螺旋并联分配管对旋风分离器分离性能的影响

为兼顾高分离精度及大处理量的要求,微小型旋风分离器并联得到越来越多应用。运用离散相模型和实验研究了螺旋并联分配管对旋风分离器分离性能的影响,分析了螺旋分配管分级和改变"序态"特性。结果表明,大颗粒易于从分配管前端出口逸出,依次进入旋风分离器固体颗粒呈现不同粒径分布,总体呈现分级特性;螺旋管对细颗粒物具有改变"序态"作用,进入旋风分离器颗粒粒径呈现外小内大趋势,内部相比外部颗粒浓度更高;内侧大颗粒构成的粒子环促进细小颗粒的去除,从而提高旋风分离器分离效率。实验进一步验证螺旋分配管分级和改变"序态"特性。研究结果对微小型旋风分离器并联设计具有指导意义。     

差异旋风分离器并联性能测量及流场分析

通过改变旋向和芯管直径,设计了3种差异旋风分离器,并按中心对称方式组成了3种并联方案：相同分离器、旋向差异分离器和芯管差异分离器并联。在冷态实验装置上,测量了单分离器和并联分离器的性能,并利用FLUENT软件分析了并联分离器的流场。结果表明,并联分离器的效率均高于单分离器,且效率-气速曲线未出现“驼峰”;与相同分离器并联相比,旋向交替变化时并联总压降较小,分离效率也更低,但各分离器流量分配均匀,未发现“窜流”现象;当芯管有差异时,并联总压降增大,各分离器进口流量分配不均匀,且进、出口流量平均相差6.0%,公共灰斗中存在“窜流”,旋流稳定性变差,效率降低。为了保证并联分离器的性能,应采用相同分离器对称并联的方式。     

天然气净化用多管旋风分离器的分离性能

为了系统评价天然气净化用多管旋风分离器的分离性能,在线测量了入口气速6~24 m/s、入口颗粒浓度30~2000 mg/m3范围内多管旋风分离器的分离效率和分级效率. 结果表明,多管旋风分离器的分离效率和分级效率都随入口气速和入口颗粒浓度增大而提高. 与单管旋风分离器相比,在相同实验条件下,多管旋风分离器的分离效率下降2%~15%;单管旋风分离器基本能除净粒径大于10 mm的颗粒,而多管旋风分离器只能去除15 mm以上的颗粒. 多管旋风分离器的压降主要是内部单管旋风分离器的压降,占整个压降的80%~90%.     

不同数量并联微旋风分离器分离性能影响研究

为了考察不同并联旋风分离器的分离性能,运用计算流体力学(CFD)软件对由不同数量、直径为30mm的微旋风元件构成的并联分离器性能特征进行了数值研究。结果表明,当微旋风元件入口气速一致时,增加微旋风元件数量,虽然各并联分离器对5μm以下、中位粒径3.5μm颗粒的总分离效率基本相同,但对3μm以下颗粒的分级效率有所下降;组合分离器灰斗中排尘管间间距减小,微旋风元件内切向速度分布几乎不变,中心轴向速度下降,排尘管尾端气流更加紊乱;随着微旋风元件数量增加,各组合分离器微旋风元件排尘管段旋流稳定性系数S_v沿轴向逐渐增大,微旋风元件内旋流稳定性变差。     

差异旋风分离器并联性能测量及流场分析

通过改变旋向和芯管直径,设计了3种差异旋风分离器,并按中心对称方式组成了3种并联方案:相同分离器、旋向差异分离器和芯管差异分离器并联。在冷态实验装置上,测量了单分离器和并联分离器的性能,并利用FLUENT软件分析了并联分离器的流场。结果表明,并联分离器的效率均高于单分离器,且效率-气速曲线未出现"驼峰";与相同分离器并联相比,旋向交替变化时并联总压降较小,分离效率也更低,但各分离器流量分配均匀,未发现"窜流"现象;当芯管有差异时,并联总压降增大,各分离器进口流量分配不均匀,且进、出口流量平均相差6.0%,公共灰斗中存在"窜流",旋流稳定性变差,效率降低。为了保证并联分离器的性能,应采用相同分离器对称并联的方式。     

高入口浓度下PV型旋风分离器的分离效率计算

基于Muschelknautz 分离模型,以PV型旋风分离器为对象,针对高入口浓度的分离效率的计算,将旋风分离器分离空间的气固分离过程划分为2个区域,提出了串级分离模型。当入口浓度大于临界入口浓度时,旋风分离器内有器壁附近的颗粒支配区和中心区域的气体支配区。颗粒支配区内颗粒速度大于气体速度,颗粒夹带气体沿器壁螺旋下行进入灰斗被全部捕集,形成了颗粒的一级分离;气体支配区内气体速度大于颗粒速度,气体携带颗粒做旋转运动进行离心分离过程,形成了颗粒的二级分离。旋风分离器总的气固分离过程是一级分离和二级分离的叠加。通过高入口浓度的实验对串级分离模型进行了验证,基于串级分离模型给出的PV型旋风分离器的分离效率与实测值较吻合。研究表明旋风分离器临界入口浓度对总效率的计算影响较大。串级分离计算模型包含了结构参数和气、固相物性等参数,具有很好的通用性,可以满足PV型旋风分离器的工程计算和设计要求。     

输气站场多管旋风分离器流场分析

为了系统评价输气站场用多管导叶式旋风分离器的分离性能,模拟计算了入口速度7~27 m/s、颗粒密度1000~5000 kg/m3、颗粒浓度2.5~2500 g/m3、操作压力1~5 MPa条件下21管旋风分离器的分离效率和压降. 结果表明,多管旋风分离器的压降主要来自单管压降,约占整个压降的80%~90%,旋风子单独使用和并联使用时其流场分布规律相同,沿轴向对称分布,中心涡核处压力最低;分离效率和压降均随入口速度增大而增加,粒径为1~10 mm的固体颗粒分离效率从30.57%增加到63.86%,压降从9053 Pa增加到116864 Pa,在入口速度7~27 m/s范围内基本能除尽粒径大于6 mm的颗粒;随颗粒密度增加,分离效率增大,压降几乎不变;操作压力增大分离效率降低,而压降略增加. 各单管间进气量波动均不超过5%.     

并联旋风分离器分离性能的实验研究

针对催化裂化三旋多管式旋风分离器存在的整体效率偏低的问题,文章开展旋风分离器并联结构优化的尝试,采用实验的方法研究4台切流式PV型旋风分离器并联后的分离性能。结果表明,并联旋风分离器的分离性能要高于单台旋风分离器,但仍存在着继续改进的空间。     

反应器结构对多段气化炉内颗粒分布的影响

针对多段气化炉(上部快速床、下部鼓泡床),采用MP-PIC(Multi-Phase Particle In Cell)方法模拟了多粒径煤粉颗粒的三维全循环流化过程,考察了鼓泡床与快速床床径比及鼓泡床和快速床之间的过渡段高度对气化炉内流动特性的影响。结果表明,基本工况下,大颗粒主要存在于下部鼓泡床中,细颗粒主要存在于上部快速床内,但细颗粒会通过旋风分离器和回料管再次进入鼓泡床参与循环。进入旋风分离器的大部分为半径622 ?m以下的小颗粒,无1216 ?m以上的大颗粒。旋风分离器对小颗粒的分离效率为99.75%,分离效率良好。增大床径比(即减小快速床直径),快速床中气速增大,整个气化床更快达到稳定状态,被夹带到快速床中的颗粒增多,所夹带的颗粒粒径增大。过渡段高度存在一个适当值(炉高0.6~1.0 m),升高或降低过渡段高度,快速床中颗粒浓度均增大,颗粒通量均升高,旋风分离效率降低。     

旋风分离器防磨减阻性能机理研究

为了提高旋风分离器的防磨减阻性能,运用计算流体动力学方法研究了常规和防磨减阻旋风分离器的防磨减阻机理。结果表明:常规旋风分离器容易发生严重的局部冲蚀,而防磨减阻旋风分离器冲蚀磨损区域较为均匀。在同一粒径下,防磨减阻旋风分离器的壁面冲蚀磨损远小于常规旋风分离器。两者的壁面冲蚀磨损速率随粒径增大而逐渐增大,当粒径大于15μm时,冲蚀磨损速率变化不大。两者的压降损失随着入口速度的增加而增大,当入口速度为15 m/s时,防磨减阻旋风分离器的压降为297 Pa远小于常规旋风分离器的821 Pa。防磨减阻板不会改变旋风分离器的流场特性,分离小粒径颗粒效率略小于常规旋风分离器,但粒径大于5μm时,防磨减阻旋风分离器具有很高的分离效率。     

重介质微型旋流器内切向速度的数值模拟

重介质旋流器在选煤领域中已得到广泛应用。根据硅和碳化硅等不同密度微细颗粒易团聚且难用化学方法分离的特点,本文选用重介质微型旋流器对其进行分离。为探索重介质微型旋流器的流场特性,本文基于CFD软件Fluent对重介质微型旋流器的切向速度场进行了数值模拟研究,考察了介质的密度及黏度对旋流器内切向速度的影响。结果显示,密度不变,黏度增大,切向速度减小,且旋流器直径越小,切向速度减小越快,即旋流强度衰减得越快。虽然黏度不变时密度的增大会导致切向速度的增加,但当密度和黏度按实际重介质溶液同时增大时,黏度对切向速度的影响远大于密度的影响。     

Development of mini-cyclones as the size-selective inlet of miniature particle detectors

The recent development of miniature particle detectors stems from the demanding need to monitor/measure particles, especially nanoparticles, at the personal level for epidemiological studies or studies investigating the interaction among genes and environmental factors, including particulates. Light scattering and electrical mobility techniques have been implemented in these mini-devices for monitoring submicron particles. The presence of large particles in the sampling stream, however, affects the performance of these mini-detectors. Prototype mini-cyclones were thus developed as a size selective inlet for mini-particle detectors. In this study two “quarter-sized” mini-cyclones were designed to remove particles larger than 1.0 and 0.3 μm at a flow rate of 0.3 lpm, and their performance was experimentally evaluated. The performance of prototypes was also compared with that of existing personal sampling cyclones. Further, empirical models to estimate the performance of the prototype mini-cyclones (i.e., the 50% cutoff particle size and pressure drop) were also established. The developed linear regression model can thus serve as the tool for the future design of mini-cyclones with the similar size and configuration.     

A Mathematical Model to Compare the Efficiency of Cyclones

Tangential cyclones modified to form spiral cyclones are very efficient in separating solid particles from dust laden gases. They offer a lower gas pressure drop and higher particle separation efficiency when compared to basic tangential cyclones. Their high performance is believed to be related to their special structure. A mathematical model is introduced to explain why a spiral cyclone is more efficient than a tangential one. An experimental apparatus is designed to compare both the performances of spiral and tangential cyclones and to check the effectiveness of the model equations. The experimental data were found to be consistent with the model predictions.     

入口抽滤预团聚提高旋风分离器性能试验研究

分析了旋风分离器对细粉捕集效率低的原因,并提出了对传统旋风分离器的改进方案,即将传统旋风分离器的排气芯管改进为一个过滤筒,并在滤筒内部加装转动清灰刷,这样的设计充分利用了旋风分离器和过滤除尘器各自的优点,使过滤除尘和旋风除尘有机结合在一起,节约了设备空间,提高了其综合性能,实验结果表明除尘总效率一般都在99.94%以上,完全除去了1.6μm以上的细粉尘。     

Multi-object optimization study on the performance of gas cyclones based on heterogeneous condensation and turbulent agglomeration

Improving the separation efficiency of fine particles becomes more and more critical as environmental pollution aggravates. This study aims to investigate the effects of four key parameters on the performance of gas cyclones, including cyclone body height, particle concentration, initial supersaturation degree, and inlet temperature. Then, the two-way coupling numerical model, in which is the process of heterogeneous condensation and agglomeration for insoluble fine particles, was achieved by user defined function. On this basis, the response surface analysis method and multi-objective genetic algorithm were adopted to optimize the cyclone. The results show that when the particle concentration is less than 1000 mg/m³, the separation efficiency can reach above 95%. The initial supersaturation degree has the greatest effect on the separation efficiency and vapour consumption rate, while the cyclone body height is the most critical factor on the pressure drop. As the particle concentration increases, the separation efficiency decreases at first and then keeps almost stable. With the increase of inlet temperature, the separation efficiency is enhanced, and the pressure drop reduces. These research results can provide important guidance for the optimization and engineering application of this technology.     

流场形态对旋风分级器性能的影响

气流分级器性能的优劣很大程度上取决于流场分布,改变常规旋风分级器的切向进风口位置,在分级空间建立不同类型的离心流场,采用数值模拟和分级试验手段分析了分级流场形态对颗粒运动过程和分级性能的影响。结果表明,传统旋风分级器边壁下行流造成粗粉中细颗粒夹带较多,影响分级精度;新型旋风分级器内形成上下两个旋涡,上旋涡均为上行气流,其流量约占总风量的80%,下旋涡携带细颗粒较少,降低了细颗粒进入粗组分的概率;上旋涡可实现对边壁区的细颗粒的轴向淘洗、再分级,提高了分级精度。试验结果表明,入口气速从10m/s增加至22m/s。相较于传统旋风分级器,新型旋风分级器的分级性能明显改善,分级精度指标平均提高27%,压降损失为传统旋风分级器的53%~62%。     

Effect of inlet particle arrangement on separating property of a cyclone separator

Different arrangements of particles on the inlet section exert different effects on the separation property of a cyclone separator. Sorting classifier with different heights was connected in series with a conventional cyclone, positive rotation cyclone, and reverse rotation cyclone respectively, to investigate the effect of particle arrangement on the separation property and inner flow field. Results indicate that the implementation of a sorting classifier increases the pressure drop and energy consumption of a cyclone separator. The taller the sorting classifier, the larger the flow is. The energy consumption in positive rotation cyclone is closer to that in reverse rotation cyclone. Meanwhile, the tangential velocity in inner flow field is higher and the separating property is enhanced. The reverse rotation cyclone relieves the fishhook effect, whereas the positive rotation cyclone eliminates such effect. The reverse and positive rotation cyclones demonstrate an improved separating property for particles smaller and greater than 1 μm, respectively. Moreover, the reverse rotation cyclone demonstrates superior overall separation, but the positive rotation cyclone demonstrates a greater classification effect than the reverse rotation cyclone.     

Simulation study of production of fine ceramic powders in a cyclone reactor

A numerical simulation study of production of fine ceramic powders in an innovative vapor-phase aerosol reactor is described. Arrangement is typical of reverse-flow cyclone equipment; no similar device is present in current scientific literature and industrial technology. The cyclone reactor has a potential technological application as it realizes process intensification by two simultaneous operating advantages: (i) curly flow reduces recirculation of as-synthesized particles towards flame region, and (ii) cyclone arrangement segregates large particles. As a result, ceramic powders with narrower particle size distribution can be produced with regard to traditional equipment. The study is based on the re-modeling of an existing industrial reactor for production of fine TiO₂ according to a cyclone configuration; particle size distributions from simulation and plant are compared.     

中心棒对石膏旋流器工作性能的影响

针对火电厂石膏旋流器运行中存在空气柱及底流夹细等问题,设计倒锥形中心棒取消空气柱,改善石膏旋流器的工作性能。采用实验方法分析不同入口压强下石膏旋流器性能的变化情况,得到无中心棒、圆柱形中心棒、倒锥形中心棒对生产能力、底流浓度、底流含固量以及底流浆液中石膏颗粒分布的影响。结果表明：与无中心棒相比,采用倒锥形中心棒能够使生产能力提高18%,底流含固量增大22%,分级性能对入口压强具有良好的适应性,并能够有效缓解底流夹细现象。     

并联旋风分离器的旋流稳定性分析

分别选用2台和4台直径300 mm的相同PV型旋风分离器作为分离元件,共用进气管、集气室和排尘室,以中心对称方式组成两种并联分离器,并通过数值模拟比较单分离器与两种并联方案中各分离元件气相流动的特点. 气体介质为常温常压空气,入口气速15~30 m/s. 结果表明,2台或4台并联时各分离元件流量偏差分别不超过0.35%和0.28%,压降最大偏差为0.79%和0.43%,流量分配均匀,灰斗内窜流返混不明显,且4台并联时效果更好. 4台并联时分离元件排尘段的稳定性指数比2台并联或单分离器降低过半,旋流稳定性显著增强. 对称排列的分离元件在公共灰斗中会形成具有自稳定性的对称涡系,对分离元件内旋进涡核的摆动有约束作用,旋流稳定性增强.