工业级管道中粉煤浓相流动特性

分别以干燥空气和粉煤为输送载气和介质，在39 mm工业级水平不锈钢管内进行了浓相气固两相流动特性实验研究。高速摄像仪拍摄到的粉煤流型表明，浓相输送条件下存在分层流。在流化气和调节气协同作用下，工业级管道中的粉煤浓相输送规律与此两路气流流量密切相关，并获得了39 mm管径下的粉煤气力输送相图。与管径较小的20 mm水平不锈钢管输送结果的比较表明：较大管径条件下，输送压力对粉煤流率的影响更为显著，输送的经济气速相对较高；相同输送通量情况下，较大管径的输送单位管长压降低，且输送通量变化引起的单位管长压降变化也较为平缓。     

高压浓相粉煤气力输送特性及信息熵分析

在输送压力可达4.0MPa,固气比高达450kg/m3的高压气力输送试验台上,用氮气进行粉煤高压浓相气力输送试验研究。分别在不同的输送差压、浓度和速度等条件下进行了输送试验,考察操作参数对煤粉固气比等气力输送特征参数的影响,用信息熵分析试验过程中采集到的压力波动时间序列,探讨流动稳定性和流型变迁过程中信息化趋势,建立信息熵和流型之间的关系。结果表明在输送差压增大的过程中,固气比和Shannon信息熵均增大;气体流量与Shannon信息熵和固气比之间呈现较好的规律性;不同流动形态的Shannon熵差异较大,不同流型之间的Shannon熵区分度较好。Shannon信息熵分析为研究高压浓相气力输送流型及其转变特性提供了一种行之有效的方法。     

柱塞气固两相流输送特性

为了研究柱塞式气力输送气固两相流的输送特性,对实际的工业气力输送系统进行1∶1试验台改造,首先进行了粉煤灰在输送管内的流动模式试验;然后进行粉煤灰输送压力、输送质量流量特性试验;最后考察了主进气流量、补气流量、助吹气流量对粉煤灰输送量、固气比的影响。研究表明,柱塞式气力输送流动模式以密相栓柱流为主,其灰栓长度为0.8～2.3 m,移动速度约为2.8～11.3 m·s^-1;输送压力与输送流量呈双曲线特性,且随着气量的增加输送量增大;主进气流量起主导作用并与输送粉煤灰质量流量呈单调上升抛物线关系,与固气比呈上凸抛物线关系即先增大后减小。研究结果对柱塞式气力输送系统的工程设计、运行和理论研究提供依据并具有指导作用。     

煤粉气力输送固气比对烧成系统能耗的影响

分析了A、B两类煤粉计量与气力输送技术的气力输送固气比的差异以及其对水泥烧成系统煤耗、电耗的影响.结果表明,在保证计量设备低磨损、低维护量、高运转率前提下,对于5 000t/d熟料生产线,采用A类技术的煤粉秤因高固气比输送,每年可节省原煤约797t,节电约79 200kW·h.     

煤粉上出料式发送罐气力输送特性

在常压上出料式发送罐气力输送试验台上,以氮气为输送介质,研究煤粉气力输送特性。通过试验分析了流化风量、充压风量、提升管入口处气体注入速度对煤粉质量流量、固气比等特征参数的影响,并将典型试验工况与高压输送进行了比较。结果表明：随着流化风量的增大,煤粉质量流量、固气比均呈现先增大后减小的趋势。随着充压风量的增大,煤粉质量流量逐渐增大,固气比呈现先增大后减小的趋势。随着提升管入口处注入速度的增大,煤粉质量流量逐渐增大,固气比呈现先增大后减小的趋势。与高压输送相比,常压输送的质量固气比较高,气耗率及输送能耗较低。     

上出料系统粉煤密相气力输送特性及其与下出料系统的比较

考察了气体进入方式和输送压力对上出料发料罐系统粉煤密相气力输送特性的影响,并比较了上出料和下出料发料罐系统的煤粉输送量、固气比和稳定性差异。结果表明,在上出料发料罐系统中,随锥部气增加,煤粉输送量和固气比呈先增加后减小趋势;随底部气和调节气增加,煤粉输送量和固气比呈减小趋势;随输送压力增加,煤粉输送量和固气比先明显增加后增加趋势减弱。与上出料发料罐系统相比,相同输送差压下,下出料发料罐系统具有较高的输送量和固气比,但二者均具有良好的输送稳定性。     

文丘里管收缩段高固气比气固两相流压降模型

为建立高固气比(10 kg/kg相似文献   

一种粉料的输送特性研究

利用自主研究设计的工业规模级气力输送装置,分析研究了一种粉料稀相气力输送的规律.通过在两条不同长度输送线上的大量系统实验,得出输送量、输送压力、气量、固气比、表观气速等输送参数间的相互关系,展现了该粉料输送的宏观规律.同时对气力输送设计计算最重要的参数“管道压降”进行分析讨论,整理拟合出该粉料不同输送量下的压降模型,并且其计算值与实际值吻合较好,对工程应用具有一定指导意义.     

栓流密相气力输送特性的试验研究

为研究栓流密相气力输送气固两相流的输送特性,进行了粉煤灰在输送管内的流动模式试验和粉煤灰输送压力、物料流量特性试验.采用EcT技术测试了粉煤灰在输送管内的流动模式,并考察了主进气流量、补气流量、助吹气流量对物料流量、固气比的影响.研究表明:粉煤灰在输送管内的流动模式是以栓流密相为主,其灰栓长度为0.8～2.3 m,移动速度为2.8～11.3 m/s;输送压力与物料流量成双曲线特性,且随着空气流量的增加物料流量增大;主进气流量起主导作用,并与物料流量成单调上升抛物线关系,与固气比成上凸抛物线关系,即先增大后减小.     

粉煤密相气力输送流型

基于电容层析成像技术对粉煤密相气力输送系统的流型进行了研究,获得了水平管和竖直上升管粉煤密相气力输送系统的典型流动形态。研究结果表明,水平管输送时的流型随时间复杂多变,典型流型有满管流、沉积层流、悬浮流等;统计分析发现,随表观气速不同,存在明显的主导流型;结合固相速度及管道压力信号分析,展示出其与流型之间存在一定的对应关系,进一步证实了密相气力输送系统的不稳定性特征。对竖直上升管的ECT测试结果表明,输送流型为环核结构。     

电容层析成像在高压浓相煤粉气力输送中的应用

Electrical capacitance tomography (ECT) was applied to dense-phase pneumatic conveying of pulverized coal, including the visualization of gas-solid flows in a horizontal pipeline.The pressure of experimental setup was up to 4.0 MPa, the solid-gas ratio was up to 11.73 kg·kg-1, and the diameter of conveying pipeline was 10 mm.The pipeline thickness of 8-electrode ECT system was 5 mm.An improved AC-based capacitance measuring circuit was developed.Single channel capacitance measuring circuit was adopted to si...     

Investigation on characteristics of pulverized coal dense-phase pneumatic conveying under high pressure

Experiments of dense-phase pneumatic conveying of pulverized coal were carried out in a test facility with a conveying pressure up to 4 MPa. The influence of fluidization nitrogen flow rate, the flow rate of supplementary nitrogen, and the pressure difference between sending hopper and receiving hopper on the solids to gas ratio and the solid mass flow rate was investigated. Test results indicate that with the increase in fluidization nitrogen flow rate, the solid mass flow rate increases, and the solids to gas ratio increases at first and then declines. When the fluidization of pulverized coal in the sending vessel becomes intensive, with the increase in supplementary nitrogen flow rate, the solids to gas ratio declines and the solid mass flow rate increases. And the solid mass flow rate increases linearly with the increase in pressure difference between two hoppers. The experimental results provide a database for the design and operation of a dense-phase pneumatic conveying system. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Study of the pressure drop of dense phase gas-solid flow through nozzle

Pressure drops are measured on different nozzles of various pipe sizes in dense phase pulverized coal pneumatic conveying. From the experimental results, we conclude that the effect of the gas phase nozzle pressure drop is negligible when comparing with the solid phase pressure drop in the experimental range. The main influence factors contributing to the nozzle pressure drop are gas and solid mass flow rate, solids loading ratio, and the diameters of the nozzle inlet and outlet. A new model was developed to predict the nozzle pressure drop in dense phase pneumatic conveying of pulverized coal based on the Barth's pneumatic conveying theory. The pressure drop predictions from the model are in good agreement with the experimental values. The model quantified the important influence factors of the nozzle pressure drop.     

Conveying Characteristics of Pulverized Coal in a Top‐Discharge Blow Tank System

Based on the experiments of pulverized coal pneumatic conveying using nitrogen as carrier, the influences of riser inlet height above the gas distribution plate, riser diameter, pulverized coal external moisture content, and supplemental gas flow rate on the conveying characteristics such as pulverized coal mass flow rate and solid‐gas ratio were investigated in a laboratory‐scale experimental setup of a top‐discharge blow tank under atmospheric pressure. There exists an optimal riser inlet height for a given top‐discharge blow tank. The supplemental gas is one of the critical factors affecting the conveying stability and continuity. A model for material mass flow rate prediction with errors ranging from –25 % to +15 % is presented.     

Effect of moisture content on dense-phase conveying of pulverized coal at high pressure

In dense-phase pneumatic conveying, the solid moisture content can significantly influence the conveying process, but there are very few studies in the open literature. In this study, the conveying experiments of two pulverized coals with various moisture contents were carried out at a 4MPa high pressure and dense-phase pneumatic conveying facility. Results show that the whole conveying system can be stably and controllably operated under the condition that moisture content below ∼8%. With the increase of moisture content up to ∼8%, the mass flow rate of 280 μm pulverized coal increases at first and then decreases, while that of 55 μm pulverized coal decreases continuously. The method of solid friction factor correlation is used to investigate pressure drop of the horizontal pipe, and non-dimensional parameters—Fr number, moisture content M and solid loading ratio μ—are investigated. The pressure drop predictions by this correlation are in good agreement with the experimental data. The solid friction factor correlations indicate that the fine coal is more sensitive to M, and μ plays a more important role for the coarse coal.     

Flow Characteristics and Shannon Entropy Analysis of Dense‐Phase Pneumatic Conveying of Pulverized Coal with Variable Moisture Content at High Pressure

Experiments consisting of dense‐phase pneumatic conveying of pulverized coal using nitrogen were carried out in an experimental test facility, with a conveying pressure of up to 4 MPa. The influences of the conveying differential pressure, the coal moisture content, the gas volume flow rate and the superficial velocity, on the solid‐gas ratios, were investigated. The Shannon entropy analysis of the pressure fluctuation time series was developed to reveal the flow characteristics. By investigation of the distribution of the Shannon entropy at different conditions, the flow stability and the evolutional tendency of Shannon entropy, in different regimes and regime transition processes, were revealed, and the relationship between Shannon entropy and the flow regime was also established. The results indicate that the solid‐gas ratio and the Shannon entropy rise with increases in conveying differential pressure. The solid‐gas ratio and the Shannon entropy reveal preferable correlation with the superficial gas velocity. Shannon entropy is different for different flow regimes, and can be used to identify the flow regimes. Both the mass flow rate and the Shannon entropy, decrease with increases in moisture content. Shannon entropy analysis is a feasible approach to researching the characteristics of the flow regime, the flow stability and the flow regime transitions in dense‐phase pneumatic conveying systems, at high pressure.     

Horizontal pneumatic conveying from a fluidized bed

In this paper the feasibility of feeding a horizontal pneumatic conveying line directly from a fluidized bed is explored by investigating the relationships governing the solids mass flow rate in such a pipe as a function of both pressure drop and pipe length. Three different materials were fluidized by air and discharged though a 25 mm internal diameter pipe. Materials used were turnip seeds of mean diameter 1.5 mm, carbon steel shot of mean diameter 0.73 mm and plastic pellets of mean diameter 3.76 mm. Several pipe lengths were used, from 0.75 to 1.77 m. The experiments showed that it is feasible to feed directly from a fluidized bed to a horizontal pneumatic conveying line. The flow regime in the pipe was that of dense phase conveying also called slug flow. The data collected show that there is a clear relationship between the pressure drop down the conveying line and the discharge rate of solids from the line. The discharge rate is also dependent on the pipe length.In previous studies of pneumatic conveying, the solids and gas mass flow rates have been independently set, which cannot be done if the conveying line is fed from a fluidized bed. For a pipe fed from a fluidized bed, the solid and gas mass ratio are coupled and this was modelled using the theory for air-augmented granular discharge through an orifice in a hopper or silo of Nedderman et al. [1983. The effect of interstitial air pressure gradients on the discharge from bins. Powder Technology 35, 69-81], but as modified by Thorpe [1984. Air-augmented flow of granular materials through orifices. Ph.D. Thesis, University of Cambridge] for horizontal discharge. This was then combined with a modification of the theory of Konrad [1981. Ph.D. Dissertation, University of Cambridge] to give a prediction of the total pressure drop and the gas and solid mass flow rates. This combined model for dense-phase conveying from a fluidized bed was found to give an excellent fit to the data using the standard values for the constants in every equation. The predictions of the combined model also agree well with the experiments of Konrad [1981. Ph.D. Dissertation, University of Cambridge] for discharge from a hopper into a horizontal conveying line.