In this article explained about basic idea of different decolourzation techniques used sugar refinery form raw melt to refined sugar like melt clarification, second decolurization process and crystalization process.
Different methods for Decolourization of Raw melt to Refined sugar Production
For general description of Refined Sugar Manufacturing Process
Unit Operations in Sugar Refinery
1. Raw Sugar Storage / Handling
4. Clarification/First Decolourization
6. Second Decolourization
7. Melt Concentration
8. Crystallization & Centrifuging
10. Drying, Cooling & Packing
The process of colour reduction of raw melt involves two basic stages, Pre-treatment of Raw Sugar Liquor and then De-colorization of treated sugar liquor.
The main Objective of above both clarification steps are the removal of turbidity and colour.
The choice of the process will dependent on several factors:
1. Raw Sugar Quality
2. Turbidity Removal
3. Colour Removal
4. Process Capability
5. Capital cost
6. Operating costs
7. Sugar loss & Environmental concerns
8. Refined sugar quality
Basically, colour removal from raw sugar melt to refined sugar occurs in three stages.
First Stage: 1st Decolurization /Clarification of Raw Sugar Liquor- It is classified in to two main clarification processes.
a) Carbonation process.
b) Phospho- floatation Process.
In first raw melt Colour reduction will be depended on type of process. it will be around in the range of 30% to 50%
Second Stage: Secondary Decolourization Process- It having mainly three clarification processes are there.
a)Ion exchange resin.
b) Powdered activated carbon
C) Granular activated carbon
Third Stage: Crystalization Process
a) Crystallization process is the major stage of colour reduction from melt to crystallized sugar
b) Colour transfer from decolourized liquor to sucrose crystal during crystallization vary from 3% to 10% depends on process used in 1st and 2nd decolourization of melt and number of boiling. In second 2nd and 3rd boiling color transfer rate from liquor to crystal will be less compare to 1st massecuite boiling.
c) The color transfer to the crystal, or alternatively the fraction of the color included in the crystals, is different in the raw sugar massecuite boiling compared to refined massecuite boiling. Because of the different spectrum of colorants in the liquor from which the sugar is crystallized.
d) The decolorized liquor from second stage is evaporated in vacuum pan for crystallization of sugar. The exhausted molasses again crystallized to get 2nd and 3rd crop of sugar.
e) The sugar obtained is R1 sugar while the sugar from 2nd &3rd Boiling R2 & R3 sugar. As the R1 Sugar is made from fine liquor its colour value in ICUMSA unit is very low. R2 & R3 sugar made from exhausted molasses. So R2 & R3 sugar will have slightly more colour value.
General Norms of raw melt color reduction in sugar refinery
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Carbonation Process for sugar refinery
Ion Exchange Process for melt decolonization of sugar refinery
Colour Balance in massecuite boiling of Refined sugar