Scaleup pilot columns

Scaleup from pilot column. The most common scaleup is from a small column (e.g., pilot plant) to a commercial column. No reduction in efficiency on scaleup is expected (24,99) as long as... 

Previous work with Oldershaw columns (209-211), however, spells a note of caution to Fair et al. s conclusion. For a fixed system, higher Oldershaw column efficiencies were measured under cellular foam conditions than under froth conditions. For this reason, Gerster (212) warned that when cellular foam can form, scaleup from an Oldershaw column may be dangerous. The conclusions presented by Fair et al. (208) do not extend to Oldershaw columns operating in the Cellular foam regime. Other considerations for scaleup from pilot columns (above) may also be important. The scaleup procedure recommended by Fair et al. (208) is... 

In general, the key to a successful scaleup of packed columns is producing identical distribution conditions in the pilot column to those expected in the prototype. Sections 9.2.1 to 9.3.2 show that this is practically impossible to achieve. Packed-column scaleup iB therefore often uncertain and sometimes dangerous. For best results, one can only do the best he or she can. Based on Secs. 9.3.1 and 9.3.2, this includes... 

Any relevant process factors (Sec. 7.3.6) are allowed for. Also, it is a good policy to pilot-test over several composition ranges engulfing all those expected in the commercial column. A pilot test is never an exact replication of a commercial column, and differences may lead to poor scaleup. 

Wu and Chen (167) recommend pilot testing over the entire range between the expected minimum and maximum operating rates, and taking the highest measured HETP as the basis for scaleup. The author concurs. With structured packings, the loed effect may be due to liqnid rather than vapor loads, and the pilot tests should cover the range of liquid loads (i.e., gpm per square foot of column cross section) that is expected in the prototype. 

It should be noted that the smallest size packings in the Bolles-Fair correlation are nonanally 12 min (0,5 in.) in diameter. If the general rale of 8 1 column packing diameter is to be maintained, (hen a minimum column size of 100 mm (4 in.) is indicated. This is a crucial point in tha design of pilot facilities and the development of scaleup parameters. It is not yet possible to go to the tiny packings for laboratory tests (using, say, column diameters of 25-50 mm) and still obtain reliable scaleup data. 

Methods for predicting efficiency also parallel those for tray columns comparison against a similar installation, use of empirical methods, direct scaleup from laboratory or pilot plant, and use of theoretically derived models. Approaches by vendors of packing usually center on comparisons with similar installations (the so-called vendor experience ) and empirical approximations. Direct scaleup from small column studies is difficult with packed columns because of the unknown effects of geometrical factors and the variations of liquid distribution that are required for practical reasons. Theoretical or semitheoretical models are difficult to validate because of the flow effects on interfacial area. It may be concluded that there is no veiy good way to predict packed column efficiency, at least for the random type packings. 

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