Demineralization of Liquid Sucrose

When highly refined liquid sucrose is desired by customers instead of dry sugar, there are a few options for producing a non-inverted liquid sucrose product using various configurations and forms of ion exchange resin technology.

Weak Acid Cation Mixed Bed
One process for producing liquid sugar involves passing the high Brix, moderate temperature liquid sucrose through a mixed bed containing a high pK weak acid cation resin (H⁺ form) and strong base anion resin (OH^- form). This process produces a liquid sucrose with < 0.2% invert and color < 20 ICUMSA.

The sucrose solution can be decolorized and demineralized by passing through a bed of strong base anions (OH^- form) to convert all the salts to base, then passing through a separate bed of high pK weak acid cation resin which will exchange the cations and neutralize the base. The weak acid cation effluent pH will be approximately 4.0 and must be blended with a sidestream of syrup to bring the pH up to avoid inversion. 

In order to avoid precipitation of Mg(OH)₂ or CaCO₃ in the resin bed, either a cation resin can be used to soften the syrup, or the anion can be run in the HCO₃^- form which will produce more highly soluble bicarbonate salts. Conductivity reduction and color removal will be somewhat less in the HCO₃^- form.

The liquid sucrose can be treated through a macroporous cation resin (H+ form), followed by weak base anion resin (free base form) for removal of salts and color below liquid sugar standards. This process requires a treatment temperature less than 10 °C (50 °F) to avoid sucrose inversion.

To be able to operate at this low temperature without high viscosity, (causing pressure drop and kinetic problems) the syrup concentration must be below 50 °Brix. The liquid sucrose must then be evaporated back up to 68 °Brix prior to storage and shipment to avoid bacteria growth.