筛型塔板在喷射及混合状态操作下三相传质性能

以空气-水-油(煤油及白油)为介质在600mm×150mm矩形冷模塔内测试了筛型塔板气液液三相传质性能。研究喷射及混合状态下,气速、液流强度、油水比等操作条件和塔板结构参数(孔径、开孔率)对塔板效率的影响。气膜和液膜控制的2种物系的实验表明,三相传质的板效率在喷射状态下明显高于混合状态。对测试数据进行关联,获得适用于喷射及混合状态下三相传质板效率的估算式。     

汽-液-液三相蒸馏导向筛板的流体力学性能研究

本文以空气—水—煤油为介质,在600×l50矩形冷模塔内进行了气—液—液三相蒸馏导向筛板的流体力学特性的研究.实验就三相蒸馏塔板上的操作工况(Operating Regimes)及塔板上两液相混合状况进行了研究.并就清液高度、雾沫夹带、板压降等主要流体力学参数进行了大量测试,提出适用于混合工况的主要流体力学参数计算关联式.     

喷射型催化精馏塔构件的流体力学性能

对垂直筛板帽罩内装催化剂构成的新型塔构件进行了实验研究。考察了板孔动能因子、催化剂藏量、床层空隙率对塔构件压降、罩体喷出量以及液泛和漏液速度的影响。结果表明:压降随板孔动能因子和催化剂藏量的增加而增大,随床层空隙率的增加而减小;罩体喷出液体量随着板孔动能因子的增加先增大后减小,随床层空隙率的增加而增大,随催化剂藏量的增加而减小;漏液速度随液体流量、藏量的增加而增大,随空隙率增大而减少;液泛速度随床层空隙率、液体流量的增大而减小,随藏量增加而增大。新型塔构件流体力学性能良好。     

喷射工况下筛板流体力学特性研究

利用总板压降在喷射和鼓泡工况下具有不同的变化规律。测定了筛板上流动工况的转相点。分析了气速、液体负荷、孔径、开孔率以及堰高等因素对相转换的影响。测定了喷射工况下筛板流体力学特性,得出塔板压降、持液量、雾沫夹带量等参数的关联式。     

喷射环流三相流化床反应器轴向液速分布的研究

在喷射环流三相流化床反应器中，应用本文所开发的内热式热膜流体速率探头，获得了带有沉降分离区的夹套式环流反应器在不同压力、气量、流量条件下，不同轴向位置的液体速率分布规律。对于本文所述这类反应器，喷射区流体运动速率最大；自喷口向上，速率先是随距离的增大易急骤下降，然后逐渐向一渐近点逼近；当进入环隙转折口处时，由于气体的逸出及流道的变化液速急骤下降；凝固相进入环隙时，液速随距离的变化也存在渐近点。当采用变径结构时，流道面积突变处的液速变化率仅次于喷射入口区。在环流反应器中，液速主要取决于喷射动能及气提推动力，受液体进料量及压力的影响较小。     

利用计算流体力学及计算传质的方法研究精馏塔传质效率

It has long been found that the flow pattern of the liquid phase on distillation tray is of great importance on distillation process performance. But until now, there was very few published work on quantitative investigation of this subject. By combining the computational fluid dynamics (CFD) with the mass transfer equation, a theoretical model is proposed for predicting the details of velocity and concentration distributions as well as the tray efficiency of distillation tray column. Using the proposed model, four different cases corresponding to different assumptions of liquid and vapor flowing condition for a distillation tray column were investigated. In Case I, the distributions of velocity and concentration of the incoming liquid from the downcomer and the uprising vapor from the underneath tray spacing are uniform. In Case Ⅱ, the distribution of the incoming liquid is non-uniform but the uprising vapor is uniform. In Case Ⅲ, the distribution of the incoming liquid is uniform but the uprising vapor is non-uniform.In Case IV, the distributions of both the incoming liquid and the uprising vapor are non-uniform. The details of velocity and concentration distributions on a multiple sieve tray distillation column in four different cases were simulated using the proposed model. It is found that the shape of the simulated concentration profiles of vapor and the liquid is quite different from case to case. The computed results also show that the tray efficiency is highly reduced by the maldistribution of velocity and concentration of the incoming liquid and uprising vapor. The tray efficiency for Case Ⅰ is higher than Case Ⅱ or Case Ⅲ, and that for Case Ⅳis the lowest. It also reveals that the accumulated effect of maldistribution becomes more pronounced when the number of column trays increased. The present study demonstrates that the use of computational method to predict the mass transfer efficiency for the tray column, especially for the large one, is feasible.     

喷射环流生物反应器性能及处理染料废水的研究

对气液固三相喷射环流生物反应器中液体流速进行了测量,得到了不同操作压力,气本进料量和液体进料量下液速的分布规律。结合这种高效的喷射环流生物反应,采用活性污泥法对碱性绿染料废水的降解过程进行了研究。     

筛板喷射工况下的雾沫夹带

以空气／水为物系，对筛板上泡沫和喷射两种工况下的雾沫夹带进行了实验测量，依据喷射工况下雾沫夹带量随气液流量变化的规律，提出了喷射强度的概念及其定量表示，发现喷射工况存在一般喷射和强烈喷射两个状态，并对一般喷射状态下的雾沫夹带进行了新法关联。     

三相内循环流化床的流体力学研究

以活性碳、陶瓷颗粒、小米为固体粒子,采用体积膨胀法测定气含率,分别考察了气体速度、固含率、粒子种类三个因素对气含率的影响.结果表明:气含率随着气体速度和固含率的增大而增大,但却不能无限的增大.选用小米做固体粒子时在相同气速下的气含率最大.     

大孔筛板流体力学性能研究

本文测定及研究了大孔筋板(孔径为 5、10、15、20及25mm)流体力学参数,提出计算塔板压降、漏液点气速、零沫夹带量及泡沫层高度的一套设计关联式,其精确度可满足工程设计的需要.文中还对大孔筋板的操作性能及弹性范围进行了分析讨论.对于塔板结构参数设计得当的大孔筛板,操作弹性比达到2—4左右,足可适应一般工业装置的负荷波动要求.     

Efficiency of Distillation Columns Containing Packed Sieve Trays

Abstract

The Murphree efficiency of the fifth tray in a six-sieve tray distillation column, 7.8 cm in diameter and 85 cm high, was increased from 37.5 to 90% when three disks of a wire mesh pad, 9 cm high, were placed on the tray. An acetone-methanol test system was used in this investigation. The pressure drop across the tower corresponding to this packing increased by 33%. Nine disks of Raschig rings of similar height increased the tray efficiency to 75% and the pressure drop by 16%. A model was used for the azeotropic system, and the overall tower efficiency was found to increase by about 20% due to the presence of packing on a single tray.     

筛板由泡沫态到喷射态工况转变点的测定和模拟

The transition from froth to spray regime on sieve trays was experimentally studied in an air/water simulator with 300 mm diameter. It has been found that the regime transition occurs as the cleax liquid height is equal to the residual pressure drop on the trays. A convenient and accurate technique was proposed for determination of the regime transition point. ]Based on analysis of the transition process at a sieve hole, a new formula which can be used to correlate the experimental results was provided.     

网孔塔板的流体力学

木文以空气-水系统在1200×400mm矩形装置内对网孔塔板的流体力学进行了试验研究。试验所采用的塔板参数和操作条件为:塔板开口宽度为3、3.5、4、4.5及4.7mm;塔板开孔率为9.9、12.3、13.2、14.9及15.4％; 挡沫板宽度为150、200、250、300mm;板间距为400、500、600、700及800mm;液流强度为20、30、45、60m~3/m·h;气体空塔速度为0.60—2.8m/s。测定了各有关参数对塔板压降、雾沫夹带和泄漏的影响,并对试验数据进行了关联,得出了计算塔板压降、雾沫夹带、泄漏、上限气速、下限气速及操作弹性等的关系式,以便用于网孔塔板的设计。     

Fluid Mechanics of Distillation Trays (II): Prediction of Flow Fields on Some Practically Important Sieve Trays

Abstract

Separation processes account for 6% of the annual US energy expenditure, 50% of which is consumed by distillation alone. Therefore, it is not too surprising that distillation, the work horse of the chemical process industry, is under attack by emerging technologies based on membranes and adsorption, whose proponents claim enormous potential savings in energy expenditure. Moreover, the massive scale of use plus the energy intensiveness implies that even small improvements in the efficiency of distillation processes can result in large gains in energy savings. Such improvements can come from developing a fundamental understanding of the fluid mechanics of tray columns, which has heretofore been lacking and is the subject of this paper. The flow on a distillation tray is governed by the equations of mass and momentum conservation in three-dimensions. These equations are reduced here to a set of two-dimensional equations by averaging them across the depth of the fluid film flowing across the tray. The depth-averaged equations are then solved by a Galerkin/finite element technique. The evolution of film height and flow fields are determined for three types of trays that are commonly found in the laboratory and in actual plants: rectangular trays, circular trays, and so-called race track trays. Sample results include development and growth of eddies or zones of recirculation on various types of trays, variation of film height with position on a tray, and effect of tray geometry, flow rate, and physical properties on tray holdup. Occurrence of eddies and large height variations on trays can have detrimental consequences in vapor-liquid contacting operations. Therefore, the new rigorous computations should prove indispensable in developing column designs that avoid or minimize them.     

喷射状态下大孔径复合筛板塔中的液滴分布

The droplet size distribution with large-holed compound sieve tray operating in the spray regime is measured by using a double electrical probes technique in a cold model column of 400 mm diameter. The results indicate that the hole F-factor Fo and surface tension are the main factors which influence the liquid dispersion expressed by the Sauter mean diameter D32. A correlation of D32 on surface tension, viscosity, F-factor, weir height and liquid flow rate is proposed.     

Identification of Phase Inversion on Sieve Trays

The fundamental differences in hydrodynamics of the froth and spray regime account for the ongoing interest in search for the point of phase inversion. This short communication presents a new approach for identification of phase inversion on sieve trays in terms of an image-based measurement technique. Image analysis of entrained droplets reveals a distinct increase in Sauter mean diameter and droplet frequency during phase inversion. Further measurement methods like pressure drop, gravimetric analysis of entrained liquid, froth height assessment and photographic observation of the flow regime serve as a reference value and complement the discussion. A flow map based on the experimental data comprises each regime and shows a good agreement with phase inversion correlations from literature.