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Synopsis… • Introduction of sugar • Introduction • Some general knowledge • Production sources of sugar • Manufacture of sugar from sugar cane • Introduction • Steps involving process • Block diagram view of the process • Flow sheet (on transparency)
Introduction… • Sugar is basically defined as a class of molecules containing CARBON, HYDROGEN and OXYGEN which are called Carbohydrates. • They are an essential structural component of living cells and the source of energy for all animals, including humans. • Due to its world wide significance, its production in large scale is very important.
Continue… • Production of sugar is mostly done from two sources. • In this we will discuss about the manufacture process from sugar cane. Sugar cane Beet
Continue… • The sugar we take in our diet (table sugar) is in the form of sucrose, which is digestible by human body because of the enzyme catalytic reaction in our body that breaks the sucrose molecule to glucose and fructose. From which - isomer of glucose is digested and utilized by our body and the rest fructose and glucose are excreted out. • Our body cannot directly utilize glucose and fructose.
Structural formula of Sugar C12H22O11
Introduction… • Sugar cane is a member of grass family. It has bamboo like stalk. It contain about 11 to 15% of sucrose by weight. • The cutting of cane stalk is done either manually (by hands) or my means of mechanical cutters. • There can be no delay in transporting the freshly cut cane to the factory, because failure to process it within 24 hours after cutting causes loss by, “inversion to glucose and fructose.” • Reference: Shreve’s CPI 5th edition, pg: 556
Process… • The process involves the following steps; • Washing • Crushing / Chopping • Milling / Grinding • Filtration • Clarifying • Evaporation • Crystallization • Centrifugal separation • Storage
Block diagram Filtration Clarification Milling Evaporation Crystallization Crushing Centrifugal separation Storage Washing
Washing… • Washing is done to remove mud or debris. Water is used for this purpose. • The cane stalk before entering the crushers is showered with water and sometimes brushes are also used.
Crushing… • Blades are used for crushing the cane into small pieces. • The output pieces are of 3 different shapes; • In the chopper, the thick scalp of cane is removed first and then it is cut into small pieces. Length wise cut small length pieces Circular small length pieces (rod like) Inclined cut small pieces
Milling… • Milling is a process in which juice is extracted from the pieces of cane. • 3-4 mills are arranged in series to extract a maximum amount of juice from cane. • To get maximum amount of juice to be extracted, the product after passing through the mill is recycled also. • Each mill consists of a 3 grooved rollers that exert high pressure. The distance between the rollers is quite lowand is decreased progressively.
Continue… • The juice is screened and then treated with lime. Lime acts as a coagulating agent and coagulates the colloidal particles in the juice. It also changes the pH of the juice to 7.5-7.8. The juice in nature is slight acidic (pH ranges, 5.9-6.5). For its neutralization it is treated with phosphoric acid in the clarifiiers.
Clarification… • Phosphoric acid is added to clarify the juice. Transparency is increased and turbidity is decreased. • The juice before sent to clarifiers are heated that increase the solubility of impurities (phosphates and nitrates) in lime which are precipitated.
Filtration… • The flocks formed and the solid impurities are filtered and are removed from the juice. The clear juice is then sent to the evaporators.
Evaporation… • High pressure steam evaporators are used that remove the water vapors from the juice. 3-4 evaporators are arranged in series. Each successive evaporator uses the steam of the previous evaporator. • 70-75% vapors are evaporated from the juice in evaporators. • After passing through these, the messicuite(mixture of crystals and molasses) is further heated in vacuum pans where the remaining vapors are vaporized.
Continue… • Maximum amount of vapors are to be removed from the juice because the water contents are not desired either in our product as well as by-product. • Molasses (a thick viscous syrup) is our by-product. It is separated from the sugar crystals and is used as food preservation and its high grade is used in alcoholic drinks. • The first grade molasses is obtained by first evaporation in VACUUM PAN. It is called sugar pulp.
Continue… • Normally this molasses is used for food preservation and for sweetening of food. • It contain some amount of sugar. • To achieve High grade molasses, first grade molasses is sent to 2nd vacuum pan for further heating and resent to crystallizer which extract more sugar from the molasses. This high grade molasses is called BLACK STRAP.
Crystallization… • The crystallizer is a horizontal agitated tank equipped with cooling coils. Here additional sucrose deposits on the crystals already formed and crystallization is completed. Chilled water is used as a cooling media in coils.
Centrifugal separation • Centrifuges are used that separate the molasses from the crystals. The molasses is sent to storage and the crystals are sent for refining.
