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     

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     

过滤过程的计算

<正> 多种压滤机的滤室容积都是固定的,这类压滤机的操作一般分为前期的过滤阶段和后期的压密阶段。过滤阶段,滤饼各处的空隙率是不同的,越靠近滤布,滤饼空隙率越小,滤饼表面空隙率最大。过滤阶段终了,如果继续向滤室压送悬浮液,则滤饼平均空隙率降低,湿含量减少,这就是压密阶段。     

压滤机过滤压密理论设计方法

<正> 一、前言在设计压滤机或自动板框过滤机时,一般都以经典Ruth过滤公式描述其整个压滤过程的特性。但是,由于Rurh公式只能描述压滤过程中的过滤特性,而不能描述其中的过滤压密特性,所以按Ruth过滤公式设计出来的压滤机,往往达不到生产要求或是不经济的。     

定压压榨压密过程的计算

<正> 前 言 压榨操作所引起的压密过程一般分为两种情况。一种是对浆状原料的压榨,即对过滤期间结束时形成厚度为L=L_1的滤饼进行压密。另一种是对半固体状的湿润饱和原料的压榨,这时不存在过滤期间,从一开始就进入压密过程。在定压过滤时,滤饼内的液压分布实际上保持一定。但在定压压密过程     

《化工装备技术》一九八七年总目录

过 滤馅动板据过滤机设计方程的研究…………王中来j篷榨理论的基础—一压密理论…………苏显儒等!掏瓷过滤器的应用技术……………………………,真空加压过滤器……………………………………新型金属过滤元件研制成功………………………,,J、型全自动过滤机…………………………………定压压榨压密前的定压过滤的计算……苏显儒等新型筛分设备一ZC振动筛分机…………………定压压榨压密过程的计算………………苏显儒等动态旋叶过滤机功率消耗…………………张红兵压榨理论进展………………………………壬中来连续过滤浓缩机…………………     

定压压榨压密前的定压过滤的计算

定压压榨分为定压过滤期间与定压压密期间。本文主要讨论定压压密期间前的定压过滤期间的计算。推导出适合该计算的过滤基本方程式,并应用到定压过滤期间,判定出定压过滤期的终了点。计算过滤期终了时的全部压榨量及过滤比。     

带式压滤机

<正> Societe Lautrette Industries发明了物料连续过滤的一种方法和设备。这种称之为带式压滤机的压滤设备主要由渗透性输送带和传动机构组成。加压机可以由气动式压垫构成。加压机能对输送带上物料施加压刀,使所含液体滤出。该带式压滤机的优点     

一种新型立式全自动压滤机

过滤与分离工序在现代工业中几乎无处不在,相应的过滤设备种类也是各种各样,立式压滤机作为自动化程度比较高的设备,劳动强度低,生产效率高,逐渐被市场所接受。现有的立式压滤机在强腐蚀等领域还存在较大的问题,影响了立式压滤机的进一步推广,一种新型立式压滤机的成功设计将予以解决。     

管式压滤机

英国EEC国际有限公司设计和生产了一种自动管式隔膜压滤机,自1982年起就用于高岭 土的过滤。目前在欧美和亚洲已有许多联合制造厂家生产这种管式压滤机。 这种管式压滤机主要由外壳、弹性橡胶隔膜和中心滤管所组成。滤管是一根其上覆盖有金属网垫和滤布的直立有孔钢管。此外,整机还附设有加压系统和自控装置。 管式压滤机的过滤作业可分为给料、压滤和卸料三个阶段,其工作原理见下图所示。管式压滤机开始工作时,液压系统处于“负压”状态,使橡胶隔膜紧贴于过滤机外壳的内壁上。与此同时,滤管上升,在隔膜与滤管间形成了一个闭合的管状空间,矿浆给入此空间中。接着液压系统开始加压,压液充盈于隔膜与外壳内壁之间。液     

Modelling the electro-osmotically enhanced pressure dewatering of activated sludge

The mechanical dewatering of biological materials, such as activated sludge, is troublesome due to their high compressibility. The dewatering can be improved drastically by the use of electro-osmosis, a technique in which a direct current electric field is applied to the filter cake, inducing an electro-kinetic displacement of the liquid phase. In this article, a model is presented which describes this process for a one-dimensional, one-sided filter press. The model starts from two existing models, each describing a part of the process [Iwata, M., Igami, H., Murase, T., 1991. Analysis of electroosmotic dewatering. Journal of Chemical Engineering of Japan 24(1), 45-50; Sørensen, P.B., Moldrup, P., Hansem, J.A., 1996. Filtration and expression of compressible cakes. Chemical Engineering Science 51(6), 967-979]. A robust solution scheme for the basic flux and continuity equations is used to describe filtration and expression. Regarding the electro-osmosis, an adapted form of the Darcy equation, expressing electro-osmotic induced flow as well as pressure induced flow, is integrated into the former solution scheme. This permits the simulation of the overall process using a single model. Validation of the model revealed that the experimental piston height during dewatering can be described accurately provided that temperature effects are taken into account.     

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.     

High-pressure filtration—a chance for the downstream processing of biological dispersions

High-pressure filtration is a common practice in solid-liquid separation. A pressure up to 150 bar is used first for short-time drainage and then to press the filter cake with the help of an elastomer diaphragm.After the principal investigation of this concept and measurements to separate biological dispersions, its use in several processes is proposed. For suspensions of cells a filter cake with a high proportion of dry residue can be obtained within a very short time. The optimal regulation of this process on an industrial scale can be obtained by evaluation of laboratory experiments. For separation procedures with biomass and fermentation liquid the high pressure can be used to shorten the filtration time. Bacterial dispersions may be separated effectively with a cross-flow filtration apparatus which is to be developed for work at high pressure.The filtration experiments were performed on bakers' yeast (leaven) and Escherichia coli (E. coli) bacteria as model substances with a laboratory filter press apparatus. The filtration velocity and the specific filtration resistance are reported. Furthermore, the processing costs in relation to the proportion of dry residue were calculated as a function of pressure. The minimum cost corresponds to the economical operation range. Though this process is unjustifiably considered as relatively expensive, it is possible that, worked at its best, it will be able to compete with other mechanical separation processes.     

热压过滤脱水技术

根据过滤理论 ,对提高过滤速率 ,降低产品水分的三种技术途径进行了比较 ;重点论述了热压过滤的机理、效果 ;介绍了热压过滤工业应用装置的结构和系统构成 ,认为热压过滤是目前降低细料矿物产品水分最有效的技术途径 ;该热压过滤装置是实用性强 ,投资省的设施 ,适用于有关现场解决细粒矿物脱水的难题。     

Effects of pore size, suspension concentration, and pre-sedimentation on the measurement of filter medium resistance in cake filtration

Theoretical and experimental study was conducted on the factors influencing the measurement of filter medium resistance by Ruth’s equation. It was determined that a filter medium having small pore size does not always give high filter medium resistance. The appropriate pore size of filter medium for filtration was analysed. The resistances of filter media measured with thick suspensions by Ruth’s equation have negative values. This phenomenon can be analyzed as the effect of sedimentation during the long filtration time due to thick suspension. When sedimentation occurs before the start of filtration, the filter medium resistance measured by Ruth’s equation gives a large value. It was determined that the result of the filtration of sediment was included in the filter medium resistance. A new method for measuring filter medium resistance by the filtration of the sediment is proposed. This method excludes the effects of suspension concentration and pre-sedimentation.     

A Study for Development of Real-Scale Thermal Filter Press Dewatering (TFPD)

Real-scale thermal filter press dewatering equipment (plate size: 630 mm × 630 mm) was installed and operated at a waterworks for one year in an attempt to achieve sludge reduction. During the period, the dewaterability was evaluated according to the seasonal sludge properties in order to compare the dewaterability of thermal dewatering and mechanical dewatering, as well as to determine the economics of thermal dewatering. According to the results, the winter season sludge showed a 36% decrease in water content and a two-thirds reduction in dewatering velocity compared to the summertime sludge. In addition, the dewatered cakes of the thermal filter press dewatering equipment showed a lower specific cake resistance and water content in the dewatered cakes than the mechanical filter press dewatering equipment, indicating superior dewaterability. This was attributed to the easier removal of the filtrate remaining in the capillary tubes due to thermal dewatering. The energy consumption for thermal dewatering was 300 kJ/dry solids (DS) kg. A comparison of the sludge dryers indicated that it is possible to produce dewatered cakes that consume less energy and can be recycled. According to the performance evaluation results, the real-scale thermal filter press dewatering equipment had high adaptability to the changes in seasonal sludge, showing excellent dewaterability compared to the mechanical filter press dewatering equipment, and was economical due to the lower energy consumption.     

MODELLING OF HEAT TRANSFER IN HOT PRESSING AND IMPULSE DRYING OF PAPER

A modelling and simulation study regarding the heat transfer in hot pressing as well as in impulse drying of paper has been performed. The study is focused on modelling the heat transfer from a hot surface to a moist paper sheet and the heat transfer inside the paper sheet. The model is based on solving the equation for unsteady heat transfer by conduction. The model was compared with experimental data from a heated laboratory platen press and data from the experimental paper machine EuroFEX at the Swedish Pulp and Paper Research Institute (STFI) in Stockholm. The results in this study showed that a rather simple heat transfer model could be used to simulate the heat transfer in cases in which the temperature was moderate and the applied pressure did not exceed 0.5 MPa. It was also concluded that a paper could be regarded as a semi-infinite body for basis weights above 110 g/m², considering the assumptions used in the model. It was also shown that a laboratory press could simulate heat transfer in hot pressing and impulse drying with a high degree of accuracy.     

Scale-up studies of the electrolytic reduction of oxalic to glyoxylic acid

The work examines a possible process for the electrolytic reduction of oxalic acid to glyoxylic acid. The reaction is investigated in filter press type cells varying from small bench scale to pilot plant size and it is shown that the product can be produced with current efficiencies better than 70% and chemical yields better than 90%. It is demonstrated that the cell product containing 8–10 wt% of glyoxylic acid can be concentrated to the commercial specification of a 50 wt% aqueous solution.     

磷酸萃取料浆应用立式压滤机脱水的试验研究

对磷酸萃取料浆用立式压滤机脱水、洗涤进行了试验研究,对试验结果进行了分析,认为立式压滤机可以替代其它脱水设备对磷酸萃取料浆进行脱水处理。