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.     

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。     

One‐Dimensional Modeling and Simulation of Bubble Column Reactors

Reactor models that feature a practical way to design bubble columns on the semi‐industrial or even industrial scale have been published only rarely in the usual scientific literature. Creating a one‐dimensional model in the equation‐oriented simulation software ASPEN Custom Modeler? (ACM), one can reach a compromise between model precision and modeling – i.e. computational power – based on correlations selected specifically for the application in question. The model quantitatively describes, with sufficient accuracy, the processes in a bubble column reactor. The paper discusses investigations for designing a pilot plant reactor for hydrogenating 2‐ethylhexanal as an example of its application. Geometry and operating conditions were optimized, and the results are shown in the form of spatially resolved reaction and temperature profiles.     

等效模拟理论与容器试压等效模拟分析

本文介绍了等效模拟理论,提出了危险度概念,建立了容器试压等效模拟准则,揭示了温度修正系数[σ]/[σ]_2的含义。     

DEWATERING OF WASTE ACTIVATED SLUDGE VIA CENTRIFUGAL FIELD

ABSTRACT

While conducting centrifugal dewatering tests on waste activated sludge, this work considered how the rotational speed and the application of cationic polyelectrolyte flocculation affected the sludge. Increased rotational speed and/or conditioning the sludge to a charge neutralization point could enhance dewatering efficiency. A model was proposed to estimate the disruption energy exerted on the sludge body using centrifugation. Experimental results indicate that the disruption energy level provided by the centrifuge increases with rotational speed and decreasing water content in the filter cake. Moreover, polyelectrolyte flocculation may significantly reduce the disruption energy level of the water from sludge particles and the residual water contents at the end of the test.     

恩德炉灰水处理系统技术研究

通过对除尘灰水处理系统分析,选择高效浓缩压滤脱水的技术方案,解决了污染问题。     

DEWATERING OF WASTE ACTIVATED SLUDGE VIA CENTRIFUGAL FIELD

While conducting centrifugal dewatering tests on waste activated sludge, this work considered how the rotational speed and the application of cationic polyelectrolyte flocculation affected the sludge. Increased rotational speed and/or conditioning the sludge to a charge neutralization point could enhance dewatering efficiency. A model was proposed to estimate the disruption energy exerted on the sludge body using centrifugation. Experimental results indicate that the disruption energy level provided by the centrifuge increases with rotational speed and decreasing water content in the filter cake. Moreover, polyelectrolyte flocculation may significantly reduce the disruption energy level of the water from sludge particles and the residual water contents at the end of the test.     

Performance Enhancement by Unsteady‐State Reactor Operation: Theoretical Analysis for Two‐Sites Kinetic Model

Theoretical analysis of the reactor performance under unsteady‐state conditions was carried out. The reactions are described by two kinetic models, which involve the participation in catalytic reaction of two types of active sites. The kinetic model I assumes the blocking of one of the active sites by a reactant, and the kinetic model II suggests a transformation of active sites of one type into another under the influence of the reaction temperature. The unsteady‐state conditions on the catalyst surface are supposed to be created (i) by forced oscillations of temperature and concentration in the reactor inlet (periodic operation of reactor) and (ii) by catalyst circulation between two reactors in a dual‐reactor system (spatial regulation). The influence of various parameters like concentration of reactant, cycle split, length of period of forced oscillations, temperatures and the ratio of catalyst volumes in the dual‐reactor was investigated with respect to the yield of the desired product. It is shown that for both cases of unsteady‐state conditions (periodic reactor operation as well as in a dual‐reactor system), a mean reaction rate predicted by the kinetic model I was up to two times higher than the steady‐state value. The kinetic model II shows a 20 % increase of the selectivity towards the desired product.     

CFD investigation of the pipe transport of coarse solids in laminar power law fluids

A numerical parametric study of the laminar pipe transport of coarse particles in non-Newtonian carrier fluids of the power law type has been conducted using an Eulerian-Eulerian computational fluid dynamics (CFD) model. The predicted flow fields have been successfully validated by experimental measurements of particle velocity profiles obtained using a positron emission particle tracking technique, whilst solid-liquid pressure drop has been validated using relevant correlations gleaned from the literature. The study is concerned with nearly-neutrally buoyant particles flowing in a horizontal or vertical pipe. The effects of various parameters on the flow properties of such mixtures have been investigated over a wide range of conditions. The variables studied are: particle diameter (2-9 mm), mean solids concentration (5-40% v/v), mean mixture velocity (25-125 mm s⁻¹), and rheological properties of the carrier fluid (k=0.15-20 Pa sⁿ; n=0.6-0.9). A few additional runs have been conducted for shear thickening fluids, i.e. n>1. Whilst the effects of varying the power law parameters and the mixture flowrate for shear thinning fluids are relatively small over the range of values considered, particle size and solids concentration have a significant bearing on the flow regime, the uniformity of the normalised particle radial distribution and of the normalised velocity profiles of both phases, and the magnitude of the solid-liquid pressure drop. The maximum particle velocity is always significantly less than twice the mean flow velocity for shear thinning fluids, but it can exceed this value in shear thickening fluids. In vertical down-flow, particles are uniformly distributed over the pipe cross-section, and particle diameter and concentration have little effect on the normalised velocity and concentration profiles. Pressure drop, however, is greatly influenced by particle concentration.