一种新型的喷射鼓泡传质设备:泡罩立体筛板

介绍了泡罩立体筛板的结构特点和实验情况,采用空气-水物系在1 000 mm×400 mm的有机玻璃塔中进行了塔板压降、雾沫夹带和漏液量的流体力学性能研究,并与垂直筛板的流体力学性能进行对比,结果表明,泡罩立体筛板的流体力学性能优于垂直筛板。     

垂直筛板液体提升量的研究

依据垂直筛板的传质过程和一些实验关联式,结合脱苯塔汽提段的实际设计数据和运行结果,分析了不同形状的帽罩、不同的帽罩布置方法以及板孔气速这些因素对垂直筛板塔板液体提升量和塔板效率的影响,得出结论:与其他的帽罩形状和排列方式相比,设置分离板的方形帽罩以方阵形式排列,并且将板孔气速取值控制在8.0—15.0 m/s,可有效提高塔板的液体提升量及塔板效率。将其应用在垂直筛板塔板的实际设计中,便可获得较高的液体提升量和塔板效率。     

泡罩垂直筛板性能研究

选用BVS-1型和BVS-2型泡罩垂直筛板,用水和空气模拟塔内气液二相流动工况,在一定时间内采集雾沫夹带量和漏液量,研究其流体力学性能和操作弹性。结果表明:前者操作弹性比大于2,最大可达到3.5;用微差压计测得在操作弹性范围内的总板压降为850—1 400 Pa;采用氧解吸方法测试单板效率,对流体力学性能较好的BVS-1型泡罩垂直筛板和现有的垂直筛板在传质性能上进行了比较,前者比后者的单板效率提高了约20%。     

S型垂直筛板流化床的性能

在S型垂直筛板流化床中,以FCC催化剂和空气作为流化介质,对垂直筛板流化床的流化性能进行冷模实验研究,考察了板孔气速、固体循环量和帽罩结构对床层压降和帽罩提升量的影响,用提升量收集器测量帽罩提升量。实验结果表明,床层压降随板孔气速和帽罩底隙高度的增加而增加,而随塔板开孔直径、帽罩开孔直径和开孔率的增加而下降。帽罩提升量则随板孔气速、固体循环量、塔板开孔直径及帽罩底隙高度的增加而增加;随帽罩开孔直径的增加,提升量先增加后下降。     

立体旋流筛板空间气相流场的CFD模拟

应用STAR-CCM+软件,采用Realizable k-ε模型,对立体旋流筛板空间气相流场特性进行了数值模拟研究。结果表明:立体旋流筛板空间主要存在贴近筛板壁面的穿孔流动与两筛板间的旋流流动2种方式,气体经立体旋流筛板的流动过程分起旋阶段与旋流发展阶段。在贴近筛板壁面的区域,由内筒外壁至外筒内壁方向,穿孔流动速度在各流动阶段均呈增加的趋势;在两筛板间区域,起旋阶段,由内筒外壁至外筒内壁方向旋流流动速度值变化较小,沿旋流方向靠近下一块筛板区域的速度值较大;旋流发展阶段,由内筒外壁至外筒内壁方向旋流流动速度值呈先降低再增加的趋势,沿旋流方向靠近上一块筛板区域的速度值较大。在轴向不同高度区域,贴近筛板壁面的穿孔速度为中部最大、上部次之、下部最小;两筛板间的旋流流动速度为上部较小,中、下部较大。各区域速度值随着气相动能因子的增加而增加。     

垂直筛板流化床中FCC催化剂的流化性能

以FCC催化剂颗粒研究垂直筛板流化床内构件对气固两相流化性能的影响,考察了板孔气速、颗粒循环量和帽罩开孔比等筛板结构对流化床压降和提升量强度的影响. 结果表明,气固两相总体逆流流动条件下,帽罩内气速达4 m/s,气固高速并流喷射无气泡,两相接触好、返混小,属快速流态化. 由于没有气泡,床层压力波动小,在塔板上颗粒返混小. 垂直筛板压降随板孔气速、帽罩底隙高度增大而增大,随帽罩开孔比、板孔径增大而减小,颗粒提升量大,床层压降大. 提升量强度随板孔气速、帽罩底隙高度、颗粒循环量增加而增大,随帽罩高度与塔节高度比增大而减少,随帽罩筛孔孔径变化存在最大值. 当帽罩开孔比为1.2~2.5、板孔面积与帽罩截面积比为0.42、帽罩底隙高与板孔孔径比为0.36~0.64时帽罩流化性能较好.     

新型矩形垂直筛板的研究

研究了一种矩形垂直筛板.该塔板是在塔板上设置数个由板孔、升气筒、矩型罩、底隙所构成帽罩单元,在单元内气液呈喷射状态接触,实现两相传热传质.流体力学性能和传质性能研究证明该塔板压降、漏液等性能与新型垂直筛板相当,但雾沫夹带要比新型垂直筛板低.因而该塔板具有较大的生产处理能力和较宽的稳定操作范围.     

新型立体垂直筛板塔的开发进展

本文介绍了新型立体垂直筛板的结构、传质原理和塔板特性,详细介绍了新型立体垂直筛板塔的开发进展和十二种新开发的立体垂直塔板,并详尽分析各种立体垂直筛板的帽罩形式及特点,指出了其优缺点,提出了今后立体垂直塔板开发的趋势和方向.     

立体传质塔板相对液体提升量的计算

液体提升量是影响立体传质塔板(CTST)气液传质的条件有关.今分析了气液两相在帽罩内部的流动特点和能量分布状况,以立体传质塔板帽罩单元为研究系统,分析了气液两相带入和带出系统的能量以及通过帽罩时的能量损失,同时考虑帽罩结构和气液物性的影响,建立了立体传质塔板相对液体提升量数学模型.由于影响流动过程能量损失的因素比较复杂,将其表达为阻力系数的形式,并作为模型的参数.在直径600 mm的实验塔中对液体提升量进行了实验研究,确定了模型参数,并对模型进行了检验.结果表明,所建模型能够较好地反映立体传质塔板上液体的相对提升量.     

垂直筛板构件强化SDS在泡沫分离液相吸附的研究

为提高表面活性物质在泡沫分离液相的吸附,开发了一种液相安装垂直筛板构件的新型泡沫分离塔,以传统液相无构件的泡沫分离塔为对照塔,十二烷基硫酸钠(SDS)为体系,考察了装有垂直筛板构件的塔板层数、板间距和垂直帽罩数对气泡大小、SDS吸附密度和平衡时间的影响。结果表明在液相添加垂直筛板构件能有效增加SDS的吸附密度并缩短平衡时间。在塔板层数为5、板间距为60 mm和垂直帽罩数为4时,SDS吸附密度比对照塔提高58.8%。     

Liquid mixing on bubble-cap and sieve plates

Experimental frequency-response results and their interpretation by the diffusion equation lead to a correlation of liquid mixing with operating conditions for large-scale bubble-cap and sieve plates, in terms of a modified Péclet number and the liquid hold-up and froth density. Other mixing concepts are critically discussed. A simple method of predicting the effect of liquid mixing on plate efficiency is proposed, assuming complete mixing of the vapour between plates.     

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。     

摇摆对气液并流模式立体旋流筛板压降的影响研究

以空气-水为实验介质,在喷淋密度78～182 m³·(m²·h)^-1、气相动能因子1.19～2.77 m·s^-1·(kg·m^-3)^0.5、摇摆幅值Θ=5°～15°、周期T=8～20 s的条件下,测定了气液并流模式下立体旋流筛板(TRST)的压降,考察了气液通量、塔板数量、位置和方式对压降的影响,并与直立和倾斜工况对比。结果表明：增加倾斜及摇摆角度干板压降略微下降;摇摆时的湿板压降介于直立和倾斜之间,受摇摆角度影响较大,基本不受周期影响;增大气量有利于抵抗倾斜及摇摆的影响,而增大液量会使倾斜及摇摆的影响作用加剧。整体上,塔板顺、逆向安装时的湿板压降分别在100 Pa和170 Pa以内,而逆向安装的变化率约为顺向的2倍,这是由于逆向安装下改变了气液流动方向,增大了能量损失。建立了气液并流摇摆工况下TRST的湿压降预测模型,相对误差在15%以内。     

立体旋流筛板并流时的流型特征及其操作域

流型影响气液通过塔板时传热传质效率,为了确定立体旋流筛板上不同喷淋密度Lw,空塔气相动能因子Fs的流型及其操作域,采用安装立体旋流筛板内构件的冷模实验塔,在Lw=39—260 m~3/(m~2·h),Fs=0.78—3.9(m/s)(kg/m~3)~(0.5)的操作条件下,测量立体旋流筛板内部差压脉动信号并记录流动照片。使用时域及标准偏差分析并结合流动图片的方法,主要考察了气液并流通过立体旋流筛板的流型特征及其操作域。实验结果表明:液相通量对各流型转变影响较大,Lw70 m~3/(m~2·h)时为连续-分层流,Lw=70—145 m~3/(m~2·h)之间时为鼓泡-分层流或栓塞流,Lw145 m~3/(m~2·h)为泡沫流;当Lw=70—145 m~3/(m~2·h)时,鼓泡-分层流和栓塞流的转变主要受气相通量Fs影响,Fs1.95(m/s)(kg/m~3)~(0.5)为鼓泡-分层流,Fs2.34(m/s)(kg/m~3)~(0.5)为栓塞流。     

Synthesis and characterization of a new microporous cesium silicotitanate (SNL-B) molecular sieve

Ongoing hydrothermal Cs–Ti–Si–O–H₂O phase investigations has produced several new ternary phases including a novel microporous Cs–silicotitanate molecular sieve, SNL-B with the approximate formula of Cs₃TiSi₃O_9.5 · 3H₂O. SNL-B is only the second molecular sieve, Cs–silicotitanate phase reported to have been synthesized by hydrothermal methods. Crystallites are very small (0.1×2 μm²) with a blade-like morphology. SNL-B is confirmed to be a three-dimensional molecular sieve by a variety of characterization techniques (N₂ adsorption, ion exchange, water adsorption/desorption, solid state cross polarization-magic angle spinning nuclear magnetic resonance). SNL-B is able to desorb and adsorb water from its pores while retaining its crystal structure and exchanges Cs cations readily. Additional techniques were used to describe fundamental properties (powder X-ray diffraction, FTIR, ²⁹Si and ¹³³Cs MAS NMR, DTA, SEM/EDS, ion selectivity, and radiation stability). The phase relationships of metastable SNL-B to other hydrothermally synthesized Cs–Ti–Si–O–H₂O phases are discussed, particularly its relationship to a Cs–silicotitanate analogue of pharmacosiderite, and a novel condensed phase, a polymorph of Cs₂TiSi₆O₁₅ (SNL-A).     

Sorption kinetics of eight gases on a carbon molecular sieve at elevated pressure

The sorption kinetics of eight different molecules (O₂, N₂, Ar, CO, CO₂, SO₂, CH₄ and H₂) on a carbon molecular sieve was studied over a wide range of pressures up to 15 atm by using a volumetric method. The acentric factor was suggested as a potential factor to estimate the relative sorption rate. Since the apparent time constants of all the components showed much stronger dependence of pressure than those expected by the traditional Darken relation and the structural diffusion model, new models with the diffusion relation at the supercritical condition was proposed to predict the kinetic behaviors in the micropores. The proposed model successfully predicted the apparent time constant up to high pressure. In addition, the semi-empirical model that combined acentric factor with the proposed model was able to predict the strong pressure dependence accurately. However, since the strong adsorbates, CO₂ and SO₂, showed two-stage kinetic behavior with pressure, which was different from that of the other adsorbates. The kinetic behaviors of these molecules could be predicted by using two different sorption models.     

Flow regimes and pressure drop of a composite tridimensional rotational flow sieve tray under concurrent gas-liquid flow

A composite tridimensional rotational flow sieve tray (CTRST) is proposed. The flow patterns of CTRST were visually categorized, combined with the standard deviation of the pressure difference. In the TRST area of the internal packing-type tray, the membrane-drip column and foam-embolic flow is present, while bubbly and milk froth-ribbon flow is present in the packing area of the external packing-type tray. The effect of the tray structure parameters on the pressure drop under co-current flow was investigated. The dry and wet pressure drop is within 160 and 900 Pa, respectively. Under the same structural parameters, the pressure drop of the internal packing-type tray was higher than that of the external packing-type tray. The flow characteristics of the standard tray under the countercurrent flow were compared. The CTRST was found to be more suitable for co-current flow. A prediction model pressure drop under co-current was established with an error of 15.5%.