水平90°弯管内盐泥浆输送压力损失研究

为得到盐泥浆在水平弯管内输送过程中的压力分布规律，探究管道直径、输送速度、输送浓度对压力损失的影响，对盐泥浆在水平弯管内的流动状态进行三维数值模拟，采用仿真与实验相结合的方式，分析了管道直径、输送浓度和输送速度对弯管段压降的影响。结果表明：弯管段压力损失随着管道直径的增大而减小，随着浆体流速的增加而增大，随着输送浓度增加而增大。设计正交实验发现各因素对弯管段压力损失影响大小顺序为：管道直径>输送速度>输送浓度。     

气力输送分支管分流处局部阻力特性分析

在上引式流态化气力输送试验台上,对3种不同角度分支管进行输送试验,分析管路分流处局部阻力损失的变化规律,并拟合分支管局部阻力特性方程;同时以试验所得参数为基础,采用fluent软件对分支管段分流情况进行数值模拟。研究结果显示,分支管局部阻力损失随管道内固气比和表观气速的增大而增大,当表观气速为8 m/s时达到了输送系统的沉积速度;误差分析表明所得拟合方程有较高准确性;模拟结果显示在管道分流处湍流现象明显并有较大的漩涡出现,且分支角度越大,湍流和漩涡现象越明显。     

连续重整催化剂提升管道设计探讨

石化连续重整装置反应部分催化剂采用含有铂的催化剂,催化剂的再生是重整装置的核心部分。催化剂提升管道为气固输送过程,输送过程的压降、催化剂和弯管的磨损是管道设计优劣的两个重要指标。结合长庆重整装置,通过分析立管、斜管和弯管处的压降,研究催化剂与弯管磨损的主要影响因素,对重整催化剂提升管管道设计提出合理建议。     

基于连续方法的气固循环流化床全回路模拟及稳定性分析

相比对单个操作单元的模拟，气固循环流化床的全回路模拟能全面揭示各单元之间的联系、诊断操作突变等现象，对实际工业生产更具指导意义。本研究在连续介质模型结合颗粒动理论的框架下，对一套虚拟过程工程(VPE)的气固循环流化床装置进行了全回路模拟和稳定性分析。模拟发现了提升管中的颗粒浓度及压降发生大幅度的周期性震荡现象，两种完全不同的操作状态，即稀相输送和浓相输送，交替式地出现。为分析该现象产生的原因，考察了模型因素(主要是气固相间曳力)和操作因素(颗粒藏料量和提升管表观气速)对周期性震荡现象的影响。研究发现，将考虑非均匀结构影响的曳力替换成均匀曳力，仍不能消除周期震荡现象，其颗粒输送返回装置(Loop-seal)压头不足以保证颗粒从下降管平稳输送到提升管，而降低气速和增大藏料量都有利于颗粒循环输送的稳定性，防止“窜气”现象的发生。结合上述现象，进一步聚焦影响颗粒输送的关键点，即Loop-seal气动阀，采用引入虚拟阀门的方式提高Loop-seal输送管中的输送阻力，从而有效改进了全回路模拟的稳定性，其预测得到的提升管轴向压降分布与实验值基本吻合。     

在气力输送弯管中炭黑的输送特性分析

研究炭黑(固相颗粒)在气力输送通过弯管时,弯径比(δ)对输送弯管内压力损失和固相颗粒运动速度以及弯管内壁磨损的影响。当δ小于5时,随着δ的增大,输送弯管内压力损失减小和固相颗粒运动速度增大,弯管内壁磨损程度降低;当δ增大到5后,输送弯管内压力损失和固相颗粒运动速度以及弯管内壁磨损速率变化放缓。设计炭黑气力输送弯管时,δ在5～7范围内既可以使输送弯管内壁磨损程度和输送能耗降低,又可满足输送管道布局和工艺要求。     

换向球在粉料输送管道中的应用

粉状物料采用气力输送时,管道弯管处磨损比较严重,所以,经常需要对管道弯管处进行补焊、更换,直接影响气力输送设备的运转率。为彻底解决这一难题,我厂在对有关厂家进行考察学习的基础上,在生料、水泥输送管道转弯处采用φ600毫米换向球代替弯管。换向球的结构见图,其工作原理是当气料进入球体后,粉料首先冲击到球壁上,由于阻力较     

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。     

基于fluent不同角度弯管持液率的计算

天然气运输过程当中,由于弯管处的阻力所造成的局部能量损失,以及重力的作用,造成气体携液能力的降低,本文将通过workbench建立不同角度弯管的模型,采用龙岗集输管道001-1至001-7段的管道参数,应用fluent数值模拟,模拟得到进出口气液的体积流量,计算持液率,研究不同角度弯管对气体持液率的影响。     

多级喷动烟气脱硫工程流动及阻力特性研究

以节能降耗为目的,在多级喷动流态化烟气脱硫技术示范工程上,对其系统流动和阻力特性进行了优化研究。结果表明:入口均流装置采用布置1块竖直导流板具有明显优越性;多级喷动塔体结构,可明显降低塔体高度,使其系统负荷适应性达到40%—100%;脱硫塔一级塔体呈现中心流速高边壁流速低的规律,中心气速约10 m/s,边壁气速约6 m/s,二级塔体上部区域流速峰值明显向脱硫塔出口侧倾斜;新型伞骨栈桥快速分离装置阻力损失较小,约占系统阻力损失的23.7%;入口段阻力损失所占份额最大,约为51%,为降低能耗还需对其作进一步优化研究。     

提升管内气固流动的小波分析

对由光纤探头获得的提升管循环流化床内颗粒体积分数的瞬态信号,采用Dauchveies小波(db4)进行15层的小波分解,并计算各尺度能量分率,以研究提升管底部浓相段与顶部稀相段气固流动结构。结果表明:颗粒速度、体积分数、能量分率在径向分布都呈典型的环核结构;底部浓相段和顶部稀相段的高、中、低频能量分率基本相同,分别在10%,60%,30%左右,说明提升管内大多数的颗粒以聚团形式或密度较大的颗粒群的形式在流化床内流动。操作条件的改变对稀密段气固流动结构的影响不同:颗粒循环流率的改变对密相段的流动影响较大,而气体速度的变化对稀相段的流动影响较大。     

工业级水平管粉煤气力输送的最小压降速度和稳定性

采用压缩空气作为输送介质,在工业级水平管(内径50 mm)上开展了粉煤密相气力输送实验研究。在实验获得最小压降速度基础上,通过电容层析成像系统观察到,随着表观气速降低而存在分层流、沙丘流、移动床流以及栓塞流4种流型。不同流型压力信号的概率密度分布和功率谱密度分析表明,压力信号的波动特征与流型紧密联系;由于流动形态的变化,存在由稳定输送过渡到不稳定输送的临界气速,且该速度小于最小压降速度。     

A case of drag reduction and pressure pulsations in pneumatic conveying

Experimental pressure drop results have been obtained for dilute phase pneumatic conveying of ordinary portland cement in a 100 mm diam. horizontal pipe with a test section length of 18 m.Significant drag reduction was detected in the presence of pressure pulsations introduced into the flow by a Roots type blower. Suppression of the pressure pulsations eliminated drag reduction.Compared with steady flow condition, it was found that pressure pulsations had a stabilising influence on the flow, permitting a 32% higher solids feed rate to be obtained before the formation of a stationary bed and the onset of unstable flow.Drag reduction in the test section was obtained at the expense of an increased pressure drop in the mixing and solids acceleration zones.     

Characteristics of a hydro-filter pressure drop,liquid hold-up and liquid overflow rate

An experimental study of the effect of operating conditions on the characteristics of a hydro-filter (Marble bed scrubber) has been performed. There are stable operating regions of a hydro-filter with respect to the gas flow rate, the packed bed height and the height of an overflow pipe above the bed. The total pressure is mainly composed of the pressure drops in two sections, the packed section and the bubble section. The pressure drop in the packed section can be estimated from the correlation for a cocurrent gas-liquid upward flow packed bed given by Turpin ad Huntington.     

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。     

Comparison of flow characteristics for dilute phase pneumatic conveying for two different plastic pellets

A series of dilute phase pneumatic conveying experiments using two different types of plastic pellets has led to the determination and development of distinguishing flow characteristics. Separate experiments on polystyrene and polyolefin pellets captured pressure-drop fluctuations and values at two different measuring points—one at the lower horizontal section of the transporting pipe and another at the upper section and at two different solid-loading ratios for each material.Also, comparison and analysis of the pressure-drop fluctuations and values obtained from the experiments were carried out under the same solid-loading ratio and blower rotational speed for both materials. Basic pressure drop calculations were made to find pressure drop due to pure gas, and that due to the presence of solids using a solid friction factor. In addition, the power spectral density analysis, and the wavelet analysis were conducted for both materials to evaluate the flow characteristics.     

气力输送系统设计中的放大换算技术

资料研究表明，尽管实验台数据放大换算已被广泛地认为是气力输送系统设计中的一个十分重要的步骤，然而直至今日，还没有通用的方法使实验台数据能可靠而精确地按比例放大到全尺度系统，主要原因在于以前的放大换算技术并未考虑到弯管位置、数量，以及短管等对总压降的影响。试验台布置了由两长一短的直管段和两个弯管组成的简单实验管道，通过从两长直管段测得的压力来确定经验公式中的指数以预测由弯管和直管段引起的压降。研究结果表明，这些公式不但能够精确地预测不同位置直管段和弯管引起的压降。还能够精确地预测不同长度、管径、弯管数和分段的总管道压降．     

气－固－固循环流化床填料层中压降及细颗粒含率的轴向分布

在气－固－固循环流化床中，尺寸较大的固相（通常作为催化剂）被固定在床中形成一段填料层，较小的固相一般为细颗粒（通常用作吸附剂或热载体）被气流携带穿过填料层。本文从讨论此类流化床中气－固两相并流流过填料层时压降的数学模型入手，应用实验测得的填料段的压降，细颗粒的平均动含率及细颗粒的循环流率等实验结果，回归了数学模型中的有关参数。在此基础上，应用这一数学模型对细粉的截面平均动含率在填料层轴向的分布行为进行了研究     

复合中空热管冷凝侧传热特性

复合中空热管能够有效解决普通重力热管换热设备的酸露点腐蚀问题,在回收低温烟气（<200℃）余热领域有重要的应用。建立了复合中空热管传热实验平台,对复合中空热管冷凝侧传热特性进行了实验研究。实验所用热管管长1080mm,不锈钢材质,工作介质为甲醇;热管蒸发侧和冷凝侧分别采用电加热和水冷却方式,K型热电偶被用于测量管壁温度和冷却水进出口温度,真空压力传感器测量管内蒸气饱和压力;研究了充液率（15%≤V+≤40%）和蒸发侧热流密度（9.48kW/m2≤q≤37.91kW/m2）对冷凝侧传热特性的影响。结果表明：当充液率为20%时,复合中空热管冷凝侧均温性能最好,冷凝侧换热系数最大,传热性能最佳;随着蒸发侧热流密度的增大,复合中空热管有效冷凝长度增大,冷凝侧换热系数增大。实验研究为工业应用提供了基础。     

Solid circulation and gas bypassing characteristics in a square internally circulating fluidized bed with draft tube

The effects of gas velocities to draft tube (26.64–52.54 cm/s) and to annulus section (8.14–11.84 cm/s) on solid circulation rate and gas bypassing fractions were determined in a square internally circulating fluidized bed reactor with an orifice-type square draft tube. The solid circulation rate and gas bypassing fraction from the annulus section to the draft tube increase but gas bypassing fraction from the draft tube to the annulus section decreases with increasing gas velocity to the draft tube. With increasing gas velocity to the annulus section, the solid circulation rate and gas bypassing fraction from the draft tube to the annulus section increase but, gas bypassing fraction from the annulus section to the draft tube decreases. The solids circulation rate was correlated with the pressure drop across the orifice and the opening area ratio based on the orifice theory. The gas bypassing fraction was correlated with gas velocities to the fluidized and the moving beds. Based on the gas bypassing fraction data, the gas flow rates across the orifice were correlated with gas velocities to the fluidized and the moving beds, opening area ratio, particle size and solids height in the bed.     

Vertical pneumatic conveying of particle plugs

Dense-phase pneumatic conveying of solids offers many advantages over dilute-phase conveying. The lower air velocities, and, consequently, lower particle velocities, result in lower pipe wear and lower particle attrition. This paper describes an experimental program that has been undertaken to study the flow pattern of cohesionless solids in vertical transport and to measure the parameters influencing the pressure drop required to move a single plug of solids. Highspeed photographic techniques have been used to observe the flow pattern of polyethylene particles (diameter ? 3 mm) in the vertical riser section of a circulating unit constructed from pipes with an internal diameter of 50.8 mm. The flow pattern resembles that of square-nosed slugging in a fluidized bed. The solids move up as “plugs” of bulk solids that occupy the entire cross-section of the pipe. Particles are seen to “rain” down from the back of one plug and then to be collected by the front of the next plug. Collecting these particles causes a stress on the plug front which is transmitted by powder mechanics forces axially through the plug and radially to the wall. The pressure drop required to move a single plug of cohesionless solids through the transport pipeline was measured as a function of the plug length, particle properties, pipe diameter, and the frontal stress. The results of these experiments are compared with a theoretical model.