石灰长距离气力输送系统的试验研究

基于气力输送理论,通过石灰的长距离输送试验系统的建立,研究输送过程中耗气量、管道压力损失、物料输送前后的状态等重要输送特性。结果表明,将气力输送应用在长距离的石灰输送上是完全可行的,可解决钢铁行业的高粉尘污染问题,极大地改善工作环境。     

颗粒粒径对气力输送影响的数值模拟与分析

在气力输送实验台上,以空气为输送介质,砂石为输送物料,进行水平管道流动特性实验;并以Euler方法为基础,建立数学模型,利用Fluent软件进行模拟。结果表明:水平管道底部颗粒浓度沿轴向不断增大,接近管道尾部时浓度减小;气相输送速度相同时,颗粒粒径越小,则水平管道内压降越小,颗粒在管道内分布越均匀,越容易获取加速度;通过对比可知,模拟所得结论与实际测量结果相符。     

小麦气力输送流场颗粒流化特性数值模拟

目的 探索仓泵式气力输送小麦颗粒时不同输送压力下罐体及引出管内颗粒的流化特性,从而得出最佳操作压力。方法 利用Solidworks建立简易的等比例发送装置三维模型,采用模拟仿真软件Fluent对0.25、0.3、0.35 MPa等3种不同输送压力进行数值模拟,并利用CFD–Post进行数据后处理。结果 当进气口压力为0.35 MPa时物料最先输送完毕,用时为10 s。整体发料过程从引出管入口至出口处三者压力分别降低了97.1%、96.8%、98.1%,其中当进气口压力为0.3 MPa时,压力降低最小,能量利用率最高。结论 输送压力越大输送速度越快,其压降也最大。考虑经济性与高效性可得,最佳进气口压力为0.3 MPa。     

石灰石粉对泵送混凝土性能影响的试验研究

本文主要研究了单掺石灰石粉、石灰石粉与粉煤灰复掺对泵送混凝土拌合物工作性和抗压强度的影响,研究表明：掺加石灰石粉可以改善泵送混凝土的工作性能,与单掺石灰石粉相比,石灰石粉与粉煤灰复掺,具有复合叠加效应,不仅可以改善泵送混凝土的工作性能,同时可提高泵送混凝土的抗压强度。     

2种粉体气力输送系统的对比选型

为了解决某工程项目中粉煤灰输送系统的选型问题,从设备投资和运行电耗方面对仓泵输送系统和罗茨风机输送系统进行对比分析。结果表明,对于6个单只最大量为911 kg/h的卸灰口,输送距离为200 m的输送系统而言,仓泵输送系统比罗茨风机输送系统设备初投资多33.22万元,运行电费每年节省14.2万元,超出部分投资静态回收期为2.34 a。     

气力输送粉煤灰固相浓度的超声检测研究

为了得到不同气力输送条件下管道内的固相浓度,以压缩空气为输送载体,以干燥粉煤灰为输送物料进行气力输送实验,利用低频超声测试系统对气力输送不同浓度的粉煤灰进行超声衰减测试,并选取合理的衰减信号处理模型。结果表明,在气力输送初始阶段,粉煤灰浓度会随着表观气速的增大而增大,随着输送进程的继续,发送仓泵内的物料减少,使得管道内粉煤灰浓度减小。     

粉体密相气力输送理论与技术进展

综述了密相气力输送的理论,并对目前开发的密相气力输送装置进行了介绍,分析了各种形式装置的技术指标及性能,为进一步完善密相输送理论和开发新型密相气力输送装置奠定了基础。     

氧化铝粉体气力输送过程的流动状态检测

在气力循环输送提升管实验装置中检测氧化铝粉体的流动状态,在提升管的不同测点位置布置电磁感应线圈,添加铁磁颗粒作为输运物料氧化铝的示踪颗粒,利用电磁感应声卡信号采集装置测量电磁感应系数。结果表明,电磁感应系数与气力输送提升管内的氧化铝、铁磁颗粒流量存在线性关系,随着测点高度的增大,电磁感应系数逐渐减小;提升管发生堵塞时,堵塞测点截面以上的电磁感应系数开始减小,截面以下各测点的电磁感应系数开始增大;通过增大喷动风量,可有效改善提升管内颗粒的分布状态。     

不规则宽粒径石灰石粉脱硫及气力输送技术

通过分析干法脱硫技术及其影响因素,如石灰石性能和石灰石颗粒直径等,提出脱硫剂的选择及气力输送的方式,同时分析了气力输送中的问题,如透气性差和保气性差引起的不易流化等,并相应提出解决办法和输送设计方案。针对不规则宽粒径石灰石粉粒具有的特殊颗粒学特性和复杂气固两相流场,提出了解决方案,为更好地设计石灰石粉气力输送系统提供参考。     

气力输送中PVC粉体静电带电影响因素

为了研究工业中常用的聚氯乙烯(PVC)粉体在气力输送过程中的静电影响因素,以PVC粉体为输送对象,以荷质比为指标,研究PVC粉体的下料质量流量、气流速度、气单位体积的气体中所含粉体的质量和球阀开度对粉体带电的影响。结果表明：当下料质量流量一定时,PVC粉体的荷质比会随气流速度增大而增大,随球阀开度减小而减小;当气流速度一定时,PVC粉体的荷质比会随下料质量流量增大而减小,输送颗粒的荷质比存在临界值为0.2μC/kg;当单位体积的气体中所含粉体的质量一定时,下料质量流量对PVC粉体荷质比影响要大于气流速度对其的影响;当下料质量流量一定时,PVC粉体的荷质比会随球阀开度的减小而减小。     

Investigating Straight-Pipe Pneumatic Conveying Characteristics for Fluidized Dense-Phase Pneumatic Conveying

This article presents results from an investigation into the pneumatic conveying characteristics (PCC) for horizontal straight-pipe sections for fluidized dense-phase pneumatic conveying of powders. Two fine powders (median particle diameter: 30 and 55 µm; particle density: 2300 and 1600 kg m^?3; loose-poured bulk density: 700 and 620 kg m^?3) were conveyed through 69 mm I.D. × 168 m, 69 mm I.D. × 148 m, 105 mm I.D. × 168 m and 69 mm I.D. × 554 m pipelines for a wide range of air and solids flow rates. Straight-pipe pneumatic conveying characteristics obtained from two sets of pressure tappings installed at two different locations in each pipeline have shown that the trends and relatively magnitudes of the pressure drops can be significantly different depending on product, pipeline diameter and length and location of tapping point in the pipeline (indicating a possible change in transport mechanism along the flow direction). The corresponding models for solids friction factor were also found to be different. There was no distinct pressure minimum curve (PMC) in any of the straight-pipe PCC, indicating a gradual change in flow transition (change in flow mechanism from dense to dilute phase). For total pipeline conveying characteristics, the shapes of the PCC curves and the location of the PMC were found to be significantly influenced by pipeline layout (e.g., location and number of bends) and not entirely by the dense-to-dilute-phase transition of flow mechanism. Seven existing models and a new empirically developed model for PMC for straight pipes have been evaluated against experimental data.     

粉体性能对浓相气力输送特性的影响

气力输送过程中物料性能是确定输送特性的重要因素,因此,粉料气力输送技术的实现要以对粉料的性能研究为基础。文中对影响气力输送的粉体基本性能及其相关参数做了较全面分析,其中粒子尺寸、粒径分布、形状是影响粉料是否可适用于浓相气力输送的关键参数,其它特性都与这3种特性相关联。介绍了几种应用广泛的粉料气力输送特性分组方法,并进行了简要评述,同时指出了今后的研究方向。     

高速火星尘暴模拟装置气力输送系统设计

开展火星尘暴环境地面模拟实验来验证火星探测器的性能是至关重要的,因此须建立火星尘暴环境的地面模拟装置。本文在对国外火星尘暴和气动模拟设备及其技术特点分析的基础上,提出了采用二次风输送的高速火星尘暴模拟系统总体方案,进行了高速火星尘暴气力输送流程的设计,并给出了沙尘质量流量、输送混合比、输送速度、输送压力、管道直径以及二次风量等气力输送参数的算式。本文研究成果可为我国的高速火星尘暴模拟装置工程设计及实施提供参考。     

气力输送在锅炉飞灰回燃技术中的应用

以山东省内几家热电厂75、130t/h循环流化床锅炉飞灰回燃、热效率提高为例,介绍气力输送系统在热电厂飞灰回燃过程中的应用,对热电厂飞灰含碳量高的原因进行分析,详细分析飞灰回燃系统的工艺流程,并对飞灰回燃前后的含碳量及成本进行对比。结果显示:飞灰回燃技术能够显著提高煤炭的燃烧率,提高锅炉的热效率。     

A Pressure Drop Model for Positive Pneumatic Conveying of Flour Through a Vertical Pipeline

A differential equation of motion for gas-flour two-phase flow in a vertical pipe was first derived based on the momentum conservation and by adopting two empirical expressions for the velocity ratio of flour to gas and frictional coefficient between flour and pipe wall, and then a pressure drop model for dilute positive pneumatic conveying of flour through a vertical pipeline was developed by employing the continuity and state equations for gas. The conveying tests were conducted on a positive pneumatic conveying system of flour in a flour mill. Under each of the six different flow conditions, the conveying parameters, such as the flour and gas mass flow rates and the pressure drop between two selected cross sections on the vertical pipeline were measured. The pressure drop between the two selected cross sections was evaluated using the pressure drop model for each of the six flow conditions. The calculated values of pressure drop agree well with the measured data, and it is demonstrated that the model is applicable to vertical positive pneumatic conveying systems of flour.     

岩石粉状乳化炸药气流输送管道积药问题探讨

岩石粉状乳化炸药管道内是否积药受风速、混合比、物料颗粒大小、加料是否均匀及物料温度等因素的影响,可以通过控制工艺参数来减少管道内积药,保证生产的安全和顺畅.     

Changes of Dextrose Particles with Pneumatic Conveying: Analysis of Size and Shape

When conveying particulate materials, changes in size and shape of individual particles can be observed. These changes can have a great impact on the bulk powder and affect its flow properties in the pipeline. Changes can be wanted or unwanted depending on the whole process chain and final use of the powder. In this investigation, dextrose monohydrate particles were pneumatically conveyed repetitively in a pilot plant–scale rig, and the size and shape of the particles were characterized by a semiautomatic image analysis method. This characterization was done qualitatively by observing micrographs and quantitatively for each individual particle (a total of 16,120 dextrose crystals) by using two statistical diameters and two shape factors. The effect of the changes in shape and size of the particles on the mass flow rate in the system was studied. It was concluded that the mass flow rate of the pneumatic conveying tests was not affected considerably by the changes of the dextrose particles.