White Liquor Filtration
In the causticizing process white liquor is filtered and clarified to remove particulates and lime mud. These can create long-term scaling problems at the digester and downstream problems due to contamination. Installing a turbidity sensor after the white liquor clarification process allows for immediate detection of high solids levels in the white liquor. These high solids levels can be a result of either a filter break or poor settling in the clarifier.
Proper clarity of white liquor prior to storage can be verified by using an optek TF16-N scattered light sensor with sapphire optics that are resistant to hot caustic process solution. Maximum measuring range is 0 to 500 ppm for this application and the optimal used range is 0 to 100 ppm with a normal lime mud content of less than 20 ppm.
Achieving high quality white liquor and increasing digester performance leads to reduction of product losses and lime build-up downstream. This, in turn, reduces overall maintenance costs in chemical recovery.