Production Scale Chromatography

Individual drums are provided for each product fraction. A detector monitors the separation and provides signals for controlling the injection and collection sequence. The operation of partial condensers for the dilute eluted streams presents challenges because of aerosol formations. When a valuable carrier such as nitrogen is used, it must be cleaned up and recycled. 

A 1968 estimate of the cost breakdown for a plant with a column 4 ft dia by 15 ft high and a throughput of 200-920 tons/yr has been converted to a percentage basis in Table 15.7 because of its age. The costs are said to not vary greatly with throughput or the nature of the separation, although this analysis has been made specifically for the separation of a- and /3-pinenes. The temperature was 165°C and the solvent was Carbowax 20M. The design was based on data in a 4 in. dia column which had a capacity of 200-1500 mL/hr. 

Some of the materials for which chromatographic separation should be considered are essential oils, terpenoids, steroids, alkaloids, pharmaceuticals, metal chelates, isotopes, and dose-boiling isomers. For easy separations, vacuum distillation, liquid-liquid extraction, and fractional crystallization are less expensive. 

The economic break between fixed bed and continuous operation has been estimated as ion concentrations of 0.57V, or flow rates above 300 gpm, or when three or more parallel beds are required to maintain continuous operation. The original application of continuous ion exchange was to treatment of radioactive wastes, but some installations of ordinary water treating have been made. 

Resin requirements for two extremes of ion concentration are analyzed in Example 15.3. The high concentration stream clearly is a candidate for continuous ion exchange. Manufacturers and distributors of ion exchange resins are Dow, Rohm and Haas, Bayer, Kasai, Sybron Chemical and Purolite. 

In this process, dissolved electrolytes are removed by application of electromotive force across a battery of semipermeable membranes constructed from cation and anion exchange resins. The cation membrane passes only cations and the anion membrane only anions. The two kinds of membranes are stacked alternately and 

Membranes may be manufactured by mixing powdered ion exchange resin with a solution of binder polymer and pouring the heated mixture under pressure onto a plastic mesh or cloth. The concentration of the ion exchanger is normally 50-70%. They are chiefly copolymers of styrene and divinylbenzene, sulfonated with sulfuric acid for introduction of the cation exchange group. 

Standard cell sizes are up to 30 by 45 in. In an individual stack the compartments are in parallel, but several stacks in series are employed to achieve a high degree of ion exchange. The ion exchange membrane is not depleted and does not need regeneration. The mechanism is that an entering cation under the influence of an emf replaces an H+ ion from the resin and H+ from solution on the opposite face of membrane replaces the migrating cation. 

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Other modes of operation, including recycle and flow reversal schemes and continuous chromatography, are discussed in Ganetsos and Barker (Preparative and Production Scale Chromatography, Marcel Dekker, New York, 1993). 

Preparative and Production Scale Chromatography, edited by G. Ganetsos and P. E. Barker... 

Ruthven, D.M. and Ching, C.B. (1993) Modeling of chromatographic processes. Preparative and production scale chromatography. In Chromatographic Science Series, Vol. 61. Eds. Ganetos, G., Barker,... 

Sardin M,Schweich D,Villermaux J (1993) In Ganestos G, Barker PE (eds) Preparative and production scale chromatography. Marcel Dekker, New York, pp 477-521... 

Balannec B, Hotier G (1993) From batch to countercurrent chromatography. In Ganetsos G, Barker PE (eds) Preparative and Production Scale Chromatography, Marcel Decker, New... 

Ganetsos, G. and Barker, P. E. Preparative And Production Scale Chromatography (Marcel Dekker, 1993) Hamada, J. S. J. Chromatogr. 760 (1997) 81. Large-scale high-performance liquid chromatography of enzymes for food applications. (Review)... 

Chromatographic separations are necessarily intermittent with alternate injections and elutions, although a measure of continuity can be achieved with an assembly of several units, or with suitably sized surge tanks. A process flowsketch appears in Figure 15.22(b). Information on production scale chromatography is provided by Conder (1973). Only separations difficult to achieve by other means are economical with chromatography. 

H. Colin, in Preparaiive and Production Scale Chromatography, Marcel Dekker. 1993, p. 11. 

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