ADVANCED CONTROL OF C-8 AROMATICS SEPARATION PROCESS WITH REAL-TIME MULTIPOINT ONLINE RAMAN-SPECTROSCOPY

This paper describes a Raman system developed for the control and the optimisation of a C-8, aromatics separation process based upon simulated moving bed chromatography. The concentrations of the five components, at four points of the separation unit, are delivered every 15 s so that the operating variables can be corrected from direct interpretation of the concentration profiles visualised in real-time. The Raman spectrometer and the argon laser are at 30 m from the ELUXYL(R) pilot unit located in the Institut Francais du Petrole (IFP) centre of Solaize. The laser beam is split towards four optical fibres which are connected to four Super DILOR head sensors located at the four points of the process. The optical observations are made through sapphire windows and the Raman spectra are simultaneously recorded with a CCD detector. The concentration profiles are obtained from the spectra by means of quantification and visualisation software. The system follows the internal concentration profiles in real-time. The purity of para-xylene and the loss of para-xylene in the raffinate stream are continuously determined. The Raman spectra together with the quantification software give the concentrations with an uncertainty of +/- 0.5% for all values in the 0-100% concentration range.