On-line soft measurement method of pH value and H2 SO3 concentration in acrylonitrile polymerization system

The present invention relates to an on-line soft measurement method of pH value and H2SO3 concentration in polyacrylonitrile polymerization system under the sodium-chlorate-sodium bisulfite initiating system. It is characterized by that it utilizes the simulation experiment of NaClO3-NaHSO3 oxidation-reduction initiating system under the condition of operation in the course of acrylonitrile polymerization to make the obtained experiment result undergo the processes of mathematical regression and normalization treatment to obtain an integrated quantitative mathmatical expression formula of 5 operation variable quantities and pH value and H2SO3 concentration in said polymerization system: in which (ci, i=1,2,...4) and D (di, i=1,2,...4) are moded fitting parameter vector, lambda (lambda i, i=1,2,...4) and gamma (gamma i i=1,2,...4) are model fitting parameter matrix x is input vector, i.e. operation variable quantity, after calculation, the real time result of pH value and H2SO3 concentration in the acrylonitrile polymerization system can be obtained.