自吸式文丘里洗涤器引射特性实验研究

为了优化自吸式文丘里洗涤器引射特性、改善气液分散效果,本文采用空气-水为工作介质,通过改变操作气速、液面高度及引入导流挡板等方式研究自吸式文丘里洗涤器引射特性变化规律。实验结果表明,自吸式文丘里洗涤器引射量、分散特征主要取决于喉部气相静压差、液面提升高度等操作因素以及导流挡板等文丘里管结构因素。喉部气相静压需大于洗消液液面提升所需压力才能实现对液相的引射功能,不引射流体时,喉部负压接近纯气相流动,一旦开始引射流体,喉管处有效吸液压差明显降低,引射量大小与文丘里环隙通道液体两侧静压差线性相关。增加导流挡板后文丘里出口处气液分散效果增强,平均雾滴粒径降低,相同能耗下引射量降低,约为无挡板时的15%。     

文丘里洗涤器内硫化氢气体碱液吸收过程的CFD模拟

采用双流体模型、RNG k-?湍流模型和组分输运模型对不同工况下自吸式文丘里洗涤器内Na OH溶液洗消H2S气体的引射能力、气液混合度和洗涤效率进行数值模拟,对引射量的模拟结果进行了实验验证.结果表明,在气液流动过程中,随气速增大,自吸式文丘里洗涤器引射量增大,洗涤器扩大段内液相径向分布均匀性减弱,液相倾向于贴壁流动.距喉部越远,气液速度越低,液相径向分散越均匀.在H2S碱液吸收过程中,气液相间化学反应主要集中于喉部至喉部上方扩大段长度1/5区域内,反应速率随距喉部距离增加先升高后降低.最大反应速率在喉部上方扩大段长度5%处.随气速增大,扩大段内气液相间化学反应速率提高,洗涤器出口处H2S浓度降低,洗涤效率增大,洗涤时间缩短.     

自吸式文丘里洗涤器吸收效果的影响因素

为考察影响自吸式文丘里洗涤器吸收效果的因素,以自吸式文丘里洗涤器为研究对象,建立了以乙醇-水为工作介质的耦合理论模型,并搭建了相应的试验装置。通过在自吸式文丘里洗涤器内部添加挡板的方式研究了带液量和分散雾化率对吸收效果的影响。结果表明:挡板会对自吸式文丘里洗涤器带液产生一定阻挡作用,但会在一定程度上提高自吸式文丘里洗涤器的自吸雾化率。外径相同、内径由小到大的环形挡板A1、A2、A3对文丘里洗涤器洗消效果影响不同,A2、A3挡板有效提升了吸收效率,A1挡板使吸收效率降低。一定范围喉部气速下吸收效果随挡板宽度增加而减小。     

新型文丘里洗涤器

文丘里洗涤器的应用十分广泛———除尘、除沫、气体净化。传统的文丘里洗涤器由收缩管、喉管、扩散管组成。高压液体通过喷嘴形成大液滴喷入气流中,在喉管处较高的气速和剪切力的作用下雾化成细小的液滴,与气体中的尘粒接触使其分离。但是,最近国外设计的新型文丘里洗涤器却采用了与传统文丘里洗涤器大相径庭的结构形式。新型文丘里洗涤器采用管缝隙作为气—液接触区,其最大特点是,液体的雾化不是由高速气流产生的,而是由液体喷嘴形成的,喉部只是提供气—液间的密切接触。因此高除尘(雾)效率不是以高气体压降为代价的。最初的管—隙式文丘…     

动力波洗涤器性能实验研究

以电厂电除尘器捕集的飞灰、空气、水为实验介质,采用单因素考察的方法,研究了液气比、液体喷射速度、气相速度对动力波洗涤器的压降、除尘效率的影响。结果表明:压降随着气相速度、液体喷射速度的增加而增加,利用实验结果拟合得出的压降数学模型,其计算值与实测值非常接近,可为设备的工业应用和放大设计提供可靠依据。除尘效率随着液气比的增加而增加,当液气比达到8—9 L/m3时,除尘效率达到99.9%并趋于稳定;与文丘里洗涤器的对比实验表明:除尘效率相同时,动力波洗涤器压降仅为文丘里洗涤器压降的26%,雾沫夹带质量浓度为文丘里洗涤器的4%。     

射水抽气器结构优化的试验研究

利用试验台对射水抽气器进行了结构优化试验。给出了试验设备、试验方法和试验表的表头设计方法。以正交试验设计方法分析了喷嘴压力、喉嘴间距和面积比3个因素对引射系数的影响,并得到了最优方案。模拟结果表明:3个因素对引射系数的影响程度依次是面积比喷嘴入口压力喉嘴间距;引射系数随喷嘴入口压力的增大而增大,随喉嘴间距和面积比的增大先增大后减小。     

文丘里卷吸型气液分配器液体分配性能的结构参数研究

为了改善滴流床用的内卷吸型气液分配器的液体分散差的现象,提出了一种文丘里卷吸型气液分配器,并对其结构参数进行了参数化研究,定量认识卷吸型分配器的结构参数对其气液分配性能的影响。在冷态实验装置上进行了文丘里卷吸型气液分配器性能实验,建立了耦合群体平衡模型的欧拉-欧拉两相流模型,数值模拟了文丘里卷吸型气液分配器气液两相分配流动过程。冷模实验结合数值模拟,系统性考察了各结构参数对卷吸型气液分配器的液体分布均匀性、喷淋半径以及压降的影响。结果表明,采用具备缩-扩结构的文丘里管作为降液管能够有效提升卷吸型分配器的分布均匀度和喷淋半径,并显著降低压降。通过正交试验,获得了主要结构参数与分配性能的相关性,给出了结构参数与性能指标的经验关联式。降液管的扩张段是改善液体分配性能的关键结构,其扩张角为30°时液体分配性能最好。     

文丘里引射反应器的喷嘴优化及压降分析

为解决黄磷脱砷系统中搅拌反应器反应不充分的问题,根据其工艺需求,研制出一种新型反应器--文丘里引射反应器,并将其用于贵州某黄磷厂的中试实验中.利用CFD数值模拟软件FLUENT的Realizable k-ε湍流模型和欧拉两相流模型,在经验公式范围内,对4种不同喷嘴出口直径(分别为6、8、10和12 mm)条件下的压降变化进行了研究和考察.结果显示,利用中试装置得到的相关实验数据与数值模拟结果基本吻合,说明数值模拟的结果是可靠的;随着喷嘴出口直径的增大,面积比减小,反应器所形成的压力比越大,驱动能力越强,同时工作效率也越高;喷嘴直径越小,产生的压力降越大,局部能量损失也越大,分散混合效果越好.根据模拟结果,为黄磷脱砷系统中文丘里引射反应器的工业放大设计提供了参考依据.     

单喷嘴低压引射器的结构设计与数值分析

引射器作为大气式燃烧器的重要组件,对燃烧器的稳定、完全燃烧具有重要的影响,因此对引射器的工作过程和影响其工作性能因素的研究尤为重要。本文首先对大气式燃烧器用的单喷嘴低压引射器的结构形式及具体尺寸进行了设计,并对设计出的引射器建立了三维、稳态的数学模型。然后利用计算流体力学(computational fluid dynamics,CFD)软件对引射器进行了模拟计算,探究了引射器内燃气与空气发生动量和质量交换的混合过程并研究了工作喷嘴出口直径、混合室长度、燃气供气压力、引射器出口背压4个因素对引射器质量流量引射系数的影响。研究结果表明:当引射器其他参数相同时,工作喷嘴出口直径与混合管长度都存在一个最佳值使得引射器达到最优的引射系数;燃气供气压力增大对引射系数的影响很小,引射系数几乎不变,而当引射器出口背压增大时,引射系数却下降的很快。     

关于水煤浆气化炉文丘里洗涤器结构及流程优化小结

水煤浆气化炉文丘里洗涤器的主要作用是对水煤气进行洗涤除尘.针对在实际运行过程中,由于文丘里洗涤器结构不合理及其洗涤水水质差,导致文丘里洗涤器喷头出水孔结垢堵塞,影响洗涤效果,以及文丘里洗涤器喉管及套管冲刷泄漏,影响生产装置的安全稳定运行的问题,通过对文丘里洗涤器结构及洗涤水流程进行技术改造优化,消除所存在的问题.     

Experimental and Theoretical Investigation of Droplet Dispersion in Venturi Scrubbers with Axial Liquid Injection

Droplet dispersion in a Venturi scrubber with axial liquid injection was investigated both experimentally and theoretically. The main objective of this study was to develop a mathematical model to predict droplet dispersion in a Venturi scrubber with axial liquid injection. The effects of the Peclet number and droplet size distribution on droplet dispersion were studied using the developed model. Sampling of the droplets was carried out, isokinetically, in 16 positions at the end of the throat section. The experimental data were used to find the parameters of the developed model, such as the Peclet number. From the results of this study, it was found that the Peclet number was not constant across the cross section of the scrubber channel. In order to achieve a better agreement between the results of the model and the experimental data, it was required to consider Peclet number variations across the Venturi channel. It was also revealed that the parameter representing the width of the Rosin‐Rammler distribution of droplet size could not be considered constant and it was influenced significantly by the operating parameters such as liquid flow rate and gas velocity.     

Experimental verification of the effect of liquid deposition on droplet size measured in a rectangular Venturi scrubber

It has been reported by previous studies [1], [2], [3], [4], [5], [6], [7] that droplet size in a Pease-Anthony Venturi scrubber depends on the jet atomization conditions, such as jet velocity and gas velocity. The assumption of this paper is that actual collector-droplet size in a confined tube such as the Venturi scrubber also depends significantly on preferential droplet deposition on the tube walls, which remove preferentially droplets of a certain size from the core, modifying the mean droplet size of the remaining droplets. To account for this effect, the present study is focused on the experimental measurement of the liquid deposition on the walls of a Pease-Anthony Venturi scrubber and the droplet size remaining in the core. The experiments were carried out varying jet penetration and the number of the injection orifices. A correlation, using dimensionless numbers, was proposed to quantify the influence of each experimental condition. The results showed that liquid deposition has a significant influence in actual collector-droplet size inside a Venturi scrubber.     

黄磷脱砷中文丘里反应器的流固耦合研究

基于计算流体力学和流固耦合原理,利用FLUENT的Realizable k-ε湍流模型,计算得到文丘里反应器内部流场分布,通过ANSYS Workbench中的流固耦合技术,将流场分析的结果数据传递到Static Structure中进行结构静力分析,从而得到流场分布、喷嘴所受压力、喷嘴变形、应力应变等分析结果。结果显示,在特定工作压力条件下,文丘里反应器的扩散管在工作中有向吸入管相反方向变形的趋势;在整个结构中,最大应力和应变值均集中在喷嘴内流道中;由于高速流体的射流作用,喷嘴出口附近结构主要承受拉应力的作用。由于计算得到的应力和应变数值均处于较低水平,因此结构能够满足工况的要求。     

Mathematical Modelling of Non‐Isothermal Venturi Scrubbers

A mathematical model consisting of differential equations for energy, momentum and material exchange is developed for a non‐isothermal Venturi‐type scrubber. By this model, the effects of heat and mass transfer on droplets concentration distribution and removal efficiency of particulate in a non‐isothermal Venturi scrubber can be investigated. In order to approach a realistic model, the liquid film flow on the walls and droplet size distribution are considered. The model is validated by comparing the results of mathematical model by plant and experimental data reported in the literature. The Results section of this work reveals that the inlet humidity and temperature of the gas can affect the removal efficiency of the scrubber.     

Absorption of CO2 by aqueous triethanolamine (TEA) solutions in a high shear jet absorber

CO₂ diluted with N₂ was absorbed by aqueous triethanolamine (TEA) solutions in a jet absorber consisting of a high pressure stainless steel vessel with a pressure nozzle at the top. The gas mixture and the aqueous solution were passed simultaneously, through the pressure nozzle into the absorber. Due to the high shear imparted to the liquid very fine droplets were produced, which resulted in a very high interfacial area and rapid mass transfer. CO₂ was absorbed rapidly by the TEA solution. The effects of gas and liquid flow rates, solution concentration and CO₂ partial pressure on CO₂ loading per unit mole of TEA and the overall mass transfer coefficient were examined. CO₂ loading per mole of TEA increased with gas flow rate and decreased with liquid flow rate and solution concentration. The overall mass transfer coefficient was found to increase with gas and liquid flow rates. Both the CO₂ removal per mole of TEA and the overall mass transfer coefficient were found to be a strong function of power dissipated at the nozzle.     

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.     

新型气液逆流撞击洗涤喷嘴的优化

针对一种新型气液逆流撞击式洗涤喷嘴,通过冷模实验,采用溶氧法考察了不同结构喷嘴的气液两相传质性能。结合解析率及流型变化,考察了喷嘴出口直径、切向进液口倾角、旋流室收敛段锥角、切向进液口直径、喷口长度5个参数对传质的影响,确定了优选喷嘴的结构尺寸,分析了该优选喷嘴在不同操作条件下(气速、表观液气比和轴切比)的传质效果。结果表明,优选喷嘴在轴切比为0.4~0.6且气速较高时传质效果较好。     

文氏栅洗涤器除尘脱硫实验研究

采用双碱法脱硫技术 ,在自行设计的多通道文丘里洗涤器 (简称文氏栅洗涤器 )进行模拟燃煤烟气的除尘脱硫试验。其试验过程是 :先在三种不同喉部参数 (分别称为 1# ,2 # ,3 # )的文氏栅洗涤器进行除尘试验 ,经过优选后 ,在 2 #文氏栅洗涤器上进行脱硫试验。试验结果表明经过优选的 2 #文氏栅洗涤器有着较高的除尘脱硫效率。当文氏栅洗涤器的运行参数为 :pH =12、液气比为 0 .75L/m3、 [Na+ ]=0 .3mol/L、 [SO2 ]=12 0 0× 10 -6,文氏栅洗涤器的除尘效率大于 96 % ,脱硫效率大于 80 %。经过完善后可用作中小型燃煤锅炉烟气的除尘脱硫     

Two-phase flow and mass transfer in scrubbers

Experimental investigations were carried out in spray scrubbers of different sizes with cocurrent flow of gas and liquid. Of special interest were the local processes in the mass transfer zone. The scrubber was operated with warm water/air system (cooling tower) to obtain detailed information about mass transfer. Air is being humidified with water vapour, which in turn leads to a temperature drop in the liquid. The liquid temperatures are relatively easy to measure and are shown as liquid isotherms. In the case of plug flow, the liquid isotherms should be straight horizontal lines. In reality, significant deviations from plug flow are caused by the transfer of liquid to the walls. A large part of the liquid forms a film flow at the wall. Furthermore, nearly all the mass transfer is completed in the zone of liquid atomization immediately beneath the nozzle. The number of measured transfer units was between 0.5 and 2.0 and was significantly influenced by the liquid flow rate. Based on the improved knowledge of the proceses inside the scrubber, a simplified model has been developed. Since the model simulates all the essential processes inside the mass transfer zone, liquid distribution and mass transfer efficiency can be approximately predicted.     

PREDICTION OF PRESSURE DROP IN A VENTURI SCRUBBER: EFFECT OF LIQUID FILM AND RE-ENTRAINMENT

A mathematical model has been developed for prediction of pressure drop in a Venturi scrubber. This model includes the effect of the amount of liquid film and re-entrainment of liquid droplets from liquid film. The result of the present model is compared with experimental data of Viswanathan et al. (1985) as well as with the other models (Viswanathan et al., 1985; Boll, 1973). Results of this study indicate that at high liquid to gas ratios prediction of pressure drop can be improved by considering re-entrainment and liquid film effects. Also the effects of gas velocity and liquid to gas ratio were investigated on the rate of droplet re-entrainment and pressure drop.