SUGARDESCRIPTION:
The sugar industry processes sugarcane and sugar beet to manufacture edible sugar more than 60% of the world’ssugar production is from sugar cane.
Sugar beet, sugar manufacturing is ahighly seasonal length of about 6 to 18 weeks for beets and 20 to 32 weeks forcane
Approximately 10% of the sugar canecan be processed to commercial sugar, using approximately 20 cubic meters ofwater per metric ton of cane processed. Sugar is also extracted from beet root
Sugar cane contains:
§ 70% water
§ 14%fiber
§ 10 to 15% sucrose and
§ 2.7% soluble impurities
RAWMATERIALS
1. Sugar cane
2. Sugar beats
Sugar is a board term applied to alarge number of carbohydrates present in many plants. In the sap of some plantsthe sugar mixtures are condensed into syrup.
The feed accumulates sugar to about 15 percentof its weight. Sugar beet is a beetroot variety with the highest sugar content.About 3700000 tons of sugar is manufactured from sugar beet
STRUCTUREOF SUGARS:
Sucrose: a disaccharide of glucose(left) and fructose (right), important molecules in the body
Monosaccharide in a closed-chain formcan form glycosidic bonds with other monosaccharides, creating disaccharides(such as sucrose) and polysaccharides (such as starch). The prefix"glyco-" indicates the presence of a sugar in an otherwisenon-carbohydrate substance.
Monosaccharides include fructose,glucose, galactose and mannose. Disaccharides occur most commonly as sucrose(cane or beet sugar - made from one glucose and one fructose), lactose (milksugar - made from one glucose and one galactose) and maltose (made of twoglucoses). These disaccharides have the formula C12H22O11.
Hydrolysis can convert sucrose into asyrup of fructose and glucose, producing invert sugar. This resultingsyrup, sweeter than the original sucrose, has uses in making confectionsbecause it does not crystallize as easily and thus produces a smoother finishedproduct.If combined with fine ash, sugar will burn with a blue flame
The usualsugar cane constituents:
Constituents %of total weight
H20 69-75
Sucrose 8-16
Reducing sugars 0.5-2
Organic substance 0.5-1
Nitrogenous bodies 0.5-1
Ash 0.3-0.8
Fiber 10-16
MANUFACTURINGPROCESS:
Planting and Harvesting:
Sugar cane requires an averagetemperature of 75 degrees Fahrenheit and uniform rainfall of about 80 inchesper year. Therefore, it is grown in tropical or subtropical areas.
Sugar cane takes about seven monthsto mature in a tropical and about 12-22 months in sub tropical area. At this time,fields of sugarcane are tested for sucrose and mature fields are harvested. Theharvesting is done primarily by machine.
Then the harvested cane stalks areloaded mechanically into trucks or railroads, cars and taken to mills forprocessing into raw sugars
PROCESSING:
Traditionally, sugarcane has beenprocessed in two stages. Sugarcane mills, located in sugarcane-producingregions, extract sugar from freshly harvested sugarcane, resulting in raw sugarfor later refining, and in "mill white" sugar for local consumption.Sugar refineries, often located in heavy sugar-consuming regions. Then thepurify raw sugar to produce refined white sugar, a product that is more than 99percent pure sucrose. These two stages are slowly becoming blurred. Increasingaffluence in the sugar-producing tropics has led to an increase in demand forrefined sugar products in those areas, where a trend toward combined millingand refining has developed.
Sugarcane first has to be moved to amill which is usually located close to the area of cultivation. Small railnetworks are a common method of transporting the cane to a mill. Once thefactories acquire the cane it will be subjected to the quality test. In Sri Lanka canewill be evaluated according to the brix and trash percentage.
JUICE EXTRACTION
In a sugar mill, sugarcane is washed,chopped, and shredded by revolving knives. The shredded cane is repeatedlymixed with water and crushed between rollers; the collected juices (calledgarapa in Brazil)contain 10–15 percent sucrose, and the remaining fibrous solids, calledbagasse, are burned for fuel. Bagasse makes a sugar mill more than self-sufficientin energy; the surplus bagasse can be used for animal feed, in papermanufacture, or burned to generate electricity for the local power grid.
Juice constituents:
Water ----------> 75-85%
Sucrose ----------> 10-21%
Other sugars ----------> 0.3-3%
Organic substance ----------> 0.2-0.6%
Nitrogenous bodies ----------> 0.5-1%
EVAPORATION
The cane juice is next mixed withlime to adjust its pH to 7. This mixing arrests sucrose's decay into glucoseand fructose, and precipitates out some impurities. The mixture then sits,allowing the lime and other suspended solids to settle out, and the clarifiedjuice is concentrated in a multiple-effect evaporator to make a syrup about 60percent by weight in sucrose. This syrup is further concentrated under vacuumuntil it becomes supersaturated, and then seeded with crystalline sugar. Uponcooling, sugar crystallizes out of the syrup.
CENTRIFUGE
A centrifuge is used to separate thesugar from the remaining liquid, or molasses. Additional crystallizations maybe performed to extract more sugar from the molasses; the molasses remainingafter no more sugar can be extracted from it in a cost-effective fashion iscalled blackstrap.
Raw sugar has a yellow to browncolour. If a white product is desired, sulfur dioxide may be bubbled throughthe cane juice before evaporation; this chemical bleaches many color-formingimpurities into colorless ones. Sugar bleached white by this sulfitationprocess is called "mill white", "plantation white", and"crystal sugar".
REFINING
In sugar refining, raw sugar isfurther purified. It is first mixed with heavy syrup and then centrifugedclean. This process is called 'affination'; its purpose is to wash away theouter coating of the raw sugar crystals, which is less pure than the crystalinterior. The remaining sugar is then dissolved to make syrup, about 70 percentby weight solids.
The sugar solution is clarified bythe addition of phosphoric acid and calcium hydroxide, which combine toprecipitate calcium phosphate. The calcium phosphate particles entrap someimpurities and absorb others, and then float to the top of the tank, where theycan be skimmed off. An alternative to this "phosphatation" techniqueis 'carbonatation,' which is similar, but uses carbon dioxide and calciumhydroxide to produce a calcium carbonate precipitate.
After any remaining solids arefiltered out, the clarified syrup is decolorized by filtration through a bed ofactivated carbon; bone char was traditionally used in this role, but its use isno longer common. Some remaining colour-forming impurities adsorb to the carbonbed. The purified syrup is then concentrated to supersaturation and repeatedlycrystallized under vacuum, to produce white refined sugar.
As in a sugar mill, the sugar crystals areseparated from the molasses by centrifuging. Additional sugar is recovered byblending the remaining syrup with the washings from affination and againcrystallizing to produce brown sugar. When no more sugar can be economicallyrecovered, the final molasses still contains 20–30 percent sucrose and 15–25percent glucose and fructose.
To produce granulated sugar, in whichthe individual sugar grains do not clump together, sugar must be dried. Dryingis accomplished first by drying the sugar in a hot rotary dryer, and then byconditioning the sugar by blowing cool air through it for several days.
WASTE CHARACTESISTICS
The main air emissions from sugar processing and refiningresult primarily from the combustion of bagasse (the fiber residue of sugarcane), fuel oil, or coal. Other air emission sources include juice fermentationunits, evaporators, and sulfitation units.
Sugar manufacturing effluents typically have biochemicaloxygen demand (BOD) of 1,700–6,600 milligrams per liter (mg/l) in untreatedeffluent from cane processing and 4,000–7,000 mg/l from beet processing;chemical oxygen demand (COD) of 2,300–8,000 mg/l from cane processing and up to10,000 mg/l from beet processing; total suspended solids of up to 5,000 mg/l;and high ammonium content.
The wastewater maycontain pathogens from contaminated materials or production processes. A sugarmill often generates odor and dust, which need to be controlled. Most of thesolid wastes can be processed into other products and by-products. In somecases, pesticides may be present in the sugar cane rinse liquids.
INDUSTRY SECTOR GUIDELINES
• Reduce product losses to less than 10% by better productioncontrol. Perform sugar auditing.
• Minimize storage time for juice and other intermediateproducts to reduce product losses and discharge of product into the wastewater stream.
• Give preference to less polluting clarification processessuch as those using bentonite instead of sulfite for the manufacture of white sugar.
• Collect waste product for use in other industries—forexample, bagasse for use in paper mills and as fuel. Cogeneration systems forlarge sugar mills generate electricity for sale. Beet chips can be used asanimal feed.
• Optimize the use of water and cleaning chemicals. Procurecane washed in the field. Prefer the use of dry cleaning methods.
• Recirculate cooling waters. Continuous sampling andmeasurement of key production parameters allow production losses to beidentified and reduced, thus reducing the waste load. Fermentation processesand juice handling are the main sources of leakage. Odor problems can usuallybe prevented with good hygiene and storage practices.
TREATMENTTECHNOLOGY
· Pretreatmentof effluents consists of screening and aeration, normally followed bybiological treatment.
· Ifspace is available, land treatment or pond systems are potential treatmentmethods. Other possible biological treatment systems include activated sludgeand anaerobic systems. Which can achieve a reduction in the BOD level of over95%. Odor control by ventilation and sanitation may be required forfermentation and juice-processing areas.
· Biofiltersmay be used for controlling odor. Cyclones, scrubbers, and electrostaticprecipitators are used for dust control. annual operating hours.
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