密相气力输送物料流动状态分析及供料装置的选用

综述了低速密相气力输送中的相图和物料流动形态；介绍了密相输送供料装置（充气罐供料器、螺旋供料充气罐、高压旋转阀供料器）及其应用场合。同时简要分析了物料特性对密相气力输送的性能影响。     

气力输送工艺在煤粉输送中的应用

针对工业煤粉输送技术效率低、不安全等问题,介绍了稀相正压输送、密相正压输送和负压输送3种气力输送工艺的原理和使用现状,研究了密相输送工艺的原理和目前主流的栓流式密相输送技术。分析了稀相正压输送、密相正压输送和负压输送工艺各自的技术特点,并在投资、能耗、环保等方面进行对比。结果表明负压输送输送距离较短,稀相正压输送能量损失大、易发热,而密相正压输送固气比高、能耗低、管道和物料磨损小、噪声低、输送过程不易发热,更适合煤粉输送。     

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。     

Horizontal slug flow pneumatic conveying: Numerical simulation and analysis of a thin slice approximation

Slug flow horizontal pneumatic conveying of granular materials is a complex phenomenon, involving many interacting properties. Investigating internal properties such as bulk density and bulk material stress, particularly via experiment, is limited by practical considerations. A combined 3D DEM + 2D CFD algorithm is introduced as a complementary means of investigating such properties. Important aspects of the simulation work include the extraction of bulk density, bulk material stress, stress transmission ratio and boundary stress data as functions of time and position in one and two dimensions. Such data is presented and analysed in the context of existing assumptions and a resulting one-dimensional model for bulk material stress within a slug.     

水平分支管路气力输送阻力特性的预测

在水平T型分支管道中,用压缩空气作为输送气体,对平均粒径为0.25 mm和0.5 mm的砂石进行气力输送试验。通过试验和GRNN神经网络对输送表观气速和两分支管路流量控制阀开度发生变化时,各分支管路中的阻力特性进行了研究。结果表明:随着表观气速的逐渐减小和两分支管路流量控制阀开度差值的增加,各分支管路中的阻力特性相应地发生了变化。通过试验值和GRNN网络模拟值的对比,发现试验值和模拟值间相互吻合得较好,说明采用GRNN网络来模拟两分支管路中各自的阻力特性适应性较好。     

脉冲料栓式密相气力输送系统研究

介绍了脉冲料栓式密相气力输送系统输送装置和输送原理，分析了料栓在输送过程中的流动行为以及栓压与栓长栓速之间的关系，分析了料气速度比及压损公式，为设计和使用脉冲料栓式密相气力输送系统提供参考。     

Experimental study on the solid velocity in horizontal dilute phase pneumatic conveying of fine powders

The calculation reliability of pressure drop and gas-solid drag force in horizontal dilute phase pneumatic conveying strongly depends on the accuracy of gas-solid velocity correlation. However, there are limited studies on the solid velocity in horizontal dilute phase pneumatic conveying and it is important to further validate suitability of existing correlation of gas-solid velocity, especially for fine particles (such as pulverized coal). Consequently, in this paper, a negative pressure pneumatic conveying test rig is set up and two kinds of powders with different sizes are adopted. Optical fiber probe (OFP) was used to measure the volumetric solid concentration and particle velocity. The volumetric solid concentration was also calculated by using the measured particle velocity. The results show that the solid concentrations obtained by the two methods have good agreement, and discrepancy is within ± 20%. It was found the particle velocities are different in the upper and lower part of the cross-section in the horizontal pipe. However, the difference is generally no more than 2 m/s. The velocity difference will decrease with the increasing gas velocity, and increases with the solid mass flow rate. In the experimental condition of 0.06 mm < d_s < 0.35 mm, 1400 kg/m³ < ρ_s < 2600 kg/m³, the implicit correlation based on Yang's Unified Theory gives the best prediction of particle velocity among existing studies but still with noticeable discrepancy with the comparison of the present experimental data. By modifying the solid friction factor, an improved correlation of the particle velocity was obtained, which agrees better with the experimental data given in the present and literature studies.     

离散单元法及其在流态化领域的应用

经过三十余年的发展,离散单元法（discrete element method,DEM）已经发展成为一种广泛应用于过程工程领域中颗粒体系研究的数值方法,特别是将DEM与计算流体力学（computational fluid dynamics,CFD）相结合形成的CFD-DEM耦合方法,已经在流态化研究领域得到广泛应用。首先对DEM模型进行了综述,包括DEM模型的基本原理、颗粒形状模型、接触力模型、非接触力模型、流体作用力模型等;然后对CFD-DEM耦合方法及其在流态化领域的一些主要应用进行了介绍,包括在流化床、气力输送以及过程工程领域里的一些其他应用。最后对DEM模型以及CFD-DEM耦合方法的发展趋势进行了预测,希望能促进DEM方法的发展,并推动其在过程工程领域中的应用。     

Large-scale discrete element modeling in pneumatic conveying

Discrete element method (DEM) is an effective approach to evaluate granular flows, whereas it is hardly used in investigating the design and the operational conditions in industries. This is due to the fact that the number of calculated particles is restricted by the limit of computer memories. In this study, a coarse grain model for large-scale DEM simulations is proposed, where a modeled particle whose size is larger than the original particle is used instead of a crowd of original particles. The coarse grain model is applied to a three-dimensional plug flow in a horizontal pipeline. The plug length, the cycle and the stationary layer area occupation are compared between the coarse grain particle system and the original particle one. The results show that the coarse grain model can simulate the original particle behavior adequately.     

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。     

气力输送中影响弯管磨损的因素及解决办法

概述了气力输送中弯管磨损的机理,详细阐述了气力输送过程中影响弯管磨损的因素,如物料的物性,输送气速,料气比,弯管的结构及形状等主要因素对气力输送过程中弯管磨损的影响.并从弯管材料和结构两方面论述了减少弯管磨损的预防办法,并建议用短半径和一端不通T型弯头代替长半径弯头.     

Experimental research of flow patterns and pressure signals in horizontal dense phase pneumatic conveying of pulverized coal

Understanding flow patterns and their variability is important for optimal design and trouble free dense phase pneumatic conveying of pulverized coal in a horizontal tube. Employing the electrical capacitance tomography (ECT), six flow patterns were identified and utilized for quantitative analysis based on the value and distribution of cross-sectional solid concentration. The dense-phase flow patterns in the horizontal tube of the pneumatic conveying system were somehow variable even when the operating conditions were unchanged. The probability calculation results suggest changing multiple flow patterns with one or two dominant flow for each of the seven sets of experimental conveying conditions and that a finite change in the dominant flow pattern would occur with an increasing superficial gas velocity. The power spectral density (PSD) function and the Hurst exponent of the pressure signals of the pulverized coal were well correlated with its flow patterns in a horizontal tube. The PSD functions and probability density functions (PDFs) of the void fraction signals from ECT are found to be related with flow patterns and can be used to quantitatively identify flow regimes. The ECT data may therefore be utilized for monitoring the flow patterns in a horizontal tube employed for pneumatic conveying of pulverized coal.     

Boundary element prediction of the free surface shape between two particle plugs in a horizontal pneumatic transport pipeline

A method is presented to predict the shape of the gas-particle interface between two plugs of cohesionless particles conveyed pneumatically through a horizontal pipeline. The method assumes that the moving solids are limiting equilibrium at the interface and that, therefore, the interfacial slope depends on the normal pressure gradient which can be used as a boundary condition for the numerical solution of Laplace's equation. The height of stationary material between the plugs cannot be predicted by the method, since this material is not in a state of limiting equilibrium. However, an analogy with a gas-liquid system can be used to predict this height. The method as presented is restricted to plugs of constant voidage and to systems which obey Darcy's law (packed bed Reynolds numbers less than 10). The boundary element numerical technique is used to apply the method to a 2-dimensional example of flow through a 50 mm I.D. pipe. The predictions are qualitatively in agreement with photographs of the observed shape in the true (3-dimensional) situation. However, further numerical and experimental work on the 3-D situation is required for a full assessment of the proposed method.     

Prediction of particle charging in a dilute pneumatic conveying system

When particles are transported in pipelines, they acquire electrostatic charges as they come into contact with the pipe wall. Charged particles can cause problems such as particle agglomeration, blockage, and explosion. Understanding the particle charge can help to prevent these issues. This study investigates a technique for predicting the particle charge in a straight pipe of any given length, as well as the pipe length at which electrostatic equilibrium occurs, through experimentation in a short 1‐m pipe section. Experimentation with five different types of particles and four pipe wall materials at longer pipe lengths were used to validate the technique. This predictive technique is applicable to a range of particle shapes and sizes under the restriction that charge transfer is due to impact charging. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2308–2316, 2013     

Signal modelling and algorithms for parameter estimation in pneumatic conveying

Capacitive measurement principles offer a non-invasive approach to determine particle velocity as well as particle concentration in pneumatic conveying. In order to assess the quality of a reconstruction method, it is mandatory to know the prevailing velocity and concentration profiles. For particulate bulk solids transportation, accurate reference systems are either not available or very expensive. Based on measurement data, a signal model of the particle flow is developed for dilute phase and dense phase conveying. These models are used to demonstrate the applicability of proposed algorithms for parameter determination — a cross-correlation technique for dilute phase and a two-step approach using the Fourier transform for dense phase.     

Discrete particle modeling of lateral jets into a packed bed and micromechanical analysis of the stability of raceways

Gas jets are often used to promote heat and mass transfer by forming raceways or circulating regions in a packed bed. Such an operation is common and critical in many processes. Multiple raceways can interact and be affected by the formation of different flow zones. This work develops a multiscale model to examine the formation and the stability of raceways and the underlying micromechanics. Four states are observed in the fluidized flow regime. More fundamentally, a critical bed width for the observation of different flow zones and states is found through numerical simulations and a theoretical analysis. Finally, the complicated transitions between different flow states are examined at a bed scale, and two general trends of the averaged solid velocity are found. The findings from the multiscale model are useful both scientifically for the understanding of state transitions and practically for the design and the operation of relevant chemical reactors. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4240–4250, 2016     

Conditions of dust sampling in pneumatic conveying through the horizontal pipeline

The paper presents the results of examinations on the reciprocal relation between the isokinetic coefficient H of sampling, the quantity of measured mass concentration and the measuring usefulness of a dust sample aspired from the stream of solgas conveyed pneumatically in the horizontal pipeline. In gravimetric measurements of two-phase flows, the conditions under which aspiration is carried out, are extremely important. Available theoretical considerations and practical experiments usually concern aspiration in the vertical channels, where the manner of making measurements is universally known and it does not express any reservations. However, it is often necessary to conduct tests in the systems of horizontal conveying of solgas, where the conditions of taking a representative sample, even for the sake of the significant effect of the gravitational force, may vary from those suggested for measurements in the systems of vertical flow. The present paper also presents results of research on the selection of the isokinetic coefficient H in the case of aspiration in the horizontal channels. By means of a comparative experiment, one has found that the isokinetic coefficient, at which the results of the determined flow parameters are representative, has the optimal value of H = 1.05-1.09. The tests were conducted at the research station. In measurements the gravimetric method was applied to taking a representative sample. Dust samples were quantitatively analyzed by means of a grain-size laser analyzer. The tested dust was shale coal.     

电石生产气力输送系统氮气回收技术的研究与应用

针对现有电石炉除尘灰气力输送过程中,因氮气压力不足而造成设备及管线的堵塞,导致气力输送系统氮气回收效率降低的问题,改造设计了氮气闭路循环系统,使得氮气输送循环用气量满足现有工艺的同时,也满足了预计折损指标,达到设计要求,使气力输送系统运行率达到90%以上,实现了生产闭环。     

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.     

炭黑双管气力输送系统常见故障分析及改进

介绍了炭黑双管气力输送系统在生产过程中出现的故障和处理方法，并对一些重要改进作了总结。