Application of industrial photometry calling for measurement of both turbidity and color.
The thin juice extracted from the sugar-beet passes through three purification steps: addition of milk of lime for preliminary and main separation, precipitation of the calcium carbonate with carbon dioxide (saturation), and removal of the resulting sludge by sedimentation or filtration.
Thin juice purification: turbidity measurement
If a defect occurs in the filtration step, the solids will be deposited in the ion exchangers of the subsequent softening step or in the evaporators, thus necessitating time-consuming cleaning work. Continuous detection of the turbidity value shows up any leaks immediately. Use of the free-fall flow cell avoids window contamination and provides maintenance-free duty over the entire milling season.
Following evaporation, the thick juice is decolorized. This step is monitored by the Sigrist colorimeter at 420 nm with the dichromatic method, which eliminates possible errors caused by solids and window contamination.
The production of high-purity sugar includes a washing cycle for removing any molasses still adhering to the crystals. Just the right amount of water must be used to remove the molasses without dissolving the sugar. The washing process is optimized by detecting the color of the effluent and correcting the washing water rate accordingly. By combining color detection with density measurement, one can obtain the reading directly in ICUMSA color units.