Raw sugar manufacturing:
(1) Milling plant
Water used in milling operation is 25 – 30% of sugar cane.
Assume it as 25%.
Therefore imbition water used = 0.25 × 250 = 62.5
Assuming milling efficiency 95% i.e. 95% of sucrose goes into the juice.
Thus sucrose content in juice = 0.95 × 35 = 33.25
Unextracted sucrose = 0.05 × 35 = 1.75
The final bagasse from last mill contains the unextracted sucrose, woody fibre and 40 – 55% (assume 50%) water.
Thus water content in bagasse = 32.5 + 1.75 = 34.25
Amount of bagasse = 32.5 fibre + 1.75 sucrose + 34.25 water = 68.5
Overall output of mill or juice entering the clarifier will have the following composition:
Water = 175 + 62.5 – 34.25 = 203.25
Sucrose = 33.25
Reducing sugars = 1.25
Impurities = 6.25
Thus total juice = 244
(2) Clarifier
Reagent used: lime (0.5 kg lime/ton of sugar cane) Thus lime to be added = 0.5 × 250 = 125 kg = 0.125 ton Assume 96% efficiency of clarifier to remove impurities.
Therefore impurities to be removed = 0.96 × 6.25 = 6.00
Total sludge from clarifier = 0.125 + 6.0 = 6.125
Amount of clarified juice entering in the evaporator = 244 – 6.0 = 238
This clarified juice is fed to the first effect of the quadruple effect evaporator and analyses as follows