A NOVEL INTEGRATED OPTIC SENSOR FOR IN-LINE MEASUREMENT OF MIXING QUALITY IN CHLORINE DIOXIDE PULP BLEACHING

THIS PROJECT ADDRESSES THE DEVELOPMENT OF AN IN-LINE SENSOR FOR MEASURING MIXING QUALITY IN CHLORINE DIOXIDE PULP BLEACHING. THE SENSOR IS BASED ON A PROPRIETARY, INTEGRATED OPTICAL INTERFEROMETER. THE INTERFEROMETER'S UNIQUE DESIGN MINIMIZES THERMOMECHANICAL NOISE TO PROVIDE A HIGHLY STABLE PLATFORM CAPABLE OF DETECTING LOW CONCENTRATIONS OF SPECIFIC CHEMICALS IN FLUID ENVIRONMENTS WITH HIGH SPATIAL RESOLUTION. THE APPROACH RELIES ON THE DETECTION OF SMALL REFRACTIVE INDEX CHANGES IN A THIN SURFACE FILM. SPECIFICITY FOR CHLORINE DIOXIDE IS ACHIEVED BY USING A SURFACE FILM THAT IS REACTIVE OR INTERACTIVE WITH CHLORINE DIOXIDE. A MIXING SENSOR BASED ON THIS APPROACH HAS SEVERAL KEY ADVANTAGES: (1) IT ALLOWS REAL-TIME, CONTINUOUS, IN-SITU MONITORING; (2) IT HAS A BROAD DYNAMIC RANGE, YET IS CAPABLE OF SENSITIVITIES DOWN TO THE PPB LEVEL; (3) IT CAN BE FULLY REVERSIBLE; AND (4) IT PERMITS SPATIAL RESOLUTION WELL BELOW 1 MILLIMETER. THE RESULTING PRODUCT WILL BE SUITABLE FOR ASSESSING BOTH MACROSCOPIC AND MICROSCOPIC MIXING, AND IT WILL PERMIT AUTOMATED FEEDBACK CONTROL OF PULP MIXERS. MOREOVER, DEVELOPMENT OF SENSORS FOR OTHER BLEACHING CHEMICALS (E.G., OZONE, HYDROGEN PEROXIDE) WOULD BE A DIRECT EXTENSION OF THIS EFFORT. IN PHASE I, A PRELIMINARY SELECTION OF CANDIDATE WAVEGUIDE COATINGS WILL BE MADE AND THEY WILL BE SCREENED AND OPTIMIZED FOR THEIR RESPONSE TO AQUEOUS SOLUTIONS OF CHLORINE DIOXIDE.