Sugarcane mill
[3] The term is also used to refer to the equipment that crushes the sticks of sugar cane to extract the juice.
However, stalks from a burnt field more quickly loose sugar content while waiting to be processed.
Overall, limiting the time between cutting and milling is essential for achieving a high sugar yield and quality.
[citation needed] Sugarcane diffusion is the process of extracting the sucrose from the cane by osmosis and lixiviation also known as leaching.
The diffusion process proper takes place on the 10-16% of sugar containing cells that have not been opened.
In this phase sucrose penetrates the walls faster than non-sugar with higher molecular weight.
[16] During purification, calcium hydroxide, also known as milk of lime or limewater, is added to the cane juice to adjust its pH to about 7 or 8.
The superheated limed juice is then allowed to flash to its saturation temperature: this process precipitates impurities, which get held up in calcium carbonate crystals.
[17] The settled solids can be filtered to produce a juice of poor clarity, which can be recycled for further purification.
[citation needed] The product of this step is syrup of 78 to 86% purity with a soluble solid content of 60-65°Brix and containing 3.5-4.5% invert sugars.
The purpose of the crystallizer is to reduce loss of sucrose by it remaining in the mother liquor / molasses, in particular with low-grade massecuites.
However, as the mother liquor of the massecuite is still supersaturated at this point, the viscosity can be reduced without re-solution of the crystals.
[20] While the mother liquor, molasses passes through the holes in the centrifuge, the sugar crystals are retained.
This method boils the sugar liquors in three crystallization/centrifugation stages, called A-, B- and C-.
The C-sugar from the centrifuge is mingled with syrup and used as massecuite seed, and so returns to the start of the process.
It is a heavy viscous material containing about one-third sucrose, one-fifth reducing sugars, and the remainder ash, organic non-sugars and water.
To make plantation white sugar by carbonation requires changes to the purification, evaporation, and storage steps.
In the purification step, the objective of carbonation is to separate non-sugar contents such as colloids and insoluble particles as well as colored material.
[29] At the end of the evaporation step, Sulfur dioxide (SO2) is added to lower the pH of the syrup to 7.0.
[29] In sugar factories, carbonation is not widely used, because it requires large quantities of lime and CO2, and sulphitation is cheaper.
In the purification stage of cold acid sulphitation, SO2 is added to the mixed juice in order to lower the pH to 3.8-4.2.
[30] The purification stage of hot acid sulphitation involves first heating the mixed juice to 70°C before lowering the pH to 3.8-4.2 by adding SO2.
[31] The crystallization and centrifugation steps for plantation white might differ on account of the boiling system used.
The remaining fibrous solids from the juice extraction phase, called bagasse, are burned for fuel in the mill's steam boilers.
These boilers produce high-pressure steam, which is passed through a turbine to generate electrical energy (cogeneration).
As in many other industries factory automation has been promoted heavily in sugar refineries in recent decades.
[36] A cattle mill on Jamaica was generally a round, covered building of no less than 60 feet diameter.
Hard wood posts, or pillars of masonry supported the roof, which was mostly covered with wooden shingles.
In an 1820s example, the lower four feet of the main roller were covered by a cast iron case, in the center of which was a gudgeon.
On the top, the main roller was driven by long levers attached to oxen walking in a roundabout.
