolate/oblate‐tear with good accuracy. Several impacts on bubble deformation were investigated, involving the rheological properties of the fluids and different forces exerted on the bubble, which were quantified by multiple dimensionless numbers (e.g., Reynolds, Eötvös, and Deborah number). Within a wide range, the empirical correlations were obtained for parameter β, and between α and β. Together with the shape model, a complete system was set up for bubble shape characterization and prediction that will provide new ideas for future studies on bubble hydrodynamics.     

Empirical Modelling of Cake Washing in a Pressure Filter

The focus of this article is on empirical modelling of filter cake washing. The filtration experiments introduced in this paper were conducted by using a pilot-scale (0.1 m²) filter press according to the basic principles of factorial designs. Five different variables of the filtration, pressing, cake washing, and air drying stages were considered in the tests and the examined product characteristics were the overall capacity of the filter and the purity of the cake. The results obtained from the tests were used for creating different kinds of regression models for explaining the influence of the studied variables on the success of the cake washing process. The goal of the modelling strategy for the cake washing was to determine the simplest empirical models and compare these with theoretical equations complemented with linear terms. It was found that the empirical equation could model the results more accurately than the theory-based equations could.     

Operating window of solution casting. II. Non‐Newtonian fluids

The operating windows of the solution casting of two polymeric liquids were evaluated experimentally. The experimental setup and procedure were the same as used previously for the casting of Newtonian fluids (Journal of Applied Polymer Science 2013, 129, 507–516). Aqueous carboxymethylcellulose/glycerol solutions exhibited pure shear‐thinning behavior at low polymer concentrations but became viscoelastic at high polymer concentrations, whereas polyacrylamide/glycerol solutions showed viscoelastic behavior over a wide range of concentrations. The shear‐thinning behavior, in conjunction with a low level of elasticity, of the casting solution was found to be useful in expanding the stable operating windows. However, an opposite effect on the operating windows was found for highly elastic solutions. The non‐Newtonian effect on the maximum stable casting speed was prominent only when the capillary number exceeded unity. Defects outside of the operating window were mostly similar to those observed in Newtonian solution casting. For highly concentrated solutions, a new rough surface defect was observed. This defect could be attributed to polymer chain entanglement, alignment, or breakup. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41411.     

Compression,Permeation and Flow Behavior of Wet Nanoparticle Cakes,in situ Tested with a Press‐Shear Cell

A new test apparatus for in situ simulation of the expression operation and rheological testing of compressed cake was developed to combine the compression‐permeability cell with a high‐performance ring shear tester. The yield loci for water‐saturated titania (d_S = 200 nm) are measured. These flow parameters can be used to determine in situ the shear strength and compressive strength of a consolidated cake after the pressure filtration steps. The permeability of the compressed cake is characterized by the conventional filter cake resistance versus particle pressure and, for comparison, by an averaged pore size.     

成饼过滤中过滤介质阻力与堵塞研究的进展

过滤介质是过滤作业的基本部件,由于在过程中不断地被堵塞,介质阻力不断增加,过滤性能逐渐下降,以致于不能再继续使用。因此研究其被堵塞的机理和降低、减少堵塞的措施就成为改善过滤作业的重要课题。综合了26篇有关文献,介绍了成饼过滤介质堵塞的机理、被堵塞过滤介质阻力的大小、影响过滤介质堵塞的主要因素等几方面的近期研究进展。     

立式压滤机在4A沸石分离工序上的试验

利用立式自动压滤机对4A沸石晶化料浆和合格料浆进行了一系列分离洗涤和风干试验,试验结果表明,该设备的洗涤效果不明显,不能用该设备对4A沸石晶化滤饼进行直接洗涤;但是其滤饼水分可以降到15%以下,故可以用在晶化料浆和合格料浆的分离与风干工序上,能大大降低搅洗工序的洗涤水耗和烘干工序的能耗。     

变腔滤片在桃山选煤厂的应用

桃山选煤厂针对过滤机的使用效果差，脱饼率低的现象，推广应用了“变腔滤片”，使脱饼率达95％以上，不需要吹风，滤网使用寿命长，节约电能，改善了工作环境等，它的推广应用对选煤厂综合效益具有重要意义。     

Measurements of Growth Rate of Filter Cake in Vertical Single-Pass Ultrafiltration Using Hollow Fiber Membrane Module

Vertical ultrafiltration experiments of silica colloid and bovine serum albumin solution were conducted in the single-pass mode by using a hollow fiber membrane module and beneficial in measuring the time evolution of the growth rate of the filter cake during filtration. The extremely small mass flux of the concentrate enabled us to highly concentrate the feed solution on the principle of vertical ultrafiltration in which the filter cake formed on the membrane surface is exfoliated continuously. Both growth and re-entrainment rates of the filter cake formed in vertical ultrafiltration were evaluated from the experimental data of the filtration rate and the mass fraction ratio of the concentrate on the basis of the mass balance within the hollow fiber membrane module. As a consequence, it was found that the re-entrainment rate of the filter cake increased almost linearly with the filtration time in the initial period of filtration and then tended to rapidly approach a constant value. The filter cake stopped growing under this dynamically balanced condition. The variations of the average specific resistance of the filter cake with time were also determined from the time evolutions of both the filtration rate and the growth rate of the filter cake.     

Pressure Drop Models for Gas/Non‐Newtonian Power‐Law Fluids Flow in Horizontal Pipes

Models commonly used in literature are evaluated versus 696 data points to predict the pressure drop of gas/non‐Newtonian power‐law fluids flow in horizontal pipes. Suitable models are recommended. A new correlation is developed by ignoring the pressure drop across the gas slug and adopting the liquid slug holdup of gas/non‐Newtonian fluid flow into the homogeneous model. The theoretical curves can capture the test data trends and the overall agreement of predicted values with experimental data is sufficient to be practically applied in industry.     

Predicting the Viscosity of Non‐Newtonian Water‐in‐Oil Emulsions Based on the Lederer Model

The accurate prediction of the viscosity of emulsions is highly important for oil well exploitation. Commonly used models for predicting the viscosity of water‐in‐oil (W/O) emulsions composed by two or three factors cannot always fit well the viscosity of W/O emulsions, especially in the case of non‐Newtonian W/O emulsions. An innovative and comprehensive method for predicting the viscosity of such emulsions was developed based on the Lederer, Arrhenius, and Einstein models, using experimental data. Compared with the commonly applied W/O emulsion viscosity models, the proposed method considers more factors, including temperature, volume fraction of water, shear rate, and viscosity of the continuous (oil) and dispersed phase (water). Numerous published data points were collected from the literature to verify the accuracy and reliability of the method. The calculation results prove the high accuracy of the model.