Scaling Up from Laboratory Data

Scaling Up from Laboratory Data Laboratory experimental techniques offer an efficient and cost-effective route to develop commercial absorption designs. For example, Ouwerkerk (Hydrocarbon Process., April 1978, 89-94) revealed that both laboratory and small-scale pilot plant data were employed as the basis for the design of an 8.5-m (28-ft) diameter commercial Shell Claus off-gas treating (SCOT) tray-type absorber. Ouwerkerk claimed that the cost of developing comprehensive design procedures can be minimized, especially in the development of a new process, by the use of these modern techniques. 

Sieve tray extractors are popular in the chemical and petrochemical industries. The trays minimize axial mixing, which results in good scale-up from laboratory data. The dispersed phase drops re-form at the each perforation, rise (or fall) near their terminal velocity, and then coalesce underneath (or above) the tray, as shown in Figure 14.14(d). The coalesced layer is important to prevent axial mixing of the continuous phase and to allow re-formation of the drops, which enhances mass transfer. The continuous phase passes... 

Efficiencies can be scaled up from laboratory data taken with an Oldershaw column (a laboratory-scale sieve-tray column) tFair et al.. 1983 Kister. 1990T The overall efficiency measured in the Oldershaw column is often very close to the point efficiency measured in the large commercial column. This is illustrated in Figure 10-15. where the vapor velocity has been normalized with respect to the fraction of flooding IFair et al 19831. The point efficiency can be converted to Murphree and overall efficiencies once a model for the flow pattern on the tray has been adopted (see section 16.6T... 

As in the case of gas-liquid systems, the reader is referred to Chapter 12 and the text by Nagata (1975) for additional discussion. Scale-up from laboratory data on the same system can be predicted to some extent. Constant power per unit volume is a good guide, but care must be taken with large tanks and density differences, as mentioned above. 

Scaling Up from Laboratory or Pilot-Plant Data. 14-19... 

It would be desirable to reinterpret existing data for commercial tower packings to extract the individual values of the interfacial area a and the mass-transfer coefficients fcc and /c in order to facilitate a more general usage of methods for scaling up from laboratory experiments. Some progress in this direction has afready been made, as discussed later in this section. In the absence of such data, it is necessary to operate a pilot plant or a commercial absorber to obtain kc, /c , and a as described by Ouwerkerk (op. cit.). 

Detailed models for mixing plus reaction have been presented, and some use computational fluid mechanics to calculate velocities and the local reaction rates throughout the tank [12,13]. Others have developed cell models, with four to six interacting zones to account for different reaction rates [11,14]. These approaches require extensive computations and detailed kinetic data, which may not be available or completely reliable. In industry, multiple reaction systems are generally scaled up from laboratory or pilot-plant data. Mixing theories offer some guidance, but often there is still uncertainty about the correct procedure. 

C)ne of the more widely studied and used columns is that designed by Karr and Lo. The column is shn de in constiuction and exhibits a high throughput and stage efficiency (i.e., low HETS) and a great d ree of flexibility. As already noted, small laboratory units also have some vibrational problems and require stabilization. This type of design has been widely studied and simple scale-up procedures have been repotted. For scale-up from experimental data in a column with diameter D,... 

Process Technology 2—Systems—study of common process systems found in the chemical process industry, including related scientific principles. Includes study of pump and compressor systems, heat exchangers and cooling tower systems, boilers and furnace systems, distillation systems, reaction systems, utility system, separation systems, plastics systems, instrument systems, water treatment, and extraction systems. Computer console operation is often included in systems training. Emphasizes scale-up from laboratory (glassware) bench to pilot unit. Describe unit operation concepts solve elementary chemical mass/energy balance problems interpret analytical data and apply distillation, reaction, and fluid flow principles. 

Scale-up Factors Factors used in thickening will vary, but, typically, a 1.2 to 1.3 multiplier applied to the unit area calculated from laboratory data is sufficient if proper testing procedures have been followed and the samples are representative. 

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