孔盘式液体分布器内液体流动对布液孔出流均匀性的影响

借助包括双欧拉均相多相流模型、VOF界面追踪方法和SST k-ω湍流模型的CFD模型,对孔盘式液体分布器内的流场对布液孔出流均匀性的影响进行研究。首先以单孔流动时的液体流量为标准值,通过与标准值的偏差来评估布液孔的出流不均。根据偏差的大小,可以衡量分布器内流动对布液孔出流的影响。然后结合孔前流动区概念对模拟结果进行分析,发现布液孔出流不均是由分布器内液体流动不均造成的。最后,提出了通过改变进料管位置来优化盘式液体分布器结构。计算结果表明,改变进料管的位置可以避免大规模不良分布,进而提高液体分布器的性能。     

孔流型液体分布器二级槽内的流场分析

为了研究底孔型液体分布器二级槽中的流动特性和考察挡板与液位两种因素对性能的影响,采用数值模拟方法,通过SST湍流模型和VOF多相流模型获得槽内的气液两相流场,分析了不同液位下挡板对底孔流量均匀性的影响。结果表明：低液位时槽底附近有明显的横向流动,挡板可以抑制这种横向流并将入口射流带进的湍流扰动移向液面。高液位时槽底横向流不明显,但射流点附近液面以下有大尺度涡流,挡板顶部绕流使相应区域产生速度波动并沿高度方向衰减。液位无论高低,设置挡板都使槽底横向流被阻滞,挡板对不同位置孔附近流场的改变方式不同,射流落点位置和板后回流涡形态的改变造成流经孔口上方介质中进入孔内的比例和孔内流速的改变,共同影响孔内流量的变化。挡板使底孔流量均匀性有所下降,主要原因是射流点下游底孔附近射流和涡流的不良分布,而较高的液位由于增加了对射流、横向流和挡板扰流的惯性和黏性阻滞,可以改善底孔流量均匀性。     

规整填料塔中精馏过程的三维模拟(Ⅱ)模型的验证及液相分布和混合行为对精馏过程的影响

用简化三维混合池模型对Gorak所做精馏实验作了实例计算。模型的计算结果与Gorak实验数据符合良好,以简化三维混合池模型为工具,用数值计算的方法研究了规整填料塔中液体流动分布和混合对精馏过程的影响。结果表明：液相轴向返混对精馏有着显著的不利影响;当液体流动分布为严重壁流分布（严重沟流分布）时,必须用三维模型描述才不会产生较大偏差;横向混合系数的增大有利于填料塔分离效率的提高,但不能完全抵消液相严重不均匀分布对精馏过程的不利影响。     

填料塔液体分布器的研究进展

填料塔作为化工单元操作过程中重要的汽液传质设备,因具有传质效率高、整塔压降低、能耗低等优点,已经成为精馏操作中的关键设备。液体分布器是填料塔中重要的塔内件,其结构形式直接关系到液相物料在塔内的分布情况,从而影响填料塔的分离效果。本文系统介绍了液体分布器的发展现状,从自然流分布、径向分布系数等方面详细总结了分布质量对填料塔分离效率的影响;深入分析了国内外关于各种结构类型的液体分布器的理论研究以及设计优化过程;并总结了不同液体分布器分布质量评价方法的适用场景。文章最后对液体分布器的发展进行了展望,为液体分布器的设计与优化提供了思路。     

海上天然气脱酸塔内排管式液体分布器各喷淋密度下的孔径研究

近年来,海上浮式液化天然气设备成为研究热点,液体分布器作为脱酸塔器中关键的塔内件之一,目前对其在海上晃动工况下的结构设计研究较少。本文选取出口数为52个的1.2m排管式液体分布器作为研究对象,利用晃动平台和水循环系统组成的实验装置,对液体分布器开展静止、横摇5°和纵摇5°的水力学实验,通过改变喷淋密度,分析在晃动工况中,具有不同出口直径的排管式液体分布器各支管孔口流量分布和整体孔口流量分布的变化情况,结合孔口流速的合理范围以及孔口流量不均匀度较静止工况下的增大程度,确定出晃动时在各种喷淋密度条件下最优的孔口直径。结果表明:排管式液体分布器在小尺寸孔径下受晃动的影响程度更小,但是出口流速较大;晃动5°以内的条件下,喷淋密度分别为4.4m~3/(m~2·h)、8.8m~3/(m~2·h)和13.2m~3/(m~2·h)左右时,孔径分别设计为4mm、6mm和8mm可以使排管式液体分布器的孔口流速落在合理范围内并且维持较高的孔口流量均布性能。     

白钨矿连续酸浸槽内固体颗粒的流动特性实验及模型研究

以停留时间分布（RTD）为评价指标,对硫磷混酸浸出白钨矿的连续浸出槽内固相颗粒流动行为进行实验研究。同时探究了进料流量、搅拌转速、连续浸出槽中物料进出口位置组合对固相颗粒流动行为的影响。实验结果表明：随着进口流量的增大,一开始槽内的返混程度得到了增强,量纲为1化方差变大,但是继续增大进口流量,进口处物料的横向迁移速度加强,使槽内流体流动趋向平推流,导致量纲为1化方差减小;量纲为1化方差随着搅拌转速的增大而增大,但是此时在槽下部区域会逐渐形成循环死区,槽内死区体积分数随之增大;平均停留时间随着物料进出口位置的变化而发生变化,下进下出的进出料位置组合其平均停留时间最大,且最接近理论平均停留时间。最后利用非理想流动模型来表征实验过程中的停留时间分布,模型拟合的停留时间曲线与实验测量的曲线吻合程度良好。     

新型管槽式吸收塔液体分布器的研制及性能测试

针对气体吸收分离中常见的吸收塔管式、槽式分布器液体分布不均匀的问题,开发出一种新型的管槽式液体分布器,并搭建直径1.2 m的吸收塔实验平台,对不同气相进料风速、不同喷淋密度下管式、槽式及管槽式分布器的液体分布情况和整塔压降,以及壁流效应进行了实验测定。实验结果表明:风速对分布器的液态分布性能没有太大的影响。随着喷淋密度的增大,新型管槽式液体分布器的不均匀系数逐渐下降,最大喷淋密度[L=6.99m3/(m2·h)]时其值接近0,相对于管式和槽式分布器分别下降6%和11%。不同风速下,管槽式分布器相对于管式、槽式分布器的整塔压降最高分别降低24%和16%;而且管槽式分布器壁流效应比管式与槽式的更不明显。最后,针对实验中管槽式分布器出现的问题,进行了分析并提出进一步优化的方案。对于在工业生产中喷淋密度大都大于实验时的喷淋密度,新型管槽式分布器将有更优异的表现,具有很好的规模化应用前景。     

固-液导流筒搅拌槽内流体流动和颗粒悬浮特性

在直径0.8 m的导流筒搅拌槽内,对单相液体的三维速度分布、固-液两相的固体颗粒浓度分布和离底悬浮特性进行了系统的实验研究. 结果表明,导流筒内外的轴向液相速度远大于径向和切向速度,导流筒外壁附近存在一个与主体轴向流动方向相反的二次流区域;搅拌槽底部结构对固体颗粒的临界离底悬浮转速(NJS)有显著的影响,浅锥底的NJS比平底的低14%以上;NJS随固相浓度的增加而增加,但当浓度超过50%时,NJS略有降低;槽内固相浓度分布的均匀性随固相浓度的增加而得到改善. 本研究结果对导流筒搅拌槽的优化设计具有一定的指导意义.     

槽式液体分布器分布性能的研究

文中以大型的工业用槽式液体分布器为研究对象,研究方法有理论计算、实验和流体模拟软件模拟。研究发现:传统的槽式液体分布器其分布孔的设计存在偏差,分布器分布管出口流量、一级槽自身液面稳定能力以及液面梯度都对分布器的分布性能有影响。文中提出了一种新型槽式液体分布器,有利于提高填料塔的效率。     

固-液导流简搅拌槽内流体流动和颗粒悬浮特性

在直径0．8m的导流筒搅拌槽内，对单相液体的三维速度分布、固-液两相的固体颗粒浓度分布和离底悬浮特性进行了系统的实验研究．结果表明，导流筒内外的轴向液相速度远大于径向和切向速度，导流筒外壁附近存在一个与主体轴向流动方向相反的二次流区域；搅拌槽底部结构对固体颗粒的临界离底悬浮转速（NJS）有显著的影响，浅锥底的NJS比平底的低14％以上；NJS随固相浓度的增加而增加，但当浓度超过50％时，NJS略有降低；槽内固相浓度分布的均匀性随固相浓度的增加而得到改善．本研究结果对导流筒搅拌槽的优化设计具有一定的指导意义．     

Simulation of Orifice Flow Influenced by Lateral Flow in a Trough‐Type Liquid Distributor

A computational fluid dynamics (CFD) simulation is performed to investigate the influence of lateral flow on the orifice flow in a trough‐type liquid distributor. The discharge coefficients from the simulation are in good agreement with the experimental values, indicating that the CFD simulation is accurate in describing the outflow through orifices. The lateral flow near an orifice can change the velocity and pressure distributions of flow regions in front of this orifice, causing a decrease in the discharge coefficient. This phenomenon is supported by the theory of flow past a blunt body. An important implication derived from this finding is that the influence of lateral flow should be minimized in the design of a trough‐type liquid distributor, because the decrease in the discharge coefficient leads to non‐uniform outflow. The structure of a trough‐type liquid distributor is optimized to improve the liquid distribution performance by reducing the influence of lateral flow.     

垂直锐边孔口的自由出流特性(Ⅰ)流动状态和孔结构参数对孔流系数的影响

通过实验,考察了Reynolds数、液层高等操作参数和孔径、板厚等结构参数对垂直锐边孔口自由出流特性的影响。在此基础上,根据孔流系数曲线的不同规律,将孔流机理划分为“大孔机理”和“小孔机理”,并对孔流曲线进行了分区讨论,借助边界层理论,探讨了这两类孔流过程的机械能损失差异以及孔流曲线在不同操作区的机械能损失差异。     

Hydrodynamics and droplet size distribution of liquid–liquid flow in a packed bed reactor with orifice plates

A packed bed reactor with orifice plates (PBR@OP) was designed by adding orifice plates periodically in packed beds. Hydrodynamics and droplet size distribution in PBR@OP were experimentally investigated using fatty acid methyl esters (FAME)/water as the model liquid–liquid system. In PBR@OP, the flow pattern was close to plug flow. Droplets with Sauter mean diameter (d₃₂) of 150–550 μm were generated. The pressure drop of orifice, flow velocity and plate spacing were key parameters to control the droplet size. The reactor performance was evaluated by analyzing a FAME epoxidation process. At the same d₃₂ and residence time, the length and total pressure drop of PBR@OP were about 1/3 and 1/4 of those of PBR without orifice plates, respectively. Furthermore, a semi-empirical correlation describing the d₃₂ change in PBR@OP was developed, revealing a relative mean deviation of 8.64%. PBR@OP presents a cost-effective option for the intensification of liquid–liquid medium rate reactions.     

Experimental studies on orifice behavior and two-phase flow in flash chamber

A two-stage flashing experimental unit with a controlled orifice and 80 kW electric heater system was set up. The experiments on the hydraulic and thermodynamic process of liquid flow through a submerged orifice were carried out in this device. Two types of orifice were used, one was typical orifice with flat base the other was U-bottom. The relationship between volume flow, pressure drop, gate opening and the liquid level was discussed experimentally. Moreover, a dynamic high-speed CCD photographic measurement system has been developed, which covered the techniques of high-speed vision analysis system and computer disposal system of digital images. The images of two-phase flow near the orifice were obtained. Several conclusions are obtained on the liquid level, pressure drop and temperature difference, orifice opening as well as the vapor bubble behavior.     

Influence of an orifice on liquid–liquid two phase flow

The present study aims an in depth investigation of liquid–liquid horizontal flow through an orifice. Initial studies have been directed to observe the influence of the orifice plate on the phase distribution of the two liquids in the pipe. The flow patterns have been identified using an optical probe along with photographic technique. The probability density function (PDF) analysis of the random signals obtained from the optical probe has been adopted to quantify the observations. The cross‐correlation function between the probe signals upstream and downstream of the orifice has been estimated to check the repeatability of the phenomenon. The inception of dispersion in the downstream section has been observed to occur in the stratified region of the upstream. The use of an orifice as a homogenizer as well as a feasible flow‐metering device for liquid–liquid flow has been encouraged by experimental results.     

Effects of Orifice Orientation and Gas-Liquid Flow Pattern on Initial Bubble Size

In many gasliquid processes, the initial bubble size is determined by a series of operation parameters along with the sparger design and gasliquid flow pattern. Bubble formation models for variant gasliquid flow pat terns have been developed based on force balance. The effects of the orientation of gasliquid flow, gas velocity, liquid velocity and orifice diameter on the initial bubble size have been clarified. In ambient airwater system, thesultable gasllquid flow pattern is important to obtain smaller bubbles under the low velocity liquid crossflow con ditions with stainless steel spargers. Among the four types of gasliquid flow patterns discussed, the horizontal orifice in a vertically upward liquid flow produces the smallest initial bubbles. However the orientation effects of gas and liquid flow are found tobe insgnifican whenliq.uid velocity is.higher than. 3.2 m;sa or theorifice diameter is small enough.     

Adiabatic flow distribution of gas and liquid in parallel pipes—Effect of additional restrictions

The distribution of gas and liquid among four parallel pipes was studied with and without orifice restrictions. The results show that the two phases may not be equally distributed among the pipes. It is shown that the two-phase flow mixture can “choose” to flow in one, two, three or in all four pipes depending on gas and liquid flow rates, on pipe inclination and on the orifice plate size. Addition of orifice plates expands the region of stability and the range of flow in all four pipes. The experimental results are in reasonable agreement with the analysis.     

Column Dust Scrubber Based on an Orifice Plate to Intensify Gas‐Liquid Mixing

A column dust scrubber based on an orifice plate is developed for small and medium‐sized enterprises in China, which urgently need small‐volume, large‐flow scrubbers. The scrubber uses an orifice plate to evenly distribute the gas flow, which forms a uniform and stable impact on the liquid phase. As a result, dust removal via intensified gas‐liquid mixing can be achieved. A laboratory orifice plate scrubber model is developed, prototyped, and preliminarily studied considering the working process of the scrubber (mixed gas‐liquid flow pattern), liquid level, gas flow rate, pressure drop characteristics, dust removal efficiency, etc. The scrubber can achieve a good gas‐liquid mixing state when it is in a stable liquid column flow pattern. The drag coefficient of the scrubber is affected by the discharge of the gas stream to the liquid phase.     

新型阳极保护管槽式分酸器的研制与应用

介绍新型阳极保护管槽式分酸器的结构特点及在硫酸装置中的应用。该分酸器由分酸支管内设置节流孔板进行一级分酸，由分酸槽内的落酸管进行二次分酸。在落酸管的上端开一道长槽，以保证每个落酸管均匀满管出酸，并且增强了对管壁的阳极保护作用，避免了偏流和堵塞发生。工业应用表明该分酸器效果良好，预期使用寿命为10年。