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Raw Sugar - Yield - Refining

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By Bento, Luis San Miguel
Posted on 2011-08-02    Last edited on 2011-08-02

Raw Sugar Yield Formulas

Luis San Miguel Bento

The formula 2xPol-100 was theoretically deducted considering a molasses apparent purity (AP) of 50º. In fact, if one consider that all non sugars  in raw sugar are incorporated in molasses, the sugar in molasses with AP = 50º will be 100 – Pol. Therefore, if we deduct this value to Pol we have 2xPol-100 as the sugar not incorporated in molasses.

This formula is used in general but, however, the formula does not consider the sugar losses during refining. When molasses are produced with a Pol less than 50º, this fact can compensate the losses during refining. During the years 50º and 60º from last century, with raw sugars with 97º to 98º Pol, the theoretical value of raw sugar yield, using 2xPol-100 formula, was attained (see graphic bellow).  In this range, when molasses of 40º AP were produced, the refining losses were compensated. However, to raw sugar Pol above 98,5º the yield variation (yield with molasses at 40º AP subtracted of yield with molasses at 50º AP) does not compensate the refining losses. Therefore, for raw sugar with Pol higher than 98,5º the theoretic yield, using 2xPol-100 formula, will be only attained with molasses purity lower than 40º or with very low losses in the refinery.

A more practical formula will be:   2xPol-100-0,50.
This formula allows for a maximum refinery losses of 0,50%.

Other formulas used are::

Pol – 4,5 x Ash – Invert – (0,6 a 0,8)                   South Africa

Pol – 3 x Ash – 2 x Invert                                     United Kingdom

Pol – 5 x Ash – Invert                                           Australia

In next Table raw sugar yelds for different raw sugars are presented, using the above formulas.

 Table
Raw sugar yields applying different formulas

 

Mozambique

Brazil

Pol

99,19

99,25

Ash

0,14

0,12

Inverts

0,21

0,28

2 Pol - 100

98,38

98,50

2 Pol – 100 – 0,50

97,88

98,00

South Africa

97,55 - 97,75

97,63 – 97,83

United Kingdom

98,35

98,33

Australia

98,28

98,37

 

 

 

 

 

 

 

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