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.     

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。     

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。     

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。     

聚烯烃类粒料气力输送槽车的开发

聚烯烃类产品的散装化运输具有显著的经济效益。通过对高密度聚乙烯（HDPE）粒料进行的正压密相栓流气力输送实验研究，获得了输送这种物料的压力降和固气比计算式，进而研制出罐体容积50m^2，不平输送距离70m、垂直输送高度30m、输送量15t/h、物料卸余率低于0.3%的HDPE粒料气力输送槽车。这种国产化槽车的开发成功，填补了国内空白，并巳在燕山石化公司得到应用。     

密相气力输送系统的比较

在建材、冶金、化工等行业中,现广泛应用的稀相气力输送技术,其气流速度高、固气比低,耗气量大,且不适用粒径大和相对体积质量大的物料输送。而低速、低压的密相栓流输送新技术,既可在输送过程中实施对物料的加热、冷却和烘干;且当物料速度减少或粉料流量增大时,具有较高的系统稳定性。目前,国内外已相继开发了多种密相栓流气力输送系统,其成栓方式包括有脉冲气刀式、挤压式和重管式等多种,均各具特点。其中,脉冲气刀栓流输送系统在运行时,输送固气比高、耗气量低,且成栓方式简单、有效,应成为密相气力输送设计时优先考虑的系统。     

高固气比状态下的粉煤气力输送

在自建的气力输送系统上，进行了高固气比状态下粉煤气力输送研究.分别在内径为15、20、32 mm的管道中进行了输送实验,考察了操作参数对粉煤质量流量、固气比、表观气速等气力输送特征参数的影响.结果表明，输送固气比达到200～580 kg•kg^-1;随气体流量增加，粉煤的质量流量增大，而固气比降低;与输送压力的影响相比，管径对粉煤质量流量的影响程度更为显著;给出了基于本系统描述各参数之间相互关系的经验方程，表明较小的气量和较大的输送管径更有利于实现高固气比状态下的粉煤气力输送.     

轮胎厂白炭黑气力输送试验与局部模拟

在轮胎厂进行造粒白炭黑的密相气力输送的试验研究,得到白炭黑气力输送的特性参数.输送管径为DN125 mm,距离为80 m,3个弯头,气体压力为0.45 MPa,压力峰值为0.6 MPa,输送白炭黑的料气比可达到20,输送能力为7t·h-1.采用Fluent软件对一段输送管进行模拟的结果表明,在辅管进入主管的人口处,气体体积膨胀,速度增大,与气力输送末端输送速度增大相符合.     

循环流化床煤燃烧/热解多联供工艺中循环灰的密相气力输送

为考察循环流化床煤燃烧/热解多联供工艺中循环热灰的密相输送特性,在实验室建立的密相气力输送装置上分别考察了发料罐内的压力、总松动气量以及特殊位置处的松动气量等对输送固气比的影响。结果表明,在发料罐内压力一定的情况下．固气比随着总松动气量的增加而增大；发料罐内压力的增加也有利于固气比的增大；在发料罐内的压力及总松动气量一定的情况下,随着特殊位置1处松动气量的增加,固气比也随之增大。该密相气力输送方式基本可以满足CFB煤燃烧/热解多联供工艺的要求。     

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.     

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。     

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.     

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.     

测算散料低速栓流气力输送压降和栓速的新方法

低速栓流气力输送技术已广泛应用于散料输送，然而对其输送对象的研究大多数针对有规则形状的散料（如塑料切片、小麦），对于不规则形状的散料（如牛奶什锦早餐、玉米芽等）的研究却很少。提出了一种新的预测方法，它根据粒子的特性及从一个简单的垂直测试筒得到的数据，可以精确地预测低速栓流气力输送系统中的压降和栓速，即使是大型的气力输送系统。该方法适用于规则、不规则或不同性能（如不同形状、密度、粒径和粒度分布）的散料的低速栓流气力输送，预测的结果可满足设计和操作要求。     

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.     

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.