PVDF密相气力输送和稀相气力输送比较

随着气力输送在石化、医药、锂电、环保等行业的广泛应用,对密相气力输送和稀相气力输送的研究尤为重要。通过对聚偏氟乙烯(PVDF)稀相气力输送和密相气力输送的介绍,以及对二者输送气源品质、输送设备旋转阀和发送罐、输送气速和管径、除尘面积、设备平稳运行时间、输送气量和能耗等方面的对比,指出了PVDF密相输送工艺的优势。     

密相气力输送系统设计

密相气力输送越来越多地用于粉料的输送。以白炭黑的密相气力输送系统为例,详细描述了密相气力输送原理,以及工艺流程、发送罐容积、输送空气体积流量、输送管径、输送系统管道压力损失和除尘器过滤面积等主要参数的确定。     

管道密相脉冲气力输送装置介绍

介绍了国产 5种应用于合成纤维生产中的密相脉冲气力输送装置及其应用。其中以密相脉冲气刀式气力输送应用较广。国产密相脉冲气力输送装置已能达到同类进口装置的输送能力。     

密相气力输送工艺在PVC粉体输送上的应用优势

介绍了两种PVC粉体输送工艺——密相气力输送工艺和稀相气力输送工艺,通过两者在投资、能耗、环保以及对产品质量影响等方面的对比,指出密相气力输送工艺在PVC粉体输送上更具有优势。     

炭黑密相气力输送节能分析

从炭黑密相气力输送气源供给压力、双管输送辅助管补气方式及可调式LAVAL管等方面分析了针对炭黑密相气力输送节能的可行性以及节能空间.指出通过采用可调式LAVAL管降低气源压力和可控式辅管补气方法,可大大降低炭黑密相气力输送的空气量和能耗,降低生产成本.     

优化改造密相气力输送逻辑确保装置长周期平稳运行

大庆石化公司20万t／a高压低密度聚乙烯装置（LDPE）自开工以来,曾多次出现了密相气力输送系统输送压力低而导致的输送风机停车和因为不同的送料段同时进行吹扫而导致的系统超压停车的现象,无法保证装置的平稳运行,通过对密相气力输送逻辑的深入分析及多次的经验摸索,最终对于密相气力输送逻辑进行了优化改造,解决了密相气力输送系统输送压力低等问题,保证了装置的平稳运行。     

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。     

PVC粉料输送工艺的对比

介绍了PVC粉料稀相气力输送工艺及密相气力输送工艺,对比了两种输送方式的工艺、设备、管道及能源消耗情况。认为密相气力输送方式具有输送风量小,输送风速低、粉尘量小,除尘设备功率较小,长距离输送能耗低等优点,是未来PVC粉料输送的发展方向。     

密相气力输送技术在纯碱输送中的应用

主要介绍密相气力输送技术的特点,结合纯碱输送设计实例,将密相气力输送技术与常规机械输送进行对比,对该技术特点和应用前景做出总结。     

浅谈气力输送稀相和密相在大型乙烯装置中的应用

随着中国工业化的发展,对气力输送装置不断进行大量试验和实践,目前气力输送装置已日趋完善。我国自上世纪70年代以来兴建的大型乙烯装置,其粉粒成品几乎均采用气力输送[1],特别是近几年大型乙烯装置更如雨后春笋,新上项目林立。气力输送方式更是得到了广泛应用,但同时出现一个问题,就是大多数用户对于气力输送是采用稀相输送还是密相输送存在困惑,孰优孰劣,难以抉择,因此,本文针对大型乙烯装置中气力输送的稀相和密相模式,结合已有项目的实践经验,浅谈稀相输送和密相输送的优缺点以及如何选择。     

低速密相气力输送综述

气力输送技术的重要发展是低速密相输送装置的出现,它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,经济效益和社会效益显著,综述了低速密相输送中的相图、物料流动形态、料性对气力输送特性的影响等技术参数,介绍了开发的新型装置及其设计和今后的研究方向。     

PET切片输送系统的节能改造

介绍了密相及稀相气力输送的基本工作原理及其特点。由于PET切片产量减少,为了节约能耗,PET切片输送系统由密相输送改为稀相输送。详述了稀相输送系统计算过程及设计方案,给出了稀相输送系统在较短距离内输送PET切片的应用范例,并对改造前后的能耗进行了对比。     

改善长距离密相栓流气力输送工况的措施

随着生产规模的扩大 ,对于输送距离长、提升高度高的工艺要求 ,密相栓流气力输送技术显示出其输送能力不足的一面。在输送途中的合适位置加设补气助推器与压力控制单元 ,以此为界 ,使物料在前段保持脉冲栓流形态输送 ,在后段则以流态化输送。这一改善工况的措施已获成功 ,使密相栓流气力输送能适应于长距离输送的工艺要求 ,扩大了使用范围。     

Coupled DEM‐CFD Simulation of Pneumatically Conveyed Granular Media

A DEM‐CFD coupling for the simulation of gas‐solid flows was successfully implemented and simulations were performed for the application to industrial‐scale pneumatic conveying. Therefore, all particle collisions and phase interactions were considered and porosity determination was optimized. The aim of this work is to show the applicability of the presented simulation model to the different regimes of pneumatic conveying systems. As a first test case a dense vertical pneumatic conveying system was chosen and an individual plug was investigated in detail. Variations of the conveying air velocity were also considered. As a second test case dilute conveying in a horizontal‐to‐vertical pipe bend was simulated. The occurrence of roping and the reduction of particle velocity is of high interest for the design of specific pneumatic systems. It is shown that both regimes can be captured reasonably well and the results are rich in details.     

表观气速对密相气力输送流型影响的模拟研究

针对目前密相气力输送数值模拟关于流型演变方面所存在的问题,提出了一种基于颗粒所在局部空间的固相浓度及颗粒群运动特征来描述颗粒间相互作用的数学模型。该模型能够对气力输送,甚至是颗粒发生大量堆积情况下的密相输送进行数值模拟,使得长期以来缺乏有效模型对密相输送流型进行数值模拟研究的问题得到一定解决。利用该模型,对水平管中煤粉高压密相气力输送的颗粒流动过程进行了数值模拟,获得了输送过程中管道内所发生的气固两相之间的分离、沉积现象,展现了沙丘流及栓塞流等流型的演变特征,模拟结果与实验观察到的现象吻合较好,从而进一步验证了新数学模型的有效性。此外,通过对不同表观气速下固相流态分布的定量分析,揭示了输送流型变化的一些内在规律。     

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.     

Friction measurement in dense phase plug flow analysis

Pneumatic conveying, employing the dense phase plug flow regimen, is largely used to transport bulk solids. This process permits the conveying of large amounts of material in economical manner with less particle and pipe degradation compared to dilute phase conveying. By using an experimental system with special measurement devices and different materials of construction and transport, the friction between the material being transported and the pipe wall, the actual motion of the particles was determined, and the degree of fluidization were estimated. This information permits more accurate modeling of dense phase plug flow providing basic parameters to insert in existing and developing models.     

负压差立管下料过程压力脉动的传递性实验与分析

在高13m大型循环流化床装置上,对φ150 mm×900 mm负压差立管内气固两相流的动态压力进行了轴向多点测量,并用标准偏差进行了分析,主要研究立管下料过程的动态传递特性.实验表明负压差立管内存在明显的压力脉动现象,这种压力脉动具有一定的传递性.颗粒质量流率比较小时是稀密两相共存流态,稀相区的压力脉动主要受进料流量振荡的影响,向下传递;密相区的压力脉动主要受立管的波动性排料影响,向上传递;随着颗粒质量流率的增加达到浓相输送流态时,上部是连续式浓相输送流态,下部是密相波浪式输送流态,立管的压力脉动主要受进口流量振荡和排料过程压缩气体作用,向下传递.对立管的压力脉动进行标准偏差分析表明脉动压力传递沿颗粒的流动方向上具有幅值增大特性.在立管内流态从稀密两相共存流态转变为浓相输送流态时,由于颗粒压缩气体分量最大,压力脉动幅值最大,减小或增加颗粒质量流率,压力脉动幅度均降低.     

Vertical pneumatic conveying: a flow regime diagram and a review of choking versus non-choking systems

For vertical pneumatic conveying of granular solids, a flow chart describing two different types of gas—solid systems, viz. the choking system and the non-choking system, is presented. Published equations for the prediction of whether a particular gas—solid tube system is of the choking type or non-choking type are reviewed. For the choking type system, a quantitative flow regime diagram for predicting demarcation between packed bed conveying and slugging dense phase conveying, and demarcation between slugging dense phase conveying and lean phase conveying, is developed in terms of the key parameters of loading ratio, gas and solid velocities. The usefulnes of the flow regime diagram in design is discussed. The shortcomings of an earlier flow regime diagram proposed by Leung [14] are overcome in the present diagram.     

Analysis of Regime Transitions and Flow Instabilities in Vertical Conveying of Coarse Particles Using Different Solids Feeding Systems

The transition between dense and dilute flow in vertical conveying of Geldart D particles were investigated for risers of different diameters using a spouted bed as a solid feeding system. The transition and choking velocities were identified by combining analyses of pressure gradient versus air velocity diagrams, pressure fluctuation signals and voidage values. Experimental data were used to evaluate the effect of particle and riser diameters on the pressure gradient, mean mixture voidage, the regime transition and choking velocities. The transition velocity from dilute to dense phase could be identified, as well as the onset of the choking condition, which appeared as the air velocity was further reduced. Data obtained in the same experimental apparatus facility using a screw conveyor and a gravitational system as solid feeding devices have been used as a reference to be compared to those obtained using the spouted bed feeder.