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Scale Minimization in Sugar Industry Evaporators using Nanoporous Industrial Bio-solid Waste Bagasse Fly Ash

ABSTRACT

Scale deposition on the surface of heat exchangers of the evaporators of a sugar mill is the bane of sugar industry. It causes corrosion of surfaces, restricts fluid flow and impairs heat transfer (because it has very low thermal conductivity) across the metal–fluid interface. Accumulation of scale is the combined effect of several processes involving inorganic/organic molecules or ions present in the cane juice. Bagasse fly ash (BFA), obtained from the flue-gas line of bagasse-fired boilers, exhibits unique characteristics such as very high carbon content (49%), large surface area (~ 500 m2/g), high pore volume, mesoporous pore size and spontaneous adsorption, rendering it suitable as adsorbent for clarification of cane juice, a process purporting to remove several of the impurities. The aim of the present paper is to study the feasibility of using BFA (primary mesh size of 200 μm) as adsorbent for clarification of industrial cane juice which in turn would minimize formation of scale. BFA consists of globular structures aggregated in a fractal-like configuration, with pore sizes ranging between 100 nm and 1.0 µm. After it has adsorbed impurities from cane juice (becoming A-BFA), its X-ray diffraction and FTIR spectroscopy show the presence of silica, alumina (Al2O3), CaO, CaSiO3, Ca8Si5O18, mullite, quartz, haematite, kaolinite and amorphous silica. Rate of adsorption as a function of BFA dosage and reaction time was studied using spectrophotometer and colorimeter. Up to 19% colour reduction takes place in cane juice treated with BFA. The results suggest that BFA can be effectively used for initial clarification (in particular, removal of silica, quartz, mullite and calcite) of sugar cane juice.