Since the successful manufacture of activated carbon in the early 20th century, the first application to the field was the decolorization of sucrose. There are many steps in the whole procedure. First, it is clarified with lime. The initially refined sugar is crystallized and concentrated, which is called raw sugar, and the purity is about 96%. The washed crystals are dissolved in water to become 50%-60% sugar liquid. The next step is to clarify mainly by adding lime to make the sugar liquid slightly alkaline, and then neutralizing with phosphoric acid. The formed calcium phosphate can adsorb impurities, and removed by filtration, then decolorized with activated carbon.
The pH value of the sugar solution is very important when decolorizing with activated carbon. It is easy to cause sugar conversion when it is acidic, but the decolorization effect is good. The sugar liquid is dilute to facilitate decolorization, but the evaporation load will be increased later, the general control concentration is about 50%. The range of temperature is 70-80 ° C. A problem that should be noted is that activated carbon will lower the pH during the decolorization process, which means that the invert sugar will increase, so the pH of the sugar solution should be monitored at any time.
Since the 1950s and 1960s, some Americas countries have used continuous decolorization of granular activated carbon to make large-scale, continuous decolorization. After decolorization, the deactivated activated carbon can also be recycled. In addition to the conventional adsorption tower, Japan also created a pulse adsorption tower in 1963. The sugar liquid enters from the lower part of the pulse tower and it is discharged at the top of the tower after being pulsed with the granular activated carbon in the tower. The activated carbon with the heaviest adsorption of pigment loaded in the lowest part of the tower is discharged regularly every day, while new carbon or regenerated carbon with the same quantity of exhaust carbon are added from the top of the tower. The release and filling of the activated carbon is completed in a few minutes. The discharged waste carbon will be washed and then dried by hot air to the moisture content of 45% and sent to a regeneration furnace for regeneration.
