Sugar industry is the second bigger Industry of the country, the first being the Textille industry. Cane sugar is used all over the world as a sweetening agent. Cane sugar occurs in sugar cane, beat, maple, sweet sorghum and some spices of plam. Many fruits such as pineapple, ripe, banana, Apricot etc. also contain sugar as sucrose. Sugar supplies man about 13% the energy required for existence. So, in this article we will discuss about the sugar manufacturing process step by step, Raw sugar manufacturing process etc.
 |
| Sugar industry |
Industrially, sugar is mainly obtained from sugarcane and beat. In India most of the sugar is produced from sugarcane. India has been the chief sugar producing country in the world; and is an exporter of sugar.
The word 'sugar' used in everyday life refers to the chemical sucrose. Sucrose therefore occurs in sugarcane and sugar beat. It concentration in lower part of sugarcane is greater than in the upper parts. In India, sucrose is obtained from sugar cane only. Sugar cane contains 70-75% water, 10-15% crystalline sugar, 0.5% -1. 0% reducing sugar, 10-18% fibre, 1% ash and organic acids.
Importance of Sugar Industry:
1) Cane sugar is used all over the world as a sweetening agent.
2) Sugar supplies man with about 13% of the energy for existance.
3) About half of the world production of sugar is from sugarcane.
4) The molasses obtained in sugar industry is also used for manufactur of alcohol by fermentation process.
5) The byproduct bagasse is utilized as a raw material for the pulp, paper, celotex, paper board and wall board industries.
Sugar Manufacturing process step by step from Sugar cane:
The main source of cane sugar (sucrose) is the Sugarcane. During 19th Century sucrose became the commercial commodity for the world. Today the quality of sugar has been improved to a great extent as a result of better techniques employed throughout the world.
1) Raw material:
The raw material used in the manufacture of sugar is sugarcane. It is a large perential tropical grass belonging to the geneus saccharum. It has bamboo like stalk grows to a height 8 to 15 feets and contain 11 to 15% sucrose by weight. The cane stalk is round and covered with a hard rind which is light brown, green, yellowish green or purple in colour, depending upon the variety.The stalk consists of a series of joints or internodes separated by nodes. The rind and nodes are woody in nature while internode is soft pith. The internode consists the greater part of the juice containing sucrose. The nodes contain 'eyes'or buds which 'sprout' when planted.
Harvesting:
The well developed sugar canes are cut at ground level and at the same time leaves and top of the stalk are removed. The harvested sugarcanes are transported to the sugar Mill by the use of trucks, transporting the sugarcane to the factory, otherwise there will be loss in weight as well as inversion to glucose and fructose that passes into molasses.
Extraction of Juice:
a) Harvested sugarcane must be washed with water before milling to eliminate soil, rocks and field trash. Washing system consisting of conveyor with water jets, baths for removal of stones and stripping rolls.
b) The washed sugarcane is first prepared for grinding by one or more of the following operations-
1) Chopping the sugarcane into smaller pieces with one or two sets of rotating knives (400-600rpm) or crushed into smaller pieces.
2) Pressing: The crushed sugarcane then passes through a series of three horizontal rollers (1st mill) arranged in a triangular pattern. The top roller rotates counter clockwise while the bottom two rollers rotate clockwise.
3) The pressure on the top roller is regulated by hydraulic rams about 500 tones per sq. inch.
4) The crusher and first mill are provided with vibrating screens and arrangement for transferring the extracted juice to the raw juice tank.
5) Below each mill, there is a juice pan into which expressed juice flows.
6) The crusher and first mill extract 60-70% of the cane juice and the remaining mills take out 22-24% cane juice from bagasse.
7) The bagasse still containing some juice pass successively through the 2nd, 3rd, and 4th mills and then to the storage or to the kiln in which it is used as a fuel to run the mill.
8) In this way bagasse is removed by crushing and milling process.
C) Compound Imbibition process:
It is a process to reduce the sucrose in the bagasse by repeated dilution. In the 5th mill tandem, water is added to the 4th mill and the expressed juice from that mill is brought back to the second mill. In this way the juice in the bagasse is always diluted before crushing. Thus, nearly 95-99% juice is extracted from spent cane (bagasse).
The bagasse which contains unextracted sugar (1%), the woody fibre and 40-50% water. This usually goes to the boilers as fuel. Many factories purchase this bagasse for making wall board, paper manufacture, insulating material, hard board, cattle bedding etc.
The cane juice from milling station is pumped into a weighing tank (8-10 tons). After weighing the juice is sent for purification process, which involves number of stops.
The bagasse which contains unextracted sugar (1%), the woody fibre and 40-50% water. This usually goes to the boilers as fuel. Many factories purchase this bagasse for making wall board, paper manufacture, insulating material, hard board, cattle bedding etc.
Purification of Juice:
The cane juice from milling station is pumped into a weighing tank (8-10 tons). After weighing the juice is sent for purification process, which involves number of stops.
Clarification process:
The weighed juice is screened to remove floating impurities. The screened juice is acidic, brownish green opaque liquid, containing soluble impurities like soil, protein, fats, waxes, gum, colouring matter and mineral salts.
1) The screened juice is then transferred into defection tanks, which are circular tanks with conical bottoms and filtered with steam and air connections.
2) The juice is then neutralised by adding adequate amount of milk of lime till the pH of the juice reaches 7 to 7.3.
3) The limed juice is then passed through a tubular heater, where it is heated to boiling (90-115°C).
4) During this process insoluble lime salts, coagulated protein and continuous closed tray clarifiers.
5) The precipitate is removed by sedimentation or settling in continuous closed tray clarifiers.
6) The thick scrum layer and mud are removed Mechanically by passing through a filter press.
7) During filtering in filter press, the cakes are washed with water and dried. The wash water is send to the clarifier.
8) Filter cakes containing phosphorus and little sucrose are used as manure.
9) The juice leaving the clarifier is a clean brownish liquid and contains calcium sucrosate and calcium hydroxide.
By lime defection process all impurities are removed completely. Hence by crystallising the concentrated juice a coloured crystalline sugar called raw sugar is produced instead of white crystalline sugar.
In India, clarification of juice or conversion of raw sugar into white crystalline sugar is done either by sulphitation or Carbonation process.
A) Clarification by lime defecation process:
1) The screened juice is then transferred into defection tanks, which are circular tanks with conical bottoms and filtered with steam and air connections.
2) The juice is then neutralised by adding adequate amount of milk of lime till the pH of the juice reaches 7 to 7.3.
3) The limed juice is then passed through a tubular heater, where it is heated to boiling (90-115°C).
4) During this process insoluble lime salts, coagulated protein and continuous closed tray clarifiers.
5) The precipitate is removed by sedimentation or settling in continuous closed tray clarifiers.
6) The thick scrum layer and mud are removed Mechanically by passing through a filter press.
7) During filtering in filter press, the cakes are washed with water and dried. The wash water is send to the clarifier.
8) Filter cakes containing phosphorus and little sucrose are used as manure.
9) The juice leaving the clarifier is a clean brownish liquid and contains calcium sucrosate and calcium hydroxide.
By lime defection process all impurities are removed completely. Hence by crystallising the concentrated juice a coloured crystalline sugar called raw sugar is produced instead of white crystalline sugar.
In India, clarification of juice or conversion of raw sugar into white crystalline sugar is done either by sulphitation or Carbonation process.
Concentration of cane juice:
 |
| Concentration of cane juice |
The clarified juice obtained from sulphitation or carbonation process is concentrated into thick syrup, so as to prepare the juice for crystallization. The juice is pumped in multieffect vaccum Evaporator, where it is concentrated under reduced pressure to a clear heavy syrup containing about 65% solids.
The temperature of first evaporator is highest than others while the pressure at the first evaporator is lowest, in order to achieve maximum steam economy. This arrangement allows the juice to be drawn from one vessel to the next and permits the juice to boil at low temperature.
Crystallization of Sucrose:
 |
| Crystallization of sucrose |
The thick syrupy liquid is further concentrated by removing water by heating in a single moving horizontal agitators and cooling coils through which cold water is circulated. The crystallization of sucrose in vacuum fans is called 'sugar boiling' and each boiling is termed as massecuite. The concentration syrup is then led to crystallising tanks and cooled slowly, when crystals of sugar (sucrose) separate out.
To obtain a maximum yield of sugar in operation the crystallization is usually carried out by introducing extremely the sugar crystals in the syrup to induce crystallization and to save fuel. The crystallization by this method also saves the time for boiling and also disposes of low grade sugar.
There are four stages in the process of crystallization:
1) Seeding and graining,
2) Establishing the seeds,
3) Growth of crystals, and
4) Concentration.
Centrifugation:
Sugar crystals are recovered from the mother liquor by whirling in centrifuged machine, which is composed of a perforated basket. These machines are usually driven by water under pressure.
As a result of high revolving motion, the crystals are easily separated and liquid portion drains out. Last traces f molasses still sticking with the crystals and whirling again in the centrifugal machine. The final mother liquor is molasses which is a by-product of sugar industry.
Drying:
The sugar crystals are then elevated to the coolers. Here it comes in contact with hot air or super heated steam and crystals are partially dried. It is then charged to a counter current rotary cylindrical drier.
Packaging:
The dried sugar crystals are screened in different grades and finally bagged.
So, this is all about the sugar manufacturing process step by step.
