物料在输送管道中的流动状态研究

散状固体物料在气力输送管道内的流动是极其复杂的，每种物料都有其独特的流动特征。通过分析散状固体物料在输送管道内的运动状态，可为正确地选择输送参数和设计气力输送系统提供依据。     

物料在输送管道中的流动状态

散状固体物料在气力输送管道内的流动是极其复杂的,每种物料都有其独特的流动特征。通过分析散状固体物料在输送管道内的流动状态,可为正确地选择输送参数和设计气力输送系统提供依据。     

气力输送装置中物料在管道内的输送机理分析

对物料在气力输送装置中的流动状太民和通过管道的输送机理进行了分析，提出了输送物料所需的最小气流速度公式，为气力输送装置的设计提供了依据。     

散状物料在气力输送管道中的密相流动数值模拟与分析

基于计算流体力学理论,采用CDF软件包中的Fluent软件建立了气固两相流在气力输送管道中的密相输送模型,对散状物料在气力输送水平管和竖直管内的流动过程进行模拟,得出了散状物料分别在水平管和竖直管的密相流动状态,可为气力输送系统的研究和设计提供参考依据。     

气力输送系统在聚碳酸酯装置中的应用

气体输送是利用空气或气体的流动,在管道中输送干燥的散装固体粒子或颗粒物料的过程,空气或气体流动直接给管内物料提供移动所需的能量。本文介绍了气力输送系统基本原理及其特点,并结合气力输送装置实例,分析气力输送系统操作影响因素,确定稀相气力输送系统在聚碳酸酯装置在改、扩建工程中应用推广的可行性。     

密相气力输送水泥粉体流动特性研究

论文建立了工业级别1∶1正压旋转供料器气力输送实验系统。在本实验系统上以两种不同水泥粉体为输送物料进行气力输送研究,通过改变输送管道内的气体速度得出了固体输送能力、平均固气质量比、固体平均速度及单位长度压力损失等参数的变化规律,为该类型气力输送水泥粉体提供依据。     

正压流态化气力输送粉煤灰流动参数变化研究

管道气力输送是利用压缩空气作为动力在管道内输送固体物料的一种常用的粉粒状颗粒输送方式[1]。目前这种输送方式已经广泛应用于电力、化工、建材、钢铁、食品等行业,正在逐渐成为一种较为通用的输运手段,占有越来越高的比重[2]。其中,上引式流态化仓泵式气力输送方式由于稳定性好、系统相对紧凑、成本较低等优点在固体粉状颗粒输送中应用广泛。固体输送能力、固体颗粒速度、压力损失等参数是气力输送系统重点关注的参数[3],也是需要在设计气力输送系统时必须考虑的问题[4-5]。     

气力输送装置中管道堵塞机理及原因分析

物料在气力输送管道中的流动状态实际上复杂多变,管道堵塞现象时有发生。本文通过分析物料在气力输送管道中的输送原理及堵塞机理,阐述了产生堵塞的诸多原因,进而提出了从气力输送装置的规划设计、输送工艺的制定、设备的加工安装调试,到物料本身的特性等方面进行预防和解决堵塞的方法,以避免这种故障出现。     

如何避免固体流动降低给料效率

“根据一个快速分析显示,目前有越来越多的人意识到应该了解散状固体物料是如何输送和流动的,以及如何影响材料输送系统的。”J＆J公司的高级顾问BrianPittenger先生表示,“但当谈到材料的流动特性时,加工商对此知之甚少。”J＆J公司可提供广泛的测试服务,以确保散状固态原材料能够无障碍地通过给料系统。在近50年的发展历史中,该公司已经检测了超过10000种散状固体物料。     

粉煤灰中浓度气力输送管道压降研究

对于粉体气力输送流动区域划出中等浓度区，使浓相输送与稀相输送的区分变得清楚、分析了粉体气力输送管道压降的主要影响因素，在量纲分析基础上，对中浓度气力输送提出一个比较简洁的管道压降关联式，与文献的实验数据进行拟合，结果表明该式可以很好地描述粉煤灰中浓度气力输送管道的总压降。对于给定的一个相图，该式的系数k、有一固定的数值；此值与物料质量流率（或气体质量流率）、料气比无关。     

Low-Velocity Pneumatic Conveying Calculations for a High Concentration of the Particulate Material

The assumption that a moving solid–gas mixture is quasi- homogeneous and is characterized by some pseudoviscosity allows one to use conventional hydrodynamic methods and to generalize numerous experimental data on the low-velocity pneumatic conveying of various particulate materials. Formulas are derived for calculating the friction pressure drop criterion and the local flow-resistance coefficient in bent pipes. These formulas take into account the relative velocity, concentration, and properties of the solids. Basic principles are developed for the design of stepped-diameter pipelines of complicated configuration for long-distance pneumatic conveying.     

The influence of particle shape on flow modes in pneumatic conveying

The transportation of particles along pipes or ducts using an imposed gas flow is known as pneumatic conveying. The type of granular flow in such systems is strongly dependent on the imposed gas flow rate, and can be categorised by a distinct set of modes. These modes range from dilute flow, where the grains are entirely suspended in the gas, to moving dunes and slug flow, in which the bore of the pipe is blocked by a slow moving plug of material. Understanding the transitions between these modes is critical to the design and application of pneumatic conveying systems. Particle shape is a crucial factor in systems with gas–grain interactions but has so far been overlooked in models of pneumatic conveying. We carry out a series of simulations using the discrete element method coupled to gas flow and show that particle shape is critical to the transition between different flow modes. Particles which are spherical, or nearly spherical, transition to slug flow at high gas flow rates, whereas non-spherical particles transition instead to dilute flow. We show the lower voidage fraction in beds of non-spherical particles is crucial to explaining this behaviour.     

气锤控制改进

为解决PVC专用树脂生产中部分设备或管道容易出现树脂黏附、物料堆积等问题,在以上位置安装了气锤。为避免用电设备带来的安全风险,采用气动控制方式控制气锤。介绍了气锤与气锤控制器的连接方式。     

海上平台仪表气管道设计探讨

结合海上平台仪表气管线的布置设计进行了探讨,概述了气动阀门的动作原理以及供气系统的流程,并对仪表管线布置设计时需要注意的问题进行了总结,希望为以后相关项目平台仪表气管线设计提供一些参考。     

Dichtstromförderung

High density pneumatic conveying . In distinguishing between high density pneumatic conveying and low density conveying it is insufficient to merely use the solids loading to characterize the various flow states. Less ambiguous classification is possible only on the basis of the diagram of state of pneumatic conveying. Most flowable bulk solids can be transported through normal smooth-walled piping in the high density mode with normal conveying equipment. In contrast, fine-grained products in particular tend to adhere to the wall and form blockages. Paying due attention to the differing flow properties of various bulk solids and to the mechanisms of blockage formation and clearance, various new conveying techniques and piping types have been developed in recent years, permitting in some cases the transport of adhering, abrasive, and attrition-sensitive materials. Since conveying pressures up to about 6 bar are usual in the high-density regime, various combinations of pressure vessels are primarily used for feeding the bulk solids into the conveying pipes. The advantages of conventional, and also special high-density conveying systems are discussed with the aid of examples.     

电容层析成像测量气固两相流的影响因素

气力输送管道内经常出现的磨损现象和被测介质的不透明性,使得运用常规方法测量固体流动时的参数困难重重。ECT作为最先进和最有效的方法之一,可在线测量流动管道内固体横截面浓度分布和固体速度,便可计算得到固体质量流量。然而在大部分实际应用中,存在许多因素会影响管内固体的横截面浓度分布和固体的湿度值,使计算质量流量时产生误差。本文通过探讨找到解决此问题的方法,使得计算误差减小到可以忽略,结果更贴近实际情况。     

炭黑密相气力输送系统设计

随着橡胶工业的发展，以及气力输送特有的优点，气力输送系统越来越广泛地应用于输送炭黑的过程中。以炭黑气力输送系统为研究对象，详细介绍了系统设计的基本参数确定、气力输送形式的确定、压送罐客积的设计、输送管道的设计，并通过输送系统压力降的计算验证了设计参数的取值是合理的。     

紊流双套管气力输灰技术及其设计要点

紊流双套管密相气力输送技术与其它气力输送技术明显不同是干灰不需要悬浮输送，因而其系统的设计、运行方式有其鲜明的特点：输送能力大，需要的输灰管道很少，输送速度低对系统的磨损轻。该技术在水泥余热利用中得到了成功的应用。     

Pneumatic transport of granular materials with electrostatic effects

The methodology of coupling large eddy simulation (LES) with the discrete element method was applied for computational studies of pneumatic transport of granular materials through vertical and horizontal pipes in the presence of electrostatic effects. The LES numerical results obtained agreed well with the law of the wall for various y⁺‐ranges. The simulations showed that a thin layer of particles formed and remained adhered to the pipe walls during the pneumatic conveying process due to the effects of strong electrostatic forces of attraction toward the pipe walls. Particle concentrations were generally higher near the pipe walls than at the pipe center resulting in the ring flow pattern observed in previous experimental studies. The close correspondence between particle velocity vectors and fluid drag force vectors was indicative of the importance of fluid drag forces in influencing particle behaviors. In contrast, the much weaker particle–particle electrostatic repulsion forces had negligible effects on particle behaviors within the system under all operating conditions considered. The electrostatic field strength developed during pneumatic conveying increased with decreasing flow rate due to increased amount of particle‐wall collisions. Based on dynamic analyses of forces acting on individual particles, it may be concluded that electrostatic effects played a dominant role in influencing particle behaviors during pneumatic conveying at low flow rates, whereas drag forces became more important at high flow rates. © 2011 American Institute of Chemical Engineers AIChE J, 2012