Influence of thin juice pH management on thick juice color in a factory utilizing weak cation thin juice softening

Abstract

In beet sugar factories utilizing weak cation thin juice softening, soda ash addition to thin juice is utilized to pre-soften the juice to a suitable feed hardness for supply to the weak cation reactors. Generally, there is addition of 50% caustic solution downstream of the weak cation reactors to counter the effect of H + bleed from the freshly regenerated weak cation resin during the reactor service cycle. If not precisely controlled, the post-reactor re-alkalization of the thin juice may result in over-alkalization of thin juice leading to pH rise in evaporation and an associated color rise in the juice during evaporation. The subject investigation was undertaken for the purpose of optimizing the pre-softening of thin juice while also achieving overall optimum pH management thus avoiding juice over-alkalization and the resulting associated color rise in process juices during juice concentration. A means of pre-alkalization control was developed and implemented satisfying both the pre-softening and the overall juice alkalization requirements leading to the complete elimination of the use of liquid caustic for post-reactor re-alkalization and the elimination of excessive color rise in evaporation. Optimum juice pH targets for minimum color rise in concentration are identified resulting in minimum thick juice color and invert concentration while meeting the competing juice processing requirements for the production of soft thin juice.