INORGANIC MINERAL SCALE CONTROL IN SUGAR EVAPORATORS USING SCALE INHIBITORS

摘要

Multiple effect evaporators consume about 70% of the total energy required in a typical sugar refinery. A small amount of scale buildup on evaporators tubes can significantly increase the energy consumption. The fouling consists of mineral scales, organic sludge, and corrosion products. Minerals commonly found as a part of the deposit include calcium carbonate, calcium sulfate, calcium oxalate, calcium phosphate, and silica/silicate compounds. During evaporation, changes in pH, sugar loading, and temperature alter the solubility of minerals, causing deposition at each stage. Laboratory data acquired using simple flask tests have been used to develop a multi-component product to inhibit most of the mineral precipitation and provide deposit control. At lower pH (<5.0) polyphosphate was found to very effective and at pH >5.0, polycarboxylates are effective in controlling calcium oxalate precipitation. Addition of trace amounts of aluminum ions to the water enhances the threshold inhibition with both polyphosphates and polycarboxylates. A careful system monitoring and a well-balanced formulated product fed at an appropriate feed-point can maintain the cleanliness of the evaporative tubes.