Sugar

Sugar Industry

Today Sugar is so plentiful and so cheap that we take it granted and overlook how much science and industry accomplished in making refined sugar available to us. Primitive man had to depend on roots, fruits and saps from certain trees for any sweetness for his diet. The term sugar refers the chemical sucrose.

Sources of Sugar

  1. Sugar Cane: It was first cultivated in India from where it spread eastward to China, westward to Arabia, Egypt, Spain and finally to the new world. The sugarcane (saccharim officinaram) is a tall perennial grass having numerous bamboos like stems which grow to a height of 12 feet or more. The period of growth is normally 15-18 months, but because of the advent of the fertilizers the period shortened and a crushing season of 6 months every year is maintained for the production of sugar.
  2. Sugar Beet:  While we can guess regarding the original cultivation of sugarcane the situation is different with reference to sugar beet. The juice of the beet contains a sugar identical with that of the cane at this discovery was put into practical use.

Steps in sugar manufacture

The sugar is synthesized by the growing plant and the processing in the factory is only a succession of separations whereby the sugar is separated from the constituents of the plant.

  1. Separation of the juice from the fiber by pressure
  2. Clarification is a removal of impurities that interfere with subsequent evaporation and crystallization
  3. Removal of water by evaporation
  4. Conversion of the sugar from the dissolved condition to a solid crystal form
  5. Separation of the crystal sugar from the mother liquor followed by molasses obtained from centrifuge.
  6. Drying and packing of sugar

Clarification

The juice extract from the cane are strained to remove dirt particles, fiber or pulp after this juice is ready for clarification. The purpose of clarification is to free the juice as far as possible from all constituents except sugar without altering the sugar itself. Lime is one for the first chemical to be used are universal basis for this clarification since it is both effective and economical for the cost. The main purpose of lime is to neutralize the acidity of juice and converts many of the organic acids into insoluble calcium salt. Thus clarification remains an essential and integral part of the manufacture of sugar.

The flow process of liming is given below;


 

Analysis of typical cane molasses

 

Composition

Percentage (%)

Water

20

Sucrose

30

Raffinase

0

Invert Sugar

32

Ash

6

Organic non-sugars

12

Evaporation

The juices from the clarification must now be evaporated in order to produce crystal sugar. Today evaporation is conducted by steam-in evaporators. In the first stage of evaporation the juice is concentrated to 50%-60% sugar. This is made in MEE (Multiple Effect Evaporator) which are very effective and by efficient use of steam.

Crystallization

At this stage the evaporation is continued to the point where sugar crystals formed and separate from remaining water and impurities. There are various types of crystallizers namely horizontal, cylindrical or U shaped kerns equipped with stirring paddles. After stirring the mixture are cooled to take advantage of the lower solubility of sugar at lowest temperature.

Refining

The raw cane sugar is subjected to further refining operation before it is ready for consumption. Adsorption of impurities is followed by crystallization. The refining process takes place in the following sequence.

  1. Affination
  2. Melting
  3. Defecation
  4. Purification with Bone-char or active carbon
  5. Filtration
  6. Crystallization
  7. Centrifuging
  8. Finishing

In affination process the raw sugar is mixed with syrup which softens and dissolves the molasses without eroding the sugar crystals. In the defecation process sufficient lime is added to make the solution alkaline and the alkalinity is neutralized with calcium phosphate or phosphoric acid. The precipitate of calcium phosphate or phosphoric adsorbs most of impurities.


Bone-char Treatment

Composition

Percentage (%)

Carbon

10

Tri calcium phosphate

83

Calcium carbonate

4

Iron, Nitrogen, Silica, Calcium Sulfide

Traces

The purpose this treatment is primarily to remove color, organic and inorganic substances from the raw sugar solution. Active carbon is used for refining of sugar. It is generally employed from producing a refined, granulated sugar.

 

By-products

Molasses:     This is basically used for cattle feed. Although it has the limitation of providing only carbohydrate high protein yeast can be made from molasses and inorganic nitrogen salts, can serve as a basis for the protein content in the cattle feed. The recent development is industrial alcohol produced from molasses can be used as motor fuel. Such a development can simplify the world production of molasses.

Bagasse:       The quantity is 28,000,000 Tonnes of Bagasse per year. It is right now used in sugar factories as fuel developing co-generation plant for producing power, manufacture of plastics, paper pulp and wall boards.

Conversion of sugar to other products

Sugar represents practically a chemically pure product available at low cost and it is natural to find that serious study has given rights to development of processes to convert sugar into other products. The various conversions for molasses can be applied for sugar but extensive development can takes place parallel to the potential molasses, bagasse and press-mud whose original name is “Filter Cake”. Some undertakings compile the manufacture of sugar with the production of ethyl alcohol, butyl alcohol, acetone by fermentation.

Press-mud (Filter cake):    Press-mud or Filter cake is the solid substance obtained after juice clarification. It is almost brown color and it was used as manure for the sugar cane field itself. A sugar factory crushing 2500 TPD of sugarcane generates 75 Tonnes of Filter cake. There are about 500 sugar mills generating sugar in India with crushing capacity ranging from 2500 - 5000 TPD. The recent research on the exploitation of press-mud or filter cake shows the presence of sugar, proteins, fiber, wax and other mineral salts. Sugar is present a 0.5% in press-mud. The Protein content is 3%. The Fiber is 35%. The Wax is 12%. And the remaining is moisture or water. These components can be extracted and used for the increased use of sugar industry. The fiber part of the waste is dried and converted to carbon called as “Adsorbent Carbon” as they can substitute the role of active carbon in the adsorption operations. Though in the potential of press-mud it is estimated that we can have 750 crores of rupees provided to national exchequer annually. These constituents are downstream of multi component sugar industry by-product. They can be applied for fluoride removal to eliminate skeletal flurosis and in the Drugs & Pharma Industry for the production of anti cancer drugs, already in commercial operation in a country like Japan.

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