静电旋风除尘器除尘机理的探讨

本文根据静电旋风除尘器的试验结果，从理论上分析了除尘器的除尘机理，初步得出除尘器捕集的粉尘粒子不是指数曲线，分级效率不是静电除尘器和旋风除尘器的线性组合等结论。     

高效旋风器分级效率理论计算的新方法

本文根据旋风器内气流的轴向速度分布规律确定尘粒在旋风器内的平均停留时间;考虑筒体和锥体边界层内粒子的捕集分离,建立旋风器分级效率的数学模型,并推出了旋风器分级效率的理论计算公式.新理论公式考虑了旋风器内气体的三维速度分布规律及旋风器各主要结构参数和运行参数的影响,从捕集机理的角度看,新理论公式优于已有的分级效率公式;通过实验验证,新理论公式的计算值与实测值符合得较好.     

提高旋风除尘器效率的新设计方法

如何设计更有效的旋风除尘器已重新引起注意。严格的排放标准迫使工程师们去最充分地发挥旋风除尘器的能力。如果设计得更好,旋风除尘器控制粒子污染就能有效得多,而且提高了旋风除尘器的性能,可以大大减少对更复杂的第二级除尘器的需要。旋风除尘器构造简单,消耗能量少,能在高温高压下运行。旋风除尘器易于保持清洁卫生,所以对食品加工工业特别有用。一、有利于设计估算的新方法以前有一些推算旋风除尘器效率的尝试都不很成功。有些提出的模型是依靠Rosin等人在1932年首次发表的方法。 Leith和Licht发展了一种新的理论方法,可以根据物理性质数据和旋风除尘器设计尺寸比推算分级效率,还预示出和发表的     

旋风除尘器下降流量的研究

通过实验测定了常规旋风除尘器内下降流量铅高度的分布，发现在排气芯管入口断面附近有约２４％的短路流量，测定了安装不同类型减阻杆后的下降流量，发现非全长减阻杆下端固定时，有增加减阻杆上方断面下降流量的功效，这将延长含尘气流在除尘器内的停留时间，提高除尘效率。     

环缝气垫高效耐磨旋风除尘器的研究

提出在旋风除尘器内壁设置环缝套圈的增效防磨新方法，探讨高速含尘气流对器壁的磨损机理和二次扬尘现象。在2t／h燃煤锅炉上不同烟气流速下的对比实验表明：该新型旋风除尘器的除尘效率比普通旋风除尘器提高5％，平均阻力系数比普通旋风除尘器降低10％。     

电磁锁气排灰阀

保证除尘器,特别是旋风除尘器下部所配排灰阀的严密性,是提高除尘器效率的重要条件之一。基于这种考虑,我们研究了适用于除尘系统的φ100电磁锁气排灰阀。根据在玻璃工厂旋风除尘器中的使用情况,我们对φ100电磁锁气排灰阀的设计、试验、规定了几个基本指标；1.阀在连续进行开闭动作时的平均     

旋风除尘器的优化选用

一、前言所谓旋风除尘器的优化选用就是在满足一定的除尘效率下,使除尘装置的投资费用为最小。一般情况下,一组除尘器的总投资包括旋风分离器的固定投资和动力费用。单位时间内除尘装置的总投资与除尘器压降、旋风分离器数量有关。增加旋风分离器数量,降低了除尘器压降,使除尘器运行电耗减少,动     

旋风除尘器流场和浓度场的测试与分析

本文介绍了旋风除尘器内三维速度场、压力场及浓度场的试验成果,着重分析了旋风器内的浓度分布规律,并根据流场、浓度场的综合分析与试验,提出了改进旋风器性能的结构措施。     

旋风除尘器的设计计算

旋风除尘器是国内外常用的一种除尘器。它的性能与除尘器的结构形式、尺寸、进口风速、处理粉尘的真密度和粒径分布、气体粘度等因素有关。通过试验求得的旋风除尘器分级效率曲线都是一定尺寸的旋风除尘器在特定的进口风速下、用特定的粉尘试验求得的,不能把这条曲线作为该除尘器的普遍规律。旋风除尘器的实际运行工况(如除尘器筒体直径、进口风速、粉尘特性等)与试验工况不同时,除尘器的性能会相应发生变化。因此,如何根据实际的运行工况确     

监测旋风除尘器运行的简便方法

作者在所从事的几种旋风除尘器的试验研究中,发现正常运行的旋风除尘器,在多种处理风量下,灰斗的压力与旋风除尘器的压力损失均有固定的比例关系,灰斗漏风,会破坏这种固定比例,因而可监测灰斗压力及旋风除尘器进出口压力,用于了解旋风除尘器工作是否正常,这可作为监视旋风除尘器运行状态的一种简便方法。     

Numerical and experimental hydrodynamic studies of a lagoon pilot

The determination of residence time is of major interest in terms of the characterisation, design and modelling of most environmental engineering processes, where a proper and homogeneous fluid distribution is often essential, and especially in the domain of wastewater or waste material treatment. In this paper, two different numerical methods for obtaining theoretical predictions of residence time distributions using the finite volume method are used. The first one consists of solving a transport equation of the local mean age of the fluid, which is the average time that a fluid particle takes to reach any point of the domain from a supply inlet. The result obtained is a spatial distribution of the local mean age of the fluid, which may be displayed as isocontours in the space domain considered. The second one consists of injecting a virtual particle stream (i.e. a fluid particle having the same density as the surrounding fluid, and treated numerically as a tracer) and measuring the time elapsed between the injection and the termination of the trajectory using a Lagrangian reference frame. The result obtained is expressed as an exit time distribution and may be displayed as a histogram. Finally, a comparison with measurements of mean residence times of tracers in a lagoon is made in order to establish the relevance of this method in concrete form. The prediction enables the instantaneous determination of the geometrical characteristics of the flow that contribute actually to the residence time dispersion. Its appropriate use prior to the design of water treatment and waste material treatment installations should contribute to prevent undesirable flow patterns such as short-circuiting and dead spaces.     

Modeling and efficiency of ultraviolet disinfection systems

Modeling can play a particularly useful role in ultraviolet (u.v.) disinfection because of difficulties in measuring u.v. dose and the immediate results of disinfection. This model predicts bacterial survival in flow-through systems. The calculation takes into account the complex intensity patterns, non-ideal flow patterns, and non-linear curves of log survival vs u.v. dose. Based on the organismal dose-response, the number of survivors in each fraction of the residence time distribution is calculated separately and summed to calculate the average survival. The model uses as input data: the average u.v. intensity within the system, the residence time distribution, and an experimentally determined dose-survival curve in a simplified system where dose can be directly measured. The predictions of the model corresponded well with measured survival in a u.v. pilot plant study. The model was used to show the effects of flow dispersion on average survival by varying residence time distribution. Measures of capacity and efficiency of u.v. systems were derived and illustrated experimentally in simple cylindrical batch units and in two multiple lamp units.     

A semi-mobile flash dryer/calciner unit to manufacture pozzolana from raw clay soils — application to soil stabilisation

The use of hydraulic binders in the construction of durable housing or roads in developing countries is an efficient technique, for which there is a demand at various times and in dispersed places throughout the world. The problem of the need for these perishable products could be resolved by the local production of pozzolana from clay soils using a semi-mobile dryer/calciner plant. By means of theoretical modelling of the thermochemical phenomena involved, and different small-scale pilot tests, we have developed a flash calcination process to this end. The Malet company has designed and built an industrial 800 kg/h production unit International patent PCT/FR98/01149—Publication No. W098/55418. It can be dismantled, moved over land (road network) and sea, and assembled within a few days. Once installed, it can be in production in 1 h. We have turned to our advantage the various benefits of the flash technique: the construction is light and compact, there is no need for grinding materials after calcination, and short materials residence time inside the unit results in short process response time and reduced start and shutdown operations duration. We describe the plant here, giving details of establishing the mass/thermal balance, the design of the gas and materials circuits, the process control system, and the construction and packaging. The plant is largely composed of a drying cyclone, a hammer mill, a preheating cyclone, a multi-burner combustion chamber with its separator cyclone and three cooling cyclones. We then compare the performances of the hydraulic binder elaborated from the pozzolana out of the unit plus lime, with those of an ordinary Portland cement.     

城市住宅平均房价研究

城市住宅平均房价的水平及走势是政府监管市场的重要依据.目前城市住宅平均房价计算采用的是简单算数平均法,它不能客观地反映城市的平均房价.本文对城市住宅平均价格的求取方法进行研究,提出了利用加权平均法求取城市住宅平均房价的具体方法.     

Computational modelling of large aerated lagoon hydraulics

A good understanding of the hydraulic performance of aerated lagoons is required for their design and operation. A comprehensive numerical procedure has been developed for the three-dimensional computational modelling of the flow in large lagoons including high-speed floating mechanical surface aerators. This paper describes the procedure that consists of separate aerator modelling, then applying the obtained results as boundary data for a full lagoon model. A model application to an industrial aerated lagoon serves as an example of flow analysis. Post processing of the results by calculating the local average residence time (age of fluid) provides a powerful and intuitive technique to visualize and analyse the lagoon performance. The model has been verified by comparing the local average residence time predictions with measurements from a dye study. It is shown that the numerical modelling proposed is feasible and constitutes an effective new tool in improving the performance and design of industrial lagoons.     

入口截面高宽比对旋风分离器内流场的影响

气相采用雷诺应力模型(RSM)模拟,颗粒相采用拉格朗日坐标系随机轨道模型,模拟具有不同高宽比的入口截面下的旋风分离器内气固两相流流动特性。采用适当的高宽比,能使旋风分离器近壁面保持较高的气流速度,强化外旋涡,能使颗粒更容易被壁面捕集而分离,对提高分离效率有重要作用。     

土地处理系统流态试验及异重流的影响

在土地处理系统的反应器中进行流态试验,考察适用于土地处理系统流态试验的方法,并挑选重现性好的示踪剂.试验结果表明,土地处理系统水流流态为推流式,体积效率达到95%以上,轴向扩散属于中等分散程度,但存在一定的滞留区.采用阶跃法进行流态试验会由于异重流的影响使试验结果不能反映出反应器的真实流态：采用升流式运行,升阶法会增加平均停留时间,具有很好的推流效果和很低的扩散系数,降阶法则相反;降流式运行,降阶法增加了平均停留时间,有更大的体积效率,升阶法则降低了水流推流效果.因而阶跃法不适合土地处理系统的流态试验.脉冲法采用罗丹明B作为示踪剂的试验结果比NaCl具有更好的重现性、更加准确.     

A model study of ozone-sparged vessels for the removal of organics from water

Ozone-sparged vessels for the oxidation of a model organic compound, methanol, was studied. The parameters under study included superficial gas velocity, the gas phase ozone concentration, the rate of ozonation of methanol and its oxidative products, the residence time, etc. The scale-up method based on the mathematical model developed in this study accurately predicts the superficial gas velocity and the gas phase ozone concentration required for two larger geometrically similar vessels to achieve the same level of total organic carbon removal obtained in a small vessel.