Distillation columns structured packing

The older tall oil distillation columns used bubble cap trays. In new columns, structured packing is preferred. Because of the low pressure drop of structured packing, steam injection is no longer necessary. The low liquid holdup of this packing minimizes the reactions of the fatty and resin acids. A specific distillation sequence for vacuum columns using structured packing of Sulzer has been described (26). Depitching is carried out at a vacuum of... 

The catalytic distillation section uses a zeolite catalyst that is packaged into specially engineered bales. The catalyst bales function similarly as typical column structured packing and are designed to optimize both the distillation and the chemical reaction processes that occur in this portion of the alkylator. ... 

As in distillation columns, a packed column contains small packing elements dumped into the column in a random fashion, and these elements can provide the needed intimate contacting of the descending liquid and the rising gas or vapor. Packings of an ordered, or structured, form are rarely if ever used for absorption or stripping. 

For specific final performance sizing of a distillation column using Norton s Intalox structured packing the designer is referred to the manufacturer s technical representatives, and should not assume the preliminary results obtained from any manufacturer s bulletin included here will necessarily serve as a final design. As a preliminary examination of a design problem (used by permission of Norton Chemical Process Products) ... 

Hufton, J. R, J. L. Bravo, andj. R. Fair, Scale-up of Laboratory Data for Distillation Columns Containing Corrugated Metal-type Structured Packing, Ind. and Eng. Chem. Res., American Chem. Soc., V. 27, No. 11 (1988) p. 2096. 

Reactors with a packed bed of catalyst are identical to those for gas-liquid reactions filled with inert packing. Trickle-bed reactors are probably the most commonly used reactors with a fixed bed of catalyst. A draft-tube reactor (loop reactor) can contain a catalytic packing (see Fig. 5.4-9) inside the central tube. Stmctured catalysts similar to structural packings in distillation and absorption columns or in static mixers, which are characterized by a low pressure drop, can also be inserted into the draft tube. Recently, a monolithic reactor (Fig. 5.4-11) has been developed, which is an alternative to the trickle-bed reactor. The monolith catalyst has the shape of a block with straight narrow channels on the walls of which catalytic species are deposited. The already extremely low pressure drop by friction is compensated by gravity forces. Consequently, the pressure in the gas phase is constant over the whole height of the reactor. If needed, the gas can be recirculated internally without the necessity of using an external pump. 

Random packings are also used they are the same as those used in packed distillation and absorption columns. The properties of random packings are given in Table 11.3. Proprietary structured packing are also used. 

Fair, J. R. and Bravo, J. L. (1990) Chem. Eng. Prog. 86, (1) 19. Distillation columns containing structured packing. 

Tray columns are the best choice for high-pressure distillation, especially above 20 bar. An important factor in trays favour is that they have been used for many years in high-pressure distillation, while it is only in the last 10-15 years that packings have been used significantly in such duties, and especially for structured packings above about 15 bar. 

J.L. Bravo, J.A. Rocha and J.R. Fair, Distillation columns containing structured packings- A comprehensive model for their performance mass transfer model, Lnd. Chem. Res., 35 (1996) 1660-1667. 

Fair. J.R. and J.L. Bravo Distillation Columns Containing Structured Packing, ... 

Fixed-bed catalytic reactors and reactive distillation columns are widely used in many industrial processes. Recently, structured packing (e.g., monoliths, katapak, mella-pak etc.) has been suggested for various chemical processes [1-4,14].One of the major challenges in the design and operation of reactors with structured packing is the prevention of liquid flow maldistribution, which could cause portions of the bed to be incompletely wetted. Such maldistribution, when it occurs, causes severe under-performance of reactors or catalytic distillation columns. It also can lead to hot spot formation, reactor runaway in exothermic reactions, decreased selectivity to desired products, in addition to the general underutilization of the catalyst bed. 

L. Spiegel, W. Meier, Distillation columns with structured packings in the next decade, Chem. Eng. Res. Des. 81 (Al) (2003) 39-47. 

Figure 8 (a) Schematic of an RD column filled with catalytic internals CD TECH (1—catalytic balls, 2—feed, 3—distillate, 4—bottom product, 5—sieve tray) and (b) catalytic structured packing Sulzer Katapak-S. (Part a from Ref. 52.)... 

Rocha JA, Bravo JL, Fair JR. Distillation columns containing structured packings— 2. Mass transfer model. Ind Eng Chem Res 1996 35 1660-1667. 

Ellenberger J, Krishna R. Countercurrent operation of structured catalytically packed distillation columns pressure drop, holdup, and mixing. Chem Eng Sci 1999 54 1339-1345. 

Distillation has traditionally been carried out in trayed columns. However, more and more frequently, additional distillation capacity is being achieved with existing trayed columns by replacing all or some of the trays by structured packing. The choice between a packed column and a tray-type column is based mainly on economics when factors of contacting efficiency, loadability, and pressure drop must be considered. 

The proposed modeling approach has been validated for distillation of non-reactive mixtures. For this purpose, the use is made of the total reflux distillation data for the binary mixture chlorobenzene/ethylbenzene (CB/EB) and ternary mixture methanol/acetonitrile/water (MEOH/ACN/WATER) obtained by Pelkonen (1997) as well as for the ternary mixture methanol/ethanol/water (MeOH/EtOH/WATER) measured by Mori et al. (2006). The experiments of Pelkonen (1997) were carried out in a column of 100 mm diameter, equipped with Montz-Pak A3-500 structured packing. The measured concentrations, temperature and flow rates at the condenser outlet are used as input values for simulations. 

Up to now, the proposed model has been validated using the total reflux distillation data in the column equipped with the Montz-Pak A3-500 and Montz-Pak B1-250 structured packings. A very good agreement between the calculated and experimental data for binary and ternary mixtures is found. 

Olujic, Z. Development of a complete simulation model for predicting the hydraulic and separation performance of distillation columns equipped with structured packings. Chem. Biochem. Eng. Q. 11, 31-46, 1997. 

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