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Scaling

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By Bento, Luis San Miguel
Posted on 2009-12-08    Last edited on 2010-08-10

On heating surfaces of evaporators, vacuum pans and other heating equipment some compounds in solution can precipitate forming incrustations or scale. This scale normally has a lower heat conductivity than metal from the equipment and heat transfer will decrease as scale forms. To minimize this problem periodical mechanical and/or chemical cleaning is necessary. This is a great inconvenient as the equipment must stop for cleaning. Therefore,  capacity decreases or extra equipment is necessary.

Major components in scale of cane sugar mill evaporators are (Rein P., 2007; Doherty, 2000):

- In the first effects:     Calcium phosphate (first two effects)
                                          Organic matter-protein, polysaccharides (first effect mainly)
                                          Hydroxyapatite

- In the last effects:     Silica (last and penultimate effect)
                                         Calcium oxalate (usually in last vessel)
                                         Calcium magnesium aconitate (last vessel)
                                         Carbonates (mainly in penultimate vesses)
                                         Sulfates

Bibliography

Rein P., 2007, Cane Sugar Engineering, Verlag Dr.Albert Bartens KG, Berlin
Doherty W.O.S., 2000, Chemical cleaning of sugar mill evaporators, Proc. Aust.
Sugar Cane Technol
., 22, 341-346


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