Process of preparing crystallised sugar (that we consume) from sugarcane...
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Answer:
Sugarcane is broadly classified into three varieties early, general and unapproved. Cane is sowed during February and October every year. The first seed growth is known as the plant and subsequent growth after harvesting from the stem is known as Ratoon. The early variety has more sugar content than the general variety.
Every farmer within the command area of the Mill is provided with a calendar, which tells him when he can expect a Mill Supply Ticket (Purchy), against which he will deliver the sugarcane.
He then harvests the cane and transports it either in a bullock cart or tractor trolley to the mill. Cane is also bought at the mill's own centers within the command area. This cane is then transported in trucks or through rail to the mill.
Cane is weighed using an electronic weigh bridge and unloaded into cane carriers. It is then prepared for milling by knives and shredders. Sugarcane juice is then extracted by pressing the prepared cane through mills. Each mill consists of three rollers:
Extracted juice mixed with water is weighed and sent to the boiling house for further processing. Residual bagasse is sent to boilers for use as fuel for steam generation
This juice is heated and then treated with milk of lime and sulphur dioxide. The treated juice is then further heated and sent to clarifies for continuous settling. The settled mud is filtered by vacuum filters and filtered juice is returned to be further processed while the Oliver cake is sent out
The clear juice is evaporated to a syrup stage, bleached by sulphur dioxide and then sent to vacuum pans for further concentration and sugar grain formation. Crystals are developed to a desired size and the crystallized mass is then dropped in the crystallizers to exhaust the mother liquor of its sugar as much as possible. This is then centrifuged for separating the crystals from molasses. The molasses is re-boiled for further crystallization
Thus, the original syrup is desugarised progressively (normally three times) till finally, a viscous liquid is obtained from which sugar can no longer be recovered economically. This liquid, which is called final molasses, is sent to the distillery for making alcohol.
The sugar thus is separated from molasses in the centrifuge is dried, bagged (50 Kg and 100 Kg), weighed and sent to storage houses.
Sugar is made in different sizes and accordingly classified into various grades I.E. large, medium and small.
Explanation:
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Sugar production involves two distinct operations; (a) processing sugar cane or sugar beets into raw sugar, and (b) processing the raw sugar into refined sugar. Cane and beet sugar extracts contain sucrose, and undesirable amounts of polysaccharides, lignins, proteins, starches, gums, waxes, and other colloidal impurities that contribute colour and/or taste to the crystalline product, and reduce product yield. The raw juice, therefore, is subjected to heating, liming addition, and clarification to remove proteins and colloidal matter.19 Sugar refining is a highly energy-intensive process; hence, membrane technology is highly attractive. However, because of high osmotic pressure and high viscosities, the role of membrane application is limited to dilute streams for clarification and purification at the juice extraction stage. Possible operations that could be replaced by UF or MF are shown in the dotted areas in Figure 3.12.17 UF and MF could be used for removing these colloidal and macromolecular impurities with little or no addition of lime, carbon dioxide, or sulphite before the clarified juice is evaporated and crystallised. Further, removing macromolecules and reducing lime levels reduces fouling and scaling of the evaporators.
The cane sugar processing consists of the following steps: sugar cane is crushed, the juice is heated and filtered, sent to a series of crystallisation steps to create crystals of raw sugar, followed by centrifugation to remove any remaining juice or syrup. The last step produces a small stream of remaining syrup called cane mill molasses containing up to 55% (wt.) sucrose and substantial amounts of invert sugar (glucose–fructose mixture) impurities. Sucrose is the fraction that becomes crystallised sugar, and has considerable commercial value but cannot be extracted economically because of the impurities. Several US patents20 describe a process to recover sucrose from molasses and other syrups incorporating NF and MF. In this process, the molasses is pretreated by MF and/or UF to remove colloids, polysaccharides, and other high molecular weight impurities to prevent fouling of NF membranes. NF membranes retain more than 75% sucrose and small amounts of invert sugar while the permeate contains most of the invert sugar and less than 10% sucrose. The retentate flows back to the first crystalliser/centrifuge stage where it crystallises into raw sugar, and is then processed in a refinery to make refined sugar. The desugarised molasses is useful as animal feed. Although beet sugar contains no invert sugars, molasses can still be treated by the NF process.