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  • OurMarts

  • 18 Mar,2020

Clarification And Colloidal Impurities...

Colorants

  • Present naturally in cane juice :
    • Chlorophyll, xanthophylls, carotene and anthocyanine.
  • Developed during processing due to changes in pH temperature and retention time :
    • caramalization, decomposition of reducing sugars and reaction of RS with amino acids.
    • Polyphenols like tannins / saccharetine forms color during processing are present naturally in cane.

Bagacillo – Major color carrier

  • Improvements in milling technology and higher cane preparation led to carry over of bagacillo and pith to juice.
  • 1% bagacillo in MJ increases clear juice color by 2.5 %
  • Bagacillo is around 50% cellulose and rest hemicelluloses, pentosans and lignin.
    • Hemicelluloses has pentose,
    • lignin has saccharetin.
      • Originally colorless but forms yellow color with MOL treatment.
      • Reacts with iron and oxygen under alkaline conditions forms dark colored compounds.

ICUMSA Color of sugar : colloidal impurities.

  • Colloidal impurities affecting ICUMSA color
  • Bagacillo in mixed juice,
  • Bagacillo and pith in rotary vacuum filtrate
  • Fine girt, sand, silica and un-dissolved particles in milk of lime (MOL)
  • Fine sugar crystals in melt.

Effect of colloidal impurities :

  • Higher lime and sulfur consumption.
  • Improper heat exchange.
  • Increased pan boiling time.
  • Increased viscosity.
  • Poor exhaustion of molasses.
  • Lower crushing rate.
  • Poor sugar quality wrt color, ash, SPM & RS.

Prevention is better than cure-

  • Filtration can prevent the entry of these suspended colloidal matter. This can be achieved by screening of inputs.
    • DSM screens with 0.7 mm aperture.
      • Insufficient to separate fine bagacillo.
    • Double DSM screens with 0.5 / 0.3 mm aperture in series.
      • Chocking of screens reduces efficiency.
      • Rotary screens could not solve chocking problems.

Special Device is necessary to :

  • Avoid screen blinding,
  • Removal of suspended impurities / fine bagacillo,
  • Minimum retention time,
  • Minimum water, steam and power consumption