Analysis device and associated method for operating simulated moving bed xylenes separation units a raman spectrometer

Simulated moving bed xylenes separation unit (called an SMB unit), using two adsorbers A and B connected in series, i.e. with the circulation current originating from the bottom of adsorber A sent to the top of adsorber B and with the circulation current originating from the bottom of adsorber B sent to the top of adsorber A, said unit comprising a device for measuring concentration by analyzing a Raman spectrum relating to sampling points, and said device being constituted by two identical and independent routes, called analysis route 1 and analysis route 2, each route having two branches, one called the main branch operating for a majority of the time, the other called the subsidiary branch operating for a minority of the time, and the sampling points being defined as follows:

• for analysis route 1
• a) internal circulation current sent from adsorber B to adsorber A,
• b) extract originating from one or other of the adsorbers,
• c) raffinate originating from one or other of the adsorbers,
• for analysis route 2
• d) distilled raffinate (leaving distillation column C),
• e) internal circulation current from adsorber A to adsorber B,
• f) feed of the unit at the inlet of one or other of the adsorbers, each analysis route comprising two distinct branches with mutually exclusive operation, branch 1, called the “main branch” (MB) being used for the Raman analysis and branch 2, called the “subsidiary branch” (SB) being used for sample collection, and branch 1 of each analysis route comprising the following main components taken in the direction of the stream to be analyzed:
• a shut-off valve (6) making it possible to force the circulation into branch 2 in certain situations,
• a thermocouple (7) making it possible to take the temperature of the sample to be analyzed,
• an analysis cell (8) containing an optrode (10), receiving an input laser signal and sending an output signal to the Raman spectrometer, the internal volume of said measurement cell being of the order of 1 cm3,
• a second shut-off valve (9) for isolating the analysis cell in the event of maintenance.