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Formation of thermodynamically unstable calcium oxalate dihydrate in sugar mill evaporators

East, Chris P., Doherty, William O.S., Fellows, Christopher M., & Yu, Hong (2010) Formation of thermodynamically unstable calcium oxalate dihydrate in sugar mill evaporators. In Proceeding of 32nd Australian Society of Sugar Cane Technologists (ASSCT) Conference, ASSCT, Bundaberg, Queensland, pp. 522-533.

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Abstract

Calcium oxalate (CaOX) is the most intractable scale component to remove in sugar mill evaporators by either mechanical or chemical means. The operating conditions of sugar mill evaporators should preferentially favour the formation of the thermodynamically stable calcium oxalate monohydrate (COM), yet analysis of scale deposit from different sugar factories have shown that calcium oxalate dihydrate (COD) is usually the predominant phase, and in some cases is the only hydrate formed. The effects of trans-aconitic, succinic and acetic acids, all of which are present in sugarcane juice, and ethylenediamine tetraacetic acid disodium salt (EDTA) on the growth of CaOX crystals have been examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and thermogravimetric analysis (TGA). trans-Aconitic acid, which constitutes two-thirds of the organic acid component in sugarcane juice, in the presence of sugar resulted in the formation of COD and COM in a 3:1 ratio. EDTA was the most effective acid to promote the formation of COD followed by trans-aconitic acid, then acetic acid and lastly succinic acid.

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ID Code: 34327
Item Type: Conference Paper
Keywords: Calcium Oxalate, Organic Acid, Fouling, Crystal Habit, Sugar
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Colloid and Surface Chemistry (030603)
Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > OTHER CHEMICAL SCIENCES (039900) > Industrial Chemistry (039903)
Divisions: Past > Schools > Chemistry
Current > Research Centres > Centre for Tropical Crops and Biocommodities
Past > QUT Faculties & Divisions > Faculty of Science and Technology
Funding:
  • ARC LINKAGE COMBO/LP0882891
Copyright Owner: Copyright 2010 [please consult the authors]
Deposited On: 03 Sep 2010 10:01
Last Modified: 22 Jul 2014 13:57

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