Column Scale-Up

The reason b is approximately proportional to and decreases only slightly with column scale-up in recirculation flow (cf. Fig, 14) is explained from Eq. (3-25) by including the behavior of Ms and which are discussed in the next section. 

A pilot study was performed by Bilello and Singley (3) using a 15 in. (38.1 cm) diameter PVC column, scaled up from a 6 in. (15.2 cm) column used in earlier studies. The effects of varying the air-to-water ratio, tower height, packing material, and temperature were studied. Good correlation between data obtained by each column was observed. 

The principle of the Scheibel column scale-up procedure is to maintain the same stage efficiency. Therefore, the scaled-up column... 

Regarding SFF that is performed on a countercurrent column, scale-up is the more difficult because axial mixing in both phases dramatically decreases the fractionation efficiency in terms of height equivalent to a theoretical plate. At present, no reliable results have been published on column scale-up. We would recommend the following procedure, following what has been done in liquid liquid extraction ... 

The concept of theoretical plates in chromatography is described elsewhere, and is not repeated here (18,19). Pieri et al. have described the application of the theoretical plate concept to column scale-up and demonstrated its utility in scale-up of pheromone separation over silica gel (15). We have found this same approach to be useful in separations over ion exchange resins used as chromatographic supports. In essence, this approach gives an estimate of column length for a given separation if the particle size is changed. This is based on empirical correlation of the number of theoretical plates, JV, ... 

A strategy for designing and developing reactive distillation processes involves three stages feasibility analysis, catalyst and hardware selection, and column scale-up. 

Scale-up and performance of a 1.47-m Scheibel column have been reported (98,154,155), as have detailed description and design criteria for the Scheibel column (156) and scale-up procedures (157). The same stage efficiency can be maintained on scale-up, and total throughput can be increased by three and one-half times at the expense of higher HETS. As of this writing, Scheibel columns up to 2.75 m in diameter are in service. 

The rotating-disk contactor (RDC), developed in the Netherlands (158) in 1951, uses the shearing action of a rapidly rotating disk to interdisperse the phases (Eig. 15b). These contactors have been used widely throughout the world, particularly in the petrochemical industry for furfural [98-01-1] and SO2 extraction, propane deasphalting, sulfolane [126-33-0] extraction for separation of aromatics, and caprolactam (qv) [105-60-2] purification. Columns up to 4.27 m in diameter are in service. An extensive study (159) has provided an excellent theoretical framework for scale-up. A design manual has also been compiled (160). Detailed descriptions and design criteria for the RDC may also be found (161). 

The Oldshue-Rushton column (Eig. 15d) was developed (162) in the early 1950s and has been widely used in the chemical industry. It consists essentially of a number of compartments separated by horizontal stator-ring baffles, each fitted with vertical baffles and a turbine-type impeller mounted on a central shaft. Columns up to 2.74 m in diameter have been reported in service (162—167). Scale-up is reported to be reliably predictable (168) although only limited performance data are available (169). A detailed description and review of design criteria are available (170). 

Scale-Up Proceduresfor a Scheibel Extraction Column, NTIS Report No. DE3-013576, National Technical Information Service, U.S. Department of Commerce, Washington, D.C., 1983. 

Direct Scale-Up of Laboratory Distillation Ljficiency Measurements It has been found by Fair, Null, and Bolles [Ind. Eng. Chem. Process Des. Dev., 22, 53 (1983)] that efficiency measurements in 25- and 50-mm (1- and 2-in-) diameter laboratory Oldersbaw columns closely approach tbe point efficiencies [Eq. (14-129)] measured in large sieve-plate columns. A representative comparison of scales of operation is shown in Fig. 14-37. Note that in order to achieve agreement between efficiencies it is necessaiy to ensure that (1) tbe systems being distilled are tbe same, (2) comparison is made at tbe same relative approach to tbe flood point, (3) operation is at total reflux, and (4) a standard Oldersbaw device (a small perforated-plate column with downcomers) is used in tbe laboratoiy experimentation. Fair et al. made careful comparisons for several systems, utibzing as large-scale information tbe published efficiency studies of Fractionation Research, Inc. 

There are not many data on the scale-up of spray columns from pilot to industrial scale, so these types of calculations must be used for... 

The rotor speed of the scaled up tower is based on maintaining the same specific power input number as used on the pilot column it can be determined by substituting the specific values into the relationship ... 

As with the design of the other columns described above, the design of a Scheibel column must be based on pilot plant tests and scale-up, The following procedure is recommended ... 

Unhke the RDC and Oldshue-Rusnton columns where the specific throughput of the scaled-up version is the same as the pilot column, it is the characteristic of the Scheibel column that the throughput of the scaled-up column is on the order of 3-5 times greater than that acheived on the pilot column. The reason for this is that the restricted geometry of the 0.075 m diameter column limits throughput these restrictions are removed in the scaled-up columns. 

The scale-up of the Scheibel column is still considered proprietary, and therefore the vendor (Glitsch Process Systems Inc.) should be consulted for the final design. From pilot tests in 0.075-m diameter column, industrial columns up to 3 m in diameter and containing 90 actual stages have been provided. 

As with the other extractors, the final design of a Karr column depends on the scale-up from a pilot test. The following procedure is recommended. 

For scale-up up to 2 m in diameter, testing in a pilot column of 0.025 m is sufficient if the anticipated scaled-up diameter is greater than 2 m, then the pilot tests should be conducted in a 0.050-m diameter. The column should be tall enough to accomphsh the complete extraction this may require several iterations on column height. 

Z9 = plate stack height in scaled-up column df = diameter of pilot column df9 = diameter of scaled up column SPM = reciprocating speed of pilot column SPMo = reciprocating speed of scaled-up column... 

For the scaled-up column, suitable baffle plates are required to control axial mixing. For the final column layout the equipment vendor (Ghtsch Process Systems Inc.) should be consulted. 

Scale-up depends on the mechanical complexity of the crystal-transport system and techniques for removing heat. Vertical oscillating spiral columns are likely limited to about 0.2 m in diameter, whereas horizontal columns of several meters are possible. Scale-up is limited by design of melter and/or crystal-washing section. Vertical or horizontal columns of several meters in diameter are possible. 

Isolation procedures for many biochemicals are based on chromatography. Practically any substance can be selected from a crude mixture and eluted at relatively high purity from a chromatographic column with the right combination of adsorbent, conditions, and eluant. For bench scale or for a small pilot plant, such chromatography has rendered alternate procedures such as electrophoresis nearly obsolete. Unfortunately, as size increases, dispersion in the column ruins resolution. To produce small amounts or up to tens of kilograms per year, chromatography is an excellent choice. When the scale-up problem is solved, these procedures should displace some of the conventional steps in the chemical process industries. 

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