低速高能效的浓相气力输送技术

低速浓相输送装置的出现,解决了物料在输送过程中易破碎、堵塞和磨蚀管道等难题,降低了耗气量。本文中综述了低速浓相输送的几种定义和输送过程中的相图、物料流动形态及相应的判定、影响浓相气力输送特性的因素等技术参数,并介绍了输送过程中经常遇到的堵管和磨损现象以及气力输送过程中的检测和自动控制技术,指出了今后的研究方向。     

论正压浓相气力输送技术在CFB中的应用

CFB的除灰方式及除灰系统对全厂的安全经济运行及环境保护有着重大的影响,正压浓相气力输送系统具有明显的节约能源减少维修费用改善环境和利于综合利用等优点。     

华电华源环境工程有限公司中标青海华电大通发电厂2×300MW机组正压气力除灰系统

近日,在青海华电大通发电厂2×300MW 机组正压气力除灰系统投标中,国电机械设计研究所华电华源环境工程有限公司一举中标。该项目位于西宁市,该期工程为2×300MW 发电机组的除灰配套项目。除灰系统采用正压浓相气力除灰系统,每台炉设一套正压浓相气力除灰系统,用于输送     

正压开放式气力输送水泥的流动特性

针对目前大宗正压开放式气力输送粉体过程中出现的料位低于临界料位值后会出现大面积腾涌、输送效率大幅度下降的问题,以山东省莒县某大型水泥钢板仓为研究对象,通过相似理论模拟设计开发开放式气力输送仓泵,并据此建立开放式气力输送系统;在该系统上以水泥粉体为输送物料,压缩空气为输送动力进行实验研究。结果表明:正压开放式气力输送过程中,固体质量流率、压力损失随料位的减小出现先增大后减小的趋势,拐点处对应的料位为临界料位。同时,研究发现临界料位随气体表观速度与平均固气质量比的增大呈减小趋势。     

正压拉法尔管仓泵气力输送硼钙石固体流量实验研究

针对目前工农业生产中部分工艺中对气力输送固相定量性要求较高的现状,建立常用的正压拉法尔管式仓泵气力输送系统,并建立后反馈自动控制系统。以硼钙石粉体为输送物料,分别采用精密称重传感器测试及超声测试方法研究输送过程中固体流量的变化规律。通过实验对比自动控制前后的固体输送能力的大小及稳定性发现,固体输送能力稳定输送时间段增加了16~18 s,自动控制后稳定段固体输送能力波动低于±8%,表明启动自动控制方案能更好地提高固体输送的稳定性。     

低能耗粉体物料气力输送的方法

粉体物料的输送有多种方式,采用管道气力输送是最经济环保的输送方式之一。对于长距离粉体物料气力输送,正压浓相加分段变径的设计思路是降低能耗/延长输送距离和减少管道磨损的最直接方法。     

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。     

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。     

多泵制正压浓相气力输灰系统的性能及其在天生港发电厂的应用

目前国内正压浓相气力输灰系统具有低能耗、耐磨损及系统简单等优点,但单泵制运行方式又制约了其在多灰斗、大机组电厂的使用。本文介绍了天生港发电厂多泵制正压浓相气力输灰系统,该系统配置相对简单、可靠,适合多灰斗、大机组电厂的除灰系统。     

气力输送设备概述

本文先就各种水平输送系统的适用范围及其能耗作一扼要介绍,然后对气力输送的主要机理进行讨论。为使气力输送简单易懂,拟将它分为流态、输送方式和输送设备来讨论。本文将叙述输送系统的结构要求,并规定各种可供选择方案的应用范围。     

密相气力输送系统中几种气量控制方式的比较

从调压范围、压力特性和流量特性方面介绍了减压阀的主要性能,讨论了气力输送交流中减压阀的选择和调节,分析了密相气力输送系统中各种气量控制方法,对其各自的优缺点进行了详细讨论,重点分析减压阀及减压阀与拉法尔联合气量控制系统的优、缺点,表明可调式拉法尔管是今后气力输送气量控制发展的方向。     

密相气力输灰管道的设计与应用

对气力输灰工程中密相输灰管道的设计和计算确定管内压力和速度的公式进行整理 ,同时可以得到较合理的管径和不同管径的长度。运行参数当已知时 ,给出的计算公式可作为设计的依据     

A Unified Scaling-Up Technique for Pneumatic Conveying Systems

A major challenge facing the designers of pneumatic transportation systems is how to scale up reliably based on the results from pilot-scale test facilities. Further, even if dense phase flow condition prevails at the start of the conveying system, it may be a dilute phase flow condition at the end of the pipeline. Hence, any scaling-up technique should be able to address the dynamic change of flow condition along the pipeline. The scaling-up technique presented here using the pressure drop prediction models based on modified Darcy-Weisbach equation successfully addresses these dynamic changes. It has been shown that the pressure drop coefficient 'K,' as defined by the models, is independent of the pipe diameter. Further, in the case of vertical conveying, 'K' has been shown to be independent of particle size distribution for a given material. The predicted pressure values were found to be in reasonably good agreement with the experimental results varying from 3.5% to 19.9%.     

A Unified Scaling-Up Technique for Pneumatic Conveying Systems

A major challenge facing the designers of pneumatic transportation systems is how to scale up reliably based on the results from pilot-scale test facilities. Further, even if dense phase flow condition prevails at the start of the conveying system, it may be a dilute phase flow condition at the end of the pipeline. Hence, any scaling-up technique should be able to address the dynamic change of flow condition along the pipeline. The scaling-up technique presented here using the pressure drop prediction models based on modified Darcy-Weisbach equation successfully addresses these dynamic changes. It has been shown that the pressure drop coefficient ‘K,’ as defined by the models, is independent of the pipe diameter. Further, in the case of vertical conveying, ‘K’ has been shown to be independent of particle size distribution for a given material. The predicted pressure values were found to be in reasonably good agreement with the experimental results varying from 3.5% to 19.9%.     

射流管在气力输送中的应用

对物料气力输送的各种供料方式的性能、特点和使用场合进行了比较 ,重点讨论了传统文丘里供料器实际应用中存在的问题 ,介绍了几种国内外新型的文丘里供料器结构及其特点和用途。指出采用组合式供料器 ,即将文丘里供料器与机械旋转式连续供料器进行组合使用 ,可以同时改善它们两者单独使用时存在的问题。文中介绍了LAVAL管密相输送气量控制方面的应用 ,指出LAVAL管在气力输送中主要起稳定空气流量和压力的作用 ,使输送过程稳定、均匀 ,并简要介绍了气力输送系统的设计方法和步骤     

An investigation of segregation and mixing in dense phase pneumatic conveying

Pneumatic conveying of bulk materials has become an important technology in many industries: from pharmaceuticals to petro-chemicals and power generation. Particulate segregation has been investigated in many solids handling processes. However, little work has been published on the segregation and mixing in pneumatic conveying pipelines, particularly in dense phase pneumatic conveying. Due to the character of dense phase flow, it is difficult to investigate the segregation in a flowing plug. A sampling device was designed and built to take samples from the pneumatic conveying pipeline after “catching a plug”. Several experiments were conducted over a range of gas–solids flow conditions with 3 mm nylon pellets and 3 mm ballotini as a segregating mixture. Experimental data combined with video footage were analysed to describe the segregation and mixing of solids plugs in pipes. This investigation provides initial research on establishing a segregation index in a flowing plug. A gas–solids two-dimensional mathematical model was developed for plug flow of a nylon-glass particulate mixture in a horizontal pipeline in dense phase pneumatic conveying. The model was developed based on the discrete element method (DEM). The model was used to simulate the motion of particles both in a homogeneous flow and as binary mixtures taking into account the various interactions between gas, particles and pipe wall. For the gas phase, the Navier Stokes equations were integrated by the semi-implicit method for pressure-linked equations (SIMPLE) using the scheme of Patankar employing the staggered grid system. For the particle motion the Newtonian equations of motion of individual particles were integrated, where repulsive and damping forces for particle collision, the gravity force, and the drag force were taken into account. For particle contact, a model with a simple non-linear spring and dash pot model for both normal and tangential components was used. This model employed a mixture of 3 mm pellets and ballotini as virtual materials with properties of nylon and glass. The results from the model are discussed and compared with experimental work and show qualitative agreement. Further modelling and experimental work in key areas is proposed.     

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.     

An Experimental Study on Degradation of Maize Starch During Pneumatic Transportation

Although attrition during pneumatic conveying is a common problem, very few publications can be found in the open literature on this subject. The particle-to-wall impact is perhaps the predominant cause of degradation since the particle impinges the wall surface at high velocities in dilute phase pneumatic conveying. The most important factors appear to be the conveying air velocity and moisture content. This article presents the experimental findings of a study on degradation of maize starch during pneumatic conveying process. The tests were carried out in a conveying setup having a pipe length of approximately 50 m and a pipe inner diameter of 50 mm in order to find out the breakage of particles under various airflow velocity conditions and temperatures. Dehumidified air was used during the experimentation, and the air temperatures used during these test were 100°C and 25°C. The experimental results indicated that for a given air temperature condition, the variation of attrition rate was a complex function of air velocity and solids loading ratio. Further, for any start pressure condition, the attrition rate was found to increase substantially with increase in air temperature.