Sugar Industry

Humans desire sweetness in their diet and nature provides it from several sources . The average person in Unitesd States consumes 32 kg of suugar per year. The world average is one-third of this but is increasing. Sugar is not prized for its taste alone, for its supplies about 13 percent of the energy required for existance. As a result sugar production and refining is huge industtry.

Manufacture of Sugar

The major processing methods used for refining cane sugaar today have been worked out for many years and are unlikely to change drastically soon. Alterations to conserve energy and perhaps reduce the use of some reagents are to be expected, but major process changes seem unlikely.

Cane: 

Sugar cane is a member of the grass family. It has a bamboo like stalk, grows to height from 3 to 5 m, and contains 11 to 15 % sucrose by weight. The cane is usually planted with cuttings from the mature stalks , which sprout and produce a number of new stalks . The approximate period of growth of the cane in Cuba is 12 to 15 months and nearly twice in Hawaii and Peru.

The production of raw cane sugar may be divided into the following unit operations and chemical conversions

The cane is first washed to remove mud and debris

The cane is chopped and shredded by crushers in preparation for removing the juice. 

 The juice is extracted by passing the crushed cane through a series of mills, each of which consists of three grooved rolls that exerts heavy pressure . Water and weak juices may be added to help macerate the cane and aid in the extraction form the cane. The spent cane (bagasse) is either burned for fuel or used to manufacture paper , hardboard, or insulating material.

      The juice is screened to remove floating impurities and treated with lime to coagulate part of the collidal material, precipitate some pf the impurities and change the pH. Phosphoric acid may be added because jucise that do not contain a small amount of phosphate s do not clarify well. Lime in slight excess over the theoritically required to precipitate all the phosphate is then added.

Cane-sugar Refining:

Raw sugar is delivered to the refineries in bulk. The first step in refining is called affination, wherein the raw-sugar crystals are treated with a heavy syrup in order to remove the the film of adhering molasses.This strong syrup dissolves little or none of the sugar but does soften or dissolve the coating of impurities. This operation is performed in manglers, which are heavy scroll conveyors fitted with strong mixing flights.The resulting syrup is resulting syrup is removed by centrifuge and the sugar cake is sprayed with water. The crystals are dumped into the melter. The melted and washed is then treated by a process called as clarification or defection. Either mechanical or chemical process can be used. The clarified liquor is filtered and sent for decolorization.
The carbonation system adds carbon dioxide from scrubbed flue gas to the melted sugar , which precipitates calcium carbonate. The precipitate carriers down with it over 60 percent of the coloring matter present and is removed by filtration.

 Decolorization-Char Filtration

The clarified effluent liquor still retains a dissolved impurities. These impurities are removed by percolation through bone char ( activated carbon is also used ) The percolation is carried out aat about 82 degree Celsius, and the initial product is clear , water-white syrup.

Bagasse

The burning of about 70 percent of the bagasse produced furnishes enough steam for power heat to run the mill.
The bagasse is conveyed by an endless belt to rotary digesters, which are 4.3 m in diameter, and is cooked under pressure in order to render the fibers pliable, loosen the encrusting the material, dissolve organic material and sterilize the fiber. The resulting pulp , is pumped to swim- hammer shredders and washed specifically designed rotary washers in order to remove dirt.