Sugar cane and sugar beet contain up to 20% sugar. The first stages extract the raw juice either through crushing the sugar cane or slicing up the sugar beets. The remaining raw juice is extracted from the plant material through a leaching process in a diffusion tower. The raw juice contains roughly 99% of the original sugar, plus various impurities. The juice is purified using multiple stages where milk of lime (Ca(OH)
2) and carbon dioxide (CO
2) are added. These two chemicals help to precipitate out impurities and neutralize any organic acids in the juice. The chemical reaction between the two additives creates calcium carbonate (CaCO
3). CaCO
3 binds with salts and impurities and precipitates out as a solid at the thickener and collection tanks.
Measurement and control problems
pH measurement is one of the key parameters to controlling effi ciency of the process. For this reason it is measured at the inlet and outlet of each stage within the process.
These applications need reliable pH measurement for up to six months while the mill is in production. Barben Analytical Performance Series pH sensors offer reliable design that can be trusted through the entire campaign. Plugging of the reference junction is the most common problem cited in sugar mill applications. The Barben Axial Ion Path
® reference technology provides a great solution for these issues. The filtering design of the reference and large amount of electrolyte contained inside the sensor ensure that a strong signal path is maintained.