Ž. Olujić

A corrugation geometry based model for efficiency of structured distillation packing

Abstract Although the structured packing is a well established gas–liquid contacting device, the understanding of its function is insufficient and often leads to poor exploitation of the available phase separating potential. This is a consequence of a rather superficial approach to modelling the packing performance through the years resulting in a lack of information on the nature and extent of interaction between counter-currently flowing gas and liquid phases and the micro and macro geometry of a rather ordered structure with a pronounced flow discontinuity at the transition among packing elements. This paper addresses the relation between the fluid-dynamics imposed by packing geometry and the mass transfer efficiency, and introduces a performance prediction method which does not require packing specific constants to describe mass transfer coefficients of phases.

Effect of Column Diameter on Pressure Drop of a Corrugated Sheet Structured Packing

The results of an experimental study indicating a significant effect of column diameter on the pressure drop and capacity of corrugated sheet structured packing are presented. The experiments were carried out with Montz-pak B1-250, using an air/water system at ambient conditions in perspex columns with internal diameters of 0.2 m, 0.45 m, 0.8 m and 1.4 m. The results clearly show that both the pressure drop increase and capacity decrease become significant when the column diameter approaches the value equal to that of the height of a packing element. This observation suggests that column diameter(s) based on small scale data can be too large.

Influence of corrugation geometry on the performance of structured packings: an experimental study

Abstract While the utilisation of corrugated sheet structured packings is well established, these gas–liquid-contacting devices are still not well understood. A contributing reason is the rather limited publicly available performance data, most of which have been obtained from relatively small columns. A recent comparison of data from the 1.2 m Fractionation Research, Incorporated (FRI) and from the 0.43 m Separations Research Program (SRP) columns show excellent agreement based on equivalent packings. This is significant since the FRI column is considered to be of industrial scale. As a result, we sought to create an expanded data base emphasising packing geometric variations, using packings from a single manufacturer (J. Montz). Hydraulic characteristics of the same packings had been studied previously using air–water simulators at TU Delft. Total reflux distillation experiments were carried out at SRP using a bed height of 3.3 m for all packings. The cyclohexane– n -heptane system was utilized because of the availability of comparative data. The operating pressure was varied from 0.33 to 4.14 bar, to determine the effect of physical properties. The resulting data provided insight into the nature and effect of corrugation angle, specific surface area, and surface texture on pressure drop, capacity and efficiency. In this paper we report the results and also discuss the implications of the observations on model development and design.

Performance characteristics of a new high capacity structured packing

Total reflux distillation results of a comprehensive experimental study are reported for a new generation of Montz high capacity structured packings. The major feature of the Montz B1-M® series is a smooth bend in the bottom third of the corrugation with continuously increasing corrugation base width. A comparison is made with the performance of conventional structured packing under the same test conditions. The relationships between specific surface area, pressure drop, capacity, and separation efficiency are discussed.

Experimental characterization and computational fluid dynamics simulation of gas distribution performance of liquid (re)distributors and collectors in packed columns

The usability of a state of the art computational fluid dynamics simulation package as a tool for analyzing the fluid-dynamic performance of internals encountered in packed distillation columns, such as initial gas distributors, liquid distributors and liquid collectors is demonstrated. A 1.4 m internal diameter column hydraulics simulator was used to provide detailed experimental evidence on the gas distribution pattern imposed by various types of column internals. The comparison of measured and predicted profiles for single-phase gas flow conditions indicates a strikingly good agreement.

Experimental Studies on the Interaction Between the Initial Liquid Distribution and the Performance of Structured Packings

Abstract Distillation and hydraulic test data are reported which give insight into the effect of the quality of initial liquid distribution on the performance of two corrugated sheet metal structured packings, differing considerably in surface area and texture. As expected, the packing with the larger surface (Montz-Pak BS-450) is more sensitive to initial liquid maldistribution. From the packing with smaller surface (Ralu-Pak 250 YC) a good performance may be expected even with only 40 drip points/sq m.

Modelling and measurement of gas flow distribution in corrugated sheet structured packings

Abstract A mathematical model and calculation procedure are developed for the gas flow distribution in channels formed between tightly packed, corrugated, unperforated metal sheets. The model is a discrete cell model based on averaged mass, momentum and energy balance equations for each of numerous crossings of gas flow channels, with characteristic friction factors for gas inlet, bulk zone and wall zone as model parameters, which can be easily obtained from pressure drop measurements for each type and size of structured packing. The model enables prediction of velocity profiles leaving an element or packing layer consisting of segments of unperforated, structured packing. It is also suited for perforated packings which under operating (wetted) conditions function as a closed surface packing.

PERFORMANCE EVALUATION OF A CONVENTIONAL NAUTAMIXER APPLIED AS A DIRECT DRYER

Abstract This paper describes the experiments which were conducted with the objective to determine the potential of a conventional Nautamixer applied as a direct dryer. This convective Nautamixer-dryer was used for drying the urea nitrate containing around 15% of water, which is converted from a pasteous form into a powder of a moisture lewel below 1%. The influence of the following variables was studied: increased hot air velocity and temperature, number of revolutions of the agitator, and mass of the drying material. The effect of inlet air distribution to the periphery of the bed of the material was studied with a perforated plate distributor by blanking the holes (17%). which adversely affected the drying rate. The examination of the effect of external heating through the wall indicated that it is not possible to achieve the desired moisture level of the product without the introducing the flowing hot air. As an addition to the convective drying the indirect drying contributed more to the increase of ...

Types of Distillation Column Internals

There are basically two different types of distillation column internals: those whose principal role is to create sufficient interfacial area and ensure within given contact times the intimate and intensive contact of vapor and liquid, and those belonging to ancillary equipment that enables both smooth functioning of the former and the operating column as a whole. Detailed accounts on trays, random packings, and structured packings are given in separate chapters (Chapters 2 to 4); the present chapter provides a concise description of generic aspects and addresses in greater detail relative performance characteristics of these particular devices.

PERFORMANCE EVALUATION OF A CONVENTIONAL NAUTAMIXER APPLIED AS A DIRECT DRYER - EMPIRICAL MODEL

ABSTRCT This paper is the second part of (1)and it shows an attempt to define a suitable model, which would make it possible to predict the drying rate for pastelike and bulk materials in a conventional Nautamixer applied as a direct dryer. As it was shown in (1), (2), (3) all influential variables were studied, and from the results it can be seen that the system is highly complex. By means of system simplification an empirical model is defined, suitable for drying rate calculation for this type of dryer, in the accuracy range of ±25%. For the practical purpose, it seems that this simple model offers a reliable starting point for drying process design for similar systems.