Brief Description of Ion Exchange Operations
The decolourization is effected by passing the clear melt through polystyrene based resin. Hot
filtered melt at a temperature of about 80 – 85 deg C is pumped at a controlled flow rate through
first column and the discharge is collected in a tank. The partially decolorized liquor is fed again
to the next column and the liquor is be collected in the fine liquor tank ready for evaporation.
The resin, after completing the duty cycle, which is normally of 16-20 hours is de-sweetened by
back flushing it with hot water to disperse the bed and to remove any suspended matter which
may have collected during the duty cycle. Regeneration, which removes the absorbed colour
from the resin, is carried out using alkaline brine solution. The resin is then rinsed thoroughly
with hot water, and then sweetened-on with liquor. The sweet water generated by this process is
used for raw sugar melting. Provision is also made to treat the resin with dilute hydrochloric acid
after 20–25 cycles to remove scale, etc from the resin. Regeneration is carried out with 10%
sodium chloride solution having 1% - 2% concentration of sodium hydroxide.