旋流塔板气液接触状态及塔板压降

旋流塔板有复杂的气液接触状态。对应于一定的气液接触现象,气液接触状态可分为倾泻区、泡花区、喷射区和全喷射区。在四种接触状态下,塔板有效压降与气速的关系有明显的差别。以有效压降随气速变化规律的转化点作为气液接触状态的转化点,确定了塔板上各种气液接触状态的区域,并关联了接触状态转化点的操作条件。对喷射区有效压降的分析得到,有效压降主要决定于塔板上液体产生的静压降,气体径向速度可以忽略,而使喷射区内有效压降不受气速影响。全喷射区内,气速影响溢流管和溢流锥的溢流能力,而使气速明显地影响塔板有效压降。泡花区内,漏液量随气速的增大而减小;因此,气速影响塔板有效压降。适当地简化流况,提出了有效压降关联式,利用实验数据确定了其中的参数。     

气液并流旋喷塔板的流体力学性能

结合新垂直筛板塔(NVST)和旋流板的特点提出了一种新型塔板——气液并流旋喷塔板，以空气水体系测试其流体力学性能。实验表明这种塔板的压降比NVST塔板减小10％20％，雾沫夹带上限比NVST塔板低，这些特性将使其比NVST塔板有较大的处理能力；而大提升量则保证了其有较高的传质效率，是一种很有应用前景的塔板。     

低喷淋密度下P-S复合塔板的持液特性研究

填料-筛板复合塔板是一种被用于高气液比吸收处理过程的塔内构件,其持液量与液相停留时间对传质传热具有重要影响,为此进行了相关性能的研究.测定分析表明:P-S复合塔板的持液量可通过填料液膜区持液和浸润填料区持液两部分进行估算,停留时间可在实验基础上据模型计算.同时,在单因素实验条件下,P-S复合塔板的动持液量随喷淋密度的增...     

新型立体传质塔板及其流体力学性能

新型立体传质塔板（CTST）结构新颖, 充分利用塔板空间进行传质,具有通量大、效率高、压降低、抗堵性能强、消泡性能好等优点.在工业规模的实验塔上对立体传质塔板的塔板压降、帽罩底隙处罩内外压强、帽罩内部气相速度分布规律、雾沫夹带量、气体对液体的提升能力、塔板空间持液量等几个方面的流体力学性能进行了研究.结果表明,立体传质塔板克服了穿过塔板液层的阻力,板压降较低;塔板上帽罩底部的进液口处,罩内压强低于罩外,利于吸液;罩内气相速度分布比较合理;气液两相负荷均可较大幅度提高,而且雾沫夹带量非常低;气体对液体的提升性能以及塔板空间的持液性能都比较理想.     

复合塔板气液运动的实验研究

采用多路电导测试系统,在直径500mm的冷模塔内,以空气-水为试验物系,研究了开孔率20%和25%复合塔板上的气液运动规律.实验揭示了气液穿孔运动的三种状态通液、通气和阻塞,并对复合塔板的气液运动机理进行了阐述.实验考察了空塔动能因子F、喷淋密度LV和开孔率φ对通液率、通气率和阻塞率的影响,分析了筛孔真实气速与复合塔液泛点关系.结果表明F因子增大,通气率也增大,而通液率和阻塞率减小;喷淋密度增加, 通气率下降,通液率上升;开孔率较大,则通气率较小,通液率和阻塞率较大;在实验范围内(开孔率20%及25%、喷淋密度5～40m3·(m2·h)-1的情况),复合塔液泛点的筛孔真实气速在11m·s-1左右,为其它物系确定操作上限提供了依据.     

板式塔的进展

介绍了板式塔的发展概况,着重浮阀塔板,喷射型塔板,旋流塔板,多降液塔板,复合塔板,并对近年来新开发的塔板的特点和性能进行了简要评述。     

红外热像仪测量多降液管塔板液相等停留时间分布的实验研究

多降液管塔板目前在精馏、吸收和解吸等领域应用日益广泛.多降液管塔板由于降液管悬挂,且上、下塔板的降液管垂直布置,故它的液相流场分布较为复杂.提出了测试塔板上液相流场分布的一项新技术:与塔板上液体同质的高温示踪剂液体在塔板上阶跃注入,用红外热像系统拍摄高温示踪剂液体的流动,从而作出塔板上等停留时间分布图.实验在直径1200 mm的有机玻璃塔中进行,测试塔板为单根悬挂降液管塔板和两根悬挂降液管塔板,物系为空气-水.实验得到不同液量下单根和两根悬挂降液管塔板上等停留时间分布图.结果表明:该测试技术方便、精确、且示踪剂对塔内液体无干扰污染.多降液管塔板存在滞流区,且滞流区随液量增大而增大.     

立体旋流筛板并、逆流操作时压降的对比研究

立体旋流筛板(TRST)是一种新式穿流型塔板。前期研究均基于气液并流的操作形式,而逆流时的表现尚不明确。因此文章对TRST在并、逆流操作下的压降进行了对比研究,考察不同气液通量、塔板安装位置及安装方式对压降的影响,并测定了逆流操作下的载点及泛点。结果表明:2种操作下,塔板逆向安装时的压降均大于顺向安装;并流时各塔板气液负荷均衡,压降值≤550 Pa。逆流时可将操作域分为低负载区及高负载区。低负载区压降与同范围并流操作时相近;高负载区压降较大,操作域较窄且各板气液负荷不均。受限于液泛的影响,逆流操作时的压降值≤300 Pa。相较于并流操作,逆流操作时气量调节范围至少小45%,液量范围至少小37.5%。综合考虑,TRST更适宜并流操作。     

宝塔罩型塔板性能研究

开发了一种宝塔罩型塔板。该塔板是在塔板上设置数个由板孔、升气筒、塔型罩、进液孔所构成的豆塔罩单元，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、氧解析效率、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。     

新型双层喷射立体传质塔板在催化裂化装置各塔的应用

介绍了新型双层喷射立体传质塔板是针对高气相和大液相负荷开发,具有双层喷射结构,降低了液滴喷射初速度,不仅降低了塔板压力降,而且有效降低了塔板雾沫夹带量.所以双层喷射立体传质塔板可以大幅度提高塔内气液相流体的流速,提高处理能力.在催化裂化分馏塔中的应用,充分证明了双层喷射立体传质塔板的空塔动能因子可以达到3.2(m·s-1)·(kg·m-3)0.5,降液管溢流强度可以达到130m3·m-1·h-1.     

HYDRAULICS AND EFFICIENCY OF SCREEN TRAYS FOR DISTILLATION

Screen trays are proprietary devices similar to sieve trays which are used in distillation and absorption applications. The pressure drop, liquid holdup and entrainment are measured for screen trays in an air/water column and compared to results obtained with sieve trays. The effciencies of both types of trays were compared in a distillation column using systems of various physical properties (methanol/water, acetic acid/water and cyclohexane/n-heptane mixtures). It was found that the screen tray has a lower dry pressure drop, higher liquid holdup, lower entrainment and weeping, and higher jet flooding capacity than the sieve tray. However, the effciencies of both trays are similar for the systems studied. A model was developed for predicting total pressure drop for screen trays using an air/water column. The model was tested using results for methanol/water, cyclohexane/n-heptane and acetic acid/water systems at total reflux. The deviations are within +/- 20% for 90% of the data points. The effect of a bed of mesh packing on the screen tray was also studied. It was found that the packing led to a higher tray effciency, but resulted in a higher tray pressure drop.     

Hydraulics and efficiency of screen trays for distillation

Screen trays are proprietary devices similar to sieve trays which are used in distillation and absorption applications. The pressure drop, liquid holdup and entrainment are measured for screen trays in an air/water column and compared to results obtained with sieve trays. The effciencies of both types of trays were compared in a distillation column using systems of various physical properties (methanol/water, acetic acid/water and cyclohexane/n-heptane mixtures). It was found that the screen tray has a lower dry pressure drop, higher liquid holdup, lower entrainment and weeping, and higher jet flooding capacity than the sieve tray. However, the effciencies of both trays are similar for the systems studied. A model was developed for predicting total pressure drop for screen trays using an air/water column. The model was tested using results for methanol/water, cyclohexane/n-heptane and acetic acid/water systems at total reflux. The deviations are within +/- 20% for 90% of the data points. The effect of a bed of mesh packing on the screen tray was also studied. It was found that the packing led to a higher tray effciency, but resulted in a higher tray pressure drop.     

十字旋阀塔板漏液性能

在φ1000mm的圆塔内,以空气-水为介质,对十字旋阀塔板的泄漏率进行了测试,考察了液流强度、出口堰高等因素对泄漏性能的影响,并将其与交错十字旋阀塔板、组合导向浮阀塔板和F1型浮阀塔板的泄漏率进行了对比。结果表明:十字旋阀塔板在气速超过临界阀孔气速且液流强度较小时具有很好的漏液性能,经数据关联,获得了十字旋阀塔板漏液点孔速的关联式。     

The turbulent behavior of novel free triple-impinging jets with large jet spacing by means of particle image velocimetry☆

A novel reactor that achieves rapid liquid–liquid mixing via free triple-impinging jets(FTIJs) is developed to improve mixing efficiency at unequal flow rates for liquid–liquid reactions. The flow characteristics of FTIJs were investigated using particle image velocimetry(PIV). The instantaneous and mean velocities data at different Reynolds numbers(Re) were analyzed to provide insights into the velocity distributions in FTIJs. The effect of jet spacing on the stagnation points, instantaneous velocity, mean velocity, profiles of the x- and ycomponents of mean velocity, and turbulent kinetic energy(TKE) distributions of FTIJs were investigated at Re = 4100 with a volumetric flow rate ratio of 0.5. The characteristics of the turbulent flows are similar for all jet spacings tested. Two stagnation points are observed, which are independent of jet spacing and are not located in the center of the flow field. However, velocity and TKE distributions are strongly dependent on the jet spacing.Decreasing jet spacing increases the expansion angle and the values of TKE, leading to strong turbulence, improving momentum transfer and mixing efficiency in FTIJs. The present study shows that optimization of the operating parameters is helpful for designing FTIJs.     

Hydrodynamic model for controlled cycling in tray columns

The paper describes a model for controlled cycling in tray columns. Gas phase dynamics and hydrodynamic relations are included in the proposed model. The model has been simulated on a digital computer.Gas phase dynamics is found to play an important role for cyclic operation of distillation columns, while as the effect of gas phase dynamics can be ignored for absorption columns.In a 5-tray distillation column reasonable separation between liquid and vapour flow periods can be achieved, but with increasing number of trays the switch-over from one period to another becomes less ideal. For a ten tray column the flow situation is unacceptable.The simulations also show that the plug flow condition in the liquid flow period is most difficult to satisfy in the top and bottom of the column. The risk of flooding on some trays and other trays running dry increases when the numbers of trays increases.Finally it is shown that the hydrodynamic behaviour may be improved by changing the geometry of some of the trays.     

气液并流筛板式填料压降的数值模拟

基于欧拉-欧拉模型,采用CFX软件对筛板式填料的气液两相并流流动进行了模拟。将模拟所得的压降与填料的出厂特性值进行了对比,发现在液气动能参数较小的情况下,两者吻合较好。分析了该流场内的速度分布和压力分布的特点,射流卷吸作用使流场内两相流体混合,但涡旋使筛板下方压强减小,射流撞击使筛板上方压强增加。对不同结构的矩形筛板式填料的压降进行研究,结果表明：筛板孔径和液相流量是影响筛板压降的重要因素,开孔直径越小,液相流量对单板压降的影响越大;上层筛孔投影与下层筛孔相交的结构更能有效降低单板压降。液相流量较大时,两个不同板间距的单板压降曲线将相交于一点,气相流量低于此交点时,板间距越小,单板压降越大;气相流量高于此交点时,则相反。     

Understanding maldistribution in 3-pass trays

Understanding 3 pass trays is the key to design of 6 pass trays, such as those in the large towers expected in carbon-capture services. This paper presents a hydraulic distribution model for 3 pass trays with no liquid or vapor equalization. The model is verified by comparison with FRI's test data and with one operating tower. Our paper predicts good distribution for the 3 pass trays tested at FRI, and shows that the poor efficiencies in some of the tests were due to losing the downcomer seals and not tray maldistribution. The model predicts good distribution at maximum rates in the operating tower, but finds that at lower rates, where valves open and close, there is an extreme sensitivity of vapor distribution to small pressure drop variations. This sensitivity precludes reliable modeling of distribution in this region and may define an unstable region in the operation of 3 pass trays.     

Mass transfer in a single-hole tray column

A theoretical model for deuterium exchange in the H₂S/H₂O system was derived to describe mass transfer in the bubble formation, bubble displacement and bubble breakup regions above a single-hole tray in an 8 cm diameter transparent column. The model was applied to data measured at 31°C in the pressure range of 790 to 2000 kPa and in a wide range of gas and liquid flows. High speed cinematography was used to measure bubble diameters, bubble formation times and bubble contact times in the liquid, all of which are parameters in the mass transfer models. Results show that for single-hole trays and the major part of mass transfer occurs in the upper surface of the froth where bubbles disengage from the liquid. However, when the same model is applied to pilot plant sieve trays, it is shown that the bulk of mass transfer takes place in the region where bubbles are ascending in the froth. The tray efficiencies predicted by the model agree well with measured values.     

蒸馏塔板上汽液传质系数的确定——非平衡池法(Ⅱ)实验数据处理

对文献报道的塔板操作数据用非平衡池法进行了分析处理.单相阻力控制系统(氨吸收)数据的处理结果与AIChE关联一致.对双相阻力控制系统(甲醇-水蒸馏)数据的处理表明,筛板汽相传质系数比AIChE关联的计算值高约20—70%.文中详细讨论了实验数据处理中各种问题的解决方法.结果表明,本文提出的传质系数确定方法比效率法和化学法更合理和方便.     

射流鼓泡反应器内气液分散状态检测

射流鼓泡反应器内随着射流速度的增大,先后经历气泛、载气和完全分散三种气液分散状态。本文在射流鼓泡反应器实验装置中,利用Pavlov管测量气体分布器上方壁面附近的液速波动信号,发现液速标准差和时均液速随射流速度的增大均依次出现第一平稳段、上升段、下降段和第二平稳段,其中,第一平稳段对应气泛状态,上升和下降段对应载气状态,第二平稳段对应完全分散状态。据此提出了临界射流速度的判断准则：第一平稳段与快速上升段的交点对应的射流速度为泛点射流速度u _jf,下降段与第二平稳段的交点对应的射流速度为完全分散射流速度u _jcd。与目测法相比,液速标准差分析得到的u _jf的平均相对偏差为5.82%,u _jcd的平均相对偏差为18.2%;时均液速分析得到的u _jf的平均相对偏差为5.86%,u _jcd的平均相对偏差为12.1%。研究还发现泛点射流速度随表观气速的增大而增大。