Spectroscopic determination of amount of one constituent of a fluid mixture in another constituent or in the fluid mixture itself, following separation of the mixture into its constituents

摘要

A method (and apparatus) is disclosed for the spectroscopic determination of the amount α_Nn of one constituent N of a fluid mixture 0 in another constituent n of the mixture, following separation of the mixture into its constituents 1,...,M (where n, N ≦ M). The method involves determining the absorptivities a_n (n = 1,...,N) of the M constituents from spectroscopic measurements and computing the amount α_Nn from a mathematical expression containing the absorptivities a_n and a_N which are expressed or expressable as the quotient a_n/a_N only. The method is insensitive to changes in the absorptivities due to feed variability or changes in upstream process conditions. A modification to the method involves determining the content α_N0 of constituent N in feed 0 from a mathematical expression containing a₀, where a₀ is the absorptivity of the feed 0, and a_N, which absorptivities a₀ and a_N are expressed or expressable as the quotient a₀/a_N only.