Institut Francais Du Pe'trole

Ifp Energies Nouvelles

Philippe Marteau

Gerard Paul Hotier

Philibert Leflaive

Mathieu Digne

Michel Leclercq

Sophie Dewally-Morel

Nathalie Zanier

Jean-Lucien Molle

Francedillaois Cansell

The present invention describes a method for measuring the concentrations of species present at one point of a separation unit functioning in simulated moving bed mode (SMB), using an immersing probe located at one point in the unit or on one of the streams entering or leaving said unit, and a thermocouple located in the vicinity of the immersing probe, in which a Raman spectrum obtained using a laser source functioning at a wavelength of 785 nm is utilized.

Method for on-line measurement in simulated moving bed units and application to control and regulation of said units

A monochromatic light signal of a wavelength of between 400 and 1300 nanometers is simultaneously passed by a source 1, a beam splitter 2 and optical fibers 3, 3a to at least two points of a zone 9 for the separation of a mixture of isomers and aromatic hydrocarbons having from 8 to 10 carbons atoms. A polychromatic signal is recovered corresponding to the Raman effect between 400 and 3500 cm.sup.-1 by optical receiving fibers 5, 5a connected to sensors 4 at the locations of said points. The chemical composition of the mixture is determined from the Raman spectra obtained by a spectrometer 6. The analysis sequence is repeated, the profiles with respect to the concentration of the isomers in the mixture are reconstituted and by comparison with reference concentration profiles, action is taken on at least on operational variable 11, 12 of the separation process. Application of this process to the regulation of simulated mobile beds, a distillation operation or a crystallization process for obtaining paraxylene or orthoxylene are also provided.

Method for regulating a process for the separation of isomers of

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Philippe Marteau