The Operation and Performance of a Large Scale Sequential Chromatographic Separator

Abstract

A review is given of general chromatographic theory, the factors affecting the performance of chromatographic columns, and methods of improving column efficiency. Scale-up of the chromatographic process for preparative and production purposes is discussed. The design of a sequential continuous chromatographic refining unit (SCCR1) for continuous gas/liquid chromatographic separations is reported. A novel feature of the unit is that counter-current operation is simulated by sequencing a system of inlet and outlet port functions around a closed symmetrical system of twelve fixed, 7.6 cm diameter columns. The operating characteristics of the unit have been investigated using an equivolume feed mixture of 1,1,2-trichloro-1,2,2-trifluoro-ethane (Arklone.P), and 1,1,1-trichloro-ethane (Genklene.P.). The solvent phase was silicone oil DC 200/50 coated onto 500-355 µm particles of Chromosorb.P, with compressed air acting as the carrier fluid. Optimisation of the carrier gas flowrate and port function sequencing interval allowed the above chemical system to be separated into two product streams of purity>99.7%, at feed rates up to 1000 cmhr-1 . Investigations into the internal column temperature profile revealed extensive temperature differences with a minimum temperature of 26°C below ambient being recorded. Redesign of the solute feed vaporisation process reduced the temperature perturbations and a flowed the maximum through put of the unit to be increased to 1400 cm3 .hr-1 for the system Arklone.P./Genklene.P. The ability of the unit to separate a second more difficult chemical system of Arklone.P., and dichloro-methane has also been demonstrated. Prior to any design changes this system had proved impossible to separate. Theoretical treatments of the counter-current chromatographic process are reviewed, and a computer simulation of the SCCR1 based on the development of concentration, temperature and pressure profiles over a series of theoretical plates is presented. The accuracy of the model, methods to improve it, and applicability to other forms of continuous chromatography are discussed.