Patent ID: 8194245

Claim:
A method for measuring the concentrations of species present at least 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 (termed the measuring point), and a thermocouple located in the vicinity of said measuring point, in order to capture the temperature (T spl ), in which method: a) a monochromatic signal is sent through a first fibre optic connected to the immersing probe, originating from a laser source the wavelength of which is 785 nm plus or minus 1 nm; b) a signal corresponding to the Raman effect, termed the Raman signal, is captured through a second fibre optic which is also connected to the immersing probe, and sent to a spectrometer using filters defining a cutoff threshold; c) the Raman spectrum of the signal under consideration is recovered at the spectrometer outlet; d) the Raman spectrum obtained is processed using a mathematical method which accommodates the temperature (T spl ) of the measuring point under consideration in order to obtain the concentration C j of the species present at said measuring point, said method for obtaining the concentrations C j of the various species present at the measuring point being based on the formula: C j = P j ⁡ ( T spl , C 1 , … ⁢ , C 5 ) ⁢ σ j ⁡ ( T spl , C 1 , … ⁢ , C 5 ) ∑ i = 1 5 ⁢ P i ⁡ ( T spl , C 1 , … ⁢ , C 5 ) ⁢ σ i ⁡ ( T spl , C 1 , … ⁢ , C 5 ) in which: P i is the integrated intensity of the Raman band due to molecule i; and σ i is the inverse of the relative effective cross section of the molecule i; in which expression the integrated intensities P i are obtained from the measured intensities M j on the Raman spectrum by means of a matrix product in which the coefficients a ij of the matrix M result from a calibration carried out at the temperature (T spl ) of the measuring point, or at a plurality of temperatures framing said temperature of the measuring point, the inverse of the effective cross sections σ i being a function of the temperature (T spl ) and the concentrations (C i ) of the various constituents.