Computational Fluid-dynamics of Liquid Phase Flow on Distillation Column Trays

The liquid flow on a single-pass sieve distillation tray is simulated with a three-dimensional computational fluid dynamics (CFD) program with the K-ε turbulence model. In the model, a source term SMi is formulatedin the Navier-Stokes equations to represent the interfacial momentum transfer and another term Sc is added to themass transfer equation as the source of interfacial mass transfer. The simulation provides the detailed informationof the three-dimensional distribution of liquid velocity on the tray, the circulation area and the concentration profilealong the height of liquid layer.

Characteristics of Trays Using Inertial Separation Technology

Though they look very different,UOP SimulFlowTM,Koch-Glitsch Ultra-FracTM,Jaeger CoFloTM and Shell ConSepTM trays fall into the same category of trays using inertial separation technology. However,flooding mechanisms and the trends of entrainment and efficiency are different due to their different working principles. This paper provides a detailed analysis of these trays using available information from literature and U.S. Patents. Efforts are also made to interpret the observations reported. In terms of tray efficiency,it is found that SimulFlow,Ultra-Frac and CoFlo trays are typical point efficiency devices due to a completely mixed liquid pool on the tray deck,while ConSep trays can take advantage of liquid concentration gradient on the tray deck,which makes this tray at-tractive among all ultra high capacity trays.

Computational Fluid-dynamics of Liquid Phase Flow on Distillation Column Trays

A computational fluid-dynamics model is presented for predictingthe two-phase two-dimensional liquid phase flow on a distillationcolumn tray based on the modification of Navier-Stokes Equation byconsidering both the resistance and the enhanced turbulence createdby the uprising vapor. Experimental measurement of the local liquidphase velocity on an air-water simulator of 1.2 m in diameter byusing the hot film anemometer is briefly described. Two of theconventional fluid-dynamic constants are readjusted for the case ofliquid flow on a tray by fitting the experimental data.

Effect of Structural Parameters on the Performance of NS High-efficiency Composite TraysⅠ.The Effect of Aperture and Opening Ratio on NS High-efficiency Composite Trays

In this paper,the structure and characteristics of the NS high-efficiency composite trays based on the doublelayer aperture jet sieve plate and compositely structured packing were investigated.The effect of aperture and opening ratio of plate on the fluid dynamics of the NS high-efficiency composite trays,such as the dry tray pressure drop,the wet tray pressure drop,the entrainment,the froth height,the leakage and mass transfer characteristics,were investigated.As a result, the low pressure drop,the high efficiency and the high capacity are the main advantages of the NS high-efficiency composite trays compared to other types of trays.According to this study,small aperture is useful for reducing the pressure drop and entrainment with a high mass transfer efficiency;while large aperture can achieve high capacity and efficiency in a broader operating range at the same pressure drop and entrainment.

Directed Valve Trays

1 INTRODUCTIONValve tray columns are one of the most important mass transfer equipment for vapor-liquidoperations and are widely used in the petroleum and chemical industries.They have good op-erating performances with floatable parts on the trays.There are various of valve trays,andType V1(F1-type)valve trays are used very common in industry.Though Type V1 valvetrays have a number of advantages,it has been found in recent years that there are also cer-tain drawbacks,for example,higher hydraulic gradient on the tray,more backmixing

Identification and Modeling of Froth to Spray Transition on Sieve Trays

The transition from froth to spray regime on sieve trays was experimentally studied in an air/water simulator with 300mm diameter. It has been found that the regime transition occurs as the clear 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.

Formula for Determining Number of Basic Seedlings at Scattered-Planting with Seedling Dry-Raised on Plastic Trays in Double-Season Rice

The tiller emergence in seedling nursery beds and field, and panicle formation in the field were investigated under scattered-planting with seedling dry-raised on plastic trays in double-season rice. A significant difference was noted in the non-synchronously-emerged tillers （the tillers that formed from latent buds and did not emerge following the normal tillering law on seedling nursery beds and recovered to grow after scattered-planting or transplanting） as well as the percentage of the available synchronously-emerged tillers between seedlings raised on plastic trays under dry-land conditions （DPT） and seedlings raised on nursery beds under wetland conditions （WB）. The seedlings under DPT had some non-synchronously-emerged tillers, but those under WB had not. Therefore, the traditional formula for determining the number of rice seedlings was improved, and the formula for determining the number of basic seedlings under scattered planting with DPT in double-season rice was introduced. For early rice, it was X=Y/{（I＋t1r1）[1＋（N-n-SN）Rr2]＋（SN-3-t1）R2r5}, and for late rice, it was X=Y/{（1＋t1r1）[1＋（N-n-SN）Rr2]＋（N-n-SN-3）Rr2R1r3＋（SN-3-t1）R2r5}. Where, X represents reasonable number of basic seedlings per unit area at scattered-planting; Y, number of fitting panicles per unit area; t1, total number of tillers per plant; r1, percentage of the total available tillers; N, total number of leaves of the main culm; n, total number of elongated internodes in the main culm; SN, seedling leaf ages at scattered-planting; R, percentage of the primary tillers emerged in available node-position; r2, percentage of the available primary tillers; R1, percentage of the secondary tillers in the field （except the secondary tillers of the seedlings）; r3, percentage of the available secondary tillers; R2, percentage of the asynchronously-emerged tillers after scattered-planting; r5, percentage of the available non-synchronously-emerged tillers after scattered-planting.

Establishment and Growth of Potato Micro-Cuttings in Sand Trays

Two separate experiments were conducted to evaluate the success of the establishment and growth of micro-cuttings of potato (5 - 6 cm tall) in sand trays [38 cm (L) × 28 cm (W) × 7.5 cm (H) plastic trays] under controlled environment (22?C ± 2?C, 60 - 75 μmosm–1?s–1 light energy for 16 h daily). In the first experiment, micro-cuttings of potato cv. Diamant were planted at six populations (500, 600, 700, 800, 900 and 1000 cuttings per tray) in treated sand (sun dry, 1% formaldehyde, 0.2% Dithane M-45 and control). The mortality percentage of micro-cuttings was nil for sun dry sand while formaldehyde and dithane M-45 treated sand had 1% - 4% against 15% in the control with the highest population density. Mortality of micro-cuttings in formaldehyde and dithane M-45 treated sand trays were found not to be related to pathogenic organism rather toxic effect of these two chemicals. Micro-cuttings in Sun dry and control treatments showed better growth performance than these in chemically treated sand trays. In the second experiment, urea @ 1, 2 and 3 g per tray was applied as solid form after 15 days of planting the micro-cuttings and as liquid form @ 0.5, 1 and 2% solution sprayed in the micro-cuttings repeatedly after 15, 30, 45 and 60 days of planting. The micro-cuttings which received urea as solid state died within 2 - 3 days and 2% urea solution was also detrimental. Urea solution @ 0.5% found to be very effective for vegetative growth of micro-cuttings in sand trays. The control was also good for vegetative growth but at a slower rate.

Effects of Different Planting Densities on the Yield of Rice Developed from Seedlings Dry Raised in Plug Trays

[Objectives]This study was conducted to investigate the effects of different planting densities on rice tillering dynamics and yield. [Methods]The effects of different planting densities on rice yield were studied based on seedlings dry raised in plug trays. [Results]Planting density had obvious effects on tillering dynamics,number of panicles per unit area,number of grains per panicle and rice yield under the condition of seedlings dry raised in plug trays. Comprehensive analysis showed that the row spacing × hill spacing = 25 cm × 14 cm,that is,the planting density of 2. 85 × 10~5 hills/hm^2,achieved the highest yield,at 9 960 kg/hm^2. [Conclusions]This study provides a scientific basis for optimizing rice cultivation techniques and achieving high yield and high efficiency in rice production.

Quantitative Analysis of Frosting Characteristics on the Drip Tray of A Cryogenic Valve for LNG Ships

Cryogenic valves play a crucial role in the production and transportation of liquefied natural gas(LNG),and are primarily responsible for efficiently controlling the inflow and outflow of LNG and regulating pressure.However,due to their operation in low-temperature and high-humidity environments,crucial components such as drip trays are susceptible to frosting,which may lead to LNG leakage,thereby causing severe safety incidents.In this study,the user-defined function(UDF)is employed to redevelop Fluent,which integrates the frost growth model with the Eulerian multiphase flow model,to conduct a quantitative analysis of frosting on drip trays of cryogenic valves.The effects of environmental parameters,such as wind speed,ambient temperature,air humidity,and cold surface temperature on the growth of the frost layer were analyzed.This study reveals a limiting wind speed between 1 m/s and 2 m/s.Upon reaching this limit speed,the growth of the frost layer reaches its maximum,and further increases in the wind speed have no significant effect on the growth of the frost layer.Furthermore,the influence of the change in the flow field on droplet impingement and freezing during the growth of the frost layer is considered through the coupling method of the kinematic characteristics of water droplets and the collection coefficient of water droplets.This study identifies the influence of different parameters on the droplet impact efficiency,leading to the modification of the frost layer on the drip tray.

一种Tray装产品镭雕Logo的设备设计

本文阐述一种Tray装产品镭雕Logo的设备结构设计,Logo镭雕是一种加工方式,将汽车企业的标志、名称、图案、产品信息等,通过激光镭射技术刻在产品的外形上,达到立体浮雕的效果。镭雕技术在汽车行业内应用广泛,如:安全带、车钥匙、汽车灯具、汽车音箱、摄像头、行车记录仪、蓄电池等。本设计的核心结构包括:前/后Tray盘上下料结构、整Tray产品翻转结构、Tray盘定位/移动结构、镭雕机结构、CCD检测结构等。该设备可实现Tray装产品自动上下料、自动翻转以实现产品正反面镭雕、CCD对单个产品自动补偿定位、CCD目检的功能,生产效率高,质量好,更换产品方便,适应性强。

DOWNCOMER MIXING AND ITS EFFECT ON DISTILLATION TRAY EFFICIENCY

In this paper, the measurement of liquid mixing in a downcomer of segmental type of distillation column is presented. The extent of liquid mixing is calculated by means of a mixing pool model. The results indicate that liquid mixing in a downcomer is actually incomplete. It is a significant correction to the assumption of complete downcomer mixing or no downcomer mixing which is generally adopted in many distillation calculations. Besides, the present results are used in a two dimensional eddy diffusion model to calculate the distillation tray efficiency. It is shown that the assumption of complete downcomer mixing is closer to the actual situation than that of no downcomer mixing.

Research on Potted-Tray Grown Rice Seedling Transplanting by Machine

[Objective] In order to cultivate seedlings that are adaptable to farming system and transplanter, the technology for transplanting potted-tray grown rice seedlings with machine was introduced and studied. [Method] The transplanter-spe-cific seedlings were cultivated with potted-tray, bowl-shaped blanket tray and soft plastic flat plate respectively. The seeding rate and 20-50-day-old seedling height were investigated for the 3 sowing patterns. After the transplanting, the missing transplanting rate, upright seedling rate, seedling injury rate and green-returning pe-riod were investigated. [Result] Nursing seedlings with potted-tray had the advan-tages of saving seeds, high sowing precision, high seedling rate and high seedling rate. The 20-40-day-old seedlings had relatively high leaf age, seedling height and root number. However, 40 d after the transplanting, the growth of seedlings was slowed. The quality difference was smal est among the 20-day-old seedlings that were nursed with 3 different patterns, but since then the quality advantage of pot-ted-tray grown seedlings had been more and more prominent. There was smal dif-ference in quality among the 30-day-old seedlings. However, for the seedlings that were older than 40 d, the transplanting quality of potted-tray grown seedlings was higher than that of bowl-shaped blanket tray grown seedlings and soft plastic flat plate grown seedlings. In addition, the green-returning period of the potted-tray grown seedlings was significantly shortened. [Conclusion] Compared to the bowl-shaped blanket tray grown seedlings and soft plastic flat plate grown seedlings, the potted-tray grown seedlings were more suitable to transplant by machine in the wheat-rice double cropping areas of Chengdu Plain.

A Novel SiC Foam Valve Tray for Distillation Columns

The novel SiC foam valve tray was made of thin slices of SiC foam material with a high specific surfacearea. Hydrodynamic performances of the novel SiC foam valve tray were studied with air-water system at atmos-pheric pressure. These performance parameters included pressure drop, entrainment, weeping and clear liquidheight. The mass transfer efficiency of the SiC foam valve tray was measured in laboratory plate column. Comparedwith the F1 float valve tray, the dry pressure drop was decreased about 25%, the entrainment rate was about 70%lower at high gas load, the weeping was much better, and the mass transfer efficiency was far higher. Thus, theoverall performance of the novel SiC foam valve tray was better than that of F1 float valve tray.

SIMULATION OF TWO DIMENSIONAL LIQUID PHASE FLOW ON A DISTILLATION TRAY

A mathematical model describing the two dimensional liquid phase flow on a tray is presented, in which the k-ε model of turbulent flow was adopted with consideration of the rising vapor as a resisting force. The calculated results show that the theoretical prediction is in agreement with the experimental measurement.

Hydrodynamics performance and tray efficiency analysis of the novel vertical spray packing tray

Column setup has been widely utilized in the petroleum and chemistry industries. However, with the fast progress of industries and the increasingly serious energy shortage, designing a new column setup with better performance and higher capacity becomes more urgent. In order to improve column's capacity and expand operating condition, a new type of column tray named novel vertical spray packing(NVSP) tray was designed and experimented. The performances of the novel tray, including pressure drop, weeping, entrainment and tray efficiency, were tested in a plexiglass column. In addition, performances of the novel tray were compared with that of the sieve tray and the Glitsch V1 valve tray. Based on the experiment data, the mathematical correlations of pressure drop, weeping and entrainment for the novel tray were established by regression analysis method. A fundamental model of dry pressure drop of the novel tray was promoted at the form of sum mode. The results indicate that the novel tray has wider operating condition and better performance.

Bubble Formation Characteristics from a Sieve Tray with Liquid Cross-flow

An apparatus, designed to simulate bubbling of sieve tray operatedin froth regime, was employed. Bubble contact angles in and above theincipient weeping regime for an air-water-plexiglas system wereinvestigated. The influence of both liquid cross-flow and gas up-flowupon bubble contact angles was examined. A model consider- Ing theinfluence of liquid cross-flow was developed to predict bubble sizefrom a sieve hole in froth operation regime. The comparison showsthat the bubble sizes predicted by the present model are consistentwith our experimental Values and the available published experimentaldata.

CFD gas–liquid simulation of oriented valve tray

Computational fluid dynamics(CFD) has recently emerged as an effective tool for the investigation of the hydraulic parameters and efficiency of tray towers.The computation domain was established for two types of oriented valves within a tray and meshed into two parts with different grid types and sizes.The volume fraction correlation concerning inter-phase momentum transfer source was fitted based on experimental data,and built in UDF for simulation.The flow pattern of oriented valve tray under different operating conditions was simulated under Eulerian-Eulerian framework with realizable k-ε model.The predicted liquid height from CFD simulation was in good agreement with the results of pressure drop and volume fraction correlations.Meanwhile,the velocity distribution and volume fraction of the two phases were demonstrated and analyzed,which are useful in design and analysis of the column trays.

The Analysis of Distillation Tray Column Efficiency by Fluid Dynamics and Mass Transfer Computation

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 n, the distribution of the incoming liquid is non-uniform but the uprising vapor is uniform. In Case HI, 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 Ⅳ is 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.

SIZE DISTRIBUTION OF DROPLETS ABOVE A ROTATING STREAM TRAY AND MODEL OF DROPLET MOTION THEREIN

Droplet size distributions have been investigated with a two-probe system above a rotatingstream tray of 300 mm diameter.The measured distributions are found to follow the upper limitedlognormal distribution with three parameters dependent primarily on gas hole F-factor.A probabilitymethod is used to describe the initial state of the droplet population above the tray,and a model fordroplet motion is presented.The results computed with model agree well with experimental data.